Intermittent service screw compressor

Claim 1

A continuously driven screw compressor adapted for intermittent compressor operation, comprising: a compressor housing means (1) which comprises a casing wall means (2) which encloses at least two radially overlappping compression chambers (5, 6) each of which accommodates a respective helical rotor (7, 8), said helical rotors each being fixedly connected to a respective bearing shaft (9, 10); said compressor housing means including a compressor inlet (12); said housing means (1) having spaced apart end portions, and comprising at respective end portions thereof a high-pressure end wall means (4) at a high pressure end of the compressor, and a low-pressure end wall means (3) at a low pressure end of the compressor; said casing wall means (2) having end surfaces at least in the vicinity of said high-pressure end wall means (4); said high-pressure end wall means (4) including: means defining a space (16) which is in communication with said compressor inlet (12) through a channel (12'); and a movable wall plate means (14) which, in an active compression state of the compressor, is in sealing abutment with said end surfaces of said casing wall means (2) and which, for the purpose of deactivating the compressor, is movable in the axial direction of the compressor in said space (16) in said high-pressure end wall means so as to communicate said compression chambers (5, 6) with said compressor inlet (12) through said space (16) and said channel (12'); auxiliary drive means (20) coupled to said movable wall plate means (14) for selectively moving said wall plate means (14) in said axial direction of the compressor; said rotors (7, 8) being coupled with respective journals (11) via their respective bearing shafts (9, 10) solely at the low-pressure end of the compressor; said movable wall plate means (14) having a sealing surface facing said end surfaces of said casing wall means (2), said sealing surface being imperforate and extending sealingly across said compression chambers; oil injecting means (22, 23) for injecting oil into said compression chambers (5, 6); and valve means (24) coupled to said oil injection means for throttling or interrupting a flow of oil to said compressor chambers when said movable wall plate means (14) is in its compressor deactivating position; said valve means (24) being coupled to said movable wall plate means (14), and said valve means (24) being operable to a position for throttling or interrupting said flow of oil to said compression chambers responsive to movement of said movable wall plate means (14) to a position out of sealing abutment with said end surfaces of said casing wall means.