Dunham-Bush

Joseph S Orosz

Donald D Schaefer

Anthony J Bianco

A large slide valve member concentrically mounts a small slide valve member or slide stop at one end thereof proximate to a helical screw rotary compressor discharge port with the small and large slide valve members movable as a unit for varying the built in volume ratio of the compressor. The small slide valve member is shiftable independently of the large slide valve member to vary the capacity of the machine. A large diameter cylinder fixedly mounted to the end of the compressor casing remote from an outlet port slidably mounts interiorly a smaller diameter cylinder fixed to the large slide valve via a spindle. The small slide valve is fixed to one end of a piston rod which extends through a bore within the large slide valve member and the spindle and terminates internally of the small diameter sliding inner cylinder and has fixed thereto a piston. Hydraulic fluid supplied to one side of the piston and removed from the other side shifts the small slide valve independent of the position of the large slide valve member. A stepping motor fixed to the outer cylinder has an output shaft fixed to an elongated ball screw mounted for rotation with its axis parallel to the concentric inner and outer cylinders and a cylindrical ball nut concentrically positioned on the ball screw, is flange connected through a slot opening within the side of the fixed outer cylinder, to the outer periphery of the inner cylinder. Bearing balls positioned between opposing screw threads of the ball screw and the ball nut move through a circulating loop such that the inner cylinder and thus the slide stop and the large slide valve member is driven bidirectionally, incremented by the stepping motor.

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Storrs, CT, United States of America

Joseph S Orosz