| 摘要 |
1426814 Seaming non-metallic sheet material WAVIN BV 7 March 1973 [15 March 1972] 11212/73 Heading B5K In the manufacture of thermoplastic bags, longitudinally spaced transverse seals are made in a tubular thermoplastic film 3 by feeding the film 3 longitudinally in a substantially untensioned condition past a heating member 10 to plasticize the film in zones where the transverse seals are to be formed and passing the film 3, after leaving the member 10, between two pressure rollers 12, 13 to effect sealing. The film 3 is fed from a roll 1 bearing on rotatable rubber rollers 2 by driven rollers 4. Transverse perforations are made by a rotatable drum 5 having projections thereon and cooperating with a backing roller 6. The sealing members 10 are mounted in a metal surface drum 8 and are thermally insulated therefrom. Preferably, each member 10 is made of copper covered with polytetrafluoroethylene. Foam rubber rollers 7, 9 maintain the film 3 in contact with the roller 8 but do not compress it thereagainst. The roller 12 is provided with a cooling spiral 18 and a lever 19 is provided to press the roller 13 against the roller 12. The rollers 4 rotate slightly faster than the rollers 12, 13 so that the film 3 is not tensioned as it passes around the drum 8. A tension roller 20 acted on by a spring 21 draws the film slippingly from between the rollers 12, 13 and then the film passes between rollers 14, 15 driven at the same speed as the rollers 4. Subsequently, the film 3 passes through a printing machine 18a, is doubled longitudinally by a folding triangle 16 and is wound on a device 17. |
