Patent GB-1091581-A (GB)
Title: Apparatus for the severing and welding of thermoplastic tube-films or composite foils of synthetic plastic for the fabrication of bags,sacks or like packaging containers
IPC: B29C65/18
Filed: 1965-01-13
Abstract: 1,091,581. Seaming non-metallic sheet material. M. LEHMACHER and H. LEHMACHER. Jan. 13, 1965 [June 3, 1964], No. 1486/65. Heading B5K. Apparatus for severing and welding thermoplastic film in flattened tubular form, in longitudinally folded form or in the form of superimposed webs comprises paired feed and withdrawal rolls (49), (50), Figs. 2 and 3 (not shown), and 47, respectively; a severing and welding knife 21 between clamping jaws 12, 14 and projecting above the jaws 14; hold-down means 27 operative when it is desired to weld the film on only one side of the sever; and a spring-loaded film retainer 29 to hold the film during severing and welding. In the embodiment shown, Fig. 1, welding and clamping jaws 12, 14 having welding surfaces 15a, 15b are secured to supports 10, 11, respectively, and extend transversely to the path of movement of the film. Each jaw 12, 14 is provided with a heating device in the form of a glow rod 17. A bar 20 is inserted in a slot 19 in the jaw 14 and carries the knife 21, the edge 22 of which may be either smooth or sawtoothed. The knife 21 may be stationary or may be oscillated longitudinally thereof. A movable band 24 of polytetrafluoroethylene extends across the surfaces 15a, 15b of the jaw 14 and around the bar 20. A similar band 24 passes over the surfaces 15a, 15b of the jaw 12 and is guided by a bar 25 in a groove 26 in the jaw 12. The hold-down means 27 in the form of a bar parallel to the jaw 12 and extending along the entire length thereof is mounted on the support 10 by arms 28. The film retainer gripper 29 in the form of a bar parallel to the hold-down 27 and also extending over the entire length of the jaw 12 is mounted on the support 10 by a screw 30, an eye 31 and a shank 32. A spring 36 constantly urges the gripper 29 downwardly. A counter support 43 having an inset rubber strip 44 is provided for the gripper 29. A bent support 40 is provided and has a tube 41 for cooling water situated in the side thereof directed toward the jaw 14. Feed rolls 49, 50 and a withdrawal conveyer band 45 passing around a roll 47 are provided. Guiding blades (51), (52), Figs. 2 and 3 (not shown), introduce the film (13) between the jaws 12, 14 and later lift it from the jaw 14. To form two seams with a cut therebetween the hold-down 27 is adjusted in height so as not to project beyond the surfaces 15a, 15b of the jaw 12, i.e. so as to be inoperative, Fig. 2 (not shown). During the approach of the jaws 12, 14 the film (13) is clamped by the gripper 29, which under the action of the spring 36 projects beyond the surfaces 15a, 15b of the jaw 12, against the support 43, is severed by the knife 21 and is welded on both sides of the cut. To form a cut and only one adjacent weld the hold-down 27 is adjusted in position to project beyond the surfaces 15a, 15b of the jaw 12, Fig. 3 (not shown). The hold-down 27 stretches the film (13) and presses it downwardly so that, after severing by the knife 21 but before the surfaces 15b close, the film is drawn away over the support 40 so that only the surfaces 15a produce a weld. The jaws 12, 14 are not heated if it is desired to cut, but not weld, the film.