GB1427748A - Reducing internal pressures of sealed containers - Google Patents

Abstract

1427748 Reducing pressures within sealed containers; endless conveyers SWISS ALUMINIUM Ltd 18 May 1973 [19 May 1972] 23822/73 Headings B8C and B8A A method of reducing the internal pressure of a container 12 filled with contents such as cream and of the kind comprising a lid 14 which is hermetically-sealed to a body 16 which is formed with an inwardly-domed base 18 of resilient, but plastically deformable material, comprises the steps of partially encasing the container with one or more, rigid members in such a manner that at least the lid is covered, the or each of the rigid members lying substantially directly against the outer surface of the container, then heating the container so that the pressure acting therein increases to such an extent that the base of the container is caused to deform plastically by flexing outwardly, thereby increasing the internal volume of the container, and finally allowing the container to cool to ambient atmospheric temperature. The container base 18, which is preferably integrally formed with the body 12, is made, e.g. of relatively thick aluminium foil or, of a semi-hard plastics material. As shown, filled containers are fed successively from a lidsealing machine 26 into corresponding recesses 36 in blocks 34 which form the individual links 32 of an endless conveyer 24 each recess 36 having a peripheral groove 38 to receive the rim 20 of a container and the base of the block 34 being adapted to limit the outward movement of the container base 18 and having an exhaust opening 44. A flap 50, pivoted at 48 to each block 34, is moved downwardly against the bias of a coil spring 54 by spring-loaded rollers 66 to contact and completely cover the lid of the container as the respective block passes through a heating chamber 30. While being conveyed through the heating chamber 30, which has rubber end-curtains 68, 70, the containers are heated to a temperature of over 50‹ C. to deform the container bases 18 outwardly the bases 42 of the blocks 34 limiting the outward deformation of the bases 18 which assume substantially planar form. A single link 32 could be constructed to carry several containers 12 side-by-side. Due to the reduced pressure within the containers the lid 14 may flex inwardly slightly. In a modification, Fig. 4, not shown, each link comprises a base-plate (42) which is connected to a separate block (34) by adjustable distance pieces which each comprise sets of individually removable rings (56) and an associated bolt (58).