| 摘要 |
978,302. Feeding webs. E. I. DU PONT DE NEMOURS & CO. May 3, 1961 [May 3, 1960], No. 16011/61. Heading B6B. Thermoplastic film 11, e.g. polyethylene terephthalate is passed over rollers, e.g. 13 and then around rollers 14, 15, 16, Fig. 1 (not shown), driven at slow speed and then over rollers 17, 18 driven at a higher speed, thereby stretching the web. The rollers 13, Fig. 2, are earthed at 24 while a wire electrode 23 is connected to a D.C. power supply 25. The web is held in contact with the roller 13 by electrostatic force. In a modification, a knife edge 27, Fig. 3 (not shown), replaces the electrodes 21, 22, Fig. 2. Alternatively, the electrodes may be highly conductive metal rods 28, 29, Fig. 4 (not shown), honed to a sharp point. The web 11, Fig. 5, is led over electrically conductive belts 31, 32, driven by rollers 33, 34, 35 and 36. A wire electrode 23 is connected to a D.C. power supply 25 while the roller 34 is earthed at 37. The belts 31, 32 diverge thereby transversely stretching the web which is held thereto by electrostatic force. The stretching may be carried out in an enclosure supplied with heated or cooled air. Specification 488,137, U.S.A. Specifications 1,548,864, 1,601,289 and 2,000,079 are referred to. |
