Dual piston pneumatically operated valve.

摘要

A gas cylinder valve for high pressure gas cylinders includes a pneumatic actuator (41) with tandem pistons (55, 59) which can be operated by normal industry "house" pneumatic pressures to overcome the large closing bias force generated by a set of disc springs (89) and thus to allow a valve opening spring (25) to lift a valve stem (19) from its seat (23). A floating pressure plate (61) which seats against an annular internal shoulder (65) in the actuator housing (43) prevents pneumatic pressure applied to the underside of the upper piston (59) from acting on the top of the lower piston (55). In order to open the valve, compressed air or nitrogen is supplied through a fitting (97) to a chamber (57) beneath the piston (55) and, through an axial hole in a piston rod (67) integral with piston (55) and bearing against the other piston (59), to a chamber (63) below the piston (59). The actuator is easily assembled by merely inserting the lower piston (55), the pressure plate (61), the upper piston (59) and the disc springs (89) into the open end of a cup-shaped housing (43), and securing them in place with a preload on the springs (89) by screwing on a housing cover (95).