SYSTEMES DE CHAUFFAGE A MICRO-ONDES AMELIORES ET LEURS PROCEDES D'UTILISATION

ENHANCED MICROWAVE HEATING SYSTEMS AND METHODS OF USING THE SAME

Abrégé français

Des systèmes de chauffage par micro-ondes améliorés pour le chauffage de plusieurs articles et des méthodes dutilisation sont décrits. Selon un mode de réalisation, le système de chauffage par micro-ondes peut comprendre une chambre de chauffage sous pression ou remplie de liquide, configurée pour chauffer les articles passant à lintérieur le long dune ou plusieurs lignes de convoyage, au moyen de lénergie micro-onde déchargée par un ou plusieurs émetteurs de micro-ondes. Les systèmes de chauffage par micro-ondes et les procédés selon les modes de réalisation de la présente invention peuvent être applicables à un système de chauffage de taille commerciale et peuvent être utilisés pour la pasteurisation et/ou la stérilisation de produits alimentaires, de fluides médicaux et de dispositifs médicaux.

Abrégé anglais

Enhanced microwave heating systems for heating a plurality of articles and methods of using the same are provided. In one embodiment, the microwave heating system may include a pressurized or liquid-filled heating chamber configured to heat the articles passing therethrough along one or more convey lines using microwave energy discharged by one or more microwave launchers. Microwave heating systems and processes according to embodiments of the present invention may be applicable to a commercial-sized heating system and can be employed for the pasteurization and/or sterilization of foodstuffs, medical fluids, and medical devices

Revendications

We claim;
1. A microwave system for heating a plurality of articles, said microwave
system
comprising:
a microwave generator for generating microwave energy having a predominant
wavelength, A.;
a conveyance system for conveying said articles along a convey axis; and
a first microwave launcher for launching at least a portion of said microwave
energy toward said articles conveyed by said conveyance system,
wherein said first microwave launcher defines at least one launch opening
having
a width, W: , and a depth, Di,
wherein W1 is greater than Di and Di is not more than. 0.50 7L.
2. The system of claim 1, wherein said first microwave launcher comprises a
set
of broader opposing side walls and a set of narrower opposing end walls,
wherein each of
said side walls and said end walls presents a terminal edge, wherein the
terminal edges
of said side walls and said end walls cooperatively define said launch
opening, wherein
said width, Wi , of said launch opening is defined hy the distance between the
terminal
edges of said end walls and said depth. Di, of said launch opening is defined
by the
distance between the terminal edges of said side walls.
3. The system of claim 2, wherein the terminal edges of said side walls extend
substantially parallel to said convey axis.
4. The system of claim 3, wherein said side walls have a width flare angle,
Ow, of
at least 5 .
5. The system of claim 4, wherein said end walls have a depth flare angle, ed,
of
not more than O.
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6. The system of claim 5, wherein Od is less than 00.
7. The system of claim 1, wherein said launch opening is rectangular.
8. The system of claim 1, wherein said first microwave launcher defines a
microwave inlet and at least a first and a second launch opening, wherein said
first launch
opening has said width. Wi, and said depth, Di, wherein said second launch
opening has
a width, W2, and a depth, D2, wherein W2 is greater than D2, wherein D2 is not
more than
0.625 A,.
9. The system of claim 8, wherein said microwave launcher comprises at least
one dividing septum disposed within the interior region said microwave
launcher
between said microwave inlet and said launch openings, wherein said septum at
least
partially defines said first and said second launch openings.
10. The system of claim 9, wherein first and said second launch openings are
adjacent to one another and are aligned transverse to said convey axis,
11. The
system of claim l 0, wherein said microwave inlet has a depth, Do,
wherein Di and 02 are less than or equal to Do,
12. The system of claim 11, wherein said first microwave launcher further
comprises a third launch opening having a width, W3, and a depth, D3, wherein
W3 is
greater than 03, wherein none of Di, D2, or D3 is more than 0.50 A.
13. The system of claim 12, wherein said first microwave launcher further
comprises at least two dividing septa disposed between said microwave inlet
and said
launch openings, said septa collectively defining at least three separate
microwave
pathways for propagating microwave energy from said microwave inlet to each of
said
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first, second, and third launch openings, wherein at least one of said
separate microwave
pathways is longer than at least one other of said separate microwave
pathways.
14. The system of any one of claims 1 to 13, further comprising a microwave
chamber through which said articles are conveyed by said conveyance system,
wherein
said articles comprise packaged foodstuffs, wherein said microwave chamber is
configured to be liquid-filled and pressurized to at least 10 psis, wherein
said microwave
system is configured to pasteurize and/or sterilize said packaged foodstuffs
at a rate of at
least 20 packages per minute per convey line.
15. A microwave system for heating articles, said microwave system comprising:
a microwave generator for generating microwave energy having a predominant
wavel ength, X;
a microwave heating ehamber for receiving a phrality of said articles, wherein
said microwave heating chamber is configured to be filled with a liquid
medium;
a conveyance system for conveying said articles through said liquid medium
along a convey axis; and
a. first microwave launcher for launching at least a portion of said microwave
energy toward said articles conveyed by said conveyance system,
wherein said first microwave launcher includes a microwave inlet and first and
second spaeed apart launch openings,
wherein said microwave launcher includes at least one dividing septum disposed
between said microwave inlet and said first and said second launch openings,
wherein said dividing septum at least partially defines said first and said
second
launch openings,
wherein said first launch opening has a width, We and a dcpth, De and said
second launch opening has a width, W2, and a depth, Dz,
wherein WI is greater than Di and W2 is greater than D2
wherein Di and D2 are each not more than 0.50 X,

wherein said first microwave launcher comprises a set of broader opposing side
= walls and a set of narrower opposing end walls,
wherein each, of said side walls and said end walls presents a terminal edge,
wherein the terminal edges of said side walls extend substantially parallel to
said
convey axis,
wherein said articles comprise packages.containing foodstuffs, medical fluids,
or
medical instruments, and said microwave heating system is configured to
pasteurize or
sterilize said articles.
16. The system of claim 15, wherein said end walls have a depth flare angle,
ed,
of not more than 00.
17. The system of claim 15, wherein said end walls have a depth flare angle,
Od,
of less than 00.
18. The system of claim 15, wherein first and said second launch openings are
adjacent to one another and are aligned transverse to said convey axis.
19. The system of claim 15, wherein said microwave inlet has a depth, D.,
wherein Di and D2 are less than or equal to D..
20. The system of claim 15, wherein said first microwave launcher further
comprises a third launch opening having a width, W3, and a depth, D3, wherein
W3 is
greater than D3, wherein none of DI, D2, or D3 is more than 0.50 X.
21. The system of claim 20, wherein said first microwave launcher further
comprises at least two dividing septa disposed between said microwave inlet
and said
first, second, and third launch openings, wherein said septa collectively
define at least
three separate microwave pathways for propagating microwave energy from said
microwave inlet to each of said first, second, and third launch openings,
wherein at least
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one of said separate microwave pathways is longer than at least one other of
said separate
microwave pathways.
22. The system of claim 15, wherein the center points of said first and said
second
launch openings arc laterally spaced from one another relative to said convey
axis,
23. The system of claim 15, wherein said fffst and second launch openings are
rectangular and are elongated in the direction of extension of said convey
axis,
24, The system of claim 15, wherein said first mierowave launcher further
comprises a pair of inductive iris panels disposed between said inlet and said
launch
openings, wherein said inductive iris panels define an inductive iris
thercbctween.
25. The system of claim 15, Rather comprising a microwave-transparent window
at least partially covering said launch openings.
26. The system of any one of claims 15 to 25, wherein said first microwave
launcher is configured to propagate microwave energy along a first central
launch axis
and wherein a first launch tilt angle of 00 to 15* is defined between said
first central
launch axis and a plane normal to said convey axis,
27. The system of any one of claims 15 to 25, wherein said microwave chamber
is
configured to be pressurized to at least 10 psig.
28. The system of any one of claims 15 to 25, wherein said microwave system is
configured to pasteurize and/or sterilize said articles at a rate of at least
20 articles per
minute.
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29. The system of any one of claims 15 to 25, wherein said first microwave
launcher is art upper microwave launcher positioned above said conveyance
system arid
configured to direct microwave energy downwardly toward said conveyance
system.
30. The system of any one of claims 15 to 25, further comprising a second
microwave launcher, wherein said second microwave launcher is positioned below
said
conveyance system and is configured to direct microwave energy upwardly toward
said
conveyance system.
31. The system of any one of claims 15 to 25, further comprising a plurality
of
individual carriers for securing said articles when said article are passed
through said
microwave heating chamber, wherein said conveyance system is configured to
move said
carriers through said microwave heating chamber.
32. The system of any one of claims 15 to 25, further comprising a
tberrnalization
zone located upstream of said microwave heating chamber for thermalizing said
articles,
wherein said thermalization zone comprises a thermalization chamber and a
plurality of
fluid jet locations for discharging pressurized jets of liquid toward said
articles in said
thermalization chamber, and a quench chamber located downstream of said
microwave
heating chamber for cooling said articles, wherein said thermalization zone is
configured
to adjust the temperature of said articles so that at least 85 percent of said
articles have a
temperature within 5 C of each other prior to the introduction of said
articles into said
microwave heating chamber, wherein said quench zone is configured to cool the
heated
articles by at least 30 C, and wherein said microwave heating chamber is
configured to
heat said articles by at least about 25"C in a time period in the range of
from about 60
seconds to about 10 minutes, wherein said articles comprise packages and said
system is
configured to pasteurize or sterilize said articles at rate of at least 15
packages per minute.
93

Description

Enhanced Microwave Heating Systems and Methods of Using the Same
Related Application
[001] This application is filed as a divisional application resulting
applicant's
Canadian Patent Application Serial No. 2867301, filed 13 March 2013, and which
has
been submitted as the Canadian national phase application corresponding to
International
Patent Application No. PCT/US2013/030844, filed 13 March 2013.
Field of the Invention
[001a] This invention relates to microwave systems for heating one or more
objects, articles, and/or loads.
Background
Electromagnetic radiation, such as microwave radiation, is a known mechanism
for delivering energy to an object. The ability of electromagnetic radiation
to penetrate
and heat an object in a rapid and effective manner has proven advantageous in
many
chemical and industrial processes. Because of its ability to quickly and
thoroughly heat
an article, microwave energy has been employed in heating processes wherein
the rapid
achievement of a prescribed minimum temperature is desired, such as, for
example,
pasteurization and/or sterilization processes. Further, because microwave
energy is
generally non-invasive, microwave heating may be particularly useful for
heating
'sensitive' dielectric materials, such as food and pharmaceuticals. However,
to date, the
complexities and nuances of safely and effectively applying microwave energy,
especially on a commercial scale, have severely limited its application in
several types of
industrial processes.
[002] Thus, a need exists for an efficient, consistent, and cost effective
industrial-
scale microwave heating system suitable for use in a wide variety of processes
and
applications.
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Summary
[003] One embodiment of the present invention concerns a microwave system for
heating a plurality of articles. The system comprises a microwave chamber
configured to
receive the articles and a conveyance system for transporting the articles
through the
microwave chamber along a convey axis. The system also comprises a first
microwave
launcher configured to propagate microwave energy into the microwave chamber
along a
first central launch axis, wherein a first launch tilt angle of at least 2 is
defined between
the first central launch axis and a plane normal to the convey axis.
[004] Another embodiment of the present invention concerns a microwave system
for heating a plurality of articles. The system comprises a microwave chamber
configured
to receive the articles and a conveyance system for transporting the articles
through the
microwave chamber along a convey axis. The system also comprises a first
microwave
launcher defining at least one launch opening for discharging microwave energy
into the
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microwave chamber; and a substantially microwave-transparent window disposed
between the
microwave chamber and the launch opening. The window presents a chamber-side
surface
defining a portion of the microwave chamber and at least 50 percent of the
total surface area of
the chamber-side surface of the window is oriented at an angle of at least 2
from the horizontal.
[005] Yet another embodiment of the present invention concerns a process for
heating a
plurality of articles in a microwave heating system, the process comprising
the steps: (a)
passing a plurality of articles through a microwave heating chamber via a
conveyance system,
wherein the microwave heating chamber is at least partially filled with a
liquid medium; (b)
generating microwave energy using one or more microwave generators; (c)
introducing at least
a portion of the microwave energy into the microwave chamber via at least one
microwave
launcher, wherein at least a portion of the microwave energy introduced into
the microwave
chamber is discharged at a launch tilt angle of at least 2'; and (d) heating
the articles in the
microwave heating chamber using at least a portion of the microwave energy
discharged
therein.
[006] One embodiment of the present invention concerns a microwave system for
heating a plurality of articles. The system comprises a microwave generator
for generating
microwave energy having a predominant wavelength (A), a conveyance system for
conveying
the articles along a convey axis, and a first microwave launcher for launching
at least a portion
of the microwave energy toward the articles conveyed by the conveyance system.
The first
microwave launcher defines at least one launch opening having a width (W1) and
a depth (Di),
wherein Wi is greater than Di, wherein Di is not more than 0.625 A.
[007] Another embodiment of the present invention concerns a microwave system
for
heating a plurality of articles. The system comprises a microwave generator
for generating
microwave energy having a predominant wavelength (A), a microwave chamber
configured to
receive the articles, and a microwave distribution system for directing at
least a portion of the
microwave energy from the microwave generator to the microwave chamber. The
microwave
distribution system comprises a first microwave launcher. The first microwave
launcher defines
a microwave inlet for receiving at least a portion of the microwave energy and
at least one
launch opening for discharging the microwave energy into the microwave
chamber. The
microwave inlet has a depth (do) and the launch opening has a depth (di). The
do is greater
than di.
[008] Yet another embodiment of the present invention concerns a microwave
system
for heating a plurality of articles. The system comprises a microwave chamber
configured to
receive the articles, a conveyance system for transporting the articles
through the microwave
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chamber along a convey axis, and a first microwave launcher defining a
microwave inlet and
two or more launch openings configured to discharge microwave energy into the
microwave
chamber. The center points of adjacent launch openings are laterally spaced
from one another
relative to the convey axis.
[009] One embodiment of the present invention concerns a microwave launcher
comprising a microwave inlet for receiving microwave energy having a
wavelength (A), at least
one launch opening for discharging at least a portion of the microwave energy,
and a pair of
opposing launcher end walls and a pair of opposing launcher sidewalls defining
a microwave
pathway therebetween. The microwave pathway is configured to permit the
passage of
microwave energy from the microwave inlet to the launch opening. The launcher
also includes
a pair of inductive iris panels respectively coupled to and extending inwardly
from the pair of end
walls. Each of the inductive iris panels extends partially into the microwave
pathway to define
therebetween an inductive iris through which at least a portion of the
microwave energy routed
from the microwave inlet to the launch opening can pass.
[010] Another embodiment of the present invention concerns a microwave system
for
heating a plurality of articles. The system comprises a microwave generator
for generating
microwave energy having a wavelength (A), a microwave chamber configured to
receive the
articles, a conveyance system for conveying the articles through the microwave
chamber along
a convey axis, and a microwave distribution system for directing at least a
portion of the
microwave energy from the microwave generator to the microwave chamber. The
microwave
distribution system comprises a first microwave splitter for dividing at least
a portion of the
microwave energy into two or more separate portions and at least one pair of
microwave
launchers each defining a microwave inlet and at least one launch opening for
discharging
microwave energy into the microwave chamber. The microwave distribution system
further
comprises a first inductive iris disposed between the first microwave splitter
and the launch
opening of one of the microwave launchers.
[011] Yet another embodiment of the present invention concerns a process for
heating a
plurality of articles in a microwave heating system, the process comprising
the steps: (a)
passing a plurality of articles through a microwave heating chamber along one
or more convey
lines of a conveyance system; (b) generating microwave energy using one or
more microwave
generators; (c) dividing at least a portion of the microwave energy into two
or more separate
portions; (d) discharging the portions of microwave energy into the microwave
heating chamber
via two or more microwave launchers; (e) subsequent to the dividing of step
(c) and prior to the
discharging of step (d), passing at least one of the portions of microwave
energy through a first
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inductive iris; and (f) heating the articles in the microwave heating chamber
using at least a
portion of the microwave energy discharged therein.
[012] One embodiment of the present invention concerns a method for
controlling a
microwave heating system comprising the steps of (a) generating microwave
energy using one
or more microwave generators; (b) passing a plurality of articles through a
water-filled
microwave chamber via a conveyance system; (c) directing at least a portion of
the microwave
energy into the microwave chamber via one or more microwave launchers to
thereby heat at
least a portion of the articles; (d) during at least a portion of steps (a)
through (c), determining a
value for one or more microwave system parameters to thereby provide at least
one determined
parameter value; (e) comparing the determined parameter value with a
corresponding target
parameter value to determine a difference; and (f) based on the difference,
taking an action
with regard to the microwave heating system. The one or more microwave system
parameters
are selected from the group consisting of net microwave power, temperature of
the water in the
microwave chamber, flow rate of the water through the microwave chamber, and
conveyance
system speed.
[013] Another embodiment of the present invention concerns a method
controlling a
microwave heating system comprising the steps of (a) generating microwave
energy with at
least one microwave generator; (b) passing at least a portion of the microwave
energy through a
first waveguide segment; (c) discharging at least a portion of the microwave
energy from the
first waveguide segment into a microwave chamber via at least one microwave
launcher to
thereby heat a plurality of articles; (d) determining a first value for net
power discharged from
the microwave launcher using a first pair of directional couplers; (e)
determining a second value
for net power discharged from the microwave launcher using a second pair of
directional
couplers, wherein the first and second pairs of directional couplers are
independent from each
another; (f) comparing the first value and the second value to determine a
first difference; and
(g) taking an action with regard to the microwave heating system when the
difference is greater
than a predetermined amount.
[014] One embodiment of the present invention concerns a variable phase short
circuit
device for use in a microwave heating system. The device comprises a fixed
section defining a
first substantially rectangular opening and a rotatable section comprising a
housing and a
plurality of spaced-apart, substantially parallel plates received in the
housing. The housing
comprises opposite first and second end and the first end defines a second
opening adjacent to
the first opening of the fixed section. Each of the plates is coupled to the
second end of the
housing and extends generally toward the first and the second openings. The
rotatable section
CA 3130845 2021-09-10

is configured to be rotated relative to the fixed section on an axis of
rotation that extends
through the first and the second openings.
[015] Another embodiment of the present invention concerns a method for
heating a
plurality of articles in a microwave heating system comprising the steps of
(a) passing the
articles through a heating zone of a microwave chamber via a conveyance
system, wherein
each of the articles is maintained within the heating zone for an article
residence time (c); (b)
generating microwave energy with one or more microwave generators; (c) passing
at least a
portion of the microwave energy through a phase shifting device configured to
cyclically shift the
phase of the microwave energy at a phase shifting rate (t); (d) discharging at
least a portion of
the microwave energy exiting the phase shifting device into the heating zone
via at least one
microwave launcher; and (e) heating the articles in the heating zone with at
least a portion of the
microwave energy discharged therein, wherein the ratio of the article
residence time to the
phase shifting rate (TA) is at least 4:1.
[016] One embodiment of the present invention concerns a microwave system for
heating a plurality of articles. The system comprises at least one microwave
generator for
generating microwave energy, a microwave chamber, a conveyance system for
conveying the
articles through the microwave chamber, and a microwave distribution system
for directing at
least a portion of the microwave energy from the microwave generator to the
microwave
chamber. The microwave distribution system comprises at least three microwave
allocation
devices for dividing the microwave energy into at least three separate
portions. The microwave
distribution system further comprises at least three microwave launchers for
discharging the
separate portions of microwave energy into the microwave chamber. Each of the
microwave
allocation devices is configured to divide the microwave energy according to a
predetermined
power ratio, wherein the predetermined power ratio for at least one of the
microwave allocation
devices is not 1:1.
[017] Another embodiment of the present invention concerns a process for
heating a
plurality of articles using microwave energy comprising the steps of (a)
introducing the initial
quantity of microwave power into a microwave distribution manifold; (b) using
the microwave
distribution manifold to divide the initial quantity of microwave power into a
first launch
microwave fraction and a first distribution microwave fraction, wherein the
power ratio of the first
launch microwave fraction to the first distribution microwave fraction is not
1:1; (c) using the
microwave distribution manifold to divide the first distribution microwave
fraction into a second
launch microwave fraction and a second distribution microwave fraction; (d)
introducing the first
launch microwave fraction into a microwave heating chamber via a first
microwave launcher;
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and (e) introducing the second launch microwave fraction into the microwave
heating chamber
via a second microwave launcher.
[018] One embodiment of the present invention concerns a continuous process
for
heating a plurality of articles in a microwave heating system comprising the
steps of (a)
thermalizing the articles in a thermalization zone to thereby provide a
plurality of thermalized
articles having a substantially uniform temperature; (b) heating the
thermalized articles in a
microwave heating zone to thereby increase the average temperature of each
article by at least
50 C, wherein at least a portion of the heating is carried out at a heating
rate of at least 25 C
per minute; and (c) cooling the heated articles in a quench zone. The articles
are passed
through each of the thermalization zone, the microwave heating zone, and the
quench zone via
one or more conveyance systems, wherein the microwave heating system has an
overall
production rate of at least 20 packages per minute per convey line.
[019] Another embodiment of the present invention concerns a microwave system
for
heating a plurality of articles. The system comprises a thermalization chamber
for thermalizing
the articles to a substantially uniform temperature, a microwave heating
chamber disposed
downstream of the thermalization chamber for heating the thermalized articles,
and a quench
chamber disposed downstream of the microwave heating chamber for cooling the
heated
articles to a lower temperature. The microwave heating chamber is configured
to increase the
average temperature of the articles by at least 50 C at a heating rate of at
least 25 C per
minute. The system comprises at least one convey system configured to
transport the articles
through the thermalization chamber, the microwave heating chamber, and the
quench chamber.
The microwave system is configured to achieve an overall production rate of at
least 20
packages per minute per convey line.
[020] One embodiment of the present invention concerns a process for heating a
plurality of articles in a microwave heating system comprising the steps of
(a) passing the
articles through a pressurized microwave chamber via a conveyance system,
wherein the
microwave chamber is at least partly filled with a liquid medium; (b)
generating microwave
energy via one or more microwave generators; (c) introducing at least a
portion of the
microwave energy into the microwave chamber via one or more microwave
launchers; (d)
heating the articles in the microwave chamber using at least a portion of the
microwave energy
introduced therein; and (e) during at least a portion of the heating of step
(d), agitating at least a
portion of the liquid medium within the microwave chamber, wherein the
agitating includes
discharging a plurality of fluid jets toward the articles at multiple
locations within the microwave
chamber.
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[021] Another embodiment of the present invention concerns a process for
heating a
plurality of articles in a microwave heating system comprising the steps of
(a) therrnalizing the
articles in a thermalization chamber at least partially filled with a liquid
medium to thereby
produced thermalized articles having a substantially uniform temperature; and
(b) heating the
thermalized articles in a microwave chamber. The thermalizing of step (a)
includes discharging
a plurality of jets of the liquid medium toward the articles at multiple
locations within the
thermalization chamber.
[022] One embodiment of the present invention concerns a locking gate device
comprising a pair of spaced apart fixed members presenting opposing sealing
surfaces and
defining a gate-receiving space between the sealing surfaces, wherein each of
the fixed
members defines a flow-through opening circumscribed by one of the sealing
surfaces, wherein
the flow-through openings are substantially aligned with one another; and a
gate assembly
shiftable within the gate-receiving space between a closed position where the
gate assembly
substantially blocks the flow-through openings and an open position where the
gate assembly
does not substantially block the flow-through openings. The gate assembly
comprises a pair of
spaced apart sealing plates and a drive member disposed between the sealing
plates, wherein
when the gate assembly is in the closed position the drive member is shiftable
relative to the
sealing plates between a retracted position and an extended position. The gate
assembly
further comprises at least one pair of bearings disposed between the sealing
plates, wherein
shifting of the drive member from the retracted position to the extended
position causes the
bearings to force the sealing plates apart from one another and into a sealed
position where the
sealing plates engage the opposing sealing surfaces, wherein shifting of the
drive member from
the extended position to the retracted position allows the sealing plates to
retract towards one
another and into an unsealed position where the sealing plates are disengaged
from the
opposing sealing surfaces.
[023] Another embodiment of the present invention concerns a method for moving
one
or more articles within a pressurized system comprising the steps of (a)
passing one or more
articles from a first pressurized process zone to a second pressurized process
zone through a
flow-through opening; (b) shifting a pair of movable plates into the opening;
(c) moving the
plates apart from one another to thereby seal the plates against a pair of
opposed sealing
surfaces that at least partially define the opening, wherein the pair of
sealed plates substantially
isolates the first and the second process zones from one another; (d) creating
a pressure
differential of at least 15 psig across the pair of sealed plates; (e)
depressuring at least one of
the first and second process zones to equalize the pressure across the pair of
sealed plates; (f)
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moving the plates toward one another to thereby unseal the plates from the
sealing surfaces; (g)
shifting the pair of plates out of the opening; and (h) removing the articles
from the second
process zone back into the first process zone through the flow-through opening
and/or inserting
a new article into the second process zone through the flow-through opening.
[024] One embodiment of the present invention concerns a microwave heating
system
for heating a plurality of articles. The system comprises a liquid-filled
thermalization chamber, a
liquid-filled microwave chamber configured to operate at a higher pressure
than the
thermalization chamber, and a pressure lock system disposed between the
thermalization
chamber and the microwave chamber. The pressure lock system comprises a
pressure
adjustment chamber, a first locking gate valve, and a second locking gate
valve, wherein the
first locking gate valve is coupled between the thermalization chamber and the
pressure
adjustment chamber, wherein the second locking gate valve is coupled between
the pressure
adjustment chamber and the microwave chamber.
[025] Another embodiment of the present invention concerns a process for
heating a
plurality of articles in a microwave heating system comprising (a) passing a
plurality of articles
through a liquid-filled thermalization zone to thereby provide a plurality of
thermalized articles;
(b) introducing at least a portion of the thermalized articles into a pressure
adjustment zone,
wherein the pressure adjustment zone is at least partially defined between a
first and a second
locking gate valve, wherein the first locking gate valves is in a first open
position during at least
a portion of the introducing; (c) after the thermalized articles have been
introduced into the
pressure adjustment zone, shifting the first locking gate valve from the first
open position to a
first closed position to thereby substantially isolate the pressure adjustment
zone from the
thermalization zone; (d) shifting the second locking gate valve from a second
closed position to
a second open position to allow the articles to be transferred from the
pressure adjustment zone
to a liquid-filled microwave heating zone; and (e) after the articles have
been removed from the
pressure adjustment zone, shifting the second locking gate valve from the
second open position
back to the second closed position to thereby re-isolate the pressure
adjustment zone from the
microwave heating zone.
[026] One embodiment of the present invention concerns a method for heating a
plurality of articles comprising the steps of (a) heating a first test article
in a small-scale
microwave heating system while conveying the first test article through a
water-filled, small-
scale microwave chamber having a total internal volume of less than 50 cubic
feet, wherein at
least a portion of the heating of step (a) is accomplished using microwave
energy; (b)
determining a first prescribed heating profile based on the heating of step
(a), wherein the
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prescribed heating profile comprises at least one value for one or more
microwave system
parameters selected from the group consisting of net power discharged into the
chamber,
sequential microwave power distribution, average temperature of the water in
the
microwave chamber, flow rate of the water in the microwave chamber, and
residence
time of the article in the microwave chamber; and (c) heating a plurality of
first
commercial articles in a large-scale microwave heating system while conveying
the first
commercial articles through a water-filled, large-scale microwave chamber
having a total
internal volume of at least 250 cubic feet. At least a portion of the heating
of step (c) is
accomplished using microwave energy and wherein each of the first commercial
articles
is substantially similar in size and composition to the first test article,
wherein the heating
of step (c) is controlled in accordance with the first prescribed heating
profile determined
in step (b).
Accordingly, in one aspect the present invention resides in a microwave system
for heating a plurality of articles, said system comprising: a microwave
chamber
configured to receive said articles; a conveyance system for transporting said
articles
through said microwave chamber along a convey axis; a first microwave launcher
configured to propagate microwave energy into said microwave chamber along a
first
central launch axis, wherein a first launch tilt angle of at least 2 and not
more than 15 is
defined between said first central launch axis and a plane normal to said
convey axis; and
a second microwave launcher configured to propagate microwave energy into said
microwave chamber along a second central launch axis, wherein a second launch
tilt
angle of at least 2 is defined between said second central launch axis and a
plane normal
to said convey axis, wherein said first and said second microwave launchers
are
positioned on opposite sides of said microwave chamber.
In addition, the invention may reside in one or more future non-limiting
aspects,
and which may include without limitation.
1. A microwave system for heating a plurality of articles, said system
comprising:
a microwave chamber configured to receive said articles; a conveyance system
for
transporting said articles through said microwave chamber along a convey axis;
and a
first microwave launcher configured to propagate microwave energy into said
microwave
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chamber along a first central launch axis, wherein a first launch tilt angle
of at least 2 is
defined between said first central launch axis and a plane normal to said
convey axis.
2. The system of aspect No. 1, wherein said first launch tilt angle is less
than 15 .
3. The system of aspect No. 1, further comprising a second microwave launcher
configured to propagate microwave energy into said microwave chamber along a
second
central launch axis, wherein a second launch tilt angle of at least 2 is
defined between
said second central launch axis and a plane normal to said convey axis.
4. The system of aspect No. 3, wherein said first and said second central
launch
axes are substantially parallel to one another.
5. The system of aspect No. 3, wherein said first and said second microwave
launchers are positioned on opposite sides of said microwave chamber.
6. The system of aspect No. 5, wherein said first and said second microwave
launchers are oppositely facing.
7. The system of aspect No. 3, wherein said first and said second microwave
launchers are positioned on the same side of said microwave chamber.
8. The system of aspect No. 1, further comprising at least one microwave
generator for generating microwave energy having a wavelength (k), wherein
said first
microwave launcher defines at least one launch opening for discharging
microwave
energy into said microwave chamber, wherein said launch opening has a width (w-
i) and
a depth (di), wherein w-i is greater than di, wherein di is less than 0.625A.
9. The system of aspect No. 8, wherein said launch opening is elongated in the
direction of extension of said convey axis.
10. The system of aspect No. 8, wherein said first microwave launcher
comprises
an inlet and two or more launch openings for discharging microwave energy into
said
microwave chamber, wherein each of said two or more launch openings has a
depth of
less than 0.625 X.
11. The system of aspect No. 8, further comprising at least one substantially
microwave-transparent window disposed between said microwave chamber and said
launch opening.
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12. The system of aspect No. 1, wherein said microwave chamber is a
pressurized
chamber configured to operate at a pressure of at least 15 psig.
13. The system of aspect No. 1, further comprising a thermalization zone
located
upstream of said microwave chamber, said thermalization zone configured to
adjust the
temperature of said articles to a substantially uniform temperature prior to
introduction of
said articles into said microwave chamber.
14. The system of aspect No. 1, wherein said microwave system is configured
for
sterilization or pasteurization of foodstuffs, medical fluids, and/or medical
instruments
and wherein said microwave chamber is liquid-filled.
15. The system of aspect No. 1, wherein said microwave system is configured to
achieve an overall production rate of at least 150 packages per minute
equivalent.
16. The system of aspect No. 1, wherein said articles comprise packaged
foodstuffs, wherein said microwave chamber is configured to be water-filled
and
pressurized to at least 15 psig, wherein said microwave system is configured
to sterilize
said packaged foodstuffs at a rate of at least 150 packages per minute
equivalent.
17. A microwave system for heating a plurality of articles, said system
comprising: a microwave chamber configured to receive said articles; a
conveyance
system for transporting said articles through said microwave chamber along a
convey
axis; a first microwave launcher defining at least one launch opening for
discharging
microwave energy into said microwave chamber; and a substantially microwave-
transparent window disposed between said microwave chamber and said launch
opening,
wherein said window presents a chamber-side surface defining a portion of said
microwave chamber, wherein at least 50 percent of the total surface area of
said chamber-
side surface of said window is oriented at an angle of at least 2 from the
horizontal.
18. The system of aspect No. 17, wherein said microwave chamber is a liquid-
filled chamber configured to operate at a pressure of at least 10 psig.
19. The system of aspect No. 17, wherein at least 95 percent of the total
surface
area of said chamber-side surface is oriented at an angle of at least 2 from
the central
axis of elongation of said microwave chamber.
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20. The system of aspect No. 17, wherein said chamber-side surface of said
window comprises at least one convexity and/or at least one concavity.
21. The system of aspect No. 17, wherein said window has an average thickness
of at least 10 mm and is constructed of at least one material selected from
the group
consisting of glass-filled TEFLON, polytetrafluoroethylene, poly(methyl
methacrylate),
polyetherimide (PEI), aluminum oxide, glass, or combinations thereof.
22. The system of aspect No. 17, wherein said window is elongated in the
direction of extension of said convey axis.
23. The system of aspect No. 17, wherein said window is formed of glass-filled
TEFLON.
24. The system of aspect No. 17, further comprising a thermalization zone
located
upstream of said microwave chamber for adjusting the temperature of said
articles to a
substantially uniform temperature prior to the introduction of said articles
into said
microwave chamber.
25. The system of aspect No. 17, wherein said microwave system is configured
for sterilization or pasteurization of foodstuffs, medical fluids, and/or
medical
instruments.
26. The system of aspect No. 17, wherein said microwave system is configured
to
achieve an overall production rate of at least 150 packages per minute
equivalent.
27. The system of aspect No. 26, wherein said articles comprise packaged
foodstuffs, wherein said microwave chamber is configured to be water-filled
and
pressurized to at least 15 psig, wherein said microwave system is configured
to sterilize
said packaged foodstuffs at a rate of at least 150 packages per minute
equivalent.
28. A process for heating a plurality of articles in a microwave heating
system,
said process comprising: (a) passing a plurality of articles through a
microwave heating
chamber via a conveyance system, wherein said microwave heating chamber is at
least
partially filled with a liquid medium; (b) generating microwave energy using
one or more
microwave generators; (c) introducing at least a portion of said microwave
energy into
said microwave chamber via at least one microwave launcher, wherein at least a
portion
of said microwave energy introduced into said microwave chamber is discharged
at a
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launch tilt angle of at least 2'; and (d) heating said articles in said
microwave heating
chamber using at least a portion of said microwave energy discharged therein.
29. The process of aspect No. 28, wherein said introducing of step (c) is
carried
out using two or more microwave launchers disposed on opposite sides of said
microwave chamber, wherein each launcher discharges microwave energy at a
launch tilt
angle of at least 2 and not more than 15 .
30. The process of aspect No. 28, wherein said articles comprise packaged
foodstuffs or packaged medical fluids, wherein said microwave chamber is a
water-filled
chamber pressurized to a pressure of at least 10 psig, wherein said process
sterilizes said
packaged foodstuffs or said packaged medical fluids at a rate of at least 150
packages per
minute equivalent.
31. A microwave system for heating a plurality of articles, said microwave
system
comprising: a microwave generator for generating microwave energy having a
predominant wavelength (A); a conveyance system for conveying said articles
along a
convey axis; and a first microwave launcher for launching at least a portion
of said
microwave energy toward said articles conveyed by said conveyance system,
wherein
said first microwave launcher defines at least one launch opening having a
width (W-i)
and a depth (D-i), wherein W-i is greater than D-i, wherein D-i is not more
than 0.625 X.
32. The system of aspect No. 31, wherein D-i is not more than 0.50 X.
33. The system of aspect No. 31, wherein said first microwave launcher
comprises a set of broader opposing side walls and a set of narrower opposing
end walls,
wherein each of said side walls and said end walls presents a terminal edge,
wherein the
terminal edges of said side walls and said end walls cooperatively define said
launch
opening, wherein said width (W-i) of said launch opening is defined by the
distance
between the terminal edges of said end walls and said depth (D-i) of said
launch opening
is defined by the distance between the terminal edges of said side walls.
34. The system of aspect No. 33, wherein the terminal edges of said side walls
extend substantially parallel to said convey axis.
35. The system of aspect No. 33, wherein said launch opening is rectangular.
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36. The system of aspect No. 33, wherein said side walls have a width flare
angle
(OW) of at least 50
.
37. The system of aspect No. 33, wherein said end walls have a depth flare
angle
(Od) of not more than 0 .
38. The system of aspect No. 37, wherein Od is less than 0 .
39. The system of aspect No. 31, wherein said first microwave launcher defines
a
microwave inlet and at least a first and a second launch opening, wherein said
first launch
opening has said width (W-i) and said depth (D-i), wherein said second launch
opening
has a width (W2) and a depth (D2), wherein W2 is greater than D2, wherein D2
is not
more than 0.625 X.
40. The system of aspect No. 39, wherein said microwave launcher comprises at
least one dividing septum disposed within the interior region said microwave
launcher
between said microwave inlet and said launch openings, wherein said septum at
least
partially defines said first and said second launch openings.
41. The system of aspect No. 39, wherein first and said second launch openings
are adjacent to one another and are aligned transverse to said convey axis.
42. The system of aspect No. 39, wherein said microwave inlet has a depth
(DO),
wherein D-i and D2 are less than or equal to DO.
43. The system of aspect No. 39, wherein said first microwave launcher further
comprises a third launch opening having a width (W3) and a depth (D3), wherein
W3 is
greater than D3, wherein none of D-i , D2, or D3 is more than 0.50 k.
44. The system of aspect No. 43, wherein said first microwave launcher further
comprises at least two dividing septa disposed between said microwave inlet
and said
launch openings, said septa collectively defining at least three separate
microwave
pathways for propagating microwave energy from said microwave inlet to each of
said
first, second, and third launch openings, wherein at least one of said
separate microwave
pathways is longer than at least one other of said separate microwave
pathways.
45. The system of aspect No. 31, further comprising a microwave chamber
through which said articles are conveyed by said conveyance system, wherein
said
articles comprise
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packaged foodstuffs, wherein said microwave chamber is configured to be liquid-
filled
and pressurized to at least 10 psig, wherein said microwave system is
configured to
pasteurize and/or sterilize said packaged foodstuffs at a rate of at least 20
packages per
minute per convey line.
46. A microwave system for heating a plurality of articles, said microwave
system
comprising: a microwave generator for generating microwave energy having a
predominant wavelength (A); a microwave chamber configured to receive said
articles;
and a microwave distribution system =for directing at least a portion of said
microwave
energy from said microwave generator to said microwave chamber, wherein said
microwave distribution system comprises a first microwave launcher, wherein
said first
microwave launcher defines a microwave inlet for receiving at least a portion
of said
microwave energy and at least one launch opening for discharging said
microwave
energy into said microwave chamber, wherein said microwave inlet has a depth
(d0) and
said launch opening has a depth (d-t), wherein said dO is greater than d-I.
47. The system of aspect No. 46, wherein di is less than 0.625A.
48. The system of aspect No. 46, wherein said first microwave launcher
comprises a set of opposing side walls and a set of opposing end walls each
extending
from said microwave inlet to said launch opening, wherein said side walls are
broader
than said end walls, wherein each of said side walls defines a width flare
angle of at least
2 and each of said end walls defines a depth flare angle of less than 0 .
49. The system of aspect No. 46, wherein said first microwave launcher defines
a
second launch opening having a depth (d2), wherein said dO is greater than d2,
wherein di
and d2 are both less than 0.625 X.
50. The system of aspect No. 49, wherein said first microwave launcher further
comprises a third launch opening having a depth (d3), wherein dO is greater
than d3,
wherein d-t, d2, and d3 are each less than 0.50A.
51. The system of aspect No. 46, further comprising a thermalization zone
upstream of said microwave chamber for heating said articles to a
substantially uniform
temperature before said articles are introduced into said microwave chamber.
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52. The system of aspect No. 46, wherein said microwave chamber is configured
to be liquid-filled and pressurized to at least 10 psig.
53. A microwave system for heating a plurality of articles, said microwave
system
comprising: a microwave chamber configured to receive said articles; a
conveyance
system for transporting said articles through said microwave chamber along a
convey
axis; and a first microwave launcher defining a microwave inlet and two or
more launch
openings configured to discharge microwave energy into said microwave chamber,
wherein the center points of adjacent launch openings are laterally spaced
from one
another relative to said convey axis.
54. The system of aspect No. 53, wherein said first microwave launcher
comprises at least one septum disposed within said launcher at least partially
defining at
least two pathways through which said microwave energy propagates from said
inlet to
each of said launch openings.
55. The system of aspect No. 53, wherein said first microwave launcher
comprises three or more launch openings and at least two septa defining at
least a first,
second, and third pathway through which microwave energy can propagate from
said
microwave inlet to said launch openings, wherein at least one of said first,
second, and
third pathways is longer than at least one other of said first, second, and
third pathways.
56. The system of aspect No. 53, wherein said first microwave launcher defines
a
set of opposing side walls and a set of opposing end walls each extending from
said
microwave inlet to said launch openings, wherein said side walls are broader
than said
end walls, wherein each of said side walls defines a width flare angle of at
least 2 and
each of said end walls defines a depth flare angle not more than 0 .
57. The system of aspect No. 56, wherein said depth flare angle of said end
walls
is less than 0 .
58. The system of aspect No. 53, further comprising a second microwave
launcher
disposed on a generally opposite side of said microwave chamber from said
first
microwave launcher, wherein said second microwave launcher defines a second
microwave inlet and at least two more launch openings configured to discharge
microwave energy into said microwave chamber.
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59. The system of aspect No. 53, wherein said microwave chamber is a
pressurized microwave chamber.
60. The system of aspect No. 53, wherein said articles comprise packaged
foodstuffs, wherein said microwave chamber is configured to be water-filled
and
pressurized to at least 15 psig, wherein said microwave system is configured
to sterilize
said packaged foodstuffs at a rate of at least 20 packages per minute per
convey line.
61. A microwave launcher comprising: a microwave inlet for receiving
microwave energy having a wavelength (A); at least one launch opening for
discharging
at least a portion of said microwave energy; a pair of opposing launcher end
walls and a
pair of opposing launcher sidewalls defining a microwave pathway therebetween,
wherein said microwave pathway is configured to permit the passage of
microwave
energy from said microwave inlet to said launch opening; and a pair of
inductive iris
panels respectively coupled to and extending inwardly from said pair of end
walls,
wherein each of said inductive iris panels extends partially into said
microwave pathway
to define therebetween an inductive iris through which at least a portion of
said
microwave energy routed from said microwave inlet to said launch opening can
pass.
62. The launcher of aspect No. 61 , wherein said inductive iris is disposed
between said microwave inlet and said launch opening, wherein said microwave
launcher
has a length (L) defined by the minimum distance between said microwave inlet
and said
launch opening, wherein said inductive iris is spaced from said microwave
inlet by at
least 0.1 L.
63. The launcher of aspect No. 61, wherein said microwave launcher defines a
central launch axis extending through the geometric center of said microwave
pathway,
wherein said inductive iris panels extend substantially perpendicular to said
central
launch axis.
64. The launcher of aspect No. 61, wherein said side walls are broader than
said
end walls, wherein said side walls have a width flare angle of at least 2 .
65. The launcher of aspect No. 64, wherein said end walls have a depth flare
angle
of not more than 0 .
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66. The launcher of aspect No. 61, wherein said launch opening has a width (w-
i)
and a depth (d-i), wherein w-i is greater than d-t , wherein d-t is less than
0.50A.
67. The launcher of aspect No. 61, wherein said microwave launcher defines at
least two launch openings and at least two microwave paths extending from said
microwave inlet to one of said launch openings, wherein each of said iris
panels extends
into at least two of said microwave paths.
68. The launcher of aspect No. 67, further comprising at least one septum
separating and at least partially defining each of said microwave paths,
wherein said
septum is coupled to and extends between said end walls of said launcher,
wherein the
thickness of said septum is less than 0.1 A.
69. A microwave system for heating a plurality of articles, said system
comprising: a microwave generator for generating microwave energy having a
wavelength (A); a microwave chamber configured to receive said articles; a
conveyance
system for conveying said articles through said microwave chamber along a
convey axis;
and a microwave distribution system for directing at least a portion of said
microwave
energy from said microwave generator to said microwave chamber, wherein said
microwave distribution system comprises a first microwave splitter for
dividing at least a
portion of said microwave energy into two or more separate portions and at
least one pair
of microwave launchers each defining a microwave inlet and at least one launch
opening
for discharging microwave energy into said microwave chamber, wherein said
microwave distribution system further comprises a first inductive iris
disposed between
said first microwave splitter and said launch opening of one of said microwave
launchers.
70. The system of aspect No. 69, wherein said microwave distribution system
further comprises a second inductive iris disposed between said first
microwave splitter
and said launch opening of the other launcher of said pair of microwave
launchers.
71. The system of aspect No. 69, wherein said first inductive iris is disposed
between said microwave inlet and said launch opening of said microwave
launcher.
72. The system of aspect No. 71, wherein each of said microwave launchers
comprises at least two launch openings having respective depths (d-t and d2),
wherein d-t
and d2 are both less than 0.625A.
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73. The system of aspect No. 69, wherein said first inductive iris is disposed
between said first microwave splitter and said microwave inlet of said one of
said
microwave launchers.
74. The system of aspect No. 73, wherein said microwave distribution system
further comprises a second inductive iris disposed between said first
microwave splitter
and the microwave inlet of the other launcher of said pair of microwave
launchers.
75. The system of aspect No. 69, wherein said microwave distribution system
further comprises a second splitter for dividing at least a portion of said
microwave
energy into two or more additional portions, an additional pair of microwave
launchers
defining a second microwave inlet and at least one launch opening for
discharging
microwave energy into said microwave chamber, and a second inductive iris
disposed
between said second microwave splitter and said launch opening of one of said
launchers
of said additional pair of microwave launchers.
76. The system of aspect No. 75, wherein each of said launchers of said pair
of
microwave launchers is disposed on the same side of said microwave chamber.
77. The system of aspect No. 69, wherein one launcher of said pair of
microwave
launchers is disposed on an opposite side of said microwave chamber from the
other of
said pair of microwave launchers.
78. The system of aspect No. 69, wherein said microwave chamber is a
pressurized microwave chamber.
79. The system of aspect No. 69, further comprising a thermalization zone for
adjusting the temperature of said articles to a substantially uniform
temperature prior to
introducing the thermalized articles into said microwave chamber.
80. The system of aspect No. 69, wherein said articles comprise packaged
foodstuffs, wherein said microwave chamber is configured to be liquid-filled
and
pressurized to at least 10 psig, wherein said microwave system is configured
to pasteurize
and/or sterilize said packaged foodstuffs at a rate of at least 20 packages
per minute per
convey line.
81. A process for heating a plurality of articles in a microwave heating
system,
said process comprising: (a) passing a plurality of articles through a
microwave heating
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chamber along one or more convey lines of a conveyance system; (b) generating
microwave energy using one or more microwave generators; (c) dividing at least
a
portion of said microwave energy into two or more separate portions; (d)
discharging said
portions of microwave energy into said microwave heating chamber via two or
more
microwave launchers; (e) subsequent to said dividing of step (b) and prior to
said
discharging of step (c), passing at least one of said portions of microwave
energy through
a first inductive iris; and (f) heating said articles in said microwave
heating chamber
using at least a portion of said microwave energy discharged therein.
82. The process of aspect No. 81, further comprising, subsequent to said
dividing
of step (c) and prior to said discharging of step (d), passing the another of
said portions of
microwave energy through a second inductive iris.
83. The process of aspect No. 81, wherein said first inductive iris is
disposed
within the interior of one of said microwave launchers and is positioned
between the
microwave inlet and said launch opening of said microwave launcher.
84. The process of aspect No. 81, wherein at least two of said microwave
launchers are located on opposite sides of said microwave chamber.
85. The process of aspect No. 84, wherein at least two of said microwave
launchers are oppositely facing launchers.
86. The process of aspect No. 81, wherein at least two of said microwave
launchers are located on the same side of said microwave chamber.
87. The process of aspect No. 81 , wherein said microwave chamber is at least
partially filled with a liquid medium and pressurized to at least 10 psig.
88. The process of aspect No. 87, wherein said articles are selected from the
group consisting of packaged foodstuffs, packaged medical fluids, and medical
instruments and said process is a pasteurization and/or sterilization process.
89. A method for controlling a microwave heating system, said method
comprising: (a) generating microwave energy using one or more microwave
generators;
(b) passing a plurality of articles through a water-filled microwave chamber
via a
conveyance system; (c) directing at least a portion of said microwave energy
into said
microwave chamber via one or more microwave launchers to thereby heat at least
a
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portion of said articles; (d) during at least a portion of steps (a) through
(c), determining a
value for one or more microwave system parameters to thereby provide at least
one
determined parameter value; (e) comparing said determined parameter value with
a
corresponding target parameter value to determine a difference; and (0 based
on said
difference, taking an action with regard to said microwave heating system,
wherein said
one or more microwave system parameters are selected from the group consisting
of net
microwave power, temperature of the water in said microwave chamber, flow rate
of the
water through said microwave chamber, and conveyance system speed.
90. The method of aspect No. 89, wherein step (0 is carried out when said
difference determined in step (e) is at least 5 percent of said target value.
91. The method of aspect No. 89, wherein said determining of step (d) includes
determining a value for temperature of the water in said microwave chamber,
wherein
said target value used during said comparing of step (e) is not more than 130
C.
92. The method of aspect No. 89, wherein said determining of step (d) includes
determining a value for flow rate of the water through said microwave chamber,
wherein
said target value used during said comparing of step (e) is at least 15
gallons per minute
(gpm).
93. The method of aspect No. 89, wherein said determining of step (d) includes
determining a value for net microwave power, wherein said target value used
during said
comparing of step (e) is at least 75 kW.
94. The method of aspect No. 93, wherein said net microwave power is measured
using a pair of directional couplers disposed within a waveguide upstream of
said at least
one microwave launcher.
95. The method of aspect No. 89, wherein said determining of step (d) includes
determining a value for conveyance system speed, wherein said target value
used during
said comparing of step (e) is not more than 10 feet per second (fps).
96. The method of aspect No. 89, wherein said one or more microwave system
parameters are selected from the group consisting of minimum net microwave
power,
minimum temperature of the water in said microwave chamber, minimum flow rate
of
water through said microwave chamber, and maximum speed of said conveyance
system,
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wherein said action taken during step (f) comprises removing and/or isolating
at least a
portion of said articles from said microwave chamber.
97. The method of aspect No. 96, wherein said determining of step (d) includes
determining a value for the minimum temperature of the water in said microwave
chamber, wherein said target value used during said comparing of step (e) is
at least
120 C.
98. The method of aspect No. 96, wherein said determining of step (d) includes
determining a value for minimum flow rate of water through said microwave
chamber,
wherein said target value used during said comparing of step (e) is at least 5
gpm.
99. The method of aspect No. 96, wherein said determining of step (d) includes
determining a value for minimum net microwave power discharged, wherein said
target
value used during said comparing of step (e) is at least 50 kW.
100. The method of aspect No. 96, wherein said determining of step (d)
includes
determining a value for maximum speed of said conveyance system, wherein said
target
value used during said comparing of step (e) is not more than 15 fps.
101. The method of aspect No. 89, wherein at least a portion of steps (a)
through
(f) are carried out via an automatic control system.
102. The method of aspect No. 89, further comprising, prior to step (b),
passing
said articles through a thermalization zone to thereby thermalize said
articles to a
substantially uniform outlet temperature.
103. The method of aspect No. 89, wherein said articles comprise packages
containing foodstuffs, medical fluids, or medical instruments.
104. The method of aspect No. 89, wherein said microwave chamber is at least
partially filled with a liquid medium and is pressurized to at least 10 psig,
wherein said
microwave heating system is a pasteurization and/or sterilization system.
105. The method of aspect No. 104, wherein said articles comprise packaged
foodstuffs, wherein said microwave chamber is a water-filled chamber
pressurized to at
least 15 psig, wherein said microwave heating system has a production rate of
at least 20
packages per minute per convey line.
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106. A method of controlling a microwave heating system, said method
comprising: (a) generating microwave energy with at least one microwave
generator; (b)
passing at least a portion of said microwave energy through a first waveguide
segment;
(c) discharging at least a portion of said microwave energy from said first
waveguide
segment into a microwave chamber via at least one microwave launcher to
thereby heat a
plurality of articles; (d) determining a first value for net power discharged
from said
microwave launcher using a first pair of directional couplers; (e) determining
a second
value for net power discharged from said microwave launcher using a second
pair of
directional couplers, wherein said first and second pairs of directional
couplers are
independent from each another; (f) comparing said first value and said second
value to
determine a first difference; and (g) taking an action with regard to said
microwave
heating system when said difference is greater than a predetermined amount.
107. The method of aspect No. 106, wherein the value of said predetermined
amount is at least 1 percent of said first or said second values determined in
steps (d) or
(e).
108. The method of aspect No. 106, wherein said determining of steps (d)
and/or
(e) respectively comprise using one of said directional couplers of said first
pair and one
of said directional couplers of said second pair to measure respective values
for forward
power, and using the other of said directional couplers of said first pair and
the other of
said directional couplers of said second pair to measure respective values for
reflected
power, wherein the differences between said values for forward and reflected
power
determined for each of said first and said second pairs of directional
couplers are said
first and said second values for net power discharged, respectively.
109. The method of aspect No. 106, further comprising, comparing said first
value
for net power discharged to a target value to determine a second difference
and, based on
said second difference, adjusting the power output of said microwave
generator.
110. The method of aspect No. 106, wherein said action of step (g) is carried
out
when the lower of said first and said second values for net power discharged
drops below
a minimum power level.
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111. The method of aspect No. 106, wherein said action of step (g) is selected
from the group consisting of (i) shutting down said microwave generator, (ii)
removing
one or more articles from said heating chamber and isolating or disposing of
the removed
article, and (iii) increasing or decreasing the power output of said
generator.
112. The method of aspect No. 106, wherein at least a portion of steps (d)
through
(g) is carried out with an automatic control system.
113. The method of aspect No. 106, wherein said passing of step (b) includes
dividing at least a portion of said microwave energy generated in step (a)
into two
separate portions with a microwave splitter, wherein said discharging of step
(c)
comprises respectively discharging each of said two separate portions of
microwave
energy into said microwave chamber via a pair of opposed microwave launchers.
114. The method of aspect No. 25, wherein said first and said second pair of
directional couplers is disposed between said splitter and one of said
launchers of said
pair of launchers.
115. The method of aspect No. 106, wherein said microwave chamber is a
pressurized microwave chamber for pasteurizing and/or sterilizing said
articles.
116. The method of aspect No. 27, wherein said articles are selected from the
group consisting of foodstuffs, packaged medical fluids, and medical
instruments.
117. The method of aspect No. 28, wherein said articles comprise packaged
foodstuffs, wherein said microwave chamber is a water-filled chamber
pressurized to at
least 15 psig, wherein said microwave heating system has a production rate of
at least 20
packages per minute per convey line.
118. A variable phase short circuit device for use in a microwave heating
system,
said device comprising: a fixed section defining a first substantially
rectangular opening;
and a rotatable section comprising a housing and a plurality of spaced-apart,
substantially
parallel plates received in said housing, wherein said housing comprises
opposite first
and second ends, wherein said first end defines a second opening adjacent to
said first
opening of said fixed section, wherein each of said plates is coupled to said
second end of
said housing and extends generally toward said first and said second openings,
wherein
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said rotatable section is configured to be rotated relative to said fixed
section on an axis
of rotation that extends through said first and said second openings.
119. The device of aspect No. 1 18, wherein said housing has a length (L-i), a
width (W-i) and a depth (D-i), wherein said variable phase short circuit is
configured to
pass microwave energy having a wavelength (X) from said first opening to said
housing,
wherein at least one of W-i and D-i is greater than 0.5 X..
120. The device of aspect No. 119, wherein both W-i and D-i are less than 1 X.
121. The device of aspect No. 119, wherein the ratio of is less than 1.5:1.
122. The device of aspect No. 1 18, wherein said variable phase short circuit
is
configured to pass microwave energy having a wavelength (X) from said first
opening to
said housing, wherein adjacent plates within said housing are spaced apart by
no more
than 0.1 k.
123. The device of aspect No. 118, wherein each of said plates presents a
distal
end having a first surface area facing toward said first and second openings,
wherein said
second end of said housing defines an exposed inner surface area located
between said
plates and facing toward said first and second openings, wherein the ratio of
the sum of
the first surface areas of the distal ends of said plates to the exposed
surface area of said
second end of said housing is at least 0.5:1 and not more than 2:1.
124. The device of aspect No. 1 18, wherein said variable phase short circuit
is
configured to pass microwave energy having a wavelength (X) from said first
opening
into said housing, wherein said plates extend toward said first side for a
distance of at
least 0.25 X.
125. The device of aspect No. 118, wherein said first opening has a length
(L2), a
width (W2) and a depth (D2), wherein the ratio of W2:D2 is greater than 1
.25:1.
126. The device of aspect No. 125, wherein said housing has a length (L-i), a
width (W-i), and a depth (D-i), wherein W-i and W2 are substantially equal.
127. The device of aspect No. 126, wherein the ratio of is less than 1.2:1.
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128. The device of aspect No. 118, further comprising a microwave choke
disposed proximate said first and second openings and configured to inhibit
leakage of
microwave energy from between said fixed and rotatable sections.
129. The device of aspect No. 118, further comprising an actuator for rotating
said
rotatable section at a speed of at least 50 revolutions per minute (rpm).
130. The device of aspect No. 118, wherein said rotatable section is
configured to
be adjusted manually via rotation to a desired position.
131. The device of aspect No. 118, wherein said variable phase short circuit
is
configured to be connected to a coupler and utilized as a phase shifting
device in a
microwave system for heating a plurality of articles.
132. A method for heating a plurality of articles in a microwave heating
system,
said method comprising: (a) passing said articles through a heating zone of a
microwave
chamber via a conveyance system, wherein each of said articles is maintained
within said
heating zone for an article residence time (x); (b) generating microwave
energy with one
or more microwave generators; (c) passing at least a portion of said microwave
energy
through a phase shifting device configured to cyclically shift the phase of
the microwave
energy at a phase shifting rate (t); (d) discharging at least a portion of
said microwave
energy exiting said phase shifting device into said heating zone via at least
one
microwave launcher; and (e) heating said articles in said heating zone with at
least a
portion of said microwave energy discharged therein, wherein the ratio of said
article
residence time to said phase shifting rate (x:t) is at least 4:1 .
133. The method of aspect No. 132, wherein said phase shifting rate is at
least 1 .5
cycles per second.
134. The method of aspect No. 132, wherein ratio of said article residence
time to
said phase shifting rate (x:t) is no more than 10:1.
135. The method of aspect No. 132, wherein said article residence time is at
least
2 seconds and not more than 30 seconds.
136. The method of aspect No. 132, wherein said phase shifting device is a
rotatable phase shifting device.
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137. The method of aspect No. 136, wherein said passing of step (c) includes
rotating said phase shifting device at a speed of at least 120 revolutions per
minute (rpm).
138. The method of aspect No. 136, wherein said rotatable phase shifting
device
comprises a fixed section and a rotatable section comprising a housing and a
plurality of
plates disposed within said housing, wherein said rotatable section is
configured to rotate
relative to said fixed section.
139. The method of aspect No. 132, further comprising, simultaneously with
step
(d), discharging a portion of said microwave energy generated in step (b) into
said
heating zone, wherein said portion has not been passed through a phase
shifting device.
140. The method of aspect No. 132, wherein said discharging of step (d)
comprises directing said microwave energy into said heating zone via a pair of
launchers
disposed on generally opposite sides of said heating zone.
141. The method of aspect No. 132, wherein said launchers of said pair are
staggered relative to one another along the central axis of elongation of said
microwave
chamber.
142. The method of aspect No. 132, wherein said microwave chamber is a
pressurized microwave chamber.
143. The method of aspect No. 132, wherein microwave heating system sterilizes
and/or pasteurizes one or more of said articles.
144. The method of aspect No. 143, wherein said microwave chamber is a liquid
filled chamber and wherein said articles are selected from the group
consisting of
packaged foodstuffs, medical fluids, and medical instruments.
145. The method of aspect No. 132, wherein said articles comprise packaged
foodstuffs, wherein said microwave chamber water-filled and pressurized to at
least 15
psig during said heating of step (e), wherein said microwave system sterilizes
and/or
pasteurizes said foodstuffs at an overall production rate of at least 20
packages per minute
per convey line.
146. A microwave system for heating a plurality of articles, said system
comprising: at least one microwave generator for generating microwave energy;
a
microwave chamber; a conveyance system for conveying said articles through
said
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microwave chamber; and a microwave distribution system for directing at least
a portion
of said microwave energy from said microwave generator to said microwave
chamber,
wherein said microwave distribution system comprises at least three microwave
allocation devices for dividing said microwave energy into at least three
separate
portions, wherein said microwave distribution system further comprises at
least three
microwave launchers for discharging said separate portions of microwave energy
into
said microwave chamber, wherein each of said microwave allocation devices is
configured to divide said microwave energy according to a predetermined power
ratio,
wherein said predetermined power ratio for at least one of said microwave
allocation
devices is not 1:1 .
147. The system of aspect No. 146, wherein said predetermined power ratio for
two or more of said microwave allocation devices is not 1 :1 .
148. The system of aspect No. 146, wherein said microwave allocation devices
are configured such that the amount of power discharged from each of said
microwave
launchers is approximately the same.
149. The system of aspect No. 146, wherein said microwave allocations devices
are configured such that the amount of power discharged from one or more of
said
microwave launchers is different than the amount of microwave power discharged
from
at least one other of said microwave launchers.
150. The system of aspect No. 146, wherein said microwave system comprises n
microwave launchers and (n-1 ) microwave allocation devices disposed between
said
microwave generator and said n microwave launchers, wherein n is at least 4.
151. The system of aspect No. 146, wherein said microwave allocation devices
are selected from the group consisting of splitters, inductive irises, or
combinations
thereof.
152. The system of aspect No. 146, wherein said microwave launchers are
disposed on a first side of said microwave chamber and are axially spaced from
one
another along the central axis of elongation of said microwave chamber.
153. The system of aspect No. 7, wherein said microwave distribution system
further comprises at least three additional microwave launchers disposed on a
second side
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of said microwave chamber and a microwave splitter for dividing said microwave
energy
into separate portions to be directed to said launchers and said additional
launchers,
wherein said additional launchers are axially spaced from one another along
the central
axis of elongation of said microwave chamber.
154. The system of aspect No. 8, further comprising at least three more
microwave allocation devices disposed between said splitter and said
additional launchers
for dividing microwave energy into at least three additional portions, wherein
said
additional launchers are configured to discharge said additional portions into
said
microwave chamber.
155. The system of aspect No. 9, wherein at least one of said at least three
more
microwave allocation devices are configured to divide said microwave energy
passing
therethrough according to another predetermined power ratio that is not 1 :1.
156. The system of aspect No. 146, wherein said microwave chamber is a
pressurized microwave chamber.
157. The system of aspect No. 146, further comprising a thermalization zone
for
heating said articles to a substantially uniform temperature prior to the
thermalized
articles being introduced into said microwave chamber.
158. The system of aspect No. 146, wherein said microwave system is configured
for the sterilization or pasteurization of foodstuffs, medical fluids, and/or
medical
instruments.
159. The system of aspect No. 146, wherein said articles comprise packaged
foodstuffs, wherein said microwave chamber is configured to be liquid-filled
and
pressurized to at least 15 psig, wherein said microwave system is configured
to sterilize
said packaged foodstuffs at a rate of at least 20 packages per minute per
convey line.
160. A process for heating a plurality of articles using microwave energy,
said
process comprising: (a) introducing said initial quantity of microwave power
into a
microwave distribution manifold; (b) using said microwave distribution
manifold to
divide said initial quantity of microwave power into a first launch microwave
fraction
and a first distribution microwave fraction, wherein the power ratio of said
first launch
microwave fraction to said first distribution microwave fraction is not 1 :1 ;
(c) using said
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microwave distribution manifold to divide said first distribution microwave
fraction into
a second launch microwave fraction and a second distribution microwave
fraction; (d)
introducing said first launch microwave fraction into a microwave heating
chamber via a
first microwave launcher; and (e) introducing said second launch microwave
fraction into
said microwave heating chamber via a second microwave launcher.
161. The process of aspect No. 160, wherein the power ratio of said first
launch
microwave fraction to said first distribution microwave fraction is less than
1 :1.
162. The process of aspect No. 160, wherein said first and second microwave
launchers are located on the same side of said microwave heating chamber.
163. The process of aspect No. 160, wherein said initial quantity of microwave
power is introduced into said microwave chamber using only said first
microwave
launcher, said second microwave launcher, and a third microwave launcher.
164. The process of aspect No. 163, further comprising using said entire
second
distribution microwave fraction as a third launch microwave fraction and
introducing said
third launch microwave fraction into said microwave heating chamber via said
third
microwave launcher.
165. The process of aspect No. 163, wherein the power ratio of said second
launch microwave fraction to said second distribution microwave fraction is in
the range
of 0.8:1 to 1.2:1.
166. The process of aspect No. 160, further comprising using said microwave
distribution manifold to divide said second distribution microwave fraction
into a third
launch microwave fraction and a third distribution microwave fraction, and
introducing
said third launch microwave fraction into said microwave heating chamber via a
third
microwave launcher.
167. The process of aspect No. 166, wherein the power ratio of said second
launch microwave fraction to said second distribution microwave fraction is
not 1 :1.
168. The process of aspect No. 166, wherein the power ratio of said second
launch microwave fraction to said second distribution microwave fraction is
less than 1
:1.
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169. The process of aspect No. 166, wherein said initial quantity of microwave
power is introduced into said microwave chamber using only said first
microwave
launcher, said second microwave launcher, said third microwave launcher, and a
fourth
microwave launcher.
170. The process of aspect No. 169, further comprising using said entire third
distribution microwave fraction as a fourth launch microwave fraction and
introducing
said fourth launch microwave fraction into said microwave heating chamber via
said
fourth microwave launcher and wherein said first, second, third, and fourth
microwave
launchers are located on the same side of said microwave chamber.
171. The process of aspect No. 170, wherein the power ratio of said third
launch
microwave fraction to said third distribution microwave fraction is in the
range of 0.8:1
to 1.2:1.
172. The process of aspect No. 160, further comprising heating articles in
said
microwave chamber, wherein at least a portion of said heating is provided by
microwave
energy introduce via said first and second microwave launchers and said
heating is
carried out while said articles are being conveyed through said microwave
chamber.
173. The process of aspect No. 172, wherein said microwave chamber is liquid-
filled and pressurized to at least 15 psig during said heating.
174. The process of aspect No. 173, wherein said articles are packaged
foodstuffs,
wherein said heating causes sterilization or pasteurization of said
foodstuffs.
175. The process of aspect No. 174, wherein said heating is carried out at a
production rate of at least 20 packages per minute per convey line.
176. A continuous process for heating a plurality of articles in a microwave
heating system, said process comprising: (a) thermalizing said articles in a
thermalization
zone to thereby provide a plurality of thermalized articles having a
substantially uniform
temperature; (b) heating said thermalized articles in a microwave heating zone
to thereby
increase the average temperature of each article by at least 50 C, wherein at
least a
portion of said heating is carried out at a heating rate of at least 25 C per
minute; and (c)
cooling the heated articles in a quench zone, wherein said articles are passed
through
each of said thermalization zone, said microwave heating zone, and said quench
zone via
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one or more conveyance systems, wherein said microwave heating system has an
overall
production rate of at least 20 packages per minute per convey line.
177. The process of aspect No. 176, wherein said thermalization zone is at
least
partially filled with a liquid medium.
178. The process of aspect No. 176, wherein said heating of step (b) includes
discharging microwave energy into said microwave chamber via at least one pair
of
opposed launchers disposed on generally opposite sides of said microwave
chamber.
179. The process of aspect No. 178, wherein said opposed launchers are
staggered
relative to one another along the central axis of elongation of said microwave
chamber.
180. The process of aspect No. 178, wherein said opposed launchers are
oppositely facing launchers.
181. The process of aspect No. 176, wherein at least a portion of said heating
of
step (b) is carried out under a pressure of at least 10 psig.
182. The process of aspect No. 176, wherein said microwave heating zone
comprises a microwave chamber at least partially filled with a liquid medium,
wherein at
least a portion of said heating of step (b) is carried out at a temperature
above the normal
boiling point of said liquid medium.
183. The process of aspect No. 176, wherein at least a portion of said
thermalizing
of step (a) and/or said cooling of step (c) is carried out at a different
pressure than said
heating of step (b), further comprising, subsequent to said thermalizing of
step (a) and/or
at least a portion of said cooling of step (c), passing said articles through
at least one
pressure adjustment zone to thereby at least partially equalize the pressure
between said
thermalization zone and said microwave chamber and/or said microwave chamber
and
said quench zone.
184. The process of aspect No. 176, wherein said substantially uniform
temperature of said articles exiting said thermalization zone is at least 20 C
and not more
than 70 C.
185. The process of aspect No. 176, wherein said articles have an average
residence time in said thermalization zone of at least 2 minutes and not more
than 20
minutes.
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186. The process of aspect No. 176, wherein the residence time of said
articles in
said microwave chamber is at least 30 seconds and not more than 10 minutes.
187. The process of aspect No. 176, further comprising prior to said cooling
of
step (c), passing said heated articles through a holding zone, wherein the
temperature of
said articles is maintained at or above a specified minimum temperature for a
time period
of at least 2 minutes and not more than 15 minutes in said holding zone.
188. The process of aspect No. 187, wherein said specified minimum temperature
is at least 120 C and wherein said holding zone comprises a liquid-filled
chamber
operated at a pressure of at least 10 psig.
189. The process of aspect No. 176, wherein said microwave heating system is a
pressurized microwave system and pasteurizes and/or sterilizes said articles.
190. The process of aspect No. 189, wherein said articles comprise packages
containing foodstuffs, medical fluids, or medical instruments.
191. A microwave system for heating a plurality of articles, said system
comprising: a thermalization chamber for thermalizing said articles to a
substantially
uniform temperature; a microwave heating chamber disposed downstream of said
thermalization chamber for heating the thermalized articles, wherein said
microwave
heating chamber is configured to increase the average temperature of said
articles by at
least 50 C at a heating rate of at least 25 C per minute; a quench chamber
disposed
downstream of said microwave heating chamber for cooling the heated articles
to a lower
temperature; and at least one convey system configured to transport said
articles through
said thermalization chamber, said microwave heating chamber, and said quench
chamber,
wherein said microwave system is configured to achieve an overall production
rate of at
least 20 packages per minute per convey line.
192. The system of aspect No. 191, wherein said microwave heating chamber is
at
least partially defined within a pressurized microwave chamber.
193. The system of aspect No. 192, wherein said microwave chamber is a liquid-
filled microwave chamber.
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194. The system of aspect No. 191, further comprising at least one pair of
opposed microwave launchers disposed on generally opposite sides of said
microwave
chamber for discharging microwave energy into said microwave chamber.
195. The system of aspect No. 194, wherein said opposed launchers are
staggered
with respect to one another along the central axis of elongation of said
microwave
chamber.
196. The system of aspect No. 194, wherein said opposed launchers are
oppositely facing launchers.
197. The system of aspect No. 191, further comprising a holding chamber
disposed between said microwave heating chamber and said quench chamber for
maintaining the temperature of said heated articles above a minimum
temperature for at
least 2 minutes.
198. The system of aspect No. 197, wherein said holding chamber is at least
partially filled with a liquid medium.
199. The system of aspect No. 191 , further comprising a first pressure
adjustment
chamber respectively disposed between said thermalization chamber and said
microwave
heating chamber and a second pressure adjustment chamber disposed downstream
of said
quench chamber, wherein said first pressure adjustment chamber is configured
to
transition articles from said thermalization chamber into said microwave
heating chamber
and said second pressure adjustment chamber is configured to transition said
articles out
of said quench chamber, wherein said thermalization chamber is configured to
operate at
a different pressure than said microwave heating chamber and/or said quench
chamber.
200. The system of aspect No. 191, wherein said microwave system is configured
for the sterilization or pasteurization of foodstuffs, medical fluids, and/or
medical
instruments.
201. The system of aspect No. 191 , wherein said articles comprise packaged
foodstuffs, wherein said microwave chamber is configured to be water-filled
and
pressurized to at least 15 psig, wherein said microwave system is configured
to sterilize
said packaged foodstuffs at a rate of at least 25 packages per minute per
convey line.
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202. A process for heating a plurality of articles in a microwave heating
system,
said process comprising: (a) passing said articles through a pressurized
microwave
chamber via a conveyance system, wherein said microwave chamber is at least
partly
filled with a liquid medium; (b) generating microwave energy via one or more
microwave generators; (c) introducing at least a portion of said microwave
energy into
said microwave chamber via one or more microwave launchers; (d) heating said
articles
in said microwave chamber using at least a portion of said microwave energy
introduced
therein; and (e) during at least a portion of said heating of step (d),
agitating at least a
portion of said liquid medium within said microwave chamber, wherein said
agitating
includes discharging a plurality of fluid jets toward said articles at
multiple locations
within said microwave chamber.
203. The process of aspect No. 202, wherein said multiple locations are
axially
spaced along the central axis of elongation of said microwave chamber, wherein
at least a
portion of said jets are directed in a direction generally perpendicular to
said central axis
of elongation of said microwave chamber.
204. The process of aspect No. 202, wherein said multiple locations are
circumferentially spaced along the interior cross-section of said microwave
chamber,
wherein at least a portion of said jets are directed radially inwardly toward
the central
axis of elongation of said microwave chamber.
205. The process of aspect No. 202, wherein said heating of step (d) is
capable of
increasing the temperature of said articles by at least 50 C.
206. The process of aspect No. 202, wherein said heating of step (d) is
carried out
at a heating rate of least 25 C per minute.
207. The process of aspect No. 202, wherein said introducing of step (c)
includes
discharging microwave energy into said microwave chamber via at least one pair
of
axially spaced microwave launchers disposed on the same side of said microwave
chamber, wherein said agitating includes discharging said fluid jets from one
or more jet
manifolds disposed between axially adjacent microwave launchers.
208. The process of aspect No. 202, wherein the Reynolds number of each of
said
fluid jets introduced into said microwave chamber is at least 4500.
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209. The process of aspect No. 202, further comprising subsequent to said
heating
of step (d), passing the heated articles through a holding zone, wherein the
temperature of
said articles in said holding zone is maintained at or above a specified
minimum
temperature for a time period of at least 2 minutes and not more than 15
minutes.
210. The process of aspect No. 209, wherein said specified minimum temperature
is at least 120 C and wherein said holding zone has a pressure of at least 10
psig.
211. The process of aspect No. 202, further comprising, prior to said passing
of
step (a), thermalizing said articles in a thermalization zone to thereby
adjust the
temperature of said articles to a substantially uniform temperature, wherein
said
thermalized articles are passed through said microwave chamber in step (a).
212. The process of aspect No. 202, wherein said microwave chamber is at least
partially filled with a liquid medium comprising water and is pressurized to
at least 10
psig, wherein said microwave system sterilizes said articles at a rate of at
least 20
packages per minute per convey line.
213. The process of aspect No. 212, wherein said articles comprise packaged
foodstuffs, medical instruments, and/or medical fluids.
214. A process for heating a plurality of articles in a microwave heating
system,
said process comprising: (a) thermalizing said articles in a thermalization
chamber at
least partially filled with a liquid medium to thereby produced thermalized
articles having
a substantially uniform temperature; and (b) heating said thermalized articles
in a
microwave chamber, wherein said thermalizing of step (a) includes discharging
a
plurality of jets of said liquid medium toward said articles at multiple
locations within
said thermalization chamber.
215. The process of aspect No. 214, wherein said multiple locations are
axially
spaced along the central axis of elongation of said thermalization chamber,
wherein at
least a portion of said jets are directed in a direction generally
perpendicular to said
central axis of elongation of said thermalization chamber.
216. The process of aspect No. 214, wherein said multiple locations are
circumferentially spaced along the interior cross-section of said
thermalization chamber,
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wherein at least a portion of said jets are directed radially inwardly toward
the central
axis of elongation of said thermalization chamber.
217. The process of aspect No. 214, wherein said substantially uniform
temperature of said articles exiting said thermalization zone is at least 20 C
and not more
than 70 C.
218. The process of aspect No. 214, wherein said articles have an average
residence time of at least 2 minutes and not more than 20 minutes in said
thermalization
zone.
219. The process of aspect No. 214, wherein the Reynolds number of each of
said
jets introduced into said thermalization chamber is at least 4500.
220. The process of aspect No. 214, further comprising subsequent to said
heating
of step (b), passing the heated articles through a holding zone, wherein the
temperature of
said articles is maintained at or above a specified minimum temperature for a
time period
of at least 2 minutes and not more than 15 minutes within said holding zone.
221. The process of aspect No. 214, wherein said liquid medium in said
thermalization chamber comprises water.
222. The process of aspect No. 214, wherein said microwave chamber is at least
partially filled with said liquid medium.
223. The process of aspect No. 222, wherein said heating of step (b) includes
agitating at least a portion of said liquid medium within said microwave
chamber,
wherein said agitating includes discharging a plurality of fluid jets toward
said articles at
multiple locations within said microwave chamber.
224. The process of aspect No. 214, wherein said heating of step (b) is
carried out
to increase the average temperature of each article by at least 50 C, wherein
at least a
portion of said heating is carried out at a heating rate of at least 25 C per
minute.
225. The process of aspect No. 214, wherein said articles comprise foodstuffs,
medical fluids, and/or medical instruments.
226. The process of aspect No. 214, wherein said microwave chamber is a liquid-
filled chamber pressurized to at least 10 psig during at least a portion of
said heating of
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step (b), wherein said microwave system pasteurizes and/or sterilizes said
articles at a
rate of at least 20 packages per minute per convey line.
227. A method for heating a plurality of articles, said method comprising: (a)
heating a first test article in a small-scale microwave heating system while
conveying
said first test article through a water-filled, small-scale microwave chamber
having a total
internal volume of less than 50 cubic feet, wherein at least a portion of said
heating of
step (a) is accomplished using microwave energy; (b) determining a first
prescribed
heating profile based on said heating of step (a), wherein said prescribed
heating profile
comprises at least one value for one or more microwave system parameters
selected from
the group consisting of net power discharged into said chamber, sequential
microwave
power distribution, average temperature of the water in said microwave
chamber, flow
rate of the water in said microwave chamber, and residence time of said
article in said
microwave chamber; and (c) heating a plurality of first commercial articles in
a large-
scale microwave heating system while conveying said first commercial articles
through a
water-filled, large-scale microwave chamber having a total internal volume of
at least
250 cubic feet, wherein at least a portion of said heating of step (c) is
accomplished using
microwave energy, wherein each of said first commercial articles is
substantially similar
in size and composition to said first test article, wherein said heating of
step (c) is
controlled in accordance with said first prescribed heating profile determined
in step (b).
228. The method of aspect No. 227, wherein said heating of step (c) comprises
introducing said microwave energy into said large scale microwave chamber via
a
plurality of microwave launchers, wherein said first prescribed heating
profile specifies
the amount of microwave energy to be discharged by each launcher.
229. The method of aspect No. 227, wherein said first prescribed heating
profile
specifies a value for the average temperature of the water in said microwave
chamber,
wherein said value for the average temperature of the water is at least 120 C.
230. The method of aspect No. 227, wherein said first prescribed heating
profile
specifies a value for the residence time of said article in said microwave
chamber,
wherein said value for the residence time is at least 30 seconds and not more
than 20
minutes.
39
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231. The method of aspect No. 227, further comprising prior to step (c),
thennalizing at least a portion of said first commercial articles in a
thermalization zone to
a substantially uniform temperature, wherein at least a portion of said
thermalizing is
carried out according to said first prescribed heating profile determined in
step (b).
232. The method of aspect No. 231, further comprising subsequent to step (c),
passing said first commercial articles into a holding zone, wherein the
temperature of said
first commercial articles is maintained at or above a minimum temperature for
a specified
time period within said holding zone.
233. The method of aspect No. 232, wherein said minimum temperature is at
least
120 C and said specified time period is at least 2 minutes and not more than
20 minutes.
234. The method of aspect No. 227, further comprising repeating steps (a) and
(b)
with a second test article to thereby determine a second prescribed heating
profile,
repeating step (c) with a plurality of second commercial articles
substantially similar in
size and composition to said second test article, wherein said heating of said
second
commercial articles is carried in accordance with said second prescribed
heating profile.
235. The method of aspect No. 227, wherein said small-scale microwave heating
system is a batch system and said large-scale microwave heating system is a
continuous
system.
236. The method of aspect No. 227, wherein at least a portion of steps (a) and
(c)
are carried out with one or more automatic control systems.
237. The method of aspect No. 227, wherein said first test and commercial
articles
comprise packages containing foodstuffs, medical fluids, or medical
instruments.
238. The method of aspect No. 227, wherein said large-scale microwave heating
system is a sterilization system.
239. The method of aspect No. 227, wherein said large-scale microwave heating
system has an overall production rate of at least 20 packages per minute per
convey line.
240. The method of aspect No. 227, wherein said first commercial articles
comprise packaged foodstuffs, medical fluids, or medical instruments, wherein
said
large-scale microwave chamber is pressurized to at least 10 psig during at
least a portion
of said heating of step (c).
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241. The method of aspect No. 227, wherein said first commercial articles
comprise packaged foodstuffs, wherein said large-scale microwave chamber is
pressurized to at least 15 psig during at least a portion of said heating of
step (c), wherein
said large-scale microwave heating system is configured to sterilize said
packaged
foodstuffs at a rate of at least 20 packages per minute per convey line.
242. A locking gate device comprising: a pair of spaced apart fixed members
presenting opposing sealing surfaces and defining a gate-receiving space
between said
sealing surfaces, wherein each of said fixed members defines a flow-through
opening
circumscribed by one of said sealing surfaces, wherein said flow-through
openings are
substantially aligned with one another; and a gate assembly shiftable within
said gate-
receiving space between a closed position where said gate assembly
substantially blocks
said flow-through openings and an open position where said gate assembly does
not
substantially block said flow-through openings, wherein said gate assembly
comprises a
pair of spaced apart sealing plates and a drive member disposed between said
sealing
plates, wherein when said gate assembly is in said closed position said drive
member is
shiftable relative to said sealing plates between a retracted position and an
extended
position, wherein said gate assembly further comprises at least one pair of
bearings
disposed between said sealing plates, wherein shifting of said drive member
from said
retracted position to said extended position causes said bearings to force
said sealing
plates apart from one another and into a sealed position where said sealing
plates engage
said opposing sealing surfaces, wherein shifting of said drive member from
said extended
position to said retracted position allows said sealing plates to retract
towards one another
and into an unsealed position where said sealing plates are disengaged from
said
opposing sealing surfaces.
243. The device of aspect No. 242, wherein each of said sealing plates
comprising
a resilient seal member for engaging said sealing surfaces when said sealing
plate is in
said sealed position.
244. The device of aspect No. 242, wherein said sealing plates are biased
towards
said unsealed position.
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245. The device of aspect No. 244, wherein said gate assembly further
comprises
at least one spring for biasing said sealing plates towards said unsealed
position.
246. The device of aspect No. 242, wherein said gate assembly comprises at
least
3 pairs of bearings disposed between said sealing plates.
247. The device of aspect No. 242, wherein one of said pair of bearings is
disposed between said drive member and one of said sealing plates, said
sealing plate
further comprising a bearing slot extending along at least a portion of the
surface of said
sealing plate configured to permit contact between said one bearing and the
surface of
said sealing plate as said drive member moves within said gate receiving
space.
248. The device of aspect No. 247, wherein said bearing slot is a ramp
oriented at
an inclined angle.
249. The device of aspect No. 242, wherein one or more of said bearings is
physically coupled to said drive member and/or said at least one of said
sealing plates.
250. The device of aspect No. 249, wherein said drive member further comprises
at least one housing configured to receive one of said pair of bearings.
251. The device of aspect No. 242, wherein said locking gate device is
configured
for use in a pressurized chamber configured to be operated at a pressure of at
least 10
psig.
252. The device of aspect No. 242, wherein said locking gate device is
configured
for use in a liquid-filled chamber configured to be operated at a pressure of
at least 15
psig.
253. A method for moving one or more articles within a pressurized system,
said
method comprising: (a) passing one or more articles from a first pressurized
process zone
to a second pressurized process zone through a flow-through opening; (b)
shifting a pair
of movable plates into said opening; (c) moving said plates apart from one
another to
thereby seal said plates against a pair of opposed sealing surfaces that at
least partially
define said opening, wherein the pair of sealed plates substantially isolates
said first and
said second process zones from one another; (d) creating a pressure
differential of at least
15 psig across the pair of sealed plates; (e) depressuring at least one of
said first and
second process zones to equalize the pressure across the pair of sealed
plates; (f) moving
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said plates toward one another to thereby unseal said plates from said sealing
surfaces;
(g) shifting said pair of plates out of said opening; and (h) removing said
articles from
said second process zone back into said first process zone through said flow-
through
opening and/or inserting a new article into said second process zone through
said flow-
through opening.
254. The method of aspect No. 253, wherein at least a portion of said moving
of
said plates in step (c) is carried out by shifting a movable drive member
between said pair
of plates, wherein said drive member is coupled to at least one pair of
bearings that
contact and exert an outward pressure on said plates thereby moving said
plates in
opposite directions.
255. The method of aspect No. 253, wherein the plates are physically coupled
to
one another and biased in an unsealed position.
256. The method of aspect No. 253, further comprising, during said creating of
step (d) and/or said depressuring of step (e), moving the articles from said
second process
zone to a third process zone through a second flow-through opening, wherein
said
removing of step (h) includes inserting a new article into said second process
zone.
257. The method of aspect No. 256, wherein said third process zone has a
higher
pressure than said first process zone.
258. The method of aspect No. 257, wherein said creating of step (d) includes
opening a first equalization valve fluidly connecting said second process zone
and said
third process zone, wherein said depressuring of step (e) includes closing
said first
equalization valve and opening a second equalization valve fluidly connecting
said first
process zone and said second process zone.
259. The method of aspect No. 256, wherein said first process zone is a
thermalization zone, said second process zone is a pressure adjustment
chamber, and said
third process zone is a microwave heating zone, wherein said articles comprise
foodstuffs, medical fluids, or medical instruments.
260. The method of aspect No. 253, wherein said articles are processed in said
second processing zone and removed back into said first processing zone during
said
removing of step (h).
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261. The method of aspect No. 253, wherein said first and second process zones
are liquid-filled process zones.
262. A microwave heating system for heating a plurality of articles, said
microwave heating system comprising: a liquid-filled thermalization chamber; a
liquid-
filled microwave chamber, wherein said microwave chamber is configured to
operate at a
higher pressure than said thermalization chamber; and a pressure lock system
disposed
between said thermalization chamber and said microwave chamber, wherein said
pressure lock system comprises a pressure adjustment chamber, a first locking
gate valve,
and a second locking gate valve, wherein said first locking gate valve is
coupled between
said thermalization chamber and said pressure adjustment chamber, wherein said
second
locking gate valve is coupled between said pressure adjustment chamber and
said
microwave chamber.
263. The system of aspect No. 262, further comprising first and second
equilibration valves, wherein said first equilibration valve selectively
connects said
thermalization and pressure adjustment chambers, wherein said second
equilibration
valve selectively connects said microwave and pressure adjustment chambers.
264. The system of aspect No. 262, further comprising first and second check
valves respectively coupled to said first and second locking gate valves.
265. The system of aspect No. 262, further comprising a platform disposed in
said
pressure adjustment chamber and configured to support said articles.
266. The system of aspect No. 262, further comprising a thermalization convey
system and a microwave convey system, wherein said thermalization convey
system is
configured to convey said articles through said thermalization chamber toward
said
pressure adjustment chamber, wherein said microwave convey system is
configured to
convey said articles through said microwave chamber away from said pressure
adjustment chamber.
267. The system of aspect No. 266, further comprising an automatic article
transfer system comprising first and second article transfer devices, wherein
said first
article transfer device is configured to transfer said articles from said
thermalization
convey system, through said first locking gate valve, and into said pressure
adjustment
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chamber, wherein said second article transfer device is configured to transfer
said articles
from said pressure adjustment chamber, through said second locking gate valve,
and into
said microwave chamber.
268. The system of aspect No. 267, wherein at least a portion of said first
and/or
said second article transfer devices are configured to be stationary.
269. The system of aspect No. 267, wherein at least a portion of said first
and/or
said second article transfer devices are configured to extend and/or retract.
270. The system of aspect No. 269, wherein said first and/or said second
article
transfer devices are disposed within said pressure adjustment chamber and are
configured
to extend into said thermalization chamber and/or said microwave chamber to
transport
articles into and/or out of said pressure adjustment chamber.
271. The system of aspect No. 270, wherein said first and/or said second
article
transfer devices are disposed within said thermalization chamber and/or said
microwave
chamber and are configured to extend into said pressure adjustment chamber to
transport
articles into and/or out of said pressure adjustment chamber.
272. The system of aspect No. 267, further comprising an automatic control
system coupled to said first and second locking gate valves and said first and
second
article transfer systems, wherein said control system is programmed to control
said
locking gates and transfer systems to facilitate automatic transfer of said
articles from
said thermalization chamber to said microwave chamber via said pressure lock
system.
273. The system of aspect No. 272, further comprising first and second
equilibration valves, wherein said first equilibration valve selectively
connects said
thermalization and pressure adjustment chambers, wherein said second
equilibration
valve selectively connects said microwave and pressure adjustment chambers,
wherein
said control system is operably coupled to said first and second equilibration
valves,
wherein said control system is programmed to automatically open and close said
equilibration valves in coordination with the control of said article transfer
systems and
said gate valves to thereby facilitate pressure adjustment in said pressure
adjustment
chamber.
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274. The system of aspect No. 262, further comprising a liquid-filled holding
chamber configured to receive the heated articles exiting said liquid-filled
microwave
chamber and a liquid-filled quench zone configured to receive the articles
withdrawn
from the holding chamber.
275. The system of aspect No. 274, further comprising a second pressure lock
system comprising a second pressure adjustment chamber, a third locking gate
valve, and
a fourth locking gate valve, wherein said second pressure lock system has a
similar
configuration as said pressure lock system, wherein said second pressure lock
system is
disposed downstream of said holding zone.
276. The system of aspect No. 275, wherein said quench zone includes a high
pressure portion and a low pressure portion, wherein said third locking gate
valve is
coupled between said high pressure portion of said quench zone and said second
pressure
adjustment chamber and said fourth locking gate valve is coupled between said
pressure
adjustment chamber and said low pressure portion of said quench zone.
277. The system of aspect No. 276, wherein each of said high pressure portion
and said lower pressure portion of said quench zone are liquid-filled.
278. The system of aspect No. 262, wherein said thermalization chamber and/or
said microwave chamber are configured to be operated at a pressure of at least
15 psig.
279. The system of aspect No. 262, wherein said microwave heating system is
configured to pasteurize and/or sterilize said articles.
280. The system of aspect No. 279, wherein said articles comprise packaged
foodstuffs and said microwave heating system is configured to sterilize said
packaged
foodstuffs at a rate of at least 20 packages per minute per convey line.
281. A process for heating a plurality of articles in a microwave heating
system,
said process comprising: (a) passing a plurality of articles through a liquid-
filled
thennalization zone to thereby provide a plurality of thermalized articles;
(b) introducing
at least a portion of said thermalized articles into a pressure adjustment
zone, wherein
said pressure adjustment zone is at least partially defined between a first
and a second
locking gate valve, wherein said first locking gate valves is in a first open
position during
at least a portion of said introducing; (c) after said thermalized articles
have been
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introduced into said pressure adjustment zone, shifting said first locking
gate valve from
said first open position to a first closed position to thereby substantially
isolate said
pressure adjustment zone from said thermalization zone; (d) shifting said
second locking
gate valve from a second closed position to a second open position to allow
said articles
to be transferred from said pressure adjustment zone to a liquid-filled
microwave heating
zone; and (e) after said articles have been removed from said pressure
adjustment zone,
shifting said second locking gate valve from said second open position back to
said
second closed position to thereby re-isolate said pressure adjustment zone
from said
microwave heating zone.
282. The process of aspect No. 281, wherein the operating pressure of said
thermalization zone is lower than the operating pressure of said microwave
heating zone.
283. The process of aspect No. 281, wherein said introducing of step (b)
includes
shifting said first locking gate valve from said first closed position,
wherein said
thermalization zone and said pressure adjustment zone are substantially
isolated from one
another, to said first open position and transporting said articles through a
flow-through
opening defined within or by said first locking gate valve and into said
pressure
adjustment zone.
284. The process of aspect No. 281, further comprising prior to said shifting
of
step (c), opening a first equalization valve fluidly connecting said
thermalization zone
with said pressure adjustment zone and allowing the pressures of said
thermalization zone
and said pressure adjustment zone to substantially equalize before shifting
said first
locking gate valve into said first open position.
285. The process of aspect No. 284, further comprising prior to said shifting
of
step (d), opening a second equalization valve fluidly connecting said pressure
adjustment
zone and said microwave heating zone and allowing the pressure of said
pressure
adjustment zone and said microwave heating zone to substantially equalize
before
shifting said second locking gate valve into said second open position.
286. The process of aspect No. 285, further comprising closing said first
equalization valve after said shifting of said first locking gate valve in
step (c), but prior
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to opening said second equalization valve; and closing said second
equalization valve
after said shifting of step (e).
287. The process of aspect No. 281, wherein at least a portion of said
introducing
of step (b) is carried out using an automatic article transfer device.
288. The process of aspect No. 287, wherein at least a portion of said
automatic
article transfer device is disposed within said pressure adjustment zone,
wherein said
introducing of step (b) includes extending at least a portion of said
automatic article
transfer device from said pressure adjustment zone into said thermalization
zone and
withdrawing the extended portion of said article transfer device back into
said pressure
adjustment zone to introduce said articles therein.
289. The process of aspect No. 281, further comprising repeating steps (a)
through (e) with another plurality of articles.
290. The process of aspect No. 281, wherein said articles comprise a plurality
of
packaged foodstuffs, medical fluids, or medical instruments and wherein said
microwave
heating system has a production rate of at least 20 packages per convey line.
Brief Description of the Drawings
[027] FIG. la is process flow diagram depicting one embodiment of a microwave
heating system for heating one or more articles, particularly illustrating a
system
comprising a thermalization zone, a microwave heating zone, an optional
holding zone, a
quench zone, and a pair of pressure adjustment zones;
[028] FIG. lb is a schematic diagram of a microwave heating system 10
configured according to one embodiment of the present invention, particularly
each of the
zones of microwave heating system 10 outlined in the diagram provided in FIG.
la;
[029] FIG. 2a is a cross-sectional schematic end view of a process vessel
configured according to one embodiment of the present invention, particularly
illustrating
a conveyance system including a pair of convey lines arranged in a side-by-
side
configuration;
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[030] FIG. 2b is a schematic top cut-away view of the process vessel shown in
FIG. 2a, particularly illustrating the laterally-spaced arrangement of the
convey lines
relative to the convey axis extending through the vessel;
[031] FIG. 2c is a cross-sectional schematic end view of another process
vessel
configured according to another embodiment of the present invention,
particularly
illustrating a conveyance system including a pair of convey lines arranged in
a stacked
configuration;
[032] FIG. 2d is a schematic side cut-away view of the process vessel shown in
FIG. 2c, particularly illustrating the vertically-spaced arrangement of the
convey lines
relative to convey axis extending through the vessel;
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[033] FIG. 3 is a perspective view of a carrier according to one embodiment of
the
present invention configured to secure and transport the articles being heated
through a liquid-
filled process vessel;
[034] FIG. 4a is a partial side cut-away view of one embodiment of a microwave
heating
system that includes a pressure adjustment zone configured to transport one or
more articles
from the thermalization zone to the microwave heating zone of the heating
system using a
carrier transfer system;
[035] FIG. 4b is a partial side cut-away view of another embodiment of a
microwave
heating system including a pressure adjustment zone similar to the one
depicted in FIG. 4a, but
particularly illustrating a carrier transfer system disposed nearly entirely
within the pressure
adjustment zone;
[036] FIG. 4c is a partial schematic view of the pressure adjustment zone
similar to the
ones depicted in FIGS. 4a and 4b, but illustrating another embodiment of the
carrier transfer
system for moving the articles from the thermalization zone to the microwave
heating zone;
[037] FIG. 4d is a partial schematic view of the pressure adjustment zone
similar to the
ones depicted in FIGS. 4a and 4b, but illustrating yet another embodiment of
the carrier transfer
system for moving the articles from the thermalization zone to the microwave
heating zone;
[038] FIG. 5a is a partial side cut-away view of a locking gate device
configured
according to one embodiment of the present invention, particularly showing the
gate assembly
in an open position;
[039] FIG. 5b is a partial side cut-away view of the locking gate device
depicted in FIG.
5a, particularly showing the gate assembly in a closed position with the
sealing plates in a
retracted position;
[040] FIG. 5c is a partial side cut-away view of the locking gate device
depicted in FIGS.
5a and 5b, particularly showing the gate assembly in a closed position with
the sealing plates in
an extended position;
[041] FIG. 5d is an enlarged partial view of the gate assembly shown in FIGS.
5a-c,
particularly illustrating one embodiment of a bearing used to move the sealing
plates of the gate
assembly;
[042] FIG. 6a is a schematic partial side cut-away view of a microwave heating
zone
configured according to one embodiment of the present invention, particularly
illustrating the
heating vessel and the microwave distribution system;
CA 3130845 2021-09-10

[043] FIG. 6b is a schematic top view of a microwave heating zone configured
according
to one embodiment of the present invention, particularly illustrating one
configuration of
microwave launchers in a heating system employing a multi-line convey system;
[044] FIG. 6c is a schematic side view of the microwave heating zone
illustrated in FIG.
6b, particularly showing the one set of microwave launchers configured to heat
articles passing
along a convey line;
[045] FIG. 7a is a partial side cut-away view of a microwave heating zone
configured
according to one embodiment of the present invention, particularly
illustrating a titled microwave
launcher and showing what is meant by the term "launch tilt angle" (8);
[046] FIG. 7b is a partial side cut-away view of another embodiment of a
microwave
heating zone, particularly illustrating a microwave distribution system
comprising a plurality of
tilted launchers;
[047] FIG. 8a is a partial enlarged side cut-away view of a portion of a
microwave
heating zone, particularly illustrating one embodiment of a microwave window
located near the
discharge opening of at least one microwave launcher of the heating zone;
[048] FIG. 8b is a partial enlarged side cut-away view of a portion of a
microwave
heating zone, particularly illustrating another embodiment of a microwave
window located near
the discharge opening of at least one microwave launcher of the heating zone;
[049] FIG. 8c is a partial enlarged side cut-away view of a portion of a
microwave
heating zone, particularly illustrating yet another embodiment of a microwave
window located
near the discharge opening of at least one microwave launcher of the heating
zone;
[050] FIG. 9a is an isometric view of a microwave launcher configured
according to one
embodiment of the present invention;
[051] FIG. 9b is a longitudinal side view of the microwave launcher depicted
in FIG. 9a;
[052] FIG. 9c is an end view of the microwave launcher depicted in FIGS. 9a
and 9b,
particularly illustrating a launcher having a flared outlet;
[053] FIG. 9d is an end view of another embodiment of the microwave launcher
generally depicted in FIGS. 9a and 9b, particularly illustrating a launcher
having an inlet and
outlet of approximately the same size;
[054] FIG. 9e is an end view of yet another embodiment of the microwave
launchers
generally depicted in FIGS. 9a and 9b, particularly illustrating a launcher
having a tapered
outlet;
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[055] FIG. 10a is an isometric view of another microwave launcher configured
according
to one embodiment of the present invention, particularly illustrating a
launcher comprising a
single microwave inlet and a plurality of microwave outlets;
[056] FIG. 10b is a vertical cross-sectional view of the microwave launcher
depicted in
FIG. 10a, particularly illustrating the multiple microwave outlets;
[057] FIG. 10c is a vertical cross-sectional view of the microwave launcher
depicted in
FIGS. 10a and 10b, particularly showing the pair of dividing septa used to
create individual
microwave pathways between the inlet and multiple outlets of the microwave
launcher;
[058] FIG. 11a is an isometric view of a microwave launcher configured
according to yet
another embodiment of the present invention, particularly showing an
integrated inductive iris
disposed between the inlet and outlet of the launcher;
[059] FIG. 11b is a horizontal cross-sectional view of the microwave launcher
depicted
in FIG. 11a;
[060] FIG. 11c is a horizontal cross-sectional view of another microwave
launcher
similar to the launcher depicted in FIG. 11a, but including a pair of dividing
septa in addition to
an inductive iris disposed between the inlet and outlet of the launcher;
[061] FIG. 12a is a side cut-away view of a phase shifting device configured
according
to one embodiment of the present invention, particularly illustrating a
plunger-type tuning device
that includes a single plunger;
[062] FIG. 12b is a schematic side cut-away view of a phase shifting device
configured
according to another embodiment of the present invention, particularly
illustrating a plunger-type
tuning device including a plurality of plungers driven by a common rotatable
shaft;
[063] FIG. 13a is a side perspective view of a phase shifting device
configured
according to yet another embodiment of the present invention, particularly
illustrating a rotatable
phase shifting device;
[064] FIG. 13b is a longitudinal cross-sectional view of the rotatable phase
shifting
device depicted in FIG. 13a;
[065] FIG. 13c is a lateral cross-sectional view of the rotatable section of
the rotatable
phase shifting device depicted in FIGS. 13a and 13b, particularly showing the
width and spacing
of the plates disposed within the housing;
[066] FIG. 13d is an lateral cross-sectional view of the fixed section of the
rotatable
phase shifting device depicted in FIGS. 13a and 13b, particularly illustrating
the dimensions of
the fixed section;
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[067] FIG. 13e is a side cut-away view of a rotatable phase shifting device
configured
according to another embodiment of the present invention, particularly
illustrating a drive system
that includes a rotating crank member;
[068] FIG. 13f is a side cut-away view of a rotatable phase shifting device
configured
according to yet another embodiment of the present invention, particularly
illustrating a drive
system that includes a set of compression springs;
[069] FIG. 14a is a schematic partial side cut-away view of a microwave
distribution
system utilizing two phase shifting devices for phase shifting and/or
impedance tuning;
[070] FIG. 14b is a schematic partial side cut-away view of a microwave
heating vessel
configured according to one embodiment of the present invention, particularly
illustrating a
phase shifting device coupled to the vessel for use as a frequency tuner;
[071] FIG. 15a is a schematic partial side cut-away view of a portion of a
microwave
heating system, particularly illustrating a thermalization zone including a
plurality of fluid jet
agitators;
[072] FIG. 15b is an end view of a thermalization zone similar to the one
depicted in
FIG. 15a, particularly illustrating one embodiment wherein the fluid jet
agitator is
circumferentially-positioned within the thermalization zone;
[073] FIG. 16 is a flowchart representing the major steps involved in a method
of
controlling a microwave system in accordance with one embodiment of the
present invention;
[074] FIG. 17 is a flowchart representing the major steps involved in a method
for
determining the net power discharged from at least one microwave launcher
using two or more
pairs of directional couplers; and
[075] FIG. 18 is an isometric depiction of the location of thermocouples
inserted into a
test package to determine the minimum temperature of the package for
determining the heating
profile for an article according to one embodiment of the present invention.
Detailed Description
[076] Microwave processes and systems for heating a plurality of articles
according to
various embodiments of the present invention are described below. Examples of
suitable
articles to be heated in systems and processes of the present invention can
include, but are not
limited to, foodstuffs, medical fluids, and medical instruments. In one
embodiment, microwave
systems described herein can be used for the pasteurization and/or
sterilization of the articles
being heated. In general, pasteurization involves rapid heating of an article
or articles to a
minimum temperature between 80 C and 100 C, while sterilization involves
heating one or more
articles to a minimum temperature between 100 C to 140 C. However, in one
embodiment,
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pasteurization and sterilization may take place simultaneously or nearly
simultaneously and
many processes and systems can be configured to both pasteurize and sterilize
one or more
articles. Various embodiments of microwave systems and processes configured to
heat one or
more types of articles will now be discussed in detail, with reference to the
Figures.
[077] Turning now to FIGS. la and lb, a schematic representation of the major
steps in
a microwave heating process according to one embodiment of the present
invention is depicted
in FIG. la, while FIG. lb depicts one embodiment of a microwave system 10
operable to heat a
plurality of articles according to the process outlined in FIG. 1 a. As shown
in FIGS. la and 1 b,
one or more articles can initially be introduced into a thermalization zone
12, wherein the
articles can be thermalized to a substantially uniform temperature. Once
thermalized, the
articles can then be optionally passed through a pressure adjustment zone 14a
before being
introduced into a microwave heating zone 16. In microwave heating zone 16, the
articles can
be rapidly heated using microwave energy discharged into at least a portion of
the heating zone
by one or more microwave launchers, generally illustrated as launchers 18 in
FIG. lb. The
heated articles can then optionally be passed through a holding zone 20,
wherein the articles
can be maintained at a constant temperature for a specified amount of time.
Subsequently, the
articles can then be passed to a quench zone 22, wherein the temperature of
the articles can be
quickly reduced to a suitable handling temperature. Thereafter, the cooled
articles can
optionally be passed through a second pressure adjustment zone 14b before
being removed
from system 10 and further utilized.
[078] Microwave system 10 can be configured to heat many different types of
articles.
In one embodiment, the articles heated in microwave system 10 can comprise
foodstuffs, such
as, for example, fruits, vegetables, meats, pastas, pre-made meals, and even
beverages. In
other embodiments, the articles heated in microwave system 10 can comprise
packaged
medical fluids or medical and/or dental instruments. The articles processed
within microwave
heating system 10 can be of any suitable size and shape. In one embodiment,
each article can
have a length (longest dimension) of at least about 2 inches, at least about 4
inches, at least
about 6 inches and/or not more than about 18 inches, not more than about 12
inches, or not
more than about 10 inches; a width (second longest dimension) of at least
about 1 inch, at least
about 2 inches, at least about 4 inches and/or not more than about 12 inches,
not more than
about 10 inches, or not more than about 8 inches; and/or a depth (shortest
dimension) of at
least about 0.5 inches, at least about 1 inch, at least about 2 inches and/or
not more than about
8 inches, not more than about 6 inches, or not more than about 4 inches. The
articles can
comprise individual items or packages having a generally rectangular or prism-
like shape or can
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comprise a continuous web of connected items or packages passed through
microwave system
10. The items or packages may be constructed of any material, including
plastics, cellulosics,
and other microwave-transparent materials, and can be passed through microwave
system 10
via one or more conveyance systems, embodiments of which will be discussed in
detail below.
[079] According to one embodiment of the present invention, each of the above-
described thermalization, microwave heating, holding, and/or quench zones 12,
16, 20, and 22
can be defined within a single vessel, as generally depicted in FIG. lb,
while, in another
embodiment, at least one of the above-described stages can be defined within
one or more
separate vessels, According to one embodiment, at least one of the above-
described steps can
be carried out in a vessel that is at least partially filled with a fluid
medium in which the articles
being processed can be at least partially submerged. The fluid medium can be a
gas or a liquid
having a dielectric constant greater than the dielectric constant of air and,
in one embodiment,
can be a liquid medium having a dielectric constant similar to the dielectric
constant of the
articles being processed. Water (or liquid media comprising water) may be
particularly suitable
for systems used to heat edible and/or medical devices or articles. In one
embodiment,
additives, such as, for example, oils, alcohols, glycols, and salts may
optionally be added to the
liquid medium to alter or enhance its physical properties (e.g., boiling
point) during processing, if
needed.
[080] Microwave system 10 can include at least one conveyance system (not
shown in
FIGS. la and 1 b) for transporting the articles through one or more of the
processing zones
described above. Examples of suitable conveyance systems can include, but are
not limited to,
plastic or rubber belt conveyors, chain conveyors, roller conveyors, flexible
or multiflexing
conveyors, wire mesh conveyors, bucket conveyors, pneumatic conveyors, screw
conveyors,
trough or vibrating conveyors, and combinations thereof. The conveyance system
can include
any number of individual convey lines and can be arranged in any suitable
manner within the
process vessels. The conveyance system utilized by microwave system 10 can be
configured
in a generally fixed position within the vessel or at least a portion of the
system can be
adjustable in a lateral or vertical direction.
[081] Turning now to FIGS. 2a-2d, embodiments of a process vessel 120 that
includes a
conveyance system 110 disposed therein are provided. In one embodiment
generally depicted
in FIGS. 2a and 2b, conveyance system 110 includes a pair of laterally spaced,
substantially
parallel convey lines 112, 114 positioned in a generally side-by-side
configuration within vessel
120. As shown in the top, cut-away view of vessel 120 in FIG. 2b, convey lines
112 and 114
may be laterally spaced from each other and may be positioned on both sides of
a convey axis
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122, which extends along the length of vessel 120 in the direction of
conveyance of the articles
passing therethrough. Although shown in FIG. 2a as being at generally the same
vertical
elevation within vessel 120, it should be understood that, in one embodiment,
convey lines 112,
114 may also be positioned at different vertical elevations. Additionally,
conveyance system
110 depicted in FIGS. 2a and 2b may also include multiple pairs of laterally
spaced convey lines
(embodiment not shown), such that the pairs of laterally spaced convey lines
are vertically
spaced from each other along the vertical dimension of vessel 120.
[082] Another embodiment of a conveyance system 110 that includes a pair of
vertically-spaced, substantially parallel convey lines 116, 118 positioned in
a stacked
arrangement within the interior of vessel 120, is shown in FIGS. 2c and 2d.
Convey lines 116
and 118 may be configured above and below convey axis 122, which may generally
extend
along the length of vessel 120, as shown in the cutaway side view of vessel
120 provided in
FIG. 2d. Additionally, in a similar manner as previously described, vessel 120
shown in FIGS.
2c and 2d may also include multiple pairs of convey lines, laterally spaced
from one another
within the vessel. Further, each convey line of the pair may or may not be
offset from the other
in a lateral direction. In a further embodiment (not shown), vessel 120 may
include a single
convey line, positioned in the middle one-third of the internal volume of
vessel 120, or
positioned at or near the centerline of the vessel. Additional details of
conveyance systems
according to several embodiments of the present invention will be discussed in
detail below.
[083] When a conveyance system is used to transport articles through a liquid-
filled
process vessel, one or more carriers or other securing mechanisms can be used
to control the
position of the articles during passage through the liquid medium. One
embodiment of a
suitable carrier 210 is illustrated in FIG. 3. As shown in FIG. 3, carrier 210
comprises a lower
securing surface 212a and an upper securing surface 212b configured to secure
any suitable
number of articles 216 therebetween. In one embodiment, upper and/or lower
surfaces 212b,a
can have a meshed, grid, or grated structure, as generally depicted in FIG. 3,
while, in another
embodiment, one or both surfaces 212a,b can be a substantially continuous
surface. Carrier
210 can be constructed of plastic, fiberglass, or any other dielectric
material and, in one
embodiment, may be made of one or more microwave-compatible and/or microwave-
transparent materials. In some embodiments, the material may be a lossy
material. In some
embodiments, carrier 210 can comprise substantially no metal.
[084] Lower and upper securing surfaces 212a, 212b may be attached to one
another
by a securing device, shown as a fastener 219 in FIG. 3, and, as assembled,
carrier 210 may be
attached or secured to the conveyance system (not shown in FIG. 3) according
to any suitable
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attachment mechanism. In one embodiment, at least one side (or edge) of
carrier 210 can
include one or more attachment mechanisms, such as, for example, upper and
lower hooks
218a, 218b shown in FIG. 3, for securing carrier 210 to a portion (e.g., a
bar, a rail, a belt, or a
chain) of the conveyance system (not shown). Depending on the thickness and/or
weight of
articles 216, carrier 210 may only include one of hooks 218a, 218b for
securing carrier 210 onto
the conveyance system. The conveyance system used to transport articles 216
may be
configured to transport multiple carriers along one or more conveyance lines
and the carriers
may be arranged in a side-by-side, laterally-spaced configuration and/or in a
vertically-spaced,
stacked configuration as described previously. When the conveyance system
includes a
plurality of convey lines, each convey line may include a single carrier for
holding a plurality of
articles 216, or each convey line may hold multiple carriers stacked or
laterally spaced from
each other.
[085] Referring back to FIGS. la and 1 b, the articles introduced into
microwave system
are initially introduced into thermalization zone 12, wherein the articles are
thermalized to
achieve a substantially uniform temperature. In one embodiment, at least about
85 percent, at
least about 90 percent, at least about 95 percent, at least about 97 percent,
or at least about 99
percent of all the articles withdrawn from thermalization zone 12 have a
temperature within
about 5 C, within about 2 C, or within 1 C of one another. As used herein, the
terms
"thermalize" and "thermalization" generally refer to a step of temperature
equilibration or
equalization. Depending on the initial and desired temperature of the articles
being thermalized,
the temperature control system of thermalization zone 12, illustrated in FIG.
la as heat
exchanger 13, can be a heating and/or cooling system. In one embodiment, the
thermalization
step can be carried out under ambient temperature and/or pressure, while, in
another
embodiment, thermalization can be carried out in a pressurized and/or liquid-
filled thermalization
vessel at a pressure of not more than about 10 psig, not more than about 5
psig, or not more
than about 2 psig. Articles undergoing thermalization can have an average
residence time in
thermalization zone 12 of at least about 30 seconds, at least about 1 minute,
at least about 2
minutes, at least about 4 minutes and/or not more than about 20 minutes, not
more than about
minutes, or not more than about 10 minutes. In one embodiment, the articles
withdrawn
from thermalization zone 12 can have a temperature of at least about 20 C, at
least about 25 C,
at least about 30 C, at least about 35 C and/or not more than about 70 C, not
more than about
65 C, not more than about 60 C, or not more than about 55 C.
[086] In one embodiment wherein thermalization zone 12 and microwave heating
zone
16 are operated at substantially different pressures, the articles removed
from thermalization
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zone 12 can first be passed through a pressure adjustment zone 14a before
entering microwave
heating zone 16, as generally depicted in FIGS. la and lb. Pressure adjustment
zone 14a can
be any zone or system configured to transition the articles being heated
between an area of
lower pressure and an area of higher pressure. In one embodiment, pressure
adjustment zone
14a can be configured to transition the articles between two zones having a
pressure difference
of at least about 1 psi, at least about 5 psi, at least about 10 psi and/or
not more than about 50
psi, not more than about 45 psi, not more than about 40 psi, or not more than
about 35 psi. In
one embodiment, microwave system 10 can include at least two pressure
adjustment zones
14a,b to transition the articles from an atmospheric pressure thermalization
zone to a heating
zone operated at an elevated pressure before returning the articles back to
atmospheric
pressure, as described in detail below.
[087] One embodiment of a pressure adjustment zone 314a disposed between a
thermalization zone 312 and a microwave heating zone 316 of a microwave
heating system 310
is illustrated in FIG. 4a. Pressure adjustment zone 314a is configured to
transition a plurality of
articles 350, which may be secured within at least one carrier, from lower-
pressure
thermalization zone 312 to higher-pressure microwave heating zone 316.
Although shown in
FIG. 4a as being a single carrier 352a, it should be understood that pressure
adjustment zone
314a may be configured to receive more than one carriers. In one embodiment,
the carriers
may be received simultaneously, such that pressure adjustment zone 314a
contains multiple
carriers at one time. In another embodiment, multiple carriers may be lined up
and ready, for
example within thermalization zone 312, for being transitioned through
pressure adjustment
zone 314a, details of which will now be discussed below.
[088] In operation, one or more carriers 352a can be transitioned from
thermalization
zone 312 to microwave heating zone 316 by first opening an equilibration valve
330 and
allowing the pressure between thermalization zone 312 and pressure adjustment
zone 314a to
equalize. Next, a gate device 332 can be opened to allow carrier 352a to be
moved from a
convey line 340a disposed within thermalization zone 312 onto a platform 334
within pressure
adjustment zone 314a, as generally shown by the dashed-line carrier 352b in
FIG. 4a.
[089] Thereafter, gate device 332 and equilibrium valve 330 can be closed in
sequence,
re-isolating pressure adjustment zone 314a from thermalization zone 312.
Subsequently,
another equilibration valve 336 can be opened to allow the pressure between
pressure
adjustment zone 314a and microwave heating zone 316 to equalize. Once
equilibrium is
achieved, another gate device 338 can be opened to permit carrier 352b to be
moved onto
another conveyance system 340b disposed within microwave heating zone 316, as
generally
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shown by dashed-line carrier 352c in FIG. 4a. Subsequently, gate device 338
and equalization
valve 336 may be closed in sequence, re-isolating microwave heating zone 316
from pressure
adjustment zone 314a. The process may then be repeated to transport additional
carriers from
thermalization zone 312 to microwave heating zone 316 as needed.
[090] According to one embodiment, each of microwave heating zone 316 and
thermalization zone 312 can be filled with a non-compressible fluid or liquid,
such as, for
example, water or solutions including water. As used herein, the term "filled"
denotes a
configuration where at least 50 percent of the specified volume is filled with
the filling medium.
The "filling medium" can be a liquid, typically an incompressible liquid, and
may be or include,
for example, water. In certain embodiments, "filled" volumes can be at least
about 75 percent,
at least about 90 percent, at least about 95 percent, or 100 percent full of
the filling medium.
When thermalization zone 312 and/or microwave heating zone 316 are filled with
an
incompressible fluid, gate devices 332, 338 and/or pressure adjustment zone
314a may also
include two or more one-way flaps or valves, shown as valves or flaps 342, 344
in FIG. 4a, for
preventing substantial fluid leakage between thermalization zone 312 and
microwave heating
zone 316 when gate devices 332 and 338 are open and carrier 352 is passed
therethrough.
[091] The transportation of carrier 352 from thermalization zone 312 through
pressure
adjustment zone 314a and into microwave heating zone 316 can be accomplished
via one or
more automatic article transfer systems, several embodiments of which are
illustrated in FIGS.
4b-4d. In some embodiments, automatic transfer system 380 can include one or
more transfer
devices, disposed within thermalization zone 312, pressure adjustment zone
314a, and/or
microwave heating zone 316 for moving carrier 352 into and/or out of pressure
adjustment zone
314a. In one embodiment shown in FIG. 4b, transfer system 380 includes two
gear transfer
devices 381, 382 configured to engage teeth 353 disposed along the lower edge
of carrier 352
and rotate, as indicated by the arrows 392a,b, to pull carrier 352 into out of
thermalization zone
312 and/or push carrier 352 into microwave heating zone 316. As shown in FIG.
4b, first and
second gear transfer devices 381, 382 remain substantially stationary (in
terms of lateral
motion) during the transportation of carrier 352 and are nearly entirely, or
entirely, disposed
within pressure adjustment zone 314a.
[092] In contrast, some embodiments of automatic transfer system 380 can
include one
or more transfer devices that are laterally shiftable (i.e., movable in the
direction of transport)
during transport of carrier 352 into and/or out of pressurize adjustment zone
314a. As depicted
in one embodiment shown in FIG. 4c, a portion of the automatic transfer system
380 may be
disposed in thermalization zone 312 and/or microwave heating zone 316 and can
be configured
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for extension into and retraction out of pressure adjustment zone 314a. In the
system 380
shown in FIG. 4c, the transfer devices include a pusher arm 381 configured to
push carrier 352
into pressure adjustment zone 314a and a puller arm 382 for pulling carrier
352 into microwave
heating zone 316. Neither pusher arm 381 nor puller arm 382 are disposed
within pressure
adjustment zone 314a, but instead, each is configured to extend into and
retract out of pressure
adjustment zone 314a, as generally shown by arrows 394a,b in FIG. 4c.
[093] According to another embodiment depicted in FIG. 4d, automatic transport
system
380 includes a platform 334 having a movable portion 384, which is configured
to be extended
into and retracted out of thermalization 312 and/or microwave heating zone 316
to thereby
transport carrier 352 into and out of thermalization and microwave heating
zones 312, 316, as
generally shown by arrows 396a and 396b. In contrast to the embodiment shown
in FIG. 4c,
automatic transfer system 380 depicted in FIG. 4d is primarily disposed within
pressure
adjustment zone 314a and is configured to extend out of and retract back into
pressure
adjustment zone 314a.
[094] Regardless of the specific configuration of the transfer devices
utilized by
automatic article transfer system 380, the transfer system can be automated,
or controlled, by
an automatic control system 390, as illustrated in FIGS. 4a and 4b. Although
not specifically
depicted in the embodiments illustrated in FIGS. 4c and 4d, it should be
understood that such
control systems 390 may also be employed in these embodiments. Automatic
control system
390 can be used to control the motion and/or timing of at least one of first
and second
equilibration valves 330, 336, first and second gate valves 332, 338, and
first and second
transfer devices 381, 382 of the automatic article transfer system 380. In one
embodiment,
control system 390 can adjust the position, speed, and/or timing of these
devices or elements in
order to ensure that the carriers within the system move in an uninterrupted
and consistent
manner.
[095] Turning now to FIGS. 5a-5d, one embodiment of a locking gate device 420,
suitable for use as gate device 332 and/or 338 in the portion of microwave
system 310 depicted
in FIGS. 4a and 4b, is provided. Locking gate valve device 420 is illustrated
in FIGS. 5a-d as
generally comprising a pair of spaced apart fixed members 410, 412 that
present opposing
sealing surfaces 414a,b and that define a gate-receiving space 416
therebetween. The spaced
apart fixed members 410, 412 can each define a flow-through opening 418a,b,
which are
circumscribed by one of sealing surfaces 414a,b. Each of flow-through openings
418a,b are
substantially aligned with one another such that the articles can pass through
the cumulative
opening when gate valve device 420 is open.
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[096] Locking gate device 420 further comprises a gate assembly 422, which is
configured to be received within gate-receiving space 416 and is shiftable
therein between a
closed position (as shown in FIGS. 5b and 5c), wherein gate assembly 422
substantially blocks
flow-through openings 418a,b, and an open position (as shown in FIG. 5a),
wherein gate
assembly 422 does not substantially block flow-through openings 418a,b. In one
embodiment,
gate assembly 422 comprises a pair of spaced apart sealing plates 424, 426 and
a drive
member 428 disposed between sealing plates 424, 426. When gate assembly 422 is
configured in the closed position, drive member 428 is shiftable, relative to
sealing plates 424,
426, between a retracted position (as shown in FIG. 5b) and an extended
position (as shown in
FIG. 5c). In one embodiment shown in FIGS. 5a-c, gate assembly 422 comprises
at least one
pair of bearings 430 disposed within the space defined between opposing
sealing plates 424,
426, which is positioned in gate receiving space 416 when gate assembly 422 is
in a closed
position, as particularly shown in FIGS. 5b and 5c. When drive member 428 is
shifted between
a retracted position as illustrated in FIG. 5b to an extended position as
depicted in FIG. 5c, at
least one bearing of pair 430 can force at least one of sealing plates 424,
426 outwardly, away
from one another and into a sealed position, as shown in FIGS. 5c.
[097] In one embodiment, one or more of the bearings of pair 430 can be
secured,
attached, or at least partially housed within at least one of sealing plates
424, 426 and/or drive
member 428. According to one embodiment, at least one of the bearings 430 a
can be fixedly
attached to drive member 428, as depicted in the enlarged partial view of gate
assembly 422
provided in FIG. 5d. As drive member 428 shifts downwardly into gate receiving
space 416, one
of the bearings 430a from the pair can contact one of sealing plates 424, 426
(shown as plate
426 in FIG. 5d) and can move along a ramp (or slot) 427 therein. As the
bearing travels through
the slot 427 (or along the ramp 427), outward pressure is exerted on sealing
plate 426, thereby
moving it in a direction as indicated by arrow 460. Although shown as
including only a single
pair of bearings 430, it should be understood that any number of bearings,
positioned along the
vertical length of drive member 428 and/or sealing members 424, 426 can be
used.
[098] When in a sealed position, as shown in FIG. 5c, at least a portion of
sealing plates
424, 426 engage or physically contact respective opposing sealing surface
414a,b, to thereby
form a substantially fluid tight seal. In one embodiment, each of sealing
plates 424, 426
comprises a resilient seal 423, 425 for engaging sealing surfaces 414a,b when
sealing plates
424, 426 are in the sealed position. When drive member 428 is shifted from the
extended
position, as shown in FIG. 5c, back to the retracted position, as shown in
FIG. 5b, sealing plates
424, 426 retract towards one another into the unsealed position, as shown in
FIG. 5b. In the
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unsealed position, sealing plates 424, 426 are disengaged from opposing
sealing surfaces
414a,b, but may remain disposed within gate receiving space 416. In one
embodiment, sealing
plates 424, 426 can be biased towards the unsealed position and can include at
least one
biasing device 429 (e.g., a spring or springs) for biasing sealing plates 424,
426 toward the
unsealed position.
[099] Referring again to FIGS. la and lb, the articles exiting thermalization
zone 12,
and optionally passed through pressure adjustment zone 14a, as described
above, can then be
Introduced into microwave heating zone 16. In microwave heating zone 16, the
articles can be
rapidly heated with a heating source that uses microwave energy. As used
herein, the term
"microwave energy" refers to electromagnetic energy having a frequency between
300MHz and
30 GHz. In one embodiment, various configurations of microwave heating zone 16
can utilize
microwave energy having a frequency of about 915 MHz or a frequency of about
2.45 GHz,
both of which have been generally designated as industrial microwave
frequencies. In addition
to microwave energy, microwave heating zone 16 may optionally utilize one or
more other heat
sources such as, for example, conductive or convective heating or other
conventional heating
methods or devices. However, at least about 85 percent, at least about 90
percent, at least
about 95 percent, or substantially all of the energy used to heat the articles
within microwave
heating zone 16 can be microwave energy from a microwave source.
[0100] According to one embodiment, microwave heating zone 16 can be
configured to
increase the temperature of the articles above a minimum threshold
temperature. In one
embodiment wherein microwave system 10 is configured to sterilize a plurality
of articles, the
minimum threshold temperature (and operating temperature of microwave heating
zone 16) can
be at least about 120 C, at least about 121 C, at least about 122 C and/or not
more than about
130 C, not more than about 128 C, or not more than about 126 C. Microwave
heating zone 16
can be operated at approximately ambient pressure, or it can include one or
more pressurized
microwave chambers operated at a pressure of at least about 5 psig, at least
about 10 psig, at
least about 15 psig and/or not more than about BO psig, not more than about 60
psig, or not
more than about 40 psig. In one embodiment, the pressurized microwave chamber
can be a
liquid-filled chamber having an operating pressure such that the articles
being heated can reach
a temperature above the normal boiling point of the liquid medium employed
therein.
[0101] The articles passing through microwave heating zone 16 can be heated to
the
desired temperature in a relatively short period of time, which, in some
cases, may minimize
damage or degradation of the articles. In one embodiment, the articles passed
through
microwave heating zone 16 can have an average residence time of at least about
5 seconds, at
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least about 20 seconds, at least about 60 seconds and/or not more than about
10 minutes, not
more than about 8 minutes, or not more than about 5 minutes. In the same or
other
embodiments, microwave heating zone 16 can be configured to increase the
average
temperature of the articles being heated by at least about 20 C, at least
about 30 C, at least
about 40 C, at least about 50 C, at least about 75 C and/or not more than
about 150 C, not
more than about 125 C, or not more than about 100 C, at a heating rate of at
least about 15 C
per minute ( C/min), at least about 25 C/min, at least about 35 C/min and/or
not more than
about 75 C/min, not more than about 50 C/min, or not more than about 40 C/min.
[0102] Turning now to FIG. 6a, one embodiment of a microwave heating zone 516
is
illustrated as generally comprising a microwave heating chamber 520, at least
one microwave
generator 512 for generating microwave energy and a microwave distribution
system 514 for
directing at least a portion of the microwave energy from generator 512 to
microwave chamber
520. Microwave distribution system 514 comprises a plurality of waveguide
segments 518 and
one or more microwave launchers, shown as launchers 522a-f in FIG. 6a, for
discharging
microwave energy into the interior of microwave chamber 520. As shown in FIG.
6a, microwave
heating zone 516 can further comprise a conveyance system 540 for transporting
articles 550 to
be heated through microwave chamber 520. Each of the components of microwave
heating
zone 516, according to various embodiments of the present invention, are now
discussed in
detail immediately below.
[0103] Microwave generator 512 can be any suitable device for generating
microwave
energy of a desired wavelength (ik). Examples of suitable types of microwave
generators can
include, but are not limited to, magnetrons, klystrons, traveling wave tubes,
and gyrotrons.
Although illustrated in FIG. 6a as including a single generator 512, it should
be understood that
microwave heating system 516 can include any number of generators arranged in
any suitable
configuration. For example, in one embodiment, microwave heating zone 516 can
include at
least 1, at least 2, at least 3 and/or not more than 5, not more than 4, or
not more than 3
microwave generators, depending on the size and arrangement of microwave
distribution
system 514. Specific embodiments of a microwave heating zone including
multiple generators
will be discussed in detail below.
[0104] Microwave chamber 520 can be any chamber or vessel configured to
receive a
plurality of articles. Microwave chamber 520 can be of any size and may have
one of a variety
of different cross-sectional shapes. For example, in one embodiment, chamber
520 can have a
generally circular or elliptical cross-section, while, in other embodiments,
can have a generally
square, rectangular, or polygonal cross-sectional shape. In one embodiment,
microwave
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chamber 520 can be a pressurized chamber and, in the same or other
embodiments, can be
configured to be at least partially filled with a liquid medium (a liquid-
filled chamber). Microwave
chamber 520 can also be configured to receive at least a portion of the
microwave energy
discharged from one or more microwave launchers 522 and, in one embodiment,
can be
configured to permit the creation of a stable (or standing) wave pattern
therein. In one
embodiment, at least one dimension of microwave chamber 520 can be at least
about 0.30A, at
least about 0.40A, or at least about 0.50A, wherein A is the wavelength of the
microwave energy
discharged therein.
[0105] Microwave distribution system 514 comprises a plurality of waveguides
or
waveguide segments 518 for directing at least a portion of the microwave
energy from generator
512 to microwave chamber 520. Waveguides 518 can be designed and constructed
to
propagate microwave energy in a specific predominant mode, which may be the
same as or
different than the mode of the microwave energy generated by generator 512. As
used herein,
the term "mode" refers to a generally fixed cross-sectional field pattern of
microwave energy. In
one embodiment of the present invention, waveguides 518 can be configured to
propagate
microwave energy in a TExy mode, wherein x and y are integers in the range of
from 0 to 5. In
another embodiment of the present invention, waveguides 518 can be configured
to propagate
microwave energy in a TMab mode, wherein a and b are integers in the range of
from 0 to 5. It
should be understood that, as used herein, the above-defined ranges of a, b,
x, and y values as
used to describe a mode of microwave propagation are applicable throughout
this description.
In one embodiment, the predominant mode of microwave energy propagated through
waveguides 518 and/or discharged via launchers 522a-f can be selected from the
group
consisting of TElo, TMoi, and TEii.
[0106] As shown in FIG. 6a, microwave distribution system 514 further
comprises one
or more microwave launchers 522a-f, each defining at least one launch opening
524a-f for
discharging microwave energy into microwave chamber 520. Although illustrated
in FIG. 6a as
comprising six microwave launchers 522a-f, it should be understood that
microwave distribution
system 514 can include any suitable number of launchers arranged in any
desirable
configuration. For example, microwave distribution system 514 can include at
least 1, at least 2,
at least 3, at least 4 and/or not more than 50, not more than 30, or not more
than 20 microwave
launchers. Launchers 522a-f can be the same or different types of launchers
and, in one
embodiment, at least one of launchers 522a-f can be replaced with a reflective
surface (not
shown) for reflecting at least a portion of the microwave energy discharged
from the other
launchers 522 into microwave heating chamber 520.
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[0107] When microwave distribution system 514 includes two or more launchers,
at
least some of the launchers may be disposed on generally the same side of
microwave
chamber 520. As used herein, the term "same-side launchers" refers to two or
more launchers
positioned on generally the same side of a microwave chamber. Two or more of
the same-side
launchers may also be axially spaced from one another. As used herein, the
term "axially
spaced" denotes spacing in the direction of conveyance of the articles through
the microwave
system (i.e., spacing in the direction of extension of the convey axis).
Additionally, one or more
launchers 522 may also be laterally spaced from one or more other launchers
522 of the
system. As used herein, the term "laterally spaced" shall denote spacing in
the direction
perpendicular to the direction of conveyance of the articles through the
microwave system (i.e.,
spacing perpendicular to the direction of extension of the convey axis). For
example, in FIG. 6a,
launchers 522a-c and 522d-f are disposed on respective first and second sides
521a,b of
microwave chamber 520 and launcher 522a is axially spaced from launcher 522b
and 522c, just
as launcher 522e is axially spaced from launchers 522f and 522d.
[0108] Additionally, as shown in the embodiment depicted in FIG. 6a, microwave
distribution system 514 can comprise at least two (e.g., two or more) pairs of
oppositely
disposed or opposed launchers. As used herein, the term "opposed launchers"
refers to two or
more launchers positioned on generally opposite sides of a microwave chamber.
In one
embodiment, the opposed launchers may be oppositely facing. As used herein
with respect to
opposed microwave launchers, the term "oppositely facing" shall denote
launchers whose
central launch axes are substantially aligned with one another. For
simplicity, central launch
axis 523c of launcher 522c and central launch axis 523d of launcher 522d are
the only central
launch axes illustrated in FIG. 6a. However, it should be understood that each
of launchers
522a-f include a similar launch axes.
[0109] Opposed launchers may be generally aligned with one another, or may be
staggered from one or more other launchers disposed on the opposite side of
microwave
chamber 520. In one embodiment, a pair of opposed launchers may be a staggered
pair of
launchers, such that the discharge openings 524 of the launchers 522 are not
in substantial
alignment with one another. Launchers 522a and 522e constitute one exemplary
pair of
opposed launchers arranged in a staggered configuration. Staggered opposed
launchers may
be axially or laterally staggered from one another. As used herein with
respect to opposed
microwave launchers, the term "axially staggered" shall denote launchers whose
central launch
axes are axially spaced from one another. As used herein with respect to
opposed microwave
launchers, the term "laterally staggered" shall denote launchers whose central
launch axes are
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laterally spaced from one another. In another embodiment, a pair of opposed
launchers may be
directly opposite launchers, such that the discharge openings of the launcher
pair are
substantially aligned. For example, launchers 522c and 522d shown in FIG. 6a
are configured
as a pair of opposite launchers.
[0110] In some embodiments, microwave heating zone 516 can include two or more
convey lines operating simultaneously with one another. An exemplary multi-
line conveyance
system 540 is shown in FIGS. 6b and 6c. As shown in FIGS. 6b and 6c,
conveyance system
540 can be configured to transport a plurality of articles 550 in a convey
direction generally
represented by arrow 560 in FIG. 6b. In one embodiment, conveyance system 540
can include
at least two laterally spaced, substantially parallel convey lines, such as,
for example, first,
second, and third convey lines 542a-c shown in FIG. 6b. Convey lines 542a-c
can, in one
embodiment, comprise individual conveyance systems, while, in another
embodiment, each of
convey lines 542a-c can be portions of an overall conveyance system.
Conveyance system 540
and/or convey lines 542a-c can be any suitable type of conveyor or conveyance
system,
including those discussed in detail previously.
[0111] Microwave heating system 516 depicted in FIGS. 6b and 6c includes a
plurality
of microwave launchers 522 that can be divided or organized into at least two
groups of two or
more microwave launchers. Each of first, second, and third convey lines 542a-c
can be
configured to receive microwave energy from respective first, second, and
third groups of
microwave launchers. In one embodiment, a "group" of launchers can refer to
two or more
axially spaced launchers, generally position along the convey direction (e.g.,
launcher group
522a-d, launcher group 522e-h, and/or launcher group 522i-I shown in FIG. 6b),
while, in the
another embodiment, a "group" of launchers can include one or more pairs of
opposed
launchers positioned on different sides of a microwave chamber (e.g., groups
that include pair
of launchers 522a and 522m, the group that includes pair of launchers 522b and
522n, group
that includes pair of launchers 522c and 522o, and group that includes pair of
launchers 522d
and 522p, as shown in FIG. Sc). When the group of launchers comprises one or
more pairs of
opposed launchers, the launchers can be arranged in a staggered configuration
(not shown) or
can be directly opposite one another (e.g. oppositely facing), as illustrated
in FIG. 6c. According
to one embodiment, at least one generator, shown as generator 512a in FIG. 6b,
can be
configured to provide microwave energy to at least one group of microwave
launchers.
[0112] As particularly shown in FIG. 6b, individual microwave launchers 522 of
adjacent convey lines 542 can be arranged in a staggered configuration
relative to one another
in the convey direction. In one embodiment, one or more same-side microwave
launchers
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522a-I may be axially staggered from one another. For example, in the
embodiment shown in
FIG. 6b, launchers 522a-d associated with first convey line 542a are arranged
in a staggered
configuration relative to each of respective launchers 522e-h associated with
second convey
line 542b with respect to and/or along the convey direction 560. As used
herein with respect to
same-side microwave launchers, the term "axially staggered" shall denote
launchers that are
axially spaced from one another by distance greater that 1/2 the maximum axial
dimension of the
launch openings of the launchers. As used herein with respect to same-side
microwave
launchers, the term "laterally staggered" shall denote launchers that are
laterally spaced from
one another by a distance greater that 1/2 the maximum lateral dimension of
the launch openings
of the launchers.
[0113] Additionally, in the same or another embodiment, the microwave
launchers
associated with the non-adjacent convey lines (e.g., first and third convey
lines 542a,c) can be
arranged in a substantially aligned configuration relative to one another, as
illustrated by the
arrangement of launchers 522a-d relative to launchers 522i-I shown in FIG. 6b.
Alternatively, at
least a portion of the launchers 522i-I associated with third convey line 542c
may be staggered
with respect to launchers 522a-d of first convey line 542a and/or second
convey line 542b
(embodiment not shown). Although generally depicted in FIG. 6b as including
little to no space
between launchers of adjacent convey lines, it should be understood that, in
one embodiment,
that some space may exist between launchers of adjacent lines (e.g., launchers
522a and 522e,
launchers 522b and 522f, etc.). Further, individual launchers 522 can have any
suitable design
or configuration and, in one embodiment, can include at least one feature from
one or more
embodiments of the present invention which will be described in detail herein.
[0114] Turning now to FIG. 7a, a partial view of one embodiment of a microwave
heating zone 616 is shown. Microwave heating zone 616 includes at least one
microwave
launcher 622 that defines a launch opening 624 for discharging energy into a
microwave
chamber 620. As shown in FIG. 7a, microwave launcher 622 is configured to
discharge
microwave energy along a central launch axis 660 toward a conveyance system
640 configured
to transport a plurality of articles 650 within microwave chamber 620 along a
convey axis 642.
In one embodiment, central launch axis 660 can be tilted such that a launch
tilt angle, 13, is
defined between central launch axis 660 and a plane normal to convey axis 642,
illustrated as
plane 662 in FIG. 7a. According to one embodiment, launch tilt angle 13 can be
at least about
2 , at least about 4 , at least about 5 and/or not more than about 15 , not
more than about 10 ,
or not more than about 8 .
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[0115] Turning now to FIG. 7b, another embodiment of a microwave heating
system 616
is shown as including two or more launchers 622a-c, each configured to
discharge energy into
microwave chamber 620 along respective tilted central launch axes 660a-c. In
one embodiment
wherein microwave heating system 616 includes two or more tilted launchers,
the central launch
axes of the launchers, especially the same-side launchers, can be
substantially parallel to one
another, as generally illustrated by central launch axes 660a,b of launchers
622a,b shown in
FIG. 7b. As used herein, the term "substantially parallel" means within 5 of
being parallel. In
the same or another embodiment, the central launch axes of two or more
launchers, especially
opposed launchers, within microwave heating zone 616 can be substantially
parallel or
substantially aligned, as illustrated by launch axes 660a,c of microwave
launchers 622a,c in
FIG. 7b. When microwave heating zone 616 comprises n tilted microwave
launchers having
central launch axes oriented as described above, each launcher can define a
respective launch
tilt angle, 13õ, within the ranges discussed previously. In one embodiment,
each of the launch tilt
angles 13, of each launcher may be substantially the same, while, in another
embodiment, at
least one of the launch tilt angles 13, can be substantially different than
one or more other launch
tilt angles.
[0116] Referring back to FIG. 6a, at least one of launch openings 524a-f of
launchers
522a-f of microwave system 516 can be at least partially covered by a
substantially microwave-
transparent window 526a-f disposed between each launch opening 524a-f and
microwave
chamber 520. Microwave-transparent windows 526a-f can be operable to prevent
fluid flow
between microwave chamber 520 and microwave launchers 522a-f while still
permitting a
substantial portion of the microwave energy from launchers 522a-f to pass
therethrough.
Windows 526a-f can be made of any suitable material, including, but not
limited to one or more
thermoplastic or glass material such as glass-filled Teflon,
polytetrafluoroethylene (PTFE),
poly(methyl methacrylate (PMIVIA), polyetherimide (PEI), aluminum oxide,
glass, and
combinations thereof. In one embodiment, windows 526a-f can have an average
thickness of at
least about 4 mm, at least about 6 mm, at least about 8 mm and/or not more
than about 20 mm,
not more than about 16 mm, or not more than about 12 mm and can withstand a
pressure
difference of at least about 40 psi, at least about 50 psi, at least about 75
psi and/or not more
than about 200 psi, not more than about 150 psi, or not more than about 120
psi without
breaking, cracking, or otherwise failing.
[0117] Several embodiments of suitable configurations for microwave launcher
windows
are generally depicted in FIGS. 8a-c. As shown in FIGS. 8a-c, each of
microwave windows 726
define a chamber-side surface 725 that can optionally define at least a
portion of the sidewall
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721 of microwave chamber 720. According to one embodiment shown in FIG. 1,
chamber-side
surface 725 of window 726 can be configured such that at least about 50
percent, at least about
65 percent, at least about 75 percent, at least about 85 percent, or at least
about 95 percent of
the total surface area of chamber-side surface 725 is oriented at a tilt
angle, a, from the
horizontal. Tilt angle a can be at least about 2 , at least about 4 , at least
about 8 , at least
about 10 and/or not more than about 45 , not more than about 30 , or not more
than about 15
from the horizontal, illustrated as dashed line 762. In other embodiments, the
tilt angle, a, may
also be defined between the axis of elongation 762 of microwave chamber 720
and/or an axis of
convey (not shown in FIGS. 8a-c) when, for example, these axes are parallel to
the horizontal.
[0118] Chamber-side surface 725 of window 726 can be oriented from the
horizontal
regardless of whether or not launcher 722 is oriented with a launch tilt angle
as described
above. In one embodiment, window 726 can be substantially planar and sloped
from the
horizontal (as shown in FIG. 8a), while, in the same or another embodiment,
chamber-side
surface 725 of window 726 can include one or more convexities (as shown in
FIG. 8b) or
concavities (as shown in FIG. 8c). When chamber-side surface 725 is not
substantially planar,
one or more (or n) total tilt angles may be formed as described above.
Depending on the exact
configuration of chamber-side surface 725, the multiple tilt angles formed
thereby may be the
same as or different than other tilt angles formed by the same surface 725.
[0119] As discussed previously, the microwave launchers 522a-f depicted in
FIG. 6a
may be of any suitable configuration. Several views of a microwave launcher
822 configured
according to one embodiment of the present invention are provided in FIGS. 9a-
f. Referring
initially to FIG. 9a, microwave launcher 822 is illustrated as comprising a
set of opposing
sidewalls 832a,b and a set of opposing end walls 834a,b, which collectively
define a
substantially rectangular launch opening 838. When launch opening 838
comprises a
rectangular-shaped opening, it can have a width (W1) and a depth (D1) defined,
at least in part,
by the terminal edges of sidewalls 832a,b and 834a,b, respectively. In one
embodiment,
sidewalls 832a,b can be broader than end walls 834a,b such that the length of
the lower
terminal edge of side walls 832a,b, shown as W1 in FIG. 9a, can be greater
than the length of
the lower terminal edge of end walls 834a,b, depicted in FIG. 9a with the
identifier D1. As
shown in FIG. 9a, the elongated portion of side walls 832a,b and end walls
834a,b can also
collectively define a pathway 837 through which microwave energy can propagate
as it passes
from the microwave inlet 836 to the at least one launch opening 838 defined by
launcher 822.
[0120] When used to discharge microwave energy into a microwave chamber,
launch
opening 838 can be can be elongated in the direction of extension of the
microwave chamber
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(not shown) or in the direction of convey of the articles therein. For
example, in one
embodiment, side walls 832a,b and end walls 834a,b of launcher 822 can be
configured such
that the maximum dimension of launch opening 838 (shown in FIG. 9a as WO can
be aligned
substantially parallel to the direction of extension of the microwave chamber
and/or to the
direction of convey of articles passing therethrough. In this embodiment, the
terminal edges of
side walls 832a,b can be oriented parallel to the direction of extension (or
the direction of
convey), while the terminal edges of end walls 834a,b may be aligned
substantially
perpendicular to the direction of extension or convey within the microwave
chamber (not shown
in FIG. 9).
[0121] FIGS. 9b and 9c respectively provide views of a sidewall 832 and end
wall 834 of
microwave launcher 822 illustrated in FIG. 9a. It should be understood that,
while only one of
the side or end walls 832, 834 are shown in FIGS. 9b and 9c, the other of the
pair could have a
similar configuration. In one embodiment, at least one of side wall 832 and
end wall 834 can be
flared such that the inlet dimension (width Wo or depth Do) is smaller than
the outlet dimension
(width Wi or depth Di), as respectively illustrated in FIGS. 9b and 9c. When
flared, each of side
and end walls 832, 834 define respective width and depth flare angles, 0,, and
Od, as shown in
FIGS. 9b and 9c. In one embodiment, width and/or depth flare angles 0,, and/or
Od can be at
least about 2 , at least about 5 , at least about 10 , or at least about 15
and/or not more than
about 45 , not more than about 30 , or not more than about 15 . In one
embodiment, the width
and depth flare angles Ow and Od can be the same, while, in another
embodiment, the values for
Ow and ed may be different.
[0122] According to one embodiment, depth flare angle Od can be smaller than
width
flare angle Ow. In certain embodiments, depth flare angle ad can be not more
than about 0 ,
such that the inlet depth Do and the outlet dimension Di of microwave launcher
822 are
substantially the same, as illustrated in the embodiment depicted in FIG. 9d.
In another
embodiment, the depth flare angle ed may be less than 0 , such that D1 is
smaller than Do, as
shown in FIG. 9e. When microwave launcher 822 comprises a depth flare angle
less than 0
and/or the depth D1 of launch opening 838 is smaller than the depth Do of
microwave inlet 836,
microwave launcher 822 can be a tapered launcher having a generally inverse
profile. In one
embodiment wherein microwave launcher 822 comprises n launch openings, between
1 and n
of the openings can have a depth and/or width less than or equal to the depth
and/or width of
the inlet of the launcher. Further embodiments of multi-opening launchers will
be discussed in
detail below.
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[0123] According to one embodiment of the present invention, the depth D1 of
launch
opening 838 can be no more than about 0.625A, not more than about 0.5A, not
more than about
0.4A, not more than about 0.35A, or not more than about 0.25A, wherein A is
the wavelength of
the predominant mode of microwave energy discharged from launch opening 838.
Although not
wishing to be bound by theory, it is believed that minimizing the depth D1 of
launch opening 838,
the microwave field created proximate launch opening 838 is more stable and
uniform than
would be created by launchers having greater depths. In one embodiment wherein
microwave
launcher 822 comprises n launch openings, the depth of each launch opening,
dn, can be not
more than about 0.625A, not more than about 0.5A, not more than about 0.4A,
not more than
about 0.35A, or not more than about 0.25A. When microwave launcher 822 has
multiple
openings, each opening can have a depth that is the same or different than one
or more of the
other launch openings of the same launcher.
[0124] Referring now to FIGS. 10a-c, another embodiment of a microwave
launcher 922
suitable for use in the microwave heating systems described herein is
illustrated as comprising
a single microwave inlet 936 and two or more launch openings, shown as launch
or discharge
openings 938a-c, for discharging microwave energy therefrom. Microwave
launcher 922
illustrated in FIGS. 10a-c includes first, second, and third spaced apart
launch openings 938a-c,
which are laterally spaced from one another. Although described herein as
defining three
launch openings, it should be understood that launcher 922 can include any
suitable number of
launch openings including at least 2, at least 3, at least 4 and/or not more
than 10, not more
than 8, or not more than 6. The spacing between each of first, second, and
third launch
openings 938a-c can be at least about 0.05 A, at least about 0.075A, or at
least about 0.10 A
and/or not more than about 0.25 A, not more than about 0.15 A, or not more
than about 0.1 A,
wherein A is the wavelength of the predominant mode of microwave energy
discharged from
launcher 922.
[0125] In one embodiment, each of first, second, and third launch openings are
separated by one or more dividing septum (or septa) 940a,b disposed within the
interior of
launcher 922, as shown in FIGS. 10a-c. Septa 940a,b typically have a thickness
equal to the
desired spacing between the discharge openings 938a-c. When microwave launcher
comprises
n septa, microwave launcher 922 defines (n+1) separated launch openings and
(n+1) separate
microwave pathways 937a-c defined between microwave inlet 836 and each of
launch openings
938a-c, as particularly shown in FIG. 10c. As shown in FIG. 10c, each of
microwave pathways
937a-c has a length, L1-L3, which extends from inlet 936 to a point
perpendicular with respective
launch opening 938a-c. Each of 1.1-L3 can be substantially the same, or at
least one of L1, L2,
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and L3 can be substantially different. According to one embodiment,
particularly shown in FIG.
10c, one or more pathways 937a-c can be longer than one or more other pathways
937a-c.
[0126] When one or more pathways 937a-c are of different lengths than one or
more
other pathways, the dimensions (L1, L2, and/or L3) of pathways 937a-c may be
adjusted such
that the phase velocity of the microwave energy propagating therethrough
accelerates at a more
rapid pace within the longer microwave pathways (e.g., L1 and L3 in FIG. 10c)
than through the
shorter pathways (e.g., L2 in FIG. 10c). Although not wishing to be bound by
theory, it is
hypothesized that such adjusting can be carried out to ensure uniform
synchronization of
individual wave portions, thereby creating a uniform wave front as the
microwave energy is
discharged into chamber 520. When microwave launcher 922 includes a single
septum, only
two microwave pathways are created (embodiment not shown) and the length of
each pathway
is substantially the same. Consequently, little or no control of the phase
velocity of microwave
energy passing through the equal length pathways may be needed.
[0127] In the same or another embodiment, each of launch openings 938a-c can
define
a depth, d1-3, as generally depicted in FIG. lob. In one embodiment, each of
depths di through
d3 can be substantially the same, while, in another embodiment, at least one
of the depths d1-d3
can be different. As discussed previously, one or more of d1-d3 can be not
more than about
0.625 A, not more than about 0.5 A, not more than about 0.4 A, not more than
about 0.35 A, or
not more than about 0.25 A, wherein A is the wavelength of the predominant
mode of microwave
energy discharged from launch opening 938a-c. In addition, in one embodiment,
at least one of
di-do can be less than or equal to the depth do of inlet 936 as discussed in
detail previously. As
shown in FIG. 10b, the depths, d1-3, of each of launch openings 938a-c do not
include the
thickness of septa 940a,b, when present.
[0128] Referring again to FIG. 6a, in one embodiment, the microwave
distribution
system 514 of microwave heating zone 516 can include at least one microwave
distribution
manifold 525a,b for allocating or distributing microwave energy into chamber
520 via a plurality
of launchers 522a-c and 522d-f. In one embodiment, microwave distribution
manifold 525a,b
can include at least three microwave allocation devices configured to divide
the microwave
energy from generator 512 into two or more separate portions prior to being
discharged from at
least some of microwave launchers 522a-f. As used herein, the term "microwave
allocation
device" refers to any device or item operable to divide microwave energy into
two or more
separate portions, according to a predetermined ratio. As used herein, the
term "predetermined
power ratio" refers to the ratio of the amount of power of each resultant
separate portion exiting
a specific microwave allocation device. For example, a microwave allocation
device configured
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to divide the power passing therethrough at a 1:1 power ratio would be
configured to divide the
power introduced therein into two substantially equal portions.
[0129] However, in one embodiment of the present invention, at least one of
the
microwave allocation devices, shown as inductive irises 570a-h and "T-shaped"
or two-way
splitter 572 in FIG. 6a, of microwave distribution system 514 can be
configured to have a
predetermined power ratio that is not 1:1. For example, one or more of the
microwave
allocation devices 570a-h or 572 can be configured to divide the microwave
energy passing
therethrough according to a predetermined power ratio of at least about 1:1.5,
at least about
1:2, at least about 1:3 and/or not more than about 1:10, not more than about
1:8, or not more
than about 1:6.
[0130] Each of the allocation devices 570a2-h and/or 5 employed by microwave
distribution system 514 may be configured to discharge energy according to the
same ratio, or
one or more of allocation devices 570a-h can be configured at a different
power ratio. Allocation
devices 570a-h and 572 can be configured such that substantially the same
amount of power is
discharged from each of launchers 522a-f, while, in another embodiment, the
allocation devices
570a-h and 572 can be collectively designed such that more power is diverted
to and
discharged from one or more launchers 522a-f, with less power being discharged
through the
remainder of the launchers 522a-f. The specific power ratios utilized each of
microwave
allocation devices 570a-h and 572, as well as the pattern or overall
configuration of microwave
energy allocation within the system, can depend on a variety of factors
including, for example,
the type of articles being heated, the desired operating conditions of the
microwave heating
zone 516, and other similar factors.
[0131] In operation, an initial quantity of microwave power can be introduced
into
microwave distribution system 514 and can be divided into two portions as it
passes through
splitter 572. In one embodiment, the two portions of microwave energy exiting
splitter 572 can
be approximately of approximately the same power, while, in another
embodiment, one of the
two portions may have more power than the other. As shown in FIG. 6a, each
portion may pass
to a respective manifold 525a,b, optionally passing through a phase shifting
device 530 prior to
entering manifold 525a,b. Described now with respect to microwave distribution
manifold 525a,
it should be understood that analogous operation is applicable to the lower
manifold 525b
shown in FIG. 6a.
[0132] The microwave power exiting splitter 572 and optionally phase shifting
device
530 (embodiments of which will be discussed in detail below) may then pass
through a
microwave allocation device, shown as iris 570a, whereupon the power can be
divided into a
73
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first launch microwave fraction and a first distribution microwave fraction.
The first launch
microwave fraction can be directed toward launcher 522a and can be discharged
via outlet 524a
The first distribution microwave fraction can be propagated down waveguide 518
toward the
additional microwave launchers 522b,c. According to one embodiment, the power
ratio of the
first launch microwave fraction to the first distribution microwave fraction
exiting iris 570a can be
not more than about 1:1, not more than about 0.95:1, not more than about
0.90:1, not more than
0,80:1, not more than about 0.70:1 or not more than 0.60:1. In one embodiment,
the power
ratio of the first launch microwave fraction to the first distribution
microwave fraction is not 1:1.
[0133] As the first distribution microwave fraction propagates toward
launchers 522b,c,
it can subsequently be divided into a second launch microwave fraction
directed toward
launcher 522b to be discharged via launch outlet 524b, and a second
distribution microwave
fraction that propagates down waveguide 518 toward launcher 522c. In one
embodiment, the
ratio of second launch microwave fraction to second distribution microwave
fraction can be at
least about 0.80:1, at least about 0.90:1, at least about 0.95:1 and/or not
more than about 1.2:1,
not more than about 1.1:1, not more than about 1.05:1, or can be approximately
1:1.
Subsequently, the remainder of the microwave energy (e.g., the entirety of the
second
distribution microwave fraction) can then be directed to the final microwave
launcher 522c and
discharged from launch outlet 524c.
[0134] According to another embodiment (not shown in FIG. 6a), microwave
distribution
system 514 can include a microwave distribution manifold 525a,b having more
than three
launchers. For example, when microwave distribution manifold 525 includes n
launchers, all but
the (n-1)th step of dividing can be carried out such that the ratio of the
launch microwave
fraction to the distribution microwave fraction is not 1:1. For each of the
steps except the (n-1)th
step, the power ratio can be not more than about 1:1, not more than about
0.95:1, not more than
about 0.90:1, not more than 0,80:1, not more than about 0.70:1 or not more
than 0.60:1, while
the (n-1)th dividing step can be carried out such that the ratio of the launch
microwave fraction
to second distribution microwave fraction can be at least about 0.80:1, at
least about 0.90:1, at
least about 0.95:1 and/or not more than about 1.2:1, not more than about
1.1:1, not more than
about 1.05:1, or can be approximately 1:1. The (n-1)th distribution microwave
fraction can then
be sent, in its majority or entirety, as an nth launch microwave fraction to
be discharged to the
microwave chamber via the nth microwave launcher.
[0135] In addition to one or more irises 570a-h positioned within microwave
distribution
system 514, one or more of launchers 522 can also include at least one
inductive iris disposed
within the launcher, as shown in one embodiment illustrated in FIGS. 11a and
11b.
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Alternatively, one or more of irises 570b and/or 570d may be disposed within
launchers 522a
and/or 522b, respectively, rather than be disposed within a waveguide as shown
in FIG. 6a.
[0136] One embodiment of a microwave launcher 1022 including an inductive iris
disposed therein is shown in FIG. 11a. Launcher 1022 may include at least one
inductive iris
1070 located between its microwave inlet 1036 and one or more launch openings
1038, as
generally illustrated in FIGS. ha and 11b. As shown in FIGS. ha and 11b, iris
1070 may be
defined by a pair of inductive iris panels 1072a,b disposed on opposite sides
of launcher 1022.
Although illustrated as being coupled to narrower opposing end walls 1034a,b
of launcher 1022,
it should be understood that first and second iris panels 1072a,b could also
be coupled to
broader opposing side walls 1032a,b of launcher 1022. As shown in FIGS. ha and
lib, first
and second iris panels 1072a,b extend inwardly into the microwave pathway 1037
defined
between microwave inlet 1036 and launch opening 1038 in a direction that is
generally
transverse to the direction of microwave propagation through pathway 1037.
In one
embodiment, iris panels obstruct at least about 25 percent, at least about 40
percent, or at least
about 50 percent and/or not more than about 75 percent, not more than about 60
percent, or not
more than about 55 percent of the total area of microwave pathway 1037 at the
location at
which they are disposed. When microwave launcher 1022 comprises two or more
launch
openings, as shown in FIG. 11c, first and second iris panels 1072a,b can be
configured to
obstruct at least a portion of each of the launch openings 1038a-c of the
launcher 1022.
[0137] As shown in FIG. 11a, first and second iris panels 1072a,b can be
substantially
co-planar and can be oriented substantially normal to the central launch axis
of microwave
launcher 1022. In certain embodiments, the iris panels 1072a,b may be spaced
from both the
microwave inlet 1036 and the launch opening 1038 of microwave launcher 1022.
For example,
the iris panels 1072a,b can be spaced from microwave inlet 1036 of launcher
1022 by at least
about 10 percent, at least about 25 percent, or at least about 35 percent of
the minimum
distance between microwave inlet 1036 and launch opening 1038 of launcher
1022. Further,
iris panels 1072a,b can be spaced from launch opening 1038 of launcher 1022 by
at least about
percent, 25 percent, or 35 percent of the maximum distance (L) measured
between
microwave inlet 1036 and launch opening 1038 of launcher 1022.
[0138] Turning again to FIG. 6a, microwave distribution system 514 is
illustrated as
further comprise one or more devices or for increasing the uniformity and/or
strength of the
microwave field created within microwave heating chamber 520. For example, in
one
embodiment, microwave distribution system 514 can include one or more devices
designed to
modify and/or control the location and strength of the constructive
interference bands of the
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microwave field created within each of individual heating zones 580a-c, which
are respectively
defined between pairs of launchers 522a and 522f, 522b and 522e, and 522c and
522d. In one
embodiment, such a device can be a phase shifting device, schematically
represented in FIG.
6a as device 530, operable to cyclically shift the phase of the microwave
energy passing
therethrough.
[0139] As the articles 550 move along conveyance system 540 within microwave
chamber 520, each article 550 can have an average residence time (t), within
each individual
heating zone 580a-c, of at least about 2 seconds, at least about 10 seconds,
at least about 15
seconds and/or not more than about 1 minute, not more than about 45 seconds,
or not more
than about 30 seconds. In one embodiment, the average residence time (r) for
articles 550 can
be greater than the phase shifting rate (t) for which phase shifting device
530 is configured. For
example, the ratio of the average residence time of the articles passing
through one of individual
heating zones 580a-c to the phase shifting rate of device 530 (-c:t) can be at
least about 2:1, at
least about 3:1, at least about 4:1, at least about 5:1 and/or not more than
about 12:1, not more
than about 10:1, or not more than about 8:1.
[0140] Phase shifting device 530 can be any suitable device for rapidly and
cyclically
shifting the phase of microwave energy passing through microwave distribution
system 514.
According to one embodiment, phase shifting device 530 can be configured to
shift the
microwave energy passing therethrough at a phase shifting rate (t) of at least
about 1.5 cycles
per second, at least about 1.75 cycles per second, or at least about 2.0
cycles per second
and/or not more than about 10 cycles per second, not more than about 8 cycles
per second,
and/or not more than about 6 cycles per second. As used herein, the term
"phase shifting rate"
refers to the number of complete phase shift cycles completed per second. A
"complete phase
shift cycle" refers to a phase shift from 0 to 180 and back to 0 . Although
shown as including
a single phase shifting device 530, it should be understood that any suitable
number of phase
shifting devices can be utilized within microwave distribution system 514.
[0141] In one embodiment, phase shifting device 530 can comprise a plunger-
type
tuning device operable to be moved in a generally linear (e.g., up-and-down
motion) within a
cylinder to thereby cause the phase of the microwave energy passing
therethrough to be
cyclically shifted. FIGS. 12a and 12b illustrate two embodiments of a plunger-
type tuning device
1130a,b suitable for use in microwave distribution system 514. FIG. 12a
depicts a single-
plunger phase shifting device 1130a that includes one plunger 1132 operable to
move within a
single cylinder 1134 via an automatic driver 1136. FIG. 12b illustrates
another embodiment of a
phase shifting device that comprises a multi-plunger phase shifting device
that includes a
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plurality of plungers 1132a-d disposed and operable to moved within several
corresponding
cylinders 1134a-d. Plungers 1132a-d can be driven by a single automatic driver
1136, which
can be connected to each of plungers 1132a-d via a rotatable cam shaft 1138.
Either of
plunger-type tuning devices 1130a,b can be connected to a coupler, such as,
for example, a
short slot hybrid coupler (not shown in FIGS. 12a and 12b) and can be employed
in microwave
distribution system 514 as a phase shifting device 530 as described above.
[0142] Another embodiment of a suitable phase shifting device is depicted in
FIGS. 13a-
e. In contrast to the phase shifting or tuning devices illustrated in FIGS.
12a and 12b, the phase
shifting devices illustrated in FIGS. 13a-e are rotatable phase shifting
devices. For example, as
shown in FIGS. 13a-c, one embodiment of a rotatable phase shifting device
1230, also referred
to as a variable phase short circuit, can comprise a fixed section 1210
defining a first
substantially rectangular opening 1212 and a rotatable section 1240 positioned
proximate said
= first opening 1212. As shown in FIG. 13a, a gap 1213 can be defined
between rotatable section
1240 and fixed section 1210 and, in one embodiment, a microwave choke (not
shown) can be at
least partially disposed within gap 1213 for preventing the leakage of
microwave energy from
fixed and rotatable sections 1210 and 1240.
[0143] Rotatable section 1240 comprises a housing 1242 and a plurality of
spaced
apart, substantially parallel plates 1244a-d received within housing 1242. As
shown in FIG.
13a, housing 1242 comprises a first end 'I243a and a second end 1243b and
first end 1243a
defines a second opening 1246 adjacent to first rectangular opening 1212 of
fixed section 1210.
As indicated by arrows 1290, 1292 in FIG. 13a, rotatable section 1240 can be
configured to be
rotated relative to fixed section 1210 about an axis of rotation 1211
extending through first and
second openings 1212, 1246, as generally shown in FIGS. 13a-c.
[0144] As particularly shown in FIGS. 13b and 13c, housing 1242 has a length
(LH), a
width (WH), and a depth (DH). In one embodiment, at least one of LH, WH, and
DH are at least
about 0.5 A, at least about 0.65 A, at least about 0.75 A and/or not more than
about 1 A, not more
than about 0.9 A, or not more than about 0.75 A, wherein A is the wavelength
of the microwave
energy which variable phase short circuit 1230 is configured to pass between
first and second
openings 1212 and 1246. In one embodiment, at least one of WH and DH are at
least about 0.5
A and both are not more than about A. As generally shown in FIGS. 13a-c, the
cross-sectional
shape of housing 1242 is substantially square, such that the ratio of WH:DH is
not more than
about 1.5:1, not more than about 1.25:1, or not more than about 1.1:1.
[0145] Fixed section 1210 can be any suitable shape or size and may comprise a
circular or a rectangular waveguide. In one embodiment shown in FIG. 13d,
first substantially
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rectangular opening 1212 can have a width (WR) and a depth (Dr) such that the
ratio of WR:DR
is at least about 1.1:1, at least about 1.25:1, or at least about 1.5:1. The
width of first openings
1212 of fixed section 1210 and the width of second opening 1246 of rotatable
section 1240 are
substantially the same, such that the ratio WR:WR is at least about 0.85:1, at
least about 0.95:1,
or at least about 0.98:1 and/or not more than about 1.15:1, not more than
about 1.05:1, or not
more than about 1.01:1.
[0146] As generally shown in FIG. 13a, each of plates 1244a-d can be coupled
to
second end 1243b of housing 1242 and can extend generally toward first end
1243a of housing
1242 in a direction toward first and second openings 1212 and 1244. Each of
plates 1244a-d
can have an extension distance or length, shown as Le in FIG. 13b, of at least
about 0.1A, at
least about 0.2A, at least about 0.25A and/or not more than about 0.5A, not
more than about
0.3511/4, or not more than about 0.30A. Additionally, as particularly shown in
FIG. 13c, one or
more of plates 1244a-d can have a thickness, k, of at least about 0.01A, at
least about 0.05A
and/or not more than about 0.10A, or not more than about 0.075A, wherein A is
the wavelength
of the microwave energy introduced into housing 1242 via first opening 1212.
Adjacent plates
1244a-d can be spaced apart by a spacing distance, j, which can be greater
than, approximately
the same as, or less than the thickness of each plate. In one embodiment, j
can be at least
about 0.01A, at least about 0.05A and/or not more than about 0.10A, or not
more than about
0.075A. Thus, in one embodiment, the ratio of the cumulative surface area of
the distal ends of
plates 1244a-d, generally illustrated as the shaded regions in FIG. 13c, to
the total internal
exposed surface area of second end 1243b of housing 1242, generally
illustrated as the
unshaded regions in FIG. 13c, can be at least about 0.85:1, at least about
0.95:1, or at least
about 0.98:1 and/or not more than about 1.15:1, not more than about 1.10:1, or
not more than
about 1.05:1.
[0147] Variable phase short circuit 1230 can be configured to rotate at a
speed of at
least about 50 revolutions per minute (rpm), at least about 100 rpm, at least
about 150 rpm
and/or not more than about 1000 rpm, not more than about 900 rpm, or not more
than about
800 rpm about axis of rotation 1211, as illustrated in FIG. 13a. In one
embodiment, at least a
portion of the movement of rotatable variable phase short circuit 1230 can be
carried out via an
actuator 1270 coupled to an automatic driver and/or automatic control system
(not shown). In
another embodiment, at least a portion of the movement can be carried out
manually and may
optionally include periods of non-rotation.
[0148] Additional embodiments of other rotatable phase shifting devices 1233
and 1235
suitable for use in microwave distribution system 514 of FIG. 6a, are
illustrated in FIGS. 13e and
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13f, respectively. As shown in the embodiment depicted in FIG. 13e, rotating
phase shifting
device 1233 can include a rotating crank member 1237 coupled via a securing
rod 1239 to a
plunger 1241 disposed within a waveguide 1243. As crank member 1237 rotates as
indicated
by arrow 1261, rod 1239 facilitates a general up-and-down movement of piston
or plunger 1241
within waveguide 1243, as indicated by arrow 1263 in FIG. 13e. Another
embodiment of a
rotating phase shifting device 1235 is depicted in FIG. 13f as including a cam
1245 coupled to a
follower rod 1247, which can be integrated with or coupled to a plunger 1241
disposed within
waveguide 1243. As cam 1245 rotates, follower rod 1247 moves plunger or piston
1241 in a
general up-and-down motion within cylinder 1243, as indicated generally by
arrow 1263.
Additionally, according to one embodiment, rotating phase shifting device 1235
can further
comprise one or more biasing devices 1249 (e.g., one or more springs) for
facilitating movement
of plunger 1241 within waveguide 1243 in an upward direction.
[0149] In addition to being utilized as a rotatable phase shifting device,
variable phase
short circuit 1230 (or, optionally, rotating phase shifting devices 1233,
1235) can also be
configured for use as a tuning device, such as, for example, as an impedance
tuner for tuning
out or canceling unwanted reflections and/or as a frequency tuner for matching
the frequency of
the generator to that of the cavity.
[0150] Turning now to FIG. 14a, one embodiment of a microwave distribution
system
1314 utilizing two variable phase short circuits 1330a,b as an impedance tuner
for canceling or
minimizing reflected power is illustrated. As shown in FIG. 14a, each of
variable phase short
circuits 1330a,b can be connected to adjacent outlets of a coupler 1340, which
can be a short
slot hybrid coupler. In operation, each of variable phase short circuits
1330a,b can be
individually adjusted to a desired position such that impedance tuner tunes
out energy reflected
from microwave launcher 1322 back toward generator 1312. According to one
embodiment,
one or both of variable phase short circuits 1330a,b can be further adjusted
as needed during
the microwave process in order to accommodate changes in the reflection
coefficient of the
articles being heated. In one embodiment, the further adjustments can be at
least partially
carried out using an automatic control system (not shown).
[0151] Variable phase short circuits as described herein can also be utilized
as
frequency tuners for matching the frequency of the cavity to the frequency of
the generator.
According to this embodiment, one or more variable phase short circuits, shown
as variable
phase short circuit 1330c in FIG. 14b, can be directly coupled to individual
ports spaced along a
resonant microwave chamber 1320. In this embodiment, variable phase short
circuit 1330c can
be continuously or sporadically rotated and its position can be manually or
automatically
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adjusted depending on changes within microwave chamber 1320 and/or the
articles being
processed therein (not shown). As a result of this adjustment of variable
phase short circuit
1330c, the frequency of microwave energy within the cavity can be more closely
matched to the
frequency of the generator (not shown).
[0152] Referring again to the microwave heating system 510 shown in FIG. 6a,
more
thorough and/or more efficient heating of articles 550 passed through
microwave chamber 520
may be carried out by, for example, increasing the heat transfer coefficient
between the articles
and the surrounding fluid medium. One embodiment of a microwave chamber 1420
configured
to facilitate quicker and more efficient heating of articles 1450 through
changes in the heat
transfer coefficient within microwave heating chamber 1420 is illustrated in
FIG. 15a. In one
embodiment, the heat transfer coefficient within microwave chamber 1420 can be
increased, at
least in part, by agitating the gaseous or liquid medium within chamber 1420
using one or more
agitation devices, such as, for example, one or more fluid jet agitators 1430a-
d configured to
turbulently discharge one or more fluid jets into the interior of microwave
chamber 1420. In one
embodiment, the fluid jets discharged into microwave chamber 1420 can be a
liquid or a vapor
jet and can have a Reynolds number of at least about 4500, at least about
8000, or at least
about 10,000.
[0153] Structurally, fluid jet agitators 1430a-d can be any device configured
to discharge
a plurality of jets toward articles 1450 at multiple locations within
microwave chamber 1420. In
one embodiment, fluid jet agitators 1430 can be axially spaced along the
central axis of
elongation 1417 of microwave chamber 1420 such that at least a portion of the
jets are
configured to discharge in a direction generally perpendicular to central axis
of elongation 1417.
In another embodiment, particularly shown in FIG. 15b, one or more fluid jet
agitators 1430a-d
can be circumferentially positioned within microwave chamber 1420 such that at
least a portion
of the jets are directed radially inwardly toward the central axis of
elongation 1417 of chamber
1420. Although shown in FIG. 15b as being generally continuous along a portion
of the
circumference of microwave chamber 1420, it should be understood that fluid
jet agitator 1430a
may also include a plurality of distinct jets, radially spaced from one
another along at least a
portion of the circumference of chamber 1420, each positioned to discharge a
fluid jet toward
central axis of elongation 1417 of chamber 1420.
[0154] As shown in FIG. 15a, fluid jet agitators 1430a-d can be positioned
along one or
more sides of microwave chamber 1420 and can be disposed between (alternately)
with one or
more microwave launchers 1422. Use of one or more agitators 1430a-d can
increase the heat
transfer coefficient between the fluid medium within microwave chamber 1420
and articles 1450
CA 3130845 2021-09-10

by at least about 1 percent, at least about 5 percent, at least about 10
percent, or at least about
15 percent, as compared to the heat transfer coefficient of a quiescent
chamber, ceteris paribus.
In the same or another embodiment, one or more jets configured and/or operated
in a similar
manner can be included within one or more other zones of microwave system 10
including
thermalization and/or holding zones 12 and/or 20, illustrated previously in
FIGS. la and lb.
[0155] Referring again to FIGS. la and 1 b, after being withdrawn from
microwave
heating zone 16, the heated articles can then optionally be routed to a
temperature holding zone
20, wherein the temperature of the articles can be maintained at or above a
certain minimum
threshold temperature for a specified residence time. As a result of this
holding step, the
articles removed from holding zone 20 can have a more consistent heating
profile and fewer
cold spots. In one embodiment, the minimum threshold temperature within
holding zone 20 can
be the same as the minimum temperature required within microwave heating zone
16 and can
be at least about 120 C, at least about 121 C, at least about 122 C and/or not
more than about
130 C, not more than about 128 C, or not more than about 126 C. The average
residence time
of articles passing through holding zone 20 can be at least about 1 minute, at
least about 2
minutes, or at least about 4 minutes and/or not more than about 20 minutes,
not more than
about 16 minutes, or not more than about 10 minutes. Holding zone 20 can be
operated at the
same pressure as microwave heating zone 16 and can, in one embodiment, be at
least partially
defined within a pressurized and/or liquid-filled chamber or vessel.
[0156] After exiting holding zone 20, the heated articles of microwave system
10 can
subsequently be introduced into a quench zone 22, wherein the heated articles
can be quickly
cooled via contact with one or more cooled fluids. In one embodiment, quench
zone 22 can be
configured to cool the articles by at least about 30 C, at least about 40 C,
at least about 50 C
and/or not more than about 100 C, not more than about 75 C, or not more than
about 50 C in a
time period of at least about 1 minute, at least about 2 minutes, at least
about 3 minutes and/or
not more than about 10 minutes, not more than about 8 minutes, or not more
than about 6
minutes. Any suitable type of fluid can be used as a cooling fluid in quench
zone 22, including,
for example, a liquid medium such as those described previously with respect
to microwave
heating zone 16 and/or a gaseous medium.
[0157] According to one embodiment generally depicted in FIGS. la and 1 b,
microwave
heating system 10 may also include a second pressure adjustment zone 14b
disposed
downstream of microwave heating zone 16 and/or holding zone 20, when present.
Second
pressure adjustment zone 14b may be configured and operated in a manner
similar to that
previously described with respect to first pressure adjustment zone 14a. When
present, second
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pressure adjustment zone 14b can be located downstream of quench zone 22, such
that a
substantial portion or nearly all of quench zone 22 is operated at an elevated
(super
atmospheric) pressure similar to the pressure under which microwave heating
zone 16 and/or
holding zone 20 are operated. In another embodiment, second pressure
adjustment zone 14b
can be disposed within quench zone 22, such that a portion of quench zone 22
can be operated
at a super-atmospheric pressure similar to the pressure of microwave heating
zone 16 and/or
holding zone 20, while another portion of quench zone 22 can be operated at
approximately
atmospheric pressure. When removed from quench zone 22, the cooled articles
can have a
temperature of at least about 20 C, at least about 25 C, at least about 30 C
and/or not more
than about 70 C, not more than about 60 C, or not more than about 50 C. Once
removed from
quench zone 22, the cooled, treated articles can then be removed from
microwave heating zone
for subsequent storage or use.
[0158] In accordance with one embodiment of the present invention, one or more
methods for controlling the operation of microwave heating system 10 are
provided, for
example, to ensure a consistent and continuous exposure to microwave energy
for each article
or package passing through microwave heating system 10. The major steps of one
embodiment of a method 1500 suitable for controlling the operation of
microwave system 10 are
depicted by individual blocks 1510-1530 in FIG. 16.
[0159] As shown in FIG. 16, the first step of control method 1500 is to
determine a value
for one or more microwave system parameters related to microwave heating zone
16, as
represented by block 1510. Examples of microwave system parameters can
include, but are
not limited to, net power discharged, speed of conveyance system, and
temperature and/or flow
rate of the water within the microwave heating chamber. Subsequently, as shown
by block
1520 in FIG. 16, the resulting determined value for the specific parameter can
then be
compared to a corresponding target value for the same parameter in order to
determine a
difference. Based on the difference, one or more actions can be taken to
adjust the operation of
microwave system 10, as represented by block 1530 in FIG. 16. In one
embodiment, the
adjustment of microwave heating system 10 can be undertaken when, for example,
the
magnitude of the difference is at least about 5 percent, at least about 10
percent, or at least
about 20 percent of the value of the target value and/or determined value for
the specific
microwave system parameter. In one embodiment, at least a portion of the above-
described
method can be carried out using an automatic control system.
[0160] In one embodiment, the basic steps of the above-described control
method 1500
can be utilized by microwave heating system 10 to ensure safety and/or
regulatory compliance
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of the articles (e.g., food and/or medical fluids or equipment) being heated
therein. According to
this embodiment, the one or more microwave system parameters may be selected
from the
group consisting of minimum net power discharged, maximum speed of conveyance
system,
and minimum temperature and/or minimum flow rate of the water within the
microwave heating
chamber. In one embodiment, the minimum temperature of the water in the
microwave
chamber can be at least about 120 C, at least about 121 C, at least about 123
C and/or not
more than about 130 C, not more than about 128 C, or not more than about 126
C, while the
minimum flow rate can be at least about 1 gallon per minute (gpm), at least
about 5 gpm, or at
least about 25 gpm. The maximum speed of the conveyance system, in one
embodiment, can
be not more than about 15 feet per second (fps), not more than about 12 fps,
or not more than
about 10 fps and the minimum net power discharged can be at least about 50 kW,
at least about
75 kW, or at least about 100 kW. When control method 1500 is utilized to
ensure product safety
or compliance, the one or more actions taken to adjust the operation of
microwave heating
system 10 can include, but are not limited to, stopping the conveyance system,
turning off one
or more generators, removing, isolating, and re-running or disposing of one or
more articles
exposed to undesirable conditions, and combinations thereof.
[0161] In the same or another embodiment, the basic steps of control method
1500 can
also be utilized by microwave heating system 10 to ensure quality and
consistency amongst the
articles (e.g., food and/or medical fluids or equipment) being heated.
According to this
embodiment, the microwave parameters can include net power discharged, speed
of
conveyance system, and temperature and/or flow rate of the water within the
microwave heating
chamber. In one embodiment, the temperature of the water in the microwave
chamber can be
at least about 121 C, at least about 122 C, at least about 123 C and/or not
more than about
130 C, not more than about 128 C, or not more than about 126 C, while the flow
rate can be at
least about 15 gallons per minute (gpm), at least about 30 gpm, or at least
about 50 gpm. The
speed of the conveyance system, in one embodiment, can be controlled to a
speed of at least
about 5 feet per second (fps), at least about 7 fps, or at least about 10 fps,
while the net power
discharged can be at least about 75 kW, at least about 100 kW, or at least
about 150 kW.
When control method 1500 is utilized to ensure product quality or consistency,
the one or more
actions taken to adjust the operation of microwave heating system 10 can
include, but are not
limited to, stopping the conveyance system, turning off one or more
generators, removing,
isolating, and re-running or disposing of one or more articles exposed to
undesirable conditions,
and combinations thereof.
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[0162] In order to perform the comparison step 1520 of the method 1500 shown
in FIG.
16, one or more of the target values for at least one of the microwave system
parameters
discussed above can be determined prior to heating the articles in microwave
system 10.
Determination of the magnitude of these target values may be accomplished by
first creating a
prescribed heating profile for the specific type of article to be heated using
a small-scale
microwave system. For example, in one embodiment, one or more articles of a
specific type
(e.g., particular foodstuffs, medical devices, or medical fluids) are first be
loaded into a
microwave chamber of a small-scale microwave heating system. In one
embodiment, the
articles loaded into the small-scale heating chamber can be of a single type
such that the
resultant prescribed heating determined can be specifically applied to that
type of article in a
larger-scale heating system. In one embodiment, the article can be a specific
type and/or size
of packaged food (e.g., an 8-oz MRE package of meat) or can be a packaged
medical fluid
(e.g., saline) or specific types and/or packages of medical or dental
equipment.
[0163] Once loaded into the microwave chamber of the small-scale microwave
heating
system, the article can be heated by introducing microwave energy into the
chamber via one or
more microwave launchers. During this heating period, which can include
multiple heating runs,
a prescribed heating profile can be determined for the article being heated.
As used herein, the
term "prescribed heating profile" refers to a set of target values of a
variety of parameters
suggested or recommended for use when heating a specific type of article. In
addition to
including a target values, prescribed heating profiles can also be expressed,
at least in part, as
a function of time and/or position of the article. In one embodiment, the
prescribed heating
profile can include at least one target value for one or more microwave system
parameters
including, but not limited to, net power discharged, sequential distribution
of microwave power
(i.e., specifics regarding timing, location, and amount of microwave energy
discharged),
temperature and/or flow rate of the fluid (e.g., water) in the microwave
chamber, and/or
residence time of the article within the microwave chamber. In addition, the
prescribed heating
profile can also include target or minimum values for one or more parameters
(e.g.,
temperature, flow rate of fluid, pressure, and article residence time) related
to thermalization,
holding, and/or quench zones 16, 20, 22 of microwave heating system 10.
[0164] Once a prescribed heating profile has been determined, a plurality of
that type of
article can be loaded into a larger-scale microwave heating system and can
then be heated
according to the prescribed profile determined with the small-scale microwave
system,
optionally with the use of an automatic control system. In one embodiment, the
small-scale
microwave heating system can be a batch or semi-batch system and/or can
comprise a liquid-
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filled microwave chamber having a total internal volume of less than 100 cubic
feet, less than 50
cubic feet, or less than 30 cubic feet. In the same or another embodiment, the
large-scale
microwave system can be a continuous or semi-continuous process at least
partially carried out
in a pressurized or liquid filled microwave chamber having a total internal
volume of at least
about 100 cubic feet, at least about 250 cubic feet, or at least about 500
cubic feet. The above-
described steps can subsequently be repeated as many times as needed in order
to create
specific prescribed heating profiles for any number of different articles.
Subsequently, target
values for one or more parameters described above can be determined and used
in the
comparison step 1520 of method 1500 shown in FIG. 16. Thereafter and based on
the
difference, one or more of the actions listed above may be taken to ensure
consistent heating of
the final product.
[0165] One aspect of ensuring consistent heating is ensuring constant and
measurable
power discharged into the heating zone. In one embodiment, a method for
controlling the net
power discharged within microwave heating system 10 is provided. As used
herein, the term
"net power discharged" refers to the difference between the forward and
reflected power within
a waveguide or launcher. As used herein, the term "forward power" refers to
power propagating
in an intended direction from the generator to a load, while the term
"reflected power" refers to
power propagating in a non-intended direction, usually from the load back into
a waveguide or
launcher and toward the generator.
= [0166] The major steps of a method 1600 for determining the net power
discharged
from at least one microwave launcher using two or more pairs of directional
couplers are
summarized in the flow chart provided in FIG. 17. As represented by blocks
1610 and 1620, a
first and second value for net power discharged can be determined using two
independent pairs
of directional couplers. Each pair of directional couplers can include one
coupler for measuring
forward power and another for measuring reflected power and one or more
devices or systems
for calculating the difference to thereby provide respective first and second
values for net power
discharged. According to one embodiment, at least one of the net power values
can be used to
adjust or control the output of the microwave generator, while the other can
be used as a
backup or validation of the other.
[0167] Once values have been obtained from each pair of couplers, the first
and second
values for net power can be compared to determine a difference, as illustrated
by block 1630,
and, based on the difference, an action can be taken to adjust the operation
of the microwave
heating system, as depicted by block 1640. In one embodiment, the action can
be taken when
the difference exceeds a predetermined value, such as, for example, a value
that is at least
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about 1 percent, at least about 2 percent, or at least about 5 percent of the
first and/or second
net power values determined previously. In one embodiment, action can be taken
when the
difference is at least about 1 percent, at least about 2 percent, or at least
about 3 percent of the
lowest of first and second net power values. In another embodiment, action may
also be taken
if one of first or second net power values falls below a predetermined minimum
and/or exceeds
a predetermined maximum. Depending, at least in part, on the articles being
processed and the
difference determined, the action may include, but is not limited to, shutting
down a generator or
conveyance system, increasing or decreasing generator output, and/or removing,
isolating, and
disposing or re-running one or more articles that were disposed within the
microwave heating
chamber when the difference exceeded the predetermined value.
[0168] Microwave heating systems of the present invention can be commercial-
scale
heating systems capable of processing a large volume of articles in a
relatively short time. In
contrast to conventional retorts and other small-scale systems that utilize
microwave energy to
heat a plurality of articles, microwave heating systems as described herein
can be configured to
achieve an overall production rate of at least about 15 packages per minute
per convey line, at
least about 20 packages per minute per convey line, at least about 25 packages
per minute per
convey line, or at least about 30 packages per minute per convey line, which
far exceeds rates
achievable by other microwave systems.
[0169] As used herein, the term "packages per minute" refers to the total
number of
whey gel-filled 8-oz MRE (meals ready to eat) packages able to be processed by
a given
microwave heating system, according to the following procedure: An 8-oz MRE
package filled
with whey gel pudding commercially available from Ameriqual Group LLC
(Evansville, IN, USA)
is connected to a plurality of temperature probes positioned in the pudding at
five equidistant
locations spaced along each of the x-, y-, and z- axes, originating from the
geometrical center of
the package, as shown in FIG. 18. The package is then placed in a microwave
heating system
being evaluated and is heated until each of the probes registers a temperature
above a
specified minimum temperature (e.g., 120 C for sterilization systems). The
time required to
achieve such a temperature profile, as well as physical and dimensional
information about the
heating system, can then be used to calculate an overall production rate in
packages per
minute.
[0170] The preferred forms of the invention described above are to be used as
illustration only, and should not be used in a limiting sense to interpret the
scope of the present
invention. Obvious modifications to the exemplary one embodiment, set forth
above, could be
readily made by those skilled in the art without departing from the spirit of
the present invention.
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[0171] The inventors hereby state their intent to rely on the Doctrine of
Equivalents to
determine and assess the reasonably fair scope of the present invention as
pertains to any
apparatus not materially departing from but outside the literal scope of the
invention as set forth
in the following claims.
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