Method for forming a blown plastic container

In a method of forming a blown thermoplastic article, the steps of:

• 1. introducing air under pressure through a first opening of an essentially tubular thermoplastic parison within a first mold cavity to expand the parison to a preform configuration intermediate that of the parison and the final article;
• 2. while the preform is in the first mold cavity, forming a second opening in the wall of the preform at a position other than that at which the air under pressure is introduced in Step (1);
• 3. closing said first opening in the preform;
• 4. enclosing the preform within a second blow mold cavity having a size and shape of a final article;
• and
• 5. introducing blow air under pressure into the preform through the second opening to expand the preform into the final article.

A method of forming a blown plastic container by the steps of:

• 1. closing the sections of a preform blow mold onto an elongated, essentially tubular blowable thermoplastic parison having an opening at one of its axial ends in alignment with a blow pin;
• 2. introducing blow air under pressure into the parison through said axial end opening to expand the parison to a preform having the configuration of the mold cavity defined by the sections of the preform blow mold;
• 3. during the performance of Step (2), expanding a portion of the thermoplastic preform material against a convex mold cavity surface to form a concave preform portion which is destined to form a convex portion of the blown plastic container;
• 4. forming an opening through approximately the center of the concave preform portion while the preform is in the preform mold;
• 5. removing the preform from the preform mold;
• 6. closing the sections of a final mold on the preform to pinch shut said axial end opening;
• 7. inserting a blow pin through the opening in the concave parison portion and introducing blow air under pressure through said blow pin (a) to expand the preform to the configuration of the cavity defined by the closed sections of the final mold and (b) to invert the concave preform portion into a convex container portion having a thickness substantially the same as the immediately adjacent container portion.

A method for forming a plurality of blown containers from a single tubular parison of thermoplastic material, comprising the steps of:

• 1. enclosing an essentially tubular, elongated blowable plastic parison within a preform mold having a plurality of interconnected, major, elongated cavities generally perpendicular to the longitudinal axis of the parison;
• 2. introducing blow air under pressure into the parison through an opening at one axial parison extremity and forming a preform by expanding the parison into the major cavities and against mold portions interconnecting those cavities, forming a plurality of preform segments (a) destined to form individual containers and (b) interconnected by integral, opposed pairs of joining portions;
• 3. while the preform mold is closed, forming an opening in the wall of each preform segment destined to form an individual container;
• 4. removing the preform from the preform mold;
• 5. closing the sections of a final blow mold on the preform (a) to pinch shut said opening at the one axial parison extremity, (b) to pinch shut and weld together portions of the corresponding, opposed joining portions and (c) to enclose each of the preform segments within an individual blow cavity;
• and
• 6. forming a plurality of individual blown containers by introducing blow air under pressure into each preform segment through that opening formed in the wall thereof by the performance of step (3).