Importance

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Abstract

A helical screw rotary compressor or expander rotatably mounts intermeshed helical screw rotors within intersecting bores of a casing. An axially extending recess provided within the barrel portion of the casing in open communication with the bore bears a slide valve member whose inner face is complementary to the envelope of the casing. The slide valve member controls communication between the working chamber defined by the rotors and the casing to the outlet port and bears means at the end in communication with the outlet port for sensing the closed thread pressure adjacent to the end of the slide valve member closing off the outlet port. Comparison of that closed thread pressure to the outlet port pressure permits controlled shifting of the slide valve member to prevent overcompression and undercompression, when the unit acts as a compressor, or underexpansion or overexpansion when the unit acts as an expander. The slide valve member carries a bore parallel to its longitudinal axis which bears a cylindrical volume capacity control valve body which shifts to vary flow through axially spaced channels, selectively communicating the working fluid inlet to the bores bearing the intermeshed helical screw rotors. The slide valve member and the volume capacity control valve body carried thereby are independently movable.

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First Claim