SURVEILLANCE DEVICE

Description

[0001] The invention relates to a monitoring device according to the preamble of claim 1.

[0002] Such monitoring devices are used in the field of safety technology, whereby the safety sensor is generally used to monitor the danger area of ​​a hazardous system, whereby the term system generally also includes machines, robots and the like.

[0003] In particular, the monitoring device is used to secure access to a danger zone of a plant, with access to the danger zone being via a conveyor system.

[0004] The monitoring device typically comprises a light curtain as a safety sensor, which monitors a protective field lying on a single plane. The light curtain generates a switching signal whose switching states indicate whether an object is present in the protective field or not. If the light curtain detects an object in the protective field, the corresponding switching signal triggers a safety function as an object detection signal. For example, the switching signal is used to control a system's control unit, which shuts it down so that no further hazards can arise from the system.

[0005] Permissible objects, such as palletized transport goods, are generally also fed into the system on the conveyor system and are required to perform the system's work processes. Since such permissible objects are not safety-critical, triggering the safety function when permissible objects move through the light curtain's protective field would result in an unnecessary machine downtime.

[0006] To prevent this, known monitoring systems use muting sensors upstream of the safety sensor in the conveying direction of the conveyor. If the muting sensors detect an object as a permissible object, the safety sensor is bypassed for a specified period of time, so that it no longer triggers the safety function when the permissible object passes through the protective field.

[0007] Such muting sensors are typically formed by light barrier arrangements. Such light barrier arrangements often cannot reliably detect permissible objects.

[0008] Another disadvantage of such monitoring devices is that the muting sensors arranged upstream of the safety sensor require a considerable amount of space.

[0009] Another disadvantage is that the coordination of the timing and the evaluation of the signals from the muting sensors is complex and prone to errors, since the time period that elapses until the permissible object has actually passed the safety sensor must be extrapolated from the times of the object detections by the muting sensors.

[0010] DE 10 2016 116 733 B3 relates to a signal processing unit and method for generating an output signal at an output terminal with a cable having at least two signal conductors, wherein a first sensor signal from a first sensor is applied to a first input terminal and a second sensor signal from a second sensor is applied to a second input terminal, wherein the input terminals are each connected to a cable, wherein a control and evaluation unit is arranged, wherein the control and evaluation unit generates a signal change in a first sensor signal from a first sensor upon an edge or signal change of a second sensor signal from a second sensor, wherein the signal change of the first sensor signal is maintained for a predetermined period of time, wherein the control and evaluation unit outputs the first changed sensor signal and the second sensor signal respectively on the signal conductors of the output terminal.

[0011] DE 10 2008 004 941 A1 relates to a safety arrangement for monitoring a passage through which only permissible objects are conveyed in at least one direction of movement, with a first optoelectronic sensor which has at least one light transmitter and at least one light receiver for monitoring a flat protective field arranged in the passage for passage through the object, with at least one control and evaluation unit through which a warning or control signal can be derived when an impermissible object passes through and with a muting sensor which is arranged in front of the passage in the direction of movement and is connected to the control and evaluation unit for the timely deactivation of the protective field when permissible objects pass through.In order to provide a device that ensures high reliability with less effort, it is proposed that means for determining and evaluating an object speed are present in the control and evaluation unit and that, depending on an object detection by the muting sensor and depending on the object speed, the warning or control signal can be suppressed for a calculated time and for a calculated duration, from the time the object enters the protective field until it leaves the protective field.

[0012] The invention is based on the object of providing a monitoring device of the type mentioned above, which has a high level of functionality while being structurally simple.

[0013] To achieve this object, the features of claim 1 are provided. Advantageous embodiments and expedient developments of the invention are described in the dependent claims.

[0014] The invention relates to a monitoring device with a safety sensor designed to monitor a protective field in such a way that an internal object detection signal is generated upon object intrusion detected in the protective field. Furthermore, at least one signal source generating an influence signal and a control and evaluation unit are provided, by means of which the internal object detection signal can be delayed such that it can be influenced depending on the influence signal. The influenced internal object detection signal can be output to the safety sensor as an external object detection signal.

[0015] The basic idea of ​​the invention is therefore to delay the internal object detection signal generated in the safety sensor relative to the influencing signal in such a way that the internal object detection signal can be influenced depending on the influencing signal in order to generate an external object detection signal that is dependent on the influencing signal and may be modified, which is then output via the safety sensor.

[0016] If the safety sensor detects an object in the protective field, an internal object detection signal is usually generated, which is also output in this form as an external object detection signal, triggering a safety function. For example, the safety function involves shutting down a system monitored by the safety sensor, i.e., shutting it down so that it no longer poses any danger.

[0017] According to the invention, the internal object detection signal can be influenced, in particular modified, using the influencing signals generated by the signal source(s), so that the output external object detection signal is different from the internal object detection signal. This allows the monitoring function of the safety sensor to be flexibly adapted to changing hazardous situations. A delay in the internal object detection signal is essential here, since the influencing signal from the internal object detection signals is then present, and thus the internal object detection signal can be modified depending on the influencing signal.

[0018] As a signal source for generating the influencing signal, for example, a controller can be provided which in particular controls a system component such as a conveyor unit that supplies transport goods to a system to be monitored.

[0019] It is particularly advantageous to use sensors to form the signal sources or all of them. In particular, the signal sources are optical sensors, ultrasonic sensors, or radar sensors.

[0020] The signal sources can be distance sensors, light barriers, reflective light barriers, light curtains or code readers.

[0021] To increase the safety of the monitoring system, it is advisable to provide means for testing the functionality of the or each signal source.

[0022] This enables error control of the signal sources.

[0023] For example, if the signal sources are designed as distance sensors, their signal values ​​can be used to perform a self-test of these sensors if no permissible object is detected.

[0024] According to a particularly advantageous embodiment of the invention, a muting function is implemented with the influencing signal, i.e. permissible objects are detected by means of the or all signal sources.

[0025] In this case, the signal sources are used to detect permissible objects that do not lead to a hazardous situation in a system monitored by the safety sensor, whereby the interference signal is generated when a permissible object is detected.

[0026] In the simplest case, a signal source, in particular a sensor, may be sufficient to generate the influence signal.

[0027] Preferably, several sensors can be provided as signal sources, whose signals are evaluated jointly, in particular to detect the geometry of a permissible object. Alternatively, permissible objects can be detected using identifiers, codes, and the like, in which case code readers can be used as sensors.

[0028] In general, it is crucial that the internal object detection signal is delayed relative to the interference signal so that it follows the interference signal in such a way that the detection of a permissible object is completed before the internal object detection signal is generated, so that the interference signal can influence the internal object detection signal.

[0029] For better timing of the signal sequences, the influencing signal can be delayed in the control and evaluation unit.

[0030] According to a particularly practical and simple design, a FIFO element is provided as a means for signal delay.

[0031] The muting function prevents unnecessary shutdown of a system monitored by a safety sensor when permissible objects, such as transport goods to be fed into the system, are conveyed through the protective field into the system's danger zone. The muting function ensures that if a permissible object is detected by the signal sources, i.e., the muting sensors of the monitoring device, the safety sensor is at least partially bypassed, i.e., muted, so that the transport goods can pass through the protective field without the safety sensor triggering the safety function.

[0032] With full muting, the entire safety sensor is bypassed. With partial muting, only the part of the protective field in which the permissible object is expected or detected is bypassed.

[0033] According to an advantageous embodiment of the invention, a protective field running in a plane is monitored by means of the safety sensor.

[0034] The safety sensor, an area distance sensor or a light curtain, is particularly advantageous.

[0035] The term "light curtain" also includes retro-reflective light curtains, light grids, and discrete arrangements of light barriers or retro-reflective light barriers. Generally, the light curtain forms a multi-beam system with beam axes formed by light beams that define the planar protective field. Area distance sensors are generally scanning distance sensors, which preferably use a pulse-time-of-flight or phase measurement method for distance measurements. Monitoring a planar protective field is achieved by deflecting the transmitted light beams emitted by the distance sensor's transmitter via a deflection unit that can rotate about a rotational axis. Alternatively, the distance sensor can be integrated into a rotating measuring head.

[0036] To provide a muting function, at least one muting sensor is advantageously provided as a signal source.

[0037] It is particularly advantageous if the or each muting sensor is arranged in the plane of the protective field.

[0038] The muting sensors therefore do not require a separate space for the installation of the monitoring device, but can be accommodated in the safety sensor itself, particularly in a space-saving manner.

[0039] According to a particularly simple embodiment, the muting sensor is formed by the safety sensor or by elements of the safety sensor.

[0040] In the event that the safety sensor is designed as a light curtain, individual or all beam axes of this light curtain can form a muting sensor.

[0041] According to an alternative embodiment, separate sensors are provided as muting sensors.

[0042] In this case, the or each muting sensor can be arranged in a housing of the safety sensor.

[0043] This means that the muting sensors do not require any additional space, meaning the monitoring device has a compact design.

[0044] Since the muting sensors are arranged on the same plane as the safety sensor, they generate signals simultaneously with the safety sensor. The inventive delay of the internal object detection signal generated in the safety sensor ensures that the influence signal is generated before the internal object detection signal, so that the influence signal can be used to influence the internal object detection signal and generate the external object detection signal to be output.

[0045] If the muting sensors do not detect a permissible object, no interference signal is generated, and the safety sensor's monitoring function remains activated. If the safety sensor then detects an object intrusion in the protective field and generates the internal object detection signal, this is also output as an external object detection signal, triggering the safety function—for example, shutting down the system monitored by the safety sensor—by outputting this external object detection signal to the system's control system.

[0046] However, if a permissible object is detected by the muting sensors, an interference signal is generated that activates the muting function. The safety sensor is muted in such a way that the interference signal bypasses the internal object detection signal when the safety sensor detects an object intrusion in the protective field. This means that, depending on the interference signal, an external object detection signal is generated from the internal object detection signal in such a way that no safety function is triggered.

[0047] The invention is explained below with reference to the drawings. They show: Figure 1: Example of a monitoring device according to the invention as access control to a hazardous area of ​​a facility. Figure 2: Individual view of the monitoring device according to Figure 1in a side view. Figure 3: Example of a detection of a transported item with the monitoring device according to Figure 1 . Figure 4: Alternative design of the monitoring device according to Figure 1. Figure 5: Schematic representation of a control and evaluation unit for the monitoring device according to Figure 1 Figure 6: Time courses of the control and evaluation unit according to Figure 5 evaluated and generated signals. Figure 7: Example of a conveying of a transported item for the monitoring device according to Figure 1 . Figure 8, 9: Examples of transport goods detection for the monitoring device according to Figure 1 .

[0048] Figure 1shows a schematic example of the monitoring device 1 according to the invention. In this case, the monitoring device 1 is used as access control for a hazardous area on a hazardous installation 2. Access to the hazardous area is via a conveyor device 3, whose conveyor belt is moved in the direction of movement marked F to convey transport goods 5 arranged on pallets 4 into the hazardous area. Of course, transport goods 5 can be guided out of the hazardous area in the same way. The conveyor device 3 and / or the hazardous area 2 can be protected by fencing attached to the sides.

[0049] The monitoring device 1 comprises a safety sensor 6 in the form of an optical sensor. This can be designed, for example, as an area distance sensor. In the present case, the safety sensor 6 is designed as a light curtain.

[0050] The light curtain comprises a series arrangement of transmitters 9 emitting light beams 8 in a first housing 7a and a series arrangement of receivers 10 in a second housing 7b. The light beams 8 span a planar protective field oriented in a vertical plane and thus perpendicular to the horizontal surface of the conveyor belt of the conveyor device 3.

[0051] The channels 9 ( Figure 2 ) are activated cyclically one after the other by means of a transmitter control (not shown). The receivers 10 ( Figure 2 ) are optically synchronized to the transmitters 9 in a known manner.

[0052] The received signals generated in the receivers 10 are evaluated in an evaluation unit (not shown) to generate an object detection signal in the form of a binary switching signal. The switching states of the switching signal indicate whether an object is located within the protective field or not. When the protective field is clear, the light beams 8 of all transmitters 9 strike the assigned receiver 10 unhindered. If an object enters the protective field, the light beams 8 of at least one transmitter 9 are interrupted by the object. To meet safety requirements, the evaluation unit has a redundant, preferably two-channel design.

[0053] If the safety sensor 6 registers an object intrusion in the protective field, the switching signal triggers a safety function, in particular the dangerous system 2 is shut down.

[0054] In order to avoid unnecessary shutdown of the system 2, the safety sensor 6 can be activated depending on muting signals from muting sensors 11 ( Figure 2 ), which generally form signal sources, are bridged when they are used to detect a permissible object such as, for example, a transport item 5 stored on a pallet 4 ( Figure 2 ). By bypassing the safety sensor 6, it does not trigger a safety function when the permissible object passes the protective field and the transported goods 5 can be fed to the system 2 without shutting it down.

[0055] In the embodiment according to Figure 2 Distance sensors arranged in the plane of the protective field are provided as muting sensors 11. In this case, the muting sensors 11 are integrated into the housings 7a, 7b of the light curtain, although this is not mandatory.

[0056] In principle, the distance sensors can be designed as ultrasonic sensors, radar sensors, or the like. In the present case, the distance sensors are optical sensors designed in the form of light sensors such that transmitted light beams 12 emitted by a distance sensor are reflected back to the distance sensor as received light beams from an object. The distance sensors can operate according to a pulse-time-of-flight method, a phase measurement method, or a triangulation method. As can be seen from Figure 2 As can be seen, the beam axes of the transmitted light beams 12 run perpendicular to the longitudinal axes of the housings 7a, 7b, i.e. in the same plane as the protective field.

[0057] The measured values ​​of the muting sensors 11 are fed to a control and evaluation unit 13 to generate muting signals, the structure of which is shown in Figure 5In principle, the evaluation unit of the light curtain can take over the function of the computer unit.

[0058] The permissible objects formed by the transport goods 5 are detected by means of the muting sensors 11.

[0059] An example of this shows Figure 3 As shown there, the muting sensors 11 arranged in the first housing 7a detect the complete left side contour of the transported goods 5 and also the side contour of the pallet 4. Similarly, the muting sensors 11 arranged in the second housing 7b detect the complete right side contour of the transported goods 5 and the pallet 4.

[0060] The muting sensors 11 designed as distance sensors detect the entire transported goods 5 with the complete pallet 4 during transport on the conveyor device 3.

[0061] As the Figure 8 and 9show, with the muting sensors 11, with a known distance W between the housings 7a, 7b of the safety sensor 6, a transport item 5 of width x can be determined independently of the offset of the transport item 5 to the center of the conveyor device 3, in which the distances a, b ( Figure 7 ) or a', b' ( Figure 8 ) of the left or right side contour of the transported goods 5 to the muting sensors 11.

[0062] Figure 4 shows an alternative embodiment of muting sensors 11 in the form of ultrasonic sensors 14, which have spatially separated ultrasonic transmitters 14 and ultrasonic receivers 15, so that the ultrasonic waves 16 determined by the respective ultrasonic transmitter 14 are guided obliquely onto the transported goods 5 and are reflected from there to the ultrasonic transmitter 14.

[0063] Alternatively, appropriate optical sensors or radar sensors can also be provided.

[0064] Figure 5 shows schematically the structure of the control and evaluation unit 13 of the monitoring device 1 according to Figure 1 The object detection signal generated in the safety sensor 6 is fed via a line 17 to a first delay element 18, which is preferably formed by a FIFO element. The internal object detection signal delayed in the delay element 18 is fed via a line 19 to a bypass logic 20.

[0065] The signals from the muting sensors 11 are fed to a detection unit 22 via a line 21. This unit detects whether a permissible object has been detected by the muting sensors 11.

[0066] The signals generated in the detection unit 22 are fed to a bridging unit 24 via an optional second delay element 23.

[0067] The output signals of the bridging unit 24 are fed to the bridging logic 20 via line 19 on the one hand and to the bridging logic 20 via an inverter 25 on the other hand.

[0068] The functioning of the control and evaluation unit 13 according to Figure 5 is based on the Figure 6a - 6d explained.

[0069] The signals from the muting sensors 11 are used in the detection unit 22 to detect whether a permissible object, in particular a transport item 5, is present or not. In order to reliably detect the transport item 5 even when it is transported at an angle on the conveyor unit, as Figure 7 shows, the muting sensors 11 are preferably activated only within limited time windows.

[0070] Figure 6ashows the internal object detection signal generated in safety sensor 6 in the form of a binary switching signal. As soon as an object is detected in the protective field by safety sensor 6, the switching state of the internal object detection signal changes from 0 to 1, as shown in Figure 6a visible.

[0071] Figure 6b shows the object detection signal delayed by the time interval Δt using the first delay element 18. The object detection signal acts in such a way that the Figure 6c The recording of the transported goods 5 in the recording unit 22 shown is completed.

[0072] In the detection unit 22, depending on the detection of the transported goods 5 with the muting sensors 11 ( Figure 6c ) as an influencing signal a muting signal ( Figure 6d ) is generated, the duration of which specifies the duration of the muting, i.e. the bridging of the safety sensor 6.

[0073] Muting duration is delayed by a defined time interval Δt by means of the second delay element 23, as Figure 6d shows.

[0074] When muting is activated, i.e. during the period in which the muting signal is Figure 6d is in switching state 1, the safety sensor 6 is bypassed by a logical AND operation of the muting signal with the internal object detection signal, generating an external object detection signal that is output to the safety sensor 6. This external object detection signal is present on the output line 26 of the bypass logic 20, which is no longer in switching state 1 (like the internal object detection signal) but in switching state 0.

[0075] If muting is not activated, the internal object detection signal is output as an external object detection signal, which triggers the safety function. List of reference symbols

[0076] (1)Monitoring device (2)System (3)Conveyor device (4)Pallet (5)Transported goods (6)Safety sensor (7)Housing (8)Light beam (9)Transmitter (10)Receiver (11)Muting sensor (12)Transmitted light beam (13)Control and evaluation unit (14)Ultrasonic sensor (15)Ultrasonic transmitter (16)Ultrasonic wave (17)Cable (18)Delay element (19)Cable (20)Bridging logic (21)Cable (22)Detection unit (23)Delay element (24)Bridging unit (25)Inverter (26)Output line (F)Direction of movement

Claims

1. A monitoring device (1) with a safety sensor (6), which is designed to monitor a protective field in such a way that an internal object detection signal is generated when an object is detected in the protective field, wherein at least one signal source generating an influencing signal is provided, characterised in that a control and evaluation unit (13) is provided, by means of which the internal object detection signal can be delayed in such a way that it can be influenced as a function of the influencing signal, and in that the influenced internal object detection signal can be output as an external object detection signal at the safety sensor (6).

2. A monitoring device (1) according to claim 1, characterised in that the influencing signal is a muting signal by means of which the internal object detection signal is bridged.

3. A monitoring device (1) according to one of claims 1 or 2, characterised in that a protective field extending in a plane is monitored by means of the safety sensor (6).

4. A monitoring device (1) according to one of claims 1-3, characterised in that the safety sensor (6) is an area distance sensor or a light curtain.

5. A monitoring device (1) according to one of claims 1-4, characterised in that at least one muting sensor (11) is provided as a signal source.

6. A monitoring device (1) according to claim 5, characterised in that the or each muting sensor (11) is arranged in the plane of the protective field.

7. A monitoring device (1) according to one of claims 5 or 6, characterised in that the muting sensor (11) is formed by the safety sensor (6) or by elements of the safety sensor (6).

8. A monitoring device (1) according to one of claims 5 or 6, characterised in that the or each muting sensor (11) is arranged in a housing (7a, 7b) of the safety sensor (6).

9. A monitoring device (1) according to one of claims 1 - 8, characterised in that the signal source is formed by an optical sensor, an ultrasonic sensor or a radar sensor.

10. A monitoring device (1) according to one of claims 1-9, characterised in that the signal source is formed by a distance sensor, a light barrier, a retro-reflective light barrier, a light curtain or a code reader.

11. A monitoring device (1) according to one of claims 1-10, characterised in that admissible objects are detected by means of the or all signal sources.

12. A monitoring device (1) according to claim 11, characterised in that an influence signal is generated when a permissible object is detected.

13. A monitoring device (1) according to one of claims 1-12, characterised in that the influencing signal can be delayed in the control and evaluation unit (13).

14. A monitoring device (1) according to one of claims 1 - 13, characterised in that a FIFO element is provided as a means for signal delay.

15. A monitoring device (1) according to one of claims 1-14, characterised in that means are provided for testing the function of said or each signal source.