Apparatus and method for multi-layer injection molding

In combination with a nozzle and a separate melt passage of an injection molding apparatus, a unitary flow control valve member positioned in a central bore and comprising:

• a first portion for allowing flow of material transversely across the flow control valve member and through the melt passage;
• a second portion for restricting flow of material through the melt passage;
• and
• a third portion for restricting flow of material out of the nozzle;
• wherein the flow control valve member divides the melt passage into a first section and a second section, the first portion allowing flow of material from the first section to the second section, the second portion restricting flow of material from the first section to the second section and from the second section to the first section;
• wherein the melt passage is in connection with a melt channel;
• and
• wherein the central bore defines a portion of the melt channel and has a uniform diameter upstream of the melt channel.

A method for injection molding comprising the steps of:

• injecting a first material into a first melt passage having a first section and a second section;
• positioning a unitary valve pin in a central bore;
• positioning a first portion of the valve pin between the first and second sections to allow flow of the first material transversely across the valve pin through the first melt passage;
• positioning a second portion of the valve pin between the first and second sections to restrict flow of the first material through the first melt passage;
• and
• positioning a third portion of the valve pin in an opening of a nozzle to restrict flow of the first material out of the nozzle;
• wherein the central bore defines a portion of a melt channel and has a uniform diameter upstream of the melt channel.

An injection molding apparatus comprising:

• a manifold having at least a portion of a first melt passage;
• a nozzle having a melt channel in connection with the first melt passage;
• a cavity aligned with the melt channel of the nozzle;
• and
• a unitary valve member positioned in a central bore and having a first portion for allowing flow of material transversely across the valve member and through the first melt passage, a second portion for restricting flow of material through the first melt passage, and a third portion for restricting flow of material from the melt channel into the cavity;
• wherein the valve member passes through and divides the first melt passage into a first section and a second section in connection with the melt channel, the second portion of the valve member restricting flow of material between the first and second sections of the first melt passage;
• and
• wherein the central bore defines a portion of the melt channel and has a uniform diameter upstream of the melt channel.