Fail safe mechanical oil shutoff arrangement for screw compressor
AssigneeAmerican Standard Inc.
InventorsJerome C. Roach, Garry E. Andersen
Life of this patent
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Abstract
Apparatus as disposed internal of a refrigeration screw compressor which, upon compressor shutdown, shuts off the flow of oil injected into the compressor's working chamber and the oil which is directed to the compressor rotor bearings and which at compressor startup opens oil flow to those locations by the use of ambient internal compressor conditions that inherently exist at those respective times. The operation of the apparatus is therefore "fail safe" and the need for external oil flow cutoff valving and the need to monitor and/or prove oil flow within the compressor is eliminated.
Claims19
A rotary screw refrigerant gas compressor comprising:
- a housing defining a working chamber, said housing further defining a suction port, a discharge port and an oil supply passage, all in flow communication with said working chamber, said housing further defining an oil flow cutoff passage which is in flow communication with said oil supply passage, with an area in said compressor which is at a pressure less than compressor discharge pressure when said compressor is in operation and with an area in said compressor downstream of said discharge port which is at compressor discharge pressure when said compressor is in operation;
- and
- a pair of screw rotors meshingly disposed for rotation in said working chamber;
- and
- valve means disposed within said compressor and positionable to (i) occlude said oil supply passage to prevent the flow of oil therethrough and to (ii) open said oil passage to permit the flow of oil therethrough in direct response to ambient conditions in said compressor downstream of said discharge port which inherently exist at compressor shutdown and startup respectively.
A screw compressor comprising:
- a housing defining a working chamber, an oil supply passage and an oil cutoff passage, said housing further defining a suction port and a discharge port in flow communication with said working chamber, said oil cutoff passage being in flow communication with said oil supply passage and communicating between an area in said compressor downstream of said discharge port and an area in said compressor which is at a pressure less than compressor discharge pressure when said compressor is in operation, said downstream area being in flow communication with said discharge port;
- a pair of screw rotors meshingly disposed in said working chamber;
- means for driving one of said screw rotors;
- means for stopping the backflow of gas to said working chamber from downstream thereof immediately subsequent to the stoppage of said means for driving one of said screw rotors motor;
- and
- valve means disposed in said first passage, said valve means having an upstream surface exposed to pressure in said area which is at less than discharge pressure when said compressor is in operation and a downstream surface exposed to pressure in said area downstream of said discharge port, said valve means being positionable to occlude the flow of oil through said oil supply passage by the pressure differential which develops across said valve means subsequent to the operation of said means for stopping backflow to stop gas backflow.
What is claimed is a screw compressor-based refrigeration system comprising:
- an oil supply;
- a condenser;
- an expansion valve;
- an evaporator;
- and
- a screw compressor, said compressor, condenser, expansion valve and evaporator being serially connected to form a hermetically closed refrigeration system having a high pressure side, downstream of said compressor and upstream of said expansion valve, and a low pressure side, downstream of said expansion valve and upstream of said compressor, said compressor having locations which are at a pressure intermediate compressor discharge pressure and compressor suction pressure when said compressor is in operation, said compressor
- (i) defining a working chamber in which a pair of screw rotors are disposed, an oil supply passage in flow communication with said oil supply, a suction port in open flow communication with said working chamber and with said low pressure side of said system, a discharge port in open flow communication with said working chamber and said high pressure side of said system, an oil cutoff passage in flow communication with the high pressure side of said system, with one of said intermediate pressure locations in said compressor and with said oil supply passage;
- and
- (ii) having valve means disposed in said cutoff passage, said valve means being positioned to prevent flow through said oil supply passage by the ambient conditions which inherently exist internal of said compressor immediately subsequent to compressor shutdown and being positioned to permit the flow of oil through said oil supply passage by the ambient conditions which inherently exist internal of said compressor immediately subsequent to compressor startup.
The screw compressor-based refrigeration system according to claim 13 wherein said valve member has an upstream surface exposed to pressure in said one of said intermediate pressure locations in said compressor and a downstream surface exposed to pressure in said high pressure side of said refrigeration system, the position of said valve member being dependent upon the pressure differential across said valve member.
Dependencies are inferred from the claim text.