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Injection molding method and apparatus for ejecting a molded plastic article from a mold. A lifting structure and/or step is provided with a lifting portion which is configured to contact substantially one half of an end of the molded plastic article along a line substantially perpendicular to the l

Injection molding method and apparatus for ejecting a molded plastic article from a mold. A lifting structure and/or step is provided with a lifting portion which is configured to contact substantially one half of an end of the molded plastic article along a line substantially perpendicular to the lifting direction. Since the molded plastic article is lifted by its end, the article does not have to be solidified at its interior, thus allowing earlier removal of the article from the mold, reducing cycle time. A tapered surface forms an acute angle with respect to the lifting portion to form a tight seal with the mold, preventing leakage. Preferably, the neck ring engages only an outer circumferential portion of the molded plastic article during a majority of a mold opening stroke.

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What is claimed is: 1. Apparatus for ejecting a molded plastic article from a molding structure, comprising: a neck ring lifting structure having: a first portion configured to contact a threaded neck portion of a molded plastic article, a second portion configured to contact an end of the molded p

What is claimed is: 1. Apparatus for ejecting a molded plastic article from a molding structure, comprising: a neck ring lifting structure having: a first portion configured to contact a threaded neck portion of a molded plastic article, a second portion configured to contact an end of the molded plastic article along a line substantially perpendicular to the lifting direction, said second portion being configured so as to not contact an inner circumferential portion of the end of the molded plastic article; and a third portion disposed on an opposite side of said second portion from said first portion, said third portion and said second portion having a parting line therebetween substantially parallel to the lifting direction, said third portion being stepped from said second portion in a direction substantially parallel to the lifting direction. 2. Apparatus according to claim 1, wherein the plastic article comprises a preform mounted on a mold core. 3. Apparatus according to claim 2, wherein the preform has a neck portion having a ledge, a helical thread, and a circular sealing surface, said circular sealing surface having a circular engagement portion substantially perpendicular to the lifting direction, and wherein said lifting structure second portion is configured to engage substantially fifty percent of the circular engagement portion. 4. Apparatus according to claim 3, wherein said lifting structure has portions which respectively engage the preform neck portion ledge and the preform neck portion threads. 5. Apparatus according to claim 1, further comprising moving structure for moving said lifting structure in the lifting direction. 6. Apparatus according to claim 1, wherein said lifting structure first portion applies a shear force to the molded plastic article in the lifting direction, and wherein said lifting structure second portion applies a compressive force to the molded plastic article in the lifting direction. 7. Structure to eject a molded preform from a mold device, comprising: a neck ring lifting portion which is configured to (i) grip a threaded neck portion of the molded preform, and (ii) contact substantially one half of a sealing surface of the molded preform and apply a compressive force thereto; a neck ring sealing portion having a surface disposed below said neck ring lifting portion, said surface being disposed at an angle of substantially ninety degrees with respect to said neck ring lifting portion; and a movement device which causes relative movement between said lifting portion and the mold device to eject the molded preform from the mold device, said movement device causing said lifting portion to remain in contact with the end of the molded preform through a majority of an opening stroke. 8. Structure according to claim 7, wherein said movement device causes the relative movement before the molded preform is solidified. 9. Structure according to claim 8, wherein said movement device causes the relative movement after a skin portion at said end of the molded preform is solidified. 10. Structure according to claim 8, wherein said lifting portion includes: a threaded portion configured to engage a helical thread in the molded preform neck; a cylindrical portion configured to contact a surface of the molded preform which is substantially parallel with a direction of lifting; and an end portion configured to contact a surface of the molded preform which is substantially perpendicular to the direction of lifting. 11. Structure according to claim 10, wherein said end portion applies compressive force to the molded preform, and wherein said threaded portion applies both compressive force and shear force to the molded preform. 12. Structure according to claim 7, wherein said lifting portion is disposed in a neck ring. 13. Structure according to claim 7, wherein said lifting portion applies both a shear force and the compressive force to the molded preform. 14. An injection molding machine, comprising: a mold cavity configured to receive a molten material and form it into a molded preform; a mold core configured to engage the molded preform; and neck ring ejecting structure configured to eject the molded preform from said mold core by applying a compressive force to an end of the molded preform, said neck ring structure being configured to (i) grip a helical threaded portion in a neck area of the molded preform, and (ii) contact substantially one half of an outer circumferential portion of a sealing portion of the molded preform throughout a majority of an opening stroke, said neck ring ejecting structure having (i) a lifting surface substantially perpendicular to a lifting direction, and (ii) a sealing surface disposed substantially parallel to the lifting direction, said neck ring lifting surface and said mold core being configured to provide a preform dominant sealing surface and a preform subordinate sealing surface that are stepped with respect to each other in the lifting direction. 15. A method for ejecting a molded plastic preform from a molding structure, comprising the steps of: engaging a threaded portion on a circular neck portion of the molded plastic preform; contacting substantially fifty percent of an end portion of a circular neck portion of the molded plastic preform with a lifting surface disposed substantially perpendicular to the ejecting direction so as to form a stepped sealing surface on an open end of the preform; and applying a compressive force to the end portion of the neck portion of the molded plastic preform throughout a majority of an opening stroke to eject the molded plastic preform from the molding structure. 16. A method according to claim 15, wherein the contacting step and the applying step are performed by a neck ring. 17. A method according to claim 16, wherein the neck ring also applies a shear force to the molded plastic preform during the applying step. 18. A method according to claim 15, wherein the contacting step comprises the step of contacting a tapered portion of a mold core with a tapered surface that forms an acute angle with respect to the lifting surface. 19. A method according to claim 15, wherein the applying step comprises the step of applying the compressive force while an interior portion of the molded plastic preform is nonsolid. 20. A method according to claim 15, wherein the contacting at least fifty percent step comprises the step of contacting at least fifty percent of an outer circumferential portion of a circular portion of the open end of the preform.