US Patent 7597828 Injection molding valve flow control

Apparatus for controlling the rate of flow of fluid material through an injection molding flow channel leading to a mold cavity, the apparatus comprising:a pin having a longitudinal length and a diameter slidably mounted in an aperture in a housing that is adapted for back and forth axial movement of the pin through the flow channel;the pin having a protrusion at a selected position along its length, the protrusion having an upstream end and a downstream end and a maximum diameter circumferential surface intermediate the upstream and downstream ends;the channel having an interior surface area portion which is complementary to the maximum diameter circumferential surface of the protrusion of the pin;the pin being slidable to a position within the channel such that the maximum diameter circumferential surface of the protrusion is matable with the complementary interior surface portion of the channel to stop flow of the fluid material.