Pressure relief valve and method of manufacturing the same

Abstract

A pressure relief valve such as is used to relieve over-pressure in the passenger compartment of an automotive vehicle has valve flaps which are retained in connection with a housing by molded-in-place retainer strips. The valve is manufactured by an injection molding tool having a pair of mold halves defining a first mold cavity for forming the housing and a second mold cavity for forming the flaps. After the housing and flaps have set, the mold is opened, with the housing remaining in contact with one mold half and the flaps remaining in contact with the other mold half. One mold half is then moved relative to the other to place the housing and the flaps in alignment with one another, and the mold halves are closed again to place the flaps inside the housing and define a third mold cavity extending along the lines of desired attachment between the flaps and the valve seats. A third quantity of thermoplastic material is injected into the third mold cavity where it sets to form the retainer strips, bonding with the edges of the flap and the adjacent edges of the valve seat. The third mold cavity also extends around a peripheral flange surrounding the housing, forming a seal which is bonded to the housing. The part is complete when ejected from the mold, with no additional assembly required.