Rieter

Conceptual structure of the drafting system

Index

3-roller, double-apron drafting systems are used exclusively on modern ring spinning machines used for short staple spinning. They consist of three fluted, driven, bottom steel rollers (a) with top rollers (b) positioned above them, supported and pressed against bottom rollers (a) by a rocking support (c) (pressure arm). Since a fiber bundle with only few fibers has to be transported in the main drafting zone, the main drafting zone is provided with a guide unit consisting of rotating bottom and top aprons (e).

The top rollers are usually arranged as shown in Fig. 8. An overlap (a) of 2 - 4 mm is usually selected for the front rollers and an underlap (b) of 2 - 4 mm for the middle rollers. The overlap and underlap ensure smooth running of the top rollers, and the overlap of the front roller also shortens  the spinning triangle by advancing the nip line (refer to „ Spinning geometry“), which has a correspondingly positive impact on ends down frequency. Another roller configuration has been offered by the INA company in the so-called VDraft drafting system. In this case the rear top roller is shifted to the rear on the bottom roller. The larger wrapping arc (a, Fig. 9) results in an additional fiber control zone. However, it can also result in a wider spread of the fiber ribbon.

Fig. 7 – The drafting system

Fig. 8 – Section through the drafting system

Fig. 9 – The INA drafting system