| 摘要 |
A welding bar for laminating flexible thermoplastic sheets features a twin series of isosceles triangles standing proud of bar face and spaced so that the extension of the gap between alternate triangles is tangential to the end of the base of the next triangle in the series. Used esp. for making covers or pockets of e.g. polypropylene for office stationery etc. by ultrasonic welding, to produce a weld zone having a continuous longitudinal zig-zag rib. This rib braces the film against shrinkage effects typical of welds with straight but broken welds, e.g. one or two rows of parallel point or dash welds, which can tend to crease the papers enclosed. |
