US2920812A

US2920812A - Unloaders for refrigerant compressors

Info

Publication number: US2920812A
Application number: US629266A
Authority: US
Inventors: Jr Arthur W Courtney
Original assignee: Westinghouse Electric Corp
Current assignee: CBS Corp
Priority date: 1956-12-19
Filing date: 1956-12-19
Publication date: 1960-01-12
Anticipated expiration: 1977-01-12

Description

Jan. 12, 1960 A COURTNEY, JR 2,920,812

UNLOADERS FOR REFRIGERANT COMPRESSORS Filed Dec. 19, 1956 R TIMER l 21 W i! PRESSURE COMPRESSOR l DISCHARGE -7 TUBE 0| PUMP CONDENSER Inventoriuia fufl Wlbuflfneg,Jn

UNLOADERS FOR REFRIGERANT COMPRESSORS I Arthur W. Courtney, Jr., Grottoes, Va., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania "Application December 19, 1956, Serial No. 629,266

4 Claims. .(Cl. 230-7) 1 This invention relates to refrigerant compression, and

has as an object to improve the mechanisms used for unloading such compressors.

In many refrigerant compressors, unloading mechanisms are used for reducing the starting power, and for reducing the output as load reductions take place.

The E. R. Wolfert Patent No. 2,296,304 discloses a successful form of unloader in which unloading is accomplished by depressing suction valve reeds so that they do not act as check valves as they ordinarily do during the compression strokes of the pistons in their respective cylinders. A toothed bar called a comb is usedto hold a set of suction reeds down, this comb being forced down by refrigerant discharge gas pressure acting on a piston in an unloader cylinder located over the comb. The comb is returned from the depressed (unloading) position by relieving the pressure in the unloader cylinder and allowing return. springs and the spring action of the reeds to lift the comb to its neutral position.

Lubricating oil is recirculated with the refrigerant through a refrigeration system, and is used in some compressors for providing unloading pressure. It has the advantage that it is incompressible, but has the disadvantage that sufiicient oil pressure for unloading is not available immediately on the start of a compressor.

, This invention provides for starting the unloading of a compressor cylinder with discharge gas pressure, and,

embodiment of this invention.

, A conventional refrigerant compressor 10 driven by anelectric motor 11, has three pairs of cylinders. C1, C2 and C3,-with their associated cylinder heads H1, H2 and H3 respectively. Each cylinder head would have the unloader cylinder 12, although for simplicity of illustration and explanation the head H1 only is shown with unloader cylinders. The unloader cylinder 12 would contain pistons which would depress combs to depress suction reed valves for unloading as is conventional.

The compressor 10 would be connected by a gas discharge tube 13 to a conventional water-cooled condenser 14 which would be connected through a tube 15 and a conventional expansion valve 16 to a conventional evaporator 17, the outlet side of which is connected by a tube 18 to the suction side of the compressor.

The discharge tube 13 is connected through a tube 19, a three-way valve C, a tube 21 and valve B to the inlets of the unloader cylinders 12. The valve C is connected through a tube 23 to the suction side of the compressor 10. The valve C is adapted to be adjusted by a solenoid 24 to connect the tube 21 to the tube 19 or to the tube 23. The valve B is adapted to be opened and closed by a solenoid 26. A tube 27 connects the oil pump of the United States Patent 0 duced at any time into them.

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2 compressor through valve A and check valve 28 to the inlets of the cylinders 12. A solenoid 29 opens and closes the valve A.

The solenoids 24 and 26 are connected directly to supply line L2. The solenoid 26 is connected through contact 30 and armature 31 of relay 32 and L1 when the relay 32 is energized. The solenoid 24 is connected through contact 35 and armature 31 of the relay 32 when the relay 32 is energized.

The solenoid 29 is connected directly to the line L2, and through down contact 36 of switch 33 when the switch is on the contact 36, and contact 34 and armature 31 of the relay 32 when the relay is deenergized.

The solenoid 26 is also adapted to. be connected through the up contact 37 of the switch 33, when the switch is on contact 37, relay contact 34, and relay armature 31, to L1 when the relay is deenergized. V

The energizing winding of the relay 32 is connected through a timer 38 to the supply lines L1 and L2 which would be connected to the starter circuit of the compressor motor.11 so as to be energized when the compressor is started.

Operation 7 At the start of operation, the relay 32 would be energized through the timer 38, and would pull up its armature 31 against the contacts 30 and 35,- closing the energizing circuits of the solenoids 24 and 26. The solenoid 24 would then adjust the valve C to connect the tube 21 to the tube 19. The solenoid 26 would open the valve B, admitting discharge gas supplied through the tube 19, the valve C, the tube 21 and the valve B, into the unloader cylinder 12. r

The solenoid 29 is deenergized at this time, and its valve A is closed, preventing oil from the tube 27 from being supplied into the unloader cylinders 12.

The discharge gas pressure builds up rapidly immediately after starting, and causes the unloader cylinders 12 to unload their associated compressor cylinders.

At the end of about 10 to 15 seconds after the start, the timer 38 times out, deenergizing the relay 32. Its armature 31 then leaves the contacts 30 and 35 opening the previously described energizing circuits of the solenoids 24 and 26. The valve C, as a result of the deenergization of the solenoid 24, disconnects the tube 21 from the tube 19, and connects the tube 21 to tube 23. The valve B as a result of the deenergization of the solenoid 26 closes.

At the same time the relay armature 31 touches the relay contact 34 connecting the solenoid 29 to the supply lines so that the solenoid 29 is energized and opens the valve A, .supplying oil through the valve A and check valve 28 into the unloader cylinders 12 for unloading the compressor. The valve B is closed at this time so that there is no relief of this pressure.

Thereafter until the compressor is stopped, unloading is controlled by the switch 33. When this switch is placed on the down contact 36 by an operator or under thermostatic control as described in said Wolfert patent, unloading is accomplished. When loading is required the switch 33 is placed against its up contact 37. The switch in leaving its down contact 36 deenergizes the solenoid 29 causing the valve A to close.

The switch 33 on touching its up contact 37 energizes the solenoid 26 causing it to open the valve B, connecting the unloader cylinders 12 through the valves B and C, and tube 2 3 to the suction pressure permitting the relief of the oil pressure which previously caused unloading.

The oil filling of the unloader supply lines through valve A is not disturbed since no discharge gas is intro- Norrnal operation on oil thus is not hamperedas it is when discharge gas is introduced into the supply lines. g o

While the oil pressure available in a refrigerant compressor is not as great as is the discharge gas pressure, byusing the check valve 28, the oil pressure is sufficilent The suction valve reeds willbe opened during every compressor cylinder intake stroke. All that is really required of an unloader is sufficient force to make theiunload er combs follow in the path of the suction valve reeds during their opening. However, in a relativelyiinelastic system, in this case an oil filled system, the use of a check valve will prevent any return travel even though the supply pressure to the unloader cylinder is relatively low. The check valve makes the system irreversible except when the valve 3 is opened to relieve theuoil pressure when loading. As in the case of systems using discharge gas pressure, the spring loading and valve, reed tension will return the unloader assembly to sienna position.

I claim as my invention: a I

1. In an unloader for a cylinder of a. refrigerant compressor, said cylinder: having an unloader cylinder for opening the suction valve means of said compressor cylinder whenfluid is supplied into said unloader cylinder, the improvement comprising a gas control valve connected to said unloader cylinder, an oilcontrol valve connected to said unloader cylinder, a three-way valve connected to said gas control valve, gas tubing connecting said three-way valve to the discharge gas side of said compressor, v suction tubing connecting'said three-way valve to the suction side of said compressor, oil tubing connecting, said oil control valve to the oil supply of said compressor, means including control means connected to said gas and oil control valves and to said three-way valve for closing said oil control valve, for opening saidgas control valve, and for adjusting said three-way valve to connect said gas control valve to said gas tubing and to disconnect said gas control valve from said suction tubing, whereby discharge gas is supplied through said gas tubing, said three-way valve and said gas control valve into said unloader cylinder, means in eluding said control means for closing said gas control valve, for opening said oil control valve, and for adjusting said three-Wayvalve to connect said gas control valve to said suction tubing and to disconnect said gas control valve from said gas tubing, whereby oil is supplied through said oil tubing and said oil control valve into said unloader cylinder, and whereby suction is applied through said suction tubing, said three-way.valve and said gas control valve to said unloader cylinder when said oil control valve is next closed and said gas control valve is next opened, to relieve the oil pressure within said unloader cylinder, and means including said control means for closing said oil control valve and opening said gas control valve.

2. The invention claimed in claim 1 in which a check valve is provided and connected between said oil con- 2,920,812 p a e 4 t trol valve and 'said unloader cylinderf'said check valve permitting the flowof oil to said unloader cylinder when said oil control valve is open, and preventing the How of discharge gas into said oil control valve during the discharge strokes of said compressor cylinder.

3. In an unloader for a cylinder of a refrigerant compressor, said cylinder having an unloader cylinder for opening the suction valve means of said compressor cylinder when fluid is supplied into said unloader cylinder, the improvement comprising a gas control valve connected to said unloader cylinder, a gas control solenoid for opening and closing said gas control valve connected to said gas control valve, an oil control valve connected to said unloader cylinder, an oil control solenoid for opening and closing said oil control valve connected to said oil control valve, a three-way valve connected to said gas control valve, gas tubing connecting said three-way valve with the discharge gas side of said ;;compr essor suction tubingconnecting said three-way valve with the suction side .ofsaid compressor, a third solenoid for adjusting said threeeway valve to connect said gas control valve to said gas tubing or to said suction tubing, connected to said three-way valve, means including a relay adapted to be energized when said compressor is started, and a first switch which is closed when said relay is, energized, for energizing said gas control solenoid to open said gas control valve and for energizing 'said third solenoid to adjust said three-Way valve to connect said gas control valve to said gas tubing, timing means connected to said relay for deenergizing said relay a predetermined time interval after said relay is energized, said relay having a second switch which is closed when said relay is deenergized, means including said second switch for energizing said oil control solenoid to open said oil control valve, and means including a loader-unloaderv switch .connectedto said oil control solenoid for deenergizing and energizing said oil control solenoid to close and open respectively, said oil control valve, and connected to said gas control valve solenoid for energizing and deenergizing said gas control solenoid to open and close respectively, said gas controlvalve.

4. The invention claimed in claim 3 in which a check valve is provided and connected between said oil control valve and said unloader cylinder, said check valve perrnitting the flow of oil to said unloader cylinder when said oil control valve is open, and preventing the flow of discharge gas into said oil control valve during the discharge strokes of said compressor cylinder.

References Cited in the file of this patent I UNITED STATES PATENTS, 2,389,348