Note: Descriptions are shown in the official language in which they were submitted.
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CONVEYOR OVEN
s
CROSS REFERENCE TO RELATED APPLICATIONS
The present application claims the benefit of U.S. Provisional Application
Number
60/550,578, filed March S, 2004, entitled "SPEED COOKING CONVEYOR OVEN"; the
to benefit of U.S. Provisional Application Number 60/551,268, filed March 8,
2004, entitled
"ANTENNA COVER; and the benefit.of U.S. Provisional Application Number
60/615,888, filed
October 5, 2004, entitled "CATALYST FOR SPEED COOKING OVEN".
The present application is a continuation-in-part of U.S. Application Serial
Number
10/614,479, filed July 7, 2003, entitled "SPEED COOKING OVEN", currently
pending, which
15 claims the benefit of U.S. Provisional Application Number 60/394,216,
entitled "RAPID
COOKING OVEN", filed July 5, 2002; a continuation-in-part of U.S. Application
Serial Number
10/614,268, filed July 7, 2003, entitled "MULTI RACK SPEED COOKING OVEN",
currently
pending, which claims the benefit of U.S. Provisional Application Number
60/394,216, entitled
"RAPID COOKING OVEN", filed July 5, 2002; a continuation-in-part of U.S.
Application
2o Serial Number 10/614,710, filed July 7, 2003, entitled "SPEED COOKING OVEN
WITH GAS
FLOW CONTROL'', currently pending, which claims the benefit of U.S.
Provisional
Application Number 60/394,216, entitled "RAPID COOKING OVEN", filed July 5,
2002; a
continuation-in-part of U.S. Application Serial Number 10/614,532, filed July
7, 2003, entitled
"SPEED COOKING OVEN", currently pending, which claims the benefit of U.S.
Provisional
25 Application Number 60/394,216, entitled "RAPID COOKING OVEN", filed July 5,
2002.
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The present application . contains technical disclosure in common with
PCT/LTS03/021225, entitled "SPEED COOKING OVEN" filed July 5, 2003, currently
pending,
which claims the benefit of U.S. Provisional Application Number 60/394,216,
entitled "RAPID
COOKING OVEN", filed July 5, 2002; and contains technical disclosure in common
with
PCT/US04/035252 entitled "SPEED COOKING OVEN WITH SLOTTED MICROWAVE
ANTENNA", filed October 21, 2004, which claims the benefit of U.S. Provisional
Application
Number 60/513,110, filed October 21, 2003, entitled "SLOTTED ANTENNA", which
also
claims the benefit of U.S. Provisional Application Number 60/513,111, filed
October 23, 2003,
entitled "MICROWAVE ANTENNA COVER FOR RAPLD COOKING OVEN", which also
Io claims the benefit of U.S. Application Number 601614,877, filed September
30, 2004, entitled
"SLOT ANTENNA". Each of these applications are incorporated herein by
reference as if fully
set forth.
BACKGROUND
The typical cook time for a food product such as a fresh medium size pizza (
12 to 14
inch) through a conventional conveyor oven is approximately 7 minutes, and 15
minutes through
a deck style oven. The conveyor oven reduces cooking time as compared to the
deck oven and
also simplifies the cooking procedure because the food product is
automatically loaded into and
unloaded from the cooking tunnel.
' Conveyor ovens typically utilize a continuous open link conveyor belt to
transport food
products through a heated cooking tunnel which has openings at each end of the
oven through
which the conveyor belt sufficiently extends in order for the operator to
start incoming food
product on one end, and retrieve the finished cook product from the other.
These conveyor oven
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tunnels are generally open at each end and in instances wherein microwave
energy is used, long
entrance and exit tunnels are required in order to reduce the amount of
microwave energy exiting
the tunnel ends. Pizza output capability for such a large conveyor oven is
generally
approximately 100 to 120 medium pizzas per hour.
Although cooking speed is important, food quality is also very important.
Quality, is
generally highest when the food product is cooked and presented to the
consumer as soon as
possible (cooked to order). As such, food service operators must provide fast
service in addition
to a high quality food product and pre-cooking and holding food is therefore
not desirable
because the quality is substantially less than that of a cooked to order food
product.
to A conveyor oven virtually guarantees that a cooked food product will be
removed from
the oven at the proper time, but conveyor ovens have not generally been
compatible with some
type of food service operations such as: quick service restaurant (QSR);
consumer operated .
ovens where the consumer is a retail customer at a retail location such as a
convenience store; or
retail foodservice locations with no room for a large conveyor oven, to name a
few.
SUMMARY
It has now been found that the above objects are obtained in a conveyor oven
with at least
one cooking zone and employing gas flow to cook, or re-thermalize a food
product. The gas
flow to the food product is such that conflicting and colliding gas flows
produce high heat
transfer at the food product surface. Our conveyor oven may also utilize
microwave energy, or
other means such as radio frequency, induction and other thermal means, to
further heat the food
product. Microwave producing magnetrons are used with side wall mounted
microwave
waveguides employing the use of slotted antenna, although it is not necessary
that the microwave
system launches from the oven cavity side walls and indeed launching
microwaves from other
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oven cavity surfaces may be employed. Our conveyor oven may operate as a
conventional
speed, an accelerated speed or a speed cooking conveyor oven. the speed
cooking conveyor
oven is described herein as an exemplary embodiment or version. The speed
cooking conveyor
oven has a cooking tunnel with one or more discrete cooking zones and conveyor
transport
means that moves or indexes food product through the cooking tunnel with
product loading and
un-loading areas located prior to and after the cooking tunnel. The conveyor
loading area for
food product is sized such that the available area for food product is smaller
than the area of each
cook zone of the cooking tunnel. Gas flow and microwave energies (when
microwaves axe used)
are distributed to the food product in a manner that produces uniform cooking
and heating and a
1o typical cook zone temperature range may be in the approximately
375°F (190 degrees Celsius
"C") to approximately 500°F (260°C) range, although cook zone
temperatures below 375°F
(190°C) and above 500°F (260°C) may be utilized. Gas flow
throughout the cooking tunnel is
common to all cook zones and a common heating means provides hot gas fox the
cooking tunnel.
Cooking controls permits a wide variety of food products to be run
sequentially through the
cooking tunnel with each food product having a unique cooking profile, or
recipe, that will be
executed in a sequential format as the food product moves, or indexes, through
the cooking
zones. The indexing conveyor of the exemplary embodiment operates at a fixed
rate, that is,
each cook zone holds food product for the same length of time, but the
indexing time may vary
or may be altered or otherwise set according to the needs of the operator.
2o An optimum speed cooking conveyor oven will maintain the convenience of a
conventional conveyor oven but cook a fresh food product such as a medium
pizza to a high
quality level in less than 3 minutes, thereby representing an approximately
fifty percent decrease
in cooking time over the conventional conveyor oven. The more than double
increase in
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production rate of our invention over the conventional conveyor oven
represents a significant
decrease in cooking time and may allow a foodservice operation to increase the
number of
customer served by: adding a drive-through operation; increasing table service
turn rates;
implementing a consumer operated conveyor oven, or enabling a quick walk-
intake out
function, to name a few. For operations that currently require multiple ovens
to meet customer
demand, the significantly reduced cook times of our speed cooking conveyor
oven permits the
same collective food throughput with fewer ovens.
In addition to such items as pizza, our invention is capable of warming and
cooking a
wide variety of foods such as seafood, Mexican food, hot dogs, sausage,
sandwiches, casseroles,
biscuits, muffins, french fries, fresh and frozen appetizers, fresh proteins,
pies, bread products,
and indeed, any food product that can be cooked in a conventional oven.
Generally,
conventional conveyor ovens do not have a tall cooking tunnel but because
different food
products are of varying volumes, heights and size profiles, a tall cooking
tunnel is desirable for
cooking various food products and the cooling tunnel of our invention allows
for such cooking
of various food products. It is also desirable to keep energy consumption as
low as possible. In
order to accomplish reduced energy costs, our invention utilizes recycling gas
flow and reduces
heat loss from the tunnel ends. Not only is energy savings a benefit,
reduction of heat loss from
the tunnel ends improves the effective energy transfer to the food product.
Our speed cooking
conveyor oven is also simple and safe to operate, easy to clean and maintain,
easy to service and
low cost to manufacture.
Accordingly, it is an object of the present invention to provide a conveyor
oven capable
of cooking and warming a broad variety of food products with varying size and
volume profiles
either at conventional or speed cooking times.
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A fin-ther object is to provide such a conveyor oven that is energy efficient,
simple and
safe to operate, simple and easy to clean, easily serviceable and has a low
manufacturing cost.
Still another object is to provide such a conveyor oven that is capable of
cooking high
quality food product within metal pans, pots, sheet pans and other metal
cooking devices
commonly found in residential, commercial and vending venues.
It is a fiuther object to provide such an oven with a microwave distribution
system which
is more cost effective to manufacture and easy to clean and maintain.
Yet another object is to provide such a rillcrowave distribution system that
is reliable due
to improvements and simplifications.
l0 Still another object is to provide such an oven that can be easily and
quickly programmed
by an operator to cook various food products with the touch of a button or
such an oven that
automatically inputs cooking recipes into a controller without human
intervention.
Additional objects, features and advantages of the present invention will
become readily
apparent from the following detailed description of the exemplary embodiment
thereof, when
taken in conjunction with the drawings wherein like reference numerals refer
to corresponding
parts in the several views.
DRAWINGS
The novel features believed characteristic of the invention are set forth in
the appended
claims. The invention itself, however, as well as a preferred mode of use,
further objectives and
advantages thereof, will best be understood by reference to the following
detailed description of
an illustrative embodiment when read in conjunction with the accompanying
drawings, wherein:
FIG. 1 is a front view of the conveyor oven of the present invention
illustrating gas flow
supply;
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FIG. 2 is a front view of the conveyor oven of the present invention
illustrating gas flow
return;
FIG. 3 is a top view of the conveyor oven of the present invention ;
FIG. 4 is top view of the conveyor oven of the present invention illustrating
product
location relative to cook zones;
FIG. 5 is an end view of the cooking tunnel of the conveyor oven of the
present
invention;
FIG. 6 schematically represents gas flow nodes for the conveyor oven of the
present
invention;
l0 FIG. 7 is a front view of the ingress door microwave containment mechanism
of the
conveyor oven of the present invention;
FIG. 8 is a front view of the front side section illustrating a microwave slot
antenna;
FIG. 9 is an exploded view of the microwave slot antenna of FIG. 8.
FIG. 10 is an end view of the front side of the conveyor oven illustrating gas
flow
deflecting means;
FIG. 11 is an end view of the back side of the conveyor oven illustrating gas
flow
deflecting means;
FIG. 12 illustrates the bleed gas flow of the conveyor oven of the present
invention.
DESCRIPTION
The oven of the exemplary embodiment is shown as a three cook zone speed
cooking
commercial conveyor cooking appliance wherein each cook zone is shown to be
manufactured in
the same manner, although it is not necessary that each cook zone be the same
and indeed in
some instances it may be desirable that one or more cook zones be made
differently. Our
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conveyor oven may be built in other embodiments because it is scalable up or
scalable down.
The term "scalable" herein means that additional larger or smaller versions
may be developed,
and each embodiment or version may have different size characteristics and
utilize different
voltages of electricity; various forms of electric resistance heating means,
or utilize other thermal
s sources such as natural gas, propane or other thermal means to heat the gas.
As used herein, the terms "magnetron", "magnetron tube" and "tube" have the
same
meaning; the terms "slot" "slots" and "antenna" have the same meaning; the
term "commercial"
includes, but is riot limited to the commercial food service industry,
restaurants, fast food
establishments, speed service restaurants, convenience stores (to list a few)
and other mass
to feeding establishments; the term "residential" refers, generally speaking,
to residential
applications (home use), although the term is not limited to residences only,
but refers to non-
commercial applications for the speed cooking oven and our speed cook conveyor
oven is not
limited to commercial uses only, and is equally applicable for vending,
residential and other
cooking uses; the terms "oven zone" and "oven cavity" have the same meaning
and the term
15 "gas" refers to any fluid mixture, including air, nitrogen and other
mixtures that may be used for
cooking and applicant intends to encompass within the language any gas or gas
mixture existing
or developed in the future that performs the same function. The term "cook
zone" refers to a
separate and discrete cooking area within the oven cooking tunnel and the term
"cooking tunnel"
refers to that area of the conveyor oven wherein cooking takes place. For
example, in a one cook
2o zone speed cooking conveyor oven, there will exist one cook zone and one
cooking tunnel. In a
two cook zone speed cooking conveyor oven there will exist two cook zones but
only one
cooking tunnel, and so on. The means for moving the food product through the
speed cooking
conveyor oven is referred to herein as the "conveyor transport means". The
terms "dwell time"
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and "cook time" have the same meaning. and the terms "conventional cooking"
and
"conventional means", have the same meaning and refer to cooking at the
quality level and at the
speed that is currently widely utilized. By way of example, the "conventional
cooking time" for
a fresh 10-12 inch pizza through a conventional oven is approximately 7
minutes (e.g.
conventional cooking time). The term "cooking by-products" refers to smoke,
grease, vapors,
small aerodynamic grease particles, odors, and other products caused by the
cooking process and
the term "odor filter" does not refer exclusively to filtering of odors, but
instead refers generally
to filtering, reduction of, removal of or catalytic destruction of by-products
of the cooking
process.
to As used herein, the term "rapid cooking" and "speed cooking" have the same
meaning
and refer to cooking at five to ten times faster, and in some instances more
than 10 times faster
than conventional cooking. The term "accelerated cooking" has the meaning of
cooking at
speeds faster than conventional cooking but not as fast as speed cooking.
The exemplary embodiment employs the use of an indexing conveyor transport
means
15, wherein the operating speed or feed rate is fixed, meaning that each cook -
zone holds food
product for the same length of time. The dwell time may be varied or fixed,
may be altered
either manually or by controller 334 (see FIG. 3), and is not limited. The
indexing motion of the
conveyor transport means is a cycle consisting of a traverse to move food
product to the next
cook zone followed by a dwell or cooking period wherein the food product is
stopped within a
2o cook zone. This indexing motion insures that the energy delivered to the
food product may be
individualized for each food product. Control of the energy applied to the
food product is
important particularly in those instances wherein the conveyor oven is to cook
a variety of food
products successively and the cooking profile, or cook recipe must be adjusted
as the different
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food products enter the oven tunnel. The conveyor oven may operate as a
conventional,
accelerated or speed cooking conveyor oven.
Appliance 301 includes cook zones 380, 381 and 382 within cooking tunnel 394,
FIG. 4.
The cook zones may be spaced together or a distance apart, depending upon the
particular
conveyor oven that is desired. Each cook zone is generally defned by an oven
cavity 302,
FIGS, a top wall 303, a bottom wall 304, a front side wall 305 and a back side
wall 306. Front
wall 305 is comprised of top gas discharge plate 323a, microwave launcher 320a
(when
microwaves are utilized) and lower gas discharge plate 327a. Back side wall
306 is comprised of
top gas discharge plate 323b, microwave launcher 320b (when microwaves are
used) and lower
1 o gas discharge plate 327b, FIG. 5. In those instances wherein microwave
energy is not utilized in
the conveyor oven, front and back side walls 305 and 306 may be comprised of a
sheet of metal
instead of front of waveguides 320a and 320b. Oven cooking tunnel 394 has
associated
therewith a movable ingress door 398 and a movable egress door 397, FIG.1.
Food product 310,
FIG: 4 is placed on conveyor.transport means 399 for indexed transport through
oven tunnel 394.
As previously described, indexed motion is not required and a continuous
transport means may
be utilized in those instances wherein microwave energy is used and means
other than ingress
and egress doors are employed in order to contain the microwave energy within
cooking tunnel
394. Although doors 397, 398 are shown as movable vertically relative to the
conveyor transport
means, other door opening and closing means may be employed; such as side-
hinged doors, top
hinged doors or doors utilizing other attachment means, and applicant does not
intend to be
limited but rather intends to encompass within the language any structure
presently existing or
developed in the future that performs the same function as doors 397, 398.
to
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The- conveyor oven is comprised of two independent gas transfer systems,
described
herein as a front gas transfer system and a back gas transfer system, wherein
the front gas
transfer system 393a delivers gas to and from the front side of cook zones
380, 381, 382, FIG. 3,
and back gas transfer system 393b delivers gas to and from the back side of
the cook zones 380,
381, 382. Cook zones 380, 381, 382 may also have associated therewith vent
tube 371, FIG 5,
which allows for the passage of vent gas from any one, or all, of cook zones
380, 381, 382 to
atmosphere. ~xed.within vent tube 371 may be vent odor filter 372, which
provides for the
removal of cooking by-products. Vent odor filter 372 may be made to be
removable for cleaning
or replacement and various materials, including catalytic materials, may be
utilized to
l0 accomplish odor removal. In some instances, varying efficiencies of said
materials may also be
employed in order to allow various amounts of odors to escape the oven cavity.
Referring again to FIG. 3, gas is transferred to cook zones 380, 381, 382 via
front gas
transfer conduit 393a extending from gas flow means 316a to first cook zone
3$0, then
continuing to second cook zone 381 and terminating with third cook zone 382,
FIGS l, 3. In
fluid connection with front conduit means 393a are gas flow nodes 390a, 391a,
392, FIG. 6,
which allow for the passage of gas from gas transfer conduit 393a to top gas
transfer section
317a, FIG. 5, of each cook zone 380, 381 and 382. In fluid connection with top
gas transfer
section 317a is top gas egress opening 312, FIG.2, within each cook zone,
which is open to, and
in fluid connection with oven zone 302 through top wall 303. Top gas egress
opening 312 is
substantially rectangular, although other geometries may be employed, and is
centrally located
within each oven top wall 303 and provides for the passage of gas from oven
zone 302 into
return conduit means 389, FIG. 1 which returns gas from oven zone cook zones
380, 381, 382 to
gas flow means 316a as gases are removed from oven zone 302 through top egress
gas egress
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opening 312. Located within each top gas egress opening 312 may be grease
extractor 313, FIG.
2. As gas is drawn through top gas egress opening 312 of each oven zone, the
gas passes across
grease extractor 313, which removes the larger grease particles. By extracting
the larger grease
particles managing grease build-up in the down stream conduits and heater area
is
simplified. It may be desirable for each coop zone to utilize grease extractor
313, or alterr~atively
no grease extractor, or still further additional grease extractors may be
placed throughout the gas
flow path.
During normal cooking it may be desirable for one food product to be cooked
after
another different type of food product with successive cycles continuing. For
example a food
product such as shrimp may be cooked first, followed by a baked product or
pastry. Without
appropriate filtration, the cooking by-products will contaminate the baked
product, producing an
undesirable taste and odor in the pastry. Although grease extractors 313 may
be utilized, further
gas filtration may be desirable and odor filters 343, FIG. 2 may be placed
within any or all cook
zones or within the oven tunnel and may be placed upstream of blowers 316a,
316b to be
discussed firrther herein, and may be made of various materials including
catalyst materia.~s such
as a corrugated foil coated with catalyst, or catalyst coated screens. The
catalyst acts to combust
(oxidize) the cooking by-products. Such catalyst materials may also include,
but is not limited
to: activated charcoal, zeolite or ultra violet wavelight light. It is
beneficial that the odor filters
be comprised of a material, or materials, that effectively scrubs, or cleans
the gas flow with a
minimal amount of interference with the gas flow velocities and it is
beneficial that the odor
filters be easily removed, easily cleaned and inexpensive for the operator to
replace. The most
efficient utilization of the spent hot gas from cook cavity 302 is by re-
circulation of the gas
through the oven tunnel many times during a cooking cycle. In some uses, it
may be~desirable to
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utilize additional odor filters, which may be placed anywhere within the gas
flow path.
Depending upon the various levels of cooking by-product control that may be
desired depending
upon the food products to be cooked, the particular use of the oven, or the
requirements of
regulatory agencies, or other factors, in order to minimize cooking by-
products within each oven
s zone, the oven tunnel or the gas flow supply and return conduits may
therefore include one odor
filter per appliance 301, "n" number of odor filters as determined by "n" cook
zones, or more
than "n" number of odor filters.
As used herein the term "upstream" refers to a location within the gas flow
path that
comes before gas flow means 316a and 316b. For example, gas that is supplied
to gas flow
t o means 316a, 316b is upstream of gas flow means 316a, 316b and gas that is
discharged from gas
flow means 316a, 316b is downstream of said gas flow means. The exemplary
embodiment
illustrates gas flow means as blower wheels 316a, 316b, although our invention
may utilize a
single gas flow device, such as a single blower wheel and applicant intends to
encompass wi ~n
the language any structure presently existing or developed in the future that
performs the same
is function as 316a, 316b. Blower wheels 316a, 316b act much like centrifugal
separators that will
separate and coalesce the small grease particles in the blower scroll area and
discharge larger
particles into the supply area.
In an alternate embodiment, a portion of the gas flow leaving gas flow means
316a, 316b is
diverted to the inlet side of gas bleed chamber 365a, 365b with odor filters
340 located within
2o bleed chambers. The portion of gas flow diverted to said bleed chamber is
referred to herein as
the "bleed gas flow." The bleed gas flow passes through odor filter 340, FIG.
12 shown as a
catalytic converter, where a portion of the cooking by-products is oxidized.
Cleaner gas leaving
odor filter 340 is either reintroduced into the gas flow stream or is vented
to atmosphere via vent
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tube 371. .Odor filter 340 will remove the desired an~.ount.of grease during a
single pass as the
small bleed gas flow will continually remove grease generated during cooking.
Indeed, in some
embodiments it may be desirable for the odor filter to remove all, or as much
cooking by-product
as possible. Varying destruction efficiencies of odor alter 340 will produce
varying results and
in those instances wherein odor filter 340 is of the catalytic type,
destruction efficiencies of
greater than 50% have shown to produce acceptable results. The bleed gas flow
is configured as
an internal cleaning gas loop operating sepaxate from the main gas flow to
oven tunnel 394. In
those instances wherein odor filter 340 is a high effic>Eency catalytic type
filter for high cooking
by-product destruction efficiencies, a large pressure drop may occur across
odor filter 340.
l0 Space velocities for the catalytic converter range are typically in the
range between
approximately 60,000/hr to 120,000/hr depending on the catalyst material
utilized, the amount of
cooking by-product loading in the gas stream and odor filter 340 inlet ambient
temperature.
Unlike the placement of odor filter 343 in the main gas flow which results in
a significant
pressure drop on the entire re-circulating gas flow, the use of bleed gas
catalytic type filters, or
other odor filters, does not significantly reduce gas flow system pressure to
oven tunnel 394.
The small bleed gas flow utilizes nearly the entire pressure capability of the
gas flow means
through the gas bleed system, thereby permitting the use of catalytic
materials required for a high
destruction efficiency, based on one pass through odor filter 340.
Additionally, the small bleed
gas odor filters 340 axe easily installed, can be placed in convenient
locations and readily
2o accessible. Bleed gas flows axe a fraction of the main gas flow to the oven
tunnel, therefore
significant inlet gas temperature preheat may be achieved. Placing small gas
pre-heaters 341a,
341 b, FIG. 12 prior to odor filters 340 within the bleed gas flow system may
additionally provide
substantial improvement in the destruction efficiency of odor filter 340. Pre-
heaters 341a, 341b
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are capable of increasing the gas inlet temperature by greater than
100°F (37.78 °C )and .this
temperature increase in the bleed gas to odor filter 340 makes it possible to
achieve the desired
destruction efficiency with less catalyst material. In some instances a main
gas flow odor and
cooking by-product clean-up system may have difficulty cleaning the gas when
oven set point is
under approximately 425°F (218.3°C). Pre-heaters 341 are capable
of producing cooking by-
product control with oven tunnel temperatures below350°F
(176.67°C). Additional appliance
flexibility is achieved by simultaneously permitting lower oven cook
temperature setting while
providing grease control.
The bleed gas flow is approximately 10% of the total gas flow, blowers 316a,
316b, and pre-
l0 heaters 341a, 341b would each provide approximately 600 watts of heat for a
100°F (37:78°C)
rise in gas uilet temperature. The combined 1200 watts of heating is less than
one third of the
total heat required for each oven zone of conveyor oven and is ~rery close to
the heat needed to
satisfy standby losses of the oven (i.e., heat loss due to conduction,
radiation, vent losses to
ambient). As such, the pre-heaters can be the primary gas heaters with the
larger (for this
is example 3000V~ main gas heater used to satisfy cooking needs. ~
As previously described, in fluid connection with, and located within return
conduit
means 389 is a front gas flow means, illustrated as front blower wheel 316a,
FIGS. 1,5. Our
invention may utilize variable speed blower motors and variable speed blower
motor controllers,
but there is no requirement for their use and indeed the conveyor oven of the
present invention
20 may avoid the problems and complexity of variable speed blower motors by
maintaining a
constant gas flow, or alternatively, a substantially constant gas glow rate
through the oven zones,
oven tunnel and gas transfer and gas delivery systems. The gas flow may be
very aggressive, or
CA 02558409 2006-09-O1
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less aggressive, depending upon the cooking requirements for each food product
and one means
to achieve gas flow modulation is by use of a gas pumping means such as a
blower motor,
blower wheel combination, utilizing a controller or a mufti speed switch that
allows for the
switching of the blower motor speed in pre-determined fixed increments. Other
gas flow means
s may be utilized to accelerate the gas flow, and applicant intends to
encompass within the
language any structure presently existing or developed in the future that
performs the same
function as 316a, 390a, 391a and 316b, 390b and 391b, to be discussed further
herein.
Connected to front blower wheel 316a is blower motor shaft 390a, which is
dixect drive with
electric motor 391a, FIG. 5. Other means may be employed for coupling blower
wheel 316a to
to electric motor 391a, such as belt drive and the drive means is not limited
to direct drive and
applicant intends to encompass within the language any structure presently
existing or developed
in the future that performs the same function. Blower wheel 316a takes gas
from return conduit
means 389 and delivers the gas via conduit means 393a to node sections 390a,
391a, 392x, FIG.
6. Within node sections 390a, 391x, 392a are gas flow control means 388a, FIG.
l, which allow
is for the passage of gas from conduit means 393a to gas transfer section 317a
of each oven zone.
Gas flow control means 388a may allow for the passage of varying quantities of
gas, or no gas,
to transfer section 317a of each cook zone and are shown as valves 388a,
although other means
may be employed in order to allow, limit or restrict the gas flow to each oven
zone 380, 381, 382
by nodes 392a, 391a, 390a and applicant intends to encompass within the
language any structure
20 presently existing or developed in the future that performs the same
function as valves 388a.
Top front gas transfer section 317a, FIG 5, is in fluid connection with a
lower front gas
transfer section 318a via a front vertical gas transfer section 319a. Front
vertical gas transfer
section 319a is bounded by front side wall 366 and a front microwave waveguide
section 320a,
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when microwaves are used. When microwaves are not used, waveguide launches
320a may be
replaced by metal. As can be seen in FIG. 5, as gas is supplied into top front
gas transfer section
317a, the gas is discharged through a top front gas discharge plate 323a into
overt zone 302 via
apertures 300a and onto the front top and front side portion of food product
310. Apertures 300a
may be slotted, regularly formed or irregularly formed apertures and are
illustrated herein as
nozzles 300a and .300b, 329a, 329b, FIG. 5, and applicant intends to encompass
within the
language any structure presently existing or developed in the future that
performs the same
function as 300a, 329a and 300b and 329b, discussed further herein. Gas that
has not been
discharged through top front gas discharge plate 323a flows to lower front gas
transfer section
io 3I8a via vertical transfer section 319a. Gas that is distributed to lower
front gas ixansfer section
318a may be re=heated, if desired, by a lower front heating means 303a, FIG.
5, before said gas
passes through slotted or perforated lower front gas discharge plate 327a via
apertures 329a, for
discharge onto the front bottom and front side portions of food product 310 in
oven zone 302.
Lower front heating means 303a may be present in some embodiments and not
present in others
depending upon the particular requirements for the speed cooking conveyor
oven. Although
lower front heating means 303a is shown as an electric open coil heater, other
means to heat the
gas may be utilized such as other types of electric heating means, electric
resistance elements,
natural gas, propane or other heating means and applicant intends to encompass
within the
language any structure presently existing or developed in the future that
performs the same
function as 303a and 303b to be discussed further herein. Apertures 300a and
329a are sized for
a low pressure drop, while providing and maintaining sufficient gas velocities
in the range of
approximately 2000 ft/minute (609.6 meters/minute) to approximately 6000
ft/manute (1828.80
meters/minute) to properly cook the food product as described herein. In some
instances,
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velocities below 2000 ft/minute (609.6 meters/minute) or above 6000 ft/minute
(1828.80
meters/minute) may also be utilized, depending upon the particular food
product to be cooked, or
a particular cooking recipe that the controller is executing, to be discussed
further herein, and
applicant does not intend to limit the invention to gas velocities within a
particular range.
Apertures 300a are sized such that the majority of the gas is supplied from
top front gas
discharge plate 323a. The resulting imbalance of gas flows between the top
front gas discharge
plate 323a and lower front gas discharge plate 327a is desirable because the
top flows must
aggressively remove moisture produced and escaping from the top and top side
surfaces' of the
food pioduct 310. The gas flow imbalance also serves to heat, brown andlor
heat and brown the
food product 310.
Referring again to FIG. 3, gas is transferred to the back of cook zones 380,
381, 382 via a
back gas transfer conduit 393b, FIG. 3, extending from gas flow means 316b to
first cook zone
380, then continuing to second cook zone 381 and terminating with third cook
zone 382, FIGS
1,3, in .the same manner as previously described for front gas transfer
section 393a. In fluid
is connection with back conduit means 393b are gas flow nodes 390b, 391b,
392b, FIG. 6, which
allow for the passage of gas from gas transfer conduit 393b to top gas
transfer sections 317b,
FIG. 4, of each cook zone 380, 381 and 382. In fluid connection with top gas
transfer section
317b is the previously described top gas egress opening 312, which is in fluid
connection with
return conduit means 389b. Return conduit means 389b is in fluid connection
with a back gas
2o flow means, illustrated as back blower wheel 316b, FIG.3. As with blower
wheel 316a, other
devices may be utilized for gas flow means 316b to accelerate the gas flow,
and applicant intends
to encompass within the language any structure presently existing or developed
in the future that
performs the same function. Connected to back blower wheel 316b is blower
motor shaft 390b,
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which is direct drive with electric motor 391b, and as with electric motor
391a other means may
be employed for coupling blower wheel 316b to electric motor 391b. Blower
wheel 316b takes
gas from oven zone 302 via common return conduit means 389 and delivers the
gas via conduit
means 393b to node sections 390b, 391b, 392b, FIG. 6. Within node sections
390b, 391b, 392b
are gas flow control means 388b, FIG. 5, which allow for the passage of gas
from conduit means
393b to transfer section 317b of each oven zone. As, with gas flow control
means 388a, flow
control means 388b, FIG. 5, may allow for the passage of no gas, or varying
quantities of gas to
transfer section 317b and are shown as valves 388b although other means may be
employed in
order to limit or restrict the gas flow to each oven zone 380, 381, 382 and
applicant intends to
to encompass within the language any structure presently existing or developed
in the future that
performs the same function as valves 388b.
Top back gas transfer section 317b, FIG 5, is in fluid connection with a lower
back gas
transfer section 318b via a back vertical gas transfer section 319b. Back
vertical gas transfer
section 319b is bounded by back side wall 367 and back microwave waveguide
section 320b. As
can be seen in FIG. 5, as gas is supplied into top back gas transfer section
317b, the gas is
discharged through a top back gas discharge plate 323b into oven zone 302 via
apertures 300b
and onto the back top and back side portion of food product 310. Apertures
300b may be slotted,
regularly formed or irregularly formed apertures and are illustrated herein as
nozzles 300b and
329b, FIGS, and applicant intends to encompass within the language any
structure presently
existing or developed in the future that performs the same function as 300b
and 329b. Gas that is
distributed to lower back gas transfer section 318b may be re-heated, if
desired, by a lower back
gas heating means 303b, FIG. S, before said gas passes through slotted or
perforated lower back
gas discharge plate 327b via apertures 329b, for discharge onto the back
bottom and back side
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portions. of food product 310 in oven zone 302. Lower back gas heating means
303b may be
present in some embodiments and not present in others depending upon the
particular
requirements for the speed cooking conveyor oven and as with gas heating means
303.,
previously described, may be made of any material that accomplishes heating of
the gay.
Apertures 300b and 329b are sized for a low pressure drop, while providing and
maintaining
sufficient gas velocities in the range of approximately 2000 ft/minute (609.6
meters/minute) to
approximately 6000 ft/minute (1828.8 meters/minute) to properly. cook the food
product as
described herein. In some instances, velocities below 2000 ft/minute (609.6
meters/minute) and
above 6000 ft/minute (1828.8 meters/minute) may also be utilized. Apertures
300b are sized
to such that the majority of the gas is supplied from the top back gas
discharge plate 323b. As with
the front gas system, the resulting imbalance of gas flows between the top
back gas discharge
plate 323b and lower back gas discharge plate 327b is desirable because the
top flows mus'rt
aggressively remove moisture produced and escaping from the top and top side
surface of the
food product 310. The imbalance also serves to heat, brown and/or heat and
brown the food
product 310.
The front and back gas supply systems, although independently described
herein, are the
same configuration and function to uniformly circulate hot gas flow across the
top and top sides
and bottom and bottom sides of the food product, and return the gas to the
heating mechanism
and gas flow means for re-delivery to the oven zones. Although the same
configuration is shown
in the exemplary embodiment no requirement exists for this symmetry and the
front gas supply
system may be configured differently than the back supply system, and the top
gas supply
systems configured differently from the bottom. Indeed, each cook zone may be
configured
differently than the other cook zones and many combinations of configurations
may be desirable
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for the particular conveyor oven. When a single cook zone conveyor oven is
desired, various
combinations, as previously described may also be utilized.
As previously described, gas flow is delivered via four gas transfer sections
317a, 317b,
318a, 318b which are located in the top and bottom corners of each oven cavity
302 as shown in
FIG. 5. Gas flow transfer sections 317a, 317b; 318a and 318b extend the width
of each oven
zone 302, although it is not required that the gas flow transfer sections
extend the entire length of
the oven zone. Gas transfer section 317a is located in the top front corner of
oven zone 302,
FIG. 5, where top wall 303 intersects oven zone front side wall 366; gas
transfer section 317b in
the top back corner where top wall 303 intersects back side wall 367; gas
transfer section 318a in
io the lower front corner of the oven zone 302 where bottom wall 304
intersects front side wall 366;
and gas transfer section 318b in the lower back corner where bottom wall 304
intersects back
side wall 367. Each gas transfer section is sized and configured to deliver
the appropriate gas
flow for the particular oven utilized. For example, in a smaller oven, the gas
delivery sections,
indeed the entire oven, may be sized smaller in proportion to the smaller
footprint of the
~ particular requirements, and a larger oven may have proportionally larger
gas delivery sections.
As seen in FIG. 5, the front side and the back side gas flows converge on food
product
310 creating an aggressive gas flow field on the food product surface that
strips away the
moisture boundary layer. This turbulently mixed gas flow directed at the food
product can best
be described as glancing, conflicting and colliding gas flow patterns that
spatially average the
gas flow over the surface area of the food product producing high heat
transfer and moisture
removal at the food product surface, thereby optimizing speed cooking. The gas
flow is directed
towards the top, the bottom and the sides of the food product from the front
and back sides of the
oven zone and the front and back side gas flows conflict, collide and glance
off each other at the
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food product surface before exiting the oven zone through top gas egress
opening 312. As used
herein the term "mixing" refers to the glancing, conflicting and colliding gas
flow patterns that
meet at and upon the top surface, the bottom surface and the front and back
side surfaces of the
food product and produce high heat transfer for both conventional and speed
cooking of the food
product due to spatial averaging of the gas flow heat transfer. The mixing gas
flows patterns are
created within the oven zone and, when appropriately directed and deflected,
produce a high
quality cooked food product that can also be cooked very quickly. Although
speed cooking of
high quality food product may be accomplished with this invention,
conventional cooking may
also be accomplished by adjusting the gas flow and microwave energy (in
instances wherein
1 o microwave energy is utilized) to the food product; or by use of gas flow
alone with no
microwave energy. Enhancing the highly agitated, glancing, conflicting, and
colliding gas flow
is the general upward flow path the gas will follow, as shown in FIG. 5
through top gas egress
opening 312, as the gas exits the top of oven zone 302. This upward gas flow
draws also the gas
from lower gas discharge sections 318a and 318b thereby scrubbing the bottom
of the food
product, pot, pan or other cooking vessel, by pulling gas flow around the
sides of said vessel,
further enhancing the heat transfer, as well as drawing the gas that scrubs
the upper surface up
towards the oven zone top wall.
Returning to FIG 5, top gas discharge plates 323a and 323b are positioned
within oven
zone 302 such that the gas flow from top gas transfer section 317a conflicts
and collides with the
2o gas flow from top gas transfer section 317b upon the food product surface
and strikes the food
product at an angle that is between zero degrees and 90 degrees as referenced
from the horizontal
top wall (where zero degrees is parallel to the horizontal top wall) and lower
gas discharge plates
327a and 327b are positioned within oven zone 302 such that the gas flow from
lower gas
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transfer section 318a conflicts and collides with the gas flow from lower gas
transfer section
318b upon the lower surface of the food product at an angle that is between
zero degrees and
ninety . degrees as referenced from the horizontal bottom wall. Various
cooking requirements
may require that the angle of the gas discharge plates 323a, 323b, 327a and
327b be adjusted,
s either during manufacture, or adjustable within the oven after manufacture,
in order for the chef
or cook to change gas flow velocity angles (vectors) to effect different
cooking profiles.
The number and placement of the apertures 300a, 300b, 329a and 329b will vary
according to the particular oven that is desired. For example, a general
purpose speed cooking
conveyor oven may be scaled to a baking oven by changing the number of
apertures, which may
1 o be fewer in number but be larger in size, thereby allowing for a more
gentle gas flow across the
food product, and producing proper delicate baking of the food product. If a
browning oven
were desired, the apertures may be more numerous and smaller in diameter.
Additionally, the
operator may desire more flexibility of cooking and in this circumstance gas
discharge plates
323a, 323b, 327a and 327b may be fabricated in a manner that allows for quick
change-out of the
15 plates by the operator. As used herein the term "aperture" refers to
irregular slots, irregular holes
or irregular nozzles, regularly formed slots, regularly formed holes or
regularly formed nozzles
or a mixture of regularly formed and irregularly formed slots, holes or
nozzles. FIG. 5 illustrates
the use of three rows of apertures 300a and 300b on top gas delivery sections
317a and 317b, and
two rows of apertures on the lower gas delivery systems 318a and 318b,
although more or fewer
20 rows and numbers of apertures may be utilized and applicant intends to
encompass within the
language any structure presently existing or developed in the future that
performs the same
function. The gas delivery system as illustrated in FIG 5 produces aggressive
glancing,
conflicting and conflicting gas flow patterns 330a and 330b wherein an
aggressive top glancing,
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conflicting and colliding gas flow.pattern 330a also interacts with the front
top portion and front
top side portion of food product 310 and a similar back top glancing,
conflicting and colliding
gas flow pattern 330b interacts with the back top portion and top back side
portion of food
product 310. Aggressive glancing, conflicting and colliding gas flow 331a
interacts with the
lower front and side portions of the food product and gas flow 331b interacts
with the lower back
and side portions of the food product. This cooking profile creates high heat
transfer capability
by using the surface of the food product, as well as the interference of flow
fields to minimize
boundary layer growth. After the aggressive glancing and conflicting gas flow
patterns 330a and
330b contact or strike the food product they are exhausted through top egress
section 312 and
to cycle back through the oven as described herein. The highly turbulent flow
of the conflicting gas
patters described herein has several benefits. First, the conflicting gas flow
patterns create cook
zone gas flow that is averaged spatially, or a flow condition that tends to
average out the high
and lows in flow variation for a given point in the cook cavity greatly
reduces the design
complexity needed to impose a uniform flow field over a cooking zone. In those
instances where
gas transfer sections 317x, 317b, 318a and 318b are in use, conflicting gas
flows produce an "X"
style gas flow wherein high heat transfer rates needed for speed cooking
average the flow
conditions over space and time, thereby producing uniform cooking and
browning.
Another advantage of the upward return ,gas path is that a conveyor transport
means may
pass through the cook zones because the two ends of cook cavity 302 are now
free of any gas
2o flow means or microwave related subsystems (i.e., no blower return gas path
or microwave
feeds). Also, uniform side browning is effected because the bottom gas flow is
drawn past the
food product edges as the gas flows up to egress point 312 within roof 303.
Third, grease
loading in the return gas stream is reduced.
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Gas flow control to the various zones is accomplished via simple gas flow
dampers or
valves, referred to as nodes 390x, 390b, 391a, 391b, 392a, 392b. This approach
maintains a
relatively constant flow through the oven thereby eliminating the need for
varying the blower
speed. 'The gas flow within the conveyor oven, as well as other functions of
cooking appliance
301 axe directed by controller 334, FIG. 3. Speed cooking of individual food
products generally
requires a separate cooking profile or recipe for that food product. The speed
cooking conveyor
oven of the exemplary embodiment is capable of cooking various food products
at the same time,
therefore the oven controls must track the food products as they move through
the cook zones
and adjust the gas flow energies, and microwave energies (when
microwave,energy is used) of
to each cook zone according to the cooking recipe that has been input by the
operator or input by a
scanning device, or other device for each food product. The cooking profile
for a food product,
referred to herein as the "cooking recipe" may be quite complex and time and
labor expense
associated with inputting cooking recipes may be minimized by use of
controller 334 loaded with
predetermined cooking recipes from a smart card, or loaded from an automated
product
identification device, or other scanning and reading devices may be utilized.
Alternate
embodiments will allow the operator to place the food product onto conveyor
means 399 in
loading zone 396, FIG. 4 and a unique product identification code could be
used to transfer
recipes to the oven controller, thereby eliminating manual cooking recipe
inputs. Alternatively,
manual single button entries, or multiple button entries may be made by the
operator to input the
cooking recipes and applicant does not intend limitations concerning the use
of the control
system for cooking recipes. Indeed optical scanners may be utilized at the
ingress end of
appliance 301. The exemplary embodiment describes a unique product
identification code that is
encoded with the correct cooking recipe settings for each food product and the
transfer of
CA 02558409 2006-09-O1
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information is accomplished using an Radio Frequency Identification ("RFID")
tag placed on the
food or food packaging. The RFID tag may be programmed from the restaurant
point of sale
system and read by the oven controller by any means known such as cable linked
one way
communication, two way communication, wireless or other means and applicant
intends to
encompass within the language any structure presently existing or developed in
the future that
performs the communication function. Reading of the RFID tag by controller 334
mininuzes
error associated with the operator imputing an incorrect oven cooking recipe
and allows the
restaurant to optimize customer service as the oven controller communicates
with the point of
sale system during the cooking cycle for each food product. Controller 334
determines, among
l0 other things, the velocity of gas flow, which may be constant or varied,
or, may be constantly
varied throughout the cooking cycle and whether or not gas is delivered
through the previously
described cooking nodes to cook zones 380, 381, 382. It may be desired to cook
the food
product on one velocity throughout the entire cooking cycle, or to vary the
gas velocity
depending upon conditions such as a pre-determined cooking recipes, or vary
the gas velocity in
response to various sensors that may be placed within the cooking zone, oven
return gas paths or
various other positions within the oven. The location and placement of said
sensors will be
determined by the particular application of the oven. Additionally, other
means may be utilized
wherein data is transmitted back to controller 334, and thereafter controller
334 adjusts the
cooking recipe in an appropriate manner. For example sensors (temperature,
humidity, velocity,
vision and gas borne chemical mixtuxe level sensors) may be utilized to
constantly monitor the
cooking conditions and adjust the gas flow, and microwave energy, when used,
accordingly
within a cooking cycle, and other sensors not described herein may also be
utilized and the speed
cooking conveyor oven may utilize sensors that are not currently commercially
practical due to
26
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cost or other limitations (such as laser, non-invasive temperature sensors and
other sensors that
'are currently too expensive to be commercially feasible), and the speed
cooking oven is not
limited to those discussed herein, as many sensing devices are known and
utilized in and
applicant intends. to encompass within the language any structure presently
existing or developed
in the future that performs the same function. Additionally, controller 334
may control the
amount of bleed gas flow through each odor filter 340, as previously
described. For example,
oven zone 380 may contain a food product that, upon conventional cooking, or
speed cooking,
will produce larger amounts of airborne grease, smoke and odor than the food
products in the
other cooking zones. In such an instance, controller 334 may allow for more
gas flow to pass
l0 . through odor filter 340 of oven zone 380 and either allow more or less
gas flow to odor filters
that may be utilized for oven zones 381, 382 and to adjust pre-heaters 341x,
341b of oven zone
380.
Gas flow may also be adjusted as a function of available power. In the event,
for
example, the heating means of an all electric speed cooking conveyor oven is
requiring or
utilizing a large amount of power (larger than available power levels which
may vary according
to location and local code and ordinance) it may be desirable for controller
334 to reduce
electrical power to the heating means or other electrical components in order
to ~ conserve
available power. In a speed cooking conveyor oven, some systems may be powered
by electric
current, but the electric power requirements will not be as high as required
for an all electric
oven because the energy required for gas heating and cooking will be provided
by the
combustion of a hydrocarbon based fuel. In this event a controller, may not be
required, indeed
knobs or dials may be utilized.
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In an alternate embodiment, gas flow control may be accomplished by gas flow
control
means, FIGS. 10, 11. As gas is discharged into top front gas transfer section
317x, a selected
portion of said gas may be directed through apertures 300a within gas
discharge plate 323a by
gas deflecting means 324x, shown in the open position, Fig. 10. Gas deflecting
means 324a is
shown as pivotally attached to gas discharge plate 323x, although, other means
for
accomplishing said gas deflection may be utilized. For example means such as
normally open,
normally closed, or normally partially open and normally partially closed
switched plates may be
used (wherein said plates slide along the inside of perforated plate 323a to
limit the aperture
openings 300a of discharge plate 323a), and applicant intends to encompass
within the language
any structure presently existing or developed in the future that performs the
same function as gas
deflecting means 324a. Gas that has not been discharged or deflected through
apertures 300a
flows to lower front gas transfer section 318a via vertical transfer section
319a. Pivotally
attached to waveguide section 320a (when waveguides are used and to sheet
metal when not
used) is a lower gas transfer deflection mechanism 352x, FIG. 10 that operates
to limit the
is amount of gas that is transferred to lower gas transfer section 318a. As
used herein, the terms
"flow control means" "gas deflecting means" "transfer deflection mechanism"
and "flow control
means" all have the same meaning and refer to means to control gas flow within
and to various
parts of the conveyor oven. Indeed, certain cooking operations may call for
more gas flow to the
lower part of the conveyor oven, while other operations will call for little
or no gas flow to the
bottom side of the oven for delivery to the bottom of the food product. In
those instances where
little or no gas flow is desired upon the bottom surface of the food product,
gas transfer
deflection mechanism 352a may be closed in order to allow all, or
substantially all, of the gas
flow into top front gas delivery section 317a.
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Gas that flows to lower front gas delivery section 118a may be re-heated, if
desired, by
lower front heating means 303a, FIG. 10. After passing over heating elements
303a, the gas may
be further deflected by deflecting means 328a, FIG. 10, shown in the open
position. As gas
deflecting means 328a .is rotated, directional control of the gas flow may be
further refined,
allowing for gas flow to pass through the upper or lower rows of apertures of
lower gas plate
327a at various positions along food product 310 bottom surface, FIG. 10.
Although gas
deflecting means 328a is shown as pivotally attached to front slotted or
perforated gas discharge
plate 327a, gas deflecting means 328a is not limited to the pivotally attached
means illustrated
herein, and as described elsewhere herein, applicant intends to encompass
within the language
to any structure presently existing or developed in the future that performs
the same function as gas
deflecting means 324x, 352a, 328a, 324b, 352b and 328b to be discussed further
herein.
As gas is discharged into top back gas transfer section 317b, a selected
portion of said gas
may be directed through apertures 300b within gas discharge plate 323b by gas
deflecting means
324b, shown in the open position, Fig. 11. Gas deflecting means 324b is
pivotally attached to
gas discharge plate 323b, although as with 323a, other means for accomplishing
said gas
deflection may be utilized. For example means such as normally open, normally
closed, or
normally partially open and normally partially closed switched plates may be
used (wherein said
plates slide along the inside of perforated plate 323b to limit the aperture
openings 300b of
discharge plate 323b), and applicant intends to encompass within the language
any structure
2o presently existing or developed in the future that performs the same
function as~ gas deflecting
means 324b. Gas that has not been discharged or deflected through apertures
300b flows to
lower front gas transfer section 318b via vertical transfer section 319b.
Shown as pivotally
attached to waveguide section 320b (when waveguides are used and to sheet
metal when not
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used) is a lower gas transfer deflection mechanism 352b, FIG. 11 that operates
to limit the
amount of gas that is transferred to lower gas transfer section 318b. As with
the front gas
transfer system, certain cooking operations may call for more gas flow to the
lower part of the
conveyor oven, while other operations will call for little or no gas flow to
the bottom side of the
oven for delivery to the bottom of the food product. In those instances where
little or no gas
flow is desired upon the bottom surface of the food product, gas transfer
deflection mechanism
352b may be closed in order to allow all, or substantially all, of the gas
flow into top front gas
delivery section 317b.
Gas that flows to lower back gas delivery section 118b may be re-heated, if
desired, by
lower front heating means 303b, FIG. 1 I. After passing over heating elements
303b, the gas may
be further deflected by deflecting means 328b, FIG. 11, shown in the open
position. As gas
deflecting means 328b is rotated, directional control of the gas flow may be
further- refined,
allowing for gas flow to pass through the .upper or lower rows of apertures of
lower gas plate
327b at various positions along food product 310 bottom surface, FIG. 11.
Although gas
deflecting means 328b is shown as pivotally attached to front slotted or
perforated gas discharge
plate 327b, gas deflecting means 328b is not limited to the pivotally attached
means illustrated
herein, and as described elsewhere herein, applicant intends to encompass
within the language
any structure presently existing or developed in the future that performs the
same function as gas
deflecting means 324x, 352a, 328a, 324b, 352b and 328b.
In those instances wherein directional control of the gas flow is desired, gas
deflecting
means 324a, 324b, 328a, 328b and 352a and 352b, FIGS. 9, 10 may be rotated
such that gas flow
is diverted to selected apertures, thereby effecting a different gas flow
pattern and gas mixing
upon and above the food product surface. Additionally, in those instances
wherein no bottom
CA 02558409 2006-09-O1
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side gas flow is desired, gas deflecting means 352a, 352b may be closed,
thereby allowing for
little or no passage of gas flow to the lower portion of the oven cavity.
Various other
adjustments of gas deflecting means are possible and applicant intends to
encompass within the
language any structure presently existing or developed in the future that
allows for combinations
of open and closed positions of apertures 300x, 300b, 329a and 329b by the
various gas flow
control means described herein. Gas deflecting means 324a, 324b, 328a, 328b
and 352a and
352b may be manually controlled, automatically controlled via controller 334,
controlled by
other mechanical or electrical means, or controlled via combination of
automatic and manual
control and applicant intends to encompass within the language any structure
presently existing
or developed in the future that performs the function described herein
concerning adjustment of
the gas deflecting means. In those instances wherein gas deflecting means 324a
or 324b allow
little or no gas through gas discharge plates 323a~ 323b, and further wherein
little gas flow is
desired through lower gas discharge plates 327a, 327b, a by-pass return gas
flow conduit may be
provided in order to return gas flow to gas return conduit means 389.
Additionally, in those
instances wherein gas directing means 328a, 328b allow little or no gas
through gas discharge
plates 327a, 327b and less gas flow is desired through gas discharge plates
323a, 323b, a conduit
means may be provided to return gas flow to return conduit means 389, or
alternatively to
atmosphere or to gas bleed system previously described for further odor and
grease clean-up.
Indeed, various and multiple combinations of gas flow control exist, depending
upon the
2o particular oven that is desired and gas flow may be directed to many and
various apertures
throughout the conveyor oven in order to accomplish the desired finished
cooked product 310.
The oven of the present invention may also utilize microwave energy to at
least partially
cook the food product. As seen in FIG. 5, front side microwave launching
waveguide 320a is
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attached within oven zone 302 to front side wall 305 between top front gas
discharge plate 323a
and lower front gas discharge plate 327a. Back side microwave launching
waveguide 320b is
attached within oven zone 302 to back side wall 306 between top back gas
discharge plate 323b
and lower back gas discharge plate 327b. The microwave waveguides are designed
to distribute
microwave power from magnetrons 100, FIG. 8, uniformly from the back to the
front of oven
cook cavity 302. The vertical distance above cavity bottom wall 304 of
waveguides 320a and
320b is such that, under normal cooking conditions, approximately more than
one third of the
microwave energy is available below food product 310, with the balance of
microwave energy
available above food product 310.
to As shown in FIG. 5, microwave energy 351x, 351b, FIG. 5, is broadcast from
waveguides
320a, 320b into oven zone 302 via a slotted antenna 370, FIG. 8, wherein three
or four narrow
apertures (slots) 370 ale spaced along the waveguide. Various configurations
for microwave
distribution have been utilized with varying results and less than three slots
may be utilized or
more than three slots may be used, and applicant intends to encompass within
the language any
structure presently existing or developed in the future that performs the same
function.
Important to an efficient and inexpensive slotted microwave system, FIG. 9 is
the slot length
382, slot width, 383, the spacing between the slots, slot end spacing, angle
of the slot relative to
the long axis of the waveguide, the number of slots per waveguide and the slot
orientation.
Slots 370 in waveguides 320a, 320b, are open to the cooking cavity and must be
covered
or protected so that grease and other contaminants cannot enter the waveguide
and a durable and
inexpensive slot antenna cover may be utilized to protect such slots 370. Slot
antenna covers 106
FIG. 8, are configured to cover slots 370 in waveguides 320a, 320b. Slot
antenna covers 106 are
adhered to the surrounding stainless steel of waveguides 320a, 320b using high
temperature
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silicone rubber Room Temperature Vulcanizing ("RTV") sealant. This sealing
appioach creates
high temperature watertight seal between the cover and the surrounding metal.
Although an
RTV sealant has been described in the exemplary embodiment, other sealant
means may be
utilized to adhere antenna covers 106 to waveguide 320a, 320b. The cover
material must be
compatible with high temperature operation, must be of low loss
characteristics relative to
microwave transmission, easily cleaned, durable, and inexpensive. For good
microwave
compatibility, materials with a dielectric constant less than 6 and a loss
tangent less that 0.2 have
been found to provide such characteristics. Such materials must be thin,
generally less than
0.015 inches thick, and be suitable for gluing using (RTV). A Teflon(
PolyTetraFluoroEthylene
("PTFE"))/fiberglass fabric produced by Saint Gobain (ChemFab Product Number
10 BT) which
has one side treated to accepted silicone rubber and is 0.01 inches thick is
described in the
exemplary embodiment and has shown to have little impact on the microwave
characteristics of
the magnetron and microwave waveguide system Results of Smith chart testing
and water rise
experiments of the impedance of the vvaveguide and waveguide antenna for slot
angles greater
than 17 degrees(as measured from a horizontal centerline, 379, FIG.9) and
without antenna cover
106 are approximately the same.
Although two microwave waveguides, 320a, 320b and two magnetrons, 100, are
described per cooking zone, in other embodiments the waveguides may be
supplied by one larger
magnetron, or alternatively various numbers of magnetrons may be utilized and
the invention is
not limited to two magnetrons per cooking zone and applicant intends to
encompass within the
language any structure presently existing or developed in the future that
performs the same
function.
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For optimum cooking, food product 310 is placed within oven zone 302 upon
conveyor
transport means 399 a distance of at least 2.4 inches (for optimal cooking
uniformity) from front
side wall 305 and back side wall 306. The 2.45 inch measurement corresponds to
one half a
microwave wavelength or 2.4 inches (for optimal cooking uniformity) (E field
null) for a 2.45
GHz microwave tube (microwave) frequency. This spacing permits the E-field to
expand and
become more uniform prior to coupling with the food product. Other side
spacing placement
may be utilized with other types of magnetrons systems.
The back side microwave waveguide is identical to the front side system and
microwave
energy is broadcast from back waveguide 320b to oven zone 302 via slotted
antenna 370 as
1o previously described for the front side. Although waveguides 320a and 320b
are configured in
the same manner, infinite combinations of slot designs, slot configurations,
slot widths, slot
lengths, numbers of slots per waveguides and slot orientations are possible
per waveguide
depending upon the type of oven desired. The microwave energy field therefore
propagates
through the oven zone in an evenly distributed pattern, coupling with the food
product from all
directions, and providing an even electromagnetic energy distribution
throughout the oven zone
without the need for a mechanical stirrer to propagate the electromagnetic
field. Waveguides
320a and 320b are located on the front and back side walls of the oven, and
therefore do not
interfere with oven zone spent gas exhaust. Because microwave waveguides are
located on the
side walls of the oven zone, they are not affected by food spills, grease
contamination, cleaning
2o fluid contamination or other contamination that normally affect a bottom
launch microwave
system. The microwave system of the present invention will therefore be less
likely to be
penetrated by grease, spills, cleaning materials and other contaminants
because the systems are
not located directly under the food product where hot contaminants will drip.
It is not required
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that side launch microwave waveguide be employed and indeed microwave
launching may be
accomplished from any oven cavity surface, with varying degrees of
efficiencies.
Microwave waveguides 320a, 320b, FIG. 5 with slotted antenna 370 are
positioned along
the front and back_ cavity walls such that cooking rack 308 is slightly below
slots 370. In this
manner, microwave energy is directed towards the top and bottom of the food
product. For
safety, microwave energy must be contained within cooking tunnel 394 and
historically
conveyor ovens incorporated long entrance and exit tunnels to attenuate the
microwave leakage
escaping from the open oven tunnel ends. These long tunnels not only require
much additional
floor space, but they result in oven cavity heights of only a few inches
thereby greatly limiting
to the food products that can pass through such a conveyor oven. Our invention
eliminates the need
for long entrance and exit tunnels and short cooking cavity height by
employing the indexing
conveyor approach coupled with tunnel doors, 397, 398 FIG. 1, as discussed
herein.
Exemplary food product flow is illustrated in FIG. 4. In order to reduce
controller 334
complexity, the conveyor transport speed may be operated at a fixed rate. This
approach
i 5 establishes dwell times wherein food product 310 remains in a given cook
zone for a fixed period
of time. In addition to simplifying food recipe development and cooking recipe
algorithms, a
fixed dwell time also reduces complexities associated with conveyor drive
mechanisms; resulting
in a less expensive and more reliable conveyor transport means.
Food product 310 is placed upon conveyor transport means 399 and cook settings
for
20 product 310 may be inputted automatically or manually, as previously
described, into controller
334. Conveyor indexing motion begins with the opening of ingress tunnel door
398, FIG. 1 and
egress tunnel door 397. After doors 397, 398 open, conveyor transport means
399 moves in a
direction toward the cooking zones, (or zone) a distance such that food
product 310 indexes, or
CA 02558409 2006-09-O1
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moves forward to the first cook zone 380, FIG. 4 within oven tunnel 394. Once
conveyor
transport means 399 stops, doors 398 and 397 close around conveyor belt 399 as
shown in FIG.
7, and initiation of the cooking cycle may begin. After conveyor means 399
comes to its initial
stop, a second food product may be placed on conveyor transport means 399 at
loading position
396, FIG.4. In those instances wherein microwave energy is used, a microwave
seal must be
achieved between conveyor belt 399 and doors 397, 398. Interface wall 387,
FIG. 7 is attached
to belt 399 and doors 397, 398 close around interface wall 387. The wall
spacing on conveyor
belt 399 corresponds to the pitch length (oven zone centerline to oven zone
centerline). The
space between the partitions or walls also defines the landing zone for
product loading area 396,
l0 FIG.4. In addition to obtaining a seal for containment of microwave energy,
closed doors 397,
398 reduce heat losses associated with open cooking tunnel ends where hot gas
leaves the open
tunnel ends with cool ambient gas rushing in to replace the lost hot gas.
The door and wall microwave interface configuration between movable doors 397,
398
and short wall 387, FIG. 7, on conveyor belt 399 is such that neither precise
belt motion control
(stopping at an exact location) or metal to metal contact between door edge
399 and the wall 387
is required. The wall anal belt design is axially compliant. A one quarter
wavelength choke 386,
FIG. 7, is integrated into the bottom edge of doors 397, 398. Allowing for
small displacement of
the wall when the door closes is accomplished by the combination of the
inverted "V" shape
which guides door 398,397 together with short wall 387 by a compliant (not
rigid) connection of
wall 398 to belt 399. The inverted "V" shape has sufficient length to support
a one quarter
wavelength choke (approximately 1.2 inches). The indexing motion of speed
cooking conveyor
appliance 301 results in microwave containment within the cooking tunnel
because the conveyor
is stationary during the cooking process.
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With product 310 now in cook zone 380, controller 334 begins the cooking
recipe for
food product 310. Cooking of food product 310 may be completed within cook
zone 380 or may
be cooked in zones 381 and 382, FIG. 3, and it is not required that food
product 310 utilize all
three cook zones for completed cooking. Indeed, some cook zones may be used to
defrost frozen
food product prior to cooking, or partial defrost followed by. cooking. Dwell,
or cooking time
within each zone as previously described may be altered. The exemplary
embodiment utilizes a
50 second conveyor dwell setting per cooking zone. Food product 310 entering
cook zone 380
may therefore have a cooking recipe of 50 seconds comprised of 25 seconds
wherein 100%
microwave energy and 100% gas flow is applied; followed by 25 seconds in which
50%
to microwave energy and 100% gas flow is applied.
At the completion of the first 50 second dwell period, controller 334 begins
the next
indexing motion by opening tunnel doors 398, 397, FIG. 1 and conveyor
transport means 399
moves, or indexes one pitch length forward, moving product 310 from first cook
zone 380 to
second cook zone 381, FIG. 4. In the event a second food product has been
placed upon
i5 conveyor transport means 399 at loading position 396, FIG. 4, the second
food product will
move, or index into cook zone 380. The second food product's cooking setting
may now be
entered into controller 334 in the event the operator had not previously
entered the cooking
program, or the program had not been automatically loaded as previously
described. Once
conveyor transport means 399 stops, tunnel doors 398, 397 again close and
controller 334
2o executes the cooking settings for the first food product In cook zone 381
and for tl~e second food
product in cook zone 380. Each food product is then cooked with its own
cooking recipe. For
example, the first food product in cooking zone 381 may require 100% gas flow
and no
microwave energy for the 50 second dwell period, while the second food product
in cooking
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zone 380 may have 3 events programmed for the 50 second dwell (e.g., l5
seconds of 100% gas
flow with no microwave followed by 20 seconds of 100°0o microwave
energy and no gas flow,
followed by a final 15 seconds of 50% microwave and 50°fo gas flow).
The number of events per
cooking zone may be programmed in infinite combinations and applicant does not
limit the
endless possible combinations of cooking recipes by the exemplary embodiment.
At the completion of the second 50 second dwell period doors 398, 397 again
open and
the next conveyor transport means indexing motion is initiated. Assuming a
third food product
has been placed upon conveyor transport means 399 in holding area 396, third
food product 310
will index forward to cooking zone 380, while the second food product will
index forward to
1o cooking zone 381 and the first food product will index forward to cooking
zone 382. With the
third food product now in cooking 380, each food product can now be cooked
with its own
cooking recipe setting in the manner as previously described. With the
completion of the third
dwell period, doors 397, 398 again open and conveyor transport means 399
indexes forward one
dwell length and first food product 310 is now outside oven tunnel chamber 394
and resting upon
transport means 399, ready for unloading by the operator.
As previously described, speed cooking conveyor 301 consists of one or more
discrete
cooking zones. The simplest one zone design will process only one product at a
time. A multi-
zone design of 'n' zones would have up to 'n' products in conveyor oven tunnel
at a given time.
The total capacity or speed cooking conveyor throughput (products per hour) is
a function of the
number of cooking zones and the total cook time for a product. For example, a
one zone speed
cooking conveyor with a 150 second dwell time will process approximately 24
products per
hour. A three zone oven with 50 second dwell time zones and a total cook time
of two and one
half minutes (3 X 50 seconds) will process approximately 72 products per hour.
A six zone
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speed cooking conveyor with 25 second dwell times will process approximately
144 products per
hour.
Because the food product is stationary in each cooking zone, the energy flows
imparted
to each food product may be controlled. Control of eriergy to the food product
in a cooking zone
includes the means to modulate both the microwaves, when used, and gas flow
energies that may
be introduced into the food product. A stationary food product during cooking
also permits the
uniform application of the cooking energies (microwave, convective and
optional radiant). Each
cooking zone 380, 381, 382 has open ends with a conveyor belt placed above and
parallel to
cook zone floor 304. The cook zones are placed end to end with the conveyor
transport means
passing through each cook zone and the zones are separate by a distance in
order to minimize the
influence of gas flows or microwave energies coupling between cook zones. The
distances
between cook zones will be determined by the particular conveyor oven that is
desired, and the
amount of interference between cook zones that may be considered acceptable.
Although the exemplary embodiment illustrates the use of a two blower design
with one
blower providing the gas flow to the front of each cook zone and a second
blower for gas flow to
the back of each cook zone, only one flow means, such as a blower may be
utilized, or more than
two gas flow means may be utilized and applicant intends to encompass within
the language any
structure presently existing or developed in the future that performs the same
function.
Equipment bays for housing microwave circuit components, magnetrons, cooling
fans,
electronics, line filters, and other electrical components may be located on
the front side of
appliance 301.
For a three cooking zone speed cooking conveyor oven, approximately 300 cubic
feet/minute ("cfin") is utilized per cooking zone, although more than 300 cfin
and less than 300
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cfin of gas per cooking zone may be utilized. This produces a hot gas flow
supply loop, FIG. 5,
wherein the cook zones are supplied with hot gas flow once cooking zone valves
388x, 388b are
opened. Actuation of the valves may be accomplished using solenoids or stepper
motors 310a,
3 l Ob, FIG. 5, or any other means known to accomplish the function of opening
and closing of
valves 388a, 388b. This method permits the blowers to operate at fixed speeds,
and guarantees
that sufficient flow is always present for safe reliable operation of the gas
heating source and
grease clean-up system.
As previously described, a single energy source, heating means 314, with a
single heat
source controller, is used to supply heat to the gas returning to the blower
316a, 316b. This
to approach greatly simplifies the heating system as compared to distributing
heat sources among
the various cooking zones. High power electrical wiring or natural gas line
connections may also
be centralized. For a gas fueled heating mews, only a single burner and
ignition module are
needed. The centralized approach results in both oven construction
simplification and reduced
maintenance.
Gas heating power requirements per cook zone of the exemplary embodiment are
between approximately 5 and 7 kW for an electric appliance and 24 to 34 kBtu/h
for a direct
fired natural gas powered heater. An electric heater for the exemplary
embodiment is sized
between approximately 15 and 21 kW, while the gas fired gas heater would have
a 72 to 102
kBtu/h need. For either power source, a standard temperature controller could
be employed (i.e.,
2o maintaining the blower discharge temperature). For either a gas fueled or
electric fueled
appliance, as previously described, appliance 301 may be scaled to permit use
of available power
supplies. Additionally, a common gas heating means is ideal for ease of
installation, service, and
the ability to incinerate grease particles that come in contact with the very
hot products of
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combustion. Of course, the hot products of cooking by-product combustion are
mixed with the
gas returning to the blowers, resulting in a modest gas temperature increase
of between 20°F(-
6.67°F) to 60°F (15.56°C) and a number of combustor types
are suitable for this application
including a surface type burner.
Although the present invention has been described in considerable detail with
reference
to certain preferred versions thereof, other versions are possible. For
example, various sizes of
conveyor ovens, both conventional and speed cooking may be made. In these
cases larger or
smaller component parts may be utilized, and fewer or more components may be
employed. In
the case where it is desirable to make a smaller conveyor oven, one gas flow
acceleration means
may be utilized instead of two; one microwave system utilized instead of two;
smaller or fewer
thermal devices, whether electric resistance or gas fired may be used. In
cases wherein it is
desirable for a larger speed cooking oven, larger gas flow systems and
microwave systems may
be added to accomplish a larger speed cooking conveyor oven.
To summarize, the present invention provides for conventional and speed
cooking
conveyor ovens utilizing hot gas flow, and hot gas flow coupled with microwave
energy in order
to achieve conventional and speed cooking of food products. Conventional or
speed cooking of
food products five to ten times faster than conventional cooking with food
quality, taste and
appearance levels equal to and higher than that attained by conventional
cooking. The speed
cooking conveyor oven is operable on various power supplies and is simple and
economical to
manufacture, use and maintain, and is directly scalable to larger or smaller
embodiments. The
conveyor oven may operate as a gas fired, electric resistance fired oven, a
microwave oven or a
combination gas and microwave oven. Additionally, the invention may be
practiced wherein no
gas deflection means are utilized, such as in the exemplary embodiment, gas
deflection means
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are utilized as in alternate embodiments described herein. In cases wherein it
is desirable for a
larger production conveyor oven, multiple conveyors may be used with
additional gas flow
system and microwave systems
Other modifications and improvements thereon will become readily apparent.
Accordingly, the spirit and scope of the present invention is to be considered
broadly and limited
only by the appended claims, and not by the foregoing specification. Any
element in a claim that
does not explicitly state "means for" performing a specific function, or "step
for" performing a
specific function, is not to be interpreted as a "means" or "step" clause as
specified in 35 U.S.C.
~ 112, ~[6. In particular, the use of "step of in the claims herein is not
intended to invoke the
l0 provisions of 35 U.S.C. ~ 112.
42
