| 摘要 |
A roll pressed-flat around the rim of a beaker, is welded ultrasonically to itself in a process for producing a flat, squared-off edging zone round the opening. The container is of a fibrous material, esp. board or paper coated with a synthetic material on both surfaces. The rolled-over edge zone at the rim being produced by the forming mechanism, and pressed-flat in a subsequent operation. Pref. the roll is welded ultrasonically whilst it is held pressed flat by the press tools, and a tool may be used in which an ultrasonic generator is fitted. The tool may also be cooled. Used to provide a rim for a beaker of polyethylene coated paper contg. a fluid such as yoghurt, on which a cover can be welded, and which retains its form and appearance in spite of the possible penetration by moisture. At the same time the process of forming the flattened rim does not prejudice the appearance of the packaging material. |
