Rieter

Forming a yarn with the aid of false twist

Index

As shown above, a fiber strand leaving the false-twist assembly consists of parallel, non-twisted fibers. This principle is normally unsuited to the task of giving strength to the yarn. In spite of this, the principle is now exploited to enable yarns to be spun, admittedly with a modification of the system. For example, the fiber strand fed to cylinders Z1, is allowed to enter the false-twist region (a) on a very broad basis, with the result that a greater or smaller proportion of edge fibers can escape the twisting action because of the broad spread of the strand upon entry.

In contrast to the description in the previous section, in Fig. 26, the strand entering the twist element is no longer fully twisted. The core – admittedly by far the greater proportion of the fibers – has twist, but the cover of fibers have either no twist or only a few turns. The opposing turns imparted by the twist element cancel all twist originally present, namely, that in the core, and give twist to all fibers that were originally untwisted, i.e., the envelope of fibers. These are wound around the core fibers so that a bundled yarn is obtained (Fig. 27).

Known processes operating on this principle are Rotofil by Du Pont (which has since been abandoned), Dref-3000 by Dr. Ernst Fehrer, Linz, and Murata Jet Spinning. The falsetwist principle has opened up previously unforeseen possibilities for forming yarn.

Fig. 26 – Spinning yarn by means of false twist

Fig. 27 – False twist (fasciated) yarn