JPS5829440B2 - Failure detection device for optical safety equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a failure detection device for an optical safety device used in a press machine or the like.

Light beam safety devices are used in press machines and the like to ensure safety.

This light beam type safety device projects one or more light beams into a dangerous area, and when this light beam is blocked by a part of the human body, it outputs an emergency stop signal, and this signal causes the press machine to stop. It is designed to stop the slide, etc.

By the way, the conventional optical safety device described above may no longer function as a safety device if an abnormality occurs in the light-emitting element that projects the light beam, the light-receiving element that receives the light beam, or their peripheral circuits. If you put your hand, etc. into the dangerous area without realizing it, you may lose your hand, which is very dangerous.

However, the current situation is that conventional optical safety devices do not detect abnormalities in light emitting elements, light receiving elements, and their peripheral circuits at all.

The present invention has been made in view of the above circumstances, and has an object to detect abnormalities in the light emitting element, light receiving element, and their peripheral circuits of a light beam safety device, to ensure the operation of the light beam safety device, and to improve safety. With the goal.

For this purpose, in the present invention, the input signals of the light emitting elements are scanned so as to be sequentially cut off, and if an emergency stop signal is not output from the optical safety device during this scanning, this is detected as an abnormality.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a failure detection device for a light beam safety device according to the present invention will be described in detail with reference to an embodiment shown in the accompanying drawings.

FIG. 1 shows an embodiment of a failure detection device for a light beam safety device according to the present invention, in which the present invention is applied to a light beam safety device for a press machine.

The light emitting signal generation circuit 1 includes light emitting elements 2a, 2b, 2
Light emitting signals Sa and Sb for causing light to emit light c and 2d
, Sc, and Sd, and these light emission signals 5a to 8d are sent to gate circuits (two-man NAND circuits) 3a, respectively.
.

It is added to each light emitting element 23-2d via 3b, 3c, and 3d.

The light emitting elements 2a to 2d project light beams onto a dangerous area such as a slide passing portion of a press machine, and are made of, for example, light emitting diodes.

Light receiving elements 4at correspond to the light emitting diodes 2a to 2d.
4b, 4c, and 4d are arranged.

When receiving the light beams projected from the light receiving elements 2a to 2d, a light reception signal is outputted, and this signal is applied to the synchronization circuit 5.

Further, the synchronization circuit 5 is supplied with light emission signals 5a to 8d from the light emission signal generation circuit 1.

The synchronization circuit 5 compares the light emission signals 5a to 8d and the corresponding light reception signals, and if both signals are present, outputs the signal to the corresponding output lines lla, lb, lc, and ld, and also outputs the light emission signal. However, if there is no corresponding light reception signal, it is assumed that the light beam is blocked and no signal is output to the corresponding output line.

The synchronization circuit 5 may be constructed using a group of AND circuits for each of the light emission signals 5a to 8d and the corresponding light reception signal, or a group of exclusive OR circuits for the exclusive OR of both. I can do it.

The emergency stop signal generating circuit 6 aggregates the signals on the output lines 1la-ld of the periodic circuit 5, and outputs a high level signal if all of the signals are present, and outputs a low level signal if any of the signals is absent. This circuit 6 outputs a level signal, and can be composed of, for example, a four-man power AND circuit.

The output of the emergency stop signal generation circuit 6 is applied to the relay coil 7, and when the output of the circuit 6 is at a high level, the relay coil 7 is energized, and when the output of the circuit 6 is at a low level, the relay coil 7 is demagnetized.

As will be detailed later, the relay coil 7 is
When demagnetized, the relay contact 7a is opened to give an emergency stop signal to the press.

The contact 8a is a relay contact that closes when the relay coil 8 shown in FIG.
As before, the slide of the press (not shown) is demagnetized when it is rising and the safety device does not need to operate.

The OR circuit 9 and the OR circuit 10 form a flip-flop F/F, and when the input S applied to the inverting input terminal of the OR circuit 9 becomes a low level, the output Q of the OR circuit 9, which is a set output, becomes a high level. When the signal R applied to the inverting input terminal of the OR circuit 10 becomes low level, the output Q of the OR circuit 9 becomes low level.

Further, the output Q of the OR circuit 10 is an inverted output of the set output Q, and this signal is applied to the reset terminal H of the counter 12 via the inverter 11.

The counter 12 is a binary counter, and the counter 12 is a human-powered counter.
A signal from a NAND circuit 17, which will be described later, is added to , and counts up when the signal from the NAND circuit 17 falls.

The count value of the counter 12 is added to the decoder 13 and converted to BCD.
converted to code.

Therefore, when the count value of the counter 12 is 0, only the output line L6 of the decoder 13 indicating 0 is at a low level, and the remaining signals on the output lines L1 to L9 indicating 1 to 9 are at a high level.

Note that the capacitor 30 is for resetting the flip-flop F/F when the power is turned on.

That is, when the power is turned on, the voltage of the capacitor 30 rises from a low level to a high level according to a time constant determined by the resistance value of the resistor 29 and the capacitance value of the capacitor 30. The circuit was initially cleared.

It is now assumed that the relay coil 8 (FIG. 2) is demagnetized, its relay contact 8a is open, and the count value of the counter 12 is O.

At this time, the signal S applied to the inverting input terminal of the OR circuit 9 forming a flip-flop becomes low level, and the output Q of the OR circuit 9 becomes high level.

This signal is applied to the NAND circuit 15a.

The NAND circuit 15a is a two-man powered NAND circuit, and the other input terminal is the output line L of the decoder 13.

A signal inverted by the inverter 14a is added to the signal.

Here, since the count value of counter 12 is O, decoder 1
3 output line L.

The signal is at low level, the NAND condition of the NAND circuit 15a is satisfied, and the low level signal is passed to the NAND circuit 3a.
Add to.

As a result, the NAND circuit 3a is closed, and the light emission signal Sa from the light emission signal generation circuit 1 is cut off.

Note that the other NAND circuits 3b, 3c, and 3d have output lines L1. L2. A two-man NAND circuit 15b in which signals obtained by inverting the L3 signal by inverters 14b, 14c, and 14d, respectively, and the output of the NAND circuit 17 are added in common.
, 15c, and 15d are added. At this time, the outputs of the output line LII2°K3 of the decoder 13 are all at high level, so the NAND circuits 15b, 15c, and 15d
The NAND condition is not satisfied, and the NAND circuits 3b, 3c, 3d
are all open.

Therefore, only the light emitting element 2a corresponding to the light emission signal Sa is turned off.

As a result, the output of the light-receiving element 4a corresponding to the light-emitting element 2a disappears, and at the same time, the output line l! of the synchronizing circuit 5! The signal d also disappears, and the output of the emergency signal generation circuit 6 becomes low level.

The output of the emergency stop signal generation circuit 6 is inverted by an inverter 16 and applied to a NAND circuit 17.

The NAND circuit 17 is a two-man NAND circuit, and the signal from the output line LR of the decoder 13 is applied to the other input terminal via an inverter 14d, a NAND circuit 15d, and a jumper line 18.

Here, since the signal on the output line LR of the decoder 13 is at a high level, the output of the inverter 14d is at a low level, the NAND condition of the NAND circuit 15d is not satisfied, and the signal applied to the NAND circuit 17 is at a high level.

Therefore, the NAND condition of the NAND circuit 17 is satisfied, and a signal falling from a high level to a low level is applied to the counter 12's manual count CU.

As a result, the counter 12 counts up.

Then, the output line L of the decoder 13.

The signal on the output line L1 changes from low level to high level, and the signal on the output line L1 changes from high level to low level.

Output line L.

When the signal becomes high level, the NAND condition of the NAND circuit 15a is no longer satisfied, and the output of the NAND circuit 15a becomes high level, opening the NAND circuit 3a and lighting the light emitting element 2a again.

In other words, all the light emitting elements 2a to 2d are turned on, so the output of the emergency signal generation circuit 6 becomes high level, and the NAND circuit 1
The NAND condition of 7 no longer holds true.

However, since the signal on the output line L1 becomes low level, the NAND condition of the NAND circuit 15b is satisfied this time, and a low level signal is applied to the NAND circuit 3b, blocking the light emission signal sb and corresponding to the light emission signal sb. The light emitting element 2b is turned off.

Therefore, the output signal of the light receiving element 4b corresponding to the light emitting element 2b disappears, the output of the emergency signal generating circuit 6 becomes low level, and the counter 12 counts up when the output of the NAND circuit 17 falls.

In this way, the NAND conditions are satisfied in the NAND circuits 15a to 15d sequentially according to the count value of the counter 12, and the outputs of the NAND circuits 15a to 15d cause the NAND circuits 3a to 3d to
scan to close sequentially.

That is, from the light emitting signal generation circuit 1 to each of the light emitting elements 2a to 2d
The scanning is performed so as to sequentially cut off the light emitting signals S a - S d applied to the light emitting elements 2 a to 2 d, thereby sequentially turning off the light emitting elements 2 a to 2 d.

As a result of this scanning, when the count value of the counter 12 becomes 3 in decimal notation, the output of the decoder 13 becomes low level, and the NAND condition of the NAND circuit 15d is satisfied.

Therefore, the output of the NAND circuit 15d becomes low level, and this signal is applied to one input terminal of the NAND circuit 17 via the jumper wire 18, so the NAND circuit 17 is closed and the counting of the counter 12 is stopped.

Further, the output of the NAND circuit 15d taken out via the jumper wire 18 is applied to an input NAND circuit 20 which is inverted by an inverter 19.

The other input terminal of the NAND circuit 20 is the relay contact 8a.
and a signal from the relay contact 7c, which is opened by excitation of the relay coil 7, are added.

The signal from the relay contact 8a is at a low level when the relay contact is open, and at a high level when the relay contact is closed.

Further, the signal from the relay contact 7c is grounded through a resistor 21, and is at a high level when the relay contact IC is closed, and at a low level when the relay contact 7c is open.

Therefore, when the relay contact 8a closes, the NAND condition of the NAND circuit 20 is satisfied, and the Loreherno signal is applied to the inverting input terminal of the flip-flop 7'F,/-,p(7) OR circuit 10.

As a result, the output of the OR circuit 10 becomes high level, and this signal is applied to the reset terminal R of the counter 12 via the inverter 11, thereby resetting the counter 12.

When the counter 12 is reset, the output of the decoder 13 is on line L.

All signals except flip 7 become high level, and flip 7
Since the output of the OR circuit 9 of the 0-tube F/F also becomes low level, the NAND conditions of the NAND circuits 15a to 15d no longer hold, and all of the NAND circuits 3a to 3d are opened.

As a result, the output of the emergency stop signal generating circuit 6 becomes high level, and the checking of all light beams is completed.

The above explanation is based on the light emitting elements 2a to 2d and the light receiving elements 4a to 4.
This is related to the operation when there is no abnormality in the light emitting elements 2a to 2d or 4a to 4d and their peripheral circuits.
4d or their peripheral circuits, the output of the emergency signal generating circuit 6 will not go to low level even if the light emitting signals Sa"Sd applied to the light emitting elements 2a to 2d are sequentially cut off, and the relay coil T remains excited.

FIG. 2 shows an example of the press control circuit according to the above embodiment.

Relay coil 8 operates relay contacts sb, 8c, 8d, and 8a (Fig. 1), and when relay coil 8 is demagnetized, contacts 8a, 8b, and ad open, and relay coil 8 closes. When the contact point 8 is excited, the contacts 8a, 8b, and 8d are closed, and the contact point 8c is opened.

Contact point 8c in the figure. 8d only shows the contact portion and is not wired, but the contact 8c confirms whether the relay coil 8 is energized or de-energized, and the contact 8d closes to enable press operation, and opens to disable press operation. , are actually connected to appropriate locations in the press circuit.

The rotary cam switch 22 operates according to the stroke angle of the press, and has two contacts 22a and 22.
It has b.

This contact point 22a. The operation of 22b is illustrated in FIG. 3.

In other words, when the stroke angle of the press is from 180 degrees (bottom dead center) to 300 degrees as shown by crosshatching, the contact point 22a
is opened, contact 22b is closed, and from 300 degrees to 180 degrees, contact 22a is closed and contact 22b is open.

This is a time when the slide of the Huffless (not shown) is rising while the stroke angle of the press is from 180 degrees to 300 degrees, and there is no need for the safety device to operate.

Contact point 23 is connected to a press stroke angle of 30 degrees by a signal from a press clutch/brake control circuit (not shown).
This is a relay contact that closes when the temperature is above 0 degrees and the press is ready to start.

Note that a relay coil that operates this relay contact 23 is not shown.

Contacts 24 and 29 are the clutch brake solenoid valve (
This is a contact that opens when the press (not shown) is energized, that is, during press operation, and remains open during press operation.

contact? A and 7b are operated by the relay coil 7 shown in Fig. 1. When the relay coil 7 is energized, the contact 7a is closed, the contact 7b is open, and when the relay coil 7 is demagnetized, the contact is closed. The contact 7a is opened and the contact 7b is closed.

Here, the contacts 22b, 24, 29, 7a are the emergency stop circuit 2
5 operating conditions are determined.

That is, only when all of the contacts 22b, 24, 29, and 7a are open, the emergency stop circuit 25 is operated to stop the slide of the press.

The emergency stop circuit 25 stops the slide of the press when the power supply from the line 26 is stopped, but the details are not shown because it is not related to the gist of the invention.

Further, the emergency stop ink lock 27 is used to emergency stop the press by an element other than the safety device related to the present invention, and is not directly related to the present invention.

Further, number 28 is a no-fuse breaker of the press control circuit.

When the stroke of the press is between 180 degrees and 300 degrees, the contact 22a of the rotary cam switch 22 is open and the contact 22b is closed, as shown in FIG. 2, and the relay coil 8 is demagnetized by the opening of the contact 22a. , contact 2
2b is closed, power is supplied to the emergency stop circuit via the line 26 and the contact 22b, inhibiting the operation of the emergency stop circuit.

The safety device is checked while the press stroke is between 180 degrees and 300 degrees.

That is, when the relay coil 8 is demagnetized, the relay contact 8a (Fig. 1) is open, and the flip-flop F/F
is set, and the NAND circuits 3a to 3d are set as described above.
are sequentially closed, and each light emitting element 2a~ from the light emitting signal generation circuit 1 is closed.
Scanning is performed so as to sequentially block the light emission signals 5a to 8d applied to the signal 2d.

At this time, the output of the emergency stop signal generation circuit 6 alternately outputs a low level and a high level, and accordingly the relay coil 7 is demagnetized and excited to open and close one point 7a of the jJ tray. The stop circuit 25 is inhibited by the power supplied from the contact 22b of the rotary cam switch 22, so it does not operate.

If no abnormality is detected by this scanning, when the press stroke exceeds 300 degrees and the contacts 22a and 23 of the rotary cam switch 22 close, the contacts 22a, 23,
A current flows to the relay coil 8 via 7b and excites the relay coil 8.

As a result, the relay contact 8a closes and press operation becomes possible, and since the contact 8a closes, the NAND circuit 20 (Fig. 1)
The NAND condition is satisfied, the flip-flop F/F is reset, the output of the emergency stop signal generation circuit 6 becomes high level, and the inhibition of the safety device is released.

That is, when the light beams projected from the light emitting elements 2a to 2d are blocked by a part of the body or the like, the output of the emergency stop signal generation circuit 6 becomes a low level, and the relay coil 7 is demagnetized.
When the relay contact 7a opens, the power supply to the emergency stop circuit 25 is cut off, and the emergency stop circuit 25 is activated.

Note that the excitation of the relay coil 8 is self-maintained by remembering that the relay 7 has been turned off by the relay contact 8b, which is closed by the excitation of the relay coil 8.

This self-holding is released when the press stroke exceeds 180 degrees of the bottom dead center and the contact 22a of the rotary cam switch 22 opens, and the safety device is checked in the same manner thereafter.

However, if an abnormality is produced by the scanning, the relay coil 7 (FIG. 1) remains energized, the relay contact 7a closes, and the relay contact 7b remains open.

Therefore, press stroke 3o. Even if the contact point 22a1 and the contact point 23 of the rotary cam switch 22 close, the relay coil 8 is not excited and the contact point 8d does not close, making the press operation impossible and the press being brought to an emergency stop.

In this way, the light emitting elements 2a to 2d, the light receiving elements 4a to 4d, and their peripheral circuits of the safety device are checked every cycle of the press, and only when no abnormality is detected in this check, the next cycle of operation is possible. I try to do that.

In the above embodiment, the check period was set between 180 degrees and 300 degrees of the press stroke, but it is of course not limited to this, and may be set to any period that does not require the operation of the safety device. Good too.

This setting is made using the contact 22a of the rotary cam switch 22.
, 22b can be easily achieved by changing the operating angle.

Further, the present invention is not applicable only to press machines, but can be applied to any mechanical device equipped with a light beam safety device.

As explained above, according to the present invention, it is possible to completely check whether the light-emitting element, the light-receiving element, and their peripheral circuits of the optical safety device are operating normally, and the operation of the safety device can be ensured. can do.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the failure detection device for the optical safety device of the present invention, FIG. 2 is a block diagram showing an example of the press control circuit according to the embodiment, and FIG. It is a figure explaining operation of the rotary cam switch shown in a figure. 1...Light emission signal generation circuit, 2a to 2d...
...Light emitting element, 4a to 4d... Light receiving element, 5.
... Synchronous circuit, 6 ... Emergency stop signal generation circuit, 7, 8 ... Relay coil, 12 ...
... Binary counter, 13 ... Decoder, 2
5...Emergency stop circuit.

Claims (1)

[Claims] 1 A plurality of light emitting elements and a plurality of light receiving elements are arranged facing each other through a predetermined dangerous area, and blocking of any of the light beams projected from the light emitting element to the light receiving element via the dangerous area is the output of the light receiving element. A light beam type safety device that generates an emergency stop signal to a required device when detected based on the light emitting element includes a light emitting signal generation circuit that generates a light emitting signal for each light emitting element to cause the light emitting element to emit light; a plurality of gate circuits respectively provided correspondingly to open and close light emission signals applied from the light emission signal generating circuit to the light emitting element; and a scanning circuit configured to scan the gate circuits so as to sequentially close the gate circuits; A failure detection device for a light beam safety device, wherein if the emergency signal is not generated even though the gate circuit is closed by scanning, this is detected as a failure of the light beam safety device.