US 4,185,955 AGranted

Apparatus for replicating centrally apertured video disc records

AssigneeMCA Disco-Vision, Inc.

InventorsJohn R. Holmes, Roy G. Jordan

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Abstract

Heated material is injected into an annular cavity, defined by a pair of mold halves, through a sprue passage, defined by a sprue bushing and an end portion of a punch. The annular cavity and the sprue passage form, respectively, the centrally apertured part and a sprue. After partial cooling of the heated material, the punch is locked in place while the annular cavity is displaced relative to the sprue passage so that the sprue is severed from the part along the peripheral surface of the punch end portion. The mold halves are separated to open the annular cavity while the sprue is resting on the punch end portion, and while the part is held by the punch end peripheral surface. After the mold halves are separated, a sprue ejector member is actuated to eject the sprue from the punch end portion. The finished video disc is then removed, carried by the moving platen of the moving mold assembly.

Claims2

Dependent claims

In apparatus, for injection molding an article having a central aperture, having an injection nozzle for injecting a molten mixture into an annular cavity of uniform thickness formed by a first mold half and a second mold half, said injection gate being positioned intermediate the injection nozzle and the cavity, an injection gate comprising:

a sprue passage of substantially circular cross-section and having a first end and a second end, and said first end being adapted to contact the injection nozzle and to receive a molten mixture exciting the injection nozzle;
an annular shaped gate passage having a first end and a second end, and being formed by a plurality of concentric annular shaped sections positioned intermediate said second end of said sprue passage and said cavity;
each of said sections having a different average thickness for regulating the pressure of the molten mixture as the mixture passes therethrough prior to entering the cavity;
and
said first end of said gate passage having a greater thickness than the second end of said gate passage for providing restriction to the passage of the molten material through said gate passage and for achieving a minimum disturbance to material flow of the molten material as it flows through said gate passage.

2 more elements

Dependencies are inferred from the claim text.

Facts

Application: 05/918,894Filed 26 Jun 1978 · division
Priority: 31 Oct 1977
Granted: 29 Jan 1980
Term ends: Not estimatedThe source records don’t support an estimate.

Classification7 codes

B29C 45/2701
Sprue channels ; Runner channels or runner nozzles: details not specific to hot or cold runner channels
B29C 45/263
Moulds: with mould wall parts provided with fine grooves or impressions, e.g. for record discs
B29C 45/38
Component parts, details or accessories; Auxiliary operations: cutting-off equipment for sprues or ingates
B29C 2045/2653
With mould wall parts provided with fine grooves or impressions, e.g. for record discs: using two stampers