US2080288A - Refrigerating apparatus - Google Patents

Description

May 11, 1937. A. A. MCCORMACK 2,080,288

REFRIGERATING APPARATUS Filed June 30, 1954 Z8 6 40 4 Z 24 30 8 E 3 32 Qg ftwjhzr iz) z gwuc/wtoo atented 11, 1937' STATE 1,1,

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This invention relates to refrigerating apparatus and more particularly to unloading devices for compressor units, for mechanical refrigerating machines of the type comprising a refrigerant 5 liquefying unit which may include a compressor, a condenser and a receiver for liquid refrigerant and a refrigerant evaporating unit which may comprise an evaporator and a valve controlling the expansion of liquid refrigerant into the evaplil orator. K

The compressor in a refrigerating machine of this type is commonly driven by an electric motor under the control of a suitable automatic switch for intermittently operating the motor and they 15 compressor in accordance with temperature or pressure conditions within the system. In the normal operation of such a system, the load on the compressor and motor in starting after an idle period is high, and it is an object of this inl vention to provide a mechanism which will relieve the load on the compressor during starting and permit the compressor to come up to normal speed without an appreciable load.

It is also an object to provide an unloading mechanism which/will relieve the load on the compressor during the starting and which is responsive to the rate of refrigerant discharged by the compressor.

A further object is to provide an unloading de- 80 vice which is located outside the compressor and which may be applied to existing refrigerating machines by merely making suitable connections to the refrigerant conduits without altering the construction of the compressor itself.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawing, wherein a preferred form of the-present invention is clearly shown.

In the drawing:

The figure is a diagrammatic view of a refrigerating machine embodying the present invention, the unloading mechanism being shown on an enlarged scale and in .cross section.

45 The refrigerating machine shown diagrammatically in the drawing comprises a compressor it having a discharge outlet I2 which is connected by a conduit M to an unloading mechanism. it. A conduit l8 leadsfrom the unloading mechanism to the condenser 20, which, in turn,

is connected to a liquid refrigerant receiver 22.

The receiver 22 is connected by a conduit 24 to an evaporator 26 which may contain the usual float valve (not shown) for controlling the ex- 55 pension of liquid refrigerant into the evaporator.

19%, Serial No. 733,277

(or. ta-ns) A conduit 23 connects the evaporator to the intake to of the compressor It. Communicating with the conduit 28 is a conduit 32 having a branch 3% communicating with a bellows 36 for operating the snap switch 38, which, in turn, controls the motor it]. The motor til drives the compressor through belt drive ti. Conduit it also communicates with the unloading mechanism it. The parts of the refrigerant circuit from the compressor discharge 82 through the conduit it, unloading valve it, conduit l8, condenser Zt, receiver 22 and conduit 2t may be termed the high side of the system, while the evaporator 26, the conduits 28, '32 and i4 and bellows 36 may be termed the low side of the system.

The unloading mechanism comprises a body member 42 having a cylindrical interior which is divided into two chambers M and 46 by a reciprocable piston 48. Chamber 46 communicates with the high side through the conduit I4, while the chamber 44 communicates with the low side through the conduit 32. The piston 48 is biased by a spring 50 to the left in the figure and carries a valve stem 52 loosely mounted in a bore 54 in the head of the piston. A spring 55 normally biases the valve stem 52 to the right. The outer end of the valve stem 52 carries a valve head 56 adapted to close the open end of the conduit 32 when the piston i8 is moved to the right. At one side of the body member 42, there is formed a port 58 communicating withthe conduit 3. A check valve 60 is interposed between the port 58 and the conduit It. The piston 48 has a port 62 adapted to communicate with the port 58 when the piston 48 is in the right hand position. At the opposite side of the body member 42, there is provided a passage 64 connecting the chamber 44 with the chamber 46. Interposed in the passage 64 is a restriction 66 formed by an adjustable needle valve 68. A stop ring 10 is interposed in the interior of the body 42 to limit movement of the piston 48 under the urge of the spring 50. A passage 12 is cut in the wall of the chamber 44 and in the piston 48 to conheat the chamber M with the port 58 in all positions of the piston is.

During normal operation of the system the parts lie in the position shown in the figure. Gaseous refrigerant is withdrawn from the evaporator 26 by the compressor I0 and discharged through the conduit l4 into the chamber 46. The major portion of the refrigerant discharged passes through the ports 52 and 58 and through the check valve 50 to the condenser 20. A small portion of refrigerant passes from the chamber 46 to the chamber 44 through the passage 64 and the restriction 66. From the chamber 44, this small quantity of refrigerant passes through the passage 12 to the port 58 where it joins the major portion of refrigerant flowing through the high side. The valve 56 maintains the conduit 32 cut off from the chamber 44. The piston 48 is maintained in the right hand position by a slight pressure difi'erence maintained between the refrigerant in the chamber 46 and that in the chamber 44. The pressure drop occurs at the ports 58 and 62 for the major body of refrigerant flowing through the device, and at the restriction 66 for the smaller portion of refrigerant flowing through the passage 64. When the control switch 38 is opened, due to the low side pressure having been reduced to the desired value, the motor 48 and the compressor I0 are stopped. The pressure difference between the chambers 44 and 46 will then become equalized, due to passage of refrigerant from the chamber 46 through the restriction 66 and ports 62 and 58 and passage 12 into the chamber 44. This permits the spring 58 to move the piston 48 to the left, closing the ports 58 and 62 and opening the valve 56. The parts will lie in this position when the compressor is again started by the switch 38. During the initial operation of the compressor and before its normal high speed is reached, all of the small quantity of refrigerant compressed at low speed will pass through the restriction 66, and since the valve 56 is opened, will be returned directly to the intake of the compressor through the conduits 32 and 28. This will permit the compressor to start without material load, as long as the speed is low enough to prevent compressing a greater quantity of refrigerant than will pass through the restriction 66. As the speed of the compressor increases, however, and the rate of refrigerant flowing through the conduit l4 be- .comes greater than will pass restrictor 66, pres sure will be built up gradually in the chamber 46, which in turn will move the piston 48 gradually back to the position shown in the drawing, in which the unloading valve 56 is closed and operation will then be resumed in the manner first described. The effect on the unloading valve 56 of any slight pulsations in pressure in the chamber 46 inherent in a reciprocating type of compressor, such as that shown, is eliminated by the lost motion connection between valve stem 52 and the piston 48 which, together with spring 55, permit the valve 52-56 to float in piston 48. The unloading mechanism may be adjusted for various back pressures and for various sizes of compressors by varying the size of the restriction 66 through the adjustable needle valve 68 and also by replacing the spring 58 with an equivalent spring of different calibration.

While the form of embodiment of the invention as herein disclosed constitutes a preferred form, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow.

What is claimed is as follows: 1. In a refrigerating system having a refrigerant liquefying unit including a compressor and a refrigerant evaporating unit, the combination pressor is loaded, means responsive to an increase in the volume of refrigerant compressed for moving said valve from the first position to the second position and means for varying the response of said last means to an increase in volume of refrigerant compressed.

2. In a refrigerating system having a refrigerant liquefying unit including a compressor and a condenser and a refrigerant evaporating unit, the combination of a compressor unloading mechanism including a by-pass between the compressor and evaporator and means located in the refrigerant circuit between the compressor and the condenser for controlling said bypass.

3. In a refrigerating system having a refrigerant liquefying unit including a compressor and a condenser and a refrigerant evaporating unit, the combination of a compressor unloading mechanism including a by-pass between the compressor and evaporator and means including a piston located in the refrigerant circuit between the compressor and the condenser for controlling said by-pass.

4. In a refrigerating system having a refrigerant liquefying unit including a compressor and a refrigerant evaporating unit, the combination of a compressor unloading mechanism movable from a first position in which the compressor is unloaded to a second position in which the compressor is loaded, means responsive to an increase in the volume of refrigerant compressed for moving said mechanism from the first position to the second position and means for varying the response of said last means to an increase in volume of refrigerant compressed.

5. An automatic unloading device for refrigerating machines which include a compressor, a condenser and an evaporator comprising a valve body, means in the body defining a passage adapted to communicate between the discharge of the compressor and the condenser, means in the body defining a passage adapted to communicate between the discharge of the compressor and the intake of the compressor, a pressure responsive device in the valve body and valves controlled by said pressure responsive device for controlling both passages.

6. An automatic unloading device for refrigerating machines which include a compressor, a condenser and an evaporator, comprising a valve body, means in the body defining a passage adapted to communicate between the discharge of the compressor and the condenser, a pressure responsive device in the valve body, a valve controlled by said pressure responsive device for controlling said passage and unloading means for the compressor also controlled by said pressure responsive device.

'7. An automatic unloading device for compression refrigerating machines which include a compressor and a high side and a low side comprising a body member including a first chamber adapted to communicate with the high side and a second chamber adapted to communicate with the low side and the high side, a restricted by-pass connecting the two chambers, a valve operating member movable in accordance with the difference in pressure between the two chambers, a first valve associated with the valve operating member for controlling the flow of refrigerant in the high side and a second valve associated with the valve operating member for controlling communication between high side and the low side through said by-pass.

8. An automatic unloading device for refrigerating machines which include a compressor and a high side and a low side, comprising means forming a restricted passage between the high side and the low side, a restriction forming two portions, a valve for cutting ofi said passage from the low side and means responsive to an increase in pressure difference in said two portions of the high side created by flow of refrigerant through the restriction for controlling said valve.

9. An automatic unloading device for refrigerating machines which include a compressor and a high side and a low side comprising means forming a restricted passage between two points in the high side and having communication at one end with the low side, a valve for cuttting off said passage from the low side while maintaining both ends of said passage in communication with different points of the high side and a valve for controlling said valve.

10. An automatic unloading device for refrigerating machines which include a compressor and a high side and a low side comprising means forming a restricted passage between two points in the high side and having communication at one end with the low side, a valve for cutting off said passage from the low side while maintaining both ends of said passage in communication with difierent points of the high side and a valve operating device responsive to the difference in pressure between" said points in the high side for controlling said valve and a second valve controlled by said valve actuating device for controlling the pressure difference between said points.

11. An automatic unloading device for refrigerating machines which include a compressor, a condenser and an evaporator comprising a valve body, means in the body defining a passage adapted to communicate between the discharge of the compressor and the condenser, means in the body defining a passage adapted to communicate between the discharge of the compressor and the intake of the compressor, a pressure responsive device in the valve body and valves controlled by said pressure responsive device for controlling both passages and a resilient operating connection between said pressure responsive device and one of said valves.

12. An unloading device for refrigerating machines which include a compressor and a high side and a low side, comprising a body member, means in the body member defining a passage adapted to be in series connection with the high side, means defining a passage adapted to connect the high side directly with low side for unloading the compressor, a valve in the second passage and means responsive to the rate of flow of refrigerant through the first passage for controlling said valve.

13. The combination in a refrigerating machine of a compressor, a condenser, an evaporator and a compressor unloading device comprising means defining a conduit adapted to be connected in series between the compressor discharge .7:

and the condenser and means responsive to the rate of fiow of refrigerant through said conduit for equalizing the pressure between the intake and discharge of the compressor.

ALEX A. MCCORMACK.

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