Apparatus for preventing thermal damage to a preformed plug during molding of a housing therearound

摘要

A rotary plug valve which is of the type comprising a housing formed of a polymer and a rotary plug disposed in a through-passage of the housing. The plug is formed of a polymer and includes a bore selectively alignable with the through-passage to admit the passage of fluid. The plug valve is formed by forming the plug and attaching thereto a preformed polymeric shield by snap-fitting the shield onto the plug. The shield has an inner surface conforming to the periphery of the plug. The plug and shield assembly is positioned within a cavity of a mold. The cavity corresponds to the shape of the housing. A molten polymer is introduced into the cavity and intimately contacts the shield and forms the housing around the plug.