A control method and system for weft-braking devices for automatically adjusting the mechanical tension of the yarn in weaving maschines

摘要

An improved method for controlling electrically operated weft-braking devices, capable of automatically adjusting the mechanical tension of the weft yarn (F) in mechanical-picking weaving machines (TE), is disclosed herein. The excitation current (Ie) of the weft-braking device (LF) is controlled by an adjustment loop (A) using a signal (tens-mis), which is a measure of the actual tension of the yarn, as a feedback signal for the adjustment loop (A). The improvement comprises employing an average value (TMx), which is computed at predetermined intervals (x) of weft picking and for a predetermined number (i) of picking strokes, in order to measure the direct tension of the thread (F), so that said average value (TMx) is substantially stable and not affected by fluctuations due to variations of the parameters of the weaving process.