Rieter

Operating principle

Index

If a fiber strand (Fig. 64) is held by two clamps K1 and K2 at two spaced points and is twisted at some point in between, the strand will take up the same number of turns on each side of the twisting element (T), but with opposite  twist directions. In the example above, Z-twist is shown on the right and S-twist on the left (seen vertically). If the clamps are replaced by rotating cylinders (Z1 and Z2) and the yarn is made to run past the cylinders during twisting, the same thing happens – but the conditions are now different. With a stationary thread, as first assumed, both thread portions were untwisted at the start. With a running thread, however, the thread entering path section b is already twisted with the number of turns imparted to it in path section a. In the given example these are turns of Z-twist.

The twisting element, however, is creating S-twist in the left-hand path section, so that each turn of Z-twist imparted a is cancelled by a turn of S-twist imparted in the second section b. The strand therefore never has any twist between the twisting element and the delivery cylinder. In a false-twist device, twist is found only between the infeed cylinder and the twisting element. This principle is used in false-twist texturing.

Fig. 64 – Creation of false twist (above) in stationary condition; (beneath) in through-flow condition