Piston unloader arrangement for screw compressors
AssigneeAmerican Standard Inc.
InventorsGarry E. Andersen, Peter J. Linnert
Life of this patent
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Abstract
A screw compressor employs a piston unloader which is disposed in a bore remote from the compressor's working chamber. Flow communication between the bore and working chamber is through a series of non-overlapping unloader ports. The unloader piston has a notched end face which effectively causes the unloader ports to overlap in operation. Precise and continuous capacity control of the compressor over a predetermined portion of its operating range is thereby achieved while internal high to low side gas leakage within the compressor and the clearance volume of the unloader ports is minimized. Compressor efficiency is thereby increased.
Claims16
A screw compressor comprising:
- a housing defining a working chamber, a bore remote from said working chamber and a plurality of ports communicating therebetween said ports being spaced apart so that no portion of any one of them overlaps a adjacent port along said bore;
- and
- means, disposed for axial movement within said bore, for unloading said compressor in a continuous manner by providing an uninterrupted unloading path from said working chamber to said bore through said ports.
A screw compressor comprising:
- a rotor housing defining a generally axially running working chamber and an unloader bore generally parallel thereto, said working chamber and said unloader bore being in flow communication through a plurality of ports, said ports being axially spaced along said bore so that no portion of a first port overlaps a second port along the axis of said bore, said bore being in flow communication with a portion of said compressor which is at compressor suction pressure when said compressor is in operation;
- an unloader piston disposed in said bore for axial movement therein between a full load and a full unload position, said piston being configured to provide a flow path between said working chamber and said bore through at least one of said ports other than when said piston is in said full load position;
- and
- means for controllably positioning said piston in said bore so as to provide for the continuous unloading of said compressor over at least a predetermined portion of the compressor's operating range.
A method for unloading a screw compressor where said compressor defines a working chamber a bore running generally parallel thereto and where said working chamber and bore communicate through a plurality of non-overlapping ports spaced along said bore comprising the steps of:
- disposing a piston unloader in said bore said piston unloader configured so as to cause said non-overlapping ports to overlap in effect by providing a flow path therebetween;
- and
- controllably positioning said piston unloader in said bore in and between a full load and a full unload position so that at least one of said ports is in flow communication with said bore at all times other than when said piston is in said full load position.
Dependencies are inferred from the claim text.