Patent GB-1132965-A (GB)
Title: Improvements in the manufacture of patterns of slits in a web
IPC: B26F1/20
Filed: 1964-12-01
Abstract: 1,132,965. Cutting webs; folding edges of sheet material. P. EISLER. 1 Dec., 1965 [1 Dec., 1964], No. 48780/64. Headings B4B and B5K. A method of producing interrupted longitudinal slits of variable length in a web includes the steps of feeding the web longitudinally through a cutting station, and, while the web is in motion through the station, imparting a repeated cycle of movements to a knife having a cutting edge with at least one gap therein, said cycle including a movement of the knife in fixed ratio to the movement of the web while the gap in the cutting edge is passing over the web and a movement of the web controllable independently of the movement of the web while the cutting edge makes an incision in the web. The fixed ratio is preferably unity. During the incision phase, at least one acceleration and one deceleration are preferably included in the movement of the knife. The web may be reinforced prior to slitting by lamination to a material e.g. paper or a film of synthetic material, or by a coating of lacquer or varnish. The web is preferably held under tension during slitting. The web may be lubricated prior to slitting. Apparatus for performing the method comprises gapped rotary knives 321 extending into grooves 326 in a roller 327, the gaps in the knives being staggered relatively to one another along a non-circular shaft 319. The web 333 to be slit is fed by means of crimping rollers 304 past tensioning bars 341 and around rollers 327, 334. The knives are exchangeably mounted on the shaft 319 and held in position by spring clips 323. The knives are guided during threading on the shaft 319 by guide rods 328 and are retained in their correct planes by guide rods 331. The drive to the shaft 319 is geared to the drive for the rollers 304, the gearing including a coupling comprising two cranks 308, 317 the crank pin 316 of the crank 317 engaging a groove in the crank 308. The gearing comprises a continuously variable gear 305 and a change speed gear 318 having a multiplying ratio of 2n where n is the number of gaps in each knife. The gear 305 is mounted on a slide 309 movable along slideways 311. The margins of the slits in the web are folded through 90 degrees by coaction of the knives and the roller 327 as in Specification 1,020,311 and the folding is continued and maintained, by means of ploughs 336 and/or air jets delivered by nozzles 338, and completed to convert the slits into slots, by means of shoes 337 or air jets. If desired, the ploughs and shoes may be swung out of action and the air jets rendered inoperative. The interruptions of alternate series of slots may be longitudinally staggered to form a meander pattern. In a modification (Figs. 3 and 4), the knives may be made of two semi-circular halves angularly adjustable relative to one another to vary the length of the interruptions in relation to the length of the slits. In other modifications (Figs. 10 and 11), the knife shaft may be of helical form and made flexible in torsion so that the interruptions between the slits extend across lines inclined to a line perpendicular to the length and direction of movement of the web.