Method for making an elastomeric annular seal with enclosed garter spring

Abstract

Abstract A mold assembly including an externally-tapered lower core member with an annular groove near the top and an annular shoulder and seat near the bottom and an internally-tapered upper cavity mold member cooperatively form an annular die cavity having the shape desired for the elastomeric annular seal to be formed therein. Prior to molding the seal, the upper cavity mold member is retracted and moved out of alignment with the core member and replaced temporarily by a cylindrical loading device having an annular groove for receiving a pre-tensioned annular hollow helical tension spring and below it a cylindrical end portion adapted to receive an annular charge of elastomer. In carrying out the method of this invention, an annular mounting case is placed on the seat and a collar on the loading device is moved downward so as to push the annular hollow helical tension spring and the annular elastomeric charge from the loading device onto the core member until the spring snaps into the annular groove of the latter. The loading device is then retracted and moved out of alignment with the core member and the mold cavity member moved into alignment therewith and then moved downward into telescoping relationship with the core member, moving the annular hollow helical tension spring downward and at the same time expanding and circumferentially stretching it to open up spaces between its convolutions. As the spring is pushed downward, it pushes the elastomeric charge ahead of it into the mold chamber which shapes the seal and totally encloses the spring therein. Excess elastomer is ejected upward through the clearance between the mold and core members. Simultaneously therewith, the elastomer is pushed between the now-spaced convolutions of the expanded spring into the hollow of the spring, completely and uniformly filling it with elastomer. The upper mold cavity is then moved downward to the end of its stroke and an annular nose portion thereof cooperates with the shoulder as a fulcrum to bend the periphery of the case upward into a frusto-conical flange which enters the mold chamber and becomes bonded to elastomer flowing against its opposite sides. The end of the stroke ordinarily cuts off any flash adhering to the upper end of the seal, forming a sharp sealing lip thereon. The elastomer of the seal is then cured in the mold cavity by heating the mold assembly, after which the completed seal is ejected from the core member by a conventional stripper as the mold cavity member is retracted upward.

Inventors

• 👤 Michael J Burke

Bibliographic Details