Patent GB-637593-A (GB)
Title: Improvements in or relating to apparatus for stretching synthetic yarns, threads, filaments, foils and films
IPC: D02J1/22
Filed: 1947-05-15
Abstract: Apparatus for stretching synthetic yarns, threads, filaments, foils and films comprises means for feeding said materials under controlled tension including a roller, means for driving said roller, a second roller, mechanism connecting said driving means and said second <PICT:0637593/IV (a)/1> <PICT:0637593/IV (a)/2> roller for driving said second roller, a movable mounting for one of said rollers permitting relative movement between said rollers during rotation and stretching means for extending the synthetic materials including at least one stretching roller adapted to operate at a higher peripheral speed than said first roller, heating means being provided for heating one or more of said rollers.  In particular the apparatus is concerned with the processing of multifilament yarn, but monofils and threads, foils and films may also be treated.  As shown, a frame 10, Figs. 1 and 4, supports shafts 11, 12 and 13 carrying rollers 17, 18, 19 rotating therewith.  Roller 20 fixed to shaft 21 is driven from shaft 11 by a gear 22 fixed to shaft 21 and meshing with gear 23 fixed to shaft 11, the teeth ratio on gears 22 and 23 having the same ratio as the thread contacting peripheries of rollers 20 and 17, so that both rollers travel at the same peripheral speed. Shaft 21 is rotatably supported in arms 24 which in their turn are supported for movement on a pivot 26 mounted on a bracket 27 on the frame 10.  The roller 20 is so chosen in size and so positioned as to rest against roller 17 with a pressure of about one pound per square inch.  The relative movement of the rollers does not unmesh the gears.  The roller 17 may be heated to any desired temperature, preferably by internal heating, and similarly roller 20 may be heated, though it is preferred that it should not be.  A roller 31 mounted similar to roller 20 on a pivoted bracket is driven by gears meshing with gears on the shaft of roller 18, and having the same peripheral speed.  A further roller 28 is mounted for free rotation in a bearing 29 on the frame 10, and in order to maintain the threads separate is placed askew to 31. Roller 18, like roller 17, is heated, but to a somewhat higher temperature, roller 31, like roller 20 being unheated.  The peripheral speed of roller 18 is such as to give the preferred degree of stretch.  Rollers 31 and 18 are not in contact, but are mounted with a clearance slightly greater than the diameter of the yarn passing between them, which means that the roller 31 is always positively driven and is free to accommodate different yarn sizes, knots and other non-uniformities in the yarn.  A third pair of rollers 38 and 19 are similarly mounted, but roller 38 is surface driven from roller 19 but free to move away from it by a limited extent to accommodate different yarn sizes.  The stress on the yarn between rollers 38 and 19 is less than that between other rollers, so that roller 38 may press against roller 19 with sufficient pressure to prevent slippage without causing damage. Intermeshing gears as in previous cases allow roller 38 to be positively driven as are 20 and 31, but normally a positive drive is not required.  The peripheral speed of roller 19 is less than that of roller 18 and is such as to effect a degree of relaxation of the yarn.  In operation, yarn 45 is fed to rollers 20 and 17 at a moderate tension, heated on roller 17 to a relatively high temperature, then passed round the separator roller 28 and roller 31 a number of times to prevent slippage.  It is then passed between rollers 31 and 18 where it is stretched, and thence to roller 38, between rollers 38 and 19, round roller 19 and through the centring guide 44 to the collecting pin 43.  The apparatus may be used with polyacrylonitrile yarn in which the polymer contains at least 85 per cent acrylonitrile, nylon, cellulose acetate and the copolymer of 75 per cent vinyl acetate and 25 per cent vinyl chloride.  Any form of twister may be used for collecting. Preferably the rollers are driven by variable speed mechanism, but other suitable driving means may be employed.  The rollers may be heated by internally heated shells around which the rollers rotate, or heated metal shoes may be mounted concentrically above the rollers.  The movable rollers instead of being pivotally mounted may have a non-rotatable sliding connection with the shafts. Specifications 585,367 and 585,368 are referred to.