| 摘要 |
1301848 Seaming and finishing edges of non- metallic sheet material BRITISH VISQUEEN Ltd 14 Aug 1970 [8 Sept 1969] 44343/69 Headings B5A and B5K [Also in Division D1] A resistance-heated blade 1 for simultaneously slitting an advancing thermoplastic web and sealing the slit edges provided on one of its longer sides with a projecting edge portion 3 so shaped that it may intersect the path of the web when the blade is held perpendicular thereto and with its flat faces parallel to the direction of travel of the web, the blade being cut away behind the projection 3 so as to have its smallest cross-sectional area 4 in the vicinity of the projection 3, and being apertured at 2 at its two ends for attachment to a pair of conductors, is characterized in that the contour of the blade 1 and the positions of the apertures 2 are such that the neutral line of tension 5, i.e. the line through the ends of the blade about which the strains resulting from the attachment of the blade at its two ends, under longitudinal tension are balanced, lies wholly within the body of the blade. The blade 1 may have its smallest cross sectional area 4 in advance of the crest of the projection 3 in relation to the travelling web, as shown, or at the crest of the projection 3. The blade may be used for dividing flattened tubular films into at least two sections or for slitting a single thermoplastic layer, e.g. to prevent fraying of cut edges of a woven fabric or to form bead edges to strengthen the cut edges of slit film. |
