Rieter

Sliver coiling

Index

As already described for the  card, two rotary movements are required for cycloidal coiling of the sliver. On the one hand, the rotatable plate must be rotated above the can, while the can itself must rotate, at a considerably slower rate, below the plate. A sliver tube is provided on the plate as a fixed part to guide the sliver from the calender rollers into the can (Fig. 11). This tube extends from the center of the plate to its periphery. It is important for the coils that the circumferential velocity at the deposition point (sliver exit point) is somewhat higher than the delivery speed, so that blockages of the sliver in the tube are avoided.

However, the difference should not be too large, otherwise noticeable false drafts arise in the sliver. Due to the very high delivery speeds of modern drawframes, coiling is becoming increasingly critical. That is why the shape of the sliver tube is no longer straight, but is now curved exactly to correspond to the movement of the coiling sliver. On the Rieter drawframe a honeycomb-structured, high-grade steel sheet is also provided on the underside of the rotating plate to prevent depositions of spin finish when processing synthetic fibers.

Change gears are provided to permit adjustment to requirements. The plate is usually driven by toothed belts and the can turntable by gear wheels or an individual drive. The sliver may be laid in the cans in small coils (under-center coiling) or in large coils (over-center coiling) depending on the size of the cans (see  Technology of Short-staple Spinning).
The direction of rotation may also be changed and change gears are also provided for this purpose. The plate and the can turntable were formerly made to rotate in the same direction or in opposite directions. The direction of rotation exerts an influence on the quality of the coiling operation.

The standard can format in short staple spinning was always cylindrical (Fig. 12). Some years ago Rieter introduced a new format: the rectangular CUBIcan can (see Fig. 13). Compared with the cylindrical can it has three major advantages:

  • capacity is increased by about 75%, due not only to the geometry of the can but also to the elimination of the can spring;
  • it permits optimal utilization of the space available in down-stream processing (especially in rotor spinning);
  • it is suitable for automation.

These advantages make the rectangular can very interesting. Drawframes for filling slivers into rectangular cans are offered by Rieter and Trützschler.

Fig. 11 – Rieter Coiler (CLEANcoil)

Fig. 12 – The Rieter RSB-D 40 drawframe

Fig. 13 – Drawframe with rectangular cans