Thermo-electric refrigerators

May 30, 1961

2,986,009

J. J. GAYSOWSKI

THERMO-ELECTRIC REFRIGERATORS

Filed July 13, 1959

Sheets-Sheet 1

Fig 2

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AMBIENT AIR -- 70° F.

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102

2!

4!

HOT P5 US5

CHAMBER C5 40°-60°F

CHAMBER C4 30°- 40°E

CHAMBER 03 20°-30°F.

CHAMBER C2

IO-2O°E

CHAMBER C! 0°- !0°F.

^TCOLD ~tLS5

HOT P4 US4

BOLD ~tLS4

HOT P3 US3 \tOLD ~ 1lS3'

HOT P2 US2

HOT PJ US!

BOLD ^rLSI

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H8V. 1Φ a-c

101

INVENTOR.

Joseph J. Gaysowski

BY

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Attys.

May 30, 1961

2,986,009

J. J. GAYSOWSKI

THERMO-ELECTRIC REFRIGERATORS

Filed July 13, 1959

Sheets-Sheet 2

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<img file="US2986009A_D0006.tif" />

<img file="US2986009A_D0007.tif" />

INVENTOR.

Joseph J. Gaysowski

BY

<img file="US2986009A_D0008.tif" />

2,986,009

J. J. GAYSOWSKI

THERMO-ELECTRIC REFRIGERATORS

May 30, 1961

Filed July 13, 1959

Sheets-Sheet 3

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T_S3

INVENTOR.

Joseph J. Gaysowski by

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United States Patent Office

2,986,009

Patented May 30, 1961

2,986,009

THERMO-ELECTRIC REFRIGERATORS

Joseph J. Gaysowski, Chicago, III., assignor to General Electric Company, a corporation of New York

Filed July 13,1959, Ser. No. 826,769

Claims. (Cl. 62—3)

The present invention relates to thermo-electric refrigerators, and more particularly to an improved thermoelectric pile for use in such refrigerators and related appliances.

It is a general object of the invention to provide a refrigerator incorporating a thermo-electric pile for the cooling purpose, together with an improved circuit arrangement for selectively controlling the thermo-electric pile.

Another object of the invention is to provide in a refrigerator, or related appliance, an improved arrangement of a thermo-electric pile, so as to cause a Peltier effect as required in the transfer of heat between the appliance and the ambient air.

A further object of the invention is to provide a refrigerator cabinet structure of improved construction and arrangement, including a plurality of storage chambers, a plurality of thermo-electric piles arranged to effect the cascading of heat through a series of the storage chambers.

A further object of the invention is to provide a thermo-electric pile of improved and simplified construction and arrangement that may be readily incorporated in a refrigerator cabinet, or related appliance, in order to govern the transfer of heat between the appliance and the ambient air.

Further features of the invention pertain to the particular arrangement of the elements of the refrigerator and of the elements of the thermo-electric pile, whereby the above-outlined and additional operating features thereof are attained.

The invention, both as to its organization and method of operation, together with further objects and advantages thereof, will best be understood by reference to the following specification, taken in connection with the accompanying drawings, in which:

Figure 1 is a fragmentary vertical sectional view of a refrigerator of the household type incorporating a thermo-electric pile and embodying the present invention;

Fig. 2 is a front elevational view of the refrigerator shown in Fig. 1, with the front door removed from the adjacent cabinet section thereof;

Fig. 3 is a combination schematic illustration of the arrangement of the thermo-electric piles incorporated in the refrigerator of Figs. 1 and 2, and a wiring diagram of the electric circuit control system therefor;

Fig. 4 is an enlarged fragmentary plan view of one of the thermo-electric piles incorporated in the refrigerator of Figs. 1 and 2; and

Fig. 5 is an enlarged vertical sectional view of the thermo-electric pile, taken in the direction of the arrows along the line 5—5 in Fig. 4.

Referring now to Figs. 1 and 2, the refrigerator 10 there illustrated and embodying the features of the present invention is of the household type including an upstanding heat-insulating cabinet section 21 provided with both an open top and an open front, and an associated heat-insulating front door section 31. Also, the refrig10 erator 10 is provided with a supporting base 41 providing an apparatus compartment 42 in which certain apparatus, described more fully hereinafter, is housed. More particularly, the cabinet section 21 includes a rear wall 22, a bottom wall 23 and a pair of side walls 24 and 25; the open top of the cabinet section 21 is closed by a top wall or panel P5; and the interior of the cabinet section 21 is divided into five food storage chambers Cl to C5, inclusive, by four panels Pl to P4, inclusive, arranged in vertically spaced-apart relation between the bottom wall 22 and the top wall or panel P5; whereby the chambers Cl to C5, inclusive, are arranged in a tier.

As clearly illustrated in Fig. 2, the panel Pl comprises a thermo-electric pile dividing the chamber Cl from the chamber C2 and adapted to maintain the temperature of the chamber Cl in the general range 0 to 10° F. and to maintain the temperature of the chamber C2 in the general range 10° to 20° F. The panel P2 comprises a thermo-electric pile dividing the chamber C2 from the chamber C3 and adapted to maintain the temperature of the chamber C2 in the previously mentioned general range 10° to 20° F. and to maintain the temperature of the chamber C3 in the general range 20° to 30° F. The panel P3 comprises a thermo-electric pile dividing the chamber C3 from the chamber C4 and adapted to maintain the temperature of the chamber C3 in the previously mentioned general range 20° to 30° F. and to maintain the temperature of the chamber C4 in the general range 30° to 40° F. The panel P4 comprises a thermo-electric pile dividing the chamber C4 from the chamber C5 and adapted to maintain the temperature of the chamber C4 in the previously mentioned general range 30° to 40° F. and to maintain the temperature of the chamber C5 in the general range 40° to 60° F. The panel P5 comprises a thermo-electric pile separating the chamber C5 from the ambient air and adapted to maintain the temperature of the chamber C5 in the previously mentioned general range 40° to 60° F., when the ambient air has a temperature of 70° F.

Moreover, each of the piles Pl to P5, inclusive, includes a plurality of thermocouples, each including a “hot” junction and a “cold” junction. In the pile Pl, the cold junctions are arranged in heat exchange relation with the air in the top of the chamber Cl, and the hot junctions are arranged in heat exchange relation with the air in the bottom of the chamber C2. In the pile P2, the cold junctions are arranged in heat exchange relation with the air in the top of the chamber C2 and the hot junctions are arranged in heat exchange relation with the air in the bottom of the chamber C3. In the pile P3, the cold junctions are arranged in heat exchange relation with the air in the top of the chamber C3, and the hot junctions are arranged in heat exchange relation with the air in the bottom of the chamber C4. In the pile P4, the cold junctions are arranged in heat exchange relation with the air in the top of the chamber C4 and the hot junctions are arranged in heat exchange relation with the air in the bottom of the chamber C5. In the pile P5, the cold junctions are arranged in heat exchange relation with the air in the top of the chamber C5 and the hot junctions are arranged in heat exchange relation wtih the ambient air exteriorly of the cabinet section 21 and adjacent to the top thereof.

In the refrigerator 10, a plurality of lower screens of foraminous construction LSI to LS5, inclusive, are respectively arranged below and adjacent to the piles Pl to P5, inclusive, for the fundamental purpose of preventing short-circuiting of the thermocouples incorporated therein; and likewise, a plurality of upper screens of foraminous construction US1 to US5, inclusive, are respectively arranged above and adjacent to the piles Pl to PS,, inclusive, for the fundamental purpose of preventing short2,986,009 circuiting of the thermocouples incorporated therein. The screens LSI, etc., and US1, etc., prevent the shortcircuiting of the thermocouples incorporated in the respective piles Pl, etc., without, in any way, interfering with the ready conduction of heat, by convection currents, with respect to the associated piles Pl, etc.; and moreover, the upper screens US1, US2, US3 and US4 serve the additional purpose of food-supporting shelves in the respective food storage chambers C2, C3, C4 and C5.

As generally illustrated in Fig. 2, the refrigerator 10 comprises electrical apparatus 50 housed in the base 41 and supplied with A.-C. power of 118 volts, single-phase; which apparatus 50 supplies direct current in parallel circuit relation to the piles Pl to P5, inclusive. Also, the refrigerator 10 comprises a temperature-responsive device T arranged in the side wall 25 of the cabinet section 21 and subject to the temperature of the storage air in the chamber C3; which temperature-responsive device T preferably takes the form of a thermistor. Also, in the arrangement, the thermistor T is employed for the purpose of selectively controlling the electrical apparatus 50, as explained more fully hereinafter.

Referring now to Fig. 3, in a construction example of the refrigerator 10: the pile Pl comprises 66 thermocouples and occupies an area of approximately 6 x 11; the pile P2 comprises 168 thermocouples and occupies an area of approximately 7 x 24; the pile P3 comprises 316 thermocouples and occupies an area of approximately 11 x 30; the pile P4 comprises 536 thermocouples and occupies an area of approximately 15 x 36; and the pile 55 comprises 1150 thermocouples and occupies an area of approximately 26 x 45. As explained more fully hereinafter, each of the piles Pl, etc., is arranged substantially centrally with respect to the associated partition and each of the partitions is about 27 x 48. In the arrangement: the distance between the rear wall 22 of the cabinet section 21 and the front door 31 in its closed position is approximately 27; the distance between the side walls 24 and 25 of the cabinet section 21 is approximately 48; the lowermost partition Pl is spaced above the bottom wall 22 a distance approximately 12; and the adjacent partitions Pl, P2, etc., are separated from each other by distances of approximately 12. Accordingly, each of the chambers Cl, C2, etc., has a volume approximately 12 x 27 x 48.

As illustrated in Fig. 3, the apparatus 50 essentially comprises a plug 51 that is insertible into an associated socket, not shown, terminating the previously mentioned A.-C. supply source, and a cable 52 connected to the plug 51 and including a pair of conductors 53 and 54, the conductors 53 and 54 being terminated by a switch 55 of the double-pole single-throw type. Further, the apparatus 50 comprises a power transformer 60 including a primary winding 61 and a secondary winding 62, a control transformer 70' including a primary winding 71 and a secondary winding 72, and a magnetic amplifier 80 including a saturable magnetic core 81 provided with an exciting winding 82 and a reactive winding 83. The two output terminals of the power switch 55 are respectively connected to two conductors 56 and 57; the primary winding 71 is bridge across the conductors 56 and 57; and the primary winding 61 is connected in series relation with the reactive winding 83 and bridged across the conductors 56 and 57. The secondary winding 62 is provided with a center tap that is connected to a negative bus 63; and the extremities of the secondary winding 62 are respectively connected by a pair of diode rectifiers 64 and 65 to a positive bus 66, a filtering capacitor 67 being bridged across the negative and positive buses 63 and 66. The secondary winding 72 is provided with a center tap that is connected to a negative bus 73; and the extremities of the secondary winding 72 are respectively connected by a pair of diode rectifiers 74 and 75 to a positive bus 76, a filtering capacitor 77 being bridged across the negative and positive buses 73 and 74.

The apparatus 50 further comprises a control switch 90 provided with a “cool” position and a “defrost” position; which switch 90 comprises three movable switch blades 91, 92 and 93, three stationary front switch blades 94, 95 and 96 and two stationary back switch blades 97 and 98. When the control switch 90 occupies its “cool” position, the movable switch blades 91, 92 and 93 respectively engage the front switch blades 94, 95 and 96; and when the control switch 90 occupies its “defrost” position, the movable switch blades 91 and 92 respectively engage the back switch blades 97 and 98. The negative bus 73 is connected to one terminal of the exciting winding 82; and other terminal of the exciting winding 82 is connected by a conductor 84 to a contact 85 that is operatively associated with a variable resistor 86 that, in turn, terminates a conductor 87. The thermistor T is bridge dacross the conductor 87 and a conductor 88. In the switch 90: the blades 91, 92 and 93 respectively terminate the conductors 63, 66 and 76; the blades 94 and 98 commonly terminate a power supply bus 101; the blades 95 and 97 commonly terminate a power supply bus 102; and the blade 96 terminates the conductor 88.

Considering now the general mode of the operation of the refrigerator 10, and assuming that the plug 51 is inserted into the associated A.-C. power supply source, that the power switch 55 occupies its closed position, and that the control switch 90 controls its “cool” position; the primary winding 71 is energized effecting energization of the secondary winding 72, with the result that a D.-C. voltage appears between the conductors 73 and 76, effecting energization of the exciting winding 82 in series circuit relation with the resistor 86 and the thermistor T, the circuit including the closed switch blades 93 and 96, as well as the conductors 87, 88 and 84. At this time, it may be assumed that the chamber C3 in the refrigerator 10 is “hot” so that the thermistor T has a relatively low resistance, thereby to cause a direct exciting current to traverse the exciting winding 82 that is adequate to cause saturation of the magnetic core 81 of the magnetic amplifier 80, with the result that the reactive winding 83 has very small impedance. Accordingly, a substantial primary current traverses the primary winding 61 in series circuit relation with the reactive winding 83 inducing a substantial voltage in the secondary winding 62, with the result that a substantial D.-C. voltage appears between the buses 63 and 66; the bus 63 is connected via the switch blades 91 and 94 to the supply conductor 101 impressing a negative potential thereupon; and the bus 66 is connected via the switch blades 92 and 95 to the supply conductor 102 impressing a positive potential thereupon. Accordingly, the five thermo-electric piles Pl to P5, inclusive, are energized in parallel circuit relationship between the supply conductors 101 and 102, and the polarity is such that the lower junctions thereof comprises cold junctions and upper junctions thereof comprises hot junctions; whereby the chambers Cl to C5, inclusive, are progressively cooled due to the Peltier effects respectively produced by the piles Pl to P5, inclusive. Specifically, the heat from the chamber Cl is cascaded into the chamber C2 by the pile Pl; the heat from the chamber C2 is cascaded into the chamber C3 by the pile P2; the heat from the chamber C3 is cascaded into the chamber C4 by the pile P3; the heat from the chamber C4 is cascaded into the chamber C5 by the pile P4; and the heat from the chamber C5 is cascaded into the ambient air by the pile P5.

As the cooling operation of the apparatus 50 continues, the temperature in the chamber C3 is lowered, so that the resistance of the thermistor T is correspondingly increased, thereby to increase the resistance of the circuit including the exciting winding 82, with the result that the current traversing the exciting winding 82 is progressively decreased, so as to bring about progressively reduced amounts of saturation of the magnetic core 81 of the £,986, 5 magnetic amplifier 80; whereby the impedance of the reactive winding 83 is correspondingly and progressively increased. As the impedance of the reactive winding 83 is progressively increased, the voltage impressed across the primary winding 61 is progressively reduced, with the 5 result that the D.-C. voltage impressed across the buses 63 and 66 is progressively reduced, causing a corresponding reduction in the voltage impressed across the supply conductors 101 and 102; whereby the currents respectively traversing the piles Pl to P5, inclusive, are correspond- 10 ingly reduced, so as correspondingly to reduce the cooling effects upon the chambers Cl to C5, inclusive. Accordingly, it will be understood that as the temperature of the chamber C4 is reduced, the resistance of the thermistor T is increased, with the result that the im- 15 pedance of the reactive winding 83 is increased, with the result that the voltage impressed between the supply conductors 101 and 102 is reduced, thereby reducing the Peltier effect produced by the piles Pl to P5, inclusive;

whereby the thermistor T controls the apparatus 50 to ²⁰establish the rate of heat transfer by the piles Pl to P5, inclusive, from the refrigerator 10 to the ambient air.

In the arrangement, the piles Pl to P5, inclusive, progressively include larger numbers of thermocouples, as previously explained, so that the piles Pl to P5, in- ²⁵elusive, are capable of transferring progressively larger amounts of heat; whereby ultimately the temperatures of the chambers Cl to C5, inclusive, may be brought respectively into the previously mentioned temperature ranges, progressively decreasing below the ambient tern- ³⁰perature in the downward direction in the tier.

Further, it will be understood that by adjustment of the contact 85 relative to the variable resistor 86, a higher temperature or a lower temperature may be maintained in the refrigerator 10, the temperature maintained being ³⁵lowered as the resistance of the resistor 86 is decreased, and the temperature maintained being raised as the resistance of the resistor 86 is increased. This effect will be readily appreciated when it is observed that the inclusion of additional resistance of the resistor 86 in the circuit ⁴of the exciting winding 82 reduces the exciting current, thereby to bring about an increase in the impedance of the reactive winding 83.

Of course, it will be understood that the effects produced by the thermistor T and the manually adjustable ⁴⁵contact 85 cooperating with the variable resistor 86 are substantially amplified by the magnetic amplifier 80 by virtue of the usual magnetic amplification factor of the magnetic amplifier 80, as is well-understood.

In order to effect defrosting of the refrigerator 10, it is only necessary to reverse the position of the control switch 90; whereby the switch blades 91, 92 and 93 disengage the front switch blades 94, 95 and 96, and the switch blades 91 and 92 respectively engage the back 55 switch blades 97 and 98. This reversal of the control switch 90 reverses the polarity that is applied to the supply conductors 101 and 102; whereby the Peltier effects produced in the piles Pl to P5, inclusive, are reversed, with the result that heat is pumped from the ambient air into the chamber C5 by the pile P5; which heat is cascaded by the piles P4, P3, P2 and Pl, respectively, through the chambers C5, C4, C3, C2 and Cl. More particularly, the reversal of polarity as applied to the supply conductors 101 and 102 brings about the reversal of the normal “hot” junctions and the normal “cold” junctions of the thermocouples in each of the piles Pl, etc.; whereby the heat is pumped from the exterior or ambient air into the refrigerator 10 in the manner described above.

Considering now the construction and arrangement of each of the thermo-electric piles Pl to P5, inclusive, these piles are preferably of the same basic construction, but include a progressively increasing number of thermocouples, as previously explained.

009

Referring now to Figs. 4 and 5, the thermo-electric pile there illustrated may be assumed to be the pile P3; and the composite partition provided in the cabinet section 21 between the chambers C3 and C4 comprises a stationary section 111 and a movable section 112, the stationary section 111 constituting a flat sheet having the previously mentioned dimensions 27 x 48 and having a centrally disposed opening 113 therein into which the movable section 112 is arranged, the opening 113 having the previously mentioned dimensions 11 x 30. The movable section 112 also carries the previously described lower and upper screen respectively indicated at LS3 and US3, the screens LS3 and US3 being of foraminous construction, as previously noted.

Provided through the plate 112 are a number of substantially cylindrical holes that are arranged in a substantially uniform geometric pattern; in odd ones of these holes, there are arranged N-type semi-conductors 114; and in even ones of these holes, there are arranged P-type semi-conductors 115. A first group of metallic conductors 121 are arranged upon the lower side of the plate 112, and a second group of metallic conductors 122 are arranged upon the upper side of the plate 112; which metallic conductors 121 and 122 are substantially identical. In the arrangement, each of the conductors 121 and 122 includes a central bridging strap and a pair of outwardly projecting heat-exchange fins formed integrally therewith. A pair of holes are formed in each of the strap portions in each of the conductors 121 and 122; and electrical connections are formed through the holes mentioned with the adjacent ends of the semi-conductors 114 and 115, as, for example, by soldering, as indicated at 123. Accordingly, the lower group of conductors 121 respectively connect together the adjacent ends of the P-N types of semi-conductors 115—114; and the upper group of conductors 122 respectively connect together the adjacent ends of the N-P types of semi-conductors 114—115; whereby all of the N-type semi-conductors and all the P-type semi-conductors 115 and all of the metallic conductors 121 and 122 are connected in series circuit relationship. As best illustrated in Fig. 5, it will be observed that a first of the conductors 121 is connected via a first of the N-type semi-conductors 114 to a first of the conductors 122; this first conductor 122 is connected via a first of the P-type semi-conductors 115 to a second of the conductors 121; this second conductor 121 is connected via a second of the N-type semi-conductors 114 to a second of the conductors 122; etc. Accordingly, in the arrangement, when a relatively positive potential is connected to the left-hand conductor 121 and a relatively negative potential is connected to the righthand conductor 122, all of the junctions between the semi-conductors 114 and 115 and the conductors 121 comprise “cold” junctions of the corresponding thermocouples and all of the junctions between the semi-conductors 114 and 115 and the conductors 122 comprise “hot” junctions of the corresponding thermocouples. Hence, in the pile P3, all of the “cold” junctions are disposed in heat-exchange relation with the fins of the conductors 121 disposed in the top of the chamber C3 and all of the “hot” junctions are disposed in heat-exchange relation with the fins of the conductors 122 disposed in the bottom of the chamber C4; with the result that the fins of the conductors 121 absorb heat in the chamber C3 and ⁸⁵ transfer this heat through the plate 112 (through the semiconductors 114 and 115) to the conductors 122; and the fins of the conductors 122 deliver this heat into the chamber C4.

₇₀ Considering now in greater detail the constructional example of the thermo-electric pile P3, each of the semiconductors 114 is formed essentially of Bi₂Te₃ and contains a small controlled amount of a “donor” impurity to render the same an N-type semi-conductor; and each γβ of the semi-conductors 115 is formed essentially of Bi₂Te₃

3,986,009 and contains a small controlled amount of an “acceptor” impurity to render the same a P-type semi-conductor. Ordinarily, the donor impurity contained in an N-type semi-conductor is selected from the group consisting of P, As and Sb; and ordinarily, the acceptor impurity contained in a P-type semi-conductor is selected from the group consisting of B, Al, Ga and In. Each of the Ntype semi-conductors 114 is of cylindrical form having a diameter of about %₄ (with a cross-sectional area of 1.0 c.²); and each of the P-type semi-conductors 115 is of cylindrical form having a diameter of about (with a cross-sectional area of 1.1 cm.²). Each of the cylinders 114 and 115 has a length of 1 cm.

The plates or panels 111 and 112 comprise flat sheets and are formed of plastic or ceramic heat-insulating and electrical-insulating material; and preferably, the panel 112 is formed of a phenolformaldehyde condensation product, a melamine resin or a high-density polyethylene, and has a thickness of approximately 1 cm. substantially to match the length of the cylinders 114 and 115. In the arrangement, the material of the panel 112 may be cast in place about the cylinders 114 and 115, or alternatively suitable holes may be first provided through the panel 112 and the cylinders 114 and 115 may be located in the holes and suitably cemented in place therein. Accordingly, the plate 112 also has a thickness of about 1 cm. and the holes formed therein are arranged in a grid-pattern with a space therebetween of about 1 in each of the X and Y directions.

Each of the metallic conductors 121—122 may be formed of copper, or other suitable metal that is both a good thermal conductor and a good electrical conductor. Each of the conductors 121 and 122 may be formed of ribbon stock % wide and %e thick. The strap section of each of the conductors mentioned may be approximately 1% long and each of the fin sections thereof may be approximately long or high.

Further considering the thermocouples provided in the pile P3, the figure of merit of each thermocouple is 2.08ΧΙΟ-³ per °C. (or higher); also, the resistance of each thermocouple is 0.0016 ohm (or less), and the thermal conductivity of each thermocouple is 0.0534 watt per ° C. per cm. (or less). Furthermore, the thermo-electric power of each of the semi-conductors 114— 115 exceeds 200χ 10^-6 volt per ° C.

In the refrigerator 10, each of the panels P2, etc. is constructed to provide a cooling effect that is approximately 100 watts (or 341 B.t.u./hr.) greater than the total heat given off by the panel Pl, etc., disposed therebelow. This arrangement allows each thermo-electric panel or pile P2, etc., to provide sufficient cooling effect for cooling any food, or the like, placed in the associated chamber C2, etc.; and each panel C2, etc., delivers heat at the top side thereof which is equivalent to the heat given off by the panel Cl, etc., disposed therebelow plus the D.-C. power losses in the panel itself plus the heat removed from any food, or the like, stored in the chamber C2, etc., immediately therebelow.

The general performance of the refrigerator 10 is set forth in the two tables, appearing below:

TABLE I

Panel

No. of Thermocouples in Panel

Total Cooling Effect (Watts)

Total Heating Effect (Watts)

Pl (bottom)

P2__________

P3-.......

P4__________

P5 (top)—.

<td> 66</td><td> 100</td>

<td> 168</td><td> 250</td>

<td> 316</td><td> 472</td>

<td> 536</td><td> 803</td>

<td> 1,150</td><td> 1,300</td>

372

703

1,195

2,600

Temperature Difference Between Hot and Cold

Sides of Panel ⁰ F.

10-20

10-20

10-20

10-20

20-30

TABLE Π

<td> Panel</td><td> Average Cooling per Thermocouple (watts)</td><td> Average Power Input per Thermocouple (•watts)</td><td> Average Heat Output per Thermocouple (watts)</td>

<td> Pl (bottom)______________________</td><td> 1.50</td><td> 0. 73</td><td> 2. 23</td>

<td> P2_ .......______________________</td><td> 1.50</td><td> 0. 73</td><td> 2. 23</td>

<td> P3________________________________</td><td> 1. 50</td><td> 0.73</td><td> 2.23</td>

<td> P4 _______________________</td><td> 1.50</td><td> 0. 73</td><td> 2.23</td>

<td> P5 (top)__________________________</td><td> 1.13</td><td> 0. 90</td><td> 2.03</td>

In the foregoing description of the connection and 15 arrangement of the thermo-electric pile P3, it was explained that all of the semi-conductors 114 and 115 and all of the metallic conductors 121 and 122 are connected in series circuit relationship between the power supply conductors 101 and 102 in the refrigerator 10, 20 and this is an entirely satisfactory arrangement with respect to the pile P3 that comprises only 316 thermocouples. However, in the pile P4 that comprises 536 thermocouples, the thermocouples may be arranged in two groups that are connected in parallel relationship with 25 respect to each other; and similarly, in the pile P5 that comprises 1150 thermocouples, the thermocouples may be arranged in four groups that are connected in parallel relationship with respect to each other. This connection of the thermocouples in appropriate series and 30 parallel groups is dependent upon the total number of thermocouples included in the corresponding thermo-electric pile; and in each thermo-electric pile, the number of thermocouples that are connected in series circuit relationship with each other and thus across the power 35 supply conductors 101 and 102 should be related to the number of thermocouples included in the various piles and selected so as to obtain the required current through the series connected thermocouples so as to produce the desired Peltier effects, as explained above, and as par40 ticularly pointed out in the foregoing Tables I and II.

The foregoing data relative to the general performance of the refrigerator 10 are predicated upon the incorporation therein of the thermo-electric piles of the general construction described in conjunction with Figs. 4 45 and 5, wherein the elements 114 and 115 respectively comprises N-type semi-conductors and P-type semi-conductors of the composition and arrangement set forth; however, the thermo-electric piles incorporated in the refrigerator 10 may be entirely conventional. For exam50 pie, in a conventional thermo-electric pile of the general construction and arrangement, as shown in Figs. 4 and 5, the elements 114 are formed of metallic bismuth, the elements 115 are formed of metallic antimony and the conductors 121 and 122 are formed of copper. This ¢5 conventional construction of the pile provides the required hot and cold junctions; however, the operating efficiency of this arrangement is not as high as that of the preferred arrangement, as previously described in conjunction with Figs. 4 and 5.

6Q In view of the foregoing, it is apparent that there has been provided in a refrigerator of the household type an improved arrangement of a number of thermo-electric piles so as to obtain the required cascaded cooling in the several chambers disposed in the tier in the refrigerator ₆₅ cabinet. Also, there has been provided an improved thermo-electric pile and control circuit therefor of simplified connection and arrangement that is suitable for incorporation in a refrigerator, or related appliance of the character described.

7Q While there has been described what is at present considered to be the preferred embodiment of the invention, it will be understood that various modifications may be made therein, and it is intended to cover in the appended claims all such modifications as fall within the 76 true spirit and scope of the invention.

2,986,000