US2112791A - Refrigerating system - Google Patents

Description

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R EFRIGERATING SYSTEM Filed March 28, 1936 2 Sheets-Sheet l March 29, 1938. N. M. SMALL ET AL REFRIGERATING SYSTEM 2 Sheets-Sheet 2 Filed March 28, 1956 gwvcntom Kw Aida/, an

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Gnome/1s Patented Mar. 29, 1938 PATENT OFFICE REFRIGERATING SYSTEM Norman M. Small and Leon Buehler, Jr., Waynesboro, Pa., assignors to Frick Company, Waynesboro, Pa., a corporation of Pennsylvania Application March 28, 1936; Serial No. 71,485

.15 Claims.

This invention relates to refrigerating systems and more particularly to capacity control means for refrigerating compressors which are automatically operable in accordance with conditions in the refrigerating system.

In refrigerating plants a plurality of compressors have been installed in which case one or more compressors can be shutdown during cool or cold seasons and thus reduce the refrigerating caof the compressor is old in the art and is not claimed as a part of this invention.

The present invention relates particularly to capacity control for refrigerating compressors although it may be used to equal advantage for air of fluid compressors.

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

Another object of the invention is to provide means for varying the volumetric displacement of a compressor automatically controlled by temperature responsive means.

Another object of the invention is to provide in a refrigerating system automatically operable means for operating compressor capacity control means in accordance with temperature of the refrigerant in the low side of the system.

A further object of the invention is to provide in a refrigerating system means for operating compressor capacity control means in accordance with the true saturated temperature of refrigerant in the low side of the system which corresponds to the back pressure of the expanded gas regardless of what the superheat temperature of the expanded gas in the low side of the system compressors, gas compressors, and other types fluid pressure in accordance with this .invention.

Fig. 2 is a sectional view of an automatic unloading valve for returning the capacity control means operating fluid back to the fluid supply source.

Fig. 3 is a vertical sectional view through a compressor cylinder and one of the capacity control ports in connection with fluid pressure operating mechanism.

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

Fig. 5 is a fragmentary sectional view showing a modification of part of the unloading valve shown in Fig. 2.

Referring to the drawings this invention is shown by way of example applied to a two cylinder compressor I0, however, the invention is applicable to a single cylinder compressor or of any number of cylinders. In the arrangement shown the compressor is provided with a crank case I I, and a suction conduit I2 communicates with the compressor intake chamber I3. The compressor is provided with the usual discharge valves located in the valve head I4 in the cylinder head as shown in Fig.3 and compressed gases are conducted through a discharge line I5 leading to a condenser and receiver I6. From the receiver refrigerant fluid is conducted through a hand control valve Mia and conduit II to an evaporator I8 which may be a cooler of any desired type, an expansion valve I8a controlling the discharge of liquid refrigerant thereinto. The gaseous refrigerant is then returned from the evaporator to the compressor through the suction conduit I2.

As shown in Fig. 3 each cylinder is provided with a chamber I9 extending upwardly from the intake chamber I3 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 they compressor. This port provides communication with the cylinder 2| above piston 22 with the chamber I9 so as to permit gas to flow from the cylinder therethfough into the suction chamber I3 and through the suction port 20 during a portion of the upward stroke of the piston. As indicated, piston 22 has moved upwardly to the upper edge of port 23 to close the communication in the compressor cylinder 2|.

The distance the edge of the port 23 is located from the head of the compressor depends upon the amount of capacity reduction desired,

' for example, in Fig. 3 it is located at fifty per by a nut 3|d on the end of plunger. 30 extending cent of the stroke of the piston which gives approximately fifty per cent 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 the cylinder. 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 Fig. 3 a valve cage 24 is mounted in flanges 25 formed in chamber I9 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 and the compressor cylinder wall. Cage 24 is provided with a port 21 communicating with port 23 into the interior of the cylinder and ports 28 communicating with chamber H) 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 29 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 29 is held closed by a' plunger 30 extending from a piston 3| which is slidingly mounted in an operating cylinder casing 32 which is secured by means of bolts 33 to the outer wall of chamber l9 with a gasket 34 of circular cross section between the end of the cylinder member 32 in the wall of the chamber. This gasket forms a gas tight seal and permits easier alignment of the cylinder with the valve cage chamber for the valve 29. Piston 3| may be held in the valve closing position as shown by the engagement of the head 35 on a stem 36 which is provided with a manual operating hand wheel 31.

Hand wheel stem 36 is provided with threads 38 engaging corresponding threads 39 in a cylinder closing head 40, and the outer end of head 40 is provided with a packing member 4|. It will be noted that when hand wheel 31 is turned to disengage the head 35 from piston 3| and is moved outwardly therefrom the rear of the head 35 which'has a seating surface makes contact with a complementary seat 42 formed in head 40 making a gastight joint therewith whereby the packing element 4| may be inserted or renewed.

Referring to Fig. 4 an operating cylinder casing 32', of the same construction as shown in Figure 3, is shown with a modified form of piston 3| and other slight changes; with the exception through piston 3|, which also maintains piston elements assembled on this plunger. The casing 32' is also provided with aclosure seal 30a surrounding plunger 39 which seal as shown includes a flexible packing ring and a retainer ring cooperating therewith and secured to the end wall of casing 32' by means of screws or the like.

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 in the position shown in Fig. 3 the Valve 29 closes port 23 for the full volumetric capacity of the compressor, but when the hand wheel is turned to disengage the stem head 35 from piston 3| valve 29 will be forced by the compression in the cylinder to an open position pushing with it piston 3| in its cylinder casing 32. Piston 3| is adapted to be operated by fluid pressure behind it entering cylinder 32 through a fluid conduit 43 communicating therewith. Cylinder 32 is also provided with fluid return conduit 44 communicating with the other side of the piston and as shown in Fig. 1, the fluid return conduits for each cylinder 32 are interconnected between the various cylinders and conduct the fluid to 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 of the cylinders 32 are interconnected and coupled with a fluid pump 45 which has a supply conduit 45 leading to it from the source of fluid supply,as shown the crank case M of the compressor.

Fluid pump 45 is shown operatively connected by means of a coupling 41 with an electric motor 43 which receives its operating current from a suitable source of electric power supply indicated by electrical conductors 49 through a switch 5|] in the circuit for controlling the operation thereof.

Switch 59 controlling the operation of the motor driven pump is actuated by a bellows 5| by either temperature or pressure of a storage room or any part of a plant in which the temperature or pressure is to be maintained within close limits. As shown in Fig. 1 this bellows is contolled by a thermal element 52 cooperating with the suction conduit |2 of the compressor.

In this arrangement of switch control the operation of the motor driven pump is automatically controlled so that its operation is in accordance with the temperature of the refrigerant in the suction line, and'in accordance with the conditions required the piston 3| is operated to close port 23 by valve 29 without using 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 weather conditions such as temperature and humidity .which normally have a decided effect on the compressor capacity, and the compressor will operate at full discharge capacity or at its intermediate discharge capacity in accordance with the control of switch 5| which, as shown in Fig. 1, is controlled by temperature.

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 by way of a check valve 53 to conduit 44 back to the source of fluid supply. This allows 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.

Check valve 53 is closed by a fluid pressurein the conduit 43. This valve as shown in Fig. 2, 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 in the casing, and a spring I 59 therein tends to force the valve upwardly to open the port through valve seat 58. In the upper portion of the valve casing is an abutment member 60 having a projection 6| thereon within the casing against which the movable valve member 55 is adapted to engage when forced upwardly by a spring 59. ,The position of the proje'ction 6| in the valve casing determines the upper limit of the movement of valve member 55'.

A check valve 53 with modifications is shown in Figure 5. Due to inequalities of tension of spring 59, a compensating spring 59' is positioned above valve member and in this arrangement the abutment member with its projection is replaced by a head 60' threaded into thecheck valve casing in place of the member 60. This head carries a stem 60a having a threaded engagement therewith at 601) and a packing member 690 forms a fluid tight seal around stem 60a. Stem 60a has an enlarged spring engaging member 6| on its inner end for engaging spring 59' and its upper end is formed for receiving an operating tool such as a kerf 60d 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 50 is auto-' matically closed, starting motor 45 so that pump 48 is operated to start the circulation of fluid through conduit 43 to the cylinders of pistons 3|. Check valve 53 has its valve member 55' closed against the spring 59 by the fluid pressure on account of the resistance of the fluid passing through this valve. This in turn 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 and thus the ports 23 by engagement of the valves 29 therewith and the compressor then operates at full capacity.

Referring again to the thermal element 52 which cooperates with suction line l2 of the compressor, it will be noted that this element is preferably positioned in a small chamber 62 which is closed at its upper end where the thermostatic bulb screws into it but is in open communication at its lower end with the suction line. A small liquid refrigerantline G3 conducting refrigerant from receiver 16, shown connected with conduit 11, is connected with an expansion valve 64 which in turn discharges through a connecting pipe 65 into chamber 62 around thermal element 52.

It will be noted that with valve 64 fluid refrigerant 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 correspond to the back pressure in the suction line, and this true saturated temperature is obtained because the gas so expanded does not mix with the superheated gas until it passes down to the suction line. However when valve 64 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 64 opened or closed as desired.

It will be obviou'stothose skilled in the art that various changes may be made in our device without departing from the spirit of the invention and herefore we do not limit ourselves to what is shown in the drawings and described in the specification but only as pended claims.

We claim:

1. In a refrigerating system, a compressor, capacity control means constructed to operate only during a portion of the compression stroke for varying the volumetric displacement of the compressor for varying the refrigerating capac-- ity of the system, and temperature responsive means for controlling said capacity control means, said temperature responsive means being constructed and arranged for actuation in accordance with the temperature corresponding to the pressure within the cooling element of the said refrigerating system.

2. In a. refrigerating system, a compressor,

capacity control means for varying the. volumetric displacement of the compressor for varying the refrigerating capacity of the system, manual means for controlling the capacity control means, and temperature responsive means for controlling said capacity control means, said temperature responsive-means being constructed and arranged for actuation in accordance with the temperature corresponding to the pressure within the cooling element of the said refrigerating system.

3. A refrigerating system including a compressor, an evaporator and suction line for returning refrigerant from the evaporator to the compressor and capacity control means constructed to operate only during a portion of the compression stroke for varying the volumetric displacement of the compressor for varying the refrigerating capacity of the system, and means for controlling said capacity control means in accordance with the temperature-of expanded gas on the low side of the system.

4. A refrigerating system including a compressor, an evaporator andsuction line for returning refrigerant from the evaporatonto the compressor and capacity control means for varying the volumetric displacement of the compressor for varying the refrigerating capacity of the system. and means for controlling said capacity control means in accordance with saturated gas temperature on the low side of the system.

- 5. In a refrigerating system, a compressor including a compression cylinder and piston therein, capacity control means constructed to operate only during a portion of the compression indicated in the ap-'-" stroke to affect the volumetric displacement of the compressor for varying the refrigerating capacity of the system comprising a port in the cylinder wall and a valve for closing said port,

fluid pressure means for closing said valve, and

prising a port in the cylinder wall and a valvefor closing said port, temperature responsive means for operating said valve to close the port and to permit the valve to open, and manual control means for closing said valve, said temperature responsive means being constructed and arranged for actuation inaccordance with the temperature corresponding to the pressure within the cooling element of the said refrigerating system.

7. In a refrigerating system, a compressor including a compression cylinder and piston therein, capacity control means for varying the volumetric displacement of the compressor for varying the refrigerating capacity of the system comprising a port in the cylinder wall and a valve for closing said port, temperature responsive means for operating said valve to close said port and to permit the said valve to open said port, and manual control means for operating said valve including a stem movable inwardly toward said valve to effect the engagement of said valve with said port in its closed position and movable outwardly away from said valve to release the valve from the effect of said manual control means.

8. In a refrigerating system, a compressor including a compression cylinder and piston therein, capacity control means for varying the volu metric displacement of the compressor for varying the refrigerating capacity of the system comprising a port in the cylinder wall and a valve for operating said port, manual control means for closing said valve including a stem movable inwardly toward said valve and outwardly away from said valve, a head on one end'of said stem arranged on one side to.form a control valve, a control cylinder head with a packer through which said stem operates, and said control cylinder head having a cooperating valve seat adapted to receive said control head valve and form a seal therewith when the stem is in its outermost position.

9. In a refrigerating system, a compressor including a compression cylinder and piston therein, capacity control means constructed to operate only-during a portion of the compression stroke for varying the volumetric displacement of the compressor for varying the refrigerating capacity of the system comprising a port in the cylinder wall and a valve for closing said port, a source of fluid supply, fluid pressure means for closing said valve, and means for controlling the supply of said fluid pressure means, and means for returning the fluid directly to the fluid supply source when the pressure of the fluid pressure means is reduced so as to permit the valve to open by the pressure in the compressor and thereby cause the compressor to operate at lower capacity, said temperature responsive means being constructed and arranged for actuation in accordance with the temperature corresponding to the pressure within the cooling element of the said refrigerating system.

10. In a refrigerating system, a compressor in- 4 cluding a compression cylinder and piston therein, capacity control means for varying the volumetric displacement of the compressor for varying the refrigerating capacity of the system comprising 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 having means for engaging said valve to operate it to its closed position, a source of fluid supply, a pump for supplying said fluid behind said piston for closing said valve, 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.

11. In a refrigerating system, a compressor, capacity control means for varying the refrigerating capacity of the compressor, a fluid supplysource, means for placing the fluid under pressure for operating said capacity control means to cause the refrigerating system to operate at full capacity, a conductor for returning fluid there.- from to said source 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.

12. In a refrigerating system, a compressor with fluid pressure operated capacity control means, a source of fluid supply and means for supplying fluid therefrom under pressure to said fluid pressure operated control means, a conductor for returning fluid from said control means to said source of supply, and a check valve therein for unloading the operating fluid and returning it to the source of fluid supply when the pressure thereon is reduced.

13. In a refrigerating system, including a compressor with fluid pressure operated capacity con-' trol means, a source of fluid supply and means for supplying fluid therefrom under pressure to said pressure operated control means, a conductor for returning fluid from said control means to said source of supply, and a check valve therein for unloading the operating fluid therethrough comprising a valve casing having a cylindrical 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 said casing, a spring under said valve member tending to move it from its closing position, and said piston portion having a restricted passageway therethrough permitting the passage of fluid therethrough when the pressure of the fluid is reduced.

14. In a refrigerating-system, including a compressor with fluid pressure operated capacity control means, a source of fluid supply and means for supplying fluid therefrom under pressure to said pressure operated control means, a conductor for returning fluid from said control means to said source of supply, and a check valve therein for.

unloading the operating fluid therethrough comprising a valve casing having a cylindrical 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 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 of said compressor for varying the refrigerating capacity of the system, and temperature responsive means for controlling said capacity controlled means.

NORMAN M. SMALL. LEON BUEHLER, JR.

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