WAVE-TYPE PRESSURE COMPENSATING BASES FOR POLYMERIC CONTAINERS

摘要

A plastic container having a sidewall defining a chamber and having a first end and a second end and an opening at the first end into the chamber. A base of the container extends from the sidewall and closes the second end, the base having an outer perimeter portion defining a support structure, an axially inwardly extending perimeter wall spaced radially inwardly from the support structure forming an angle with a horizontal line of greater than about 80°, a centrally disposed pushup section in the shape of an axially inwardly extending truncated cone, and a toroidal-shaped channel circumscribing and connecting the perimeter wall to the pushup section. The toroidal-shaped channel has a surface that is asymmetrical about a central axis of the container when the container is under static pressure conditions.

主权项

1. A method for forming a polymeric container comprising:
providing a blow mold having a chamber and an opening into the chamber at one end, the blow mold being moveable between an open position and a closed position, a pushup member is positioned in the opening to close the chamber, the pushup member having a surface extending into the chamber for defining a bottom wall of the container; inserting a preform within the blow mold; and blowing the preform against the chamber to form a container having a base, the base having an outer perimeter portion defining a support structure, an axially inwardly extending perimeter wall spaced radially inwardly from the support structure forming an angle with a horizontal line of less than about 90°, and a pressure compensating panel closing an end of the perimeter wall, the pressure compensating panel being moveable along an axis of the container from a first position where a central portion of the panel is below a top portion of the perimeter wall to a second position where the central portion is above the top portion of the perimeter wall to change the volume of the container, and a plurality of circumferentially spaced radial grooves on the panel, the grooves comprised of thinned lines in the panel, creating hinges extending through a partial thickness of the panel with no interruption in the surface of the panel on an opposite surface of the grooves, and adding flexibility to the panel.