Container base with releaved corner geometry

Abstract

A plastic container having a longitudinal axis, a finish adapted to receive a closure for sealing the container, a neck situated below and supporting the finish, a shoulder portion situated below the neck, a body portion extending downward from the shoulder portion, and a base. The base has a central portion and a plurality of edges and corners defining a generally polygonal base perimeter. Downwardly extending contact portions are located along the edges of the base perimeter, a lowermost surface of the contact portions defining a common plane perpendicular to the container longitudinal axis. Each of the corners of the base includes a channel upwardly offset with respect to the common plane, each channel extending between the base central portion and the base perimeter.

Description

BACKGROUND OF THE INVENTION [0001] The present invention relates to blow-molded containers of thermoplastic materials, which are generally biaxially oriented, such as polyethylene terephthalate. The invention particularly relates to improvements in container design to achieve a stable container that accurately reflects the desired container geometry, preferably using less polymer than other containers of similar overall geometry. The invention more particularly relates to containers having bases that are polygonal rather than circular when viewed in plan view. Polygonal as used herein can mean triangular, rectangular including square, pentagonal, hexagonal, octagonal, etc., unless the context of the use of the term prevents such scope. [0002] U.S. Pat. No. 5,064,081 discloses a pressure resistant polygonal bottle-shaped container having a polygonal bottom. The center of the bottom wall of the container is inversely bent inwardly of the container, and reinforcing ribs are formed in t...

AI Technical Summary

Benefits of technology

[0007] The vertical offset of the upper surface of each corner can reduce the residual stress in that area of the container. The reduction in residual stress is manifest by improved corner definition and reduced warping of the container, particularly in hot-fill containers. Other features of containers of the present invention and the corresponding advantages of those features will be come apparent from the following discussion of a preferred embodiment of the present invention, exemplifying the best mode of practicing the present invention, which is illustrated in the accompanying drawings. The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. Moreover, in the figures, like referenced numerals designate corresponding parts throughout the different views.

Problems solved by technology

It has been observed, however, that the corners of polygonal bases, being situated farthest from the axis of the container, experience higher residual stress due to the significant differences in the stretch that the polymer experiences during blow molding of the container.

This residual stress can cause warping of the seating ring and other structural problems, particularly when the weight of polymer used to form the container is reduced.

Images