Pumps – With condition responsive pumped fluid control – Expansible chamber pump distributor operation modified
Reexamination Certificate
1999-06-30
2001-05-08
Leung, Philip H. (Department: 3742)
Pumps
With condition responsive pumped fluid control
Expansible chamber pump distributor operation modified
C417S313000
Reexamination Certificate
active
06227815
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention is directed to the field of compressors, and is particularly directed to reciprocating compressors.
There are three types of capacity controls that are common to reciprocating and other positive-displacement compressors. In a smaller compressor, a pressure switch is utilized to start and stop the motor in response to changes in discharge pressure. In a medium size compressor a constant speed control is often used in combination with the pressure switch. Constant speed control may be accomplished by throttling the intake of the compressor. Other capacity control techniques which involve changing the clearance volume or modifying the port timing of the compressor are also in use for rotary compressors. Large reciprocating compressors use capacity variation techniques based on disabling the compression process by opening the cylinder inlet or outlet valves. For a compressor driven by a variable-speed motor or engine, the speed of the motor or engine can be varied to control the capacity of the compressor.
The technique of throttling the intake has not been applicable to lubricated reciprocating compressors, which use one or more pistons to drive a compressed gas flow. By throttling the intake, the gas pressure at the top of the piston would be lower than the crankcase pressure, which could allow oil to migrate from the crankcase to the top of the piston. Such migrating oil could become entrained into the compressed gas.
In order to prevent pressure buildup inside the lubricant chamber, all reciprocating compressors are equipped with a vent or breather system. Some reciprocating compressors have a vent that is connected to the inlet plenum by means of a conduit which may include a check valve. Other compressors have a vent, with or without a check valve, that is open to the surrounding atmosphere.
SUMMARY OF THE INVENTION
In accordance with the present invention, a reciprocating compressor apparatus includes a piston and a drive mechanism configured to reciprocate the piston. A housing contains a lubricant for the drive mechanism in a lubricant chamber at one side of the piston. The apparatus further includes a conduit pneumatically communicating the lubricant chamber with an opposite side of the piston, a check valve that prevents flow through the conduit from the intake plenum to the lubricant chamber, and an intake valve that acts as a throttling device to reduce the pressure in the inlet plenum.
In a preferred embodiment of the present invention, the apparatus further includes a pilot valve or other operator. The intake valve is operative to control intake gas flowing to the intake plenum and piston. The pilot valve or operator sends a signal to the intake valve in response to a pneumatic fluid pressure output from the compressor. The intake valve reduces the flow of gas into the intake plenum if the compressor output pressure is rising.
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Abt Joseph A.
Chandra Johan B.
Campbell Hausfeld/ Scott Fetzer Company
Fastovsky Leonid
Jones Day Reavis & Pogue
Leung Philip H.
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