Plastic article or earthenware shaping or treating: apparatus – Female mold and charger to supply fluent stock under... – With means to heat or cool
Patent
1982-07-19
1984-02-28
Pavelko, Thomas P.
Plastic article or earthenware shaping or treating: apparatus
Female mold and charger to supply fluent stock under...
With means to heat or cool
425549, 425566, B29F 103
Patent
active
044339690
ABSTRACT:
This invention relates to an improved valve pin bushing for use in a multi-cavity valve gated injection molding system and a method of manufacture. Each valve pin bushing has a main body portion which is positioned between the end of a manifold plate arm and the heated nozzle, and a collar portion which projects from the main body portion with clearance beyond the end of the manifold plate arm. The melt passage 34 extending through the manifold plate joins a melt duct extending diagonally through the main body portion and the valve pin is snugly received in a bore in the bushing. The bore has an enlarged portion which receives the melt from the diagonal duct which then flows through the heated nozzle around the valve pin. The valve pin bushing has a peripheral flange which laterally locates it in the cavity plate to offset frictional forces from thermal expansion of the manifold plate. The valve pin bore is interrupted by a circumferential opening in the collar portion which vents corrosive gases through a vent duct in the main body portion. The valve pin bushing is manufactured by first separately machining and drilling the main body and collar portions to form the circumferential opening, vent duct, diagonal melt duct and bolt holes. The collar portion is then brazed to the main body portion in a vacuum furnace to form an integral unit which is then centrally drilled to provide the valve pin bore. In addition to improving lateral location, this structure provides the necessary length of snugly fitting bore around the valve pin to adequately seal against leakage of the pressurized melt during operation.
REFERENCES:
patent: 4026518 (1977-05-01), Gellert
patent: 4380426 (1983-04-01), Wiles
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