| 摘要 |
A blow molding machine is provided with an external center pin so that blowing is accomplished without introducing a mechanical or rigid member within the preform and/or bottle. To do this, the blowing is done by introducing a fluid, preferably a gas such as air, into the preform to expand it. Outside of the preform, meanwhile, is the subject center pin or center rod which is located on the preform center line (axis) and near the middle of the preform bottom. The rod receives a gate disposed centrally on the bottom of the preform when the preform is expanded by the entering fluid. In this manner, the center part of the bottom of the preform is engaged by the center pin which thereafter keeps the preform on center as the blowing action continues. A process is disclosed of blowing using a compressed fluid alone inside the preform to expand the preform axially against the bias of an external resiliently biased center pin.
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