Abstract A variable capacity screw compressor comprising a casing, housing two intersecting bores defining a working chamber in which a pair of intermeshing screws comprising helical lands and intervening grooves are mounted to rotate and to compress a working fluid as it is being passed axially through the working chamber from a low pressure inlet wall to a high pressure outlet wall, the inlet wall having an inlet passage in substantially axial alignment with the axes of the rotary screws for filling the ends of the grooves facing the axial inlet passage with working fluid. The capacity of the compressor to operate within a predetermined range of load variations from full load to no load conditions is regulated by a slide valve located on the high pressure side of the compressor and being axially displaceable in response to varying load conditions to expose a by-pass opening for venting partially compressed working fluid directly into the grooves of the compressor screws at a location between the bypass opening and the axially aligned inlet passage to thereby interrupt admission of cold working fluid into the grooves from the inlet passage.
A variable capacity screw compressor comprising: a. a casing, housing two intersecting bores defining a working chamber in which a pair of intermeshing screws having helical lands and intervening grooves are mounted to rotate and compress a working fluid as it is being passed axially through said working chamber from a low pressure inlet wall to a high pressure outlet wall, said walls being located at opposite axial ends of said casing; b. an inlet passage in said inlet wall located in substantially axial alignment with the axes of said screws for admitting working fluid into the ends of the grooves facing said inlet passage as they become exposed during rotation; c. a slide valve comprising a portion of the casing located on the high pressure side of said working chamber and being axially displaceable therein in response to varying load conditions; d. said slide valve being effective to expose a by-pass opening in said working chamber to a degree corresponding to the axial displacement of the slide valve to vent partially compressed air from the working chamber; e. means for passing said vented partially compressed working fluid directly into the grooves of said screws at a location between said by-pass opening and said axially aligned inlet passage whereby to interrupt admission of low pressure working fluid.
Claim 2
Dependent Claim
217 words
A variable capacity screw compressor comprising: a. a casing, housing two intersecting bores defining a working chamber in which a pair of intermeshing screws having helical lands and intervening grooves are mounted to rotate and compress a working fluid as it is being passed axially through said working chamber from a low pressure inlet wall to a high pressure outlet wall, said walls being located at opposite axial ends of said casing; b. an inlet passage in said inlet wall located in substantially axial alignment with the axes of said screws for admitting working fluid into the ends of the grooves facing said inlet passage as they become exposed during rotation; c. a slide valve comprising a portion of the casing located on the high pressure side of said working chamber and being axially displaceable therein in response to varying load conditions; d. said slide valve being effective to expose a by-pass opening in said working chamber to a degree corresponding to the axial displacement of the slide valve to vent partially compressed air from the working chamber; e. means for passing said vented partially compressed working fluid directly into the grooves of said screws at a location between said by-pass opening and said axially aligned inlet passage whereby to interrupt admission of low pressure working fluid.
Claim 3
Dependent Claim
64 words
A variable capacity screw compressor according to claim 1, in which the means for passing the vented working fluid comprises a port in the working chamber casing, said port being so located that the leading flank of the lands of said screws will commence to pass across the rear edge of said axial inlet passage as the following grooves become aligned with said port.
Claim 4
Dependent Claim
24 words
A variable capacity screw compressor according to claim 2, in which a port is provided in said casing for each of the two bores.
Claim 5
Dependent Claim
37 words
A variable capacity screw compressor according to claim 2, in which the width of the port in the casing is of the same order of magnitude as the distance between the leading flanks of two successive lands.