| 摘要 |
1,200,347. Seaming non-metallic sheet material. WINDMOLLER & HOLSCHER. 25 Oct., 1967 [6 Dec., 1966], No. 48554/67. Heading B5K. Apparatus for heat sealing at least two superimposed thermoplastic sheets with the simultaneous formation of a weakened tear line in the region of the heat-sealed seam comprises a heatsealing jaw 1 provided with an insulating layer 2 over which an impulse heating strip 3 is stretched, an unheated backing jaw 5 carrying a resilient abutment layer 6, e.g. of silicone rubber, and a thin bead element 8 having a portion which protrudes from the engaging surface of one of the jaws, this portion being formed with closely-spaced interruptions and the bead element 8 being connected to the jaw at least in the region of these interruptions. In one embodiment, Fig. 1, the jaws 1, 5 are covered by tapes 4, 7 of "non-stick" material, e.g. polytetrafluoroethylene, which are each wound on two rolls one on each side of the jaws so that the tape is adjustable for wear. The bead element is formed by one of a number of parallel running stitchlines 8 in the tape 7 and is positioned so that the weakened tear line is formed along approximately the centre line of the seam. The stitchlines 8 may be formed as single or double stitchlines and may consist of a ply yarn or a fine wire, e.g. of nickel-chromium steel or silver. In a modification, Figs. 7-9 (all not shown), a triangular cross-section wire (14) is embedded in the tape 7 and its sharp protruding edge is formed with closely spaced notches (15). In another embodiment, Fig. 2, the tape 7 is omitted and the jaw 5 is provided with a polytetrafluoroethylene strip 10 slidably inserted in grooves 9 over the layer 6. |
