The indicatication of the false-twist unit speed is carried out when several of the twistrs are driven by an endless belt of which the control pulley shaft exhibits equispaced markings. The latter are sensed by photoelectric cells or electromagnetic pulse detection. The marking disc can be in the form of a gear or a perforated disc. Instead of perforations, the disc may exhibit dark and light shades for photodetection. The system ensures a high measurement accuracy, since the speed of the gear, and thus the number of counted pulses per unit of time depends on the peripheral velocity of the drive belt turning all false twist heads at the same speed. The connection of the belt driving pulley to the main drive of the texturizing frame ensures that the yarn delivery rate changes with the belt velocity, and thus with the speed of the false-twist heads.
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