Method of making blown plastic containers

Claim 2

In a method of making a blown plastic container or the like, the steps of enclosing a thermoplastic parison in a pre-form blow mold cavity which includes a peripheral groove in the region corresponding to an end portion of the parison, blow molding the parison interriorly of the blow mold cavity to a pre-form configuration including a convex end circumscribed by a peripheral rib formed by the cavity groove, transferring the pre-form to final blow mold cavity having telescopically movable mold sections, telescopically moving the mold sections to (1) to deform the convex pre-form end to a concave configuration and(2) collapse the rib upon itself beneath the level of the deforming pre-form end, and then blowing the pre-form interiorly of the telescopically moved mold sections to form the blown plastic container.

Claim 3

In a method of forming a blown plastic article having a concave base, the steps of positioning an axially elongated plastic parison between the sections of a sectional pre-form blow mold; closing the pre-form blow mold sections on the parison to enclose the parison in a pre-form cavity; blow molding the parison in the pre-form cavity to a pre-form havig a convex base; opening the pre-form mold sections; transferring the pre-form to a position between the sections of a final blow mold including axially movable die sections having mating convex forming surfaces; closing the final mold sections on the pre-form (a) to enclose the pre-form in a final mold cavity defined by the blow mold sections and to (b) to axially align the convex base of the pre-form with the convex die forming surfaces; after closure of the final mold sections, axially moving the convex die surfaces to engage and deform only the center portion of the pre-form convex base into a concave pre-form base circumscribed by an annular support surface; and then blow molding the pre-form into the configuration of the final blow mold cavity.

Claim 4

In a method of forming a blown plastic article having a concave base, the steps of positioning an axially elongated plastic parison between the sections of a sectional pre-form blow mold; closing the pre-form blow mold sections on the parison to enclose the parison in a pre-form cavity; blow molding the parison in the pre-form cavity to a pre-form havig a convex base; opening the pre-form mold sections; transferring the pre-form to a position between the sections of a final blow mold including axially movable die sections having mating convex forming surfaces; closing the final mold sections on the pre-form (a) to enclose the pre-form in a final mold cavity defined by the blow mold sections and to (b) to axially align the convex base of the pre-form with the convex die forming surfaces; after closure of the final mold sections, axially moving the convex die surfaces to engage and deform only the center portion of the pre-form convex base into a concave pre-form base circumscribed by an annular support surface; and then blow molding the pre-form into the configuration of the final blow mold cavity.