Rotary cock with generally spherical valve member

Claim 1

A ball valve comprising: a housing formed with an inlet at an upstream side and an outlet at a downstream side, said inlet and outlet defining a flow cross section; a generally spherical main valve member formed with a passage substantially equal in cross section to said flow cross section and being rotatable in said housing about an axis transverse to said passage between open and closed positions; a downstream valve seat in said housing engageable with said member between said member and said outlet; an upstream valve seat movably mounted in said housing between said inlet and said valve member, a deflectable annular metallic lip being formed on one of said valve member and said upstream valve seat and being deflectable in said closed position of said member by fluid pressure applied to said upstream valve seat to seal between said upstream valve seat and said valve member; a flexible metal element having one side connected to said housing and another side connected to said upstream valve seat for applying fluid pressure at said upstream side to said upstream valve seat in the direction of said valve member to generate a sealing force between said upstream valve seat and said valve member; and means for equilibrating pressure on opposite sides of said upstream valve seat for relieving said force prior to shifting of said valve member to said open position.