Valve disc and drive shaft assembly

摘要

A butterfly valve disc (10) has a circular cross-section bore (26) for receiving the end of a drive shaft (16) which engages with a member (20) non-rotatably located in the bore (26). The member (20) is polygonal and preferably formed with twelve sides (75) and edges (70), the edges (70) biting into the internal surface of the bore (26) to prevent rotation. The member (20) preferably is of harder alloy than the disc (10) to resist wearing and is formed with a slot (30) extending perpendicularly to the plane of the disc (10) to receive a corresponding tongue (36) formed at the end of the shaft (16). This arrangement allows a small degree of play so that if the disc (10) is subjected to pressure on one side and therefore bends, the torque required to open the valve is not increased. Alternatively wherein the disc (10) (or another component) is not subject to such pressure the member (20) may be integrally formed with the shaft (16).