Pressure compensating bases for polymeric containers

A plastic container comprising:

• a sidewall defining a chamber and having a first and second end and an opening at the first end into the chamber;
• a base extending from the sidewall and closing 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 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 (i) a first position where a central portion of the panel is below a top portion of the perimeter wall to (ii) a second position where the central portion is above the top portion of the perimeter wall to change the volume of the container to (iii) a third position where the panel is disposed axially outwardly from the first position, the panel having a thickness from about 30% to about 60% thinner than the thickness of the sidewall;
• 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.

A plastic container comprising:

• a sidewall being devoid of pressure compensating features, defining a chamber, and having a first and second end and an opening at the first end into the chamber;
• a base extending from the sidewall and closing 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 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 (i) a first position where a central portion of the panel is below a top portion of the perimeter wall to (ii) a second position where the central portion is above the top portion of the perimeter wall to change the volume of the container to (iii) a third position where the panel is disposed axially outwardly from the first position, the panel being always disposed within the chamber and having a thickness from about 30% to about 60% thinner than the thickness of the sidewall;
• a first circumferential groove on the panel;
• 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.