Rieter

Fiber guidance

Index

Fig. 47 – Guided and floating fibers in the drafting field

Fibers arriving for processing exhibit very considerable length variations. In a drafting field, they are therefore found in two conditions (see Fig. 47):

  • guided (a, b, c);
  • floating (d).

Fiber a, which has a greater length than the nip spacing and thus temporarily extends across both nip lines, is gripped by at least one roller pair at all times and is thus moved in a controlled fashion. As far as only fiber guidance is concerned, this fiber is optimal, but nevertheless causes disturbance. Firstly, when it is gripped at two places with different speeds, it may break; secondly, if it can resist the tension, it will be pulled out of one nip line, dragging neighboring fibers with it. This leads to fiber clumps and hence to unevenness. Fibers b, c, and d are shorter than the roller spacing. Upon entry into the drafting field, they will first move with speed v2 (as fiber b). When they finally pass into the nip region of the delivery roller, they will take on the speed v1, (as fiber c). In both cases, they are subject to controlled guidance and movement. Over a certain interval of their movement, however, i.e. after leaving the nip line of the entry roller pair and before reaching the nip of the delivery roller pair, they are without controlled guidance – they are floating (like fiber d).