Isolation chamber valve

Claim 1

In an isolation chamber valve for use with pressurized fluids and having a main first valve member, a fluid bypass circuit connected between an inlet and outlet of the first valve member comprising: a normally closed second valve element located in a fluid line of small cross sections, said second valve element comprising a ball and a seat for said ball; valve operating means for selectably opening the second valve element to allow fluid flow through the bypass circuit, thereby equalizing pressure across the inlet and outlet, said valve operating means comprising a push rod adapted to move said ball from its seat, a piston member contacting said push rod and having a helical groove formed therein which is coaxial with the push rod, and a cylindrical housing having internal pin means for engaging said groove and converting rotational motion of said piston to translational motion of said push rod and said ball; and means located in the fluid line for controlling the flow therethrough.