Sensor activated weft tension device

Details Sensor activated weft tension device Sensor activated weft tension device

1994-07-05

1995-10-31

Falik, Andy

Textiles: weaving

Weft manipulation

Tensions

139452, D03D 4734

Patent

active

054620945

DESCRIPTION:

BRIEF SUMMARY
FIELD OF THE INVENTION

The present invention refers to a method of the type wherein the insertion process for a weft yarn into a loom includes exposing the weft yarn to a braking friction and detecting the yarn tension of the weft yarn, and further relates to a loom of the type which includes a weft yarn feeder, a weft yarn insertion brake and a tension sensor for detecting the weft yarn tension.


DESCRIPTION OF THE INVENTION

In the case of a loom known from EP-A2-0 357 975, a tension sensor and an insertion brake are provided downstream of the weft yarn feeder, the insertion brake being controlled in response to the weft yarn tension behavior detected by the tension sensor. However, the tension sensor applies, just as the insertion brake, friction to the weft yarn during the insertion process, and, taking into account the high insertion speeds and short insertion times which are nowadays used, this friction applied is disadvantageous, because a frictional load on the weft yarn also during critical acceleration and high-speed phases exerts an undesirable influence on the development of the insertion process and may damage and possibly break the weft yarn. During the control of the insertion process, the permanently active tension sensor will apply a frictional load to the weft yarn in an undesirable manner even at times at which said weft yarn should be transported as unhindered as possible.
EP-A1-03 56 380 and EP-A1-01 55 431 disclose controlled weft yarn insertion brakes for jet looms, which, in correspondence with the sequence of motions of the weft yarn during the insertion process, become effective in a controlled manner only at intervals for damping the increase in tension which will inevitably occur towards the end of the insertion process due to a whipping effect. In connection with these air-jet looms, it is known to decelerate the weft yarn at the end of the insertion process when a high tension peak occurs due to a whipping effect in the weft yarn resulting from the fact that the weft yarn is stopped; this tension peak may break, locally elongate or retract the weft yarn and it may cause said weft yarn to assume a wavy shape. The braking operation should start a short time before the tension peak occurs, but its intensity and duration should only be of such a nature that the tension peak is reduced, that the weft yarn is in the maximum possible stretched condition before the period of time predetermined for the insertion process expires, and that the free end of the weft yarn reaches the end of the shed before the reed beats up. Hence, the control of the braking operation should precisely be adapted to the actual sequence of movements of the weft yarn during the insertion process. Information on the weft yarn movement which can be used for controlling the braking operation are, for example, passage signals which are produced in the weft yarn feeder when the yarn is drawn off. The moment at which the tension peak occurs is an additional, useful and precise information for the termination of the insertion process and for controlling the braking operation for subsequent insertion processes; on the basis of said information, a possibly existing difference between the movement of the weft yarn coming from the weft yarn feeder and the deviating movement of the weft yarn end in the shed--which deviation may, for example, be caused by a take-off balloon--can be taken into account for controlling the braking operation at the right moments. Furthermore, due to the increase in tension occurring when the reed beats up, the measure of detecting the tension additionally supplies information which will show whether the insertion process has properly been terminated before the beat up takes place, and, prior to this, said measure of detecting the tension also supplies information which will indicate the fact that the insertion process has been started properly as well as the moment at which the weft yarn is released by the yarn feeder for drawing off, said last-mentioned information being supplied on the bas

REFERENCES:
patent: 4157722 (1979-06-01), Tojo et al.
patent: 4359068 (1982-11-01), Loepfe et al.
patent: 4875506 (1989-10-01), Gacsay et al.
patent: 4932442 (1990-06-01), Ishido et al.
patent: 5002098 (1991-03-01), Desmet et al.
patent: 5050648 (1991-09-01), Pezzoli
patent: 5144988 (1992-09-01), Del Favero

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