HOT OR COLD FOOD RECEPTACLE UTILIZING A PELTIER DEVICE WITH AIR FLOW TEMPERATURE CONTROL

Abstract

A temperature controlled food storage unit is provided with a Peltier device (18) to effectuate the temperature of food place in a thermally conductive container or basin (24). Air from a fan (52) is passed through an air duct (50) and over a heat sink (22), which is thermally coupled to one side of the Peltier device (18). A hand-operated damper (54, 64) is used to control the air flow through the air duct (50) and over the heat sink (22) thereby controlling heat exchange between the Peltier device (18) and ambient air.

Description

FIELD OF THE INVENTION

This invention relates to a temperature controlled food storage unit that uses a solid-state, thermoelectric heat pump device commonly known as a Peltier device.

BACKGROUND OF THE INVENTION

FIG. 1 is a perspective view of a prior art food storage container 10 that provides a cold storage using a solid-state, thermoelectric heat pump device. The types of foods kept in container 10 often include items such as meats, soups, cheeses, vegetables, and condiments, including condiment dispensers. Multiple food storage containers 10 of similar or varying sizes can be used simultaneously in food service preparation counters or carts, such as used in the assembly of sandwiches and pizzas, and also commonly used in soup and salad buffets.

FIG. 2 is a cross section of the storage container 10 taken along line 2-2 of FIG. 1. FIG. 2 depicts the interior walls 14, which are usually made from a thermally conductive material such as aluminum or stainless steel, and a bottom or base 16, which is also thermally conductive.

A thermoelectric assembly 17 is thermally coupled to the bottom 16 of the food container 10. The thermoelectric assembly 17 includes a solid-state, thermoelectric device 18, which is sandwiched between a thermal transfer plate 20 and a heat sink 22.

The thermoelectric device 17 is embodied as a Peltier device works according to the Peltier effect. One side of the device will be cool or cold while the opposite side is warm or hot, depending on the direction of current flow through the Peltier device. The Peltier device 18 acts as a heat pump in that heat is absorbed on the cold side and transferred to the hot side where it is dissipated.

In FIG. 2 the Peltier device is configured to have its cool or cold side facing the base 16 of the container 10 in order to cool the container. A thermal transfer plate 20, embodied as a block of thermally conductive material such as copper or aluminum, is located between and thermally coupled to both the cold side of the Peltier device 18 and the base 16 of container 10.

The Peltier device 18, the cold side of which is against the thermal transfer plate 20, will absorb heat from the plate 20, causing its temperature to drop. The heat transfer plate 20 will thereafter absorb heat from the base 16 of the container 10.

A heat transfer medium, such as a silicone thermal transfer grease or tape, is often paced between the Peltier device 18 and the thermal transfer plate 20 to improve conductive heat transfer between the two bodies. The heat sink grease or tape can also be placed between the thermal transfer plate 20 and the base 16 of the container 10.

In addition to the thermal transfer plate 20, a heat-dissipating sink 22 is located below the Peltier device 18 and thermally coupled to the hot side of the Peltier device 18. The heat sink 22 is also comprised of materials having a relatively high thermal conductivity coefficient, such as copper and aluminum. As with the cold side and the thermal transfer plate 20, thermal transfer grease or tape, can be used between the Peltier device 18 and heat sink 22 to improve heat transfer there between.

The structure depicted in FIG. 2 is known prior art, however, a drawback of prior art food storage devices that use Peltier devices is that the temperature inside the container is effectuated by controlling the Peltier device electrically. Prior art refrigerators that use Peltier devices effectuate temperature control by measuring temperatures and shutting off or adjusting current to the Peltier device. Sensing temperature and controlling electric power requires electronic devices that add manufacturing cost and which are themselves subject to failure. A food storage device that uses a solid state Peltier device and which can effectuate temperature control without having to rely on sensors and electronic or electrical control devices would be an improvement over the prior art.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a prior art food storage container;

FIG. 2 is a cross-section taken along line 2-2 of FIG. 1 of a prior art food storage container showing the connection of a Peltier device;

FIG. 3 is a perspective view of a food receptacle that can be kept hot or cold by a Peltier device, with the inside temperature of the receptacle being controlled by air flow over;

FIG. 4 is a cross-sectional view of the device shown in FIG. 3

FIG. 5 is an alternative embodiment of a manually controlled damper for manually controlling air flow over a heat sink of a Peltier device connected to a food storage device;

FIGS. 6A, 6B and 6C is another alternative embodiment of a manually controlled damper for manually control air flow over a heat sink of a Peltier device connected to a food storage device; and

FIGS. 7A, 7B and 7C bottom view showing the use of manually rotatable heat-sink fins for manually controlling air flow over the heat sink of a Peltier device connected to a food storage device.

FIG. 8 shows the use of multiple Peltier devices, thermally coupled in parallel to a food storage container;

FIG. 9 shows the use of stacked Peltier devices connected to a food storage device;

DETAILED DESCRIPTION

A known characteristic of Peltier devices is that the heat dissipation/absorption of one side is proportional to the heat absorption/dissipation from the other side. Stated another way, the temperature of the cold side is proportional to the heat dissipated from the hot side. The hot side temperature is proportional to heat absorbed by the cold side. Depending on which side is thermally coupled to a food storage container, a Peltier device can thus be used to either sink heat from food receptacles that need to be kept cold or provide heat to receptacles that need to be kept hot.

Temperature control of Peltier device-cooled food receptacles disclosed herein is effectuated by controlling heat dissipated from the Peltier device hot side. Temperature control of Peltier device-heated food receptacles disclosed herein is effectuated by controlling the heat absorbed by the Peltier device cold side.

Heat dissipation from the hot side and heat absorption by the cold side is controlled by controlling air flow. In one embodiment, air flow control is accomplished by a movable damper located either up stream or downstream of a fan that moves air across a heat transfer body. In another embodiment, air flow control is accomplished by an air flow diverter that routes air through or around a heat transfer body. In another embodiment, air flow control is accomplished by controlling the speed of a fan that moves air across a heat transfer body. In yet another embodiment, heat transfer from or heat transfer into a Peltier device is accomplished by a finned heat transfer body, the fin structure of which is rotatable relative to the air flow direction such that rotating the heat sink fin structure parallel to an air current direction, increases heat transfer while rotating the heat sink fin structure orthogonal to an air current reduces heat transfer.

FIG. 3 shows a perspective view of a first embodiment of a food receptacle 24 (also considered herein to be a container and a basin) the temperature of which is effectuated by heat transferred through a Peltier device 18. FIG. 4 is a cross-sectional view.

As shown in the figures, the opposing, heat-transferring sides of the Peltier device are thermally coupled to a thermal transfer plate 20 and a heat sink 22, which are spatially and thermally separated from each other. One side of the thermal transfer plate 20 is thermally coupled to the bottom 23 of the basin or food storage container 24, which itself is preferably made from a thermally conductive material suitable for use in a restaurant, food service or kitchen, examples of which include stainless steel or aluminum. The opposite side of the thermal transfer plate 20 is thermally coupled to one side of the Peltier device 18. As described above, the thermal transfer plate 20 effectuates heat transfer between the Peltier device 18 and the food storage container 24.

An air duct 50 directs air from a fan 52 over the heat sink 22. The orientation and placement of the fan is a design choice but the fan 52 is preferably attached to a side wall of a cabinet, similar to the one shown in FIG. 1 that supports the food storage container 24. In one embodiment, the fan 52 is behind a safety grill and can be operated with or without an air filter. The orientation of the fan 52 can be changed so that the fan 52 can be mounted inside the cabinet and draw air from an air space between the bottom of the cabinet and a countertop or floor on which the food storage device is operated.

As explained more fully below, the temperature inside the food storage container is controlled by controlling air flow over the side of the Peltier device that is opposite the food storage container and not by sensing temperature inside the container 24 and/or controlling electric power to the Peltier device 18. In an alternate embodiment, however, a temperature sensing device can be used to provide for temperature warnings or alarms or other operating conditions, such as a thermal runaway of the Peltier device.

In the embodiment shown in FIG. 3 and FIG. 4, the volumetric flow of the air from the fan 52 across the heat sink 22 is controlled by a manually-operated, i.e., hand-controlled, adjustable damper 54. The damper 54 is shown in FIG. 3 as being located away from the fan, i.e., at the distal or far end 57 of the air duct 50, however, in an alternate embodiment, the damper 54 is located between the heat sink 22 and the fan 52.

The damper in one embodiment is hingedly attached to the duct 50 at the top 58 of the duct 50. Rotating the damper 54 counterclockwise around the hinge 55, which connects the damper 54 to the duct 50, allows increased air flow through the duct 50.

An alternate and equivalent embodiment of the configuration shown in FIG. 3 and 4, but which is not shown uses a damper configured to open when it is rotated clockwise. Another embodiment uses a damper 54 hingedly attached to the bottom 59 of the duct. One such alternate embodiment uses a damper 54 that opens to allow air through the duct 50 when rotated clockwise while another embodiment uses a damper 54 that opens to allow air through the duct when it is rotated counterclockwise. In yet another embodiment not shown, the duct 54 is embodied as a sliding door able to move across the duct in directions that are into and out of the plane of the paper on which the figure is drawn or, up and down.

Different damper 54 positions between fully open and fully closed will allow correspondingly more or less air from the fan 52 to pass through the duct 50 and over the heat sink 22. Heat transfer between the ambient air driven through the duct 50 by the fan 52 will increase when the damper is “open” and decrease as the damper 54 closes. Changing or adjusting the position of the damper 54 between fully open and fully close thus effectively provides heat transfer control of the Peltier device, which in turn provides control over the temperature of the opposite side of the Peltier device, i.e., the side of the Peltier device 18 facing the food storage receptacle 24 and as a result, the temperature inside the food storage container 24. Temperature control of the receptacle 24 is thus effectuated simply, reliably and mechanically, i.e., by controlling air flow over a heat sink coupled to the Peltier device.

FIG. 5. shows an alternate and equivalent embodiment of a duct/fan/damper configuration that can be used to control the temperature of a food receptacle by controlling air flow. In FIG. 5, the fan 52 is configured to pull or draw air across the heat sink 22 from air duct 50 whereas in the embodiment shown in FIG. 3 and FIG. 4 the fan 52 pushes air through the duct and over the heat sink.

Unlike the embodiment shown in FIGS. 3 and 4, the embodiment of FIG. 5 provides maximum air flow across the heat sink 22 when the manually controlled damper 54 is fully “closed,” which is when the damper 54 is rotated in the counterclockwise direction. When the damper 54 is closed, all of the air drawn by the fan 52 is pulled down the duct 50 and across the heat sink 22. As the damper 54 rotates clockwise, it “opens” and allows ambient, room air to flow around or by-pass the heat sink 22. As the duct is rotated to is full open position, almost no air is drawn over the heat sink 22.

The embodiment of FIGS. 3 and 4 controls air flow across the heat sink 22 by restricting air flow through the duct 50. The embodiment of FIG. 5 controls air flow across the heat sink by routing air flow across the heat sink or around the heat sink. Unlike the embodiment of FIGS. 3 and 4, the embodiment of FIG. 4 moves substantially the same volume of air through the fan 22 at all times. Air flow noise in the embodiment shown in FIG. 5 can therefore be maintained at a more-constant level

FIGS. 6A, 6B and 6C show yet another duct/fan/damper configuration by which the temperature of a food storage receptacle 24 using a Peltier device 18 can be simply and effectively controlled by controlling air flow. The embodiment shown in FIGS. 6A, 6B and 6C uses a sliding damper 64, which in FIGS. 6A, 6B and 6C, is downstream from a fan 52. In another embodiment, the sliding damper 64 is at the distal end 57 of the duct, i.e., downstream from the Peltier device 18.

When the damper 64 in FIG. 6C is manually positioned to close off opening 66, the fan 52 will move air through only the opening 62 into the room, which will prevent air from moving through the duct 50 and over the heat sink 22. When the damper 64 is manually positioned to close off opening 62 to the room, as shown in FIG. 6A, the fan 52 will move air through only the air duct 50, which then forces fan air over the heat sink 22. When the damper 64 is positioned at some intermediate opening position as shown in FIG. 6B, some air will flow through both the opening 62 to the room and through the opening 64 into the duct 50. Changing the position of the damper 64 will therefore change the amount of air flowing over the heat sink 22. Changing the position of the damper 64 will thus change the temperature of the side of the Peltier device that is thermally coupled to the food storage container 24 through the thermal transfer plate 20.

FIGS. 7A, 7B and 7C depict a bottom view of a rotatable heat sink 70, looking upwardly toward the bottom of the food storage container. In FIGS. 7A, 7B and 7C, the orientation of the heat sink relative to the air flow direction controls heat transfer into or out of one side of a Peltier device 18. The temperature inside the food storage container 24 is thus controlled by the heat sink 70 orientation. As with the embodiments described above, in FIGS. 7A, 7B and 7C, one side of the Peltier device 18 is thermally coupled a heat transfer plate while the other side is thermally coupled to the finned heat sink 70, which is made up of multiple generally planar fins 72.

In FIG. 7A, the heat sink 70 fins 72 are substantially parallel to the direction of the air flow from the fan 52. Air from the fan will tend to travel freely between the fins 72. As the heat sink 70 is rotated as shown in FIG. 7B, the angle between the heat sink fins 72 and the air flow direction will tend to reduce the amount of air flowing through the fins 72, reducing the heat transfer between the air and the heat sink 70. As the angle between the fins 72 and the air flow direction approaches ninety degrees or perpendicular, as shown in FIG. 7C, heat transfer between the heat sink 70 and the air from the fan will be minimized.

Another embodiment of the invention controls air flow over a heat sink by a variable speed fan and without using any sort of damper or flow control. As used herein, variable speed includes fans using motors having speeds that are continuously variable as well as fans using motors that operate at two or more different speeds.

Finally, another embodiment controls air flow over a heat sink and as a result, the temperature inside a food storage container by using fixed-speed fan motors but using differently-pitched or variably pitched fan blades.

It is important to note that for all of the embodiments depicted in the figures and described above, heat transfer direction can be either into or out of the air stream. The food storage container can thus be either hot or cold, depending upon the orientation of the Peltier device vis-à-vis the food storage container.

When the Peltier device is used to cool the food storage container, the cold side of the Peltier device(s) will face the food storage container. Heat from the food storage container will flow into the Peltier device cold side and be transferred by the device to its hot side, causing the temperature of the heat sink 22 to rise. Heat transfer will therefore be out of the heat sink 22 and into the air stream provided by the fan.

When the Peltier device is used to heat the food storage container, heat transfer is reversed in that heat will be absorbed by the cold side of the Peltier device from the heat sink 22, conducted through the Peltier device and conducted into the food storage container. When the Peltier device is used to heat foods, heat is conducted into the heat sink 22 and into the Peltier device. The claims should therefore be construed to read on both hot and cold food storage devices, the temperature of which is effected by one or more Peltier devices.

For purposes of claim construction, the fans, ducts, dampers, fan blades and movable and adjustable heat sink fins should all be considered air flow control mechanisms because each them is able to control the amount or volume of air flowing over a heat sink that transfers heat from or into a Peltier device. Since each of them can effectuate or determine air flow and as a result, hence heat transfer between ambient air and the heat sink coupled to the one or more Peltier devices, each of them can determine the temperature inside a food storage container. Stated another way, the temperature control of the food storage container disclosed herein is provided essentially by the devices that move and/or control the movement of air over the heat sink. The aforementioned air flow control mechanisms can therefore be also be considered to be temperature control mechanisms as well.

As used herein, the term “heat sink” should not be construed to be limited to a device that absorbs heat from a hot body and which dissipates heat to the environment. As used herein, “heat sink” should be construed to include a heat transfer body that can either transfer heat from a Peltier device, as happens when a Peltier device is cooling a food storage container, and which can transfer heat into a Peltier device, as happens when a Peltier device is heating a food storage container. As used herein, a heat sink is therefore thermally bi-directional.

As used herein, the term “duct” should be broadly construed to include pipes, tubes and channels as well as any component or structural element of a food storage device or cabinet, which routes or directs air from the fan 22 over a heat sink. A duct can therefore also include one or more walls of a multi-wall cabinet, such as a cabinet depicted in FIGS. 1 and 2, which supports a thermally conductive basin for storing or holding hot or cold food.

It is also important to note that the temperature control methodology and structures disclosed herein require adjustment of the various air flow control devices. Stated another way, the damper settings can require some experimentation in order to determine a damper setting whereat a desired temperature is achieved. It is important to also note that the thermal efficiency of the Peltier device will depend on the ambient temperature. Damper settings can require adjustment as room temperatures vary.

Those of ordinary skill in the art will also appreciate that the cooling and heating capacity of a Peltier device is limited. Additional heating and cooling capacity is achieved by operating multiple Peltier devices 18, 28 and 38 thermally in parallel with each other as shown in FIG. 8. Each of the devices 18, 28 and 38 has its cold side (or hot side) coupled to the food storage container 24 with its hot side (or cold side) in the controlled air stream provided by the structures described above.

Those of ordinary skill in the art will also appreciate that the temperature differential between the hot side and the cold side of a Peltier device 18 is somewhat limited. Greater temperature differentials, hotter and colder temperatures, can be achieved by stacking two or more Peltier devices 18, 28 and 38 thermally (not electrically) in series with each other such that the cold side of a first device is coupled to the hot side of second device. In FIG. 9, three Peltier devices 18, 28 and 38 are stacked in series. The cold side of a first device 18 is coupled to the hot side of a second device 28. The cold side of the second device 28 is coupled to the hot side of a third device 38. The cold side of the third device 38 is thermally coupled to a heat transfer plate 20.

In view of the foregoing, the terms Peltier device and solid state heat pump should be construed to include one Peltier device but to also include multiple devices, whether they are thermally in series with each other or thermally in parallel with each other.

The foregoing description and various embodiments are to be considered in all respects as illustrative and not restrictive. The scope of the invention is determined by the appended claims rather than by the foregoing description.

Claims

1. A temperature controlled food storage unit comprised of:

a thermally conductive food storage container (container) for storing food;

a solid state heat pump having a first side thermally coupled to the food storage container and a second side coupled to a heat sink; and

an air flow control mechanism, directing air over the heat sink;

whereby temperature of the container is determined by the air flow control mechanism.

2. The temperature controlled food storage unit of claim 1, wherein the solid state heat pump is a Peltier device.

3. The temperature controlled food storage unit of claim 1, wherein the air flow control mechanism is comprised of an air duct and an adjustable damper for the duct.

4. The temperature controlled food storage unit of claim 3, wherein the adjustable damper is hand-operated.

5. The temperature controlled food storage unit of claim 1, wherein the air flow control mechanism is comprised of a fan.

6. The temperature controlled food storage unit of claim 5, wherein the fan is a variable speed fan.

7. The temperature controlled food storage unit of claim 1, wherein the solid state heat pump is comprised of a Peltier device having a cold side thermally coupled to the food storage container.

8. The temperature controlled food storage unit of claim 1, wherein the solid state heat pump is comprised of a Peltier device having a hot side thermally coupled to the food storage container.

9. The temperature controlled food storage unit of claim of claim 2, wherein the solid state heat pump is comprised of a plurality of Peltier devices, the cold sides of which are coupled to the food storage container in parallel, the hot sides of which are thermally coupled to said air flow control mechanism.

10. The temperature controlled food storage unit of claim of claim 2, wherein the solid state heat pump is comprised of a plurality of Peltier devices, the hot sides of which are thermally coupled to said food storage container in parallel, the cold sides of which are thermally coupled to said air flow control mechanism.

12. The temperature controlled food storage unit of claim of claim 2, wherein the solid state heat pump is comprised of a plurality of Peltier devices, thermally coupled to each other in series.

13. The temperature controlled food storage unit of claim 1 wherein the air flow control mechanism includes a fan directing air toward said heat sink, and wherein the heat sink is comprised of rotatable fins, the orientation of which is adjustable relative to the direction of air flow from said fan.

14. A food storage unit comprised of:

a cabinet;

a thermally conductive food storage basin (basin) in said cabinet;

a Peltier device having a cold side thermally coupled to the basin and a hot side thermally coupled to a heat sink;

a fan; and

an air flow control mechanism;

whereby basin temperature is determined by said air flow control mechanism.

15. The food heating unit of claim 14, wherein the cabinet has at least one side wall and wherein said air flow control mechanism is a damper mounted to said at least one side wall.

16. The food heating unit of claim 14, wherein said cabinet is configured to direct air from said fan over said heat sink.

17. The food heating unit of claim 14, wherein said fan is comprised of a variable speed motor.

18. The food heating unit of claim 15, wherein the damper is hand-operated.

19. The food heating unit of claim 12, wherein the air flow control mechanism includes a heat sink comprised of fins, the orientation of which is adjustable relative to the direction of air flow from said fan.

20. A temperature controlled food storage device, comprising:

a thermally conductive receptacle (receptacle) configured to receive a food item therein;

a thermoelectric device having first and second portion, the first portion thermally coupled to and transferring heat energy between the receptacle and the thermoelectric device, effectuating the temperature of at least a portion of the receptacle;

a heat sink thermally coupled to the second portion of the thermoelectric device, the heat sink configured to transfer heat energy between the thermoelectric device and ambient air driven over surfaces of the heat sink by a fan; and

a manually operated air flow control mechanism controlling the amount of air conveyed over the heat energy transfer device by said fan;

whereby the temperature inside the receptacle is determined by said manually operated flow control mechanism.

21. The temperature controlled device as recited in claim 20, wherein the manually operated air flow control mechanism includes at least one of:

a damper manually positionable to inhibit the conveyance of air over the heat energy transfer device;

a diverter diverting air flow around the heat energy transfer device;

a variable speed fan; and

a manually adjusted heat sink fin, adjustable between a first and a second position, such that when in the first position the fin permits the conveyance of air over the heat sink and when in the second position inhibits the conveyance of air over the heat sink.

22. The temperature controlled food storage device as recited in claim 1, further including a plurality of thermoelectric devices thermally coupled to said food storage container.

23. The temperature controlled food storage device as recited in claim 12, further including a plurality of thermoelectric devices thermally coupled to said food storage basin.

24. The temperature controlled food storage device as recited in claim 18, further including a plurality of thermoelectric devices coupled to said receptacle.

25. A temperature controlled food storage unit comprised of:

a thermally conductive food storage container for storing food;

a solid state heat pump having a first side thermally coupled to the food storage container and a second side coupled to a heat sink; and

a food storage container temperature control mechanism, the temperature control mechanism consisting essentially of: an air flow control mechanism, directing air over the heat sink.

26. The temperature controlled food storage unit of claim 25, wherein the air flow control mechanism is comprised of an adjustable damper for a duct.

27. The temperature controlled food storage unit of claim 25, wherein the air flow control mechanism is comprised of is comprised of a variable speed fan.

28. The temperature controlled food storage unit of claim of claim 25, wherein the solid state heat pump is comprised of a plurality of Peltier devices, the cold sides of which are thermally coupled to said food storage container in parallel, the hot sides of which are thermally coupled to said air flow control mechanism.

29. The temperature controlled food storage unit of claim 25 wherein the air flow control mechanism includes a fan directing air toward said heat sink, and wherein the heat sink is comprised of fins, the orientation of which is adjustable relative to the direction of air flow from said fan.