PLASTICS BUTTERFLY VALVE

摘要

The invention relates to a valve assembly having a moulded polyethylene valve body (12) having a conduit portion (14) and an annular portion (16) extending upwardly from the conduit portion (14), a passageway (18) extending through the conduit portion (14) for the conveyance of fluid. A valve seat (24) is formed in the conduit portion (14) and comprises a metal sleeve (46) that is moulded in the valve body (12) to prevent separation of the sleeve (46) from the valve body (12) during sustained pressures. O-rings (45, 47) are positioned in grooves (41, 43) around the metal sleeve (46) and are compressed by the plastics material during the moulding process to effect a seal between the sleeve (46) and the plastics valve body (12). An annular rubber sleeve insert (53) is vulcanized onto the inner diameter portion of the metal sleeve (46). A plastics valve disc (26) is centrally positioned in the conduit portion (14) within the periphery of the rubber sleeve insert (53) and is arranged to sealingly engage the rubber sleeve insert (53) when the valve is moved to the closed position. A metal stem (28) extends through the annular portion (16) of the valve body (12) and is connected to the valve disc (26). The upper end of the metal valve stem (28) is moulded into an actuator (30). The actuator (30) is sealingly connected to the annular portion (16) of the valve body (12) so as to maintain the actuator (30) on the valve body (12) in the event that the pressure seal between the valve disc (26) and the valve body (12) is destroyed.