| 摘要 |
1,107,925. Seaming non-metallic sheet material. ST. REGIS PAPER CO. 14 Oct., 1966 [21 Jan., 1966], No. 45965/66. Heading B5K. Two opposed sheet surfaces are continuously bonded together by progressively drawing together at a nip 16 the two surfaces having disposed between them an inflated tubular strand 24 of molten thermoplastic resin which is fed between the sheet surfaces in advance of the nip 16. As shown, two webs 10, 11 or a folded single web of sheet material, e.g. paper, are continuously advanced by pinch rollers 13, 14 defining the nip 16 and covered with resilient material, e.g. rubber. The bonded web is further advanced by rollers or other means (not shown). A roll 17 guides the edge of the web 10 so that the webs 10, 11 converge towards the nip 16 at a small acute angle, e.g. 10-15 degrees. The strand 24 is extruded from an annular channel in a die 18, Fig. 3, this channel being formed between a nozzle 20 and a flange 22 of a conduit 21 which supplies an inert non-flammable gas, e.g. air. The thickness of the strand 24 may be changed by using a different die having a nozzle 20 and/or a flange 22 of different dimensions or by replacing the flange 22 with another flange. The gas pressure is adjustable by a valve 23 so that the strand 24 is inflated to the desired size. Specified thermoplastic resins are polymers of olefins, e.g. ethylene and propylene, vinyl chloride, vinyl acetate and vinylidene chloride. copolymers of these monomers and a blend of these resins. The resins may contain a plasticizer. The invention is applicable to forming the side seams of bags. |
