US2123123A

US2123123A - Refrigerating system capacity control

Info

Publication number: US2123123A
Application number: US120982A
Authority: US
Inventors: Norman M Small; Jr Leon Buehler
Original assignee: Frick Co Inc
Current assignee: Frick Co Inc
Priority date: 1937-01-16
Filing date: 1937-01-16
Publication date: 1938-07-05
Anticipated expiration: 1955-07-05

Description

July 5, 1938, v N. M. SMALL ET AL REFRIGERATING SYSTEM CAPACITY CONTROL 2 Sheets-Sheet 1 Filed Jan. 16, 1937 N. M. SMALL ET AL REFRIGERATING SYSTEM CAPACITY CONTROL Jul 5, 1938.

Filed Jan. 16, 1937 2 Sheets-Sheet 2 Patented July 5, 1938 anrarcnnarmo srs'rmu cArAorry common Norman M. Small and Leon Bnehler, In, Waynesboro, Pa., assignors to Frlck Company, Waynesboro' Pa., a corporationmf Pennsylvania Application January 16, 1931, Serial No. 126,982 22 cam (01. 62-415) This invention relates to. refrigerating systems and more particularly to'capaclty control means for refrigerating compressors which are auto-' p 'matically operable in accordance with conditions f in the refrigerating system.

In-refrigerating plants it is common practice to provide a plurality of, compressors wherein one or more of the compressors'can be shut down during cool or cold seasons and thus reduce the refrigerating capacity of the compression'side'of the plant. However, owners frequently desire to have all the-compressor'capacity in a single 'unit with means for varying the volumetric dis- I placement, and-the present invention relates to this type of installation. a

Capacity control'uslng themethod of reducing the effective stroke of the compressor by by-pasin ing partof the gas in the cylinder between the piston and discharge valves to .the suction side of the compressor is old inthe art and is no claimed as a part of this invention. a

The present invention relates particularly to capacity control for refrigerating compressors although it may be used to equal advantage for air 7 compressors, gas compressors and other types of fluid compressors.

1 a An object of the invention is to provide means whereby the volumetric displacement of a coml pressor can be controlled either by hand or by automatic means.

Another object of the invention is to provide improved means for varying. the volumetric displacement of a compressor.v said means being automatically controlled by highly sensitive tern-'- perature responsge means. I

A further object of the invention is to provide in a refrigerating system means for operating compressor capacity control means in accordance 40 with the true saturated temperature of refrigerant in the low side of the systemwhich correther means of controlling the capacity-of the compressor during its operation.

A further obiect of the inventionis toprovide a varying capacity compressor controlled by tem- -iperatur'eresponsive means in ,accordance with the load requirements of the system andin conjunction with capacity control means for varying the compression within predetermined limits. Another object of the invention is to provide in a refrigerating system a capacity control means which operates on the compressor to change from full capacityto partial capacity in accordanceiwith load requirements of the sys-' tem, thecompressor at no time being completely unloadedwhile operating.

Other objects, details and advantages of our in- 10 vention willbe apparent from the following description of the embodiments thereof shown in.

the accompanying drawings, wherein:

Figure l is a pers tive view of a refrigerating system showing a ompressor provided with capacity control means automatically operated by fluidpressure in accordance with this invention.

Figure 2 is a vertical sectional view through a compressor cylinder and one-of the capacity control ports in connection with fluid pressure operating mechanism. v

Figure 3 is a sectional view of a spring mounting for operating the capacity control valve during inoperativeness of the pressure control means.

Figure 4 is a sectional view of a modified form of the fluid pressure operating mechanism for the capacity control ports.

Figure 5 is a fragmentary. perspective view showing a modified form of the fluid pressure 30 return means.

Figure 6 is a detailed view of the pressure oper-. ative return means shown in Figure 5. t

Figure 7 is a fragmentary sectional view showing a modification of part of the pressure opera- 5 tive return means shown in Figure 6.

Referring to the drawings this invention is shown by way of examplein Figure 1 applied to a two cylinder compressor I 0 driven by motor Illa.

However, the invention is applicable to a single 4o is. provided with a crankcase ll, anda suction, conduit l2. communicates with the compressor intake chamber It. The compressor is provided 46 with the usual discharge valves located in' the valve head in the'cylinder head as shown in 'Figure 2 and compressed gases} are conducted through a discharge line l5 leading to a-con-- denser and receiver l8, From:the receiver re-so frigerant fluid is conducted through a hand eontrol valve Ilia and conduit" to an evaporator it which may be a cooler of any desired type. an expansion valve "a. controlling the discharge of liquldrefrigerant th ereinto. The gaseous refrlgv erant is then returned from the evaporator to the compressor through the suction conduit l2.

As shown in Figure 2 each cylinder is provided with'a chamber l9 extending upwardly from .the intake chamber l3 towards the head of the compressor and the intake chamber I3 is shown provided with an inlet port 20 communicating with the interior of the compressor cylinder 2| beneath the piston 22'therein; this piston is provided with the suitable types of sealing rings and valves as indicated. In order'to vary the compressor capacity a port 23 communicating through the wall of the cylinder 2| with chamber i9 is positioned to provide the required capacity reduction of the compressor. This port provides communication with the cylinder 2| above piston 22 with the chamber l9 so as to permit gas to flow from the cylinder therethrough into the suction chamber l3 and through the suction port 26 during a portion of the upward stroke of the piston. As

indicated, piston 22 has moved upwardly to the 7 upper edge of port 23 to close the communication with chamber l9 and on further upward movement it operates to compress the remaining gas in the compressor cylinder 2|.

The distance the edge of the port23 is located from the head of the compressor depends upon the amount of capacity reduction desired, for example, in Figure 2it is'located at flfty percent of the stroke of the piston which gives approximately fifty percent capacity reduction. If a-greater capacity reduction is desired the upper edge of port 23 must be closer to the head of the compressor. and for a less capacity reduction the port must be lower in thecylinder; The position of the port in accordance with the required capacity reduction is preferably determined and fixed at the time the compressor is constructed.

As shown in Figure, 3 a valve cage 24 is mounted in flanges 25 formed in chamber 19 and it extends through an aperture in the exterior wall thereof. The inner end of cage 24 seats on a gas tight gasket 26 between it andthe compressor cylinder wall. Qage 24 is provided with'a port 21 communicating with port 23 into the interior of the cylinder and ports 23 communicating with chamber l9 which ports provide passageways through which gas may be permitted to flow as stated above. This cage 24 acts as a guide for a valve 23 slidingly mounted therein and which is operable to close the passageway into the compressor cylinder, thus causing the compressor to operate under full capacity.

As shown valve 26 is held in open position by a plunger 30 connected to the valve by the pin 28a.

and extending from a differentially pressure actu- ,is provided with manual operating hand wheel 31.

Hand wheelstem 36 is provided with threads 36 engaging corresponding threads 36 in a cylinder closing head 40, andthe outer end of head 46 is provided with a packing member 4|. It will be noted that whe hand wheel 31 is turned to disengage the head 36 from piston 3| and is moved outwardly therefrom the rear of the head 3' which has a seatingsurface makes contact with a complementary seat 42 formed in head 46 making a gas tight joint therewith whereby the packing element 4| may be inserted or removed.

When h'and wheel stem 36 is turned to disengage the head from piston 3| and the pressure operating means is released the spring members 30a positioned between the piston 3| and end wall 32 hold the valve open and displace the fluid when the pressure supply is discontinued. Preferably these springs are placed in a recess 3017 at angles of. 120 about the plunger 30 to obtain a more "even distribution of force in opening the valve 29.

Referring to Fig. 4 an operating cylinder casing 32', of the same construction as shown in Fig. 3, is shown with a modified form of a differentially pressure actuated piston 3| and other slight changes; with the exception of these modifications, the parts are the same as those illustrated in Figure 3 but the stem 36 is shown in its outer position with the head 35 seated in the seating surface in head are previously described. In this structure piston 3|- is provided with a piston packing 3|b, in the form 01 a molded cup packing instead of piston rings 3|a such as provided for piston 3|: This cup packing. is secured to piston by means oi a cup retainer 3|c. This in turn is held in place by a nut 3|d on the end of plunger 30 extending through piston 3| which also maintains piston elements assembled on this plunger. The casing 32' is also provided with a closure seal 30' surrounding plunger 36 which seal as shown includes a flexible packing ring and a retainer ring cooperating therewith and may be secured to the end wall of casing 32' by means of screws or the like shown in Figure 2. The spring members 30a inindentatiohs or recesses 30b as shown in Figures 2 and 3, positioned by pistonll against wall end 32' of fluid chamber 32, are not included in this view as the compression pressure may serve tohold the valve in open position, though preferably the spring members are to be used.

It will be noted in the foregoing valve equipment, which is a preferred construction although other forms can be employed for the purpose of this invention, that with the hand control moved to the extreme inward position from that shown in Figures 2 and 3 the valve 29 closes port '23 for the full volumetric capacity of the compressor, but when the hand wheel is inthe position shown in Figures 2 and 3,the valve 29 will be forced to an open position by the comvpression'inthe cylinder and the springs 30a com-'- pressed-by piston 3| in its cylinder casing 32, the springs 36a maintaining the valve open during inoperation of either the compressing fluid or the hand valve. Cylinder 32 is also provided with afluid return conduit 44 as shown in Fi ure 1 and Figure 5 to conduct the seepage 0F pressure'fluidto the source of fluid supply which in this case is the compressor, crank case, although" any suitable source of fluid supply may be employed other than the crank case if desired. The fluid conduits 43 01 the cylinders 32 are interconnected and coupled with a fluid pump 46 which has a supply conduit 46' leading to it from the source of fluid supply,--as shown the crank case M of the compressor.

Fluid pump "is shown operatively connected by means of a coupling 41 with an electric motor 43 and the compressor I0 is shown operatively connected with an electric motor Illa, which motors Illa and 43 receive their operating current from a suitable source of electric power supply indicated by electrical conductors 43 having a positive cut-out switch 49a and the thermostatically actuated switch 50 in the circuit for controlling thecurrent flow.

The switch 491: is placed in the power supply line to render the switch 50 inoperative when no power supply to the electric motors is desired. In the power supply line between the switch control 59 and fluid motor 48 is placed the switch 48a which may be used to cut out the power supplied to the fluid motor when the com- 7 pressor is desired to be operated at full capacity by mechanical closure of the outlet ports in the cylinder wall, or if the compressor is to be operated at a capacity less than full, by allowing the port to remain open and the closure means inoperative. While the switch 49a and 48a are manually operable any substitution of an automatic or mechanically actuated switch means could obviously be used for cutting in or out the power supply.

Switch 50 controlling the operation of the motors 48 and l Ila is actuated by a bellows which perature of the refrigerant in the suction line.

The bellows 5| actuates the switch arm 50a on which are contact points 5llband 50c properly insulated from one another and adapted to have sliding engagement with the contact points 50d and 500 for controlling the electric motors illa and 48 respectively. The operation of the electric motors is in accordance with the load requirements of the system and the switch contact is arranged to operate the motors in accordance with the required conditions of the system.

When a system is required to operate at full capacity bellows 5| is expanded to engage the contacts 591) and 500 with 50d and We respectively, the contact 50d controlling the compressor motor Illa, the contact 50c controlling the fluid motor 48. I When the compressor is adapted to be operated at a reduced capacity the bellows 5| is contracted to disengage the contact 500 from 50c controlling the fluid motor 48. The contact 50b remains in engagement with the contact 5011 controlling the operation. of motor Illa and allowing it to complete the compression desired at half capacity until at such time that when suflicient" refrigeration is produced the compressor motor control switch is disengaged to interrupt the current supply; If desired the control of the capacity and the operation of the compressor may be produced by individual thermostats situated.

of the refrigerant in the suction line, and in ac-'- cordance with the conditions required the piston 3| is operated to close port 23 by valve 29 withoutusing the hand control wheel 31, the hand control wheel being operated to its outermost position to allow piston 3| to reciprocate in its cylinder for the automatic operation thereof. Thus the automatic operation of the compressor will take place irrespective of atmospheric conditions such as temperature and humidity or pressure which normally have a decided effect on the compressor capacity, and the compressor will operate at full discharge capacity or at itsintermediate discharge capacity in accordance with the refrigerating requirements within the system and which may be determined by temperature or pressure. I

Accordingly in the operation of the control mechanism when the temperature drops below a predetermined point the switch opens and breaks the. current to motor 48 thereby stopping it. The fluid supply is consequently stopped and the fluid in the piston cylinder is released through conduits 43, returning directly back to its source of supply. This allows the springs 30a aided by the compressor to force valves 29 to open position and consequently unload the compressor to the predetermined degree (fifty percent or in accordance with the position of port 22 with respect to the compressor cylinder head) through the various ports back to the suction of the compressor. l l

A modified pressure relief connection particularly applicable when a fluid pressure pump is used which is inapt for return of fluid therethrough is shown in Figure 5 for the return of fluid through conduit 44 to its source by means vof valve 53 which is placed in the by-pass between the pressure supply source conduit and the relief conduit 44. Check valve 53 is closed by fluid pressure in the conduit 43. This valve as'shown in Figure 6 comprises a casing which includes an inlet port 54 and outlet port 55 which ports are connected to

conduits

43 and 44 respectively. Inside the casing is a reciprocable valve member 55' having an elongated spirally grooved passageway 56 extending from its upper face to the lower portion thereof whereby fluid may escape from the inlet or high pressure side to the outlet or low pressure side when the pump is inoperative. This valve member has a plunger '51, the end of which seats in a valve seat 58 which the movable valve member- 55' is adapted to engage when forced upwardly by the spring 59. The position of the projection 6| inthe valve casing determines the upper limit of the'move- 'ment of valve member A check valve 53 with modifications isrshown in Figure 7. Due to inequalities of tension of spring 59, a compensating spring 59' is posi-' tioned above valve member 55' and in this arrangement the abutment member 60 with its projection are replaced by a head 68' threaded into the check valve casing in place of the member 68. This head carries a stem 50a having a threaded engagement therewith at 601) and a packing member 68c forms a fluid tight seal around stem Stern 60a. has an enlarged spring engaging member In on its inner-end for engaging spring 59' and its upper end is'formed for receiving an operating tool such as a kerf Bid for receiving the blade of a screw driver. By turning stem 60a in or out' tension on spring 59' may be varied and by such adjustment compensation. for inequalities of spring 59 is provided.

When the temperature rises switch 58 is automatically closed, starting motor 48 so that pump correspond toithe ba '45 is operated to start the circulation of fluid through conduit 43 to the cylinders of piston 3|. This puts pressure through the branch conduits 43 leading to the piston chambers for each compressor cylinder and against the pistons 3| which are forced inwardly compressing the springs 30a and closing the ports 23 by engagement of the valves 28 therewith, the compressor then operates at full capacity. When the check valve 53 connection is used valve member 55" is closed against the spring 59 by the fluid pressure on account of the resistance of the fluid passing through the valve. This inturn puts pressure through the branch conduits 43 leading to the piston chambers for operation of the valves as heretofore described.

Referring again to .the thermal element 52 I which cooperates with suction line I! of the compressor, it will be noted that this element is port in the cylinder wall and a valve for closing said port, a pressure actuated piston for operating said valve, temperature responsive means for operating said valve and piston to close the port and to permit the valve to open, manual control means for closing said valve, and spring means for opening said valve during inoperation of the closing means.

3. In a refrigerating system, a compressor includinga compression cylinder and piston therein, capacity control means including a housing for controlling the volumetric displacement, of the compressor for varying the refrigerating capacity of the system comprising a. port in the cylinder wall and a valve biased into open position for closing said port, manual control means for closing said valve including a stem movable inwardly to and outwardly from its val've closing position, a head on the end of said stem having a valve seat on one side, a packer in said housing through which said stem operates, and said housing having a cooperating valve seat adapted to connecting pipe into chamber 52 around thermal element 52.

It will be noted that with valve 0i fluid re-.

frigerant is discharged and expanded into this chamber surrounding the thermal bulb. This is for the purpose of giving a saturated temperature around the bulb regardless what the superheat temperature may be in the suction line itself. Accordingly, a true saturated temperature corresponding to the back pressure is obtained because the temperature of the gas expanded must pressure in the suction line, and this true saturated temperature is obbe engaged by said stem head valve seat and forming a seal therewith when the stem is in its outermost position.

-4. In a refrigerating system, a compressor including a compression cylinder and piston therein, capacity control means controlling the volumetric displacement of the compressor for varying the refrigerating capacity of the system com- 30 prising a port in the cylinder wall and a valve for closing said port, a ported cylinder in which said valve is slidingly mounted, a piston reciprocably mounted-behind said valve and havin means interconnecting it and said valve to operate the latter to its open or closed position, a

source of fluid supply, a pump for supplying said fluid behind said piston for closing said valve,

tained because the gas so expanded does not mix with the superheated gas until it passes down to the suction line However when valve is closed the capacity control of the refrigerating system will operate in accordance with the temperature of the gas in the suction line from the evaporator instead of the saturated gas temperature. Thus the system may be operated under either condition by operating with valve opened or closed as desired.

This application is a continuation inpart of our copending application now Patent No. 2,112,

It will be obvious to those skilled in the art that various changes may be made inmy device without departing from the spirit of the invention and therefore we do not limit ourselves to what is shown in the drawingsand described in the specification but only pended claims.

We claim: 1. A refrigerating system including a compressor, an evaporator and suction line for returning refrigerant from the evaporator to the compressor and capacity control means for controlling the elective volumetric displacement of the compressor for varying the effective refrigerating capacity of the system, and means for controlling said capacity control means and for controlling said system in accordance with-refrigerant temperature on the low side of the system.

2. In a refrigerating system, a compressor including a compression cylinder and piston therein, capacity control means for varying the reiri'gerating capacity of the system, comprising a as indicated in the ap-.

a conductor for returning fluid therefrom to said source of supply, and a check valve therein operable to return the fluid-therethrough to the source of fluid supply when said pump is inoperative.

5. In a refrigerating. system, a compressor, capacity control means for varying therefrlger! ating capacity of the compressor, a fluid supply source,.means for placing the fluid under pressure for operating said capaclty'control means to cause the refrigerating system to operate at full capacity, manually operable electrical means for controliing the effectiveness of said capacity control means independently of'the system operation, a conductor for returning fluid therefrom to saidsource of supply, and a check valve therein operable to return the fluid therethrough to the fluid supply source when said fluid pressure means is inoperative.

6. In a refrigerating system, including a compressor with fluid pressure operated capacity consaid casing, a spring under said valve member,

, through comprising a valve basing having a cylintrol means, asource of fluid supply and means for supplying fluid therefrom under pressure to said pressure operated control means, a conductor forv returning fluid from said control means to said source of supply, and a check valve therein for unloading the operating fluid there- 65 drical interior and inlet and outlet ports at opposite ends thereof, a valve member therein operable to close the communication with the outlet port, said valve including a piston portion slidable in tending to'move it from its closing position, and said piston portion having a restricted spiral passageway therethrough permitting the passage of fluid when the pressure of the fluid is reduced.

7. .In a refrigerating system. including a comsaid last named means but constructed and arpressor with fluid pressure operated capacity control'means, a source of fluid supply and means for supplying fluid therefrom under pressure to ends thereof, a valve member therein operable to close the communication with the outlet port, said valve including a piston portion slidable in said casing, a spring under said valve member tending to move it from its closing position, a spring over said valve tending to move in the reverse direction, means for adjusting the tension of the last said spring, and said piston portion having a restricted passageway therethrough permitting the passage of fluid therethrough when the pressure of the fluid is reduced.

8. In a compressor condenser evaporator system an unloading mechanism for the compressor, temperature responsive means controlling said unloader and for controlling said system, said temperature responsive means being constructed andarrang'ed for actuation in accordance with the temperature corresponding to the pressure within the said evaporator.

9. In a refrigerating system a compressor, a condenser and an evaporator connected 'in a closed circuit and in the order named, an unloading device for said compressor, a control for said unloading device, a by-pass connected in the circuit parallel to andshort-circuiting the evap:

orator, a thermostat in functional relation to said by-pass for selectively actuating said control or the system;

10. A compression refrigeration system hav-, ing a variable capacity compressor, a motor for j in the said evaporator.

ing said element for stopping. and starting'said 12. In a compressor condenser evaporator system an unloading mechanism for the compressor,

means controlling said unloader including a temperature responsive element, said temperature responsive element being constructed and arranged for actuation in accordance with the tem?- perature corresponding to the pressure within said evaporator, and thermostatic means includsystem. 13.- In a refrigeration system having a compressor, condenser and evaporator, an unloading mechanism for the compressor, means controlling said unloader including a temperature responsive element, means remote from said evaporator but responsive to pressure conditions interiorly of 15 ment being located outside said evaporator in said evaporator, said temperature-responsive eleranged for actuation in accordance with the temperature corresponding to the pressure within the said evaporator, and thermostatic means including said temperature responsive element for stopping and starting said system and selectively rendering said unloader control effective or ineffective.

. 14. In a compressor condenser evaporator system an unloading mechanism for the compressor, temperature responsive means controlling said unloader, said temperature responsive means being constructed and arranged for actuation in accordance with the temperature corresponding tothe pressure within the said evaporator, and means for stopping and starting said system, said last named means being responsive to said temperature responsive means.

15. In a compressor condenser evaporator system an unloading mechanism for the compressor, temperature responsive means controlling said unloader, said temperature responsive means being located outside of said evaporator and constructed and arranged for actuation in accordance with the temperature corresponding to the pressure within the said evaporator, and means for stopping and starting said system, said last named means being responsive tosaid temperatureresponsive means.

16. In a refrigerating s'ystema compressor, a condenser and an evaporator connected. in a closed circuit and in the order named, an unloading device for said compressor, a control for said unloading device, a by-pass connected in the circuit parallel to: and short-circuiting the evaporator, a thermostat in functional relation to said by-pass for actuating said control, and thermostatic means for stopping and starting said system.

17. In a refrigerating system a compressor, a

condenser and an evaporator connected in a closed circuit and in the order named, an unloading device for said compressor, a control for said unloading device, aby-pass connected in the circuit'parallel to and short-circuiting the evap-- orator, a thermostat in functional relation to said by-pass for actuating saidcontrol, and. means for stopping and starting saidsystem, said last named means being responsive to said thermostat.

' 18. A compression refrigeration system having a variable capacity compressor, a motor for driving said compressor, means for controlling the capacity of the compressor including an unloader, means for stopping and starting operation of the system, and single thermostatic means for actuating both the compressor-capacity control and said last named means.

19. A compressor condenser evaporator system, an unloader for said compressor, manual means for operating said unloader, fluid pressure means for operating saidunloader, a circulating pump for causing an under pressure to operate said un loader, and means for controlling said circulat-' ing pump.

20. A compressor condenser evaporator system, an unloader for said compressor, manual means for operating said unloader, fluid pressure means for operating said unloader, a circulating pump for causing fluid under pressure to operate said unloader, and thermostatic means for controlling said circulating pump.

21. A compressor condenser evaporator system, an unloader for said compressor, manual means for operating said unloader, fluid pressure operating said unloaider, means for controlling said circulating pump; and thermosatic means for starting and stopping said system.

22. A compressor condenser evaporatorsys-' tem, an unloader for said compressor, manual means for operating said unloader, fluid pressure means" including a fluid circulating pump for .means including a'iluid circulating pump for operating said unloader, means for controlling said circulating pump? and single thermostatic means for starting and stopping said system and for controlling said circulating pump.

n- NORMAN M; SMALL.

LEON BUEHLER, JR.