THERMO-ELECTRIC COOLER
One or more piezoelectric devices cool or heat a thermally-conductive basin. The basin is sized, shaped and arranged to receive two or more food serving trays. In a preferred embodiment, the food serving trays are sized, shaped and arranged to provide an air gap between the tray and the thermally-conductive basin so that the tray is cooled by convection and radiation but not conduction.
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A problem with prior art thermoelectric coolers or chillers shown in
While heat conduction can transfer heat between the food storage tray 6 and the thermoelectric device 3, conductive heat transfer tends to result in an uneven heat absorption through-out the basin 11. Portions of the basin 11 nearest the Peltier device 3 tend be very cold whereas portions of the basin away from the Peltier device tend to be relatively warm, especially when the basin 11 is fitted tightly against a food holding tray filled with relatively warm food products. The reliance on only thermal conduction to transfer heat between the food products and the Peltier refrigeration device tends to create significant temperature gradients between the bottom of the tray 5 and the open top 7. A thermoelectric cooler that would accept industry-standard inserts and which would provide a more uniform temperature through-out a food holding tray would be an improvement over the prior art.
The length of the sidewalls 18 determines the location of the bottom of the tray 42 above the bottom of the basin 20. The sidewall length thus effectively determines the space between the basin bottom 20 and the tray bottom 42. The open space between the tray bottom 42 and the basin bottom 20 defines a second, substantially rectangular air gap 46.
The air gap 44 and the air gap 46 allow air currents to exist between the sidewalls and bottom of the food storage try 36 and the side walls and bottom of the basin 14. The air gaps thus allow heat transfer by convection currents.
The air gaps also allow heat to be radiated from warm surfaces to cold surfaces. The air gaps thus allow heat transfer by radiation. Except for very small amounts of heat transfer that can take place between the top edges of the food storage tray 36, which rest on the top surface 21 of the cabinet 12, heat transfer between the food storage tray 36 and the basin 14 is by convection and radiation but not by conduction. Transferring heat by convection and radiation but not conduction is believed to provide a more uniform heat dissipation from the food storage tray 36, which yields a more uniform temperature gradient inside the tray 36.
Refrigerating the basin 14 can be accomplished by having the lower surface 22 of the bottom 20 of the basin 14 thermally connected to a cold side heat sink 26, below which is a solid state heat pump or Peltier device. Peltier devices and their operation are well known to those of ordinary skill in the art. A description of their characteristics and operation is omitted for brevity, they are however considered herein to be solid-state heat pumps.
Air is preferably blown across a finned, hot-side heat sink 28 that dissipates heat from the hot side of a Peltier device. Dissipating heat from the hot side decreases the Peltier device cold side temperature. As the Peltier device cold side gets colder, the temperature of the metal surrounding the cold side of the Peltier device drops, allowing the colder metal to absorb heat.
Temperature sensors 49 are coupled to the lower surface 22 of the basin to provide an electrically measurable representation of the temperature of the basin 14, to a controller or central processing unit 32. The controller or CPU 32 reads the sensors 49 and in response thereto, it modulates the electric power provided to the Peltier device to keep the measured temperature within a preferred operating range.
In one embodiment, the controller/CPU 32 measures a voltage across a temperature-dependent transistor. In another embodiment, the controller/CPU reads the electrical resistance of a thermistor. The temperatures of the sensors 49 thus indicate a temperature of at least the lower surface of the basin 22. By adjusting the power provided to the Peltier device, the temperature inside the basin can be effectively controlled.
In
The second thermoelectric device 24 is provided with its own controller 32A and its own temperature sensors 49. The tandem thermoelectric devices 24 in a single basin 14 enable the temperature-controlled food storage unit 10 to sink more from the right side of the basin 14 than from the left side. Using a second Peltier device also allows more heat to be removed from the basin 14 than would otherwise be possible with a single device.
In a preferred embodiment, the fan speed and/or Peltier device 24 power is modulated by the controller/CPU responsive to the temperature of the thermally conductive basin 14, as measured by one or more of the temperature sensors 49. If the temperature inside the basin 14 falls below a predetermined value, the blower speed is reduced and/or the power to the thermoelectric device 24 is adjusted to keep the temperature of the basin 14 within desired limits.
As stated above, a problem with prior art thermoelectric chillers is their exclusive reliance on conductive heat transfer between a thermoelectric device and a food product to be cooled. In the embodiments shown in
In a preferred embodiment, the conductive basin 14 is sized, shaped and arranged to receive two or more industry-standard food storage containers 36 and to provide the aforementioned one or more air gaps around the exterior of a food storage container 36. The cabinet 12 is preferably provided with separate and independently hinged thermally insulated covers 48 for each basin 36. In another embodiment, the food storage containers 36 in the basin are configured to receive a thermal insert as described in the U.S. patent application Ser. No. 12/329,795, the contents of which are incorporated herein by reference as well as a thermal insert described in U.S. patent application Ser. No. 12/478,439, the contents of which are also incorporated herein by reference.
While the preferred embodiment of the food storage unit 10 is of a cold storage unit, those of ordinary skill in the art will recognize that the food storage unit 10 can also be a hot food storage unit by simply reversing the orientation of the Peltier device. And while the preferred embodiment uses a Peltier device as a refrigeration unit to refrigerate the basin 14, alternate embodiments use ice, cold water, an ice/water slurry and a conventional compressed gas refrigeration units. Alternate embodiments of a hot food storage unit steam, hot water and electrically-resistive heaters thermally coupled to the basin 14.
The foregoing description is for purposes of illustration only. The scope of the invention is defined by the appurtenant claims.
Claims
1. A temperature controlled food storage unit (food storage unit) comprised of:
- a cabinet;
- a thermally conductive basin (basin) within the cabinet, the basin having an open top, four sides and a bottom;
- a refrigeration unit within the cabinet having a first side thermally coupled to the basin and having at least one second side thermally coupled to a heat sink, the basin being configured to receive a thermally conductive food storage container (container) comprised of an open top, at least first and second sides and a bottom, the container being sized, shaped and arranged to be suspended in the basin from at least one of the cabinet and the basin, and being sized, shaped and arranged to provide an air gap between a side of the container and a side of the basin.
2. The food storage unit of claim 1, wherein the refrigeration unit is a Peltier device.
3. The food storage unit of claim 2, further including an air gap between the bottom of the basin and the bottom of the container.
4. The food storage unit of claim 1, wherein the air gap between sides of the container and sides of the basin, is configured to transfer heat convectively between the basin and the container through air in the air gap.
5. The food storage unit of claim 2, wherein the air gap between sides of the container and sides of the basin, is configured to transfer heat convectively between the basin and the container through air in the air gap.
6. The food storage unit of claim 1, wherein air gaps between the basin and container are configured to allow heat transfer between the basin and container via air convection currents and infrared radiation but not via conduction.
7. The food storage unit of claim 5, wherein the air gaps between basin and container are configured to allow heat transfer between the basin and container via air convection currents and infrared radiation but not via conduction.
8. The food storage unit of claim 1, wherein the container sides are tapered inwardly from the open top of the container to the bottom of the container.
9. The food storage unit of claim 1, 6, 7 or 8, further comprised of a thermally-insulated cover for the container, the thermally-insulated cover being hingedly attached to at least of the cabinet and the basin to rotate around a hinge between open and closed positions.
10. The food storage unit of claim 1 or 2, further comprised of a plurality of containers in said basin and a corresponding number of thermally-insulated covers, each thermally-insulated cover being hingedly attached to at least of the cabinet and the basin to rotate around a hinge between open and closed positions for each container.
11. The food storage unit of claim 1 or 2, further comprised of temperature sensor, thermally coupled to the basin, the temperature sensor effectuating temperature control of the basin.
12. The food storage unit of claim 11, wherein the temperature sensor is a thermistor.
13. The food storage unit of claim 11, wherein the temperature sensor is a transistor.
14. The food storage unit of claim 11, wherein the temperature sensor acts to control the electric power applied to the refrigeration unit.
15. The food storage unit of claim 11 wherein the temperature sensor acts to control air flow across the heat sink.
Type: Application
Filed: Jun 4, 2009
Publication Date: Dec 9, 2010
Applicant: PRINCE CASTLE, INC. (CAROL STREAM, IL)
Inventors: KOREY V. KOHL (ROGERS, MN), ROBERT A. IVERSON (MOUND, MN), LOREN VELTROP (CHICAGO, IL), CHRISTOPHER B. LYONS, JR. (LAGRANGE PARK, IL), DONALD VAN ERDEN (WILDWOOD, IL)
Application Number: 12/478,480
International Classification: F25B 21/02 (20060101);