Imparting strength by false twist


Fig. 65 – Forming a yarn by means of false twist

As described, the strand leaving the false-twist unit consists of parallel, untwisted fibers (Fig. 65). This twist principle is therefore normally unsuitable for imparting strength to a yarn. Nevertheless, threads are currently spun by this process - but with modification of the system. For example, the fiber strand fed by cylinder Z1 has to be very wide as it passes into false-twist zone a. The result is that, owing to this substantial width, a considerable number of edge fibers can avoid the twisting effect.

In contrast to the operation described in the preceding section, the fiber strand entering the twisting element is no longer fully twisted. Instead, only the core is twisted, and the sheath fibers have no twist or only a low twist level, with the core still representing by far the greater part of the fibers. The opposite twist now imparted by the twisting element cancels all twist in the newly arriving strand, in particular the turns in the core.

Twist in the opposite direction is, however, imparted to all those fibers which were untwisted on arrival, i.e. the fibers in the sheath.

These are now wrapped around the core fibers so that a bundled yarn is produced. The Murata jet system operates in a similar, but not completely identical fashion and there are slightly greater differences in the Dref 3 system.