Capacity control for rotary compressor

A rotary fluid compressor comprising a housing having a closed working chamber provided with a substantially cylindrical surface, said housing having an inlet port and an outlet port communicating with said chamber;

• a rotor mounted in said chamber and rotatable about an axis eccentric to the axis of said cylindrical surface, said rotor having contact with said cylindrical surface at one point on its periphery, and a plurality of vanes slidably supported in said rotor and engaging said cylindrical surface whereby when said rotor is rotated said vanes compress fluid from said inlet port to said outlet port providing a compression area within said chamber;
• and a control member rotatably mounted in said housing and provided with an elongated arcuate aperture in fluid contact with said working chamber and spanning at least one of said vanes to permit fluid to bypass the vanes and thereby change the compression area in said chamber, said control member being operative upon rotation thereof to vary the location of the aperture to vary the compression volume of said chamber to thereby vary the capacity of the compressor, and means to rotate said control member, said means comprising a hydraulic valve operatively connected to said control member and actuated by a diaphragm which is responsive to the suction pressure of the compressor.