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A coinjection molding apparatus includes a manifold, a nozzle body coupled to the manifold, a sleeve disposed within the nozzle body and defining an outer melt channel between the sleeve and the nozzle body, a pin disposed within the sleeve and defining an inner melt channel between the pin and the

A coinjection molding apparatus includes a manifold, a nozzle body coupled to the manifold, a sleeve disposed within the nozzle body and defining an outer melt channel between the sleeve and the nozzle body, a pin disposed within the sleeve and defining an inner melt channel between the pin and the sleeve, and a nozzle tip having an alignment portion contacting the sleeve. The sleeve is actuated to open and close melt communication of the outer melt channel and a cavity gate. The pin is actuated to open and close melt communication of the inner melt channel and an opening of the sleeve. The alignment portion aligns the sleeve with the cavity gate along the actuated range of the sleeve.

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I claim: 1. A coinjection molding apparatus comprising: a manifold comprising a first manifold melt channel, a second manifold melt channel, and a guide bore; a nozzle body comprising a longitudinal bore aligned with the guide bore, the nozzle body coupled to the manifold; a sleeve disposed within

I claim: 1. A coinjection molding apparatus comprising: a manifold comprising a first manifold melt channel, a second manifold melt channel, and a guide bore; a nozzle body comprising a longitudinal bore aligned with the guide bore, the nozzle body coupled to the manifold; a sleeve disposed within the longitudinal bore, the sleeve comprising a tip portion comprising an opening, and the sleeve having a hollow section and a section narrower than the longitudinal bore thus defining an outer melt channel between the sleeve and the nozzle body, the outer melt channel communicating with the first manifold melt channel, the sleeve slidably disposed in the guide bore to open and close melt communication of the outer melt channel to a cavity gate by the tip portion of the sleeve; a pin disposed within the hollow section of the sleeve and comprising a tip, the pin having a section narrower than the hollow section of the sleeve thus defining an inner melt channel between the pin and the sleeve, the inner melt channel for communicating with the second manifold melt channel, the pin slidably disposed in the sleeve to open and close melt communication of the inner melt channel to the opening of the sleeve by the tip of the pin; and a nozzle tip coupled to the nozzle body and comprising a nozzle tip melt channel in communication with the longitudinal bore and forming part of the outer melt channel, the nozzle tip further comprising an alignment portion contacting the sleeve, the alignment portion for aligning the tip portion of the sleeve with the cavity gate along the sliding range of the sleeve. 2. A coinjection molding apparatus as claimed in claim 1, wherein the alignment portion comprises an alignment bore through which the sleeve slides. 3. A coinjection molding apparatus as claimed in claim 2, wherein the nozzle tip further comprises a release melt channel upstream of the alignment bore, the release melt channel communicating with the nozzle tip melt channel and an annular melt channel that circumferentially surrounds a portion of the nozzle tip downstream of the release melt channel. 4. A coinjection molding apparatus as claimed in claim 2, wherein an inside surface of the alignment bore comprises a friction-reducing coating or a wear-resistant coating. 5. A coinjection molding apparatus as claimed in claim 1, wherein the nozzle tip comprises a first tubular portion coupled to the nozzle body and that partially defines the outer melt channel, and a second tubular portion that comprises an alignment bore through which the sleeve slides, the second tubular portion having a smaller diameter than the first tubular portion and being located downstream of the first tubular portion. 6. A coinjection molding apparatus as claimed in claim 5 further comprising a release melt channel located between the first tubular portion and the second tubular portion. 7. A coinjection molding apparatus as claimed in claim 1, wherein the nozzle tip further comprises a release melt channel upstream of the alignment portion, the release melt channel communicating with the nozzle tip melt channel and an annular melt channel that circumferentially surrounds a portion of the nozzle tip downstream of the release melt channel. 8. A coinjection molding apparatus as claimed in claim 1 further comprising a tip retaining piece connected to the nozzle body and retaining the nozzle tip with respect to the nozzle body. 9. A coinjection molding apparatus as claimed in claim 8, wherein the tip retaining piece comprises a sealing portion that contacts a mold insert or a mold plate. 10. A coinjection molding apparatus as claimed in claim 8, wherein the tip retaining piece is made of a material that is less thermally conductive than a material of which the nozzle tip is made. 11. A coinjection molding apparatus as claimed in claim 1, wherein the sleeve comprises a lateral opening between the second manifold melt channel and the inner melt channel, the lateral opening allowing melt to flow from the second manifold melt channel to the inner melt channel, and wherein the pin further comprises a shut-off portion of an outer diameter substantially equal to an inner diameter of the sleeve at the lateral opening, the shut-off portion obstructing the lateral opening when the pin is in the closed position. 12. A coinjection molding apparatus as claimed in claim 1, wherein the outer and inner melt channels have substantially annular cross-sections. 13. A coinjection molding apparatus as claimed in claim 1, wherein the pin further comprises at least a fin that contacts an inner wall of the hollow section of the sleeve to align the pin within the sleeve. 14. A coinjection molding apparatus as claimed in claim 1, wherein the manifold or the nozzle further comprises an electric heater. 15. A coinjection molding apparatus as claimed in claim 1 further comprising a first actuator comprising a piston coupled to the sleeve and a second actuator comprising a piston coupled to the pin. 16. A coinjection molding apparatus as claimed in claim 15 further comprising a yoke plate to which the sleeve and the piston of the first actuator are attached, wherein a body of the first actuator is fixed to a backing plate. 17. A coinjection molding apparatus as claimed in claim 16, wherein a body of the second actuator is attached to the yoke plate and moves with the yoke plate. 18. A coinjection molding apparatus comprising: a moveable yoke plate; an actuator comprising a body fixed to the yoke plate and a moveable piston disposed in the body; a manifold comprising a first manifold melt channel, a second manifold melt channel, and a guide bore; a nozzle body comprising a longitudinal bore, the nozzle body coupled to the manifold; a sleeve disposed within the longitudinal bore, the sleeve comprising a tip portion having an opening, and the sleeve having a hollow section and a section narrower than the longitudinal bore thus defining an annular outer melt channel between the sleeve and the nozzle body, the outer melt channel communicating with the first manifold melt channel, the sleeve connected to the yoke plate and movable through the guide bore to open and close melt communication of the outer melt channel to a cavity gate by the tip portion of the sleeve; a pin disposed within the hollow section of the sleeve and comprising a tip, the pin having a section narrower than the hollow section of the sleeve thus defining an annular inner melt channel between the pin and the sleeve, the inner melt channel for communicating with the second manifold melt channel, the pin connected to the piston of the actuator to open and close melt communication of the inner melt channel to the opening of the sleeve with the tip of the pin, wherein the pin further comprises at least a fin that contacts an inner wall of the hollow section of the sleeve to align the tip of the pin by the opening of the sleeve; a nozzle tip coupled to the nozzle body and comprising a nozzle tip melt channel in communication with the longitudinal bore and forming part of the outer melt channel, the nozzle tip further comprising an alignment portion having an alignment bore through which the sleeve slides, the alignment bore aligning the tip portion of the sleeve with the cavity gate along the sliding range of the sleeve, wherein the nozzle tip further comprises a release melt channel upstream of the alignment bore, the release melt channel communicating with the nozzle tip melt channel and an annular melt channel that circumferentially surrounds a portion of the nozzle tip downstream of the release melt channel; and a tip retaining piece connected to the nozzle body and retaining the nozzle tip with respect to the nozzle body. 19. A coinjection molding apparatus as claimed in claim 1, wherein the sleeve comprises a lateral opening between the second manifold melt channel and the inner melt channel, the lateral opening for allowing melt to flow from the second manifold melt channel to the inner melt channel, and wherein the pin further comprises a shut-off portion of an outer diameter substantially equal to an inner diameter of the sleeve at the lateral opening, the shut-off portion obstructing the lateral opening when the pin is in the closed position. 20. A coinjection molding apparatus comprising: a manifold comprising a first manifold melt channel, a second manifold melt channel, and a guide bore; a nozzle body comprising a longitudinal bore aligned with the guide bore, the nozzle body coupled to the manifold; a sleeve disposed within the longitudinal bore, the sleeve comprising a tip portion comprising an opening, and the sleeve having a hollow section and a section narrower than the longitudinal bore thus defining an outer melt channel between the sleeve and the nozzle body, the outer melt channel communicating with the first manifold melt channel, the sleeve slidably disposed in the guide bore to open and close melt communication of the outer melt channel to a cavity gate by the tip portion of the sleeve; means for sliding the sleeve; a pin disposed within the hollow section of the sleeve and comprising a tip, the pin having a section narrower than the hollow section of the sleeve thus defining an inner melt channel between the pin and the sleeve, the inner melt channel for communicating with the second manifold melt channel, the pin slidably disposed in the sleeve to open and close melt communication of the inner melt channel to the opening of the sleeve by the tip of the pin; means for sliding the pin; and a nozzle tip coupled to the nozzle body and comprising a nozzle tip melt channel in communication with the longitudinal bore and forming part of the outer melt channel, the nozzle tip further comprising a means for aligning the tip portion of sleeve with the cavity gate. 21. A hot-runner nozzle for a coinjection molding apparatus, comprising: a nozzle body having a longitudinal bore; a sleeve comprising a tip portion having an opening therein, the sleeve being slidably disposed within the longitudinal bore; an outer melt channel located between the sleeve and the nozzle body; a pin comprising a tip, the pin being slidably disposed within the sleeve; an inner melt channel located between the pin and the sleeve; and a nozzle tip coupled to the nozzle body and comprising an alignment portion that aligns the tip portion of the sleeve with a cavity gate over a sliding range of the sleeve; wherein the sliding range of the sleeve is between opened and closed positions in which the tip portion controls melt communication of the outer melt channel and the cavity gate, wherein in the closed position the tip portion of the sleeve engages the cavity gate; wherein the pin is slidable between opened and closed positions in which the tip controls melt communication of the inner melt channel and the opening of the sleeve. 22. A hot-runner nozzle as claimed in claim 21, wherein the alignment portion comprises an alignment bore through which the sleeve slides. 23. A hot-runner nozzle as claimed in claim 22, wherein an inside surface of the alignment bore comprises a friction-reducing coating or a wear-resistant coating. 24. A hot-runner nozzle as claimed in claim 21 further comprising a tip retaining piece connected to the nozzle body and retaining the nozzle tip with respect to the nozzle body. 25. A hot-runner nozzle as claimed in claim 21, wherein the outer and inner melt channels have substantially annular cross-sections. 26. A hot-runner nozzle as claimed in claim 21, wherein the pin further comprises at least a fin that contacts an inner wall of the sleeve to align the tip of the pin with the opening of the sleeve. 27. A hot-runner nozzle as claimed in claim 21, wherein the nozzle tip further comprises a lateral release melt channel between the outer melt channel and the cavity gate. 28. A hot-runner nozzle as claimed in claim 27, wherein the lateral release melt channel is located upstream of the alignment portion, the lateral release melt channel communicating between the outer melt channel and an annular melt channel that circumferentially surrounds a portion of the nozzle tip downstream of the lateral release melt channel.