Abstract:
A refrigeration apparatus for cooling containers and food in the microgravity conditions of outer space comprising a cooler container compartment having a container cold plate therein which is contoured to the shape of sidewall portions of the cans to be cooled. The container cold plate is coated with a complient heat transfer medium such as metal-filled silicone rubber. When the lid of the cooler is closed, the containers are firmly engaged by the complient material, forming a good conductive heat transfer relationship. Extending from the container cold plate is a refrigerated food cold plate. A thermoelectric generator is disposed in a separate cabinet connected to one end of the cooler and includes thermoelectric elements and a heat sink operatively associated with both cold plates within the cooler. A freezer compartment is provided adjacent the container and food cooler compartment. A freezer cold plate thereon is connected to an additional thermoelectric generator.

Description:
BACKGROUND OF THE INVENTION 
     This application is a continuation-in-part of prior application Ser. No. 788,879, filed Oct. 18, 1985 by Arthur G. Rudick, assigned to the same assignee as the present invention. 
    
    
     The present invention relates to a compact refrigeration device suitable for cooling beverage containters or food in the microgravity conditions existing in outer space. More specifically, the present invention relates to a thermoelectric refrigerating unit and an associated cooler housing structure suitable for use upon a space ship for cooling beverage containers or food; and maintaining some food in a frozen condition in a freezer compartment. 
     A premix, carbonated beverage can for use in outer space was recently developed by the assignee of the present invention. This can works extremely well for serving a high-quality beverage under the microgravity conditions of outer space; but a suitable refrigeration device is needed for cooling one or more of these cans in the storage locker onboard a space shuttle. 
     In the conditions that exist in space shuttles or ships, there are space and power limitations with respect to any refrigeration devices which may be used. Therefore, any such refrigeration device must be compact and have low power requirements. Furthermore, since there is no convection in outer space, heat must be removed from the containers to be cooled by conductive heat transfer. Accordingly, a need in the art exists for a compact, low-power refrigeration device which can cool one or more beverage cans in the microgravity conditions of outer space primarily by means of conductive heat transfer. 
     A need in the art also exists for such a refrigeration device which can also cool food and/or maintain selected quantities of food in a frozen condition. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is a primary object of the present invention to provide a refrigeration device for use in outer space which can efficiently cool one or more beverage containers primarily by means of conductive heat transfer. 
     It is another object of the present invention to provide such a refrigeration device including an adjacent refrigerated food storage area and a food freezer compartment integrated with a can cooler section into a single compact unit made to the same dimensions as the inside of a tray designed to fit into a space shuttle storage locker. 
     It is another object of the present invention to provide a refrigeration generator for the refrigeration device which is very compact and which has low power requirements. 
     The objects of the present invention are fulfilled by providing a refrigeration apparatus for cooling containers and food in the microgravity conditions of outer space, comprising; a housing defining a container compartment for supporting said containers, a refrigerated food storage area, and a freezer compartment, said housing having an access opening therein for introducing and removing containers and food from the compartments and storage area, and a removable lid for opening and closing the access opening; a container cold plate within the container compartment for cooling the containers by conductive heat transfer, the cold container plate including a metal plate conformally shaped to the exterior sidewall portions of the containers, the metal plate having a layer of complient heat transfer material thereon for firmly engaging the sidewall portions; a food cold plate extending from said container cold plate into said refrigerated food storage area; a freezer cold plate in said freezer compartment; and thermoelectric refrigeration means for maintaining the respective cold plates at a temperature which cools the containers and food to a desired temperature. 
     The thermoelectric refrigeration means includes a separate enclosure mounted to the end of the container compartment housing, a heat sink disposed within the enclosure, at least one thermoelectric element coupled to the heat sink within the enclosure, and a heat transfer coupling between the thermoelectric elements within the enclosure and the cold plate within the refrigeration compartment housing. The enclosure further includes a gas intake opening aligned with the heat sink and a fan for drawing gas through the intake across the heat sink and out of the enclosure to dissipate heat accumulated in the heat sink. An additional enclosure is mounted on the end of the freezer compartment with associated thermoelectric elements, fans and heat sinks. 
     In a first embodiment, the housing defining the refrigeration compartments is fabricated from foam insulating material. In a second embodiment, the housing defining the refrigeration compartment is fabricated from thin metal such as aluminum, and the cans and food to be cooled and cold plate within the housing are spaced from the sidewalls of the housing to form an envelope of air completely surrounding the cans. Under the conditions which exist in outer space, air acts as a very good insulator in the absence of convective heat transfer. 
     The present invention also includes a temperature control means for energizing and deenergizing the thermoelectric elements and fan at appropriate temperature levels and a safety circuit precluding damage to the refrigeration device from current faults or excessive temperatures which may develop in the heat sinks. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The objects of the present invention and the attendant advantages thereof will become more readily apparent by reference to the drawings wherein: 
     FIG. 1 is an exploded view in perspective showing the refrigeration device of the present invention with a plurality of beverage cans therein; 
     FIG. 2 is a top plan view of the refrigeration device of FIG. 1 partially in section; 
     FIG. 3 is a sectional view taken longitudinally of FIG. 2; 
     FIG. 4 is a side elevational view in section of a second embodiment of a refrigeration compartment of the present invention which is an alternative embodiment to the structure illustrated in FIG. 3; 
     FIG. 5 is a schematic diagram of a temperature control circuit for the refrigeration device of the present invention; 
     FIG. 6 is a top plan view of a combination refrigerator and freezer according to the present invention with the lid removed to illustrate the relative locations of the container compartment, food storage area and freezer compartment; 
     FIG. 7 is a section taken along line 7--7 of FIG. 6 showing one possible construction of the freezer compartment and the thermoelectric cooling device therefor; 
     FIG. 8 is a perspective view of the thermoelectric cooling device for the freezer illustrating the positions of the thermoelectric elements on an interstage plate which couples the freezer heat sink to the freezer cold plate; and 
     FIG. 9 is an enlarged perspective view of a portion of the container cold plate of the refrigerator/freezer of FIG. 6, and the food cold plate which extends into the food storage compartment. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring to FIG. 1, there is illustrated a refrigeration device 10, including a cooler housing 12 with sidewalls 12S, a bottom wall 12B and an access opening 16. Disposed within cooler housing 12 in a refrigeration compartment defined thereby are a plurality of space cans SC of the type disclosed in the aforementioned U.S. patent application Ser. No. 724,155, filed Apr. 17, 1985 and assigned to the same assignee as the present invention. A removable lid 14 is provided which may be secured to the upper edges of sidewalls 12S by any suitable means such as latches, hinges, screws and so forth (not shown). Mounted at one end of the cooler housing 12 is a thermoelectric generator generally indicated 20, including an enclosure 22. Power is provided to the thermoelectric generator 20 through a power cord PC. As illustrated in FIG. 1, a fan F is mounted in an end wall of the enclosure 22 and is operatively associated with an air intake opening AI, and the cooling fins 26F of a heat sink, in a manner to be more fully described hereinafter with reference to FIGS. 2 and 3. Also illustrated in phantom in FIG. 1 is the location of a temperature switch device TS which is the main control device of the temperture control circuit of FIG. 5, to be described hereinafter. 
     Referring to the top plan view in FIG. 2 of the refrigeration device of FIG. 1, the details of the thermoelectric generator 20 are illustrated. Thermoelectric generator 20 includes a heat sink 26, with cooling fins 26F, a thermoelectric element or elements 28, a heat transfer block 30 and a cold plate 32. The heat sink 26 is mounted within enclosure 22 in close proximity to a protective plate 24 by means of bolts 21 extending through one sidewall 12S of housing 12. A fan mounting plate 23 has a rim that fits over the sidewalls of the protective plate 24 and includes a fan F mounted therein with the suction side of the fan facing a plenum chamber 18 within the enclosure 22. Also provided within the fan mounting plate 23 is an air intake opening AI (FIG. 1) which permits air to be drawn therethrough by the fan F over cooling the 26F through the plenum 18 and out the fan F. The fan F is mounted to plate 23 by bolts 19 and the heat sink protective plate 24 is bolted to a sidewall 12S of housing 12 by bolts 17. 
     Thermoelectric elements 28 may be of any commercially available type and are provided on the rear side of heat sink 26, and a front face of a heat transfer block 30. Heat transfer block 30 is, in turn, coupled to cold plate 32. 
     Since there is no convective heat transfer in outer space, the cold plate 32 of the present invention is designed to provide very efficient conductive heat transfer with sidewall portions of the cans SC. In order to achieve this highly efficient conductive heat transfer, cold plate 32 includes a metal layer 32A conformally shaped to sidewall portions of the cans SC, as best illustrated in FIG. 3, and a thin layer 32B of complient heat transfer material, such as a metal filled silicone rubber, on the metal layer 32A adjacent to the sidewall portions of the associated cans SC. Cold plate 32 rests upon a bottom wall 12B of housing 12, and the inner surface of removable lid 14 is provided with a foam pad opposite each can SC to firmly bias the cans SC against complient material 32B when lid 14 is fully closed. That is, the cans SC are tightly squeezed between the foam pads 34 and complient material 32B when lid 14 is fully closed, and the refrigeration compartment within housing 12 is sealed. 
     In the embodiment illustrated in FIG. 3, the walls of the housing 12 are fabricated from foam insulating material. However, in an alternative embodiment illustrated in FIG. 4, the walls of housing 12 may be thin metal such as aluminum. 
     Referring to FIG. 4 wherein the walls of housing 12 are thin aluminum, adequate insulation is provided by spacing the cold plate 32 from the sidewalls of housing 12 by rubber mounts 36. As illustrated, the cans SC are almost completely surrounded by an air space which, in the absence of convection, makes an excellent insulator. Accordingly, in the conditions that exist in a space shuttle, the housing structure embodiment of FIG. 4 provides efficient cooling of the cans SC. All other parts in FIG. 4 are similar to those in FIG. 3 with the exception of the additional foam gasket between the upper edges of the sidewalls of the housing 12 and the bottom peripheral edge of the lid 14. This gasket would be desirable in this embodiment to maintain a sealed air space. 
     Referring to FIG. 5, there is illustrated a circuit schematic of the temperature control and power supply system for the refrigeration device of the present invention. The heat of this system is a temperature switch or controller TS which is coupled through load lines L1, L2 to a fan F and the thermoelectric elements 28. As illustrated, the fan F and thermoelelectric elements 28 are connected in parallel so that they are turned on and off together. The temperature switch TS also is connected through a pair of temperature sensor lines S1 and S2 to a first temperature sensor TSN1 in heat sink 26, and a second temperature sensor TSN2 in cold plate 32, respectively. Power is supplied to the system through a power cord PC and the temperature switch TS. In the preferred embodiment, the power supplied is 28 volts DC which is readily available within a space shuttle or ship. 
     The temperature switch TS controls the temperature of the cold plate 32 and prevents the heat sink 26 from overheating. Temperature switch TS also includes over-current means for protecting the cooler&#39;s electrical system. In a typical operating situation, the temperature switch TS would turn the thermoelectric elements 28 and the fan F on when the cold plate 32 exceeds 37 F. and off when the cold plate 32 drops below 35 F. If the current in the system exceeds 5 amps or the heat sink temperature exceeds 200 F., the switch TS will disconnect the power supply from the system to preclude any damage. 
     It should be understood that although the preferred embodiment of the refrigeration means of the present invention includes a thermoelectric generator, other forms of refrigeration devices could be utilized to cool the novel cold plate structure of the present invention. Although a typical mechanical refrigeration system, including a condensor, compressor and evaporator coil, would be larger than normally desired, it could be utilized to cool the cold plate 32 of the present invention by placing the evaporator coil thereof in direct thermal contact therewith. It is also possible to use some form of chemical refrigeration device in combination with the cold plate of the present invention, such as a device which would cool by means of an exothermic reaction. However, the thermoelectric generator is the preferred embodiment because of its compact structure and low electrical energy requirements. 
     A refrigerator/freezer combination suitable for use in outer space is illustrated in FIGS. 6 to 9. This refrigerator/freezer can be made to the same dimensions as the inside of a tray designed to fit into a space shuttle storage locker. 
     FIG. 6 illustrates the relative locations of the containers compartment 40, food storage area 42 and freezer compartment 44 disposed side-by-side within a common housing 12A. Within each of these respective compartments is a container cold plate 32, a food cold plate 46 and a freezer cold plate 56. 
     The container refrigeration section of the refrigerator/freezer is of the structure illustrated in FIGS. 1 to 4 inclusive of the thermoelectric generator 20. Cooling of food in the food storage area 42 is affected by the food cold plate 46 which is an extension of container cold plate 32. A divider 48 is provided between the respective cold plates to physically isolate food from the containers SC 1. Details of the food cold plate 46 and divider 48 are illustrated in FIG. 9. Since the food cold plate 46 is an extension of container cold plate 32, food in the storage area is also cooled by the same thermoelectric generator 20 as the cans SC. The freezer compartment 44 is separated from the food storage area by an insulated wall 45 and is provided with a separate access lid 14A. As illustrated in FIG. 7, lid 14A is hinged at H at a side of housing 12A opposite from the location of thermlelectric generator 50 for the freezer compartment which is disposed in a separate housing 52. The walls of housing 12A around the freezer compartment are insulated with a foam insulation 54. 
     Thermoelectric generator 50, for the freezer compartment 44, comprises a plurality of cascaded thermoelectric elements 28A disposed on opposite sides of an interstage plate 58. Interstage plate 58 couples a heat sink HS of the generator 50 to the freezer cold plate 56 through one sidewall of housing 12A. 
     As illustrated in FIG. 8, nine cascaded thermoelectric elements 28A may be provided, three on the cold plate side and six on the heat sink side. The cascading of these elements allows the elements to develop a greater temperature differential. The cascaded arrangement of elements 28 are connected to a suitable power supply by means of leads L1, L2 which pass through holes 60 in heat sink HS. 
     Generator 50 is also provided with a pair of fans F1, F2 which draw air into and through heat sink HS in the direction of the arrows indicated in FIG. 6. Fans F3 performs the same function as fan F illustrated in FIG. 1 with respect to the operation of the thermoelectric generator 20. 
     In order to cycle the respective thermoelectric generators 20 and 50 on and off, to maintain the refrigeration and freezer compartments at appropriate temperatures, an electronic controller EC is provided. This controller includes a two-channel temperature switch. A temperature sensor runs from a first channel of the switch to the refrigerator cold plates 32, 46. By cycling the thermoelectric elements of the generator 20 on and off, the container compartment 40 and food storage area 42 are maintained at approximately 32° F. A second temperature sensor runs from a second channel of the switch to the freezer cold plate 56. In a similar manner, elements 28A and generator 50 are cycled to maintain the freezer compartment 44 at approximately 0° F. 
     It should be understood that the refrigeration device described herein may be modified as would occur to one of ordinary skill in the art without departing from the spirit and scope of the present invention.