Nozzle configuration for purging flow channel

An injection molding apparatus comprised of an injection molding machine that injects an injection fluid material into a heated manifold,

• a nozzle having a fluid flow channel having a longitudinal axis A and an upstream end that receives the injection fluid material from the heated manifold and delivers the injection fluid material to a downstream end that sealably delivers the injection fluid material to a gate of a cavity of a mold body,
• the downstream end of the nozzle comprising an inner tubular member having an outer circumferential surface and an outer tubular member having an inner tubular surface, the outer tubular member forming a seal surrounding the gate,
• the inner and outer tubular members being adapted to form a sealed circumferential gap G between the outer circumferential surface of the inner tubular member and the inner circumferential surface of the outer tubular member, the circumferential gap G circumferentially surrounding the fluid flow channel,
• a valve pin being disposed within the fluid flow channel,
• the inner tubular member has one or more apertures extending radially through the inner tubular member between the fluid flow channel and the circumferential gap G to enable flow of the injection fluid material that is injected in an upstream to downstream path of flow through the fluid flow channel to flow radially from the fluid flow channel into the circumferential gap G,
• the valve pin having a maximum downstream diameter section that has an outer circumferential surface that is complementary to and mates with a complementary interior mating surface of the inner tubular member such that the injection fluid material is stopped or substantially reduced when the complementary surfaces are axially aligned forcing flow of the injection fluid material to flow through the one or more apertures and the circumferential gap G,
• a controller having a program that contains instructions that control axial positioning of the outer circumferential surface of the valve pin relative to an inner surface of the inner tubular member to form a flow restriction UG through the nozzle channel for one or more predetermined amounts of time during the course of an injection cycle sufficient to cause flow of the injection fluid material to be routed at an elevated rate of flow through the one or more apertures and the circumferential gap G.