Patent GB-689054-A (GB)
Title: Improvements in or relating to the production of yarns
IPC: D01G1/08
Filed: 1950-05-31
Abstract: <PICT:0689054/IV (a)/1> A yarn of or containing staple fibres is obtained by subjecting groups of continuous filaments to different degrees of stretch, short of the breaking-point, to give the filaments different breaking-point elongations, combining the stretched groups of filaments to form a bundle, and then subjecting the whole bundle of continuous filaments to a uniform further stretch sufficient to rupture at least a portion of the filaments. Preferably, the bundle of continuous filaments contains filaments with breaking-point elongations ranging from 6-20 per cent.  The bundle may also contain a group of filaments which are in a crimped condition, whereby the effective range of breaking-point elongations is considerably increased.  As shown, viscose is extruded through spinnerets 4, 5, 6 into a coagulating and regenerating bath 2, and the filaments are passed upwardly in three groups to godets 11, 12; 13, 14; 15, 16.  The peripheral speeds of the godets are individually controlled to permit adjustment of the stretch imparted to the threads withdrawn by the respective pairs of godets and to control the denier of the bundles of filaments withdrawn from the respective spinnerets. The metering pumps 7 may also be individually adjusted. The differently stretched groups of filaments are brought together and passed through the liquid-treating device 20 and then through the drying-device 26.  If desired, the dried yarn may then pass to a winding device and may subsequently be subjected to further stretching to cause rupture of at least a portion of the filaments. As shown, however, the dried yarn passes directly to a further stretching and drawing device comprising feed rolls 33 and draft rolls 34.  Guides 35, 36 may be traversed across the rolls to prevent grooving of the rolls.  Each pair of rolls may comprise a metal roll and a rubber covered roll which are urged together by a spring.  The yarn containing at least a portion of staple fibres is wound and twisted on bobbin 41.  Traverse rail 42 has a circular aperture 43 co-axial with spindle 40 and having a circular track 44 upon which rides the ring traveller 46. Softening agent may be fed to the cascade 1 so as to permit high stretching of the filaments passing from godet 15 to godet 16. Although the different groups of filaments are stretched to different degrees, the upper godets 12, 14, 16 may have the same peripheral speed.  The peripheral speed of cylinders 21 may be the same as that of godets 12-16, but the peripheral speed of the cylinders 27 of the dryer 26 is preferably somewhat less in order to permit relaxation.  One of the groups of freshly spun filaments may be delivered at an increased speed so that it is present in the composite yarn or bundle in an unstressed crimped condition. When the composite yarn is subjected to drawing, a high degree of stretch is required to rupture the crimped filaments, since the crimp must be removed before they are subjected to stress.  The range of fibre length in the final spun rayon yarn is thus increased.  The composite yarn containing discontinuous fibres may subsequently be wetted and then dried while permitting shrinkage. Differential shrinking effects are produced.  The components of the composite yarn exhibit differential dyeing affinities. Specifications 500,886 and 586,017 are referred to.