JPH0593734A - Apparatus for detecting presence of running of line-shaped body - Google Patents

Abstract

PURPOSE:To obtain an apparatus which can detect whether a line-shaped body such as thread, string, rope, wire or cable runs or not without contacting a body to be detected. CONSTITUTION:A light source 1 and a slit 2 are arranged to form a slit light, which is made to irradiate an object 4 to be inspected diametrically and the resulting slice projection image is received with a photodetector 5. When the body 4 to be inspected runs, the diameter of the projection image changes cyclically and hence, an AC component in a specified frequency range is extracted with an AC amplifier 6 and a filter 7 from an output of the photodetector 5. When the amplitude of the AC component lowers below a specified value, the drop thereof is detected with an output circuit.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for detecting the presence or absence of running of a linear body such as a thread, a cord, a rope, a wire, an electric cable or the like.

[0002]

2. Description of the Related Art Conventionally, a pulley that comes into contact with a subject such as a thread is provided, and tension is applied to the roller by a spring, and the return of the roller when the subject is gone is detected by a limit switch or the like. Alternatively, an encoder is provided on the pulley to obtain an electric pulse signal.

[0003]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a device for detecting the presence or absence of a running subject without contact by eliminating a member such as a pulley that comes into contact with a running subject.

[0004]

Means for Solving the Problems An apparatus for detecting the presence or absence of traveling of a linear object of the present invention for solving the above problems is a slit for irradiating a subject with light only in a direction intersecting a traveling direction of the subject. Light source, a light receiving element that receives a slice projection image of the subject by the slit light source, a selection circuit that extracts an AC component in a predetermined frequency range from the electric output signal of the light receiving element, and the AC component is a predetermined value or more. Is also characterized in that it has an output circuit which outputs a detection signal when it drops.

[0005]

[Function] An object such as a thread, a string, a rope, or a wire has a wavy change in diameter due to twisting. Therefore, the amount of light received by the light receiving element that receives the slice projection image of the subject periodically changes depending on the diameter change pitch of the subject and its traveling speed.
That is, the received light output signal includes an AC component. The selection circuit separates this AC component. If there is no object, the amount of received light will stick to the maximum value and only the DC component will be present, and the AC component will be zero. Further, when the subject stops, there is no temporal change in the amount of received light, and only the DC component determined by the projected image in the stopped state becomes, and similarly the AC component becomes zero.

[0006]

Embodiment FIG. 1 shows an embodiment of the present invention. For example, a slit 2 having a width of 0.25 mm is provided on the front surface of a light source 1 which has a convex lens and emits substantially parallel light rays, and has a length of 0.25 m.
The slit light 3 having a width of m illuminates the traveling subject 4. A slit width varying device is provided so that the slit width can be adjusted according to the condition of the subject. The slit 2 is arranged in a direction orthogonal to the traveling direction of the subject 4.
The light receiving element 5 is provided near the rear of the intersection of the slit light 3 and the subject 4.
Is provided. The light receiving element 5 has an elongated shape, and the long side of the light receiving surface is sufficiently longer than the maximum diameter of the projected image of the subject 4, and the long side and the traveling direction of the image are arranged in a direction orthogonal to each other. ..

The output voltage signal of the light receiving element 5 is input to the AC amplifier 6, the DC component is cut and only the AC component is amplified, and then input to the filter (filter) 7 having the following predetermined frequency characteristic. As this filter, a low pass filter, a band pass filter, or a high pass filter can be used. This AC amplifier 6 and filter 7
Constitutes the sorting circuit. The output of the filter 7 is input to the one-shot timer 8.

A circuit example of the one-shot timer 8 is shown in FIG.
Shown in. Input voltage E ₁ applied to the base of the transistor T
When is small, the collector-emitter of the transistor T is off, so that the capacitor C is charged toward the DC power supply V with the time constant C (R ₁ + R ₂ ) through the resistors R ₁ and R ₂ , and the output voltage E ₂ Rises over time. Input voltage E
_{When 1} increases above a predetermined value and the transistor T turns on, the electric charge of the capacitor C is discharged with a time constant CR ₁ .
If the resistance value R ₂ is set sufficiently larger than R ₁ ,
Discharge progresses rapidly and the output waveform becomes a triangular waveform.

The comparator 9 compares the output voltage E ₂ of the one-shot timer 8 with the comparison voltage E ₃ and outputs the output voltage E _{2.
When 2} is smaller, L level is output, and when the output voltage is larger, H level and binary signal are output. The one-shot timer 8 and the comparator 9 form an output circuit. The power supply circuit supplies DC power supplies for the light source 1, the amplifier 6, the selection circuit, and the output circuit.

FIG. 3 shows slit light 3 which has passed through slit 2.
And the light receiving surface of the light receiving element 5 that receives the slit light 3 and the running object 4 to be inspected. Subject 4 of 1
The average twist length is about 1 mm, and the running speed is 3 seconds per second.
When it is mm, the output signal of the light receiving element 5 contains an AC component of about 3 Hz. FIG. 4 shows the voltage waveform of each part of the light receiving system circuit. The output of the filter 7, for example a low-pass filter, has an AC waveform of, for example, 3 Hz as shown in FIG. 7A. However, if this subject suddenly disappears at time t ₁ or stops, the output of the filter 7 becomes 0. become.
The one-shot timer 8 outputs a triangular waveform with a fundamental frequency of 3 Hz with respect to the above-mentioned AC waveform of 3 Hz, but after time t ₁ , the potential rises at a time constant C (R ₁ + R ₂ ) and eventually rises. , At time t ₂ , the comparison voltage E ₃ of the comparator 9 is exceeded. At this time, the output of the comparator 9 is inverted from the L level to the H level.

In the output circuit of the present invention, in addition to the above-mentioned embodiment, for example, after the sine wave output of the selection circuit is shaped into a square wave, the pulse width is measured with a clock pulse, or the sine wave is detected. A known electronic circuit technique such as differentiating the output to detect the presence or absence of the differentiated signal can be used. Further, the light receiving element of the present invention may directly receive the projected image of the subject, or may receive it via an optical system such as a lens.

[0012]

According to the present invention, it is possible to detect the presence or absence of running without changing the running trajectory of the subject and without contacting the subject. Therefore, it can be easily implemented only by adding this device without changing the conventional device. Further, for example, it is possible to cope with a wide range of traveling speeds from a low speed of 1 mm / second to a high speed of several meters / second.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention.

FIG. 2 is a circuit diagram showing an embodiment of the output circuit section of FIG.

[FIG. 3] is an operation explanatory view of the optical system of the present invention.

FIG. 4 is an explanatory view of the operation of the electric circuit system of the present invention.

[Explanation of symbols]

 1 ... Light source 2 ... Slit 3 ... Slit light 4 ... Subject 5 ... Light receiving element 6 ... AC amplifier 7 ... Filter 8 ...・ One-shot timer 9 ・ ・ ・ ・ Comparator

Claims (1)

[Claims] 1. A light source with a slit for irradiating the subject with light only in a direction intersecting the traveling direction of the subject, a light receiving element for receiving a slice projection image of the subject by the light source with the slit, and an electric charge of the light receiving element. An apparatus for detecting the presence / absence of traveling of a linear body, which has a selection circuit for extracting an AC component in a predetermined frequency range from an output signal and an output circuit for issuing a detection signal when the AC component falls below a predetermined value.