Metal seat butterfly valve

Claim 1

A butterfly valve comprising a valve housing with a flow channel passing therethrough, a valve disc rotatably mounted in said housing with a sealing surface circumscribing the periphery of said disc, said sealing surface being a portion of a converging surface, a metal annular seat means disposed to cooperate with said sealing surface to interrupt flow through said valve when said disc is rotated into the closed position, said seat means having a lip portion, a heel portion and a linking seat portion joining said lip portion to said heel portion, said valve housing having a recess adapted to receive a seat retaining means such that a seat receiving groove is formed between facing surfaces of said recess and said retaining means, one of said facing surfaces, when viewed in cross section, having lug means projecting toward the other of said facing surfaces, said seat means being positioned in said groove such that said heel portion of said seat is gripped in a fluid tight relationship between portions of said facing surfaces and said lug means contacts said heel portion to lock said heel portion against movement in said groove, said lip portion extending into said flow channel in the same direction as said converging surface and positioned to be preloaded against said conVerging surface when said valve is closed and being capable of flexure under the influence of temperature and pressure induced forces, and said lug means having that portion that is closest to said other of said facing surfaces being spaced from said seat to further facilitate flexure of said lip.