| 摘要 |
864,682. Welding by dielectric heating. DRITTENBASS, J. J. March 12, 1958 [March 12, 1957], No. 7974/58. Class 39(3). In welding portions of thermoplastic sheets 2, 6, the portions are placed between electrodes 1, 5, together with a buffer layer 3 consisting of impregnated organic fabric 4, and a heat resistant, electrically insulating sheet 7. Pressure between the electrodes is maintained after removal of a high frequency voltage but is released when the welded material has cooled sufficiently to become self-sustaining. The process is suitable for welding polyethylene, polypropylene, polyamide, polyester or polycarbonate, and the buffer material is preferably a P.V.C. having a dielectric loss of at least 0.1 and a high content of plasticizers which soften below the welding temperature. Closely woven cotton fabric is preferred for use with the buffer material, but wool or cellulose acetate may be used. The dielectric loss of the heat resistant sheet is preferably not greater than 0.1 and polyacetate is preferred for use as the sheet; a polyamide such as nylon, polyester, polyethylene and cellulose acetate are also specified. A range of from 20 to 200, preferably 40 to 120 megacycles, is specified for the electric field. The process is particularly suitable for welding thin-walled tubular materials, e.g. from 0.005 to 2.0 m.m. thick, which are filled with liquids and in which the weld is made across the width of the tube while the liquid is in contact with the area to be welded. |
