Note: Descriptions are shown in the official language in which they were submitted.
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FORCED AIR PESTICIDE VAPORIZER WITH HEATSINK VAPORIZATION
CHAMBER AND OFFSET EXHAUST CHAMBER
FIELD OF THE INVENTION
The present invention relates generally to beekeeping tools and
vaporizing devices, and more particularly to forced air pesticide vaporizers
to deliver
vaporized oxalic acid to bee hives for the purpose of exterminating varroa
mites.
BACKGROUND
Vaporizers operable to perform sublimation of oxalic acid crystals and
application of the resulting vapour to beehives for the extermination of
varroa mites are
known. Some of the known devices included forced-air units for blowing the
generated
vapor into the hive.
For example, U.S. Patent 7,578,722 discloses a forced air vaporization
and dispensing apparatus using a fan to help dispense the vaporized oxalic
acid into a
bee hive.
U.S. Patent 9,655,346 instead relies on connection of a separate air
compressor to a wand-like vaporization and dispensing tool. The oxalic acid is
loaded
into a primary tube of the tool at a proximal end thereof, and vaporized in
the same tube
by a heater coil wrapped around the opposing distal end of the tube.
Pressurized air is
introduced to the tube by a pair of nozzles at an intermediate location along
the tube so
that this forced air will blow the resulting oxalic acid vapor through a
diffuser at the distal
end. A screen near the distal end of the tube captures the crystals to prevent
them
from escaping the tube before they are vaporized.
However, there remains room for improvement, and Applicant has
developed a new pesticide vaporization and dispensing tool with a unique
combination
of features not shown or suggested by the prior art.
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SUMMARY OF THE INVENTION
According to one aspect of the invention, there is provided an apparatus
for vaporizing and dispensing a pesticide agent, said apparatus comprising:
an elongated body structure having a proximal end, an opposing distal
end and a delivery passage running longitudinally of the elongated body
structure to
the distal end thereof;
a heatsink of thermally conductive material attached to said elongated
body structure at the distal end thereof and comprising a hollow interior into
which the
delivery passage of the elongated body structure opens at the distal end
thereof;
a loading port on the elongated body structure at or proximate the
proximal end thereof for introduction of solid pesticide material into the
delivery passage
for delivery onward therethrough to the hollow interior of the heatsink;
a heater operably arranged with the heatsink to vaporize the solid
pesticide material received in the hollow interior of the heatsink through the
elongated
body structure; and
a vapour outlet fluidly communicating the hollow interior of the heatsink to
an exterior environment to exhaust the vaporized pesticide from the apparatus
to a
targeted treatment area.
Preferably the heatsink exceeds the elongated body structure in wall
thickness.
Preferably the heatsink comprises a bored-out solid body of said thermally
conductive material.
Preferably the thermally conductive material of the heatsink is aluminum.
Preferably the thermally conductive material of the heatsink has greater
thermal conductivity than a constituent material of the elongated body
structure.
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Preferably the proximal and distal ends of the elongated body structure
are separated in an axial direction, the hollow interior of the heatsink
comprises a
vaporization chamber and an exhaust chamber, the vaporization chamber has a
first
open end into which the delivery passage opens and a closed second end axially
opposite the first open end, and the exhaust chamber is radially offset from
the
vaporization chamber and is fluidly communicated therewith near the first end
thereof.
Preferably the exhaust chamber communicates with the vaporization
chamber and the vapor outlet adjacent axially opposing ends of said exhaust
chamber.
Preferably the chambers are in fluid communication with one another only
at areas thereof adjacent the distal end of the elongated body structure.
Preferably the chambers comprise respective cylindrical bores.
Preferably the respective cylindrical bores of the chambers are fluidly
communicated with one another at a counter-bored end of the heatsink.
Preferably the heater is disposed circumferentially around both the
vaporization chamber and the exhaust chamber.
Preferably the heater is a band heater defining a cylindrical shell around
the heatsink.
Preferably there is a temperature sensor operably installed on the
heatsink to monitor temperature conditions thereof and connected to a
controller
.. arranged to automatically control the heater in response to detected
changes in said
temperatures conditions.
According to another aspect of the invention, there is provided an
apparatus for vaporizing and dispensing a pesticide agent, said apparatus
comprising:
an elongated body structure having a proximal end, an opposing distal
end spaced therefrom in an axial direction and a delivery passage running
longitudinally
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of the elongated body structure to the distal end thereof;
a vaporization chamber carried at the distal end of the elongated body
structure, where the delivery passage of the elongated body structure opens
into said
vaporization chamber;
a loading port on the elongated body structure at or proximate the
proximal end thereof for introduction of solid pesticide material into the
delivery passage
for delivery onward therethrough to the vaporization chamber;
a heater operably arranged with the vaporization chamber to vaporize the
solid pesticide material received therein through the delivery passage to
generate a
pesticidal vapour; and
an exhaust chamber for receiving the pesticidal vapour from the
vaporization chamber; and
a vapour outlet fed by the exhaust chamber to exhaust the pesticidal
vapour from the apparatus to a targeted treatment area;
wherein the vaporization chamber has a first open end into which the
delivery passage opens and a closed second end axially opposite the first open
end,
and the exhaust chamber is radially offset from the vaporization chamber and
is fluidly
communicated therewith near the first end thereof.
Preferably the exhaust chamber communicates with the vaporization
chamber and the vapor outlet adjacent axially opposing ends of said exhaust
chamber.
Preferably the chambers are in fluid communication with one another only
at areas thereof adjacent the distal end of the elongated body structure.
Preferably the chambers comprise respective cylindrical bores in a
shared body of material.
Preferably the respective cylindrical bores of the chambers are fluidly
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communicated with one another at a counter-bored end of the shared body of
material.
Preferably there is a forced air system for pressurized conveyance of the
pesticidal vapour from the vaporization chamber to the vapour outlet via the
exhaust
chamber, said forced air system comprising a nozzle arranged to introduce a
supply of
pressurized air into the delivery passage and direct said supply of
pressurized air
through said delivery passage to the vaporization chamber.
Preferably said nozzle is an only nozzle of said forced air system, which
further comprises two different supply branches that both feed said only
nozzle, one of
said branches comprising a burst control valve operable from a normally closed
state
to an open state to momentarily open said one said branches to augment a
steady
supply of air through the other branch with a momentary burst of additional
air.
BRIEF DESCRIPTION OF THE DRAWINGS
One embodiment of the invention will now be described in conjunction
with the accompanying drawings in which:
Figure 1 is a perspective view of a pesticide vaporizing and dispensing
apparatus of the present invention.
Figure 2 is a perspective view of an elongated main body structure of the
apparatus of Figure 1.
Figure 3 is a top plan view of the main body structure of Figure 2.
Figure 4 is a side elevational view of the main body structure of Figure 3.
Figures 5A through 5F are cross-sectional views of the main body
structure of Figures 3 and 4, as viewed from lines A ¨ A through F ¨ F
thereof,
respectively.
Figure 6 is a perspective view of a heatsink chamber body of the
.. apparatus of Figure 1.
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Figure 7 is a side elevational view of the heatsink chamber body of Figure
6.
Figure 8 is an end elevational view of the heatsink chamber body of Figure
6.
Figures 9A and 9B are cross-sectional views of the heatsink chamber
body as viewed along lines A ¨A and B ¨B thereof, respectively.
Figure 10 is a schematic diagram of a forced air system of the apparatus
of Figure 1.
Figure 11 is an enlarged partial top plan view of the apparatus of Figure
1.
Figure 11A is a partial cross-sectional view of the apparatus of Figure 11
as viewed along line A ¨ A thereof, and includes schematically illustrated
travel paths
followed by solid pesticide material, resulting vapor and pressurized air from
the forced
air system of Figure 10 during use of the apparatus.
DETAILED DESCRIPTION
Figure 1 illustrates an apparatus of the present invention designed for
vaporization of oxalic acid crystals and forced-air dispensing of the
resulting oxalic acid
vapor into a beehive in order to exterminate varroa mites. Though framed
herein with
this particular purpose in mind, it will be appreciated that the apparatus may
be similarly
.. employed for the vaporization and forced air dispensing of other initially
solid pesticide
agents in a vaporized state.
The fully assembled apparatus is made up of a elongated wand-like main
body structure 10, a heatsink chamber body 12 affixed to an end of the main
body
structure 10, and a band heater 14 affixed to the main body structure near the
same
.. end thereof so as to enclose around the heatsink chamber body in manner
operable to
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elevate the heatsink temperature to a suitable range to vaporize the oxalic
crystals
loaded into the apparatus.
Referring to Figures 2 through 5, the main body structure 10 features a
primary tube 16 in the form of a rigid length of pipe extending linearly on a
central
longitudinal axis 18 from a proximal end 20 of the main body structure to an
axially
opposing distal end 22. The primary tube 16 is hollow throughout, and open at
both
the proximal and distal ends. The open proximal end 20 of the tube 16 serves
as a
loading port through which oxalic acid crystals are loaded into the apparatus
in their
original solid state for subsequent vaporization of these crystals inside the
apparatus.
A control unit housing 24 is affixed to the primary tube 16 at an
intermediate location between the proximal and distal ends thereof, more
particularly at
a location nearer to, but spaced from, the proximal end 20. The proximal
portion 16a
of the tube 16 left exposed between the control unit housing 24 and the
proximal end
of the tube 16 defines a hand grip area for manual support of the apparatus in
a wand-
like fashion. At the opposing distal end 22 of the primary tube 16, a heatsink
mounting
flange 26 is defined by a round annular plate that projects radially outward
from around
the open distal end 22 of the primary tube 16. The heatsink mounting flange 26
features
bolt holes 27a therein on opposite sides of the primary tube 16 for bolted
fastening of
the heatsink chamber body 12 to the distal end of the main body structure. The
heatsink
mounting flange 26 is non-concentric with the primary tube 16, as perhaps best
shown
in Figure 5A, where the central longitudinal axis 18 of the primary tube 16
clearly does
not coincide with the center of the circular mounting flange 26. The primary
tube 16 is
thus offset from the center of the flange 26 to reside nearer to one side of
the flange's
circular outer periphery than to a diametrically opposite side thereof.
Spaced a short axial distance along the primary tube 16 from the heatsink
Date Recue/Date Received 2022-02-22
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mounting flange 26 is a heater mount 28 that likewise features a round annular
plate
28a projecting radially outward from the primary tube 16 in non-concentric
relation
thereto. The centers of the heatsink mounting flange 26 and the heater mount
share
are aligned with one another on a shared central axis that is radially offset
from, but
parallel to, the central longitudinal axis 18 of the primary tube 16. The
heater mount 28
also features a short cylindrical collar 28b mounted concentrically on the
annular plate
28a near the outer circumference thereof. The collar 28b reaches toward the
heatsink
mounting flange 26. In the fully assembled state of the apparatus, one end of
the
cylindrical band heater 14 fits externally over the collar 28b to support the
band heater
14 on the main body structure 10.
As shown in the drawings, a stiffening fin 29 is affixed to the primary tube
16 at the portion thereof between the heatsink mounting flange 26 and the
heater mount
29. The stiffening fin projects radially from the primary tube 26 to the same
side thereof
to which the heatsink mounting flange 26 is offset from the longitudinal axis
18 of the
primary tube. The fin 29 reaches the distal end of the tube 16, where the fin
is affixed
to the heatsink mounting flange 26, and serves as a stiffening gusset between
the
primary tube 16 and the heatsink mounting flange 26 to help support the weight
of the
heatsink by resisting deflection between the tube and the mounting flange 26.
Figure 6 illustrates the heatsink chamber body 12, which is a unitary solid
body of heat conductive material such as brass or aluminum. While a brass
heatsink
is known to be more thermally conductive than aluminum, thus forming a more
effective
heatsink, aluminum is often more preferable in the interest of a more cost-
effective
construction. The heatsink chamber body 12 of the illustrated embodiment has a
cylindrical outer shape, though the external shape may vary in other
embodiments. The
heatsink chamber body 12 has an axial length that is measured parallel to the
central
Date Recue/Date Received 2022-02-22
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longitudinal axis 18 of the primary tube 16 and the shared central axis of the
heatsink
and heater mounts 26, 28. This axial length of the heatsink chamber body
exceeds its
width or diameter, which is measured orthogonally of axial length in planes
normal
thereto.
The heatsink chamber body 12 has two axial bores machined therein,
each defining a respective cylindrical chamber within the heatsink chamber
body 12. A
larger-diameter one of these two axial bores defines a vaporization chamber 30
for
receiving the oxalic acid crystals loaded into the apparatus, and holding
these crystals
during sublimation thereof into a vaporized state. The smaller-diameter bore
defines
an exhaust chamber 32 through which the vaporized oxalic acid is subsequently
exhausted from the vaporization chamber 30.
The exhaust chamber 32 is a through-bore that fully spans the axial length
of the heatsink chamber body 12 from one end thereof to the other. On the
other hand,
the vaporization chamber 30 is a blind-bore that opens into the heatsink
chamber body
only at the attachment end 34 thereof that is affixed to the heatsink mounting
flange 26
in the assembled state of the apparatus. The vaporization chamber 30 stops
short of
the axially opposing discharge end 36 of the heatsink chamber body 12. The
vaporization chamber thus has a closed end wall 30a preventing solid oxalic
acid
crystals or vaporized oxalic acid from axially exiting the vaporization
chamber through
the discharge end 36 of the heatsink chamber body 12. Both chambers 30, 32 are
therefore open at the attachment end 34 of the heatsink body 12, while only
the exhaust
chamber 32 is open at the discharge end 36 of the heatsink body. The
attachment end
34 of the heatsink chamber body 12 has an enlarged counterbore 38 recessed
axially
therein and at least partially overlapping both the vaporization chamber 30
and the
exhaust chamber 32. Accordingly, the two chambers 30, 32 are fluidly
communicated
Date Recue/Date Received 2022-02-22
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with one another in a radial direction at this counterbored area 38. Over the
entire axial
remainder of the of the vaporization chamber 30 reaching from the counterbored
area
38 to the closed end 30a of the vaporization chamber, the two chambers 30, 32
are
physically isolated from one another by a solid divider wall portion 40 of the
heatsink
body that remains intact between the two chambers 30, 32.
Neither of the two chambers is concentric with the outer cylindrical shape
of the heatsink chamber body 12, each instead being nearer to a respective one
of two
diametrically opposing sides thereof. In the fully assembled state of the
apparatus, the
cylindrical shape of the heatsink chamber body is centered on the shared
central axis
of the heatsink and heater mounts 26, 28, while the cylindrical shape of the
vaporization
chamber 30 is centered on the central longitudinal axis 18 of the primary tube
16.
The counterbore 38 of the illustrated embodiment has a keyslot shape,
with an enlarged circular upper lobe 38a that is centered on the same axis as
the
vaporization chamber and is of similar diameter thereto, and a U-shaped bottom
stem
.. 38b that juts radially from the circular lobe and has a narrower width of
similar measure
to the diameter of the smaller-bore exhaust chamber 32. The curved outer end
of the
U-shaped stem 38b generally conforms with the semi-cylindrical bottom half of
the
exhaust chamber 32 that lies furthest from the vaporization chamber 30.
The attachment end 34 of the heatsink cavity body 12 also features a pair
.. of bolt holes 27b on opposite sides of the counterbore 38. These bolt holes
27b are
sized and positioned to align with the bolt holes 27a on the heatsink mounting
flange
26. The heatsink cavity body 12 is thus bolted to the heatsink mounting flange
26, and
the hollow interior of the primary tube 16 opens into the larger circular lobe
38a of the
counterbore 38, which is of equal or similar diameter to the primary tube 16.
The
primary tube 16 stops short of, or only partially reaches into, the
counterbore 38 so as
Date Recue/Date Received 2022-02-22
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not to obstruct fluid communication between the two chambers 30, 32 of the
heatsink
via the counterbore 38. That is, the counterbore leaves a gap 43 between the
divider
wall portion 40 of the heatsink body 12 and the face of the heatsink mounting
flange
26, which abuts against the attachment end 34 of the heatsink chamber body 12.
This
gap 43 thus serves as a radial port between the two chambers by which vapor
from the
vaporization chamber can flow into the exhaust chamber, as described in more
detail
further below.
In addition to the blind bolt holes 27b, the attachment end 34 of the
heatsink cavity body 12 also features an additional blind mounting hole 42
therein at a
radial distance outward from the counterbore 38 to accommodate mounting of a
thermocouple or other temperature sensor within the solid heatsink chamber
body 12
at a location near but outside the vaporization chamber 30. The opposing
discharge
end 36 of the heatsink chamber body 12 features another set of blind bolt
holes 27c
therein.
Turning back to Figure 1, the cylindrical band heater 14 has one end
slipped over and fastened to the collar 28b of the heater mount 28. The band
heater
14 has an axial length generally equal to the distance from the flange 28a of
the heater
mount 28 to the discharge end 36 of the heatsink cavity body 12. Here, an end
cap 46
of similar structure to the heater mount 28 has a circular end plate 46a
overlying the
discharge end 36 of the heatsink cavity body, and a cylindrical collar 46h
jutting a short
axial distance back toward the matching collar 28b of the heater mount 28.
This collar
46b circumferentially receives the second end of the band heater 14, and is
fastened
thereto. The cylindrical band heater 14 thus circumferentially surrounds the
heatsink
chamber body 12 over the full axial length thereof. A diffuser 48 is attached
to the end
plate 46a of the end cap 46 to serve as the final outlet of the vaporized
oxalic acid from
Date Recue/Date Received 2022-02-22
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the apparatus. The diffuser or other output is fluidly communicated with the
open
discharge end of the exhaust chamber 32 of the heatsink chamber body 12 via
one or
more holes in the end plate 46a. The end plate features a pair of bolt holes
27d passing
therethrough, one of which is visible in Figure 1. These bolt holes 27d that
align with
the bolt holes 27c in the discharge end 36 of the heatsink chamber body 12 for
fastening
of the end cap 46 thereto.
A communications cable 50 runs from the control unit housing 24 to the
heater mount 28, and carries internal wiring (not shown) that connects up with
the band
heater 14 and the temperature sensor in the mounting hole 42 of the heatsink
chamber
body 12 in order to control operation of the heater 14. A temperature control
module in
the control unit housing 24 is responsible for such heater control, and shown
may
include an indicator 52 viewable at the exterior of the control unit housing
24 so that an
operator can be sure a sufficient operating temperature is present in the
heatsink to
achieve sublimation of the oxalic acid in the vaporization chamber. In the
illustrated
embodiment, the control indicator 52 is a temperature readout screen operable
to show
the actual temperature detected by the temperature sensor, though in other
embodiments, a more simplistic display simply switching between "ready" and
"unready" indicators may be employed (e.g. using differently coloured
indicator lamps,
such as light emitting diodes (LEDs)). Pushbuttons or other operator controls
54 may
also be included as part of the heater control module for operator-based
selection of
suitable operating temperature setpoints.
The control unit enclosure 24 also incorporates elements of a forced air
system for pressurized conveyance of the vaporized oxalic acid from the
apparatus
through the diffuser 48 or other final output point at the discharge end 36 of
the heatsink
chamber body 12. For the such purpose, the illustrated embodiment includes a
Date Recue/Date Received 2022-02-22
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pneumatic connection fitting 56 mounted to the control unit enclosure 24 to
accept
connection of an air hose from an external air compressor to provide a
pressurized air
supply to the apparatus. With reference to Figure 5F, the forced air system
further
includes a nozzle 58 that penetrates through the wall of the primary tube 16
from the
interior of the control unit enclosure 24, and points axially toward the
distal end 22 of
the primary tube 16 in order to direct pressurized air received from the
connection fitting
56 downstream toward the heatsink chamber body 12.
Figure 10 shows a schematic diagram of the forced air system. An intake
airflow path 59 from the connection fitting 56 splits into two parallel
branches 59a, 59b
each containing a respective flow control valve 60a, 60b for adjusting airflow
through
the respective branch 59a, 59b. Downstream of these valves 60a, 60b the two
branches 59a, 59b join back together to provide a singular path 61 to the
nozzle 58
inside the primary tube 16. One branch 59a is always open, and thus serve as a
continuous flow branch providing a steady, ongoing stream of pressurized air
into the
.. primary tube 16 via the nozzle 58. The other branch 59b is a normally-
closed burst-
control branch featuring a normally closed on/off valve 62 that is situated
downstream
of the respective flow control valve 60b. The on/off valve 62 can be
temporarily opened
by an operator of the apparatus to allow supplementary flow through this
second branch
59b in order to augment the continuous airflow through the first branch 59a,
thus
creating an extra burst of air pressure through the nozzle 58 when the on/off
valve 62
is opened.
Figure 1 shows a pair of valve adjustment actuators in the form of
rotatable adjustment knobs 64 disposed atop the control unit enclosure 24 for
respective manual adjustment of the flow control valves 60a, 60b. An open-
close valve
actuator in the form of a thumb lever 66 is also disposed atop the control
unit at the end
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thereof nearest the hand grip portion 16a of the primary tube 16 in order to
momentarily
open the on/off valve 62 when depressed by the thumb of the operator's hand on
this
hand grip portion 16a of the primary tube. A power switch connected to the
heater
control module for activation and deactivation of the heater is also provided,
for example
in the form of a toggle switch 66 also mounted atop the control unit
enclosure.
In use of the apparatus, the operator holds the grip portion 16a of the
primary tube 16 in one hand and tips the opposing heater-equipped distal end
22 of the
primary tube downward toward ground level to achieve a down-turned orientation
of the
primary tube 16. Oxalic acid crystals are introduced into the primary tube 16
via the
loading port at the open proximal end of the tube 16, and, shown by the solid
line arrow
in Figure 11A, the oxalic acid gravitationally falls through the downturned
primary tube
16, past the nozzle 58 and onward through the open distal end 22 of the
primary tube
16. Since this distal end of the primary tube opens into the vaporization
chamber 30 of
the heatsink chamber body 12, the crystals fall down into the vaporization
chamber 30,
past the gap space 43 at the counterbore that opens radially from the
vaporization
chamber 30 into the exhaust chamber 32. The hollow interior of the primary
tube 16
thus defines a delivery passage for routing the oxalic acid crystals into the
vaporization
chamber from a loading port situated remotely thereof to keep the operators
hands far
from the high operating temperatures at the vaporization chamber. The
delivered
crystals settle against the closed end 30a of the vaporization chamber 30. The
heat
imparted to the heatsink chamber body 12 by the band heater 14 is transferred
to the
received oxalic acid crystals, causing same to undergo sublimation within the
vaporization chamber 30.
Meanwhile, the nozzle 58 of the forced air system provides a steady
stream of air through the primary tube 16 into the heatsink chamber body 12.
Since
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the end 30a of the vaporization chamber is closed, the air being pumped into
the
heatsink chamber body 12 and the vapor resulting from the sublimation of the
oxalic
acid will exit the heatsink chamber body 12 through the gap space 43 that
exits between
the two chambers at the counterbored area 38 of the heatsink body's attachment
end
34, as shown by the long-dash broken line in Figure 11A. The pressurized state
of the
primary tube 16 due to the ongoing stream of air introduced through the nozzle
58
prevents the vaporized oxalic acid from moving upstream into the tube 16. The
air
stream thus instead forces the vaporized oxalic acid into the lower-pressure
environment outside the apparatus via the gap space 43, exhaust channel 32 and
outlet
diffuser 48, as shown by the short-dash broken line in Figure 11A.
On an ongoing basis throughout this process, the temperature sensor is
actively sampling the temperature of the heatsink chamber body 12 near the
vaporization chamber 30, which is in turn read by the heat control module This
control
module then determines if the temperature is above or below a predetermined or
programmable set-point (e.g. a user customized setpoint adjusted via controls
54). If
the detected temperature of the heatsink 12 is below the setpoint, the control
module
activates the heater 14 until the heatsink set-point temperature is reached. A
PID
controller may be used to reduce overshoot of the setpoint temperature.
The use of a separate heatsink to define the vaporization chamber, rather
than using a distally situated portion of the primary tube 16 itself, provides
notable
advantage in that the heatsink can store a substantial amount of heat energy
therein,
reducing difficulties in maintaining a relatively constant temperature in the
vaporization
chamber despite the high amount of heat energy required to vaporize the
initially solid
substance. The improved heat storage capacity of the heatsink chamber body
compared to the primary tube 16 can be attributed to both the dramatically
thicker walls
Date Recue/Date Received 2022-02-22
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surrounding the vaporization chamber versus the much thinner pipe walls of the
primary
tube 16, and the optional use of more thermally conductive material (e.g.
brass,
aluminum, etc.) for the heatsink chamber body versus the primary tube 16,
whose
constituent material(s) (e.g. steel) may be less thermally conductive to
reduce risk of
burn or discomfort to the user by minimizing heat transfer from the heater-
carrying distal
end of the primary tube to the hand grip and loading portion 16a of the
primary tube at
the proximal end.
This solid to vapor state change (sublimation) can thus draw on the stored
energy in the heatsink 12 so that the temperature doesn't drop as much during
sublimation. This allows continuous use without large delays, as the
vaporization
chamber can use the stored heat rather than waiting for the heater to catch up
with the
energy consumption of the sublimation process. Also, since the thermally
conductive
heatsink provides relatively uniform temperature distribution throughout,
accurate
sampling of the vaporization chamber temperature can be achieved without
having the
thermocouple or other sensor in an exposed position in the chamber, where
exposure
to the acid would be corrosive and detrimental to accurate long-term
temperature
sampling.
Additionally, by placing the exhaust chamber in radially offset relation to
one side of the vaporization chamber, rather than prior art configurations in
which the
.. air and vapor flow axially straight through a screened end of vaporization
chamber into
an inline-exhaust that is merely an axial extension of the same pipe that
forms the
vaporization chamber, the sold oxalic acid crystals fall directly against a
solid, thermally
conductive surface at the closed end 30a of the vaporization chamber, thus
exposing
the crystals to a greater amount of direct, conductive heat transfer than
would be
.. provided at a mesh screen surface.
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Since various modifications can be made in my invention as herein above
described, and many apparently widely different embodiments of same made, it
is
intended that all matter contained in the accompanying specification shall be
interpreted
as illustrative only and not in a limiting sense.
Date Recue/Date Received 2022-02-22
