초록 ▼

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. Outsi

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.

대표청구항 ▼

In a machine for making a plastic bottle of resin by blow molding within a blow mold assembly an elongated hollow tubular preform which is shorter than said bottle and that has one end open and the other end closed, the blow mold assembly being openable and comprising at least one mold which is open

In a machine for making a plastic bottle of resin by blow molding within a blow mold assembly an elongated hollow tubular preform which is shorter than said bottle and that has one end open and the other end closed, the blow mold assembly being openable and comprising at least one mold which is openable and which assembles to form along a substantially vertical axis a cavity shaped substantially like the bottle and providing for expansion of the preform along said axis and in a radial direction substantially normal thereto, called the hoop direction, the open end of the preform being held substantially on said axis by suspension of the preform with its closed end down from a neck ring which also cooperates with the blow mold assembly to seal the neck end of the cavity, the machine also having a blow ring means for entering the open end of the preform and directing blowing fluid into the preform to form a bottle by expanding same into engagement with the mold walls defining said cavity, there being no mandrel or core supporting the preform nor any mechanical element that enters the preform to engage the interior bottom portion thereof, the improvement that comprises a center pin movably supported in the bottle bottom of said cavity; an upwardly facing shaped upper face on said center pin for engaging the closed end of said preform and contoured at its periphery to form with said mold at the bottom of said mold cavity a bottle bottom molding surface; support means coupled to an end of and supporting said center pin for reciprocable motion in the direction of said axis while keeping said pin located substantially on said axis; means disposed beneath said center pin and support means and coupled to said support means for reciprocating said support means and center pin on said axis as aforesaid said center pin, support means, and means for reciprocating being so arranged that said shaped upper face moves between a first lower position where said shaped upper face is in register with adjacent mold cavity surfaces to define at least a part of the bottle bottom and a second upper position along said axis toward said open end where said shaped upper face is spaced apart from the closed end of the preform and is engagable during blowing by the preform; and said means for reciprocating further including means to drive said center pin and support means between said first and second positions and to bias said center pin in a direction opposite to movement from said second to said first position with a force insufficient to resist expansion of said preform once it comes into contact with said shaped upper face during blowing of said bottle.