Injection molding core ring gate system

Claim 2

In an injection molding system for filling a cavity defined between a cool cavity plate and a cool movable mold platen with an opening therethrough, an elongated valve pin with a tip end which extends through a gate leading to the cavity, through the cavity, and into a bore in the movable mold platen, the gate, the opening through the cavity, and the bore in the movable mold platen being in alignment and substantially equal in diameter, valve pin actuating mechanism which reciprocates the valve pin between a rearward closed position and a forward open position in which the valve pin extends further through the opening through the cavity, a melt passage which extends through a manifold and around the valve pin to convey pressurized melt from a molding machine to the gate, the valve bin having an elongated head portion adjacent the tip end which extends from a reduced neck portion, the head portion being substantially equal in diameter to the gate, the opening through the cavity, and the bore in the movable mold platen, the reduced neck portion extending past the gate in the open position to provide for the flow of pressurized melt into the cavity, the improvement wherein the gate extends through a land in the cooled cavity plate and the head portion of the valve pin extends a considerable distance through the cavity into the bore in the movable mold platen, whereby in the retracted closed position contact between the head portion of the valve pin and the surrounding land of the cool cavity plate provides thermal separation between the hot neck portion of the valve pin and the head portion of the valve pin extending through the cavity, and sufficient contact is provided between the movable mold platen and head portion of the valve pin received in said bore to rapidly cool the melt surrounding the valve pin in the cavity.

Claim 3

A system as claimed in claim 1 wherein the valve pin is formed of steel.

Claim 4

A system as claimed in claim 1 wherein the head portion of the valve pin has a hollow portion adjacent the neck portion thereof.

Claim 5

A system as claimed in claim 3 wherein the head portion of the valve pin has a central portion extending between the hollow portion and the tip end formed of a highly conductive metal.

Claim 6

A system as claimed in claim 4 wherein the highly conductive metal is copper.

Claim 7

A system as claimed in claim 4 wherein the head portion of the valve pin has a central well extending from the tip end, and a beryllium copper plug is seated in the well adjacent the tip end.

Claim 8

A system as claimed in claim 6 wherein the plug is heat seated in the well.

Claim 9

A system as claimed in claim 7 wherein the diameter of the head portion of the valve pin is greater than one half inch.

Claim 10

A system as claimed in claim 3 wherein the head portion of the valve pin has a central portion extending between the hollow portion and the tip end formed of a highly conductive heat pipe.

Claim 11

A system as claimed in claim 8 further including adjustable stop means to limit the rearward travel of the valve pin to the closed position, whereby the amount of heat loss through the head portion of the valve pin may be varied.

Claim 12

A system as claimed in claim 10 wherein the stop means comprises an abutment sleeve of a particular height located in the actuator means.

Claim 13

In an injection molding system for filling.a cavity defined between a cool cavity plate and a cool movable mold platen with an opening therethrough, an elongated valve pin with a tip end which extends through a gate leading to the cavity, through the cavity, and into a bore in the movable mold platen, the gate, the opening through the cavity, and the bore in the movable mold platen being in alignment and substantially equal in diameter, valve pin actuating mechanism which reciprocates the valve pin between a rearward closed position and a forward open position in which the valve pin extends further through the opening through the cavity, a melt passage which extends through a manifold and around the valve pin to convey pressurized melt from a molding machine to the gate, the valve pin having an elongated head portion adjacent the tip end which extends from a reduced neck portion, the head portion being substantially equal in diameter to the gate, the opening through the cavity, and the bore in the movable mold platen, the reduced neck portion extending past the gate in the open position to provide for the flow of pressurized melt into the cavity, the improvement wherein the gate extends through a land in the cooled cavity plate and the head portion of the valve pin extends a considerable distance through the cavity into the bore in the movable mold platen, the head portion of the valve pin having a hollow portion adjacent the neck portion thereof such that the hollow portion does not extend above the gate when the valve pin is in the retracted position and does not extend into the bore when the valve pin is in the open position, whereby in the retracted closed positon contact between the head portion of the valve pin and the surrounding land of the cool cavity plate provides thermal separation between the hot neck portion of the valve pin and the head portion of the valve pin extending through the cavity, and sufficient contact is provided between the movable mold platen and head portion of the valve pin received in said bore to rapidly cool the melt surrounding the valve pin in the cavity.

Claim 14

In an injection molding system for filling.a cavity defined between a cool cavity plate and a cool movable mold platen with an opening therethrough, an elongated valve pin with a tip end which extends through a gate leading to the cavity, through the cavity, and into a bore in the movable mold platen, the gate, the opening through the cavity, and the bore in the movable mold platen being in alignment and substantially equal in diameter, valve pin actuating mechanism which reciprocates the valve pin between a rearward closed position and a forward open position in which the valve pin extends further through the opening through the cavity, a melt passage which extends through a manifold and around the valve pin to convey pressurized melt from a molding machine to the gate, the valve pin having an elongated head portion adjacent the tip end which extends from a reduced neck portion, the head portion being substantially equal in diameter to the gate, the opening through the cavity, and the bore in the movable mold platen, the reduced neck portion extending past the gate in the open position to provide for the flow of pressurized melt into the cavity, the improvement wherein the gate extends through a land in the cooled cavity plate and the head portion of the valve pin extends a considerable distance through the cavity into the bore in the movable mold platen, the head portion of the valve pin having a hollow portion adjacent the neck portion thereof such that the hollow portion does not extend above the gate when the valve pin is in the retracted position and does not extend into the bore when the valve pin is in the open position, whereby in the retracted closed positon contact between the head portion of the valve pin and the surrounding land of the cool cavity plate provides thermal separation between the hot neck portion of the valve pin and the head portion of the valve pin extending through the cavity, and sufficient contact is provided between the movable mold platen and head portion of the valve pin received in said bore to rapidly cool the melt surrounding the valve pin in the cavity.