Frick Company

Peter C Spellar

David A Murphy

Paul Nemit, Jr

Joseph W Pillis

An axial flow helical screw compressor with a slide valve and slide stop mounted end to end in communication with the intermeshing rotors has means for changing the volume ratio during operation by stepwise movement of the slide stop and for changing the capacity during operation in infinitely variable fashion, both in response to system operating conditions. In the event of interference between the movements of the slide stop and slide valve, the components are designed so that the movements of the slide stop overpowers that of the slide valve.

Variable volume ratio screw compressor with step control

A method of operating an electric drive motor for an axial flow helical screw type compressor having a slide valve member and slide stop member mounted beneath the intermeshing rotors such that the slide member controls communication between the work chamber defined by the rotors and the casing to the outlet port and the slide stop member and the valve member together control the working fluid inlet to the bores of the rotor by sensing the drive motor current and full load operation of the compressor in order to incrementally adjust the slide members in opposite directions depending upon whether or not the motor current is increasing or decreasing to thereby continuously seek the position of the slide members at which such current is at a minimum.

Micro-processor control of compression ratio at full load in a helical

An axial flow helical screw type compressor has a slide valve member and slide stop member mounted end to end beneath the intermeshing rotors such that the slide valve member controls communication between the work chamber defined by the rotors and the casing to the outlet port and the slide stop member and the valve member together control the working fluid inlet to the bores of the rotors, the slide valve member and the slide stop being independently movable. Control means for the slide valve member and slide stop include position sensing means for these two members, inlet and outlet pressure sensing means, and means for feeding these inputs into programmable circuitry to control the positions of the slide member and slide stop. Additional control means senses the occurrence of full load operation and then causes the slide valve member and slide stop member to move as a closed unit in a given direction, or the reverse, as the compressor drive motor current is sensed, continuously seeking the position at which such current is at a minimum.

An axial flow helical screw type compressor has a slide valve member and a slide stop member mounted end to end beneath the intermeshing rotors such that the slide valve member controls communication between the work chamber defined by the rotors and the casing to the outlet port and the slide stop member and the valve member together control the working fluid inlet to the bores of the rotors, the slide valve member and the slide stop being independently movable. Control means for the slide valve member and slide stop include position sensing means for these two members, inlet and outlet pressure sensing means, and means for feeding these inputs into programmable circuitry to control the positions of the slide member and slide stop.

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Hagerstown, MD, United States of America

Peter C Spellar