Ball valve

Claim 1

A valve comprising a valve body having an inlet and outlet flow passages and a valve chamber communicating with the inlet and outlet flow passages, said valve chamber having a generally cylindrical outer wall meeting an annular end wall around said inlet and outlet flow passages, a centrally bored flow control ball rotatably disposed within said chamber and being movable under the force of fluid pressUre thereon, said ball having thereon a generally spherical external surface, said valve body defining a radial bore extending outwardly from said central bore in alignment with said ball, means for rotating said ball between said valve open and valve closed positions thereof including an operating member operatively connected to said ball and extending outwardly from said valve chamber, two annular valve seats formed of yieldable polymeric material and disposed in encircling relation to the inner ends of said respective flow passages, and two annular seat carriers disposed in encircling relation around said respective valve seats, said carriers being contiguous with the wall of said valve chamber and encircling the inner ends of said respective flow passages; characterized 1. by each said valve seat having an annular sealing surface having in radial section a concave curvature and confronting said ball to seal thereagainst, the curvature of each said valve seat being smaller than the radius of the curvature of said ball such that interference loading of each said valve seat is accomplished on assembly, each said seat surface closely approximating a spiral; 2. by each of said seat carriers comprising a first annular support member engaging its respective valve seat and containing said valve seat against radial expansion, and a second annular support member extending radially inward along the radial side of its respective valve seat opposite from said ball to sustain the outward portion of said valve seat against the axial force of said ball, the radially inward portion of said valve seat and the adjacent portion of said second annular support member normally being spaced somewhat from each other when said valve seat is in an unstressed condition to provide a clearance space between the radially inward portion of the radially outward side of said valve seat and said second member which allows clearance for dynamic displacement of said valve seat when said valve is in operation; and, 3. by a plurality of spaced radial apertures through said first annular support member of said seat carriers; whereby when said ball is rotated from said valve closed position to said valve opened position, introducing momentary throttling at high differential, said upstream valve seat deflects minutely against said second member of its respective seat carrier, opening said apertures in said first member of its respective seat carrier to said valve chamber so as to vent the pressure differential without causing a blow-out of said upstream valve seat from said seat carrier.