Fluid control valves

Claim 1

A fluid control valve comprising a smooth annular seat member defining a fluid flow passageway therethrough, and a disc shaped in plan view to correspond with the radially inner portion of a transverse section of said seat member for movement about an axis through the seat member and disc to and from a position in which the disc closes said passageway, said axis defining smaller and larger disc portions on opposite sides thereof wherein the mass of said disc is substantially balanced about said pivotal axis, said disc having a non-symmetrical aerofoil cross-sectional shaping in a direction perpendicular to said axis to define leading and trailing edges respectively located in said smaller and larger disc portions, said aerofoil shaping of said disc includinG a concave surface on one side of said disc and a convex surface on the other side thereof, and said shaping defining respective centers of pressure which are both located in said larger portion of said disc in respect to fluid flow in opposite directions through said shaping, said shaping rendering said disc self-stabilized in its open position.