US3040539A - Refrigerating apparatus - Google Patents

Description

June 26, 1962 R. s. GAUGLER 3,040,539

' REFRIGERATING APPARATUS Filed April 27, 1960 2 Shets-Sheet 1 JNVENTOR. Rib/70rd S. Gaug/er Fig.2 BYWX.%

His Attorney June 26, 1962 R. s. GAUGLER REFRIGERATING APPARATUS 2 Sheets-Sheet 2 Filed April 2'7, 1960 P type ductor semiwon N type -conducfor semi r m M m 6 m s d m (m m n '10 4 4 m His Attorney atcnt 3,sit,539 Patented June 26, 1952 3,64%,539 REFRIGERATING APPARATUS Richard S. Gaugler, Dayton, Ohio, assignor to General Motors Corporation, Detroit, Mich, a corporation of Delaware Filed Apr. 27, 1960, fier. No. 25,075 7 Claims. (Cl. 62-3) In constructing thermoelectric couples it is very important to obtain uniformity in the size of the elements and uniformity in the resistance of the elements so as to facilitate assembly of a large number of the thermocouples into a single panel in which all elements operate at maximum elficiency. A thermoelectric couple with a lower than average junction resistance, that is, a small resistance between one of the elements and the connecting bar, while operating in the panel, is not being used at its most efiicient current rating due to the larger junction resistance of the other couples. The measured differential temperature for that particular couple is then considerably less than its maximum temperature differential. On the other hand, a couple with a large junction resistance is actually operating at a higher current, in the panel, than at the current where its maximum temperature dilferential will occur. Therefore, neither the couple with the low junction resistance nor the couple with the high junction resistance, is operating at its most efiicient current. This causes a reduction in the measured temperature differential for both couples. The overall effect is that the panel willnot attain a differential as large as predicted by theory because the actual temperature differential is less than the arithmetic mean of the theoretical temperature differentials.

It is an object of this invention to provide an improved construction and arrangement of the thermoelectric units which provides for uniformity in size and which reduces the electrical resistance of each couple to a Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings wherein preferred embodiments of the present invention are clearly shown.

in the drawings:

FIGURE l is a perspective view showing a refrigerator cabinet embodying the invention.

FIGURE 2 is a sectional view taken substantially on line 22 of FIGURE 3 with parts broken away.,

FIGURE 3 is a horizontal sectional view taken substantially on line 3-3 of FIGURE 2.

FIGURE 4 is an enlarged fragmentary elevational view with parts broken away showing the construction of the thermocouples.

Referring now to the drawings wherein a preferred form of the invention is shown, reference numeral 10 designates a refrigerator cabinet having an access opening vvlnch is adapted to be closed by means of a door 14 pivotally supported on the cabinet 10 by hinge means 16 secured to the lower edge of the door 14, a shown in FIGURE 2 of the drawings.

A first thermoelectric cooling panel assembly 20 is mounted adjacent the upper rear of the main food storage compartment 22 and a second thermoelectric cooling panel assembly, generally designated by the reference numeral 24, is arranged in the bottom wall of the food storage compartment 22 for refrigerating ice trays and the like.

Each of the cooling panel assemblies consists of a plurality of thermocouples of the type shown in FIG- URE 4, which are connected in electrical series relationship by copper straps 30. Each thermocouple consists of an n type semi-conductor element 34 and a p type semi-conductor 36. These individual semi-conductors have attached thereto mounting elements 38 which are soldered to the semi-conductor elements 34- and 36. An ultrasonic soldering gun is preferably used for this soldering operation.

By attaching the mounting elements 38 to the relatively fragile semi-conductor materials 34 and 36, it is possible to support the resulting assembly by means of the mounting elements 38 without causing injury to the semiconductor material. By virtue of the construction shown, it is possible to machine the ends of the semi-conductor subassemblies so as to make them all of'uniform length. Furthermore, the arrangement makes it possible to utilize screws 40 for securing the thermocouples to the straps 30 which connect the thermocouples in series electrical relationship. Each of the straps 30 is silver plated as shown at 32 and each of the mounting elements 38 is provided with a silver plating or coating 42 which further improves the contact between the copper straps 30 and the thermocouples.

For purposes of illustration reference has been made to use of silver coatings 32 and 42 for reducing the resistance at the point where the copper straps 39 engage the ends of the thermocouple units whereas other materials such as platinum or gold which serve as good conductors could be used in lieu of the silver. One of the reasons for using silver or the equivalent is that silver oxide is an excellent conductor and, therefore, any oxidation which might take place on the silver at the point of contact between the straps 30 and the thermocouples would not increase the electrical resistance whereas copper oxide is a very poor conductor and if the elements 38 and 30 were made of plain copper Without any silver coating, any

' slight oxide which might form on the copper would materially reduce the efficiency of the thermoelectric 'couples. For purposes of illustration the silver coatings 32 and 42 have been shown as confined to the contacting sides of the elements 30 and 38 whereas the entire elements could be silver coated or silver plated.

After the thermocouples and the copper straps have been assembled, the space between the adjacent thermocouples isfilled by means of Freon filled polyurethane foam 44 of the type disclosed in application Serial No. 809,702, filed April 29, 1959. This foam material is rigid and provides the necessary thermal and electrical insulation between the hot and cold ends of the thermocouples and firmly adheres to the surfaces of the thermocouples and adjacent metallic parts to form a very rigid panel. The Freon used in the cells of the polyurethane is preferably an insoluble retained halogenated hydrocarbon which is an excellent heat insulating medium having a coefficient of heat transfer considerably less than that of air.

panel 2d are bonded to an anodized aluminum plate 59 and the warm ends are bonded to another anodized alumia num plate 52. Y

The bonding is doneby means of an adhesive which is prepared by mixing epoxy resin with a polymeric catalyst. Other bonding mediums could be used if desired. The anodic film on the aluminum plates provides the necessary electrical insulation between the ends of the thermocouples and the plate. The resistance of the anodic film is supplemented by the resistance of the film of epoxy adhesive so that the resulting structure is electrically insulated but heat can readily pass between the thermocouples and the plates bonded to the hot and cold junctions of the thermocouples.

As best shown in FIGURE 2 of the drawings, the thermocouple assembly 20 consists of a block or unit which removably fits into an aperture 60 formed .in the back wall of the cabinet 22. Corrugated metallic fins 62 are secured to the inside plate 50 and serve to form a plurality of air flues 64 which facilitate the flow of convection air currents in thermal exchange relationship with the cold junctions of the thermocouples. The plate 52 has corrugated fins 54 secured thereto which are enclosed by means .of a channel shaped sheet metal element 66 which forms with the plate 52 a vertically extending air flue adjacent the backside of the thermocouples. A blower 68 located beneath the bottom Wall of the compartment 22 serves to forcefully circulate air in thermal exchange relationship with the hot side of the thermocouple assembly. Metallic duct means 70 serves to pull the air downwardly past the heat radiating fins 54 and into the blower inlet 72. The air is discharged through the blower outlet 74 towards the side air outlet grill 76.

The thermocouple assembly 24 located in the bottom wall of the food compartment is used for refrigerating one or more ice trays 80 and consists of an upper plate 82 on which the ice trays rest and. a lower plate84 to which heat dissipating fins 86 are secured. The fan 63 serves to pull air in over the fins 86 as well as over the fins 54.

The usual power pack 90 is mounted beneath the bottom wall of the cabinet and serves to supply direct current to the thermocouples in accordance with well known practice. Since the details of construction of the power pack form no part of the invention and since power packs of the type required are well known, the power pack needs no further description. The plates 82 and 84 are secured to the thermocouples disposed therebetween in the same manner as the plates 50 and 52- are secured to the thermocouples used in making the cooling panel assembly 20.

By virtue of the above described arrangement, it is obvious that highly efiicient thermoelectric panels are produced wherein all thermocouples have substantially equal resistance so as to provide for optimum performance at the designed current flow. Any variation in the resistance in any of the semi-conductor units or elements 34 or 36 can be compensated for by varying the length of the units or elements without varying the final overall length of the element and the mounting elements 38 attached to the ends of the elements.

While the embodiments of the present invention as herein disclosed, constitute preferred forms, it is to be understood that other forms might be adopted.

What is claimed is as follows:

1. In a thermoelectric refrigerator, a plurality of thermocouples each comprising one p and one u type semi-conductor unit, means connecting a plurality of said units in electrical series relationship to form blocks of thermocouples having hot and cold junctions on opposite sides of said blocks,'heat and electrical insulating foam material filling the voids between said units, and a pair of aluminum plates having anodic films thereon secured to opposite sides of said blocks by means of an epoxy resin adhesive, said anodic film and said epoxy resin adhesive serving to electrically but not thermally insulate said plates from said thermocouples.

2. In a thermoelectric refrigerator, a plurality of thermocouples each comprising one p and one u type semi-conductor unit, each of said semi-conductor units having a semi-conductor element secured to a pair of support members by means of solder, all of said units being silver plated, copper straps having silver plating thereon connecting a plurality of said units in electrical series relationship to form blocks of thermocouples having 'hot and cold junctions on opposite sides of said blocks, heat and electrical insulating foam material filling the voids between said units, a pair of aluminum plates having anodic films thereon secured to opposite sides of said blocks by means of an epoxy, resin adhesive, said anodic film and said epoxy resin adhesive serving to electrically but not thermally insulating said plates from said thermocouples.

3. In a thermoelectric refrigerator, a plurality of thermocouples each comprising one p and one u type semi-conductorunit, each of said semi-conductor units having a semi-conductor element secured to a pair of support members by means of solder, all of said units being of equal lengths, the ends of said units being silver plated, copper straps having silver plating thereon con necting a plurality of said units in electrical series rela tionshipto form blocks of thermocouples having hot and cold junctions on opposite sides of said blocks, heat and electrical insulating material filling the voids between said units,-and a pair of aluminum plates having anodic films thereon secured to opposite sides of said blocks by means of an epoxy resin adhesive, said anodic film and said epoxy resin adhesive serving to electrically but not thermally insulating said plates from said thermocouples.

4. In a thermoelectric refrigerator, a plurality of thermocouples each comprising one p and one n type semi-conductor unit connected in series electrical relationship, each of said semi-conductor units including a semiconductor element secured to a pair of support members by means of solder, the ends of said units being silver plated, straps of conducting material having silver plating thereon connecting a plurality of said units in electrical series relationship to form panels of thermocouples having hot and cold junctions on opposite sides of said panels.

5. In a thermoelectric refrigerator, a plurality of thermocuples eachcomprising one p and one 11 type semiconductor unit, each of said semi-conductor units including a semi-conductor element sandwiched between a pair of support members, all of said units being of equal lengths, the ends of said units being silver plated, copper straps having silver plating thereon connecting a plurality of said units in electrical series relationship to form panels of thermocouples having hot and cold junctions on opposite sides of said panels.

6. In a thermoelectric refrigerator, a plurality of thermocouples. each comprising one p and one u type semi-conductor unit, each of said semiconductor units comprising. a pair of support members and a semi-conductor element disposed in abutting relationship between said support member, all of said units being of equal length irrespective of variations in lengths of said semiconductor elements, the ends of said units being silver plated, copper straps having silver plating thereon conmeeting a plurality of said units in electrical series relationship to form blocks of thermocouples having hot and cold junctions on opposite sides of said blocks, heat and electrical insulating foam material filling the voids between said units and bonded to said units and to said connecting means to form a rigid panel.

7. In a thermoelectric device, a plurality of thermocouples each comprising one p and one u type semi conductor unit, each of said semi-conductor units comprising a pair of metallic support members and a semiconductor element sandwiched between said metallic support members, the free ends of said metallic support members being plated with a metal, the oxide of which is a good conductor of electricity, and connector means contacting said plated ends for connecting a plurality of said units in electrical series relationship to form panels of thermocouples having hot and cold junctions on opposite sides of said panels.

References Cited in the file of this patent UNITED STATES PATENTS Gaugler Ian; 29, 1957 Lindenblad i Aug. 5, 1958

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