JPH0412010Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] This invention operates a work end switch each time a worker finishes work in the process for which he or she is assigned, and when all workers' work end switches are pressed, the conveyor The present invention relates to a conveyor line safety device that moves the conveyor line in a tact manner and forms a light beam along the conveyor line to stop the conveyor movement if an intruder such as a worker is detected during the conveyor line movement.

[Problems that conventional technology and ideas try to solve]

As this type of light safety device, conventional LED
A photoelectric switch type is well known, which uses a light source as a light source and has light receiving elements facing each other along a conveyor line.
However, in this case, since the divergence angle of the light beam becomes large, the reflected light from the surface of the conveyed object etc. enters the light receiving element, and even if the light beam is interrupted, the light reception signal continues to be generated. There is a problem of lack of reliability. To avoid this,
It would be better to narrow the distance between the LED and the light receiving element, but
A large number of photoelectric switches are required, and conversely, there is a possibility that the light beam will not be incident on the light receiving element due to vibration. Furthermore, if you place only the light-receiving part and the light-emitting part along the line for explosion-proofing purposes, and try to connect the device bodies placed outside the line with an optical fiber, the transmission loss will increase, making it difficult to obtain high detection accuracy. It becomes difficult.

In view of these points, the present invention aims to provide a more reliable optical safety device for a tact-moving conveyor line in a factory.

[Means for Solving the Problems] In order to achieve this objective, the present invention uses a light splitter to divide the light beam emitted from the laser light source into a plurality of beams and emit them along the conveyor line.
And on the receiving side of each light beam, a photoelectric conversion element,
a signal level comparison circuit that generates an output signal when the photoelectrically converted electrical signal falls below a predetermined level;
A beam interruption detection circuit was provided for detecting, as a beam interruption signal, a signal whose time width is longer than the period of factory vibration among the output signals.

[Effect]

Each time the conveyor line moves in a tact, a plurality of narrow beams of laser light are formed along the conveyor line. Even if the output signal of the photoelectric conversion element is cut off due to vibration and an output signal is generated in the signal level comparison circuit, the frequency is sufficiently higher than that when a person cuts it off, so the beam cutoff detection circuit detects it as a beam cutoff. do not. When the light beam is interrupted by the intrusion of a worker or an outsider, the signal level comparison circuit outputs a signal with a longer time width, and the beam interruption detection circuit judges the length and outputs a beam interruption signal. .

[Example of idea]

1 and 2 show an embodiment in which the present invention is applied to an automobile painting line.

In FIG. 1, 1 is a conveyor that moves a car 2 in tact, and three pairs of light projecting lenses 8 and light receiving lenses 9 are mounted on a horizontal surface to form three light beams 7 along the conveyor. They are placed facing each other and separated by the length of the process. Each floodlight lens 8
The light-receiving lens 9 is connected to the main body 10 of the apparatus, which is installed at a separate position in consideration of the explosion-proof nature of the painting line, through optical fibers 6 and 6a. light beam 7
Further outside the position where is formed, there are work end switches 4 to 4c that are operated by the workers 3 to 3c of each process while leaving the line each time they finish their assigned work.
are arranged.

As shown in FIG. 2, the main body 10 of the apparatus operates a He-Ne laser oscillator 11 that operates while the conveyor control device 5 moves the conveyor 1 by one step when all the switches 4 to 4c are operated. The laser beam is divided into three parts by a light splitter 12 composed of three reflecting mirrors with a reflectance of 70%, 50%, and 100%, and each is sent to an optical fiber 6 through a condenser lens 13 and an optical fiber connector 14. It is designed to be done. Further, following the three light-receiving optical fibers 6a, three systems of optical systems each consisting of an optical fiber connector 16, a collimating lens 17, an optical filter 18 for noise removal, and a light-receiving element 19 are provided. This optical system includes an I/V conversion circuit 20 that converts the current detected by the light receiving element 19 into a voltage, an amplification circuit 21 thereof, and a signal level comparison circuit 22 that detects when the level of the amplified signal falls below a predetermined level. , a beam cutoff detection circuit 23 that detects a signal whose time width is longer than the period of factory vibration as a light beam cutoff signal, and a holding circuit 24 that holds the beam cutoff signal.
and an output circuit 25 that outputs a beam cutoff signal to the conveyor control device 5 when any one of these three holding circuits holds the beam cutoff signal. As a result, since only the optical fibers 6, 6a and lenses 8, 9 are installed in the line,
The in-line equipment becomes more compact, making installation and removal easier. At this time, since the optical fibers 6 and 6a transmit the laser beam, the loss is also reduced.

The operation of the safety device configured as described above is as follows.

While the conveyor 1 is stopped, the workers 3 to 3c operate their respective work end switches 4 to 4c each time they finish their own work, and leave the line to wait. All work end switch 4~4c
When is operated, the conveyor control device 5 moves the conveyor 1 by one step in tact, and during this movement, activates the He-Ne laser oscillator 11 to send the light beam 7 through the optical fiber 6 from the projection lens 8 to the conveyor. Fire 3 horizontally along line 1.

The three light beams 7 that entered the light receiving lens 9 are
Each signal is guided to the light receiving element 19 through the optical fiber 6a and converted into a current signal, converted into a voltage signal by the I/V conversion circuit 20, and amplified by the amplifier circuit 21. If the light beam 7 does not enter one of the light receiving lenses 9 due to factory vibrations, the output signal of the associated light receiving element 19 will be blocked or reduced. However, the frequency of such vibrations is typically 5Hz
As described above, even if a signal is output from the signal level comparison circuit 22, the beam interruption detection circuit 23 does not detect the beam interruption.

On the other hand, if an outsider blocks any one of the light beams 7, the workers 3 to 3c will
The output of the associated signal level comparison circuit 2 is cut off.
2 outputs a signal with a longer time width than the vibration, and the beam interruption detection circuit 23 determines that the light beam 7 is interrupted by a human, and sends a beam interruption signal to the holding circuit 24, which holds it even after the interruption is resolved. let As a result, the output circuit 25 causes the conveyor control device 5 to stop the movement of the conveyor 1. Since there are three light beams, such blocking is performed more reliably.

Figure 3 shows the safety device of the present invention applied to a non-explosion-proof, tact-moving press automation line.
The entire circumference of the press machine 30 is surrounded by three vertical light beams 31. That is, in one corner of the periphery, a light projection side optical system 32 is arranged which divides the emitted light from the laser oscillator of the apparatus main body 35 into three vertical beams and forms a light beam 31 along the press automation line. The three corners have incident light beams
Mirrors 33 to 33b that reflect in a 90° direction are arranged, and a light receiving optical system 34 is arranged behind the light projecting optical system 32 to receive and photoelectrically convert the three light beams from the mirror 33b. This light-receiving optical system is attached with a processing circuit similar to that described in FIG. 3 within the main body 35 of the apparatus.

[Effect of idea]

As described above, according to the present invention, since the light beam can be narrowed by using a laser beam, malfunctions due to reflections in the periphery can be prevented even when a single device monitors a longer distance. Also, its monochromatic nature facilitates noise removal. By detecting the cutoff time of the received signal, it is possible to prevent malfunctions caused by factory vibrations.
Due to the monochromaticity and high convergence of laser light, light can be transmitted to a target position using an optical fiber with low loss.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a schematic configuration of a safety device for a conveyor line according to one embodiment of the present invention, FIG. 2 is a diagram showing the main body of the device, and FIG. 3 is a diagram showing the configuration of a safety device according to another embodiment. FIG. 1... Conveyor, 6, 6a... Optical fiber,
7, 31...Light beam, 8...Light projection lens, 9...
...Light receiving lens, 11...Laser oscillator.

Claims (1)

[Scope of Claim for Utility Model Registration] Each time a worker finishes work in the process for which he or she is responsible, he or she operates a work end switch, and when all workers' work end switches are pressed, the conveyor is moved in a tact manner, and the conveyor is moved in a tact manner. In a conveyor line safety device that forms a light beam along the conveyor line to detect a person and stop conveyor movement, a light beam splitter is used to split the light beam emitted from a laser light source into multiple beams. At the same time, on the receiving side of each light beam, there is a photoelectric conversion element, a signal level comparison circuit that detects when the photoelectrically converted electric signal falls below a predetermined level, and A safety device for a conveyor line, each comprising a beam cutoff detection circuit that detects as a beam cutoff signal a signal whose time width is longer than the period of factory vibration among the output signals of the comparison circuit.