| 摘要 |
680,450. Seaming non-metallic sheets. HEPWORTH, W., and IMPERIAL CHEMICAL INDUSTRIES, Ltd. Oct. 25, 1950. [Oct. 25, 1949] No. 27404/49. Class 42 (i). Two or more portions of polythene films are sealed together with two parallel seams having a space between them 1 to 10 millimetres wide. Each seal may be from 1 to 2 millimetres wide. The superposed portions of film may be drawn beneath a copper block having two ridges on the underside, and heated to a temperature between 200‹C and 300‹C, the weight of the block being partially supported to provide the correct pressure on the films. The films may be kept temporarily in tension but otherwise unsupported as they pass under the heated edges, by drawing them over a plate which is provided with a recess just below the said edges. Tubes and stockings may be made from long sheets of polythene film by passing them through a machine fitted with suitable rollers and the like to guide the film and fold it into a tube, its superposed edges then passing between a recessed plate and ridged heated block. |
