JPH0769435B2 - Photoelectric switch - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a photoelectric switch mounted on a mechanical device for safety.

[Conventional technology]

A machine tool such as a press machine is obliged to install a safety device for stopping the machine when a human hand or the like enters the space where the blade or the like moves.

As such a safety device, as shown in FIG. 5, a light projecting unit (2) having a plurality of light projectors (1) and a light receiving unit (a plurality of light receivers (3) so as to sandwich a space to be detected ( There is known a photoelectric switch in which 4) is arranged to face each other.
This photoelectric switch (5) irradiates the light receiver (3) facing each other from the light projectors (1) in parallel with the beam light, and each light receiver (3) detects the presence or absence of light reception.

If even one light beam is blocked, the light receiving output of one of the light receivers (3) is turned off, so it is determined that there is an object, and a control signal for shutting off the power of the machine tool is output.

The photoelectric switch (5) operates so that the light projecting and receiving operations are performed only between the light projecting device (1) and the light receiving device (3) which face each other, and the light receiving device (3) is not operated by the light of the adjacent light projecting device (1). Need to be kept. This is because unless this is done, the light shield does not operate unless the light shield is large and a small object cannot be detected.

As a method for preventing the interference between the adjacent light emitting and receiving devices, a synchronization method in which the light emitting and receiving timing is different for each pair of the light emitting device (1) and the light receiving device (3), and the light emitting and receiving frequency for each pair. The frequency identification method that makes the difference is considered.

[Problems to be Solved by the Invention]

The above-mentioned synchronization method requires a cable for transmitting a synchronization signal to be wired between the light projecting unit (1) and the light receiving unit (3), and is not suitable for installation in a safety detection space of a machine tool having a restricted mounting location. .

Further, in the frequency identification method, the frequency needs to be different for each pair of the sender and the receiver. Therefore, when the safety detection space is wide and the number of the pairs of the sender and the receiver needs to be increased, the frequency type to be used is different. There is a problem that the number becomes very large, the difference between the frequencies becomes small, and a highly accurate identification circuit is required in the light receiver, which leads to an increase in cost.

Further, the conventional photoelectric switch (5) is the light projecting unit (2).
Since the light receiving unit (4) is divided into a light receiving unit (4) and a light receiving output can be obtained only in the light receiving unit (4), an operation indicator lamp (6) for visually checking whether light is being received is provided in the light receiving unit (4).
Only available in Therefore, there is a problem in that it is inconvenient to align the optical axis while looking at the operation indicator lamp (6) when the photoelectric switch (5) is attached. By the way, since the light emitted by the projector (1) is infrared light and cannot be seen,
It is necessary to confirm the light receiving state by the operation indicator lamp (6), and the optical axis alignment is performed by gradually moving the directions of the light projecting unit (2) and the light receiving unit (4). If the operation indicator (6) can be seen at hand when moving, the workability is greatly improved.

In view of the above-mentioned problems, the present invention distinguishes each light projection of a plurality of pairs of a light emitter and a light receiver, which are arranged to face each other with a detection space interposed therebetween, with a simpler structure than the conventional one, and at the same time, an operation indicator lamp is provided on both sides. The purpose is to be provided in.

[Means for Solving the Problems]

According to the present invention, a master device and a slave device of a photoelectric switch are arranged to face each other with a space for detecting the presence or absence of an object interposed therebetween, and the photoelectric switch is incorporated into the master device. When a start signal is received, light is projected for a predetermined identification time. 1 light projector, a first light receiver which is incorporated in the slave device with the same optical axis as the first light projector, and which outputs when receiving the light of the identification time, and in the slave device, the first light projector is the optical axis When the output of the first light receiver is different, the light is projected to the master device side for the above-mentioned identification time, and at the same time, the second light projector that prohibits the operation of the first light receiver during this period and the inside of the master device A second light receiver which is incorporated with the second light projector so that its optical axis coincides with the second light projector, starts operation after the first light projector has finished projecting light, and generates a light reception output when light is received and stops the operation. Light emitting / receiving unit By providing a plurality of units with different identification times of each unit across the master device and the slave device, and by giving the light reception output of the second light receiver of the preceding stage unit as the activation signal of the first projector of the next stage unit, The master device and the slave device are configured to perform multiple reciprocating light emitting / receiving operations, and at the beginning of a predetermined sequence time repeatedly generated in the master device, a start signal is sent to the first light emitter of the first light emitting / receiving unit. And a sequence timer for determining whether or not there is an object between the master device and the slave device, depending on whether or not the light reception output from the second light receiver of the light emitting and receiving unit at the final stage returns within this sequence time. An output circuit is provided which receives the object presence / absence signal output by the sequence timer judging at every predetermined sequence time and outputs it. Provide a photoelectric switch.

[Action]

In the above configuration, when the master device generates the activation signal at the beginning of the sequence time, the light emitting / receiving operation is performed between the master device and the slave device by making a plurality of reciprocations with different optical axes. If there is no object between the master device and the slave device, after the predetermined time, the second stage of the final stage of the light emitting and receiving unit
Received light output can be obtained at the light receiver. On the other hand, if there is an object and even one optical axis is blocked, this light reception output cannot be obtained even after a lapse of a predetermined time. The sequence timer determines the presence / absence of an object based on whether or not the received light output returns within the sequence time, and outputs it to the output circuit.

In the light projecting operation, each second light receiver in the master device starts the light receiving operation only after the first light projector of the same unit performs the light projecting operation, and stops the operation after receiving the light. In addition, each first light receiver in the slave device is connected to the second light receiver of the same unit.
The light receiving operation is prohibited while the projector is performing the light emitting operation. Further, the first light receiver generates a light reception output only when it receives light of the identification time determined to be different for each unit. Therefore, each light receiver generates a light reception output only when it receives light from the opposing light emitter, and does not malfunction due to direct light and reflected light or external light from other light emitters.
Interference is prevented.

〔Example〕

The present invention will be described with reference to an embodiment shown in FIG. 1 in which two light emitting / receiving units are provided.

The photoelectric switch (10) shown in the figure is configured by arranging a master device (11) and a slave device (12) so as to face each other with a space for confirming safety therebetween. The master device (11) and the slave device (12) are box-type devices having a light projecting window and a light receiving window formed on the front surface as shown in FIG.

In the master device (11) and the slave device (12), two units (U ₁ ) and (U ₂ ) are installed, each including a light emitting and receiving unit that performs one round trip of light emitting and receiving operation. That is, the first and second light projecting / receiving units (U ₁ ) (U ₂ ) respectively include a _first light projecting unit (13) and a second light projecting unit (13) incorporated in the master device (11).
It is composed of a light receiver (14), a first light receiver (15) and a second light projector (16) incorporated in the slave device (12). Each unit (U ₁ ) (U ₂ ) has a unique identification time (T ₁ )
Except for (T ₂ ), the same operation is performed. Further, the master device (11) has a sequence timer (17) for managing the light projecting / receiving operation that goes around each unit (U ₁ ) (U ₂ ) and an output circuit (18).

The first floodlight (13) is a floodlighting circuit (19) and an infrared emitting LED.
It is composed of a light projecting element (20), etc., a condenser lens (21),
The first light receiver (15) includes a condenser lens (22), a light receiving element (23) such as a phototransistor, a first light receiving circuit (24), and a first detection circuit (25).

The second light projector (16) is composed of a second light projecting circuit (26), a light projecting element (27) such as an infrared emitting LED, and a condenser lens (28), and the second light receiver (14) is a collector. Optical lens (29), light receiving element (30) such as phototransistor, second light receiving circuit (3
1) and the second detection circuit (32).

When the first light projector (13) receives the activation signal S, the identification time unique to the unit [the first light emitting and receiving unit (U ₁ ) is (T ₁ ),
The second projecting / receiving unit (U ₂ ) projects only (T ₂ )] to the opposing first photoreceiver (15), and after this projecting, the second photoreceiver (1
4) It outputs a synchronization signal M that makes it possible to receive light. The first light receiver (15) determines by the first detection circuit (25) whether or not the width of the incident light is the identification time width (T ₁ ) or (T ₂ ) peculiar to the unit. When receiving light, the output L is output to the second light projector (16). The second light emitter (16) receives the output of the first light receiver (15) and emits light toward the second light receiver (14) for an identification time (T ₁ ) or (T ₂ ) unique to the unit, At the same time, during this projection time, the first
An operation stop signal N is sent to the light receiving circuit (24) to prohibit the operation. When the second photodetector (14) receives the light having the width of the identification time (T ₁ ) or (T ₂ ) peculiar to the unit, the second photodetector (32) discriminates it to generate the light reception output O, After this, the operation is stopped. In addition, this second light receiver (1
4) is the identification time (T ₁ ) without the second detection circuit (32)
Alternatively, the configuration may be such that the determination based on (T ₂ ) is not performed. First
This is because the light receiving timing is determined by the synchronization signal M of the light projector (13).

In addition, the master device (11) and the slave device (12)
Operation indicator lamps (33) (34) for receiving and displaying the received light output of one of the light receivers (preferably one and the other light receiver)
Are provided respectively.

Next, the operation of the photoelectric switch (10) shown in FIG. 1 will be described step by step.

As shown in FIG. 3, the sequence timer (17) has a timer for generating an output which is periodically turned ON for each fixed sequence time (T ₀ ), and at the time of this rising, the first light emitting / receiving unit (U _The start signal S is sent to the first projector (13) of ₁ ).

The first light projector (13), which has received the activation signal S, projects light to the first light receiver (15) facing the first light projector (13) for the identification time (T ₁ ).
This light projection is performed by pulsed light emission as shown in FIG. When the pulse emission is completed, the first light projector (13) sends a synchronization signal M to the second light receiver (14) to start its operation.

When the first light receiver (15) receives this pulsed light, the first light receiver (15)
The time width is judged by the detection circuit (25). The output of the light receiving element (23) has a continuous waveform as shown in FIG. 4 because its response speed is slower than the pulse period. If this continuous waveform matches the identification time (T ₁ ),
The first light receiver (15) generates the output L and the second light projector (16)
To start the operation of.

As a result, the second light projector (16) projects pulsed light toward the second light receiver (14) for the identification time (T ₁ ). In addition,
At the time of this light projection, an operation stop signal N is sent to the first light receiver (15) to stop the light receiving operation of the first light receiver (15) during that time. This is to prevent malfunction due to reflected light.

The second light receiver (16) is in the operating state at this time, and when it receives the light having the width of the identification time (T ₁ ), it generates the light reception output O and stops its operation.

The light reception output of the second light receiver (14) is given to the first light projector (13) of the _second light emitter / receiver unit (U ₂ ) as a start signal S. The second light emitting / receiving unit (U ₂ ) also performs the same reciprocating light emitting / receiving operation as the _first light emitting / receiving unit (U ₁ ) at the timing shown in FIG. However, the identification time in the second light emitting / receiving unit (U ₂ ) is different (T ₂ ) from that in the first light emitting / receiving unit (U ₁ ), as shown in FIGS. 3 and 4.

If there is no object between the master device (11) and the slave device (12), a predetermined time elapses after the activation signal S is sent from the sequence timer (17), and then the second light projecting / receiving unit (U ₂ ) The light reception output O from the second light receiver (14) returns to the sequence timer (17).

If the light receiving output returns before the sequence time (T ₀ ) elapses, the sequence timer (17)
If there is no object, the output p is output, and if it does not return, the object output determination output q is output. That is, since the sequence timer (17) outputs the object presence / absence determination result p or q every time the sequence time (T ₀ ) elapses, the output circuit (18) including an RS flip-flop circuit, The result is stored and held until the next determination, and is output as the safety confirmation signal a.

This output a is used for safety measures, such as sounding an alarm to notify when there is an object and shutting off the power of the machine tool.

Further, since the operation indicator lamps (33) and (34) are turned on when the light receiving output (O) is generated, it is possible to align the optical axis by using this. Since the operation indicator lamps (33) and (34) are turned on by the light receiving outputs from the different light emitting and receiving axes, if they are positioned so that both light up, all the light emitting and receiving axes match.

In the above embodiment, the light emitting and receiving units are provided in two stages,
Although the case where four light emitting / receiving axes are set in parallel has been described, this light emitting / receiving unit can be provided in three or more stages, and the number of light emitting / receiving axes for safety confirmation can be arbitrarily increased.

〔The invention's effect〕

According to the present invention, the projection and reception of light between the master device and the slave device are made to reciprocate a plurality of times by alternately changing the light projecting directions, so that the identification time can be made common for one reciprocation. Therefore, it is sufficient to use only half of the number of light emitting / receiving axes that are set in parallel as the type of light emitting signals for preventing interference, and a circuit that generates light emitting signals of different types (different identification times are generated). Circuit) and its identification circuit can be simplified.

Further, since the light receiver is provided in both the master device and the slave device, the operation indicating lamp can be provided in both, and the optical axis adjustment when mounting the photoelectric switch becomes easy.

[Brief description of drawings]

1 to 4 are views showing an embodiment of the present invention.
FIG. 2 is a block diagram showing the structure of the photoelectric switch, FIG. 2 is a perspective view showing the appearance of the photoelectric switch, FIG. 3 is a timing chart for explaining the operation, and FIG. 4 is a light emitting pulse train and a light receiving element receiving it. It is a figure which shows the output of. FIG. 5 is a plan view showing a conventional photoelectric switch. (10) -Photoelectric switch, (11) -Master device, (12) -Slave device, (13) -First projector, (14) -Second light-receiver, (15) -First Receiver, (16) …… Second emitter, (17) …… Sequence timer, (18) …… Output circuit, (U ₁ ) …… First emitter / receiver unit, (U ₂ ) …… Second Emitter / receiver unit (T ₀ ) …… Sequence time, (T ₁ ) (T ₂ ) …… Identification time.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display area H04B 10/105 10/22

Claims (1)

[Claims] 1. A master device and a slave device of a photoelectric switch are arranged so as to face each other with a space for detecting the presence or absence of an object interposed therebetween. The photoelectric switch emits light for a predetermined identification time upon receipt of a start signal. The first light projector, a first light receiver which is incorporated in the slave device with the optical axes aligned with each other, and which outputs when the light of the identification time is received, and the first light projector in the slave device are When the axes are different from each other and the first light receiver outputs, the second light projector projects the light to the master device side for the identification time, and at the same time prohibits the operation of the first light receiver, and the master device. A second light receiver which is incorporated in the second light emitter so that the optical axis thereof coincides with the second light emitter, which starts the operation after the first light emitter has finished projecting light, and generates a light reception output when receiving light and stops the operation. Light emitting / receiving unit By providing a plurality of units with different identification times for each unit across the master device and the slave device, and by giving the light receiving output of the second light receiver of the preceding unit as the activation signal of the first projector of the next unit, , Configured to perform multiple round-trip light emitting / receiving operations between the master device and slave device, and at the beginning of a predetermined sequence time that is repeatedly generated in the master device, it is activated by the first light emitter of the first light emitting / receiving unit. A sequence timer that sends a signal and determines whether or not there is an object between the master device and the slave device depending on whether or not the light receiving output from the second light receiver of the light emitting and receiving unit at the final stage returns within this sequence time. And an output circuit for receiving and outputting an object presence / absence signal which the sequence timer judges and outputs at every predetermined sequence time. Photoelectric switch characterized by