| 摘要 |
623,736. Seaming rubber: moulding hollow plastic articles. STANDARD TELEPHONES & CABLES, Ltd., CLARKE, C. E. EADON-, and MICKLEWRIGHT, P. L. April 13, 1946, No. 11397. [Classes 70 and 87 (ii)] [Also in Groups VIII and XI] Hollow articles such as bulbs made from a plurality of sheets of thermo-plastic material such as rubber or polyvinyl chloride are edge-seamed by placing the sheets between electrodes one at least of which has a dividing and seaming edge, applying a high frequency alternating or pulsating electric potential for a sufficient period to soften the thermo-plastic material, removing or substantially reducing the potential and subsequently applying a mechanical pressure sufficient to form a seam. In a device for seaming rubber bulbs, 8 bottom electrodes 16 (Fig. 14) fixed to back plate 31 are covered with a sheet of unvulcanized rubber, two plugs per mould are then placed in position by means of dimpled template 33 and then another sheet of rubber and top electrode 32 placed in position. The current is switched on and after the rubber has softened the power is cut off and the electrodes brought together by pressure, firstly to consolidate the welded joint and then to cut away excess material. The electrodes are preferably chamfered on the inside. Additional electrode limbs may be provided to form pockets in articles such as air cushions. The frequency used is normally above 5 megacycles. The Provisional Specification describes also a similar process in which the heating is produced by any suitable means. |
