Weft detection device for looms

Abstract

The invention relates to a weft yarn detection device of a weaving machine, which is used to prevent detection delay of weft yarns. During weft insertion of weft yarns of a light absorption system, a light receiving signal (Y2) is output. Because the light receiving signal is used to absorb light by black yarns, a signal level is lower than a light receiving signal (R) of a deformation reed. The light receiving signal is removed by a low frequency removing filtering circuit, and is used to form a high frequency signal (F). In the high frequency signal, an initial light receiving signal (LF) is generated on a negative side. After the high frequency signal is amplified, the high frequency signal is input in a full wave rectification circuit, and a full wave rectification signal (FR) is removed. In the full wave rectification circuit, the negative signal of the high frequency signal, namely the initial light receiving signal, is used as the positive signal, and then is converted into an initial full wave rectification signal (HR). The full wave rectification signal is compared with a threshold (S). the comparator and the full wave rectification signal greater than the threshold are correspondingly used to output weft yarn detection signals, and therefore the initial light receiving signal generated on the negative side is output as the initial weft yarn detection signals without generating delay time.

Description

technical field [0001] The invention relates to a weft yarn detecting device for optically detecting inserted weft yarns in a loom. Background technique [0002] Patent Document 1 discloses a weft detection device for detecting a weft inserted by an optical detection mechanism in a fluid jet loom. The weft yarn detection device has a detection unit main body having a slit through which a weft yarn provided near before weaving operation of the woven fabric can pass. A photosensor composed of a light projecting unit including a light emitting element such as a light emitting diode and a light receiving unit including a light receiving element such as a photodiode and a phototransistor is provided on the detection unit main body through a gap. [0003] The circuit of the weft detection device is configured as follows. The light emitting element of the light projecting part is connected to the drive amplifier, and continuously emits light during the weft yarn detection period....

AI Technical Summary

Problems solved by technology

In weft yarn speed control, jumping back and weft yarn breakage at the front end of the weft yarn are likely to occur because the weft yarn speed exceeds the weft yarn speed at the end of weft insertion. In the weft yarn arrival timing control, it is easy to produce a deviation in the arrival timing of the weft yarn. In air injection control, Unfavorable conditions such as an increase in fluid usage are generated

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