초록 ▼

This invention relates to a valve gated injection molding system of the type where the melt passage enters the system on general alignment with the valve pin and cavity. The system has a novel valve pin actuating mechanism which is pneumatically operated according to a predetermined timed cycle. A p

This invention relates to a valve gated injection molding system of the type where the melt passage enters the system on general alignment with the valve pin and cavity. The system has a novel valve pin actuating mechanism which is pneumatically operated according to a predetermined timed cycle. A piston which reciprocates in a cylinder has an outer collar portion from which a tongue portion extends inwardly to operatively engage the driven end of the valve pin. The melt passage extends through a portion of the back plate which, in turn, extends through the outer collar portion of the piston and is offset to leave room for the tongue portion of the piston to engage the driven end of the valve pin. Piston rings are located between the piston, back plate and cylinder to prevent excessive air leakage. This center entry system with a pneumatic actuating mechanism provides a more reliable mechanism which may be double acting.

대표청구항 ▼

1. In a valve gated center entry injection molding system comprising a heater cast seated in a cooled cavity plate, a gate through the cavity plate leading to a cavity, an elongated valve pin which reciprocates in a bore in the heater cast between open and closed positions, the valve pin having a dr

1. In a valve gated center entry injection molding system comprising a heater cast seated in a cooled cavity plate, a gate through the cavity plate leading to a cavity, an elongated valve pin which reciprocates in a bore in the heater cast between open and closed positions, the valve pin having a driven end and a tip end which seats in the gate in the closed position, valve pin actuating mechanism, and a melt passage which receives pressurized melt from a molding machine at a center entry and extends through the heater cast to the gate, the improvement wherein; the valve pin actuating mechanism comprises a pneumatically operated piston which reciprocates in a cylinder generally in alignment with the valve pin and engages the driven end of the valve pin, the melt passage from the center entry to the gate disc extending through the piston cylinder. 2. An injection molding system as claimed in claim 1 wherein the piston is double acting and the piston operatively engages the driven end of the valve pin to drive it in both directions. 3. An injection molding system as claimed in claim 1 wherein the piston has an outer collar portion and a centrally extending tongue portion, the collar portion operatively received inside the cylinder and the tongue portion extending inwardly from the collar portion to engage the driven end of the valve pin. 4. An injection molding system as claimed in claim 2 wherein the melt passage extends from the center entry through a back plate to the heater cast, the back plate having a centrally offset portion which extends into abutment against the heater cast, and the outer collar portion of the piston encircles the back plate and is sealingly received between the back plate and the cylinder. 5. An injection molding system as claimed in claim 3 wherein the offset portion of the back plate abuts against a bushing seal seated in the heater cast, the melt passage extending into the bushing seal to join the valve pin bore which extends through the bushing seal, the valve pin bore having an enlarged portion to conduct the melt around the valve pin to the gate. 6. An injection molding system as claimed in claim 5 wherein sealing means are provided between the back plate and the collar portion of the piston and between the collar portion of the piston and the cylinder. 7. In a valve gated center entry injection molding system comprising a heater cast seated between a back plate and a cooled cavity plate, a gate through the cavity plate leading to a cavity, a melt passage which receives pressurized melt from a molding machine and extends from a center entry in the back plate through an offset portion of the back plate and the heater cast to the gate, an elongated valve pin which reciprocates in a bore in the heater cast with a central longitudinal axis in alignment with the gate and the center entry, the valve pin having a driven end and a tip end which seats in the gate in the closed position and valve pin actuating mechanism, the improvement wherein; the valve pin actuating mechanism comprises a pneumatically operated double acting piston which reciprocates in a cylinder, the piston having an outer collar portion and a tongue portion, the outer collar portion encircling the back plate and sealingly received between the back plate and the cylinder, the tongue portion extending inwardly from the collar portion to operatively engage the driven end of the valve pin. 8. An injection molding system as claimed in claim 7 wherein piston rings are provided between the back plate and the collar portion of the piston and between the collar portion of the piston and the cylinder. 9. An injection molding system as claimed in claim 3 wherein the tongue portion of the piston has channel means and the valve pin has a head portion adjacent the driven end, the head portion being operatively received in the channel means whereby rotation of the valve pin is substantially prevented during operation of the system.