Injection molding machine for molding preforms

Abstract

An injection molding machine includes a machine base extending along a horizontal machine axis; a stationary platen fixed to the base; a moving platen supported by the base; a center section supported by the base axially intermediate the stationary and moving platens; at least one mold stroke actuator for translating the moving platen and the center section along the machine axis between a mold-open position and a mold-closed position; a two-stage first injection unit supported by the base behind the stationary platen for injecting a first resin through the stationary platen; and a two-stage second injection unit supported by the base behind the moving platen for injecting a second resin through the moving platen. The second injection unit is translatable along the machine axis to accommodate translation of the moving platen during movement between the mold-open and mold-closed positions.

What is claimed is: 
     
         1 . An injection molding machine for molding preforms, comprising:
 a) a machine base extending along a horizontal machine axis;   b) a stationary platen fixed to the base for supporting a first cavity mold half;   c) a moving platen supported by the base and translatable along the machine axis towards and away from the stationary platen, the moving platen for supporting a second cavity mold half;   d) a center section supported by the base axially intermediate the stationary and moving platens, the center section having a center section first face for supporting a first core mold half and a center section second face opposite the center section first face for supporting a second core mold half, the moving platen and the center section translatable along the machine axis between a mold-open position, in which the first cavity mold half is spaced axially apart from the first core mold half and the second cavity mold half is spaced axially apart from the second core mold half, and a mold-closed position, in which the first cavity mold half is in engagement with the first core mold half to define a set of first mold cavities for forming a set of molded first preforms, and in which the second cavity mold half is in engagement with the second core mold half to define a set of second mold cavities for forming a set of molded second preforms;   e) a first take-out plate on a non-operator side of the machine, the first take-out plate moveable relative to the base between at least one first advanced position for reaching between the first cavity mold half and the first core mold half when the moving platen and center section are in the mold-open position to facilitate transfer of the first preforms from the first core mold half on the center section to retained engagement on the first take-out plate, and a first retracted position in which the first take-out plate is clear of the first cavity mold half and the first core mold half; and   f) a second take-out plate on the non-operator side of the machine, the second take-out plate moveable relative to the base between at least one second advanced position for reaching between the second cavity mold half and the second core mold half when the moving platen and the center section are in the mold-open position to facilitate transfer of the second preforms from the second core mold half on the center section to retained engagement on the second take-out plate, and a second retracted position in which the second take-out plate is clear of the second cavity mold half and the second core mold half.   
     
     
         2 . The machine of  claim 1 , wherein the first take-out plate translates along a horizontal first take-out plate axis between the first advanced and retracted positions and the second take-out plate translates along a horizontal second take-out plate axis between the second advanced and retracted positions, the first and second take-out plate axes perpendicular to the machine axis. 
     
     
         3 . The machine of  claim 2 , wherein the first take-out plate includes at least one set of first cooling tubes for retaining and cooling the first preforms and at least one first internal fluid conduit for conducting coolant to and from the first cooling tubes, the first cooling tubes having first open ends directed toward the center section first face when the first take-out plate is in the advanced position, and wherein the second take-out plate includes at least one set of second cooling tubes for retaining and cooling the second preforms and at least one second internal fluid conduit for conducting coolant to and from the second cooling tubes, the second cooling tubes having second open ends directed toward the center section second face when the second take-out plate is in the second advanced position. 
     
     
         4 . The machine of  claim 3 , wherein the first take-out plate includes a set of set-A first cooling tubes and a set of set-B first cooling tubes, and wherein the first take-out plate is translatable to a set-A first advanced position for aligning the set-A first cooling tubes with first mold core pins of the first core mold half, and a set-B first advanced position for aligning the set-B first cooling tubes with the first mold core pins, the set-A and set-B first advanced positions offset from each other along the first take-out plate axis. 
     
     
         5 . The machine of  claim 4 , wherein the second take-out plate includes a set of set-A second cooling tubes and a set of set-B second cooling tubes, and wherein the second take-out plate is translatable to a set-A second advanced position for aligning the set-A second cooling tubes with second mold core pins of the second core mold half, and a set-B second advanced position for aligning the set-B second cooling tubes with the second mold core pins, the set-A and set-B second advanced positions offset from each other along the second take-out plate axis. 
     
     
         6 . The machine of  claim 1 , further comprising a transfer shell on the non-operator side of the machine axially intermediate the first and second take-out plates, the transfer shell including a shell first face having a set of first transfer pins protruding therefrom for retaining the first preforms, and a shell second face opposite the shell first face, the shell second face having a set of second transfer pins protruding therefrom for retaining the second preforms. 
     
     
         7 . The machine of  claim 6 , wherein when in the first retracted position, the first take-out plate is translatable parallel to the machine axis toward the transfer shell to a first shell-transfer position to facilitate transfer of the first preforms to retained engagement on the first transfer pins, and wherein when in the second retracted position, the second take-out plate is translatable parallel to the machine axis toward the transfer shell to a second shell-transfer position to facilitate transfer of the second preforms to retained engagement on the second transfer pins. 
     
     
         8 . The machine of  claim 6 , wherein the transfer shell is rotatable about a horizontal shell axis generally perpendicular to the machine axis, the transfer shell rotatable among a load position in which the shell first face is directed axially toward the first take-out plate and the shell second face is directed axially toward the second take-out plate, a first unload position in which the shell first face is directed downwardly for releasing the first preforms from the shell, and a second unload position in which the shell second face is directed downwardly for releasing the second preforms from the transfer shell. 
     
     
         9 . An injection molding machine for molding preforms, comprising:
 a) a machine base extending along a horizontal machine axis;   b) a stationary platen fixed to a platen support portion of the base for supporting a first cavity mold half;   c) a moving platen supported by the platen support portion and spaced axially apart from the stationary platen, the moving platen for supporting a second cavity mold half;   d) a center section supported by the platen support portion axially intermediate the stationary and moving platens, the center section having a center section first face for supporting a first core mold half and a center section second face opposite the center section first face for supporting a second core mold half;   wherein the moving platen and the center section are translatable along the machine axis between a mold-open position, in which the first cavity mold half is spaced axially apart from the first core mold half and the second cavity mold half is spaced axially apart from the second core mold half, and a mold-closed position, in which the first cavity mold half is in engagement with the first core mold half to define a set of first mold cavities for forming a set of molded first preforms, and in which the second cavity mold half is in engagement with the second core mold half to define a set of second mold cavities for forming a set of molded second preforms;   e) a two-stage first injection unit supported by a first injection unit support portion of the base and positioned behind the stationary platen for injecting a first resin into the first mold cavities through the stationary platen, the first injection unit including a first plasticizing apparatus for plasticizing the first resin and a first plunger apparatus transversely offset from the first plasticizing apparatus for receiving the first resin from the first plasticizing apparatus and forcing the first resin into the first mold cavities through a first nozzle of the second injection unit; and   f) a two-stage second injection unit supported by a second injection unit support portion of the base and positioned behind the moving platen for injecting a second resin into the second mold cavities through the moving platen, the second injection unit including a second plasticizing apparatus for plasticizing the second resin and a second plunger apparatus transversely offset from the second plasticizing apparatus for receiving the second resin from the second plasticizing apparatus and forcing the second resin into the second mold cavities through a second nozzle of the second injection unit, the second injection unit translatable along the machine axis between injection unit retracted and advanced positions to accommodate translation of the moving platen during movement between the mold-open and mold-closed positions.   
     
     
         10 . The machine of  claim 9 , wherein the second nozzle is in a fixed position relative to the moving platen during machine operation. 
     
     
         11 . The machine of  claim 10 , further comprising a sprue engagement actuator coupled to the second injection unit for holding the second nozzle in engagement with a sprue of the second cavity mold half during machine operation. 
     
     
         12 . The machine of  claim 11 , wherein the sprue engagement actuator comprises at least one hydraulic cylinder connected at one end to the moving platen and at the opposite end to the second plunger apparatus. 
     
     
         13 . The machine of  claim 9 , further comprising a stroke assembly for translating the moving platen and the center mold section between the mold-open and the mold-closed positions, and the second injection unit between the injection unit retracted and advanced positions. 
     
     
         14 . The machine of  claim 13 , wherein the stroke assembly comprises at least one mold stroke actuator mounted to the base and coupled to the moving platen for translating the moving platen along the machine axis. 
     
     
         15 . The machine of  claim 14 , wherein the stroke assembly comprises at least one injection unit stroke actuator mounted to the base and coupled to the second injection unit for translating the second injection unit along the machine axis. 
     
     
         16 . The machine of  claim 15 , wherein the at least one injection unit stroke actuator is operable to translate the second injection unit along the machine axis over at least an injection unit stroke length, the injection unit stroke length equal to an axial mold stroke length traversed by the moving platen when moving between the mold-open and mold-closed positions. 
     
     
         17 . The machine of  claim 16 , wherein the at least one injection unit stroke actuator provides at least a portion of an injection unit stroke force required to translate the second injection unit over the injection unit stroke length, and the at least one mold stroke actuator provides at least a portion of a mold stroke force required to translate the moving platen and the center section between the mold-open and mold-closed positions, and wherein a sum of the injection unit stroke force and the mold stroke force is provided by a combination of the mold stroke actuator and the injection unit stroke actuator. 
     
     
         18 . The machine of  claim 9 , wherein the first and second injection units are interchangeable. 
     
     
         19 . A method of operating an injection molding machine for molding preforms, comprising:
 a) plasticizing a first resin in a first plasticizing apparatus of a two-stage first injection unit supported behind a stationary platen, and plasticizing a second resin in a second plasticizing apparatus of a two-stage second injection unit supported behind a moving platen;   b) forcing the first resin from a first shooting pot transversely offset from the first plasticizing apparatus through the stationary platen and into a set of first mold cavities to form a set of molded first preforms, the first mold cavities defined by a first cavity mold half supported by the stationary platen and a first core mold half supported by a center mold section; and   c) forcing the second resin from a second shooting pot transversely offset from the second plasticizing apparatus through the moving platen and into a set of second mold cavities to form a set of molded second preforms, the second mold cavities defined by a second cavity mold half supported by the moving platen and a second core mold half supported by the center mold section opposite the first core mold half.   
     
     
         20 . The method of  claim 19 , further comprising, after step (c), (d) energizing a mold stroke actuator to provide at least a portion of a mold stroke force required to translate the moving platen and the center section away from the stationary platen to open the mold.