High pressure shut-off valve

A high pressure shut-off valve comprising

• a hollow valve body having an open end, a closed end and a cylindrical cavity therein,
• cover means for said open end,
• aligned tubular inlet and outlet portions on opposite sides of said valve body defining a continuous straight bore intersecting said cavity at a right angle thereto,
• a plug valve assembly positioned in said cavity and comprising a first piston having a sliding fit in said cavity between an extended position abutting said closed end and a retracted position a predetermined distance therefrom,
• said first piston having an end portion with a laterally extending valve passage therethrough and an intermediate portion closing said valve body bore when in said extended position and said valve passage being aligned with said valve body bore when in said retracted position,
• said first piston being a hollow piston with a smooth cylindrical surface including said intermediate portion,
• said cylindrical surface having circular grooves in diametrically opposed positions defining cylindrical surface portions of a size closing said casing bore when in a retracted position,
• a plurality of holes interconnecting each of said circular grooves with the bore of said first piston,
• said intermediate portion being radially immovable, having a fixed radius and providing fixed surfaces of cylindrical configuration with a sliding fit in said cavity,
• a sealing member of elastomeric material, filling said circular grooves and said holes and including elastomeric material positioned in the bore of said first piston, cooperable with said first piston intermediate portion and movable relative thereto and engaging the entire circumferential wall of said cavity around said bore to seal the same against leakage when closed,
• operating means for moving said plug valve assembly between said extended and retracted positions and including means engageable with said sealing member in said extended position to compress the same longitudinally along said first piston to expand the same outward to seal against leakage of pressure around said radially immovable intermediate first piston portion, said engageable means comprising a second piston slidably movable inside first piston and movable, upon movement of said plug valve assembly to a closed position, to a position engaging and compressing the portion of said elastomeric material in said first piston bore to apply substantially uniform pressure of said elastomeric material in said circular grooves against the surface of said valve cavity to seal around said valve cavity bore.