| 摘要 |
1,120,701. Making bags with tear strings; seaming non-metallic sheet material. DOW CHEMICAL CO. 18 Oot., 1965 [26 Oct., 1964], No. 44079/65. Headings B5D and B5K. [Also in Division B8] A tear string is secured to the heat-sealable thermoplastic surface of a web 11, (Fig. 1), by heating a narrow strip of the web and pressing the strip in place and the web is then welded to itself or to a further web to form a flat bag before the resin at the tear string has hardened. The pressure may be applied by a heated head 22, (Fig. 1), pressed by a pneumatic ram 28 against a portion of the material supported on an anvil 12. The tear string, which may be a single filament or a yarn of cotton, rayon or nylon is fed from a bobbin 19 through a guide 21 which can be adjusted along guides 16. The bag may be formed by superposing a second sheet on the sheet with the tear string, or by folding the sheet in two, and heat-sealing along the open edges. A notch (38), (Figs. 3 and 4, not shown) near the tear string may be cut by machine. |
