Rieter

Self-twist

Index

If the strand is passed forward (by the delivery movement) between rubbing rollers (N), which are also moving to and fro, then it will be continuously twisted with alternating Z- and S- twist over successive short portions (Fig. 67 and Fig. 68). The counter-torque created in the yarn will, however, eliminate this twist immediately after the yarn leaves the roller nipping line. If – instead of one strand – two fiber strands are passed through while arranged parallel and very close to each other, then the counter-torque can no longer operate solely on one yarn. It must operate on both, and causes twisting of the two threads around each other. A plied thread is created with continually varying twist direction – Z-twist where S-twist is present in both yarns and S-twist where the yarns had originally Z-twist. In most cases, the strength of the self-twist thread made in this way is not quite sufficient because of the untwisted pieces between the twisted portions – it must be additionally twisted subsequently.

In worsted spinning, its sole field of application, self-twist spinning (also known as Repco spinning) has been in use for several years, although not on a very large scale.

Fig. 67 – Self-twist

Fig. 68 – Forming a yarn by means of self-twist