Patent ID: 7234680

Claim:
An apparatus for regulating the flow of a gas between a high-pressure zone and a zone of lower pressure, said apparatus comprising: a hollow body having an axis; a first chamber and a second chamber, said chambers defined within said body; a nozzle within said body and separating said chambers, said nozzle defining a passage for the passage of gas between said chambers; and a stem movable axially within said passage, extending at least partially into said first chamber, wherein axial movement of said stem varies the position of said stem in relation to said nozzle, said stem comprising: an o-ring seat disposed in an annular pocket on said stem and contactable with said nozzle to seal said passage against the passage of gas; a distal stem portion extending at least partially into said first chamber and a proximate stem portion within said second chamber and extending into said passage, said distal stem portion connectable to said proximate stem portion to squeeze at least part of said o-ring there-between; and an axial duct defined in said stem for venting said gas into an interior portion of said pocket; wherein said axial duct comprises a central duct in said proximate stem portion in linear registration, and fluid communication, with a central duct in said distal stem portion.