Importance

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Abstract

A center entry valve gated injection molding system having a heated nozzle secured in front of a heated manifold with at least a pair of valve member biasing mechanisms extending radially outward from a reciprocating elongated valve member. The melt passage splits into two branches which extend through a manifold outwardly around a rear portion of the valve member. The two branches of the melt passage and the two biasing mechanisms are alternatively evenly angularly spaced around the valve member which considerably reduces the space required. The valve member has an enlarged forward end which opens forwardly into the cavity and is closed in a retracted position in which it seats in the matching mouth of a gate in a nose portion of the nozzle. Each biasing mechanism includes a compression spring which engages a lever member to continuously urge the valve member rearwardly. When injection pressure is applied it overcome the force of the springs and moves the valve member forwardly to the open position. When the cavity is filled, the combination of the back pressure of the melt and the force of the springs with a mechanical advantage from the lever members withdraws the valve member to the closed position. In an alternate embodiment, only a single biasing mechanism is utilized.

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First Claim