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A valve pin guide is provided for guiding a valve pin from a nozzle into a gate of a mold cavity in an injection molding apparatus. The valve pin guide defines a guide aperture therethrough. The guide aperture is adapted to receive and guide the valve pin into alignment with the gate. The valve pin

A valve pin guide is provided for guiding a valve pin from a nozzle into a gate of a mold cavity in an injection molding apparatus. The valve pin guide defines a guide aperture therethrough. The guide aperture is adapted to receive and guide the valve pin into alignment with the gate. The valve pin guide is positioned downstream from said nozzle and upstream from said gate.

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1. A valve pin guide positioned downstream from a nozzle for receiving and guiding a valve pin into a gate for a mold cavity in an injection molding apparatus, the valve pin guide comprising:a guiding portion in which a guide aperture is defined therethrough, wherein said guiding portion is made fro

1. A valve pin guide positioned downstream from a nozzle for receiving and guiding a valve pin into a gate for a mold cavity in an injection molding apparatus, the valve pin guide comprising:a guiding portion in which a guide aperture is defined therethrough, wherein said guiding portion is made from a guiding portion material having a first thermal conductivity and said guiding portion is adapted to contact the nozzle; and an insulating portion, wherein said insulating portion is made from an insulating portion material having a second thermal conductivity, wherein said second thermal conductivity is lower than said first thermal conductivity and said insulating portion is adapted to contact a mold cavity block. 2. The valve pin guide as claimed in claim 1, wherein the gate is defined in a mold component, and said valve pin guide has a sealing surface, wherein said sealing surface is adapted to cooperate with the mold component to seal against melt leakage around the gate.3. The valve pin guide as claimed in claim 1, wherein said valve pin guide is removably positionable downstream from the nozzle and upstream from the gate.4. The valve pin guide as claimed in claim 1, wherein said valve pin guide is adapted to slidably contact the nozzle, to accommodate thermal expansion and contraction of the nozzle during an injection molding operation.5. The valve pin guide as claimed in claim 1, wherein the nozzle has a nozzle tip that is made from a nozzle tip material having a thermal conductivity that is less than said first thermal conductivity of said guiding portion of said valve pin guide.6. An injection molding apparatus, comprising:at least one nozzle having a nozzle melt passage therethrough for receiving a melt from a melt source; a nozzle tip secured to a downstream end of said nozzle by a nozzle tip retainer, wherein said nozzle tip receives the melt from said nozzle melt passage; a mold cavity block defining at least one mold cavity and a gate into said at least one mold cavity, wherein said gate is positioned downstream from said nozzle tip; a valve pin, wherein said valve pin is movable in said nozzle tip and said nozzle melt passage to open and close said gate; and a valve pin guide positioned downstream from said nozzle tip and upstream from said gate, wherein said valve pin guide defines a guide aperture therethrough that is adapted to receive and guide said valve pin into alignment with said gate. 7. The injection molding apparatus as claimed in claim 6, wherein said valve pin guide is in contact with said mold cavity block.8. The injection molding apparatus as claimed in claim 6, wherein said valve pin guide is connected to said mold cavity block.9. The injection molding apparatus as claimed in claim 6, wherein said valve pin guide is removably connected to said mold cavity block.10. The injection molding apparatus as claimed in claim 6, wherein said valve pin is movable to an open position to permit melt flow into said mold cavity, and wherein in said open position said valve pin is spaced from said guide aperture.11. The injection molding apparatus as claimed in claim 6, wherein said valve pin has a sealing surface, wherein said sealing surface is adapted to form a seal with said gate to prevent melt flow therebetween, and said valve pin has a guide surface, wherein said guide surface is adapted to cooperate with said guide aperture on said valve pin guide to align said valve pin with said gate prior to said sealing surface contacting said gate.12. The injection molding apparatus as claimed in claim 11, wherein said sealing surface on said valve pin is a separate surface from said guide surface.13. The injection molding apparatus as claimed in claim 6, wherein said gate is defined in a separate gate insert component from said surrounding portion of said mold cavity block.14. The injection molding apparatus as claimed in claim 6, wherein said nozzle tip is made from a nozzle tip material having a first thermal conductivity, and said valve pin guide is made from a valve pin guide material having a second thermal conductivity and said second thermal conductivity is less than said first thermal conductivity.15. The injection molding apparatus as claimed in claim 14, wherein said nozzle has a nozzle body and said nozzle tip is attached to said nozzle body.16. The injection molding apparatus as claimed in claim 6, wherein said valve pin guide has a sealing surface, that is adapted to cooperate with said mold cavity block to seal against melt leakage around said gate.17. The injection molding apparatus as claimed in claim 6, wherein said valve pin guide is adapted to slidably contact said nozzle to accommodate thermal expansion and contraction of said nozzle during an injection molding operation.18. The injection molding apparatus as claimed in claim 6, wherein said valve pin guide comprises,a guiding portion in which said guide aperture is defined, wherein said guiding portion is made from a guiding portion material having a first thermal conductivity, said guiding portion is adapted to contact said nozzle, and an insulating portion, wherein said insulating portion is made from an insulating portion material having a second thermal conductivity, wherein said second thermal conductivity is lower than said first thermal conductivity and wherein said insulating portion is adapted to contact said mold cavity block. 19. The injection molding apparatus as claimed in claim 18, wherein said valve pin guide is adapted to slidably contact said nozzle, to accommodate thermal expansion and contraction of said nozzle during an injection molding operation.20. The injection molding apparatus as claimed in claim 6, further comprising: a resilient member that is positioned between said nozzle and said valve pin guide.21. The injection molding apparatus as claimed in claim 6, wherein said valve pin guide is attached to said nozzle.22. An injection molding apparatus, comprising:a mold cavity block, wherein said mold cavity block defines a mold cavity therein, said mold cavity has a gate, wherein said mold cavity block has a first bore and a second bore, wherein said gate is positioned in said second bore and wherein said first bore is larger in diameter than said second bore; an injection nozzle having a nozzle tip secured thereto by a tip retainer, wherein a melt channel is defined in said injection nozzle and said nozzle tip to convey melt towards said gate; a valve pin, wherein said valve pin is positioned at least partially in said melt channel and is movable to control melt flow into said gate; and a valve pin guide, wherein said valve pin guide is adapted to receive and guide said valve pin into alignment with said gate, and wherein said valve pin guide is positioned in said first bore downstream from said nozzle tip. 23. The injection molding apparatus according to claim 22, wherein said second bore is in fluid communication with said melt channel so that said second bore substantially fills with melt during an injection molding operation.24. The injection molding apparatus according to claim 22, wherein a shoulder separates said first and second bores and said valve pin guide is adapted to seal against said shoulder.25. The injection molding apparatus according to claim 22, wherein said nozzle includes a sealing surface that is adapted to cooperate with said first bore to inhibit melt leakage therebetween.