Butterfly valve

A valve comprising, a valve body, a passageway through said valve body, an annular valve seat position in and surrounding said passageway, a valve shaft rotatably mounted within said passageway on an axis located at right angles to the axis of said passageway, a valve closure member, and mounting means for mounting said valve closure member on said valve shaft adapted to move said valve closure member upon 90 .degree. of rotation of said valve shaft between an open position, a closed position in alignment with and spaced from said annular valve seat, and a seated position in which an annular surface of said valve seat, and a seated position in which an annular surface of said valve closure member engages said annular valve seat, said mounting means comprising a valve shaft passageway therein through which said valve shaft passes, and at least one cam chamber therein surrounding said valve shaft, and wherein said valve further comprises (a) a cam mounted on said valve shaft and rotatable therewith, said cam located in said cam chamber and said cam and said cam chamber being sized such that said cam engages said cam chamber upon rotation of said cam of 15.degree. or less to move said mounting means and said valve closure member linearly along the axis of said passageway between said closed and said seated positions, (b) spring biasing means mounted on said mounting means and engaging said cam adapted to bias said mounting means and valve closure member from said seated position away from said annular valve seat linearly along said axis of said passageway to said closed position and (c) rotational stop means adapted to provide engagement between said valve body and said valve closure member to prevent further rotation of said valve closure member when said valve closure member has been rotated to said closed position in alignment with said annular valve seat.