Preform molding system and mold stack for a preform molding system

Abstract

A preform molding system is disclosed that includes a cavity half that is mountable to a stationary platen of an injection molding machine and a core half that is mountable to a moving platen of the injection molding machine. The preform molding system includes a mold stack assembly having a cavity portion and a core portion. The cavity portion is coupled to the cavity half and includes a cavity insert, and the core portion is coupled to the core half and includes a core insert, a pair of neck rings, and a stripper ring. The core insert has an undercut that defines an annular protrusion on an internal surface of a preform that is created in the mold stack assembly. The preform molding system is configured to permit in sequence, retraction of the pair of neck rings away from the core insert and ejection of the preform from the core insert via the stripper ring.

1 - 20 . (canceled) 
     
     
         21 . A method of ejecting a preform from a preform molding system mounted in an injection molding machine, the method comprising:
 separating a core half and a cavity half of the preform molding system;   retracting a pair of neck rings from the preform;   axially displacing the preform relative to a core insert of the core half to cause an open end of the preform to expand around a calibration portion of the core insert; and   maintaining the open end of the preform in an expanded state while continuing to axially displace the preform from the core insert of the core half of the preform molding system.   
     
     
         22 . The method of  claim 21 , wherein separating the core half and the cavity half translates the preform molding system from a mold closed configuration to a mold open configuration. 
     
     
         23 . The method of  claim 22 , wherein linear movement associated with translating the preform molding system from the mold closed configuration to the mold open configuration causes lateral slides on the core half to move away from the core insert and thereby retracting the pair of neck rings, which are coupled to the lateral slides, from the preform. 
     
     
         24 . The method of  claim 21 , wherein axially displacing the preform relative to the core insert is caused by advancing a stripper ring to push the preform, and thereby cause sloped surfaces of a concave portion of the preform and an undercut inward portion of the core insert to co-act to circumferentially enlarge the open end of the preform around the calibration portion. 
     
     
         25 . The method of  claim 24 , wherein as the stripper ring is advanced the open end of the preform is maintained in an expanded state, with a protrusion at the open end of the preform maintaining inward pressure against the calibration portion of the core insert, until the protrusion at the open end of the preform is pushed clear of the calibration portion by the stripper ring. 
     
     
         26 . The method of  claim 25 , wherein the inward pressure of the protrusion at the open end of the preform against the calibration portion of the core insert forces the open end of the preform to conform to a cross-sectional shape of the calibration portion as the protrusion is pushed along a length of the calibration portion. 
     
     
         27 . The method of  claim 25 , wherein once the stripper ring has pushed the protrusion at the open end of the preform past the calibration portion of the core insert, a tension or outward pressure on a finish portion of the preform is released and an elasticity of molding material that forms the preform causes the finish portion of the preform to return to a relaxed state. 
     
     
         28 . The method of  claim 21 , further comprising permitting the preform to fall from between the core and cavity halves to be transferred away from the injection molding machine. 
     
     
         29 . The method of  claim 21 , further comprising receiving the preform by a take-out plate of a post-mold cooling system to be cooled outside of the injection molding machine. 
     
     
         30 . A method of molding a preform with a preform molding system mounted in an injection molding machine, the method comprising:
 moving a core half and a cavity half of the preform molding system into a mold closed configuration;   injecting a moldable material into a mold cavity formed by a core insert of the core half and a cavity insert of the cavity half;   maintaining the mold closed configuration until the moldable material solidifies such that a preform formed thereby can withstand further handling without being damaged; and   performing the method of ejecting a preform from the preform molding system according to  claim 21 .   
     
     
         31 . The method of  claim 30 , wherein separating the core half and the cavity half translates the preform molding system from the mold closed configuration to a mold open configuration. 
     
     
         32 . The method of  claim 31 , wherein linear movement associated with translating the preform molding system from the mold closed configuration to the mold open configuration causes lateral slides on the core half to move away from the core insert of the core half to thereby retract the pair of neck rings, which are coupled to the lateral slides, from the preform. 
     
     
         33 . The method of  claim 30 , wherein axially displacing the preform relative to the core insert is caused by advancing a stripper ring to push the preform, and thereby cause sloped surfaces of a concave portion of the preform and an undercut inward portion of the core insert to co-act to circumferentially enlarge the open end of the preform around the calibration portion. 
     
     
         34 . The method of  claim 33 , wherein as the stripper ring is advanced the open end of the preform is maintained in an expanded state, with a protrusion at the open end of the preform maintaining inward pressure against the calibration portion of the core insert, until the protrusion at the open end of the preform is pushed clear of the calibration portion by the stripper ring. 
     
     
         35 . The method of  claim 34 , wherein the inward pressure of the protrusion at the open end of the preform against the calibration portion of the core insert forces the open end of the preform to conform to a cross-sectional shape of the calibration portion as the protrusion is pushed along a length of the calibration portion. 
     
     
         36 . The method of  claim 34 , wherein once the stripper ring has pushed the protrusion at the open end of the preform past the calibration portion of the core insert, an outward pressure on a finish portion of the preform is released and an elasticity of the moldable material that forms the preform causes the finish portion of the preform to return to a relaxed state. 
     
     
         37 . The method of  claim 30 , further comprising permitting the preform to fall from between the core and cavity halves to be transferred away from the injection molding machine. 
     
     
         38 . The method of  claim 30 , further comprising receiving the preform by a take-out plate of a post-mold cooling system to be cooled outside of the injection molding machine. 
     
     
         39 . The method of  claim 30 , further comprising, after performing the method of ejecting the preform from the preform molding system, returning the core half and the cavity half of the preform molding system to the mold closed configuration to begin another molding sequence.