JPH07208690A - Light beam type safety device for machine tool - Google Patents

Abstract

PURPOSE:To improve the operating speed of a safety circuit of a machine tool by shielding two optical axes light, and simplify the configuration of a device. CONSTITUTION:In detection blocks B1 to B4 which correspond to optical axis- blocks, each of which consists of four optical axes, light-receiving element rows 8 to 11, decision by majority-gate ICs 16 to 19, and gates 20 to 23 are provided. When two or more optical axes are shut off in the respective detection blocks B1 to B4, the majority-gate ICs 16 to 19 output majority-signals. Further, when one or more optical axes are shut off, the gate circuits 20 to 23 output detection signals, and when two or more detection signals are outputted, the majority gate IC 26 outputs a majority-signal. The respective majority signals are outputted through the gates 24 and 25, or through the gate 25 to an emergency stopping device of press machines, etc.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light beam type safety device for a machine tool, and more particularly to working in a protected area defined by an optical axis of a light emitter / receiver provided at least in front of a machine tool such as a press machine. The present invention relates to a light beam safety device for a machine tool that can stop the operation of the machine tool by detecting a danger by blocking the optical axis when a person accidentally puts his / her hand or the like.

[0002]

2. Description of the Related Art Conventionally, in the case of a machine tool such as a press machine, in consideration of the danger, it is likely that an operator puts his / her hand in the protected area of the machine tool for work such as setting a workpiece. In this case, a safety device is attached to detect this and stop the operation of the machine tool. As the safety device, there is one in which at least a front surface of a machine tool is provided with a region protected by a light beam, and the operation of the machine tool is stopped when the light beam is blocked by an operator or a workpiece. For example, those described in JP-A-2-236098).

FIG. 3 is a perspective view showing an example of a light beam type safety device. In the figure, a light projector 1 and a light receiver 2 are arranged on the left and right sides of the front surface of the press machine 5, respectively. The projector 1 has a plurality of light emitting elements, and the receiver 2
The same number of light-receiving elements as the light-emitting elements are arranged in the vertical direction so as to face each other. The light projector 1 and the light receiver 2 of the press machine 5 are arranged so that the entire width of the press machine 5 is covered by a plurality of optical axes 4 formed by the light rays emitted from the light projector 1 toward the light receiver 2. It is arranged with an interval substantially the same as the width. When the optical axis 4 is interrupted during the operation of the press machine 5, the control device 3 operates by detecting this, and the clutch for transmitting the power of the prime mover to the press machine is disengaged to suddenly stop the operation of the press machine. I am trying.

By the way, depending on the shape of the material to be pressed, the end of the material may block the optical axis during pressing. In this case, even if the safety of work is ensured, the press machine cannot be started because the optical axis is blocked. Therefore, the press machine operates normally when only one optical axis is blocked, and the press machine cannot be started or stopped suddenly when two or more optical axes are blocked. Can be considered. A safety device of this type is called a two-optical-axis shading type.

FIG. 2 is an electric circuit diagram of a main part showing an example of the control device 3 used in the two-optical-axis light-shielding system, in which 16 optical axes are provided. Of the 16 optical axes, only one of the ends arranged at the top in FIG.
Exceptionally, a signal is output to stop the press machine when it is shut off. Other than that, it is set to stop the press machine when two or more arbitrary optical axes are blocked.

In the figure, the output signal of the OR gate G1 is used to stop the press machine, and when the signal becomes high level, the press machine is stopped. Each of the light-receiving element rows 8 to 11 has four light-receiving elements, and the detection signal thereof except for one of the end portions of the light-receiving element row 8,
The signals are input to 15 AND gates forming the gate ICs 13 and 14, respectively. The light receiving element rows 8 to 11 output a low level “L” signal when receiving the light emitted from the projector 1, and when not receiving light, that is, when the light is shielded, the output signal is a high level “H” signal. Output. Since the sync pulse generators 6 and 7 detect the presence or absence of the received light signal, the sync pulse is sequentially output, and this output signal is supplied to the AND gate.

As shown in the figure, the output signal s1 of the light receiving element at the end of the light receiving element array 8 is directly input to one of the OR gates G1. Therefore, when the light receiving element does not detect light, The signal s1 changes to high level and the OR gate G1
Output signal s0 also changes to a high level and the press machine is immediately stopped.

The output signal of the mono-multi (monostable vibrator) 12 is input to the other of the OR gates G1. When the output signals from any two or more light receiving elements other than the output signal from one of the light receiving elements included in the light receiving element rows 8 to 11 arranged at the end are at a high level, The output signal of the multi 12 becomes high level.
As a result, the output signal of the OR gate G1 becomes high level and the press machine is stopped.

That is, the flip-flop 15 is reset by the first sync pulse s3 output from the sync pulse generator 6. The gate ICs 13 and 14 are supplied when the second to sixteenth synchronization pulses supplied from the synchronization pulse generator 6 or 7 and the output signals (excluding the signal s1) of the light receiving element arrays 8 to 11 are at a high level. The output signal of each AND gate becomes high level, and this signal is supplied to the flip-flop 15 via the OR gate G2 or G6 and G3, and the flip-flop 15 is set.

On the other hand, the output signal of each AND gate is input to the AND gate G5 via the OR gate G2 or G6 and G4. At this time, the flip-flop 15
Is delayed and set by the delay circuit 16, so that the output signal of the AND gate G5 is at a low level only when the optical axis 4 is blocked and the output of one light receiving element changes to a high level. Therefore, the output signal of the mono-multi 12 does not change to a high level only when light is not detected by one light receiving element of the light receiving element rows 8 to 11, and the OR gate G1
Does not output an abnormal signal. However, when the light receiving element corresponding to the signal s1 does not receive light, an abnormal signal is exceptionally output as described above.

However, when light is not detected by one or more light receiving elements, the flip-flop 1 has already been detected.
Since 5 is in the set state, the AND gate G5 is immediately opened (becomes high level). As a result, the pulse signal is supplied from the monomulti 12 to the OR gate G1 and an abnormal signal is output, and the press machine suddenly stops.

[0012]

The above-mentioned conventional safety device has the following problems. That is, in the safety device, the gate I is applied when it is applied to a large-sized press machine or when it is necessary to further reduce the distance between the optical axes.
It is not enough to have only two C's, and it is necessary to add C in accordance with the number of optical axes. In addition, a flip-flop circuit is required to detect an abnormality only when the two optical axes are blocked. As a result, the number of parts is increased and the size of the device is increased. Also, the flip-flop circuit set
The operation is complicated due to the necessity of reset operation and generation of synchronization pulse.

Further, although the flip-flop circuit is reset by the first synchronizing pulse of the synchronizing pulse generator 6, it is not always output from the first synchronizing pulse s3 when the control is started. . For example, second
If the two optical axes are cut off immediately after the first sync pulse is output, an error occurs until the flip-flop circuit is reset by the first sync pulse s3 after the 1-cycle sync pulse generation operation. Is not detected.

As described above, if the number of parts is increased or a complicated operation is performed, it takes time to detect an abnormality, and it becomes impossible to sufficiently meet the demand for suddenly stopping the press machine in an emergency. Further, since the increase in the number of parts and the complicated control are likely to lead to the breakdown of the device, improvement is required from the viewpoint of improving the reliability of the device.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above problems and to provide a compact and highly reliable light beam safety device for a machine tool.

[0016]

SUMMARY OF THE INVENTION The present invention for solving the above problems and achieving the object is provided with a light receiving signal from a light receiving device corresponding to an optical axis, and at least two of the light receiving signals are supplied.
A first feature is that a majority decision gate IC is provided which outputs a majority decision signal as an abnormal signal when one is at the level when the optical axis is blocked.

Further, according to the present invention, the gate means for outputting a detection signal when at least one of the received light signals is at the level when the optical axis is blocked, and the majority gate IC.
A plurality of detection blocks including a plurality of detection blocks, and an upper majority decision gate IC that outputs a majority decision signal as an abnormal signal when at least two detection signals output from the gate means provided in each detection block are supplied. The second characteristic is the point.

[0018]

According to the first feature, when at least two optical axes are blocked, the majority decision gate IC outputs a majority decision signal as an abnormal signal. Therefore, the safety device can be operated by using this abnormal signal.

Further, the second feature makes it possible to detect that at least two of the more optical axes are blocked. That is, one optical axis block can be configured for each of the predetermined number of optical axes, and the detection block can be associated with the optical axis block. As a result, when there are many optical axes,
When the optical axes at positions distant from each other, that is, the optical axes of different optical axis blocks are interrupted one by one, the majority output signal of the upper majority gate IC is regarded as an abnormal signal,
The safety device can be activated.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram showing a main part of a light beam type safety device used for a machine tool such as the press machine shown in FIG.
In this example, unlike the configuration shown in FIG. 2 as a conventional device, each light receiving element forming the light receiving element rows 8 to 10 outputs a high level signal when receiving light, and when not receiving light, that is, the optical axis is blocked. It is sometimes assumed that the signal is set to output a low level signal.

In FIG. 1, the light receiving detector is composed of four detection blocks B1 to B4, and each detection block B1 to B4.
Corresponds to an optical axis block in which four optical axes are combined into one. Each of the detection blocks B1 to B4 includes a light receiving element array 8 to 1
1 and majority gate ICs 16 to 19 to which the output signals of the light receiving element arrays 8 to 11 are supplied, and an AND gate 20.
-23 are provided. Majority gate IC16-19
Outputs a low-level signal when the number of low-level signals is larger than the number of high-level signals among the plurality of signals supplied from the light receiving element array for each detection block. The output signals of the majority decision gate ICs 16 to 19 are supplied to the AND gate 24, and the output signal of the AND gate 24 is supplied to the AND gate 25. The output signal of the AND gate 25 is connected to a driving device (not shown) that stops the press machine. In this embodiment, the operation of the press machine is set to stop when the output signal of the AND gate 25 becomes low level.

The output signals of the AND gates 20 to 23 in the detection blocks B1 to B4 are supplied to another majority gate IC26, and the output signal of the majority gate IC26 is supplied to the AND gate 25. The majority gate IC 26 is a majority gate IC in the detection block.
For the sake of convenience, it is called a high-ranking majority gate IC for convenience.
In addition, one output signal (# 1 signal) of the light receiving element array 8
That is, the signal corresponding to the light transmission / light blocking of the uppermost optical axis is directly supplied to the AND gate 25.

The majority gate ICs 16 to 19 and 2
6 has 5 inputs, one of which is connected to ground. However, since the majority gate IC 16 is supplied with only three signals from the light-receiving element array 8, one more input is connected to the power supply and maintained at a high level.

In the above configuration, focusing on the detection block B1, when the optical axis corresponding to the # 1 signal in the output signal of the light receiving element array 8 is blocked and the light receiving element stops receiving light,
The # 1 signal changes to low level, and the output signal of the AND gate 25, which is supplied to the input side, changes to low level. When the output signal of the AND gate 25 changes to low level, an abnormality is detected, and the press machine is stopped based on the detection result.

At least 2 of the # 2 to # 4 signals
If the optical axis corresponding to one is cut off, the majority gate IC1
Since many of the six inputs are low, the output signal of the majority gate IC16 changes to low. That is, a majority decision signal is output. As a result, AND gate 24
The output signal of the AND gate 25 also changes to a low level and an abnormality is detected.

Further, when the optical axis corresponding to at least one of the # 2 to # 3 signals is cut off, the AND gate 20 is activated.
To the AND gate 20 and the output signal of the AND gate 20 also changes to the low level.

Other detection blocks B2, B3 and B4
Similarly, the majority gate ICs 17, 18, 19
When each of the output signals of 1 and 2 changes to the low level, the output signal of the AND gate 25 changes to the low level via the AND gate 24, and the abnormality is detected. Further, the light receiving element rows 9, 10, 1 of the detection blocks B2, B3 and B4
When at least one of the output signals of the light receiving elements of No. 1 changes to low level, the output signals of the AND gates 21, 22, and 23 change to low level.

Thus, when a large number, that is, two or more of the output signals of the AND gates 20 to 23 supplied as the input of the upper majority decision gate IC26 become low level, the output signal of the upper majority decision gate IC26 changes to the low level. To do. As a result, the output signal of the AND gate 25 also changes to a low level and an abnormality is detected.

As described above, according to the present embodiment, when two or more light receiving elements in each of the detection blocks B1 to B4 stop outputting light reception signals, and in each of the other detection blocks, one or more light reception signals are received. Abnormality can be detected in any case where the element stops outputting the light receiving signal.

In this embodiment, the output signal of the light receiving element array is changed to a low level when the optical axis is cut off. On the contrary, when the optical axis is cut off, Moreover, the output signal of the light receiving element array may be changed to a high level. In this case, it goes without saying that the logic of the gate circuit is modified according to the signal.

Further, by combining a plurality of majority gate ICs, it is possible to output an abnormal signal only when not only two optical axes but also three or more optical axes are blocked.

Further, the present invention is not limited to the safety device in which the light emitter and the light receiver are separately arranged on both sides of the machine tool,
A sensor in which a light emitter and a light receiver are integrated is arranged on one side of the machine tool, and the light from the light emitter is applied to a reflection mirror arranged opposite to this sensor, and the light reflected by the reflection mirror is detected. It can also be applied to safety devices. Further, it is needless to say that the present invention can be applied to machine tools other than press machines.

[0033]

As is apparent from the above description, according to the present invention, an abnormal signal is issued to stop a machine tool such as a press machine when a large number of optical axes are blocked in a light beam type safety device. In this case, the following effects can be achieved. (1) The number of gate circuits can be reduced, and a synchronizing pulse generator for supplying to the gate circuits is not required. (2) Since it is not necessary to determine whether or not a plurality of optical axes are blocked by the flip-flop circuit, a circuit for the reset / set operation of the flip-flop circuit is unnecessary. (3) The reset operation, which is a prerequisite for the abnormality determination, is not necessary, and it is possible to discriminate a large number of optical axis interruptions at any timing, and the machine tool can be stopped suddenly. (4) Since the same number of gate circuits, synchronization pulse generation circuits, and flip-flop circuits as the optical axis can be omitted, the number of parts can be reduced, the device can be downsized, and the failure rate can be reduced because the circuit configuration is simplified. It can be reduced. As a result, a highly reliable safety device can be provided.

[Brief description of drawings]

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

FIG. 2 is a circuit diagram showing a conventional technique.

FIG. 3 is a perspective view of a light beam type safety device.

[Explanation of symbols]

8 to 11 ... Light receiving element array, 16 to 19, 26 ... majority gate IC

Claims (2)

[Claims] 1. A protective area defined by a plurality of light rays is provided on at least a front surface of the machine tool, and the machine tool is stopped when a plurality of optical axes of the light rays are interrupted. In a light beam type safety device for a machine tool, a light projecting unit that emits the light beam, a light receiving unit that receives the light beam emitted from the light projecting unit, and a light receiving signal from the light receiving unit, and at least the light receiving signal. A light beam safety device for a machine tool, comprising: a majority gate IC that outputs a majority signal as an abnormal signal when two of the levels are when the optical axis is blocked. 2. A machine tool is provided with a protection area defined by a plurality of light rays on at least a front surface thereof, and the machine tool is stopped when a plurality of optical axes of the light rays are blocked. In a light beam type safety device for a machine tool, a light projecting unit that emits the light beam, a light receiving unit that receives the light beam emitted from the light projecting unit, and a light receiving signal from the light receiving unit, and at least the light receiving signal. A majority decision gate IC that outputs a majority decision signal as an abnormal signal when two are at the level when the optical axis is blocked, and a detection signal is output when at least one of the light receiving signals is at the level when the optical axis is blocked. A plurality of detection blocks including a gate means for operating the gate means, and an abnormal signal when at least two detection signals output from the gate means provided in each detection block are supplied. Top majority gate IC that outputs a majority signal as
A light beam type safety device for a machine tool, characterized in that