METHOD AND APPARATUS FOR MAKING A CONTAINER WITH A PRESSURE ACCOMODATING BASE

摘要

A container (1) having a body and a rim (3) defining an opening for the container, the container being made of a material such as PET or PEN, and being manufactured in a multi-step process. The first step comprises injection moulding a preform (15) which has a rim (3) formed at its mouth and a continuous body-forming portion (120) extending across the preform from the inner periphery (21) of the rim. In the final step, the hot preform is placed in a moulding cavity (61) of a blow moulding apparatus (60) with the preform being located by means of the rim (3). The body- forming portion (120) expands in the cavity to form the side walls (20) and bottom wall (2) of the container. The combination of the shape and thickness of the preform (15), the temperature profile of the preform after heating, and the shape of the moulding cavity (61) of the blow moulding apparatus cause the bottom wall (2) of the container to have a central rigid substantially-flat portion (4) and an annular relatively flexible portion (5) circumscribing the central rigid portion, the two portions being directly adjacent and integrally connected. The flexible portion (5) is arranged such that the central rigid portion (4) can be urged into any one of a continuum of positions between a first lowered position and a second raised position due to flexing of the flexible portion. Thus, the sealed container can accommodate changes in pressure within the container relative to atmospheric pressure.