JPS584285B2 - Yarn inspection method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for detecting abnormal portions of thickness contained in yarn, and in particular detects abnormal portions such as undrawn portions and yarn knots present in synthetic multifilament. It concerns the method of inspection.

Conventionally, this type of inspection method is the Seriprene method, in which a thread is rolled up on a black board and judged visually, but in the first place, there are not many abnormal areas, and a large number of samples are required to conduct a proper inspection. In addition, the size of the abnormal part is approximately several tens of microns at most, and it is difficult to use this method to inspect not only the number but also the size of the abnormal part.

In addition, some methods have been adopted in which the yarn is passed between slits with an appropriate gap set and detected while being suctioned and run using an air sucker, etc., but this method involves the trouble of manually determining whether the yarn is caught in a slit. In addition to this, there is a limit to the accuracy of setting the gap, and it is impossible to determine even the size of the abnormal part.

Japanese Patent Publication No. 43-18869 proposes a method in which a pair of rollers grips and runs the yarn, and detects abnormalities based on the displacement of one of the rollers.

This is particularly useful for monofilament yarns, but is difficult to apply to multifilament yarns due to the periodic displacement of the rollers due to twisting.

Furthermore, when using this method, the responsiveness of the detection unit is up to 200c.
ps, making it difficult to accurately detect at high speeds.

The present invention is a method for automatically and continuously measuring the yarn cross-sectional state of a single filament yarn constituting a multifilament, based on improvements over these conventional techniques.

That is, the present invention allows the yarn to be measured to run between a fixed piece and a movable piece that are in contact with each other with a predetermined contact pressure while separating them, and converts the displacement of the movable piece into an electrical signal. In a yarn inspection method for measuring the thickness of a yarn, an electrical signal of a steady fluctuation portion having a constant amplitude and wavelength based on the twist of the yarn to be measured is set in advance, and the electric signal is obtained by the displacement of the movable piece. This yarn inspection method is characterized in that the electric signal generated by the abnormality is passed through a predetermined frequency filtering circuit, the electric signal of the stationary fluctuation portion is removed, and the electric signal due to the abnormal portion is extracted and the abnormal portion is discriminated.

Next, the configuration of an embodiment of the present invention will be explained in detail based on the drawings.

FIG. 1 is a block diagram of the entire apparatus, in which a multifilament yarn 1 is wound from a bobbin 2 to a pulley 6 via a yarn guide 3, a tension adjustment device 4, and a detection section 5.

Reference numeral 7 represents a circuit portion that appropriately amplifies and displays the signal from the detection unit 5, and 8 represents a motor that drives the pulley 6.

FIG. 2 is a detailed view of the detection unit 5, in which a cantilevered leaf spring 10 has strain gauges 9, 9 attached to both the front and back sides so as to measure vertical displacement. A movable piece 11 is fixed downward.

On the other hand, directly below the movable piece 11 and parallel to it, there is a fixed piece 12.
are provided facing upward so that their tips come into elastic contact with each other in a straight line.

The fixing piece 12 is fixed to the upper surface of a columnar pedestal 15 attached to the tip of a vertical rod 14 that can finely adjust the shaft height up and down.

The pedestal 15 can be vertically moved up and down along the guide 13.

Then, by adjusting the rod 14, the movable piece 11 and the fixed piece 12 are
An appropriate reaction force F is applied to the line contact part (hereinafter referred to as nip point F1).
The structure is designed to bring about this.

In the figure, reference numerals 16 and 17 are thread guides at the entrance and exit portions, respectively, which are attached so that the thread 1 passes through the nip point P1 between the movable piece 11 and the fixed piece 12. By taking the thread 1, the thread 1 is run to the nip point P1, and the displacement of the movable piece 11 due to the state of the thread becomes a strain on the leaf spring 10, which is detected by the strain gauge 9.

An example of a device implementing the invention is as described above.

In the initial state when the multifilament yarn 1 is set and winding is started, the twist is squeezed at the nip point P1 and does not pass through the nip point P1. Twisting remains between points P2.

When this retained twist exceeds a certain amount, the twist begins to pass through P1 and reaches a steady state as appropriate.

That is, the multifilament yarn 1 having a twist passes through the bobbin 2 at a yarn speed v, but is nipped between the movable piece 11 and the fixed piece 12 with a contact pressure F at the nip point P1. Therefore, the twist cannot pass through and the contact resistance point P2 of the tension adjustment section 4
However, when a certain number of twists is reached, the untwisting torque generated in the relationship between the preset yarn tension T and the number of retained twists overcomes the contact pressure F, and the twist reaches the nip point. P1
It passes through.

After this equilibrium state is reached, the twists from the bobbin 2 pass through the P2 point together with the yarn 1 and enter the retention zone, and the twists leave the zone and pass through the P1 point.

Here, since the yarn speed v is constant and the number of yarn twists in the bobbin is approximately constant, in this equilibrium state, at point P1, twists of approximately constant period will be lost over time. .

However, when the twist does not pass through, the movable piece 11 and the fixed piece 12
In this state, as shown in FIG. 3, the movable piece 1 is
1 presses the fixed piece 12 and the tension T is applied, so that the multifilament threads 1 are arranged in a strip on a plane.

Also, when the twist passes through the nip point F1, the 4th and 5th
, 6, about half of the single filaments constituting the multifilament pass diagonally across the other band-shaped single filament groups.

According to research conducted by the present inventors, it has been found that when a group of single filaments overlap and pass, the displacement of the movable piece 11 over a wide range of contact pressure F is less than twice the displacement when no twist passes. did.

In addition, the strength of this contact pressure F affects the number of retained twists between P1 and P2, and therefore the overlapping angles θ and γ of the threads when the twists pass through the P1 point (see Figures 5 and 6). When becomes large, θ and γ become large, and when becomes small, θ and γ become small.

Therefore, by setting this appropriately, the displacement signal from the strain gauge 9 becomes a substantially sine wave as shown in FIG.

Figures 8 and 9 are schematic diagrams of typical abnormal parts that exist in a single filament constituting a multifilament. When such an abnormal part passes through point P1, it will appear as shown in Figure 7, as shown in Figure 10. The abnormal part signal appears superimposed on the sine wave.

By passing this signal through a sine wave filter circuit, a signal as shown in Fig. 11 is obtained, which is then appropriately processed by a known arithmetic circuit to display abnormal portions of the yarn by distinguishing them by cross-sectional size, length, etc. I can do it.

FIG. 12 shows an example of the arithmetic circuit 7, in which the signal from the strain gauge 9 is amplified in one stage, passed through a sine wave filter circuit, removes the twisted signal consisting of a sine wave, and after widening the signal, RV1...
The bias voltage is appropriately set by RVu, the signal for each setting is obtained by a comparator, the waveform is shaped by a Funshot multivibrator, and each is added and displayed as a TTL level signal by a counter.

In addition, the changeover switches SW and SW are switched to the bypass circuit of OP21 whose gain is equivalent to that of the operational amplifiers OP11 to OP14, and the micrometer 14 moves the fixed piece 12 of a known quantity upward to give a displacement to the movable piece 11.
Set RV1 so that the input of OP1 becomes zero, then sequentially operate the rod 14 and set RV2 and OP1 respectively.
...By setting RVn, the dimensions of the abnormal filament part and the number displayed on the counter are matched in advance.
Perform calibration in conjunction with each detection level setting.

In this way, the twist signal of the multifilament yarn is treated as a standing wave, and only the signal of the abnormal part of the single filament yarn is distinguished and then subjected to appropriate analog calculation processing, so that the distribution with respect to the cross-sectional size of the abnormal part It can be determined quantitatively.

Furthermore, by digitally processing the output pulse widths of OP1 to OPn in FIG. 12, it is also possible to obtain the distribution with respect to the length of the abnormal portion.

Furthermore, it is also possible to instantaneously stop the motor 8 using each counter input signal and sample the abnormal portion.

On the other hand, the rate of change of the abnormal part of the filament yarn from the normal part is represented by the change angle as shown in Figures 8 and 9.
, α', which is extremely large compared to the change angle γ when the normal portion overlaps due to twisting as shown in FIG. 6, and the rising angle of the signal from the detection section is sharp.

Therefore, the object of the present invention can be sufficiently achieved by appropriately differentially processing this signal.

In this way, since it is possible to distinguish the steady twisting signal of multifilament yarn, it is possible to detect abnormal areas such as undrawn parts and knots in single filament yarn at continuous high yarn speed and with high precision. It has become possible to detect highly quantitatively, and has become a means of elucidating problems whose causes were previously unknown.

Example v = 400m/min T = 30g F = 1.0P fc = 0.4KHz Under the conditions of RV1 to RV8 in 8 steps (n = 8) in 5μ increments, polyester semidal filament 30 denier 12 filament, For a sample with a twist number of 37T/m (
A) Those with good operability and almost no fluff (B) Those with unfavorable operability and a lot of fluff. The present invention was applied to each of these, and the graph shown in FIG. 13 was obtained.

This clearly shows that the number of yarn defects has a high correlation with workability, and by using the method of the present invention, it is possible to predict workability in subsequent processes.

[Brief explanation of the drawing]

The drawings show one embodiment of the method of the present invention, in which Fig. 1 is an overall configuration diagram, Fig. 2 is a detailed explanatory diagram of the detection section, and Fig. 3 is an illustration of a multifilament yarn passing through the detection section. Fig. 4 shows the state of the movable fixed piece when the untwisted portion passes through it, and Fig. 4 shows the state where the twisting part passes. Figures 5 and 6 show the twisted state of the multifilament when passing through the detection section, Figure 7 shows the signal in a steady state where only the twist passes through, and Figure 8
, 9 shows an abnormal part existing in a single filament, Fig. 10 shows a signal when the multifilament in which the abnormal part exists passes the detection part, and Fig. 11 shows the signal shown in Fig. 10. This is the signal after passing the signal through the HPF. Further, FIG. 12 shows an embodiment of the circuit portion for amplification, calculation, and display. FIG. 13 shows a graph of a measurement example.

Claims (1)

[Claims] 1. The yarn to be measured runs between a fixed piece and a movable piece that are in contact with each other with a predetermined contact pressure while separating them, converts the displacement of the movable piece into an electric signal, and thereby changes the thickness of the yarn. In the yarn inspection method for measuring the twist of the yarn to be measured, an electric signal of a steady fluctuation portion having a constant amplitude and wavelength based on the twist of the yarn to be measured is set in advance, and the electric signal obtained by the displacement of the movable piece is A method for inspecting a yarn, which comprises passing the yarn through a predetermined frequency filtering circuit to remove the electric signal of the stationary fluctuation portion, extracting the electric signal due to the abnormal portion, and identifying the portion.