Capacity control for rotary vane compressor

Claim 1

A control arrangement for a rotary vane fluid displacement apparatus including a fluid control valve, which valve comprises a valve housing having a longitudinal reference axis and defining a first end and a second end, a first or slide chamber and sidewall, a second or bellows chamber and a connecting channel between said first and second chambers; said valve housing being sealed at said first end by a plug defining a stub-stop protruding into said first chamber along said reference axis, said second chamber being sealed at said housing second end by a seal means and an adjustable threaded plug; a slide, coaxial with said longitudinal reference axis, and slidably operable in said first chamber defining a first land, a second land and a third land with a first and second cylindrical segments and groove segments, respectively, therebetween; said valve housing first end, slide valve bore sidewall and first land of said slide cooperating to define a bias spring chamber therebetween; said slide further defining a protuberance extending into said spring chamber from said first land longitudinally toward said stub-stop; a bias spring positioned in said spring chamber between said first end of said valve housing and said first land to bias said slide; an expandable bellows mounted in said second chamber contacting said threaded plug and including an extension member with a protruding head end extending into said connecting channel and slidable therein by said bellows; said valve housing further defining a discharge port, a suction pressure port, a compression chamber port and a valve control port which communicate, in that order, between said first chamber and a pressure operable device, a source of suction pressure, said second inlet connecting means and said fluid displacement control cavity; said valve housing further defining an annulus in said connecting channel and a first passage means communicating between said discharge port and said annulus; said bellows extension member defining a through-hole alignable with said annulus of said connecting channel when said bellows is compressed; said bellows extension member further defining a longitudinal passage means communicating between said extension member head end and said extension member through-hole; said slide defining a cross-hole in said second cylindrical segment and a bore passage means communicating between said cross-hole and said spring chamber; and wherein said fluid control valve is operable to communicate discharge or suction pressure to said control cavity in response to the differential between said discharge and suction pressures when such differential is great enough to overcome the bias force of said spring to thus provide a means to transfer discharge pressure from said valve control port to said compression chamber port and to simultaneously introduce suction pressure to said valve control port.