JPH0556440B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a light beam safety device installed at locations where safety must be ensured in various machine tools and the like.

[Conventional technology]

Conventionally, for example, a dangerous area of a machine tool such as a press machine is surrounded by multiple optical axes at the front, and when one or more optical axes are blocked by a part of the worker's body, an emergency stop is triggered. A multi-beam safety device is used.

Conventionally, this type of optical safety device has a time division circuit on the light emitter side that has a light emitter and a light receiver, which causes the light emitter to emit light in sequence, and a time division circuit on the light receiver that sequentially outputs each light reception signal from the receiver. A dividing circuit, a quick-cutting circuit that successively cuts off the outputs of the light-receiving side time-sharing circuit so as not to interfere with each other, a time-division recovery circuit that sequentially returns the outputs of the quick-cutting circuit to the state before time-division, and this time-division recovery circuit. A safety device equipped with a capacitor memory that sequentially stores each output of
This method is proposed in Japanese Patent No. 58-19918. However, in the safety device with the above configuration, in addition to a time division circuit on the light receiving side that unifies each light reception signal from the light receiver and outputs it sequentially, a time division recovery circuit that returns the unified time division signals to the original state is provided. As a result, the circuit configuration becomes complicated, the manufacturing cost increases, and the reliability of the circuit decreases.Furthermore, since each detection signal is sequentially stored in a capacitor memory and then output, there is a certain amount of input/output error in the signal input/output. There was a problem that the detection of danger was delayed when the light was blocked.

It also includes a light emitter that generates a plurality of optical axes in a dangerous area and a plurality of light receivers that receive light from the light emitter, and determines the blocking state of the light beam from the light emitter based on a light reception signal from the light receiver. JP-A-59-140994 discloses an optical safety device that generates an alarm when even one of the optical axes of a plurality of optical systems is momentarily interrupted. However, this device has the disadvantage that it generates an instantaneous alarm even if a small obstacle such as an insect crosses the optical axis, causing machine tools such as presses to stop unnecessarily.

[Means for solving problems]

The present invention aims to solve the above-mentioned disadvantages of conventional safety devices, and its purpose is to:
It is equipped with a light emitter that generates a plurality of optical axes at a dangerous location, and a plurality of light receivers that receive light from the light emitter, and provides an alarm by determining the blocking state of the light beam from the light emitter based on a light reception signal from the light receiver. To provide a light beam safety device that can accurately detect light blocking by a person or the like without malfunctioning even if noise is mixed into the light beam passage area, and operates reliably and quickly. It is in.

In order to achieve the object of the invention as described above, the present invention includes a light projector that generates a plurality of optical axes in a dangerous area, and a plurality of light receivers that receive light from the projector, and the light beams from the projector. A light beam type safety device that determines a light shielding state of a light beam based on a light reception signal from the light receiver and issues an alarm;
a light reception control circuit that causes each light receiver to perform light reception scanning in synchronization with the light emitter side and outputs a light reception data signal for each system based on the light receiver signal output from each light receiver;
Means for detecting that one system of light reception data among the plurality of systems of light reception data outputted from the light reception control circuit is missing a predetermined number of consecutive times, and generating a danger detection signal based on the missing signal from the means. A light beam type safety device is provided, characterized in that it is equipped with a light shielding determination means.

〔Example〕

Hereinafter, an embodiment of the present invention will be described. In FIG. 1, numeral 3 is a light projector, and a plurality of light emitting diodes or the like are used to generate a plurality of optical axes at regular intervals in front of a dangerous area such as a press machine. Optical elements 3a to 3n
has been established. Reference numeral 1 denotes a light projection control circuit that sequentially drives each of the light projecting elements 3a to 3n, and sequentially outputs a light projection signal to each light projector 3 through an AND gate 2 at a constant time interval. The light projection control circuit 1 can be constituted by, for example, a shift register, and operates by inputting a clock signal from a sequence controller 10, which will be described later. Reference numeral 4 denotes a light receiver that receives the light projected from each light projecting element of the light projector 3, and includes a plurality of light receiving elements 4 each formed of, for example, a phototransistor.
a to 4n are provided. Reference numeral 6 denotes a light reception control circuit which inputs the light reception signals outputted from each light receiver 4 via the amplifier 5, switches each light reception signal at a timing synchronized with the light projection operation, and outputs the light reception signals as one system. That is, the light reception control circuit 6 operates to scan the output system of each light receiver 4 at a timing synchronized with the light projection operation of the light projector 3. Reference numeral 8 denotes a flip-flop connected to the output side of the light reception control circuit 6, which converts one system of light reception signals generated by scanning each light reception output in the light reception control circuit 6 into a light reception data signal of high level and low level, that is, a binary code. do. 9 is a temporary memory RAM (random access memory) that can be written and read, and a flip-flop 8
A received light data signal sent from the RAM 9 is inputted, and the received light data is sequentially written. Writing and reading of the received light data to and from the RAM 9 is controlled by a sequence controller 10. The sequence controller 10 has a built-in fixed memory ROM (read only memory) in which a control program is written in advance, and based on this control program, sequentially outputs a read signal, a write signal, and an address signal to the RAM 9 at a predetermined timing. , light shielding determination circuit 1
It outputs a control signal to the light emitting control circuit 1, the light receiving control circuit 6, etc., and controls the entire safety device. Light shielding determination circuit 11
inputs the received light data signal for several cycles read from RAM 9, and when all the specific signals (signals corresponding to the received light signal) in each cycle are missing, it determines that light is blocked and outputs the danger detection signal. The signal is configured to be output to, for example, an emergency stop circuit (not shown) via the gate 13. A clock oscillator 12 generates a clock pulse signal, and applies a clock pulse signal of a predetermined frequency to the sequence controller 10 and the light shielding determination circuit 11. 7
is a one-shot circuit that performs a retrigger operation (one-shot operation) and outputs one pulse when the pulse interval of the light-receiving signal outputted from the light-receiving control circuit 6 becomes longer than a predetermined time width. , and a function of detecting a failure in the light reception control circuit 6 and outputting a failure signal to the emergency stop circuit.

Next, the operation of the optical safety device having the above configuration will be explained.

For example, in the case of a safety device that uses four optical axes, a clock signal CS serving as a timing signal for light emission and reception is applied from the sequence controller 10 to the light emission control circuit 1 and the light reception control circuit 6.
The start signal SS of each scan is clock signal CS 4.
Output is synchronized for each hit. From the light projection control circuit 1, as shown in the dimming chart in Figure 2, 4
Light projection drive signals 2as to 2ds are sequentially applied to the four light projectors 3 via the AND gate 2, and the light projector 3 sequentially generates four optical axes. On the other hand, the receiver 4
Each of the light receiving elements 4a to 4d sequentially receives light from the light projector 3, and the signals output from the light receiver 4 are sent to the light reception control circuit 6 through the amplifier 5, respectively.
The light reception control circuit 6 switches the signals from each light receiver 4 at the timings shown in Ta to Td in FIG.
Output. The light reception signal 6s is sent to the flip-flop 8.
A light reception data signal, which is a high level signal when light is received and a low level signal when light is not received, is written into the RAM 9, for example, in three cycles (data obtained by three scans). Subsequently, the light reception data for three cycles is immediately read out from the RAM 9 and is sent to the light shielding determination circuit 11.
The light shielding determination circuit 11 determines whether or not there is a dangerous state based on the light shielding state during each cycle. In other words, if any of the four optical axes is blocked by a part of the worker, the light reception data at the specific number in each scanning cycle will all be low-level light blocking data in three cycles, so This is determined based on the light reception data in the middle, and when the light reception data of the specific number is at a low level for all three cycles, it is determined that there is a danger state, and a high level danger detection signal is sent to the AND gate 13.
It is output to an emergency stop circuit (not shown) via. However, as shown in the timing chart in Figure 2,
If one pulse in one cycle of the light reception signal 6s is missing due to noise or malfunction, the light shielding determination circuit 11 does not determine that light is shielded, and prevents unnecessary output of a danger detection signal due to noise, etc. . On the other hand, the one shot circuit 7 inputs the light reception signal 6s output from the light reception control circuit 6, and when one or more pulses of the light reception signal 6s are deleted and the pulse interval becomes a predetermined value or more, one shot operation is performed by retriggering. Then, a one shot signal 7s is output. Therefore, an AND condition is established using this one shot signal 7s and the danger detection signal from the light shielding determination circuit 11, and a signal is output from the AND gate 13 to an emergency stop circuit (not shown) or the like.

Furthermore, as shown in Fig. 2, by eliminating the last clock signal CS pulse of 3 scanning cycles,
It is also possible to stop the light projection at this point to create a light-shielding state on the light receiving side, and to intentionally generate the one shot signal 7s from the one shot circuit 7 to automatically check the operation of the light receiver 4 and the light reception control circuit 6.

〔Effect of the invention〕

As described above in detail, the present invention includes a light emitting control circuit that sequentially scans and drives each light emitter at a fixed time interval, and a light emitting control circuit that scans and drives each light receiver in synchronization with the light emitter side. A light reception control circuit outputs a light reception data signal for each system based on the output light reception signal, and among the plurality of systems of light reception data output from the light reception control circuit, the light reception data for each system is continuously transmitted a predetermined number of times. Since it is equipped with a means for detecting the omission, and a light shielding determination means for generating a danger detection signal based on the omission signal from the means,
The optical safety device does not malfunction even if an insect or the like temporarily blocks the light beam, and it only operates reliably when the light beam is interrupted by an intruder, such as a person, increasing the reliability of the optical safety device. It turns out.

[Brief explanation of the drawing]

The figures show an embodiment of the present invention, and FIG. 1 is a block diagram of a safety device, and FIG. 2 is a timing chart of each signal. 1...Light emission control circuit, 3...Light emitter, 4...Light receiver,
6... Light reception control circuit, 9... RAM, 10... Sequence controller, 11... Light shielding determination circuit.

Claims (1)

[Claims] 1.Equipped with a light projector that generates a plurality of optical axes in a dangerous area and a plurality of light receivers that receive light from the light projector, and issues an alarm by determining the blocking state of the light beam from the projector using a light reception signal from the light receiver. In the optical safety device that generates light, there is a light emitting control circuit that sequentially scans and drives each light emitter at a fixed time interval, and a light emitting control circuit that scans each light receiver in synchronization with the light emitter side and outputs from each light receiver. A light reception control circuit that outputs a light reception data signal for each system based on a light reception signal is configured such that among the plurality of systems of light reception data output from the light reception control circuit, the light reception data for each system is missing a predetermined number of consecutive times. What is claimed is: 1. A light beam type safety device comprising: means for detecting a signal, and a light shielding determining means for generating a danger detection signal based on a missing signal from the means.