U.S. patent application number 11/685642 was filed with the patent office on 2008-05-08 for frost management system for a refrigerated cabinet.
Invention is credited to Greg HALL, James SCOTT, Marian VIDOVIC.
Application Number | 20080104973 11/685642 |
Document ID | / |
Family ID | 38952128 |
Filed Date | 2008-05-08 |
United States Patent
Application |
20080104973 |
Kind Code |
A1 |
HALL; Greg ; et al. |
May 8, 2008 |
FROST MANAGEMENT SYSTEM FOR A REFRIGERATED CABINET
Abstract
A frost management system for use in a refrigeration cabinet
having a base and sidewalls defining an opening to provide access
into the refrigeration cabinet. A heating member is positioned
proximate to the opening exterior of the sidewalls for heating of
frost accumulated on the sidewalls. The first heating member may be
activated for a time to cause accumulated frost to be melted,
thereby permitting the resulting liquid to flow down the sidewalls
toward the base and be refrozen. For full defrost operation of the
device, there may be a second heating member positioned proximate
to the base of the refrigeration cabinet. The second heating member
may be activated to heat a portion of the ice to enable its
removal. There is also disclosed a method for managing frost in a
refrigeration cabinet.
Inventors: |
HALL; Greg; (Guelph, CA)
; VIDOVIC; Marian; (Mississauga, CA) ; SCOTT;
James; (Cambridge, CA) |
Correspondence
Address: |
OSTROLENK FABER GERB & SOFFEN
1180 AVENUE OF THE AMERICAS
NEW YORK
NY
100368403
US
|
Family ID: |
38952128 |
Appl. No.: |
11/685642 |
Filed: |
March 13, 2007 |
Current U.S.
Class: |
62/80 ;
62/140 |
Current CPC
Class: |
F25D 21/08 20130101 |
Class at
Publication: |
62/80 ;
62/140 |
International
Class: |
F25D 21/00 20060101
F25D021/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 17, 2006 |
CA |
2,552,454 |
Claims
1. A frost management system for use in a refrigeration cabinet
having a base and sidewalls defining an opening to provide access
into the refrigeration cabinet, the sidewalls being conductive for
heat transfer through the sidewalls, comprising: a first heating
member positioned proximate to the opening and exterior of the
sidewalls for heating of frost accumulated on an interior of the
sidewalls; and a first activator for the first heating member,
wherein the first heating member is activated for a time to cause
accumulated frost to be melted, thereby permitting the resulting
liquid to flow down the sidewalls toward the base and be
refrozen.
2. The frost management system of claim 1, further comprising: a
second heating member positioned proximate to the base of the
refrigeration cabinet and exterior of the sidewalls for heating of
ice accumulated on the interior of the sidewalls; and a second
activator for the second heating member, the second heating member
being activated for a time to melt a portion of the ice adjacent
the sidewalls to enable its removal.
3. The frost management system of claim 1, wherein the first
heating member comprises a foil heater having a first conductive
sheet, a second conductive sheet having a surface adhered to a
surface of the first conductive sheet, and a wire heater located
between the first conductive sheet and second conductive sheet for
heating the first conductive sheet and second conductive sheet.
4. The frost management system of claim 3, wherein the foil heater
has an adhesive surface for adhering to the sidewalls.
5. The frost management system of claim 3, wherein the wire heater
is positioned in a serpentine configuration between the first
conductive sheet and second conductive sheet.
6. The frost management system of claim 1, further comprising a
cooling member located exterior the sidewalls for cooling the
interior of the sidewalls through heat transfer through the
sidewalls.
7. The frost management system of claim 6, further comprising a
controller for automatically effecting a predetermined cycle of
operation for the cooling member and the first activator at
predetermined intervals.
8. The frost management system of claim 6, wherein the
predetermined intervals are regular intervals.
9. The frost management system of claim 7, wherein the regular
intervals are 12-hour intervals.
10. A method for managing frost on a refrigeration cabinet having a
base and sidewalls defining an opening to provide access into the
refrigeration cabinet, including the step of: heating a region on
the sidewalls proximate to the opening for melting frost
accumulated on an interior of the sidewalls into a liquid, thereby
permitting the resulting liquid to flow down the sidewalls toward
the base and be refrozen.
11. The method of claim 8, including the step of: heating a region
on the sidewalls for melting a portion of ice accumulated on the
interior of the sidewalls to enable its removal; and removing the
ice from the refrigeration cabinet.
12. The method of claim 11, wherein the step of heating a region on
the sidewalls proximate to the opening is on a predetermined cycle
of operation at predetermined intervals.
13. The frost management system of claim 12, wherein the
predetermined intervals are regular intervals.
14. The frost management system of claim 13, wherein the regular
intervals are 12-hour intervals.
15. The frost management system of claim 2, wherein the first
heating member comprises a foil heater having a first conductive
sheet, a second conductive sheet having a surface adhered to a
surface of the first conductive sheet, and a wire heater located
between the first conductive sheet and second conductive sheet for
heating the first conductive sheet and second conductive sheet.
Description
FIELD OF THE INVENTION
[0001] This invention relates to refrigerated cabinets such as
chest freezers and, in particular, to frost management systems for
such devices.
BACKGROUND OF THE INVENTION
[0002] In refrigeration cabinets such as cold-wall freezers, a
principal concern is the accumulation of frost on the inside liner
walls. The formation of frost within the freezer may cause
refrigeration system degradation, loss of cooling efficiency,
cleanability and aesthetic issues. Freezer accessories such as
baskets may be "locked" into position by frost accumulation.
Freezers with frost accumulation may provide the impression that
the last cleaning was prior to the frost accumulation. Conventional
defrost systems may create a dry humidity environment which may
adversely effect food products, such as ice cream.
[0003] A principal concern with frost is that it may form an
insulating cushion between the cooling evaporator tubing coils and
an interior portion of the cabinet. This insulating cushion reduces
heat transfer efficiency in the evaporator tubing coils through the
inner walls of the cabinet and impedes proper air circulation of
refrigerated air above the freezer contents, which frequently is
food.
[0004] The cabinets of cold-wall type freezers may for example be
of the vertical closed type construction with insulated hinged
solid or glass doors. The cabinets may also for example be of the
horizontal open or closed type with solid insulated hinged, glass
hinged or sliding glass lids. In vertical type freezers with hinged
doors the warm ambient air is drawn into the freezer cabinet with
every door opening. Higher density cooler air escapes with each
door opening by dropping down to ground level. As the cool air
flows down and out of the freezer, warmer moist air is drawn into
the cabinet to make up the difference in air pressure within the
freezer. In horizontal chest freezers the warmer low pressure
ambient air is drawn into the freezer cabinet with each lid opening
due to pressure differences between the cold low pressure air
inside the freezer and the warmer higher pressure ambient air
surrounding the freezer cabinet. The moisture from the ambient air
drawn into the cabinet will condense along the inside liner walls
in the form of frost. The frost accumulates preferentially along
the liner walls in the open volume area between the upper level of
the freezer contents and top of the freezer chest liner.
[0005] Conventional freezer defrosting requires a user to remove
frozen food or other products contained within the freezer cabinet,
followed by turning off the compressor. Frost is removed by melting
with placement of a fan directed into the cabinet, spraying warm
water on the cabinet walls, or simply letting the cabinet sit for a
number of hours with the lid open to the ambient air.
[0006] Another defrosting method is to scrape frost off the cabinet
walls without increasing the ambient temperature. A difficulty with
this method is that it must be frequently done, and even so
scraping may be physically demanding or cumbersome for the user.
There is also a risk of damaging the freezer liner.
[0007] Yet another defrosting method is to use hot gas installed
within the cabinet walls. In a defrost cycle of this method, there
is a sudden release of hot high-pressure refrigerant gas into the
extremely cold evaporator tubing for melting of the frost. Hot gas
defrosting may require integration with refrigeration circuits,
thus failure of one circuit may lead to mass failure of the
apparatus. Hot gas defrosting may be costly to manufacture and
install. There may be compressor failure if the defrost cycle is
too long or if the hot gas solenoid valve is left on due to
malfunction thereby resulting in compressor winding overheating and
eventual burn out.
SUMMARY OF THE INVENTION
[0008] The present invention provides to a frost management system
for use in a refrigerated cabinet such as a cold-wall freezer which
addresses the shortcomings of prior devices.
[0009] In a first aspect, the invention provides a frost management
system for use in a refrigeration cabinet having a base and
sidewalls defining an opening to provide access into the
refrigeration cabinet, the sidewalls being conductive for heat
transfer through the sidewalls. There is a first heating member
positioned proximate to the opening exterior of the sidewalls which
may be activated to melt frost accumulated on an interior of the
sidewalls. A first activator is provided for the first heating
member, the first heating member being activated for a time to
cause the frost to be melted, thereby permitting the resulting
liquid to flow down the sidewalls toward the base and be refrozen.
In another aspect, the invention provides a second heating member
positioned proximate to the base of the refrigeration cabinet and
exterior of the sidewalls for heating of ice accumulated on the
sidewalls. There is provided a second activator for the second
heating member. The second heating member is activated for a time
to melt a portion of the ice adjacent the sidewalls to enable its
removal.
[0010] In yet another aspect, the invention provides a method for
managing frost in a refrigeration cabinet having a base and
sidewalls defining an opening to provide access into the
refrigeration cabinet, including the step of heating a region on
the sidewalls proximate to the opening for melting frost
accumulated on an interior of the sidewalls into a liquid, thereby
permitting the resulting liquid to flow down the sidewalls toward
the base and be refrozen. In another aspect, a full defrost may be
initiated by heating a lower portion and/or an upper portion of the
sidewalls for melting a surface of the ice, and mechanically
removing the ice from the refrigeration cabinet.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] Embodiments will now be described by way of example with
reference to the accompanying drawings, through which like
reference numerals are used to indicate similar features.
[0012] FIG. 1 shows a perspective sectional view of a horizontal
cold-wall type freezer in accordance with an embodiment of the
present invention;
[0013] FIG. 2 shows a perspective partial sectional view of a
cabinet wall of FIG. 1;
[0014] FIG. 3 shows a perspective view of a foil heater of the
freezer of FIG. 1 and a block diagram of an example of controller
circuitry;
[0015] FIG. 4 shows a sectional side view of the freezer of FIG.
1;
[0016] FIG. 5 shows the same view as FIG. 4 in a first mode of
operation,
[0017] FIG. 6 shows the same view as FIG. 4 in a second or full
defrost mode of operation; and
[0018] FIG. 7 shows a perspective sectional view of a vertical
cold-wall type freezer in accordance with another embodiment of the
present invention.
DETAILED DESCRIPTION
[0019] For clarity, "frost" may mean any deposition of vapors in
saturated air, including water vapors, and may include ice-like or
other crystalline formations. Usually, frost includes air or
gas-filled interstices. A "refrigeration device" may mean any
appliance that uses heat exchanging for cooling of an interior of
such a device. Examples are cold-wall type freezers, which may for
example be vertical or horizontal freezers.
[0020] Reference is now made to FIGS. 1 and 2. FIG. 1 shows a
perspective view of a horizontal freezer 10 in accordance with an
aspect of the present invention with portions cut away to reveal
interior detail. FIG. 2 shows a perspective partially sectional
view of a cabinet wall 22 of the freezer of FIG. 1.
[0021] FIG. 1 shows the freezer 10 having four cabinet walls 22 and
a base 14. In the example shown, there are four inner walls 12, a
spiral coil of evaporator tubing 16 outwardly from the out sides of
inner walls 12, a heater foil 18 adhered on the evaporator tubing
16 and inner wall 12, a thermal insulation 28 disposed on an outer
side of the heater foil 18, a condenser tubing 30 on an outer side
of the thermal insulation 28, and an outer wall 32 externally of
the condenser tubing 30. The four inner walls 12 may be upstanding
to form a rectangular box, and thereby define an interior 20 of the
freezer 10 and an opening 21 for access to the interior 20. The
inner walls 12 may be formed of any suitable heat conductive
material, for example metallic or plastic material. Accordingly,
the inner walls 12 may be used to conductively exchange heat for
cooling of the interior 20. The opening 21 may be open to the
ambient or a door may be constructed thereon as a lid (60 as shown
on FIGS. 4 to 6) on top of the cabinet walls 22.
[0022] The evaporator tubing 16 is connected to a compressor (96 in
FIG. 3), as is known in the art. The evaporator tubing 16 acts as a
cooling member, so that the interior 20 of the freezer 10 becomes
cooled by heat transfer through the inner walls 12. As will be
apparent to the skilled person, the evaporator tubing 16 may be a
serpentine coil or a spiral coil connected to an exterior of at
least one of the inner walls 12.
[0023] In FIG. 1, for illustrative purposes, heater foil 18 is
shown cutaway so that the evaporator tubing 16 may be seen. A
heating of the heater foil 18 will melt frost accumulation on the
inner walls 12 as will be described in greater detail below.
[0024] Thermal insulation 28 is exterior of the heater foil 18 and
provides insulation between the evaporator tubing 16 and condenser
tubing 30. The thermal insulation 28 may be foam injected between
the inner walls 12 and the outer walls 32. In the example shown,
the condenser tubing 30 is spirally attached to an inside surface
of the outer wall 32. At an end of the condenser tubing 30 is an
expansion valve 97 (FIG. 3), as is known in the art. Four of the
outer walls 32 define an exterior of the freezer 10. The outer
walls 32 may be formed of metal or other conductive material and
may be utilized as a heat transfer surface for the condenser tubing
30. Accordingly, heat from the condenser tubing 30 is released to
an exterior of the freezer via the outer walls 32, as is known in
the art. Alternatively, condenser tubing 30 may be a serpentine
coil rather than a spiral coil for heat exchanging to an exterior
of the freezer 10.
[0025] Reference is now made to FIG. 2, which shows a cabinet wall
22 of the freezer 10. It shows an upper portion 24 and a lower
portion 26 of the cabinet wall 22.
[0026] The components of the heater foil 18 are shown in FIG. 3. In
the example shown, heater foil 18 has two heat conductive sheets
44, 46 having heater wires 33, 34 disposed therebetween. Each
conductive sheet 44, 46 may be formed of conductive, for example
metal, foil and may have a peel off adhesive on one side and a
non-adhesive side. In one embodiment, heater wires 33, 34 are
adhered to the adhesive side of conductive sheet 44. The other
conductive sheet 46 then has its non-adhesive side adhered to the
adhesive side of conductive sheet 44. The adhesive side of
conductive sheet 46 may then be adhered to an exterior of the inner
walls 12, as shown in FIG. 2. Heater wire 33 defines an upper
region in the heater foil 18 corresponding to upper portion 24 of
the cabinet wall 22 as shown in FIG. 2. Similarly, heater wire 34
defines a lower region in the heater foil 18 corresponding to lower
portion 26 of the cabinet wall 22 as shown in FIG. 2. The heater
wires 33, 34 (FIG. 3) are shown in a serpentine configuration for
heating of the upper and/or lower portions of heater foil 18. Lead
wires 36, 38 extend from heater wire 33 and may be connected to a
controller 98. When a current is applied to lead wires 36, 38, heat
is generated in heater wire 33. Accordingly, activation or
energizing of either heating wire 33, 34 will heat a corresponding
region in the conductive sheets 44, 46 by way of heat conduction,
and will thereby heat the upper portion 24 and lower portion 26 of
the cabinet wall 22. Lead wires 40, 42 extend from heater wire 33
and may be connected to the controller 98. Lead wires 40, 42
operate in a similar manner to lead wires 36, 38. The controller 98
may also be used for setting appropriate heating times as will be
described further.
[0027] FIGS. 4 to 6 show the operation of the freezer 10. As shown,
the upper heater wire 33 is located to heat the upper portion 24 of
the cabinet wall 22, and lower heater wire 34 is located to heat
the lower portion 26 of the cabinet wall 22. Frost 50 is shown in
FIG. 4 as formed on the upper portion 24 of the cabinet wall 22.
FIG. 5 shows a first mode of operation, wherein the frost 50 is
melted and reformed as ice 52 on the lower portion 26 of the
cabinet wall 22. FIG. 6 shows a second mode or full defrost mode of
operation, wherein a portion of the ice 52 and any additional frost
is melted for removal by a user. The operation is controlled by the
controller 98 (FIG. 3) for automatically effecting a predetermined
cycle of operation of the compressor 96 and the heater wires 33, 34
at predetermined, preferably regular, intervals.
[0028] The first mode of operation is preferably performed on the
freezer 10 at regular intervals, for example, a 12-hour compressor
96 run time interval. In the first mode of operation, a first step
in the cycle is that the compressor 96 may be temporarily turned
off by the controller 98. The next step is the upper heater wire 33
is then energized by the controller 98 to melt the frost 50, the
melted water being reformed as ice 52 on the lower portion 26 of
the cabinet wall 22. Since the compressor 96 is only recently
turned off, the lower portion 26 remains sufficiently cold for
refreezing of the melted frost. Frost 50 is undesirable as it may
act as an insulator that reduces heat transfer efficiency in the
evaporator tubing 16 through the inner walls 12 of the cabinet and
impedes proper air circulation. On the other hand, ice 52 has a
higher density than frost 50, and is substantially free from gas or
air filled interstices. Accordingly, ice 52 has less insulating
properties than frost 50, and heat transfer between the evaporator
tubing 16 and the interior 20 of the freezer 10 may be improved
when frost 50 is melted into ice 52. The upper heater wire 33 is
thus activated by the controller 98 for a time to melt the frost
50. As can be appreciated, the upper heater wire 33 is preferably
heated for a selected time, dependent on the wattage, sufficient to
melt the frost 50, but not so as to substantially increase the
temperature of the interior 20 of the freezer 10. The last step in
the cycle is that the controller 98 de-energizes the upper heater
wire 33 and turns the compressor 96 back on for normal operation of
the freezer 10. After the next predetermined interval, for example
after 12 hours of compressor 96 run time, the above described cycle
is repeated, by melting the frost 50 and refreezing the melted
water into ice 52. The desired time of operation and the wattage of
the heater wires 33, 34 may vary depending on the freezer 10 and
may be determined by experimentation.
[0029] The following configuration may be used in one preferred
form of the first mode of operation. The upper heater wire 33 and
lower heater wire 34 may for example be rated at 2.5 watts
per-linear foot. This value is in compliance with the Underwriters
Laboratories Inc..TM. Commercial Freezers standard 471, which
requires that resistance-type heater Wires employed to prevent
condensation are considered in compliance if the insulation is
rated 176.degree. F. (80.degree. C.) or higher, the input is less
than 2.5 watts per foot (8.3 W/m), and adjacent heater wires are
maintained not less the 3/4 inch (19.1 mm) apart. Each heater wire
33, 34 will generate approximately 150 watts of heat. It is
suitable for the inner walls 12 to reach a maximum of about
50.degree. F. (10.degree. C.). This configuration has been found to
be suitable for melting of the frost 50, without significantly
increasing the temperature of the interior 20 of the freezer 10.
The thermal mass of the food product may also assist in
compensating against the slight increase in temperature within the
interior 20 of the freezer 10.
[0030] In another embodiment, the ice 52 acts as a "holdover
cooling" feature, as best illustrated in FIG. 5. In the interior 20
of the freezer 10, the ice 52 may be frozen to temperatures of
around -25.degree. F. (-32.degree. C.) and lower. When the
compressor 96 is turned off (either for the first mode of operation
or other reasons, such as blackout or circuit malfunction), the ice
52 assists in maintaining the low temperature of the interior 20 of
the freezer 10.
[0031] The second mode or full defrost mode of operation is
preferably performed on the freezer 10 when necessary, such as once
every few months. A manual or automatic timer may be used to
perform the cycle of operation constituting the second mode. In a
first step of the cycle, the compressor 96 may be temporarily
turned off by the controller 98. As shown in FIG. 6, the lower
heater wire 34 is then energized by the controller 98 to melt a
portion of the ice 52. The ice 52 may then be removed by a user by
gently prying the ice 52 from the inner walls 12 using a plastic
object such as a spatula (not shown). The ice 52 may also fall to
the base 14 of the freezer 10 for removal by a user, as shown in
FIG. 6. The controller 98 then de-energizes the upper heater wire
33 and turns the compressor 96 back on for normal operation of the
freezer 10.
[0032] In another embodiment, as best illustrated in FIG. 6,
instead of solely the bottom heater wire 34 being energized by the
controller 98, both the top heater wire 33 and bottom heater wire
34 are activated to melt a portion of any ice 52 or frost. This
facilitates removal of any ice 52 or frost accumulated anywhere on
the inner walls 12, by gently prying or removing by a user.
[0033] FIG. 7 shows a perspective sectional view of a vertical
cold-wall type freezer 70 in accordance with another embodiment of
the present invention. The freezer 70 has three side cabinet walls
82, an upper cabinet wall 83, and a base 74. The side cabinet walls
82, upper cabinet wall 83, and base 74 form a rectangular box, and
thereby define an interior 84 of the freezer 10 and an opening 81
for access to the interior 84. In the example shown, there are
three inner side walls 72, a serpentine coil of evaporator tubing
76, a heater foil 78 adhered thereon, a thermal insulation 88, a
condenser tubing 80, and an outer wall 92. There is also a shelf 90
for support of products in the freezer 70. The opening 81 usually
has a door (not shown) constructed thereon.
[0034] The inner side walls 72 may be used to conductively exchange
heat for cooling of the interior 84. The evaporator tubing 76
surrounds an exterior of the inner side walls 72 for cooling of the
interior 84 of the freezer 70. The evaporator tubing 76 is
connected to a compressor (e.g., 96 in FIG. 3), as is known in the
art. The evaporator tubing 76 acts as a cooling member, so that the
interior 84 of the freezer 70 becomes cooled by heat transfer
through the inner side walls 72.
[0035] Heater foil 78 is adhered exterior to the three inner side
walls 72 and also covers a region of the inner side walls 72
proximate to the opening 81. For illustrative purposes, heater foil
78 is shown cutaway so that the evaporator tubing 76 may be shown.
A heating of the heater foil 78 will melt frost accumulation on the
inner side walls 72.
[0036] Thermal insulation 88 is exterior of the heater foil 78 and
provides insulation between the evaporator tubing 76 and condenser
tubing 80. In the example shown, the condenser tubing 80 is in a
serpentine configuration and attached to an inside surface of the
outer wall 92. At an end of the condenser tubing 80 is an expansion
valve (e.g. 97 in FIG. 3), as in known in the art. The outer walls
82 may be formed of metal or other conductive material and may be
utilized as a heat transfer surface for the condenser tubing 80.
Accordingly, heat from the condenser tubing 80 is released to an
exterior of the freezer via the outer walls 82, as is known in the
art.
[0037] The heater foil 78 is similar to the heater foil 18 as shown
in FIG. 3, as explained above. Thus, similar to heater foil 18,
there is a heater wire (not shown) defining an upper region and a
heater wire (not shown) defining a lower region.
[0038] The operation of the vertical freezer 70 is similar to the
operation of the horizontal freezer 10, as illustrated in FIGS. 4
to 6, explained above. Thus, the freezer 70 is operable in a first
mode of operation and in a second or full defrost mode of
operation. For illustrative purposes, the heater foil 18 will be
used, as shown in FIG. 3. In the first mode of operation, the first
step is the compressor 96 may be temporarily turned off by the
controller 98. The next step is the upper heater wire 33 is then
energized by the controller 98 to melt the frost 50, the melted
water being reformed as ice 52 on the side cabinet wall 82. The
upper heater wire 33 is thus activated by the controller 98 for a
time to melt the frost 50. The controller 98 then de-energizes the
upper heater wire 33 and turns the compressor 96 back on for normal
operation of the freezer 70.
[0039] In the second mode of operation, the compressor 96 may be
temporarily turned off by the controller 98. As shown in FIG. 6,
the lower heater wire 34 is then energized by the controller 98 to
melt a portion of the ice 52. The ice 52 may then be removed by a
user by gently prying the ice 52 from the inner side walls 72 using
a plastic object such as a spatula (not shown). The ice 52 may also
fall to the base 74 of the freezer 70 for removal by a user. The
controller 98 then de-energizes the upper heater wire 33 and turns
the compressor 96 back on for normal operation of the freezer 70.
In another embodiment, as best illustrated in FIG. 6, instead of
solely the bottom heater wire 34 being energized by the controller
98, both the top heater wire 33 and bottom heater wire 34 are
activated to melt a portion of any ice 52 or frost. This
facilitates removal of any ice 52 or frost accumulated anywhere on
the inner side walls 72, by gently prying or removing by a
user.
[0040] While the invention has been described in detail in the
foregoing specification, it will be understood by those skilled in
the art that variations may be made without departing from the
scope of the invention, being limited only by the appended
claims.
* * * * *