GB857829A - Improvements in or relating to processes of and apparatus for drawing synthetic filaments - Google Patents

Abstract

<PICT:0857829/IV(a)/1> <PICT:0857829/IV(a)/2> <PICT:0857829/IV(a)/3> <PICT:0857829/IV(a)/4> <PICT:0857829/IV(a)/5> <PICT:0857829/IV(a)/6> Solidified synthetic filaments are caused to travel through a drawing zone in a substantially fixed path, and are alternately stretched and relaxed in a cyclic manner in this zone for at least one cycle without breaking them while in the zone, the diameter of the filaments being maintained substantially uniform. As shown in Figs. 3A and 3B, a drive shaft 14 for roll 4 is driven at a constant speed and carries a circular gear wheel 24 in mesh with a circular gear wheel 26 carried on an idler shaft 15. The idler shaft also carries an elliptical gear wheel 25 in mesh with an elliptical gear 23 mounted on a drive shaft 13 for roll 3. Rotation of roll 4 to forward the bundle of filaments at a constant rate in the direction indicated by the arrows is therefore accompanied by rotation of roll 3 at a cyclically varying rate, thus providing a ratio of feeding (into the drawing zone) to forwarding that varies continually between a predetermined maximum and a predetermined minimum as the elliptical gears make each half revolution. This variation alternately stretches the filaments and allows them to relax. The peripheral speed of the forwarding rolls 4, 41 is mantained appreciably above the average peripheral speed of the feed rolls 3, 31 so that the filaments retain part of the increase length induced during each drawing cycle. As shown in Figs. 4A and 4B, the feeding rolls 3, 31 and forwarding rolls 4, 41 are attached to the respective roll shafts in the same way as in Figs. 3A and 3B. Forwarding shaft 14 carries the circular gear wheel 34, while a similar circular gear wheel is mounted on feeding shaft 13. The gear wheel 33 engages the idler gear wheel 37 on shaft 17, and it in turn meshes with gear wheel 38 on shaft 18, which also carries elliptical gear wheel 39. This elliptical gear wheel meshes with the elliptical gear wheel 35, mounted on shaft 19; this shaft also carries gear 36, in mesh with the gear wheel 34 on the output or forwarding shaft. This arrangement facilitates wider spacing of the pairs of feed and draw rolls. and simplifies substitution of such gears for different eccentricity ratios. It also permits variation in the relative sizes of the various circular gears or the rolls themselves. Instead of elliptical gears, cardioid, oval and generally "square" gears may be used. As shown in Figs. 5A and 5B, pulley 43 is substituted for the gear wheel on the feeding shaft, and there is no gearing connecting the feeding and forwarding shafts. The rate of withdrawal of the bundle of filaments from the drawing zone is fixed by the driving of a gear wheel 24 on the forwarding shaft by a gear 40 on a separate drive shaft 44. Above the pulley 43 on the feeding shaft, for which no drive is required, is a like pulley 45 fixed to a non-rotatable shaft 46 and connected to the pulley 43 by a belt 41. The belt is contacted by an eccentric 47 carried on the shaft 48, on which is also fixed a gear wheel 49 meshing with a drive gear wheel 52 fixedly mounted on a shaft 51. As the eccentric 47 rotates to press more firmly on the belt 41 the consequent tightening of the belt imposes a drag on roll 3, increasing the tension applied to the filaments in the drawing zone; and each complete revolution of the eccentric produces a complete cycle of alternate tightening and slackening of the belt and a corresponding cycle of drawing variation. The tow of treated filaments may then be forwarded into a zone in which they are continuously converted into staple fibres or a sliver of staple fibres. Staple yarn produced from filaments treated according to the invention has a loftier handle than conventional staple yarn.