Patent ID: 7597828

Claim:
A method of controlling the rate of flow of fluid through a flow channel communicating with a gate of a mold in an injection molding apparatus, the apparatus including a valve pin having a selected longitudinal length and a stem that is slidably mounted in an aperture in a housing body that is adapted for back and forth axial movement of the pin through the flow channel, the method comprising: forming the pin with a protrusion at a selected position along its length such that the protrusion is movable back and forth within the channel wherein the protrusion has an upstream end and a downstream end; forming the protrusion having upstream and downstream surfaces and a maximum diameter outer circumferential surface between the upstream and downstream surfaces; forming the mounting aperture for the stem with a diameter that is greater than or equal to the maximum diameter outer circumferential surface; forming the channel with an interior surface area portion which is complementary to the maximum diameter circumferential surface such that the maximum diameter outer circumferential surface of the protrusion is matable with the interior surface area portion of the channel to stop flow of the fluid through the channel; controlling movement of the pin through the channel to selectively position the upstream and downstream surfaces at positions either further away from or closer to the interior surface area portion of the channel such that the fluid flow rate can be regulated by positioning either the upstream or downstream surfaces further away from or closer to the interior surface area portion of the channel.