The present generation of electronic weft stop motions monitors weft insertion on projectile weaving machines up to the range of 310 machine degrees, i.e. shortly after arrival of the projectile in the receiving mechanism.
An extension of monitoring to the end of the pull back phase at 0 machine degrees is achieved with the KBW-L short weft detector specially developed for top quality requirements in the weaving mill. This also detects safely the shortest mispicks in the right fabric selvedge area.
The heart of the KBW-L is the one-part optical sensor to be fitted at the right end of the reed. If the weft insertion is correct, an infrared light beam crosses the weft thread at about 0 degrees and is briefly interrupted at the same time. If there is no weft thread and therefore no light interruption, the machine is stopped at approx. 85 degrees, i.e. after the reed beat-up but still before insert of the next weft thread. Short mispicks can be easily seen in this machine position and corrected by the operator.