# US 4,391,579 A · Hot sprue valve assembly for an injection molding machine

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- Number: US 4,391,579 A
- Document ID: US4391579A
- Status: Granted
- Kind: A
- Application number: 06/304,421
- Filed: 1981-09-23
- Granted: 1983-07-05
- Earliest claimed: 1981-09-23
- Assignees: Discovision Associates
- Inventors: Rocky V. Morrison
- Web page: https://patentgrep.com/patent/US4391579A

## CPC

- B29C 45/2896: {extending in or through the mould cavity, e.g. valves mounted opposite the sprue channel}
- B29C 45/263: {with mould wall parts provided with fine grooves or impressions, e.g. for record discs}
- B29C 2045/2653: {using two stampers}
- Y10S 425/81: Sound record
- B29C: SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING (making preforms B29B11/00; making laminated products by combining previously unconnected layers which become one product whose layers will remain together B32B37/00 - B32B41/00)
- Y10S: TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS

## Abstract

A hot sprue valve assembly is provided for controlling flow of molten material into the mold cavity of an injection molding machine. The valve assembly is particularly designed for use with an injection molding machine for molding centrally apertured record discs, such as video information discs. The valve assembly comprises a stationary valve body supporting a movable valve member for sliding motion toward and away from the mold cavity. The valve member includes a hot sprue bushing defining a heated flow path for passage of molten material toward the mold cavity, and a dispersion head carried by the bushing for directing the molten material to flow in a generally radially outward direction through gate passages with substantially uniform radial distribution into the mold cavity. In one position, the valve member is advanced into the mold cavity to align the gate passages with the mold cavity and thereby permit flow of the molten material into the mold cavity. The valve member is movable to retract the gate passages from alignment with the mold cavity to prevent flow of the molten material into the mold cavity. In this retracted position, a portion of the dispersion head remains within a central portion of the mold cavity to mold a central aperture into the disc prior to solidification of the molten material.

## Claims

### Claim 1

A mold assembly for an injection molding machine, comprising:
first and second mold halves movable toward each other to a closed position defining a disc-shaped mold cavity, and movable away from each other to an open position allowing a molded disc to be removed from said mold cavity;
a valve body mounted on said first mold half and having a central opening formed therein;
a valve member carried within the central opening for sliding movement toward and away from the mold cavity, said valve member including a sprue bushing having a central bore formed therein for passage of the material toward the mold cavity, and a dispersion head cooperating with said sprue bushing for defining an annular and radially outwardly open gate passage for flow of material from the bore into the mold cavity;
means for controlling movement of said valve member between a first position with said dispersion head advanced at least partially through the mold cavity and said gate passage aligned with the mold cavity for flow of the material into the mold cavity when said first and second mold halves are in said closed position, and a second position with said gate passage retracted from alignment with the mold cavity and said dispersion head positioned generally within the mold cavity to mold a central aperture into the disc prior to solidification of the material within the mold cavity while said first and second mold halves are still in said closed position; and
means defining a recess formed in said second mold half for receiving said dispersion head when said valve member is in said second position.

### Claim 2 (depends on 1)

The mold assembly of claim 1 including heater means for controlling the temperature of said valve member.

### Claim 3 (depends on 1)

The mold assembly of claim 1 wherein said means for moving said valve member comprises a spring for biasing said valve member toward said second position, said valve member being responsive to flow of the disc-forming material under pressure therethrough for movement to said first position.

### Claim 4 (depends on 1)

The mold assembly of claim 1 wherein said sprue bushing includes a generally conical face extending from said bore radially outwardly and axially toward the mold cavity, and wherein said dispersion head includes a generally conical face presented toward and spaced from said sprue bushing face, whereby said generally conical faces of said sprue bushing and said dispersion head cooperate to define said gate passage.

### Claim 5 (depends on 4)

The mold assembly of claim 4 including a plurality of circumferentially arranged spacer flights connected between said generally conical faces of said sprue bushing and said dispersion head, said spacer flights cooperating with said generally conical faces to define a plurality of radially outwardly open gate passages.

### Claim 6

In an injection molding machine for producing centrally apertured record discs, a valve assembly for controlling flow of molten disc-forming material into a disc-shaped mold cavity, comprising:
first and second mold halves movable toward each other to define the mold cavity and movable away from each other to allow a disc to be removed from the mold cavity;
a valve body secured to said first mold half and having a central opening formed therein;
a valve member carried within the central opening for sliding movement toward and away from the mold cavity, said valve member including a sprue bushing having a central bore formed therein for passage of the material toward the mold cavity, and a dispersion head cooperating with said sprue bushing for defining an annular and radially outwardly open gate passage for flow of material from the bore into the mold cavity;
means for controlling movement of said valve member between a first position with said dispersion head advanced at least partially through the mold cavity and said gate passage aligned with the mold cavity for flow of the material into the mold cavity, and a second position with said gate passage retracted from alignment with the mold cavity and said dispersion head positioned generally within the mold cavity to mold a central aperture into the disc prior to solidification of the material within the mold cavity; and
said second mold half including means for receiving said dispersion head when said valve member is in said second position.

### Claim 7 (depends on 6)

The valve assembly of claim 6 wherein said dispersion head includes a face presented at least partially in an axial direction toward the bore in said sprue bushing, and wherein said controlling means comprises a spring for urging said valve member toward said second position, said valve member being movable to said first position in response to the pressure of disc-forming material passing through the bore and bearing against said dispersion head face.