Abstract: A valve comprising a substantially cylindrical housing, a substantially annular cylindrical resilient valve seating member in said housing, said seating member having an inner surface and an outer surface, a butterfly valve having an outer periphery, a shaft extending through the housing and the seating member for mounting the butterfly valve for movement between a first position wherein its outer periphery is in engagement with the inner surface of the seating member and an open position wherein the outer periphery of the butterfly valve is spaced from the inner surface, a plurality of ribs on the outer surface of the valve seating member for bearing against the inner surface of the housing, chambers between the ribs, a plurality of openings in the valve seating member upstream of the butterfly valve for permitting pressurized fluid to enter the chambers to thereby tend to move the resilient valve seating member radially inwardly into engagement with the outer periphery of the butterfly valve when the latter

Abstract: A valve comprising a substantially cylindrical housing, a substantially annular cylindrical resilient valve seating member in said housing, said seating member having an inner surface and an outer surface, a butterfly valve having an outer periphery, a shaft extending through the housing and the seating member for mounting the butterfly valve for movement between a first position wherein its outer periphery is in engagement with the inner surface of the seating member and an open position wherein the outer periphery of the valve is spaced from the inner surface, an annular chamber between the outer surface of the valve seating member and the housing, a plurality of apertures in the valve seating member upstream of the butterfly valve for permitting pressurized fluid to enter the chamber to thereby tend to move the resilient valve seating member radially inwardly into engagement with the outer periphery of the butterfly valve when the latter is in a closed position.