JPH0334021B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for detecting defects in glass fibers in the form of woven fabric (cloth).

Defects occur in glass fibers, such as foreign matter entering the glass field or adhering to its surface, variations in the thickness or thickness of the glass fibers, or contamination of the glass fibers.

[Conventional technology]

The types of glass fiber defects can be classified into the following types based on their causes:

One is due to the mixing or adhesion of foreign matter to the single glass fiber (filament), which is caused by the mixing of conductive foreign matter such as metal into the raw material or the mixing of unmelted pieces of glass. The other problem is variations in the thickness or thickness of the glass fibers, uneven threads, and uneven weaving, which are caused by various conditions of the manufacturing process. Another type of stain is glass fiber contamination, which occurs when water, oil, dust, etc. adhere to the glass fiber during the manufacturing process.

Such defects in glass fibers significantly reduce commercial value. Specifically, for example, the contamination of conductive foreign matter deteriorates the quality of glass fiber used as an electrical insulator. Therefore, it is required to detect defects in glass fibers, investigate the cause of their occurrence, and perform sufficient quality control.

However, glass fibers have minute shapes, and inspection thereof is difficult. Conventionally, the method using the naked eye was mainly used, but in the state of single fibers (filaments) or threads (strands), it was only possible to perform quantitative sampling inspections, and in particular conductive foreign substances such as metals, which were extremely small (1 to 8μ), could be inspected. If minute foreign matter is mixed in, it is impossible to detect it and a complete inspection cannot be performed. In addition, in the state of woven fabric (cloth), it takes a lot of time to inspect using the naked eye method.
The test relies on skill and intuition, and it is difficult to expect a perfect test.

It is therefore an object of the invention to also detect defects in glass fibers, in particular defects that are impossible to detect with the naked eye.
It is an object of the present invention to provide a method for automatic and high-speed detection.

[Means to solve the problem]

In this invention, when a glass fiber is placed in the transmitted microwave, a phase difference is generated between the transmitted waveform and the received waveform, and furthermore, the phase difference is different between a glass fiber with a defect and a glass fiber without a defect. It is based on this knowledge. That is, in the present invention, a glass fiber is passed through a through hole provided in a slit shape in the transmission direction of a waveguide through which microwaves are transmitted, so that the fiber direction of the glass fiber is diagonal to the transmission direction of the microwave. The presence or absence of defects in the glass fibers is detected by detecting the phase difference between the transmitted microwave waveform and the received microwave waveform that occurs in this case.

[Effect]

Since the single fibers constituting the glass fibers G are manufactured by stretching a softened material at high speed, the defects usually extend in the length direction of the single fibers. In addition, when manufacturing long glass fibers,
Usually, it is formed into a mesh shape with warp threads along the longitudinal direction and weft threads perpendicular to the warp threads. Therefore, if the traveling direction of the woven glass fiber G is perpendicular to the microwave transmission direction of the waveguide, the weft threads will be parallel to the microwave transmission direction, and a continuous defect will occur in a single fiber. Even if there is a defect, it will appear as a dot-like defect when viewed from the microwave, which has poor sensitivity and can easily be mistaken for noise. This means that the presence of the glass fiber itself causes a phase shift in the microwave, but the phase shift is different between the high-density central part of the single fiber and the surrounding low-density part, and the microwave Since high-density areas and low-density areas alternately pass perpendicular to the transmission direction, shifts in phase difference due to defects can easily be mistaken for errors. Furthermore, if the warp threads also move at right angles to the waveguide, they will move the shortest distance within the waveguide, making it impossible to increase the passing speed of the glass fibers above a certain level.

On the other hand, if the traveling direction of the glass fiber is made oblique to the microwave transmission direction (preferably at 45 degrees), the fiber direction of the glass fiber will be oblique to the microwave transmission direction. This means that defects that exist continuously in a single fiber do not become dots, but can be detected continuously over a long distance and can be detected reliably. The phase shift is always constant, there is no digital change, and errors are less likely to occur.Furthermore, since the warp threads stay in the waveguide for a long distance, the passing speed of the glass fiber can be increased. This makes it possible to detect defects in glass fibers accurately and quickly.

In this way, defects in warp yarns and defects in weft yarns can be detected equally in terms of both detection sensitivity and detectable time, improving overall detection sensitivity and simplifying the determination level setting for the presence or absence of defects. ,
This makes defect detection easy and reliable.

〔Example〕

In Figures 1 and 2, 1 is a transmitter that generates microwaves, 2 and 3 are coaxial cables that transmit microwaves, and 4 and 5 are converters that convert microwaves from coaxial cables to waveguides, which will be described later. 6 and 7 are unidirectional tubes that pass only the required microwaves traveling in one direction and attenuate reflected waves; 8 is a waveguide forming a microwave transmission line; 9 is a pipe of waveguide 8; A slit-like through hole is formed in the wall in the transmission direction and allows the glass fiber G in the form of a woven fabric to pass through, 10 is a receiver for receiving microwaves, and 11 is a receiver for detecting the phase difference between the transmitted waveform and the received waveform of the microwave. This is a displacement meter for measurement.
As shown in the figure, the traveling direction of the glass fiber G is inclined with respect to the longitudinal direction of the waveguide, that is, the direction of microwave transmission.

In the above configuration, the glass fiber G in the form of a woven fabric to be examined is passed through the through hole 9 of the waveguide 8 through which microwaves are transmitted, at a constant speed of, for example, 60 m/min.

In this case, the microwave transmission waveform and reception waveform are as shown in FIG. That is, when there is no defect in the glass fiber, the received waveform b shows a phase difference α with respect to the transmitted waveform a, and when there is a defect, for example, the received waveform c shows a phase difference α with respect to the received waveform b when there is no defect. It shows the phase difference β. These phase differences are measured by the displacement meter 11, and a defect can be detected by detecting that the phase difference has increased or decreased by a predetermined amount compared to the phase difference α when there is no defect. Note that a suitable value for the frequency of the microwave is, for example, 9 to 11 GHz.

The reason why the traveling direction of the glass fiber G is inclined with respect to the transmission direction of the waveguide is that the fiber direction of the glass fiber is oblique to the transmission direction of the microwave, as explained in detail in the operation section. This is to make it easier to detect warp defects and weft defects while balancing the detection sensitivities of both defects.

[Effects of the Invention] As explained above, the present invention allows glass fibers to pass obliquely through a microwave transmission path, and defects therein are detected by the phase difference between the transmitted waveform and the received waveform. Therefore, defect detection can be ensured and automated, and in particular, extremely small defects, which are impossible to observe with the naked eye, can be easily and reliably inspected.

[Brief explanation of the drawing]

Fig. 1 is a schematic configuration diagram of an apparatus for carrying out the present invention, Fig. 2 is a sectional view taken along the line shown in Fig. 1, and Fig. 3
The figure is a diagram showing a microwave transmission waveform and a reception waveform. G...Glass fiber in the form of woven fabric, a...Microwave transmission waveform, b...Microwave reception waveform (no defects), c...Microwave reception waveform (with defects), 8...Waveguide Pipe, 9...through hole.

Claims (1)

[Claims] 1 A slit-like through hole through which a woven glass fiber passes is provided on the opposite wall surface of a waveguide through which microwaves are transmitted, along the transmission direction of the microwave, and a slit-like through hole through which a woven glass fiber passes through the through hole is provided. The glass fibers are arranged such that the fiber direction of the glass fibers is oblique to the transmission direction of the microwaves in the plane of the glass fibers, and the transmission waveform of the microwaves and the reception of the microwaves after passing through the glass fibers are A method for detecting defects in glass fibers, comprising detecting defects in glass fibers by detecting a difference in phase difference of waveforms.