Valve seat structure having pressureactuated seal means

Claim 1

AN ANNULAR METALLIC SEAT MEMBER ADAPTED TO BE MOVABLY DISPOSED IN THE SEAT RECESS OF A VALVE HAVING A RECIPROCATING GATE PROVIDED WITH PLANAR SEALING SURFACES, SAID SEAT MEMBER HAVING AN ANNULAR SUBSTANTIALLY PLANAR SEALING FACE AND AN ANNULAR GROOVE FORMED IN THE SEALING FACE INTERMEDIATE THE INNER AND OUTER PERIPHERIES OF THE SEALING FACE, A DEFORMABLE PLASTIC SEALING MEMBER HAVING A RELATIVELY LOW MODULUS OF ELASTICITY POSITIONED IN SAID GROOVE AND HAVING A PORTION THEREOF EXTENDING BEYOND THE PLANE OF SAID SEALING FACE FOR ENGAGEMENT WITH A SEALING SURFACE OF THE GATE, AN ANNULAR RESILIENT SEALING MEMBER HAVING A RELATIVELY HIGH MODULUS OF ELASTICITY FIXED TO THE SEAT MEMBER IN CONCENTRIC RELATION TO SAID PLASTIC SEALING MEMBER AND HAVING A PORTION THEREOF EXTENDING BEYOND SAID PLASTIC SEALING MEMBER, WHEREBY UNDER LOW LINE PRESSURE CONDITIONS SAID RESILIENT SEALING MEMBER WILL BE IN SEALING ENGAGEMENT WITH THE GATE AND THE PLASTIC SEALING MEMBER WILL BE SPACED FROM THE GATE, UNDER HIGH LINE PRESSURE CONDITIONS BOTH SAID PLASTIC AND RESILIENT SEALING MEMBERS WILL BE IN SEALING ENGAGEMENT WITH THE GATE.