Hot sprue valve assembly for an injection molding machine

Claim 1

In an injection molding machine for producing centrally apertured record discs, said machine including a generally disc-shaped mold cavity and a sprue bushing for flow of molten disc-forming material into the mold cavity, a method of controlling flow of the disc-forming material into the mold cavity comprising the steps of: positioning a poppet valve generally at the end of the sprue bushing adjacent the mold cavity; biasing the poppet valve to a normal closed position seated upon the adjacent end of the sprue bushing to prevent flow of the molten disc-forming material from the sprue bushing into the mold cavity; injecting molten disc-forming material into the sprue bushing at a pressure sufficient to force the poppet valve to move generally across the mold cavity to an open position spaced from the sprue bushing to allow flow of the molten disc-forming material through the sprue bushing into the mold cavity; returning the poppet valve to its closed position by advancing a ram on the side of the mold cavity opposite the sprue bushing into bearing engagement with the poppet valve; allowing the disc-forming material in the mold cavity to solidify; and ejecting the solidified molded disc from the mold cavity.