US2581044A

US2581044A - Refrigerating system

Info

Publication number: US2581044A
Application number: US116300A
Authority: US
Inventors: Jack A Ratcliff
Original assignee: Individual
Current assignee: Individual
Priority date: 1949-09-17
Filing date: 1949-09-17
Publication date: 1952-01-01
Anticipated expiration: 1969-01-01

Description

1952 J. A. RATCLIFF 2,581,044

REFRIGERATING SYSTEM 2 Sl-lEETS-SHEET 1 Filed Sept. 17, 1949 ||||||I|| l llllllullllllllll INVENTOR. Jack 4. rPdfc/f %f Jan. 1, 1952 J. A. RATCLIFF REFRIGERATING SYSTEM 2 SHEETSSHEET 2 Filed Sept. 17, 1949 f 0 2 6. W iu LII! T m n n 7 L n Z ww "WM." QM v -L E n r am e n I Q Q 7 e u 6 n a n n a m m n e o 0 a +12 0 u 5 z u F5 4 INVENTOR. Jack 6. Fafc/f/f 3% f '47 NEK Patented Jan. 1, 1952 UNITED STATES PATENT OFFICE R-EFRIGERATING SYSTEM Jack A. Ratclifl, Amarillo, Tex.

Application September 17, 1949, Serial No. 116,300

14 Claims. (Cl. 62-2) The present invention relates in general to refrigerating apparatus and it deals more particularly with dual temperature zone refrigerating apparatus of the primary-secondary type.

It is an object of the invention to provide refrigerating apparatus of the character indicated wherein the temperature of the zone refrigerated by the primary system is adjustable and the zone refrigerated by the secondary system automatically is maintained at substantially uniform temperature despite adjustments made affecting the first mentioned zone.

Another object is to provide refrigerating apparatus of this type wherein the zone refrigerated by the secondary refrigeration system is maintained at substantially uniform temperature regardless of the intermittent operation of the primary system.

A further object of my invention is to provide refrigerating apparatus of the primary-secondary type having an improved arrangement for the exchange of heat between the primary and secondary systems. More specifically it is an object to provide an arrangement for varying the rate of heat exchange between the primary and secondary systems and automatically controlling the variation in accordance with the needs of the secondary system.

One of the features of the invention lies in the provision of a primary evaporator and a secondary condenser in heat exchange relation, the heat exchange being effected by a liquid whose level may be raised or lowered to alter the rate thereof.

Another feature resides in the provision of a novel arrangement for controlling the level of the aforementioned liquid in accordance with the temperature of the secondary evaporator or the zone refrigerated by it.

Other and further objects together with the features of novelty by which the objects are achieved will appear in the course of the following description of the invention.

In the accompanying drawings which form a part of the specification and are to be read in conjunction therewith, and in which like reference numerals are employed to indicate like parts of the various views:

Fig. 1 is a schematic drawing of a refrigerator employing my improved refrigeration system,

Fig. 2 is an enlarged horizontal cross-section of the secondary condenser of my refrigeration system, taken along lines 2-4 of Fig. 1 in the direction of the arrows. the control bellows being shown in contracted condition,

Fi 3 is a vertical cross-section of the secondary condenser taken along the line 3-3 of Fig. 2 in the direction of the arrows,

Fig. 4 is a fragmentary cross-section of the lower part of the secondary condenser, taken along line 44 of Fig. 2, the control bellows being shown in expanded condition,

Fig. 5 is a side elevation of a modified form of secondary condenser according to the invention, part being broken away in order to show the position of the control diaphragm whenthe solenoid is energized,

Fig. 6 is a horizontal cross-section taken along the lines 66 of Fig. 5 in the direction of the arrows,

Fig. 7 is a vertical cross-section taken along line l-l of Fig. 6 showing the position of the control diaphragm when the solenoid is de-energized, and

Fig. 8 is a schematic diagram of the circuits for controlling the solenoid shown in Figs. 5 to 7 inclusive.

Referring more particularly to Fig. 1, the cabinet of a household or kitchen type refrigerator is indicated diagramatioally in dotted lines: This has a pair of hinged front doors I0 and H which, when opened, give access respectively to an upper compartment l2 and a lower compartment [4, the two compartments being separated from one another by a horizontal partition or baflle IS.

The lower compartment is designed for conventional refrigerated food storage, the optimum temperature of which is in the neighborhood of 40 F. The upper compartment, on the other hand, is designed for freezing ice cubes and freezing or holding in frozen condition the various comestibles placed therein; while its temperature may be varied or adjusted, as will be explained hereinafter, it preferably should be within the range of minus 10 F. to plus 15 F. For convenience in distinguishing between the two compartments, the upper one will be referred to hereinafter as the freezer zone and the lower one as the storage zone.

Each of these zones has its own cooling coil or evaporator, the one for the freezer compartment being designated by the numeral [8 and the one for the storage compartment by the numeral 20. It will be understood that the showing of both evaporators in Fig. 1 is largeli schematic, it being intended that in the case of either one the evaporator may be a compact unit within the compartment but occupying less than all the space therein, or, alternatively, that the cooling coil may be formed within, or as a liner for, some or all of the walls of the compartment in question.

The evaporator I8 and the evaporator 20 actually comprise parts of two separate closed refrigeration systems, the former evaporator being in the primary system and the latter in the secondary system. The primary system also includes a compressor 22 and a primary condenser 24 which are of any conventional or suitable construction and may be situated in the bottom of the cabinet as shown, or in any other convenient location. The cooling coil 18 has one end connected to a downwardly extending duct 28 which leads to the suction side of the compressor. Disposed alongside the major portion of this duct in heat exchange relation thereto is a capillary tube 28, the lower end of which is connected through a strainer 30 to the outlet of the condenser; the upper end of the capillary tube is connected to the other end of coil I! through a heat exchange coil 32 which is looped back and forth in zig-zag fashion around and in thermal contact with the shell 34 of a secondary condenser.

As best seen in Figs. 2 and 3, the secondary condenser comprises a double wall vessel having an outer shell 34 and a closely spaced inner shell 36, the annular space between the two shells being somewhat exaggerated in the drawings, however, for the sake of clarity. Although the vessels are illustrated as concentric cylinders having parallel vertical walls, they may be of other shapes, having, for example, upwardly or downwardly converging walls, the effect of which will be evident from the ensuing description. Both ends of the storage zone evaporator 20 communicate with the inner vessel, one end being connected thereto by a-tube 33 which terminates flush with the bottom of the vessel and the other by a tube which extends up to a point near the top of the vessel; both tubes are soldered or otherwise sealed relative the vessel where they enter same. The inner vessel contains a suitable refrigerant such as Freon and, together with evaporator 20, comprises the closed secondary refrigeration system.

It will be convenient at this point to briefly outline the refrigeration cycle of the primary and secondary systems, and the thermal relation between the two. Referring first to the primary system, the compressor 22 draws the heat laden vaporized refrigerant from the evaporator it through the suction line 26, compresses the vapor and discharges it under high pressure into the primary condenser 24. In the primary condenser the vapor condenses and in changing into liquid phase gives up its heat to the ambient air. The liquid refrigerant then passes through the strainer 30 into the capillary tube 28 where it is conducted to the secondary heat exchange coil 32. The latter coil is of greater crosssectional area than the capillary tube, so that the pressure, and hence the temperature, of the refrigerant liquid is reduced on entering coil 32.

Since coil 32 is tightly clamped around the secondary condenser, it will refrigerate the latter. A mixture of low pressure liquid and vapor passes out of the secondary heat exchanger coil 32 to the top of the evaporator 18. In the evaporator it takes up heat from the upper compartment l2, refrigerating the latter, and the vaporized refrigerant then is drawn back to the compressor through the suction line 26; the comparatively cool suction vapor passing through this line absorbs some of the heat from the liquid passing through the capillary tube 23 which is in heat exchange relation thereto, and this considerably increases the efficiency of the primary system.

The refrigeration effect of the secondary heat exchange coil 32 condenses the vaporized refrigerant in the upper portion of vessel 35. This reduces the pressure in the vessel and accordingly the liquid refrigerant in the secondary evaporator 20 starts vaporizing. The condensed refrigerant in the vessel 36 drains out through tube 38 and enters the bottom of evaporator 20 in liquid phase; the vapor formed in the evaporator at the same time leaves the top thereof and passes upwardly through tube 40 back into the vessel 33 completing the cycle of the secondary system.

The electrical connections controlling the compressor have been omitted from the drawings for the sake of clarity since they are conventional and form no part of the present invention; as is well understood by those versed in the art, the

compressor preferably is so operated as to maintain the zone refrigerated by evaporator l3 at a relatively constant temperature, which temperature is selectable or adjustable within predetermined limits. Customarily this is accomplished by operating the compressor under control of a manually adjustable thermostat located in the refrigerated zone (clamped on the evapora tor It, for example) but as previously suggested, any suitable arrangement for selecting the temperature and automatically maintaining the selected temperature in the freezer zone l2 may be employed.

Whatever the nature of the temperature control for the primary refrigeration system, it will be evident that when the refrigeration effect upon the freezer compartment i2 is increased or decreased incident to altering the selected temperature of the compartment, there is a corresponding increase or decrease in the refrigeration effect of coil 32 upon the secondary condenser. Consequently, there is a tendency for a change in the control of the primary refrigeration system to be reflected by a corresponding change in the secondary system, with the result that the temperature of storage compartment i4 tends to shift up or down. Such a shift, however, would be very undesirable for if the temperature in the storage compartment shifts upwardly from the narrow optimum range, the perishable foodstuifs therein are not suihciently refrigerated to prevent bacterial action; on the other hand, if the temperature shifts downwardly from the optimum value it results in undue dehydration of the foodstuffs.

It is an important feature of the present invention that the temperature of the storage compartment l4 remains substantially constant regardless of adjustments made to raise or lower the temperature of the freezer compartment l2 and regardless of other factors that might otherwise tend to disturb the temperature of the storage compartment. The manner in which this result is achieved now will be described.

Referring to Figs. 1, 2 and 4 it will be seen that the shell 34 of the secondary condenser is provided with a laterally extending integral housing 42 containing a bellows 44, to which bellows a bulb 46 is connected by a small tube 48 entering the housing through a suitable seal or packing gland. Preferably the bulb is located in the storage zone M as shown, or, to achieve the same end, clamped on the evaporator 20 near the outlet thereof; if desired, however, it may be situated in compartment l2 or otherwise associated with evaporator l8.

The bellows, tube and bulb comprise a hermetically sealed unit containing a thermo-expansive gas such as Freon. Thus, as the bulb 46 is warmed the gas expands, expanding the bellows (see Fig. 4) and when it is cooled, the gas contracts, contracting the bellows (see Fig. 2). Around the bellows and in the space between the walls of

vessels

34 and 36 is a heat conducting inner vessel as shown in Fig. 3; but when the bellows fully expands, the liquid is forced upwardly in the annular space between the inner and outer walls, raising the level to a point at or near the top of the vessel.

The function of liquid 50 is to vary the rate of heat transfer between the inner and outer shells of the secondary condenser. Because the thermo conductivity of the liquid is high as compared to the thermo conductivity of air, the refrigeration effect produced by coil 32 upon the secondary system is greatest when the space between the inner and outer shells of the secondary condenser is filled with liquid, and is least when the liquid level drops so that the space is filled only with air. Between these maximum and minimum conditions of heat transfer there are, of course, innumerable intermediate values, each depending upon the exact position of the surface of the liquid between the aforementioned upper and lower limits of its travel.

For purposes of illustrating the operation of my device let it be assumed that compartment I2 is at F., compartment 14 at 40 F., and that under these conditions the surface of liquid 50 is at a level approximately midway between the top and bottom of vessel 36. In the event door II is opened for an appreciable interval, some of the cool air in compartment I4 is replaced by warm air, and the consequent warming of bulb 46 causes bellows 44 to expand as explained hereinbefore. This raises the level of liquid 50 so that heat is extracted from the secondary refrigeration system by coil 32 more rapidly than before; as the temperature in compartment 14 now drops due to the increased refrigeration effect of the secondary system, the level of liquid 50 also drops, slowing down the rate of heat transfer and preventing the food storage compartment I4 from becoming too cool.

Suppose now that the activity of the primary refrigeration system is increased, either as the result of frequent or prolonged opening of door ID, or as a result of a re-setting of a thermostatic control to make compartment l2 colder than before. This naturally increases the refrigeration effect of coil 32 upon the secondary system and begins to reduce the temperature ofcompartment M; however, when this occurs, bellows 44 begins to contract under control of bulb 46, lowering the level of liquid 50 and reducing the rate at which heat is extracted from the secondary system. Thus it will be seen that whether the refrigeration effect of the primary system is accelerated or decelerated, such compensation will automatically be effected by liquid 50 as will maintain the refrigeration of compartment l4 substantially uniform.

A modified arrangement for achieving the same end by electrical control rather than purely mechanical control is shown in Figs. to B inclusive. Here there has been substituted for the bellows of the secondary condenser a two-piece housing 50 having a flexible diaphragm 52 clamped between the two halves. This housing is .supported on the secondary condenser by a pipe 54 through which the chamber below the diaphragm communicates with the interior of shell 34. Above the housing is a solenoid 5-6 whose vertically shiftable core 58 is connected to the diaphragm as shown; Fig. 5 illustrates the position of the diaphragm when the solenoid is energized, and Figs. 7 and 8 show its position when the solenoid is de-energized. It will be understood that under theformer condition the surface of liquid 50 is at or near the bottom of the inner vessel 36 and that under the latter condition it is at or near the top of the vessel. Except for this modification in the arrangement for controlling the liquid level, the structure and relationship of the primary and secondary refrigeration systems is as previously described.

Fig. 8 is a schematic diagram of the circuit for controlling the solenoid and the compressor motor. Numeral 60 indicates a switch thermostatically controlled by the compartment or evaporator temperature in the freezer zone l2, and numeral 62 indicates a switch thermostatically controlled by the compartment or evaporator temperature in the food storage zone H. Each switch will shift to its high position when the temperature of the associated thermostat rises to or above the upper limit for which it has been set, and will shift to its low" position when the thermostat temperature drops to or below the lower limit for which it has been set. As is conventional, it should be understood that each thermostat is adjustable in order to vary the upper and lower limits of its operation.'

Considering the circuit operation more in detail, it will be seen that when either switch is in its high position (which means that the associated compartment or evaporator has reached as high a temperature as is desirable and hence that it is a need of refrigeration) a circuit is completed through that switch from conductor 64 of the power line to conductor 66.

of the compressor motor; the other side of the motor (68) is connected directly to the remaining power conductor 10, so the compressor will operate, supplying the necessary refrigeration as long as either compartment needs it, that is, as long as the associated switch 60 or 62 remains in its high position.

It also will be noted that so long as switch 62 is in its high" position, solenoid 56 remains de-energized and hence, as shown in Fig. 7, the heat transfer liquid 50 completely fills the space between the inner and

outer shells

34 and 36 of the secondary condenser. Accordingly, it will be clear from the earlier explanation that the heat is extracted from the secondary refrigeration system at the maximum rate in order that the evaporator in the food storage zone ll will supply its maximum refrigerating effect.

In the event that switch 62 shifts to its "low" position while switch 60 remains in the "high" position, solenoid 56 is energized over a circuit which extends fromsupply conductor 64 through switch 60 thence through the solenoid winding, switch 62 and back to the power supply conductor 10. The energization of the solenoid causes liquid 50 to drop as shown in Fig. 5, im-- mediately reducing the rate of heat transfer between the inner and outer shells of the secondary condenser; by reducing the refrigeration effect of the secondary system, this prevents the temperature in the food storage zone l4 from dropping too low even though the primary system is continuing to refrigerate the freezer Ton I2 at its maximum rate.

When switch 60 shifts to its low position, t e aforementioned circuit for the comprezsor motor is opened halting the same; at the state time the circuit for solenoid 56 also is opened, as a result of which liquid 50 is again raised to its uppermost level insuring that the secondary refrigeration system gets maximum benefit of the now reduced refrigeration eflect of coil 32.

The system now will remain in this condition until one or the other of the compartments becomes warm enough to shift the associated switch to its "high position. If it is switch 62 which operates first this will start the compressor without re-energizing thesolenoid and thus insure that the associated food storage zone 14 receives the maximum benefit of the refrigeration cycle. If, on the other hand, it is switch 80 which operates first, this will not only start the compressor but will re-energize the solenoid insuring that the freezer zone I: is supplied the necessary refrigeration without over-cooling the storage zone 14.

It will be clear from the foregoing description and explanation that the salient novelty of my invention resides in the construction and relationship of the primary and secondary refrigeration systems and particularly in the arrangement whereby I vary the heat transfer between the two systems. The character of the cabinet or cabinets housing the evaporator or cooling coils of the respective systems is of only incidental importance and is subject to many variations without departing from the invention. The freezer and storage zones may, for example, be separate compartments in the same cabinet as shown, or maybe located in two separate and independent cabinets; alternatively, they may not onhr be in the same cabinet but may be in limited communication with one another, for example, by the provision of apertures or ports in the baflie I, or by the provision of a single unitary door opening both compartments simultaneously rather than selectively by separate doors.

It should also be understood that I do not wish to be limited to the use of any particular refrigerant in either the primary or the secondary refrigerating system, or, to any particular liquid for my heat transfer liquid 50, it only being necessary that the liquid have adequate thermo conductivity and that it remain in liquid phase at all temperatures to which it is subjected in the normal operation of the apparatus. Various gases likewise may be employed for expanding and contracting the bellows M under control of bulb l6 and my invention contemplates the use of any satisfactory gas or mixture of gases for this purpose.

Inasmuch as many possible embodiments of the invention may be made without departure from the scope thereof, it is to be understood that all matter herein set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

From the foregoing it will be apparent that this invention is one well adapted to attain all of the ends and objects hereinbefore set forth together with other advantages which are obvious and which are inherent to the apparatus.

It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations. This is contemplated by Ed is within the scope of the appended claims.

Having thus described my invention, I claim:

1. In refrigerating apparatus, a primary refrigerant circuit including a primary evaporator having a first portion and a second portion, a secondary refrigerant circuit including a secondary evaporator and a secondary condenser, a heat exchanger constructed and arranged to conduct heat from the secondary condenser to said first portion of the primary evaporator. a low temperature compartment cooled by the second portion of the primary evaporator, a higher temperature compartment cooled by the secondary evaporator, each of said compartments having a thermo-responsive device controlled in accordance with the temperature in that compartment, and said heat exchanger including means controlled conjointly by both of said devices for varying the rate of heat transfer from the secondary condenser to said first portion of the primary evaporator.

2. In refrigerating apparatus. a primary refrigerant circuit including a primary evaporator having a first portion and a second portion, a secondary refrigerant circuit including a secondary evaporator and a secondary condenser, a heat exchanger constructed and arranged to conduct heat from the secondary condenser to said first portion of the primary evaporator, a low temperature compartment cooled by the second portion of the primary evaporator, a higher temperature compartment cooled by the secondary evaporator, each of said compartments having a thermo-responsive device controlled in accordance with the temperature in that compartment, said heat exchanger including means controlled conjointly by both of said devices for varying the rate of heat transfer from the secondary condenser to said first portion of the primary evaporator, said last means operative at times to increase said rate of heat transfer responsive to an increase in the temperature of the higher temperature compartment and operative at other times to increase said rate of heat transfer responsive to a reduction in the temperature of the lower temperature compartment.

3. In refrigerating apparatus, a primary refrigerant circuit including a primary evaporator having a first portion and a second portion, a secondary refrigerant circuit including a secondary evaporator and a secondary condenser, a heat exchanger constructed and arranged to conduct heat from the secondary condenser to said first portion of the primary evaporator, a low temperature compartment cooled by the second portion of the primary evaporator, a higher temperature compartment cooled by the secondary evaporator, each of said compartments having a thermo-responsive device controlled in accordance with the temperature in that compartment, said heat exchanger including means controlled conjointly by both of said devices for varying the rate of heat transfer from the secondary condenser to said first portion of the primary evaporator, said last means operative at times to reduce said rate of heat transfer responsive to a reduction in the temperature of the high temperature compartment and operative at other times to reduce said rate of heat transfer responsive to an increase in the temperature of the lower temperature compartment.

4. In refrigerating apparatus, a primary refrigerant circuit including a primary evaporator having a first portion and a second portion, a secondary refrigerant circuit including a secondary evaporator and a secondary condenser, a heat exchanger constructed and arranged to conduct heat from the secondary condenser to said first portion of the primary evaporator, a low temperature compartment cooled by the second portion of the primary evaporator, a higher temperature compartment cooled by the secondary evaporator, each of said compartments having a thermo-responsive device controlled in accordance with the temperature in that compartment, said heat exchanger including means controlled conjointly by both of said devices ior varying the rate of heat transfer from the secondary condenser to said first portion of the primary evaporator, said last means constructed and arranged to maintain said rate of heat transfer at a minimum whenever the lower temperature compartment is above a predetermined temperature and the higher temperature compartment concurrently is below a predetermined temperature, and said last means controlled by said devices to increase the rate of heat transfer responsive either to the lower temperature compartment dropping below said first predetermined temperature or the higher temperature compartment rising above said second predetermined temperature.

5. In refrigerating apparatus, a primary refrigerant circuit including a primary evaporator having a first portion and a second portion, a

secondary refrigerant circuit including a secondary evaporator and a secondary condenser, a heat exchanger constructed and arranged to conduct heat from the secondary condenser to said first portion of the primary evaporator, a low temperature compartment cooled by the second portion of the primary evaporator, a higher temperature compartment cooled by the secondary evaporator, each of said compartments having a thermo-responsive device controlled in accordance with the temperature in that compartment, a compressor for said primary refrigerant circuit controlled conjointly by both of said devices to operate whenever the temperature in either compartment rises above a predetermined minimum value for that compartment, and said heat exchanger including means controlled conjointly by both of said devices for varying the rate of heat transfer from the secondary condenser to said first portion of the primary evaporator.

6. In refrigerating apparatus, a primary refrigerant circuit including a primary evaporator having a first portion and a second portion, a secondary refrigerant circuit including a secondary evaporator and a secondary condenser, a heat exchanger constructed and arranged to conduct heat from the secondary condenser to said first portion of the primary evaporator, a low temperature compartment cooled by the second portion of the primary evaporator, a higher temperature compartment cooled by the secondary evaporator, each of said compartments having a thermo-responsive device controlled in accordance with the temperature in :that compartment, a compressor for said primary refrigerant circuit controlled conjointly by both of said devices to operate whenever the temperature in either compartment rises above a predetermined minimum value for that compartment, and said heat exchanger including means controlled conjointly by both of said devices for varying the rate of heat transfer from the secondary condenser to said first portion of the primary evaporator, said last means operative at times to increase said rate of heat transfer responsive to an increase in the temperature of the higher temperature compartment above said predetermined minimum value for that compartment and operative at other times to increase said rate of heat transfer responsive to a reduction in the temperature of the lower temperature compartment below said predetermine 1 minimum for that compartment.

7. In refrigerating apparatus, a primary re- 10 frigerant circuit including a primary evaporator having a first portion and a second portion, a secondary refrigerant circuit including a secondary evaporator and a secondary condenser. a heat exchanger constructed and arranged to conduct heat from the secondary condenser to said first portion of the primary evaporator, a low temperature'compartment cooled by the second portion of the primary evaporator, a higher temperature compartment cooled by the secondary evaporator, each of said compartments having a thermo-responsive device controlled in accordance with the temperature in that compartment, a compressor for said primary refrigerant circuit controlled conjointly by both of said devices to operate whenever the temperature in either compartment rises above a predetermined minimum value for that compartment, said heat exchanger including means controlled conjointly by both of said devices for varying the rate of heat transfer from the secondary condenser to said first portion of the primary evaporator, said last means operative at times to reduce said rate of heat transfer responsive to a reduction in the temperature of the higher temperature compartment below said predetermined minimum value for that compartment and operative at other times to reduce said rate of heat transfer responsive to an increase in the temperature of the lower temperature compartment above said predetermined minimum value for that compartment.

8. In refrigerating apparatus, a primary refrigerant circuit including a primary evaporator having a first portion and a second portion, a secondary refrigerant circuit including a secondary evaporator and a secondary condenser, a low temperature compartment cooled by said first portion of the primary evaporator, a higher temperature compartment cooled by the secondary evaporator, each of said compartments having a thermo-responsive device controlled in accordance with the temperature in that compartment, a variable heat exchanger for conducting heat from the secondary condenser to the second portion of the primary evaporator, said exchanger comprising an intermediate chamber between the secondary condenser and said second portion, a liquid storage reservoir communicating with said intermediate chamber, and means controlled conjointly by both of the said thermoresponsive devices for at times transferring liquid from said reservoir into said chamber and at other times transferring liquid from} ;said chamber into said reservoir.

9. In refrigerating apparatus, a primary refrigerant circuit including a primary evaporator having a first portion and a second portion, a secondary refrigerant circuit including a secondary evaporator and a secondary condenser, a low temperature compartment cooled by the first portion of the primary evaporator, a higher temperature compartment cooled by the secondary evaporator, each of said compartments having a thermo-responsive device controlled in accordance with a temperature in that compartment, a variable heat exchanger for conducting heat from the secondary condenser to the second portion of the primary evaporator, said exchanger comprising an intermediate chamber between the secondary condenser and said second portion, a liquid storage reservoir communicating with said intermediate chamber, and means controlled conjointly by said thermo-responsive devices for at times transferring liquid from said reservoir into said chamber responsive to an increase in the temperature of the higher temperature compartment and at other times transferring liquid from said reservoir into said chamber responsive to a decrease in temperature of the lower temperature compartment.

10. In refrigerating apparatus, a primary refrigerant circuit including a primary evaporator having a first portion and a second portion, a secondary refrigerant circuit including a secondary evaporator and a secondary condenser, a low temperature compartment cooled by the first portion of the primary evaporator, a higher temperature compartment cooled by the secondary evaporator, each of said compartments having a thermo-responsive device controlled in accordance with a temperature in that compartment, a variable heat exchanger for conducting heat from the secondary condenser to the second portion of the primary evaporator, said exchanger comprising an intermediate chamber between the secondary condenser and said second portion, a liquid storage reservoir communicating with said intermediate chamber, and means controlled conjointly by said thermo-responsive devices for at times transferring liquid from said chamber into said reservoir responsive to a decrease of a temperature of the higher temperature compartment and at other times transferring liquid from said chamber into said reservoir responsive to an increase in the temperature of the lower temperature compartment.

11.-In refrigerating apparatus, a primary refrigerant circuit including a primary evaporator having a first portion and a second portion, a secondary refrigerant circuit including a secondary evaporator and a secondary condenser, a low temperature compartment cooled by said first portion of the primary evaporator, a higher temperature compartment cooled by the secondary evaporator, each of said compartments having a thermo-responsive device controlled in accordance with the temperature in that compartment, a variable heat exchanger for conductin heat from the secondary condenser to said second portion of the primary evaporator, said exchanger comprising an intermediate chamber between the secondary condenser and said second portion, a closed liquid storage reservoir communicating with said intermediate chamber, one wall of said reservoir comprising a flexible membrane, a plunger engaging said membrane and movable to flex the membrane thereby to vary the liquid capacity of said reservoir, and means controlled conjointly by both thermo-responsive devices for moving said plunger thereby to transfer liquid from said reservoir into and out of said intermediate chamber.

12. In refrigerating apparatus, a primary refrigerant circuit including a primary evaporator havin a first portion and a second portion, a secondary refrigerant circuit including a secondary evaporator and a secondary condenser, a low temperature compartment cooled by said first portion of the primary evaporator, a higher temperature compartment cooled by the secondary evaporator, each of said compartments having a thermo-responsive device controlled in accordance with the temperature in that compartment, a variable heat exchanger for conducting heat from the secondary condenser to the second portion of the primary evaporator, said exchanger comprising an intermediate chamber 12 between the secondary condenser and said second portion. a closed liquid storage reservoir communicating with said intermediate chamber, one wall of said reservoir comprising a flexible membrane, a plunger engaging said membrane and movable to flex the membrane thereby to vary the liquid capacity of said reservoir and thus transfer liquid from said reservoir into and out .of said intermediate chamber, a solenoid for actuating said plunger, and temperature controlled means for intermittently energizin said solenoid.

13. In refrigerating apparatus, a primary refrigerant circuit including a primary evaporator having a first portion and a second portion, a secondary refrigerant circuit including a secondary evaporator and a secondary condenser, a low temperature compartment cooled by said first portion of the primary evaporator, a higher temperature compartment cooled by the secondary evaporator, each of said compartments having a thermo-responsive device controlled in accordance with the temperature in that compartment, a variable heat exchanger for conducting heat from the secondary condenser to said second portion of the primary evaporator, said exchanger comprising an intermediate chamber between the secondary condenser and saidsecond portion, a liquid storage reservoir communicating with said intermediate chamber, means for varying the liquid capacity of said reservoir thereby to transfer liquid from said reservoir into and out of said intermediate chamber, a solenoid for actuating said means, and a circuit for said solenoid includin a pair of switches controlled respectively by said thermo-responsive devices.

14. In refrigerating apparatus, a primary refrigerant circuit including a primary evaporator having a first portion and a second portion, a secondary refrigerant circuit including a secondary evaporator and a secondary condenser, a low temperature compartment cooled by said first portion of the primary evaporator, a higher temperature compartment cooled by the secondary evaporator, each of said compartments having a thermo-responsive device controlled in accordance with the temperature in that com partment, a variable heat exchanger for conducting heat from the secondary condenser to said second portion of the primary evaporator, said exchanger comprising an intermediate chamber between the secondary condenser and said second portion, a liquid storage reservoir communicating with said intermediate chamber, means for varying the liquid capacity of said reservoir thereby to transfer liquid from said reservoir into and out of said intermediate chamber, a solenoid for actuating said means, a circuit for said solenoid including a pair of switches controlled respectively by said thermoresponsive devices, and a compressor for said primary refrigerant circuit controlled conjointly by said switches.

JACK A. RATCLIFF.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,887,687 Killeffer Nov. 15, 1932 1,951,496 Stevens Mar. 20, 1934 2,116,389 Fiene May 3, 1938 2,492,648 McCloy Dec. 27, 1949