GB1083578A - Improvements in apparatus for closing open-topped packaging containers with thermoplastic sheet material - Google Patents

Abstract

1,083,578. Sealing package closures. PARNALL & SONS Ltd. Sept. 2, 1964 [Sept. 5, 1963], No. 35210/63. Heading B8C. Apparatus for covering open-topped containers includes a press comprising two parts, one having a cavity to receive the body and a shoulder to support the mouth flange of a filled container; a frame to clamp the margins of a horizontal thermoplastic sheet overlying the container between two opposed faces and a sealing head which presses the sheet down on to the flange, stretching the sheet over any projection of the contents above the flange and sealing it to the latter. A fixed bed plate 6 has a cavity 7 and shoulder 9 to receive the container 8 having goods 27 projecting above the lip 10. A ram cylinder 12, supported by a fixed part of the press, carries push rods 14 and posts 17, 18, the posts 17 carrying an upper frame member 19 and, on their lower parts 22, a lower frame 23 urged towards the member 19 by springs 24. The frame 23 touches the lower ends of the rods 14 which thus hold the frames apart to receive a web 25 of thermoplastic material therebetween. The posts 18 carry a hollow sealing head 26 downwardly urged by springs 31 and an impulse heated ring 30 which overlies the flange of the container 8. Downward movement of the piston rod causes the frame 23 to lose contact with the rods 14 and the film 25 to be gripped by the frames 19, 23. As the piston rod descends further, an area 28 of the film covers the goods 27, the member 23 touches the bedplate 6 (Fig. 5, not shown) and the ring 30 presses the film upon the flange 10, thus stretching the film over the goods. The ring 30 is impulse heated to seal the film to the flange and it may sever the film round the perimeter of the ring. In an alternative embodiment, not shown, a single frame may clamp the sheet against a support such as 6, the sealing ring stretching the sheet about; the container before sealing.