Abstract: A gas cylinder valve for high pressure gas cylinders includes a pneumatic actuator with tandem pistons which are operated by normal industry "house" pneumatic pressures to overcome the large closing bias force generated by a set of disc springs so that the valve opening spring can lift the valve stem from its seat. A floating pressure plate which seats against an annular internal shoulder in the actuator housing prevents pneumatic pressure applied to the upper piston from acting on the back of the lower piston. Pneumatic pressure from a common source is applied to both pistons through an axial hole in a piston rod integral with one piston and bearing against the other piston. The actuator is easily assembled by merely inserting the lower piston, the pressure plate, the upper piston and the disc springs into the open end of a cup-shaped housing, and securing them in place with a preload on the springs by screwing on a housing cover.

Abstract: 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.