Nozzle configuration for purging flow channel
An injection molding apparatus comprising: an injection molding machine, a heated manifold, a nozzle, the downstream end of the nozzle comprising an inner tubular member having a central flow channel and 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, the inner tubular member including one or apertures extending radially through the inner tubular member to route flow radially from the fluid flow channel into the circumferential gap.
1. 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.
2. An apparatus according to claim 1 wherein the one or more apertures are configured to direct or route the injection fluid material that is injected from the upstream end of the nozzle downstream through the fluid flow channel and radially and longitudinally through the circumferential gap G.
3. An apparatus according to claim 1 wherein the one or more apertures have a flow axis that is configured and disposed at an angle to the longitudinal axis A of the fluid flow channel of the nozzle that is adapted to route injection fluid radially and in a downstream axial direction through the circumferential gap G toward the gate.
4. An apparatus according to claim 1 wherein the inner tubular member is mounted within and circumferentially surrounded by the outer tubular member at the distal end of the nozzle, the inner tubular member having an outer circumferential mating surface that is sealably engaged against an inner seal surface of the outer tubular member to seal against upstream flow of the injection fluid material through the circumferential gap G.
5. An apparatus according to claim 1 wherein the outer tubular member has an exterior seal surface sealably engaged against a mold body seal surface to seal against upstream flow the injection fluid material through the circumferential gap G.
6. An apparatus according to claim 1 wherein the inner tubular member is mounted and nested within the outer tubular member in an arrangement that seals the injection fluid material against upstream flow through the circumferential gap G.
7. An apparatus according to claim 1 further comprising a controller containing instructions that direct withdrawal of the valve pin upstream from a gate closed position at one or more reduced rates of travel relative to a maximum rate of travel upstream to one or more partially gate open positions.