Abstract: A gas compressor has cylinders in which gas is compressed by pistons. Each cylinder has a suction valve and an exhaust valve to admit uncompressed gas and expel compressed gas. The suction valve includes a suction valve plate which repeatedly moves toward and away from the top end of the cylinder between closed and open positions, respectively. Apparatus to control compressor capacity includes an unloader mechanism to selectively prevent the suction valve plate moving to fully closed position to thereby unload the cylinder and reduce compressor capacity. The unloader mechanism comprises an unloader piston movable in an unloader cylinder in response to system conditions to move a linkage which determines the closure position of the suction valve plate. The linkage includes a pivotable lift arm biased toward a position which allows full closure of the suction valve plate and is movable by the unloader piston to another position which prevents full closure of the suction valve plate.

Abstract: A large manually operated leak-proof corrosion-proof low-cost shut-off or stop valve for handling high pressure refrigerant liquids and/or gases comprises a valve body formed of two sheet metal hemispheres welded to the periphery of a circular metal valve plate having a fluid passage therethrough and hollow cylindrical metal tubes welded to the hemispheres along the edges of circular holes cut in the hemispheres. One tube on each hemisphere serves for fluid flow. Another internally and externally threaded tube on one hemisphere serves as a valve sleeve through which a rotatable and axially shiftable externally threaded valve spindle extends. The cylindrical inner end of the valve spindle extends into a cylindrical recess in a valve disc which releasably engages a valve seat around a fluid flow passage in the valve plate.