Pneumatically operated valve with manual override and lockout

摘要

A gas cylinder valve with an inner valve stem biased toward a valve open position by a helical compression spring is pneumatically operated by an actuator having a piston biased by a stack of disc springs against an outer valve stem, separated from the inner valve stem by a diaphragm gas seal, to urge the inner valve stem to a valve closed position. While the force exerted on the inner valve stem by the disc springs exceeds that applied by the helical spring so that the valve is normally biased closed, pneumatic pressure applied to the piston moves the piston away from the outer valve member so that the helical spring moves the inner valve stem to the open position. The valve may be manually opened without pneumatic pressure by screwing a threaded shaft into a boss on the piston, and while holding the shaft stationary with a handle provided, rotating a nut wrench threaded onto the shaft which bears against the actuator housing to draw the piston away from the outer valve stem against the bias of the spring discs so that the helical spring can move the inner valve stem to the open position. The valve is locked closed by a threaded plug which screws into the actuator housing and clamps the piston down against the outer valve stem with the inner valve stem in the closed position. The manually operable pneumatic actuator can be easily retrofitted to existing gas cylinder valves or can be provided as a part of new valves, and is of a size which permits it to be enclosed for transportation and storage by a conventional transport cap.