JPS5822474Y2 - Safety device with operation confirmation device - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a safety device for a machine tool, etc., which has an operation confirmation device.

In a machine tool, for example, a press machine 1 as shown in FIG. 1, for the safety of the worker, there is a safety device that disables the press machine 1 when the worker approaches the work space 2 of the press machine 1. are usually combined.

There are two known types of such safety devices: a light beam type and a capacitive type.

The optical safety device is configured as shown in FIG. 1, for example.

A light projecting section 3 is arranged on the left side of the working space 2 of the press machine 1, and a light receiving section 4 that receives light from the projecting section 3 is placed on the left side of the working space 2 of the press machine 1.
Located on the right side.

As shown in FIG. 2, the signal from the light receiving section is applied to the base of the transistor 6 of the output relay circuit via the amplifier 5, turning on the transistor 6 and energizing the output relay R.

The auxiliary a contact or normally open contact Ra of the output relay R is placed between the power supply and the control circuit (not shown) for the press machine.

Therefore, as long as the operator does not bring his hand or workpiece close to the work space 2, the light from the light projector 3 will be incident on the light receiver 4 without being blocked, and the light receiver 4 will receive a high level light reception signal. is applied to transistor 6 via amplifier 5, turning transistor 6 on and keeping output relay R energized, thereby keeping output relay contact Ra closed.

Therefore, in the light condition, the press machine remains in its normal working condition.

If the light from the light projecting section 3 is blocked by the operator's hand or the workpiece, the light receiving section 4 applies a proximity signal, that is, a low-level light blocking signal, to the transistor 6 via the amplifier 5.

Therefore, the transistor 6 is returned to the off state, the output relay R is deenergized, and the attached a contact is returned to the open state, rendering the press machine 1 inoperative.

However, when the slide 7 of the press machine is on its upward stroke, there is no danger for the operator to approach the work space.
In order to override the opening of the relay contact Ra during the slide upstroke and keep the press operating continuously, a override switch 8 is normally connected in parallel to the relay contact Ra.

This invalidation switch 8 is usually a limit switch,
A cam that rotates in synchronization with the rise and fall of the slide 7 closes the slide 7 during movement from the bottom dead center to a point slightly past the top dead center.

If the closing period of the invalidation switch 8 is illustrated, it will be as shown in the shaded area in FIG.

With this configuration, even if the light from the light projecting section 3 is blocked by the work of taking out the product and feeding the work piece performed during the upward stroke of the slide 7 from the bottom dead center to the top dead center, Since the disable switch 8 is in the closed state, the opening of the relay contact Ra is disabled, and the press work can be continued without stopping the press machine.

However, if the disabling switch 8 is provided as described above, as long as the light is blocked during the upward stroke of the slide 7, it is impossible to know whether the safety device is operating properly or not.

For example, even though the light from the light projector 3 is blocked for some reason, the output relay is not deenergized and the contact Ra
If a failure occurs in which the slide does not return to the open state, the failure will not be discovered as long as the light is blocked only during the slide's upward stroke, and the worker will not be able to access the workspace 2 during the slide's downward stroke.
It was only discovered when the press machine did not stop and an accident occurred when the light was blocked as it approached.

Therefore, the present invention aims to provide a safety device equipped with a device for checking the operation of the safety device during the period in which the safety device is inactive, so as to prevent the above-mentioned accidents from occurring.

That is, according to the present invention, there is a safety device that issues a proximity signal to stop the operation of the machine when a worker approaches a predetermined area of the machine, and a safety device that stops the operation of the machine while the machine is in a predetermined work period. and a device for disabling the operation of a safety device, the first stable state changes to a second stable state when the disabling device operates to disable the safety device. and a bistable circuit configured to return from the second stable state to the first stable state in response to a proximity signal emitted by the safety device during the predetermined work period; An operation check device is provided for stopping the machine when the bistable circuit is in a second stable state at the end of the period.

By doing this, you will be sure to check whether the safety device is working correctly every time the safety device is disabled and the machine is not dangerous to the operator, and if there is an abnormality in the safety device, it will be corrected. It can be detected immediately and the machine is stopped as soon as the ineffective period ends to prevent the machine from entering operations that are dangerous to the worker, so the worker is never exposed to danger due to an abnormality in the safety device. Not at all.

When the device of the present invention is applied to a press machine, the above-mentioned predetermined working period can approximately correspond to the upward stroke of the slide.

In a typical embodiment of the present invention, the bistable circuit described above is a set/reset type flip-flop, and the first state is whether the Q output is at a high level or a low level. good.

The second state is a state in which the Q output is at a low level in the former case, and a state in which the Q output is at a high level in the latter case.

FIG. 4 is a block diagram of a safety device with an operation check device according to the present invention applied to the press machine shown in FIG. 1.

The detection signal from the switch 10 which detects the operation of the invalid switch in conjunction with the invalid switch 8 in FIG.
1 is connected to the set power S of the rising-trigger type flip-flop 12.

On the other hand, the signal from the light receiving section 4 that receives the light from the light projecting section 3 is connected to the reset manual R of the flip-flop 12.
The Q output of the flip-flop 12 is connected to one input of the OR circuit 13.

The other input of the OR circuit 13 is connected to a detection switch 10.
A detection signal from AN is applied, and the output of the OR circuit 13 is AN.
It is connected to one input of the D circuit 14.

The output of an OR circuit 15 is connected to the other input of the AND circuit 14, and the detection signal from the switch 10 and the signal from the light receiving section 4 are applied to two inputs of the OR circuit 15, respectively.

The output of the AND circuit 14 is connected to one input of an AND circuit 16, and the other input of the AND circuit 16 directly receives a signal from the light receiving section 4.

The output of the AND circuit 16 is connected to the base of the transistor 6 of the output relay circuit via the amplifier 5, as in the case shown in FIG.

Therefore, it can be said that the safety device shown in FIG. 1 is provided with the operation confirmation device enclosed by the dotted line in FIG. 4 in parallel via the AND circuit 16.

Further, the input of the differentiator 11 is grounded via the b contact Tb of a timer T, such as a time relay or a time delay relay, and the timer T is energized by turning on the power of the press machine and the auxiliary equipment. It is done like this.

Timer T and its b contact constitute an automatic setting circuit of the operation confirmation device shown in FIG.

Next, with reference to the waveform diagram at each point of the circuit shown in Figure 5,
The operation of the operation confirmation device shown in the figure will be explained.

First, power on the press machine and attached equipment is turned on.

At this time, the slide 7 of the press machine is located at the top dead center, the override switch 8 is in the ON state, and the switch 10 that detects the operation of the override switch outputs a high level signal.

However, since the b contact Tb of timer T is still closed, the differentiator 110 input is at a low level.

On the other hand, the light receiving section 4 receives the light from the light projecting section 3 and outputs a high-level light passing signal.

After that, when the delay time of the timer T elapses, the b contact Tb is opened, the input of the differentiator 11 changes from low level to high level, and the differentiator 11 flip-flops the positive spike pulse signal PPo. is applied to the set input of pin 12 to set the flip-flop.

In this way, when the power is turned on, the flip-flop 12
is automatically set to the set state.

Next, the workpiece is fed into a press machine.

At this time, when the light from the light emitter is blocked and the proximity signal from the light receiver rises from a low level to a high level,
Flip-flop 12 is reset and its Q output goes high.

Thereafter, when the press machine is started, the slide 7 begins to descend from the top dead center, and the override switch 8 is opened.

With the opening of the invalid switch 8, the detection signal from the switch 10 becomes low level, but the spike pulse signal PNI in the negative direction from the differentiator 11 passes through the flip-flop 1.
2 cannot be triggered.

When the slide 7 reaches the bottom dead center, the invalid switch 8 is closed and the detection signal from the switch 10 becomes low level.
The flip-flop 12 is set by the positive spike pulse signal PPI from the differentiator 11 generated at this time, and its Q output becomes a low level.

While the slide 7 is rising from the bottom dead center to the top dead center, the product is taken out and a new workpiece is fed in, the light from the light emitter is blocked, and the signal from the light receiver changes from low level to high level. When the level rises, flip-flop 12 is reset and the Q output goes high.

After that, the slide 7 reaches the top dead center and descends again, the invalid switch 8 is opened, the detection signal from the switch 10 becomes low level, and the differentiator 11 outputs a spike pulse signal PN2 in the negative direction. As mentioned above, the state of flip-flop 12 does not change.

From the time when the press machine is powered on until the spike pulse signal PN2 is generated, as shown in FIG. 5, either the output of the switch 10 or the Q output of the flip-flop is always at a high level. , the output of the OR circuit 13 is at a high level, and either the output of the light receiving section 3 or the switch 10 is always at a high level, so the output of the OR circuit 15 is at a high level.
4 output is maintained at a high level.

Therefore, while the slide 7 is rising to the bottom dead center (actually, while the overriding switch 8 is closed), the light is blocked, and the light blocking signal is generated, and as long as the slide 7 is operating normally. ,A
A low level signal is not applied to the ND circuit 16.

If light shielding occurs while the slide 7 is descending, the state of the flip-flop 12 does not change, but since the two inputs of the OR circuit 15 both become low level, the output of the AND circuit 14 becomes low level.

Therefore, the two inputs of the AND circuit 16 both become low level, the output relay R is deenergized, and its relay contact Ra (FIG. 2a) is opened. At this time, the override switch 8 is in the open state, so the press The machine is stopped.

Therefore, a normal safety operation is performed for blocking light during the lowering period of the slide 7.

Now, if the proximity signal, that is, the light blocking signal is not applied for some reason, that is, if the signal from the light receiving section 4 never changes to a low level during the rising period of the slide 7, the graph in FIG. As shown, since the flip-flop 12 is not reset, its Q output is maintained at a low level, and when the detection side signal of the switch 10 becomes a low level due to the opening of the invalid switch 8, the output of the OR circuit 13 becomes a low level. , the outputs of the AND circuits 14 and 16 change to a low level, the output relay R is deenergized, the relay contacts are opened, and the press machine stops immediately after the slide 7 begins to descend from top dead center.

In this way, if a proximity signal, that is, a light blocking signal is not generated while the override switch 8 is closed, the press machine is stopped the moment the slide 7 begins to descend, and the work is prevented from approaching the work space while the slide is descending. It is possible to prevent accidents that may occur due to this, and to notify that there is a malfunction in the safety device.

In the safety device with an operation check device shown in FIG. 4, when there is a line directly connected from the light receiving section 4 to the AND circuit 16 as shown in the figure, the OR circuit 15 and the AND circuit 14 are omitted, and the OR circuit 13 is It will be obvious to those skilled in the art that similar results can be obtained by directly feeding the output to the AND circuit 16.

In addition, since the operation confirmation device shown in Fig. 4 does not respond to light interruption while the disabling switch is closed, the disabling relay connected in parallel with the output relay is omitted, and the switch 10 is opened and closed by a cam that moves in synchronization with the slide. It will be clear to those skilled in the art that even if configured to do so, similar effects can be obtained.

In this case, the line directly extending from the light receiving section 4 to the AND circuit 16 and the AND circuit 16 are omitted.

The safety device with an operation confirmation device shown in Fig. 4 can be applied not only to the light beam type safety device shown in Figs. 1 and 2, but also to the capacitive type safety device shown in Fig. 6. .

The capacitive safety device has a sensing loop 20 placed, for example, in front of the working space 2 of the press machine 1;
The apparatus is equipped with a proximity detector that detects a change in the capacitance between the sensing loop and the ground when a worker or object approaches zero, and emits a proximity signal when the worker or the like approaches.

The structure and operation of this capacitive proximity detector and capacitive safety device are well known to those skilled in the art and will not be described in detail here.

In the case of a capacitive safety device, the output of a proximity detector 21 having a sensing loop 20 is connected to an operation confirmation device and an AND circuit 16 via an inverter 22, as shown in FIG.

As a result, as long as the operator does not approach the sensing loop 20, the output relay R is maintained in the energized state, and when the proximity signal is output, the output relay R is deenergized and the contact Ra returns to the open state.

Capacitive proximity detectors operate very delicately and are adjusted to generate a proximity signal when a worker or the like approaches to a desired distance.

However, the sensing zone may change depending on the size of the sensing loop, the sensitivity of the circuit, the influence of surrounding objects, etc., and a dead zone may be created within the sensing loop.

The operation checking device according to the present invention is particularly advantageous in that it can detect the occurrence of a dead zone, since the press machine is stopped when a workpiece is removed and fed through such a dead zone.

Figure 8 shows another safety device with an operation confirmation device according to the present invention.
Here are two examples.

Proximity detector 2 with sensing loop 20 as shown in FIG.
The output of No. 1 is connected to the set input S of the falling retrigger type flip-flop 23, and the Q output thereof is connected to the base of the transistor 6 of the output relay circuit via the AND circuit 24 and the amplifier 5, and further connected to the base of the transistor 6 of the output relay circuit. The output of is connected to the other input of the AND circuit 24 via an inverter 25.

The set human power S of the flip-flop 23 is grounded via the normally open push button switch 26, and the reset human power R is similarly grounded via the override switch 8.

This override switch 8 is placed here instead of being connected in parallel to the output relay contact Ra.

The reset power R of the flip-flop 23 is further connected to the connection point between the collector of the transistor 6 and the output relay R.

The safety device with operation confirmation device shown in FIG. 8 operates as follows.

After turning on the power of the press machine, press the push button switch 24 to set the flip-flop 23 and turn on the transistor 6.
energizes the output relay R.

Next, by starting the press machine, the slide descends from the top dead center to the bottom dead center, and at the moment when the slide reaches the bottom dead center, the invalidation switch 8 is closed and the flip-flop 23 is reset manually R.
falls to the ground voltage, resetting the flip-flop 23 and cutting off the transistor 6, at the same time an output relay energization path is formed from the output relay R to ground via the override switch 8, and the output relay is continuously maintained in the energized state.

While the slide is rising, the product is taken out and the workpiece is fed in, and the proximity detector 21 applies the proximity signal S to the set input of the flip-flop 23, setting the flip-flop and keeping the transistor 6 in a conductive state. do.

Therefore, from the time when the proximity signal S is generated until the disabling switch 8 is opened, there are two energizing paths for the output relay R, one via the disabling switch 8 and the other via the transistor 6. After passing through top dead center and the override switch 8 is opened, the output relay R is energized by the transistor 6 only.

In this way, as long as the proximity signal is generated during the rising period of the slide (more precisely, during the closing period of the invalid switch 8), the 9th
As shown in the graph of the figure, the output relay R is kept energized and its relay contacts Ra are kept closed to ensure the operation of the press machine.

If for some reason the proximity signal is not supplied to the set input of the flip-flop 23 during the rising period of the slide, the Q output of the flip-flop 23 remains at the A level, and the transistor 6 remains cut off. .

Therefore, as shown in FIG. 9, the moment the invalidation switch 8 is opened, the output relay R is deenergized, the relay contact Ra returns to the open state, and the press machine stops.

When using the optical proximity detector shown in Figure 1 instead of the capacitive proximity detector in the operation check device shown in Figure 8, connect the output of the light receiving section to the set input of the knob flop via an inverter. .

As described above, the device for checking the operation of a safety device according to the present invention can detect malfunctions in the safety device and automatically stop the machine, thereby preventing accidents that may occur if the operating device continues to operate. can be prevented.

Further, although an example in which the present invention is applied to a press machine has been described, it will be clear to those skilled in the art that the present invention can be applied not only to press machines but also to other machine tools and working machines.

[Brief explanation of drawings]

Figure 1 is a schematic perspective view of a press machine equipped with a light beam safety device, and Figure 2 is a circuit diagram of the light beam safety device shown in Figure 1.
FIG. 3 is a diagram showing the operating period of the override switch parallel to the output relay contact of FIG. 2, FIG. 4 is a block diaphragm of an embodiment of the operation confirmation device for the safety device according to the present invention, and FIG. are waveform diagrams at each point of the circuit in Figure 4, Figure 6 is a schematic perspective view of a press machine equipped with a capacitive safety device,
FIG. 7 shows a block diaphragm of a modification of the embodiment of FIG. 4 combined with a capacitive safety device, FIG. 8 shows a block diaphragm of another embodiment of the operation confirmation device according to the present invention, and FIG. The figure is a waveform diagram at each point of the circuit of FIG. 1...Press machine, 3...Light projection part, 4
... Light receiving section, 5 ... Amplifier, 6 ...
...Transistor, R...Output relay, Ra
...Output relay a contact, 8...Disable switch, 10...Switch, 11...
- Differentiator, 12... Flip-flop path, 20... Sensing loop, 21... Capacitive proximity detector, 22... Inverter, 23...
...Flip-flop, 24...AND
Circuit, 25... Inverter, 26...
push button switch.

Claims (1)

[Scope of utility model registration request] A safety device that issues a proximity signal to stop the operation of the machine when a worker approaches a predetermined area of the machine, and disables the operation of the safety device while the machine is in a predetermined working period. and a device for disabling the safety device, when the disabling device operates to disable the safety device, the device changes from a first stable state to a second safe state,
a bistable circuit configured to return from the second stable state to the first stable state in response to a proximity signal issued by the safety device during the predetermined work period, and the predetermined work period ends. A safety device comprising an operation confirmation device that stops the machine when the bistable circuit is in a second stable state.