Patent GB-1161902-A (GB)
Title: Improvements in or relating to the Bonding of Thermoplastic Surfaces.
Inventor: BAHLSEN WERNER
IPC: B29C65/74
Filed: 1966-07-12
Abstract: 1,161,902. Seaming non-metallic sheet materials; laminating. W. BAHLSEN. 12 July, 1966 [12 July, 1965], No. 7088/69. Divided out of 1,161,901. Headings B5K and B5N. [Also in Division B8] In a method of bonding together, by heat and pressure, two sheet materials, at least one of which has a thermoplastic surface, the necessary temperature for bonding is produced by eddy currents induced in a metal auxiliary heating member, which may form one of the sheet materials, in contact with the thermoplastic coating, and the materials to be bonded are subjected to moving pressure members which generate the alternating magnetic field to induce the eddy currents in the metal foil, the pressure members being moved along at the same speed as the webs or having a peripheral speed corresponding to the speed of travel of the webs. Preferably, the sheets to be bonded consist of paper, cardboard or metal foil coated with a thermoplastic synthetic resin or of thermoplastic films. The metal auxiliary heating member may be in the form of an endless belt band, wire or wire mesh positioned between the webs to be joined or may be one of the webs. In one embodiment, Fig. 3, a web of paper, cardboard or plastics film is laminated to a metal foil web, one or both of the webs being coated with a thermoplastic synthetic resin, by passage between smooth-surface rollers 407, 408, the journals 411, 412, 413, 414 of which are arranged at a short distance from iron cores 415, 416 having windings 417, 418 connected to a medium or low frequency generator 419. The magnetic flux is indicated by arrows. The metal foil becomes heated and the pressure applied by the rollers 407, 408 bonds the webs together. The circumferential speed of the rollers 407, 408 is adjusted so that it is just sufficient to effect adherence. If it is desired to bond the webs in localized areas only, the rollers 407, 408 are provided with suitable projections and recesses. In a modification, Figs. 4-7 (all not shown), filled containers (424) previously formed in a continuous web (425) are closed by an aluminium foil (428). The containers are accommodated in cavities (421) defined by ribs (422), (423) in the lower pressing roller (420) and the upper roller may be provided with co-operating ribs or may be smooth. After bonding between ribs (427) and the foil (428), individual containers are punched out. To bond two webs together at transversely spaced intervals, one or both rollers is or are provided with ribs (430), Fig. 8 (not shown), which extend axially thereof. To produce an undulating effect on one of the webs to be bonded, two such rollers are provided and driven at different speeds. To bond two webs together along longitudinal strips, a plurality of pairs of flanged rollers, Fig. 9, are mounted across the webs and at least one roller of each pair is provided with a winding 432, 433 connected to a generator. Arrows indicate the magnetic flux. Two webs may be bonded first longitudinally by the rollers of Fig. 9 and then transversely by the rollers of Fig. 8. In a further embodiment, Figs. 12 and 13, the webs 460, 461 are bonded as they pass between upper iron parts 448, 449, 450 and lower iron parts 451, 452, 453 disposed on endless belts 454, 457. At least one magnet 446, 446a, 446b provided with a winding 447 connected to a generator is mounted so that the long arms thereof are disposed over the parts 448, 449, 450 and under the parts 451, 452, 453. In another embodiment, Fig. 14, the webs 462 pass between an endless belt 463 made up of U-shaped magnets 465, 466, 467, 468 having windings 469, 470, 471, 472 and an endless belt 464 made up of U-shaped iron parts 473, 473a, 473b, 473c to form transverse seams. The webs 462 then pass between an endless belt 474 formed of magnets 476, 477, 478, 479 having windings 480, 481, 482, 483 and an endless belt 475 formed of iron parts 484, 485, 486, 487 to form longitudinal seams.