Rieter

Spinning angle γ

Index

At the thread guide of the lappet, the yarn is deflected more or less according to the design of the machine, mainly depending on angle γ (Fig. 82). This angle also has a major influence on the ends down rate and yarn formation due to the twist insertion operation. Twist is inserted at the traveler by its rotation. The twist must rise against the movement of the yarn up to the front rollers, where it has to tie in the fibers. If deflection arc γ at the lappet is large (Fig. 82), a substantial part of the rising twist will be held back at this point. The fiber mass at the critical point, i.e. the tying-in point of the spinning triangle, therefore has less twist than ultimately the final yarn. This results firstly in more ends down, because yarn strength between the drafting system and the lappet is simply inadequate owing to insufficient twist, and secondly the twist retention impairs the tying-in of the fibers. The yarn receives its twist in two stages, most of it at the spinning triangle and then an additional twist insertion in a yarn already formed between traveler and lappet. This in turn is detrimental to the yarn properties.
Also important at this point is almost constant contact with the thread guide eyelet, i.e. the yarn should always lie on the lappet wire. Alternate touching and lifting clear of the wire during one revolution of the traveler causes tension peaks at the spinning triangle which again increase the ends down rate.

Fig. 82 – Spinning geometry angles and dimensions