Reflected light type weft monitoring device

Details Reflected light type weft monitoring device Reflected light type weft monitoring device

2000-05-05

2001-06-12

Falik, Andy (Department: 3741)

Textiles: weaving

Stopping

Weft

C250S559010, C356S430000

Reexamination Certificate

active

06244305

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a device for monitoring of a thread, for example the weft thread in a loom of substantially the type in which the weft is driven through the shed of the loom with the aid of a jet, such as a gas jet, for example an air jet, and which has a reed with a longitudinal channel for the weft and an arm with a free end in a position at which it is desirable to monitor the arm weft, the free end having at least one light source for illuminating the monitoring point and possibly the weft located there, and a number of light-sensitive elements.
BACKGROUND OF THE INVENTION
Prior art arrival-indicators function unreliably, often resulting in many erroneous triggerings, as well as many actual fault triggering situations which remain undetected. These problems are particularly accentuated in air-driven looms, so-called jet looms, which are extraordinarily rapid and which operate at such high speeds as 20 picks per second, in which event the arrival sensing must be executed under approximately 10-15° of a whole machine cycle (5% of the cycle). This naturally places extremely high demands on the indicator proper and its associated electronics, in particular as regards sensitivity and speed. Moreover, prior art indicators with whose help a part of the above-outlined problems have been reduced or even wholly obviated have proved to be extremely uneven in connection with different weft yarns, which may reflect light to different extents. The problems have been accentuated in the employment of weft yarns with different colors and structures. In certain contexts, the problems have proved to be so intractable that no signals have been emitted at all on the use of certain weft threads or weft yarns.
SUMMARY OF THE INVENTION
The object of the present invention is to improve the indicators and, to such a high degree as is possible, to obviate or at least reduce the sensitivity to different weft yarns or weft threads, both as regards color and structure.
This object is solved according to the present invention in that the device of the invention is characterized in that the light-sensitive elements are each aimed in a direction towards the channel for sensing the light reflected from an illuminated area to generate an electric signal corresponding to the reflected light, and are each connected to an evaluator circuit for adding the signals regardless of whether the weft occurring in the monitoring point entails an increase or reduction of the signals obtained from the light-sensitive elements. The illumination of the monitoring point is pulsed to generate a carrier wave with an average amplitude which represents the reflection of light from the channel in the reed and which changes on the occurrence of the weft. The light source and the light-sensitive elements are focused substantially on a line which extends transversely of the channel in the reed. The evaluation circuit includes one channel for each light-sensitive element and electronic circuit elements which are programmed to treat the signals from the channels, and thereby the light-sensitive, as absolute value.
The present invention provides a monitoring device which may be employed with great reliability in the most rapid jet looms or air-driven looms in that the weft thread is sensed with great dependability regardless of structure or colour. A device according to the present invention is moreover relatively independent of where in the channel the monitored thread is located. A monitoring device according to the present invention moreover obviates the majority of drawbacks inherent in prior art designs and constructions.


REFERENCES:
patent: 4738284 (1988-04-01), Ishikawa
patent: 5479965 (1996-01-01), Rydborn
patent: 5694979 (1997-12-01), Toda

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