JPH042867A - Method for detecting defect in material of continuous length - Google Patents

Abstract

PURPOSE:To enable accurate and quantitative sensing of pulled yarn by reflecting the propagation of elastic waves due to vibration applied to a cloth running under a tension through a fixed plate and monitoring the amplitude modulation of the formed standing waves. CONSTITUTION:A vibrator 1, using a solenoid coil and provided near one of two feed rollers 2 having different feed speeds is operated for a cloth 7 running through the two feed rollers 2 under a prescribed tension to apply vibration at a low frequency thereto. The aforementioned vibration as elastic waves is propagated to the other feed roller 2 and reflected with a fixed plate 3 arranged in the course thereof to form standing waves between the aforementioned vibrator 1 and the fixed plate 3. The state of the standing waves is monitored with a TV camera 4 and the resultant signal is then processed with a signal processor 5 and subsequently displayed on a display device 6. Thereby, the modulation of standing wave amplitude caused by variation in cloth tension due to pulled yarn is sensed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for detecting defects in elongated articles such as woven or knitted fabrics or film-like articles. More specifically, the present invention relates to a method for detecting "hanging threads" which are a type of defect inherent in textiles.

(Prior Art) A "hanging thread" is a type of defect inherent in textiles. In other words, in a textile structure formed by warp and weft threads crossing each other, threads with abnormally high tension may be mixed into some of the warp threads or weft threads, and these are called "hanging threads".
This is called a defect and is treated as a defect.

Traditionally, inspection of defects inherent in textiles has relied solely on the visual or tactile sense of an expert. In recent years, in order to automatically detect defects in these textiles using machines,
Several proposals have been made. However, detection of the "hanging thread" still relies heavily on the visual sense and tactile sense of an expert, and no method or device for automatically detecting this has been proposed. Even in its normal state, textiles have extremely complex structures.

Even for experts, the current situation is that they supplement the information obtained from vision with the information obtained from the tactile sensation of directly touching the fabric with their fingers, especially when it comes to detecting "hanging threads."

(Problems to be Solved by the Invention) These inspections using human vision and tactile sense require skill on the part of the person performing the inspection, and are not always sufficient in terms of efficiency and accuracy. These problems are fatal when inspecting fabrics produced in large quantities using multiple looms. That is, as mentioned above, even in its normal portion, a woven fabric has an extremely complicated structure, and there is no small variation in the tension of the warp and weft yarns. Detection of hanging threads is the process of extracting particularly large deviations from this variation, and a certain standard should originally be set for this. However, even with the eyes and hands of an expert, it is virtually impossible to constantly inspect many fabrics with a constant standard.

In recent years, it has become possible to stabilize the quality of industrial products at a high level through thorough QCl, or quality control. It is amazing how much quality control has been carried out.

In view of this situation, the present inventors have conducted extensive research, and as a result,
We have achieved the next invention relating to a method for detecting hanging threads with good reproducibility and with a certain standard.

(Means for Solving the Problems) That is, the present invention provides a method for detecting defects inherent in a long object, in which a tension abnormality in the long object caused by the defect is caused in the long object. This is a method for detecting defects in long objects, characterized by detecting them as modulation of standing waves of elastic waves.

The present invention detects defects by detecting tension fluctuations in a long object caused by hanging thread guiding defects inherent in the fabric. Further, as means for detecting this tension fluctuation, it is detected as a modulation of a standing wave of an elastic wave generated in the textile.

Such a detection method involves, for example, conveying the fabric continuously or intermittently using a roller system or the like, applying tension to a specific area of the fabric, and applying a predetermined vibration to the area where the tension is applied. This is achieved by generating a standing wave in a specific area of the fabric and monitoring the state of the standing wave.

Although the mechanism for applying vibration to the fabric is not particularly limited, methods such as a piezoelectric vibrator, a solenoid coil, and rotation of an eccentric roller can be used. The frequency of vibration is easy to determine because it is influenced by factors such as the acoustical physical factors of the fabric itself, the tension that can be applied to the fabric, the ability to monitor the vibration propagation state, etc. Although it is difficult, the ultrasonic range of 20kHz abnormality or the low frequency range from 0.0IHz to 35Hz is preferable, and more preferably from 0.1Hz to 10Hz.
This is an extremely low frequency range of Hz.

The standing wave monitor is not particularly limited, but one that can be monitored in a non-contact manner is preferred. For example, optical sensors, electrostatic sensors, ultrasonic sensors, etc. can be used.

(Function) It is very difficult to directly and non-destructively measure tension fluctuations in a long object due to defects in the hanging string or the like inherent in the long object.

In the present invention, "miso" is used to detect tension fluctuations of a long object from the vibration state of standing waves generated in the long object.

In other words, the vibration state of a standing wave is affected by various acoustic engineering physical factors of the medium, and in particular, the tension of the medium has a large effect on the amplitude of the standing wave, the positions of nodes and antinodes, and the damping characteristics. be. Therefore, by monitoring the standing waves generated in the fabric, it is easy to discover if there is a tension abnormality, that is, "stiffness" in the fabric.

EXAMPLES The present invention will be explained in more detail by way of Examples below, but the present invention is not limited thereto.

(Examples) Example 1 FIG. 1 is a schematic explanatory diagram showing a detection part of a detection device used in the defect detection method of the present invention. As shown in the figure, two feed rollers are installed as part of the roller system that continuously or intermittently conveys the fabric to be inspected.
A predetermined tension is applied to the fabric by making a difference in the feeding speed of the two rollers. A vibrator using a solenoid coil is provided near one of the feed rollers, and applies a low frequency vibration of 3.5 Hz to the fabric. The vibration given to the fabric is an elastic wave,
The wave propagates toward the other roller, but is reflected at a fixed end provided in the middle, and a standing wave is formed between the vibrator and the fixed end.

The status of the standing wave is monitored by a TV camera,
The obtained signal is displayed after predetermined signal processing.

The roller width is 100cm, and the feeding speed of the fabric is 0 to 80m by controlling the drive motor of the conveyance system with an inverter.
It was made variable between / minutes.

Figure 2 is an example of a signal obtained from a normal part without a hanging string, and a standing wave with nodes and antinodes located at equal intervals can be observed.

FIG. 3 is an example of a signal obtained from a certain part of the fishing line. It is shown that the positions of the nodes and antinodes of the standing waves are shifted due to tension fluctuations in the fabric caused by the hanging thread, and that the amplitude also appears to be modulated.

(Effects of the Invention) According to the present invention, compared to human visual and tactile inspections,
It does not require any skill, is superior in terms of efficiency and accuracy, and has become possible to quantitatively determine criteria.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram of the inspection device used in the present invention, Fig. 2 is an example of a signal detected by the inspection device used in the example for a fabric without a hanging thread, and Fig. 3 is an example of a signal for a fabric with a hanging thread. An example of a signal is shown. DESCRIPTION OF SYMBOLS 1... Vibrator, 2... Feed roller, 3... Fixed plate, 4... TV camera, 5... Signal processing circuit, 6...
...Indicator, 7...Textile

Claims (1)

[Claims] (1) In a method for detecting defects inherent in a long object,
A method for detecting a defect in a long object, characterized in that an abnormal tension in the long object caused by the defect is detected as a modulation of a standing wave of an elastic wave generated in the long object.