| 摘要 |
1301846 Seaming and finishing edges of non- metallic sheet material BRITISH VISQUEEN Ltd 14 Aug 1970 [8 Sept 1969] 44341/69 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 with a projecting edge portion 3 so shaped that it may, with its leading edge 5, 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, is characterized in that the blade 1 has its smallest cross-sectional area 4 at a point to one side of the crest of the projection. As shown, both the leading and trailing edges 5, 6, respectively, of the projection 3 are bevelled. The projection 3 extends into a slot between units 7 of a roller carrying a thermoplastic film web past the blade 1, the units 7 being separated by a spacer 8. Apertures 2 are provided for attachment of the blade 1 to a pair of low resistivity conductors. The neutral line of tension 10, i.e. the line through the ends of the blade about which the strains resulting from the attachment of the blade at itstwo ends, under longitudinal tension, are balanced, lies wholly within the body of the blade. The blade may be made of a nickelchrome alloy. 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 films. |
