Rieter

Noil elimination with backward feed

Index

During the detaching stage the nippers are located at their closest spacing relative to the detaching rollers (Fig. 13), which draw off all fibers extending to the nip line, i.e. all fibers longer than E. This length E can be entered in the staple diagram (Fig. 14) as a line m-n. All fibers to the left of the line m-n pass into the combed sliver (hatched area AmnC).

As the nippers retract towards the combs, the feed roller shifts the fiber fringe (initially with length E) forward through feed amount S. The fringe projecting from the nippers is now presented to the circular combs with length E + S (Fig. 15). All fibers shorter than E + S are carried away by the circular combs because they are not clamped.

They pass into the noil. In the staple diagram (Fig. 14), this length can be entered as line q-r. In this stage all fibers to the right of the line q-r are combed out into the noil (area qBr). In the region qmnr it is therefore a matter of chance whether the fibers remain in the fringe or pass into the noil. Accordingly, a division can be made based on the mean fiber length represented within this area, and it can be assumed that the trapezium AopC represents fibers transferred to the combed sliver and the triangle oBp represents those passing into the noil. The dividing line between these areas has length E + S/2. Since in similar triangles the areas are in the same ratio as the squares of the sides, and since the noil percentage is based on the ratio of weight of waste to weight of feedstock, the following relationship can be assumed:

$p \% = \frac {oBp}{ABC} \times 100 = \frac {{(op)^2}}{{(AC)^2}} \times 100$$= \frac {{(E + \frac{S}{2})^2}}{{M^2}} \times 100$

Fig. 13 – Position of the nippers relative to the detaching rollers at the closest approach (detachment setting E) during backward feed

Fig. 14 – Combing out with backward feed (the staple diagram is shown)

Fig. 15 – Combing out the fiber fringe