US2458933A

US2458933A - Unloader for reciprocating gas compressors

Info

Publication number: US2458933A
Application number: US717002A
Authority: US
Inventors: Wayne E Dodson
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1946-12-18
Filing date: 1946-12-18
Publication date: 1949-01-11
Anticipated expiration: 1966-01-11

Description

Jan. 11, 1949. w, bopso 2,458,933

UNLOADER FOR RECIPRQCATING GAS COMPRESSORS Filed Dec. 18. 1946 2 She'ets-Sheet 1 v I nvenc or:

Wayne El. Dodson.

' His Attorney.

Jan. 11, 1949.

w. E. DODSON UNLOADER FOR RECIPROCATING GAS COMPRESSORS 2 Shoots-Sheet 2 Filed Deg. 18, 1946 van .l lll I n ventorfv Wayne E3. Dodson, by M 1124* His Attorney.

Patented Jan. 11, 1949 UNLOADER FOR. RECIPROCATING GAS coMPaEssoas Wayne E. Dodson, Caldwell, N. J., assignor to General Electric Company, a corporation of New York Application December 18, 1946, Serial No. 717,002

My invention relates to reciprocating gas compressors and particularly to an improved unloading arrangement for such compressors.

Gas compressors may be unloaded by providing a bypass for the return of compressed gas directly from the discharge to the intake of the compressor. A check valve may be provided to prevent the return of high pressure gas from the system served by the compressor when the bypass is opened. In multiple cylinder reciprocating compressors the load on the compressor may be changed by unloading one or more'of the cylinders, and in such compressors a check valve is necessary at each cylinder or group of cylinders to be unloaded so that the compressed gas supplied by the loaded cylinders cannot return Claims. (Cl. 230-22) air or other fluid circulated thereover, and the I hot compressed refrigerant therein is thus cooled and liquefied and is then delivered to a receiver 1. The liquid refrigerant flows to the evaporator 5 through a liquid line I! under control of a thermostatic expansion valve 9 having a thermal bulb The check valves provided for this and having a check valve for preventing back flow of compressed refrigerant gas during unloaded operation of the compressor.

Further objects and advantages of my inven tion will become apparent as the following description proceeds, and the features of novelty which characterize my invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

For a better understanding of my invention reference may be had to the accompanying drawings in which Fig. 1 represents diagrammatically a fluid cooling system provided with a compressor embodying my invention, and Fig. 2 is a detail sectional view of one of the cylinders of-the compressor of Fig. 1 including the bypass control.

Referring now to the drawings, the cooling system shown in Fig. 1 comprises a multiple cylinder compressor having cylinders I and 2 connected in parallel to deliver refrigerant to a condenser I and to withdraw vaporized refrigerant through a suction line I from an evaporator 5. In order to simplify the drawing, the driving mechanism for the compressor has been omitted, it being understood that pistons in both cylinders I and 2 may be driven from a common crankshaft in the usual manner. The evaporator 5 is arranged in a duct or conduit 8 through which the medium to be cooled is circulated. The condenser 3 is cooled by or ieeler l0 secured to the suction line 4 near the outlet of the evaporator.

During the operation of the system illustrated,

should the load on the evaporator 5 be greatly reduced it may be desirable to reduce the effective capacity of the compressor, and in order to reduce the capacity without discontinuing operation of the'compressor a bypass Ii is provided between the discharge chamber of the cylinder 1 within a head l2 of the cylinder and the suction line 4, the bypass l I being controlled by a valve i3 actuated by a solenoid ll. The solenoid i4 is arranged to be energized by operation of a snapacting or over-center switch l5 when the pressure within the suction line 4 falls below a predetermined value and causes a bellows I6 which is in communication with the line 4 through a duct ll to contract as illustrated and actuate the switch i5 through a rod i8 which pulls a spring i9 over center to snap the switch i5 from its right-hand position, to its left-hand position (as shown) to energize the solenoid It by connecting it across supply lines 20. Energization of the solenoid l4 opens the valve is so that the cylinder i pumps refrigerant gas directly back to the suction line through the conduit H and the one cylinder is thus unloaded.

Although the control switch i5 has been illustrated as operated in accordance with suction line pressure, it obviously may be operated manually or by any condition of the system suitable g} for indicating the requirement for unloading.

The details of construction of the cylinder i and the arrangement of the bypass are clearly shown in Fig. 2. The cylinder i comprises a block 2i having a cylinder 22 therein and a piston 23 arranged to be reciprocated'within the cylinder. A valve plate 24 is mounted on top of the cylinder and on this plate are arranged intake and exhaust connection ii. The head I2 is formed to provide a discharge chamber or passage 32 above the 3 valve 28 and a passage 33 separated from the par;-

sage 32 by a partition 34; the passage 33 is in duit II to the suction line 4 is controlled by the valvei3 which includes a movable valve member 39 for controlling a port 40 in the valve body.

When the'solenoid I4 is energized to move the valve member 39 to its open position against the force of a spring 39a, gas discharged into the chamber 32 is delivered to the suction line 4 through'the conduit I so that the chamber 32 is connected to the inlet passage 29 through the conduit i l, the suction line 4 and the conduit 30.-

In order to prevent thereturn of compressed gas from the connection 35, which is in communication with the condenser 3, a check valve 4| is arranged to close an opening 42 in the partition 34. The check valve 4| comprises a piston mounted in a cylinder 43 at the top of the head l2 and which is closed by a head plate 44. The cylinder 43 and piston 4| are arranged for vertical movement of the piston so that the check valve is biased by gravity to its lower position to close the opening 42. The piston 4| is provided with a cylindrical cavity or chamber 45 which is in communication with the high pressure passage 33 through a duct or bleeder 46. Thus when the valve 4| is in its lower position, high pressure gas enters the cylinder 43 and holds the valve closed. It will thus be evident that when the bypass valve 39 is open, as shown in Fig. 2, the check valve 4| is held in its closed position, the pressure in the chamber 32 being that on the low pressure side of the refrigerating system.

When the valve 33 is closed to load the cylinder 22 of the compressor 2|, the gas discharged into the chamber '32 will reach a pressure higher than that in the passage 33 and will lift the check valve 4| allowing the gas to be discharged from the compressor through the connection 35. The operation of the check valve 4| when the compressor is loaded may result ln'chattering of the valve and consequent noise and wear, which is objectionable. In order to prevent this chattering and wear of the valve, I provide a conduit 41 connected betweenthe suction line 4 and the cylinder 43 under control of a manual valve 48 and a valve 49 actuated by a solenoid 50. As shown in Fig. 1, the solenoid 50 is energized when the switch I is in its right-hand position. Thusthe switch l5 energizes only one of the solenoids l4 and 50 at a time so that only one of the conduits II and 41 can be open at one time. When the valve 49 is opened, the cylinder 43 is in communication with the suction line and the pressure in the cylinder is reduced so that the piston valve 4| is retracted and held in its retracted position during the loaded operation of the compressor. The manual valve 48 may be adjusted to control the bleeding of gaseous refrigerant through the passage 46, cylinder 43 and conduit 41 back to the suction line and in this manner the capacity of the compressor which is lost during loaded operation may be reduced or noise will result during the loaded operationofthe compressor and wear or the check valve provided a simple. and effective arrangement which makes it possible to employs. check valve to prevent return of compressed gas toan unloaded cylinder of a multicylinder compressor without resultant noise or chattering of the check valve during loaded operation of the compressor.

' While I have described my invention in con-' nection with a. two-cylinder compressor for supp ying a refrigerating system, other applications will readily be apparent to those skilled in the art. I do not. therefore, desire my invention to be limited to the specific construction illustrated and described, and I intend by the appended claims to cover all modifications within the spirit and scope oi-my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A reciprocating gas compressor comprising a cylinder having intake and discharge valves, means providing intake and discharge passages adjacent said intake and discharge valves respectively, an outlet connection communicating with said discharge passage, bypass means provldingcommuuication between said discharge and intake passages for unloading said cylinder, means for closing said bypass to load said cylinder, 9. check valve for preventing return of gas through said outlet connection to said discharge passage upon opening of said bypass, and means rendered efiective upon the loading of said cylinder for retaining said check valve in its open position to prevent vibration of said check valve. I

2. A reciprocating gas compressor comprising a cylinder having intake and discharge valves, means providing intake and discharge passages adjacent said intake and discharge valves respectlvely, an outlet connection communicating with said discharge passage, bypass means providing communication between said discharge and intake passages for unloading said cylinder, means for closing said bypass to load said cylinder, 2. check valve for preventing return of gas through said outlet connection to said discharge passage upon opening of said bypass, and means effective during the loaded operation of said compressor and utilizing the diiierence in pressure between the inlet an outlet of said compressor for retaining said check valve in its open position.

3. A reciprocating gas compressor comprising a cylinder having intake and discharge valves. means providing intake and discharge passages adjacent said intake and discharge valvesrespectively, an outlet connection communicating with said discharge passage, bypass means providing communication between said discharge and intake passages for unloading said cylinder, means for closing said bypass to load said cylinder, a check valve for preventing return of gas through said outlet connection to said discharge passage upon opening of said bypass, said check valve including means providing a closed cylinder and a piston arranged therein, said closed cylinder having limited communication with said outlet connection whereby said valve is held closed by the pressure of gas in said closed cylinder, and means efiective during the loaded operation of said compressor for reducing the pressure in said closed cylinder to maintain said check valve in its open position when said bypass is closed.

4. A reciprocating gas compressor comprising a cylinder having intake and discharge valves. means providingintake and discharge passages adjacent said intake and discharge valves respectively, an outlet connection communicating with said discharge passage, bypass means providing communication between said discharge and intake passages for unloading said cylinder, means for closing said bypass to load said cylinder, a check valve for preventing return of. gas through said outlet connection to said discharge passage upon opening of said bypass, said check valve including means providing a closed cylinder and a piston arranged therein, said closed cylinspectively, an outlet connection communicatingwith said discharge passage, bypass means providing communication between said discharge and intake passages for unloading said cylinder,

a check valve for preventing return of gas,

through said outlet connection to said discharge passage upon opening of said bypass, said check 25 Number valve including means providing a closed cylinder and a piston arranged therein, said closed cylinder having limited communication with said outlet whereby said valve is held closed when the pressure in said connection is greater than that in said discharge passage, means connecting said closed cylinder with said intake passage to bleed refrigerant from said discharge connection to said intake passage to reduce the pressure in said closed cylinder for retaining said check valve in its open position,a control valve for said connection to said closed cylinder, and means for maintaining each of said control valves in its closed position when the other of said control valves is in its open position whereby said check valve is effective only during the period when'said compressor is unloaded.

WAYNE E. DODSON.

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

UNITED STATES PATENTS Name Date Kinney Apr. 5, 1927 Swartwout Aug. 11, 1931 Swanson et al Man-1, 1932 Hirsch Aug. 30, 1932 Lindsay Jan. 9, 1934