US2492610A - Refrigeration - Google Patents

Description

E. W. ZEARFOSS, JR

Dec. 27, 1949 REFRIGERAT ION 2 Sheets-Sheet l Filed Nov. 30, 1944 Lwenan.

Zearfass 5 il rn@ 5 Y @75% 5 Dec. 27, 1949 E. w. vzlzRFosss, JR I 2,492,610

REFRIGERATION 2 Sheets-Sheet 2 Filed Nov. 30, 1944 2*:- OSS Jin". 2411633 Patented Dec. 27, 1949 RErmcEnA'rloN Ehner W. Zearfoss, Jr., Philadelphia, Pa., assignor, by mesne assignments, to Philco Corporation, Philadelphia, Pa., a corporation of Penn- Sylvania Application November 30, 1944, Serial No. 565,842

12 Claims. (Cl. 62-115) pression may, of course, be obtained by redesigning the motor-compressor units now in use, to increase the capacity or volumetric displacement of such units. This, however, necessitates enlarging the overall dimensions of the unit as well as increasing the size and power of the motor re- .quired to drive the compressor, with the result that the unit requires additional space for its mounting within the refrigerator cabinet structure, which space could be used to greater advantage for refrigerated storage. The use of known multi-stage compressor units embodying multiple pistons and cylinders, still have the disadvantages above mentioned, in that the added pistons and compression chambers vadd to the size of the units and demand relatively large and powerful motors.

It is an object of this invention to provide a method and system whereby, in domestic refrigerators of the special type above referred to, the evaporator or expanded refrigerant may be compressed adequately by means of commercially known motor-compressor units now commonly used in conventional domestic refrigerators, without necessitating the redesigning of such units and without requiring material changes in' the basic structure thereof, so that no more space than has heretofore been required is needed to mount the units in the refrigerator cabinets.

It is also an object of the invention to provide a system for compressing evaporated or expanded refrigerant to the required pressure to assure its condensation for recirculation in an evaporator intended to cool a space at low freezing temperatures, the system being such that compression of the refrigerant is effected in two stages by means of the single piston and cylinder of a type of motor-compressor unit now available on the market.

Another object of the invention is vthe provision of a refrigerant compressing system for use in a refrigerating circuit intended to cool a space at low freezing temperatures, said system employing a type of compressor heretofore used for single compression to perform multi-stage compression.

Still another and more specific .object of the invention is to provide a method of and system for obtaining two-stage compression by means of .the generally known single-stage hermetic motor-compressor unit which heretofore has been commonly used in ordinary domestic refrigerating circuits.

The invention is further characterized by the provision of a refrigerant two-stage compression system utilizing a compressor of the single compression chamber type, which, in addition to its primary function of adequately compressing the refrigerant, provides a space wherein the pressure of the refrigerant may be raised to the proper value between the first and second stages for the purpose of effecting two-stage compression.

Other objects and characteristic features of the invention will appear from the following description and from the accompanying drawings, in which:

Figure 1 is a semi-diagrammatic representation of the system of the invention and its method of operation; and f Figure 2 is a transverse vertical sectional view of a hermetic motor compressor unit incorporating the features of the invention and illustrating a refrigerating circuit connected therewith.

As illustrated in the drawings', the refrigerant compression system is included in the refrigerant 1 circuit which, conventionally, contains an evaporator l and 4a condenser 2, a suitable refrigerant flow restrictor 3 being interposed between said evaporator and condenser. The compression system basically comprises a compression chamber C, a hermetically sealed zone S and pressure'responsive means M, the latter being adapted to control the initiation .of the first and second stage operations of said system.

In accordance with the method of this invention, during first stage operation of the system, expanded or evaporated refrigerant at suction pressure, say, 15 pounds per square inch absolute,v is drawn from the evaporator I into the compression chamber C, and is pumped from said chamber into the hermetically sealed zone S against interstage pressure of minimum value, say, 50 pounds per square inch absolute, until the pressure in the latter is raised to a predetermined maximum interstage value, say, 55 pounds per square inch absolute, whereupon the pressure responsive means M is actuated to initiate the second stage operation of the compression system. In this second stage operation, the refrigerant from the zone S is admitted at interstage pressure into the compression chamber C and is discharged therefrom into the condenser 2 at a discharge pressure of say, 180 pounds per square inch absolute. The second stage operation is continued until the pressure within the zone S is reduced again to the aforesaid minimum interstage pressure, whereupon the pressure responsive means M operates to reinitiate rst stage operation thus starting another cycle in the twostage function of the compression system.

As shown in the drawings, the chamber C is dened by a cylinder 4 in which a piston 5 is mounted for reciprocatory motion through operation of a suitable motor 5 (Fig. 2), and the zone S is defined by a housing 1 which, as shown in Fig. 2, may be the motor-compressor housing. Also as shown in the drawings, the pressure responsive means M preferably takes the form of a multiple valve `mechanism comprising a valve casing 8 and a pair of 'spaced interconnected valve members 9 and I0, respectively, mounted for axial movement within and longitudinally of said valve casing. Formed within the walls of the valve casing 8 and adapted to accommodate the valve members 9 and I0, are relatively spaced co-axial recesses II and I2 each having oppositely disposed valve seats I3 and I4. In mounting the valve members 9 and I 8 in the manner stated, three distinct non-communicating spaces I5, I6 and I1 are provided within the valve casing 8.

The respective valve members are adapted to seat selectively on the valve seats I3 or I4, and it is to be noted that the said members seat simultaneously on their respective valve seats I3, and simultaneously also on their respective valve seats I4. For that purpose, there is provided a relatively heavy compression spring I8 which normally acts on the valve member 9 to urge the same into engagement with the seat I3. In the present instance the valve members 9 and I0 are rigidly connected by a rod I9 so that they move together as a unit between the respective seats.

With reference to the drawings, it is"pointed out that when the valve members 9 and I0 are seated on their respective seats I3, that is, in the position shown in full lines, the system will function for first-stage operation. In this position of the valve members, a casing port 2 I, connected with a conduit 22 leading from 4the refrigerant evaporator I, is in communication with a port 23 which is connected through a conduit 24 with the valved intake port 24a of compression chamber C; and a casing port 25 connected with a conduit 26 leading from the valved exhaust port 26a of said chamber C is in communication with a port 21 which is connected through a conduit 28 with the hermetically sealed zone S. Referring again to the drawings, it will be noted that when the valve members 9 and I0 are seated on their respective seats I4, that is, in the position shown in dotted lines, the system will function for second stage operation. In this latter position of the valve members, port 23 is in communication with port 21, and port 25 communicates with a port 29 which is connected through a conduit 30 with the refrigerant condenser 2.

Since the system is a closed circuit'controlled by the valve means M, it will be appreciated that a pressure differential may be maintained at all times on opposite sides of the valve members 9 and I9, and in accordance with the invention, the system has three distinct pressure sides, that is, a low pressure side P1, an intermediate pressure side Pz, and a high pressure side P3. During rst 4 stage operation of the system, the low pressure side P1 extends from the restrictor 3 through the evaporator I, conduit 22, and port 2I intovalve space I5, thence through port 23 and conduit 24 into the compression chamber C up to the exhaust valve 28a thereof; the intermediate pressure side P2 extends from said exhaust valve through conduit 26 and port 25 into the valve space I6, thence through port 21, conduit 28 and into the hermetically sealed zone S; and the high pressure side P3 extends from the valve space I1 through port 29, conduit 30, condenser 2 and conduit 32 up to the restrictor 3.

During second-stage operation of the system,

when the valve members 9 and I0 occupy the alternative positions establishing communication between ports 23 and 21 and between ports 25 and 29, then the conduit 24 and compression chamber C up to its exhaust valve 26a become parts of the intermediate pressure side, while conduit 26 between said exhaust valve 26a and port 25 becomes a part of the high pressure side.

It will be understood, therefore, that the forces exerted in one direction `on the valve members 9 and I0, must be sulcient to overcome the pressure forces exerted on said members in the other direction while the system functions in first-stage operation to build up the pressure in the intermediate pressure side Pz to the predetermined maximum interstage value, and that this pressure differential upon the valve unit must be reversed in order to initiate and maintain secondstage operation, and again reversed when the intermediate pressure has dropped to the minimum in order to reinitiate the iirst-stage operation.

To summarize the operation of the system as far as described, let it be assumed that the condition is such that the interstage pressure within the zone S and therefore in the valve space I6, has been reduced to its minimum value, say, 50 pounds per square inch absolute, and that the force of spring I8 together with the force of the fluid pressure within the valve space I5 are suilicient to move the valve unit to first-stage position, that is, to the position shown in full lines in the drawings. 'I'he iiow of refrigerant is then, a`s indicated by the solid arrows in Fig. 1, that is low pressure gaseous refrigerant, admitted into the compression chamber C through conduit 22, port 2l, valve space I5', port 23 and conduit 24, and is discharged at increased pressure into the hermetically sealed zone S through conduit 26, port 25, valve space I5, port 21 and conduit 28. Continued pumping of the refrigerant causes the pressure in the zone S to gradually increase until the' interstage pressure in said zone, and therefore in the valve space i6, reaches its predetermined maximum value, at which point the force exerted by the uid pressures acting on the relatively large piston 9 is suicient to overcome the combined forces of the spring I8 and the uid pressures on the relatively small Valve member I0, thus causing the valve unit to move to its second-stage position, that is, the position shown in dotted lines in the drawings. The flow of the refrigerant is then, as indicated by the broken arrows in Fig. 1, that is, gaseous refrigerant at interstage pressure, permitted to flow into the compression chamber C through conduit 28, port 21, valve space I 6, port 23 and conduit 24, and is discharged at elevated pressure into the condenser through conduit 26, port 25, valve space I1, port 29 and conduit 30. The high pressure gaseous refrigerant gives up its heat in the condenser and condenses therein to return, as liquid,

amano to the evaporator. 'Ihis second-stage operation of the system continues until the lnterstage pressure within the zone S and valve space I6 is reduced to the predetermined minimum value, whereupon the opposing pressures on the valve members 9 and Ill become unbalanced in a direction causing the valve unit to return to the initial position and to thereby initiate another rststage operation.

In order to minimize the force effect on the valve member IIJ, the area of the valve member 9 should be considerably larger than the area of said member Ill. Moreover, it is to be understood that the spring rate of spring I8 should have a low value, so that the changes in its length, which occur with movements of the valve members 9 and I0 from one seated position to an'- other, does not materially affect the force exerted by said spring on said members.

In order to assure proper seating of the valve members 9 and I0 and also to preclude unseating of the members during the periods when the interstage pressure is in process of change between the aforesaid limits, suitable detent means, such as shown at 34, may be provided to engage the edge portions of the valve member 9, said detent holding the valve unit against movement until such time as one or other of said limits is reached and the pressure conditions are then such as to effect a shifting of the valve unit from one to the other of its alternative seated positions. The movement of the valve unit from one of said positions to another will occur almost instantaneously.

Provision is made also for balancing the weight of gaseous refrigerant handled by the compressor during the first and second stage operations, thus equalizing the number of strokes required for and the amount of work performed in said stages. In the embodiment shown in the -drawings, this is accomplished by providing a port 35 extending through the side wall of the compressor cylinder 4 to establish communication between the compressor chamber C and the hermetically sealed zone S, the connection including a casing 36, a tube 31, and a valve 38 which controls passage of gaseous refrigerant through-- the port as hereinafter described.

During first-stage operation, when gaseous refrigerant at suction pressure, say, pounds per pression chamber C by movement of the piston 5 through its intake stroke D (Fig. 1), the valve 33 still remains closed because then the pressure on: both sides of this valve is equal. However, the"- valve 38 opens as the compression stroke begins' due tothe increased pressure in said chamber so that gaseous refrigerant is bled back into the. zone S during movement of the piston through the initial part D1 of the discharge stroke. Movement of the piston over the part, D2, of the discharge stroke which remains after the port is covered, effects the normal second-stage compression. By locating the po'rt 35 so that a given part of the more highly compressed gaseous re frigerant in second-stage operation is bled awayas described above, theweight-o! the refrigerant handled during the two stages may be substantially balanced and, therefore, the work done per stroke and the number of strokes required for each stage substantially equalized.v

With reference to Fig. 2, which illustrates the adaptation of the compression system to a wellknown type of hermetic motor-compressor unit, the tube 31 preferably opens into the zone S at a point above the oil level 39 so that direct communication is established between said zone and the casing 38 which encloses the valve 38.

Also, as shown in Fig. 2, an intercooler 40 of known structure may be included in the system to cool the gaseous refrigerant as it is pumped into or out of the zone S. In this manner, it is possible to remove the heat of first-stage compression'thereby increasing the efficiency of the system.

Moreover, as illustrated in Fig. 2, the system may, and preferably does, include an overload -cutoff arrangement generally indicated at 4| which functions to prevent the imposition of excessive load on the motor, particularly during pull down periods, that is, during those periods when the evaporator I is working at abnormally high temperatures such as is the case, for instance, during defrosting cycles. The overload cut-off arrangement. 4I preferably comprises a valve 42 mounted in the suction conduit 22 to control the flow of refrigerant therethrough. This valve 42 may be automatically actuated in response to variations in pressure within the system. For that purpose a bellows 43, see Fig. 2, is connected, through the conduit 28 in the present instance, with that portion of the system included in the intermediate pressure side P2. In practice the bellows 43 is adjusted, by means for example of a suitable. regulating device 44, so as to be actuated if and when the pressure in the intermediatepressure side P2 rises above normal operating pressure, say to 60 pounds per square inch absolute. Connected with the bellows 43 to be operated thereby is a switch 45 adapted to open and close on electrical circuit 46 in which is included a solenoid 41 operatively connected to the actuating member 48 of the valve 42. When, therefore, the pressure in the intermediate pressure side of the system rises abnormally, as would occur during a pull down period, when the bellows 43 will expand moving the switch 45 into `position for closing the circuit 46 and energizing the solenoid 41 to close the valve 42; 'as soon as normal operating pressure is re-established in the system, the bellows will collapse moving the switch 45 into position for opening the circuit 46 to desolenoid 41 and to thereby open the functions to control the pressure responsive' means M in such manner that the interstage' 1f pressure, during pull down or high temperature periods, never exceeds a predetermined top value, say, pounds per square inch absolute.4

It will be apparent that the'invention makespossible eiiicient multi-stage compression by means of a single piston and cylinder assembly,"

and that such multi-stage compression may be obtained by means of a known conventional type' of motor compressor unit designed and heretofore use'd solely for single compression operation.l

*It will be understood that the invention is not# herein shown and described, and that such embodiments are subject to modification within the scope of the appended claims.

I claim:

l. In refrigeration, the method which comprises subjecting low pressure gaseous refrigerant to a first-stage compression in a compression chamber to bring such refrigerant to an elevated interstage pressure, collecting the gaseous refrigerant at said interstage pressure in an hermetically sealed zone, subsequently returning the gaseous refrigerant at the elevated pressure from said zone to the compression chamber for a second-stage compression therein to a relatively high discharge pressure, and bleeding a portion of said refrigerant from the compression chamber so as to reduce the quantity of gas subjected to the second-stage compression.

2. In refrigeration, the method which comprises compressing low pressuregaseous refrigerant in a compression chamber to an elevated interstage pressure, discharging the compressed gaseous refrigerant into a hermetically sealed zone, subsequently returning the compressed gaseous refrigerant from said zone to said chamber, compressing such refrigerant to a discharge pressure in excess of the said interstage pressure, and diverting a portion of -the refrigerant from the compression chamber to said zone so as to reduce the `quantity of the gas subjected to the second compression.

3. In refrigeration, the method which comprises admitting gaseous refrigerant at suction pressure to a compression chamber, compressing the refrigerant in said chamber to interstage pressure and discharging the compressed gaseous refrigerant into an hermetically sealed zone, thereafter returning compressed gaseous refrigerant from said zone to said chamber and compressing such refrigerant to discharge pressure in excess of the said interstage pressure, and bleeding a portion of said refrigerant from the compression chamberso as to reduce the quantity of the refrigerant subjected to the last-mentioned compression.

4. -In the operation of a refrigerating system including an evaporator, a condenser, a compressor of the type having a single compression chamber, and conduit means interconnecting said evaporator, condenser and compressor for ow of refrigerant therethrough, the method which comprises first, initiating a iiow of expanded gaseous refrigerant at suction. pressure from said evaporator to the compressor andA into the compression chamber thereof, compressing such gaseous refrigerant in said chamber to an interstage pressure and collecting the compressed gaseous refrigerant in an hermetically sealed zone until the pressure therein reaches a predetermined maximum value, then interrupting the flow of the gaseous refrigerant from the evaporator to the compressor and initiating a return flow of the compressed gaseous refrigerant from said zone to said compressor and into the compression chamber thereof, further compressing the gaseous refrigerant in said chamber to a relatively high discharge pressure and discharging gaseous refrigerant at such discharge pressure into the condenser to be liquefiedtherein for circulation as liquid from the condenser to the evaporator.

5. In the operation of a refrigerating system including an evaporator, a condenser, a compressor of the type having a single compression chamber, and conduit means interconnecting said evaporator, condenser and compressor for now of refrigeranttherethrough, the method which comprises first, initiating a flow of expanded gaseous refrigerant at suction pressure from said evaporator to the compressor and into the compression chamber thereof, compressing such gaseous refrigerant in said chamber to an interstage pressure and collecting the compressed gaseous refrigerant in an hermetically sealed zone, then interrupting the ow of the gaseous refrigerant from the evaporator to the compressor and initiating a return flow of the compressed gaseous refrigerant from said zone to said compressor and into the compression chamber thereof, bleeding a portion of such gaseous refrigerant from said chamber and back into said zone, compressing the remaining portion of such gaseous refrigerant in the chamber to a relatively high discharge pressure and discharging gaseous refrigerant at such discharge pressure into the condenser to be liquefied therein for circulation as liquid from the condenser to the evaporator.

6.- In the operation of a refrigeration system including an evaporator, a condenser, a motor compressor unit of the type having a hermetically sealed housing enclosing said unit, and conduit means interconnecting said evaporator, condenser, and motor compressor unit for the fiow of refrigerant therethrough, the method which comprises rst, initiating a flow of expanded gaseous refrigerant at suction pressure from said evaporator to the compressor, compressing such gaseous refrigerant in said compressor to an interstage pressure, and discharging the compressed gaseous refrigerant into the motor compressor housing until the pressure therein reaches a predetermined maximum value, then interrupting the now of gaseous refrigerant from the evaporator to the compressor and initiating a return flow of the compressed gaseous refrigerant from said housing to the compressor, further compressing such gaseous refrigerant in the compressor to a relatively high discharge -pressure and discharging the refrigerant at such discharge pressure into the condenser to be liquefied theref in for circulation as liquid from the condenser to the evaporator, re-establishing the ow of low pressure gaseous refrigerant from the evaporator to the compressor when the pressure in said housing reaches a predetermined minimum value, and repeating the steps as specified.

7. In a refrigerant system, a compressor, a hermetically sealed zone, means for circulating refrigerant between said compressor and zone, said circulating means including a first conduit for admitting refrigerant to said compressor, a second conduit for discharging refrigerant from said compressor, a third conduit for both admitting refrigerant to and discharging refrigerant from said zone, a valve casing in communication with said three conduits, and valve means in said casing responsive to pressure variations in the system for establishing communication between said third conduit and the said first and second con-.

duits selectively.

sion chamber provided with an intake port and exhaust port, means for admitting expanded refrigerant at suction pressure into said chamberA through the intake port thereof, an hermetically sealed zone maintained at an interstage pressure in excess of said suction pressure, conduit,

means connecting said zone with said ports, a

pressure responsive device associated with said said zone, and means for condensing refrigerant compressed to a discharge pressure in excess of said interstage values, said pressure responsive device including a valve structure constantly exposed to the pressure Within said zone and operative when the interstage pressure in said zone is reduced to the predetermined minimum value to establish communication between the expanded refrigerant admitting means and the compression chamber intake port and between the compression chamber exhaust port and the hermetically sealed zone, thereby vinitiating the first stage compression operation, and when the interstage pressure in said zone is increased .to the predetermined maximum value, to interrupt communication between the expanded refrigerant admitting means and the compression chamber intake port and to establish communication between said intake port and the hermetically sealed zone and also between said compression chamber exlaust port and the refrigerant condensing means, thereby initiating the secondstage compression operation.

9. In a closed refrigerant comprising a refrigerant compressor having a single compression chamber provided with an intake port and an exhaust port, means for admitting expanded refrigerant at suction pressure into said chamber through the intake port thereof, a hermetically in excess of said suction pressure, conduit means connecting said zone with said ports, a pressure responsive device associated with said conduit means and operable to initiate the rst and second stage compression operations of the system in accordance with predetermined minimum and maximum interstage pressure values in said zone, and means for condensing refrigerant compressed to a discharge pressure in excess of said interstage pressure, said pressure responsive device including a valve structure constantly exposed to the pressure within said zone and operative when the interstage pressure in said zone is reduced to the predetermined minimum value to establish communication between the expanded refrigerant admitting means and the compression chamber intake port and between the compression chamber exhaust port' and thehermetically sealed zone, thereby initiating the rst stage compression operation, and when the interstage pressure in said zone is increased to the predetermined maximum value to interrupt `communication between the expanded refrigerant admitting means and the compression chamber intake port and to establish communication between said intake port and-hermetically sealed zone and between said compression chamber exhaust port and the refrigerant condensing means, thereby initiating the .second-stage compression operation. and means for bleeding a portion of the refrigerant from said chamber to said zone during the second stage compressing operation.

10. In a multi-stage refrigerant compressing` system utilizing a motor-compressor unit of the type having a hermetically sealed housing enclosing said unit. means for circulating refrigerant between said compressor and the interior of said housing, said circulating means including a rst conduit for admitting refrigerant to the compressor. a second conduit (or discharging rc- Numberv -an abnormally high value. ELMER.

l0 frigerant from the compressor, a third conduit for both admitting refrigerant to vand discharging refrigerant from the housing, a valve casing in communication with said three conduits, and a valve in said casing responsive to pressure variations in the system for establishing communication between said third conduit and one of said first and second conduits selectively while interrupting communication between said third conduit and the other of said iirstr and second conduits.

11. In a refrigerating apparatus including an evaporator and a condenser, a two-stage refrigerant compressing system comprising a compressor of the type having a single compression chamber provided with a valved intake port and a valved exhaust port, an hermetically sealed zone, conduit means interconnecting said evaporator, condenser, compressor and zone to provide a closed circuit for the circulation of refrigerant, an interposed device including valve means movable selectively into two positions in response to pressure variations in the system, said valve means being operative in one position to establish communication between the evaporator and the intake port of the compression chamber and between the exhaust port of said chamber and the hermetically sealed zone, and in the other position to establish communication between said zone and the intake port of said compression chamber and between the exhaust port and the condenser.

12. In a refrigerating apparatus including an evaporator and a condenser, a two-stage refrigsealed zone maintained at an interstage pressure I.' erant compressing system comprising a com" device operable to initiate rst and second stage operations in the system, said device including valve means movable selectively into two positions in response to pressure variations in the system, said valve means being operative in one of said positions to establish communication between the evaporator and the intake port of the compression chamber and between the exhaust port of said chamber and the hermetically sealed zone, thereby initiating ilrst stage operation, and in the other of said positions to establish communication between said zone and the intake port of said compression chamber and between the exhaust port and the condenser,- thereby initiating second-stage operation, means for bleeding a portion of the refrigerant from said chamber back to said zone during the second-stage compressing operation, and pressure actuated means included in said conduit means for interrupting flow of refrigerant from the evaporator to the condenser when pressure in the system attains W. ZEARFOSS, JR.

REFERENCES CITED The vfollowing references are o! record in the ille of this patent:

UNITED s'rs'rns PATENTS Name Date Wyldv -v...- Dea-17, 1935 Eaton May 22, 1945 Eaton Oct. 2, 1945 Eaton .v-; Oct. 2, 1945 Fowler Oct. 2, 1945

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