SURVEILLANCE DEVICE

Description

[0001] The invention relates to a monitoring device

[0002] Such a monitoring device includes a security sensor that detects objects within a protected field.

[0003] Such monitoring devices are commonly used in the field of security technology, particularly in the area of ​​personal protection. Typically, the security sensor is used to monitor access to a hazardous area within a facility.

[0004] A safety sensor in the form of a light curtain, used for such monitoring tasks, is known from DE 299 20 715 U1. The light curtain comprises a multiple arrangement of light barriers. If an object or person is detected by this light curtain, an object signal is generated within the light curtain, which leads to the shutdown of a machine or system. The light curtain thus fulfills its safety function, as it detects when a person enters the danger zone, which would endanger the person if the machine or system remained switched on. However, the ingress of a workpiece being processed by the machine or system into the danger zone would also trigger an object signal in the light curtain, which would then result in the machine being switched off.Since the workpiece being processed is not a safety-critical object, shutting down the machine or system upon its detection within the danger zone is unnecessary and therefore undesirable.

[0005] To prevent such unnecessary shutdowns of the machine or system, the light curtain described in DE 299 20 715 U1 incorporates muting sensors in addition to the light barrier arrangement at the entrance and exit of the danger zone. These sensors differentiate between persons or generally safety-critical objects and permissible objects, which are considered non-safety-critical. If a permissible object is detected, the muting sensors generate a muting signal, i.e., a bridging signal that temporarily deactivates the shutdown function, meaning the machine or system is not shut down, even if the light barriers of the light curtain are interrupted. Conversely, if one of the light barriers is interrupted and the muting sensors do not generate a bridging signal, the monitored machine or system is shut down.

[0006] From DE 10 2009 048 111 B4, a safety sensor is known that serves for monitoring the hazardous area of ​​a machine or system. It comprises a sensor unit with at least one light-emitting transmitter and one light-receiving receiver for monitoring a protective field, as well as an evaluation unit in which, upon detection of an object in the protective field, a shutdown command for the machine or system is generated as a safety function. Simultaneous monitoring of object presence signals, generated in two independent signal sources, is performed by means of an external or internal bridging unit. One of the signal sources is integrated into the safety sensor itself.The bypass unit generates a safe bypass signal that overrides the safety sensor's safety function only if an object presence signal is registered by each of the signal sources within a time interval defined by the requirements of the relevant safety standards. The safety sensor is switched to a safe locking state by the bypass unit if, after the first object presence signal is registered within the time interval, the second object presence signal is not registered by the bypass unit.

[0007] EP 1 329 662 A2 relates to a safety curtain that triggers a safety function when an object enters its monitored area. To prevent non-safety-critical objects from triggering the safety function when passing through the monitored area, a muting function is provided. This muting function monitors whether a muting light curtain upstream of the safety light curtain generates object signals within a predefined time interval. If so, the safety light curtain is muted.

[0008] EP 2 306 063 A2 relates to a safety sensor used for monitoring the hazardous area of ​​a machine or system. The safety sensor comprises a sensor unit with at least one light-emitting transmitter and one light-receiving receiver for monitoring a protective field, as well as an evaluation unit. When an object is detected within the protective field, the evaluation unit generates a shutdown command for the machine or system as a safety function. An external or internal bypass unit overrides the safety function of the safety sensor if an object presence signal is registered by each of two independent signal sources within a specific time interval. One of the signal sources is integrated into the safety sensor itself.

[0009] DE 10 2007 040 692 A1 relates to an optoelectronic protective device comprising a safety sensor integrated in at least one housing for monitoring a hazardous area, and a sensor arm in which at least one muting sensor is integrated. A muting signal can be generated by the muting sensors, which can be used to silence the safety sensor. The sensor arm is coupled to the housing via a bracket in such a way that the sensor arm can be selectively positioned in either a transport position or a working position relative to the housing.

[0010] DE 201 03 828 U1 relates to a safety device for monitoring a passage through which objects move in one direction, comprising a first light barrier arrangement securing the passage which activates safety means when triggered, a second light barrier arrangement arranged in the direction of movement of the objects in front of the passage which deactivates the first light barrier arrangement and / or the safety means when triggered, and a timer device which maintains this deactivation for a predefinable time after an object has passed through the second light barrier arrangement.

[0011] The invention is based on the objective of providing a monitoring device with extended functionality.

[0012] 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.

[0013] The invention comprises a monitoring device with a safety sensor by means of which objects within a protective field can be detected. In normal operation, the safety sensor triggers a safety function when it registers an object entering the protective field. A bridging unit and detection means are provided, by means of which an object moving towards the safety sensor can be detected successively at at least two detection points. At least one area of ​​the protective field of the safety sensor is bridged by the bridging unit only if an object entering the protective field is registered at the detection points within a predetermined time interval. If an object entering the protective field occurs within the bridged area, the safety sensor does not trigger a safety function.The bridging unit puts the safety sensor into a secure locked state if, after an object intervention at a first detection point, no object intervention is registered at the second detection point within the specified time interval.

[0014] The monitoring device according to the invention is suitable for use in safety-related applications.

[0015] In particular, the protective field is used to monitor access to a hazardous area of ​​a facility.

[0016] Generally, a safety sensor performs a monitoring function such that, during normal operation, it triggers a safety function if it detects an object intrusion within the protected area. A key advantage of this safety function is that it shuts down a system monitored by safety sensors.

[0017] The term "plant" generally also includes machinery or other work equipment.

[0018] To avoid unnecessary plant downtime, the monitoring device according to the invention has a bridging unit with which a gating function, i.e. a bridging function, is implemented.

[0019] The gating function temporarily bridges at least a portion of the protective field, allowing objects to pass through without the safety sensor triggering the safety function and thus shutting down the system.

[0020] This can be used to feed non-hazardous objects, such as transported goods, through the protective field of the system's safety sensor without the system being shut down by the safety sensor.

[0021] According to the invention, the gating function is implemented with a bridging unit, wherein the bridging unit evaluates signals from detection means that detect objects moving towards the safety sensor at at least two detection points. The detection points are advantageously arranged one behind the other in the direction of movement of objects moving towards the safety sensor. Generally, the detection points are selected such that an object moving towards the safety sensor is detected sequentially by the detection means at the detection points.

[0022] According to the invention, the bridging unit performs simultaneity monitoring such that a gating function, in the form of bridging at least one area of ​​the safety sensor's protective field, is only triggered if an object intrusion is registered at both detection points within a predetermined time interval. The same applies analogously if more than two detection points are provided.

[0023] The distance between the detection points and to the safety sensor, as well as the size of the time interval, are chosen so that the gating function is only triggered when a non-hazardous object, such as a transported item, passes the detection point.

[0024] The detection device advantageously distinguishes permissible objects from impermissible objects; that is, object classification is possible based on the signals from the detection device. Permissible objects are non-hazardous objects, such as transported goods. Impermissible objects can include, in particular, people.

[0025] According to a first embodiment of the invention, sensor means are provided as detection means by which object interventions at both detection points can be detected.

[0026] In the simplest case, a single sensor is sufficient to detect objects at both detection points.

[0027] In this variant, the second detection point assigned to the safety sensor is advantageously located at a distance from the safety sensor that is less than a predefined minimum distance. This ensures that the object passing the safety sensor is the same object that was previously detected by the sensor elements at both detection points.

[0028] According to a second embodiment of the invention, a sensor means is provided as a first detection means by means of which object interferences at a first detection point can be detected. The safety sensor forms a second detection means by means of which object interferences at a second detection point, namely the location of the safety sensor, can be detected.

[0029] In this case, the second detection point coincides with the position of the safety sensor. This means that the detection of a permissible object occurs directly along with its placement within the protected area.

[0030] According to the invention, the bridging unit transfers the safety sensor into a secure locking state if, after an object intervention at a first detection point, no object intervention is registered at the second detection point within the specified time interval.

[0031] The transition of the safety sensor into the safe locking state immediately brings a system monitored by the safety sensor into a safe state, preferably shutting it down.

[0032] This distinguishes the monitoring device according to the invention from systems that operate with muting sensors. If no valid muting condition is detected by the muting sensors, the safety sensor continues to operate in its normal state. Only when the safety sensor registers an object intrusion within its protective field is the system shut down.

[0033] The detection means differ from known muting sensors such as light barriers or signal sources such as those known from DE 10 2009 048 111 B4.

[0034] According to one initial proposal, the sensor means could be formed by a radar system.

[0035] According to a second variant, the sensor means can be formed by an arrangement of induction loops.

[0036] According to a third variant, the sensor means are formed by the position sensors of a vehicle.

[0037] The vehicle can, for example, be an AGV (Automated Guided Vehicle), where a navigation system can be used as a detection device.

[0038] Advantageously, the sensor devices do not generate error-free signals.

[0039] This means that the sensor devices do not need to have a fail-safe design.

[0040] The fault tolerance of the monitoring device required for use in the field of safety technology is achieved, on the one hand, by the fact that the safety sensor has a fault-tolerant design.

[0041] It is advantageous that the fail-safe design of the safety sensor is realized through a redundant evaluation unit.

[0042] On the other hand, the fail-safe operation of the monitoring device is achieved by the fact that the bridging unit has a fail-safe design.

[0043] This can be achieved in particular by having the bridging unit be formed by the evaluation unit of the safety sensor.

[0044] The fail-safe bridging unit and the simultaneous monitoring of the signals from the recording devices, which are generated during the monitoring of the recording point, ensure the necessary fail-safety of the monitoring device.

[0045] According to an advantageous embodiment, the safety sensor is a light curtain, an area distance sensor, or a camera sensor.

[0046] The safety sensor thus monitors a protective field that covers an area or space.

[0047] In general, it is possible to bridge not just a part of the protected area, but the entire protected area with the monitoring unit.

[0048] Furthermore, it is possible to bridge several sub-areas of the safety sensor's protective field using the bridging unit.

[0049] This allows multiple permissible objects to pass through the safety sensor's protective field simultaneously within the various bridged sections without triggering a safety function. For example, with a safety sensor in the form of an area distance sensor or camera sensor, adjacent sections of the protective field can be bridged, enabling multiple permissible objects arranged side-by-side on a conveyor belt or similar to pass the safety sensor without triggering a safety function.

[0050] According to an advantageous embodiment, the bypassing of the safety sensor is maintained for a predetermined period of time.

[0051] This duration is adjusted to the speed of a permissible object so that the bridging is maintained for the time it takes the permissible object to pass the safety sensor.

[0052] Furthermore, the bridging can be advantageously terminated if no object is detected in the protective field by the safety switch.

[0053] The bridging is then terminated immediately after the permitted object has passed the safety sensor.

[0054] The invention is explained below with reference to the drawings. They show: Figure 1: Exemplary embodiment of a security sensor in the form of a light curtain. Figure 2: Exemplary embodiment of a security sensor in the form of an area distance sensor. Figure 3: Exemplary embodiment of a security sensor in the form of a camera sensor. Figure 4: First embodiment of the monitoring device according to the invention. Figure 5: Second embodiment of the monitoring device according to the invention. Figure 6: Third embodiment of the monitoring device according to the invention.

[0055] Figure 1 Figure 1 shows a first embodiment of a safety sensor in the form of a light curtain 1, by means of which a planar protective field 2 is monitored.

[0056] The light curtain 1 comprises an arrangement of light beams 3 emitted by transmitters 4, which are cyclically activated individually in succession by a control unit (not shown). The transmitters 4 and the control unit are integrated in a transmitter unit 5 with a first housing. The light curtain 1 further comprises an arrangement of receivers 6 for receiving the light beams 3. The receivers 6 are integrated in a receiver unit 7 with a second housing. The transmitters 4 are controlled by a transmitter controller 8. An evaluation unit 9 is assigned to the receivers 6 for controlling the receiver operation and for evaluating the received signals present at the outputs of the receivers 6. To meet the requirements for the use of the light curtain 1 in the field of safety technology, the evaluation unit 9 has a redundant design. Preferably, the evaluation unit 9 consists of two computer units that cyclically monitor each other.A protective field 2, formed by the area between the two housings, is monitored by the light curtain 1. Each transmitter 4 is assigned a receiver 6, so that when the protective field 2 is clear, the light rays 3 emitted by the transmitter 4 reach the receiver 6. Each transmitter 4 and its assigned receiver 6 define a beam axis of the light curtain 1, the direction of which is determined by the light rays 3 of the respective transmitter 4. If an object enters the protective field 2, the beam path of the light rays 3 from at least one transmitter 4, i.e., at least one beam axis, is interrupted.

[0057] In the evaluation unit 9, a fail-safe switching signal is generated based on the signals from the sensor unit. The switching states of this signal indicate whether an object is located within the protective field 2 or not. The switching signal is output via a safety switching output 10, which is advantageously designed with multiple channels.

[0058] When protective field 2 is clear, the safety switching output 10 is switched on according to the current switching state of the switching signal. If an object enters protective field 2, the safety switching output 10 is switched off.

[0059] Figure 2Figure 1 shows an embodiment of a safety sensor in the form of an area distance sensor. The area distance sensor has a distance sensor operating according to a pulse-time-of-flight method with a transmitting element 12 emitting light beams 11 and a receiving element 14 receiving light beams 13, wherein the distance to the target object 15 is determined from the time of flight of light to the target object 15 and back to the area distance sensor.

[0060] The transmitting element 12 and the receiving element 14 are mounted in a measuring head 16 by means of a holder. The outer surface of the measuring head 16 forms an exit window for the transmitting light beams 11 and the receiving light beams 13. The measuring head 16 is rotatably mounted on a base 17. By means of a drive mechanism (not shown), the measuring head 16 is set into a rotational movement about a rotational axis D, whereby the transmitting light beams 11 periodically sweep over a planar protective field 2.

[0061] Alternatively, the area distance sensor can be designed such that the transmitting element 12 and the receiving element 14 are arranged stationary in a housing. The transmitted light beams 11 are then periodically deflected by a motor-driven deflection unit.

[0062] Figure 3 Figure 1 shows an embodiment of a security sensor in the form of a camera sensor, comprising an image sensor 18 and an illumination unit 19. The image sensor 18 can have a linear or matrix arrangement of pixels. For example, the image sensor 18 can be formed from a CCD or CMOS array.

[0063] According to the embodiment according to Figure 1 The safety sensors also indicate, according to the Figures 2 and 3 an evaluation unit 9 and a safety switching output 10.

[0064] Figure 4Figure 1 shows a first embodiment of the monitoring device 20 according to the invention with a safety sensor in the form of a light curtain 1. Instead of the light curtain 1, an area distance sensor or camera sensor can also be used. This also applies to the embodiments shown in Figures 5 and 6.

[0065] The light curtain 1 monitors access to a danger zone 21 of a system 22. The system 22 is controlled by a system controller 23. The safety switching output 10 of the light curtain 1 is connected to the system controller 23.

[0066] In normal operation, light curtain 1 monitors the entire protective field 2. If protective field 2 is clear, light curtain 1 generates a corresponding switching signal, which activates the safety switching output 10, thus enabling the operation of system 22. If an object enters protective field 2, light curtain 1 generates a switching signal, which deactivates the safety switching output 10. This triggers a safety function that shuts down system 22.

[0067] In order to allow non-hazardous, permissible objects to pass through the protective field 2 of the system 22 without the light curtain 1 triggering a safety function and shutting down the system 22, a bridging unit 24 is provided, by means of which the protective field 2 of the light curtain 1 is temporarily at least partially bridged.

[0068] The bridging unit 24 forms a fail-safe unit, preferably comprising two mutually monitoring computer units. In this case, the bridging unit 24 forms a separate unit. Alternatively, the bridging unit 24 can be integrated into the evaluation unit 9 of the light curtain 1.

[0069] How Figure 4 As shown, a transport item 25 is moved as a permissible object on a conveyor line 26 in a transport device T in the direction of the safety sensor in order to supply the transport item 25 to the system 22.

[0070] On conveyor line 26, induction loops 28a and 28b are provided at two detection points 27a and 27b, extending across the entire width of the conveyor line 26. The detection points 27a and 27b with the induction loops 28a and 28b are arranged one behind the other in the transport direction T.

[0071] The induction loops 28a and 28b are non-fail-safe sensors for detecting the transported goods 25 and are connected to the bridging unit 24. To reliably distinguish the transported goods 25 from unauthorized objects, such as persons, the distances between the first detection point 27a and the second detection point 27b, and to the light curtain 1, are adjusted accordingly. Furthermore, the induction loops 28a and 28b only detect metallic objects, such as the surface beneath the transported goods 25. This also enables differentiation between authorized and unauthorized objects.

[0072] In the bridging unit 24, the transported goods 25 approaching the safety sensor are detected by the fact that first the first induction loop 28a registers an object intervention by the transported goods 25 and then, within a time interval specified in the bridging unit 24, which is e.g. 4 sec, the second induction loop 28b also registers an object intervention.

[0073] If this condition is met, at least a portion of the protective field 2 of the light curtain 1 is bridged by a command from the bridging unit 24, so that any object interference occurring there does not trigger the safety function. The bridged portion is adapted to the dimensions of the transported item 25, so that the transported item 25 can pass through the protective field 2 without triggering the safety function.

[0074] Advantageously, the bypassing of the safety sensor is maintained for a predetermined period of time.

[0075] The duration is adapted to the duration that the transported item 25 needs to pass through the protective field 2.

[0076] According to an advantageous further development, the bridging is terminated when no object is detected in protective field 2 by the safety switch.

[0077] Advantageously, the bridging unit 24 transfers the safety sensor into a secure locking state if, after an object intervention at a first detection point 27a, no object intervention is registered at the second detection point 27b within the specified time interval.

[0078] The secure locking state is achieved by switching off the safety switching output 10 of the light curtain 1, which immediately shuts down the system 22.

[0079] The design of the Figure 4The system can be modified such that only one induction loop 28b is provided as a sensor. In this case, the light curtain 1, in addition to the induction loop 28b, forms a further detection means by means of which a transported item 25, or more generally a permissible object, is considered detected if first an object intervention is registered in the induction loop 28b and subsequently, within the specified time interval, an object intervention is registered by the light curtain 1. Only if this condition is met is the light curtain 1 bypassed.

[0080] If, after object detection with the induction loop 28b, no object interference is registered with the light curtain 1 within the specified time interval, the light curtain 1 is switched to the safe locking state.

[0081] Figure 5 shows a variant of the embodiment according to Figure 4. Instead of induction loops 28a, 28b, a radar system 29 is arranged above the conveyor line 26 as a sensor means, with which objects within a detection area 30 are detected.

[0082] Within the detection area 30, two detection points 27a, 27b are defined, at which object interventions are registered.

[0083] Instead of two recording points 27a, 27b, only one recording point 27b may also be provided, in which case the embodiment is analogous to that shown in the above. Figure 4 In addition to the radar system 29 as a sensor and first detection means, the light curtain 1 is used as a second detection means.

[0084] The functioning of the monitoring device 20 according to Figure 5 corresponds to the functioning of the monitoring device 20 according to Figure 4 .

[0085] Figure 6Figure 1 shows a further embodiment of the monitoring device 20 according to the invention. In this case, an automated guided vehicle (AGV) 31 transports goods 25 through the protective field 2 to the system 22. The AGV 31 incorporates a navigation system 32 that generates position signals. Based on these position signals, the bridging unit 24 can trigger the bridging of the light curtain 1, the operation of which corresponds to the embodiments of the Figures 4 and 5 corresponds. List of reference symbols

[0086] (1) Light curtain (2) Protective field (3) Light beam (4) Transmitter (5) Transmitter unit (6) Receiver (7) Receiver unit (8) Transmitter control (9) Evaluation unit (10) Safety switching output (11) Transmitting light beam (12) Transmitting element (13) Receiving light beam (14) Receiving element (15) Target object (16) Measuring head (17) Base (18) Image sensor (19) Lighting unit (20) Monitoring device (21) Danger zone (22) System (23) System control (24) Bridging unit (25) Transported goods (26) Conveyor track (27a, b) Detection point (28a, b) Induction loop (29) Radar system (30) Detection area (31) Driverless transport system (32) Navigation system (D) Axis of rotation (T) Direction of transport

Claims

1. A monitoring device (20) with a safety sensor, by means of which objects can be detected within a protective field (2), wherein the safety sensor triggers a safety function in normal operation when it registers an object intrusion in the protective field (2), wherein a bridging unit (24) and detection means, by means of which an object moving towards the safety sensor can be detected successively at at least two detection points (27a, 27b), are present, and wherein at least one region of the protective field (2) is provided, by means of which an object moving towards the safety sensor can be detected successively at at least two detection points (27a, 27b), and wherein at least one region of the protective field (2) of the safety sensor is bridged by the bridging unit (24) only if the object is detected within a predetermined time interval, if an object intrusion is registered at the detection points (27a, 27b) within a predetermined time interval, the safety sensor not triggering a safety function in the event of an object intrusion in the bridged area of the protective field (2), characterised in that the bridging unit (24) transfers the safety sensor into a safe locking state if, after an object intrusion at a first detection point (27a), no object intrusion is registered at the second detection point (27b) within the predetermined time interval.

2. A monitoring device (20) according to claim 1, characterised in that sensor means are provided as detection means, by means of which object interventions can be detected at both detection points (27a, 27b), or in that sensor means are provided as first detection means, by means of which object interventions can be detected at a first detection point (27a), and in that the safety sensor forms a second detection means, by means of which object interventions can be detected at a second detection point (27b).

3. A monitoring device (20) according to claim 2, characterised in that the sensor means are formed by a radar system (29) or by an arrangement of induction loops (28a, 28b) or by position sensors of a vehicle.

4. A monitoring device (20) according to one of claims 2 or 3, characterised in that the sensor means do not generate fail-safe signals.

5. A monitoring device (20) according to one of claims 1 to 4, characterised in that the safety sensor has a fail-safe design.

6. A monitoring device (20) according to claim 5, characterised in that the fail-safe design of the safety sensor is implemented by a redundant evaluation unit (9).

7. A monitoring device (20) according to one of claims 1 to 6, characterised in that the safety sensor is a light curtain (1), an area distance sensor or a camera sensor.

8. A monitoring device (20) according to one of claims 1 to 7, characterised in that the bridging unit (24) has a fail-safe structure.

9. A monitoring device (20) according to one of claims 6 and 8, characterised in that the bridging unit (24) is formed by the evaluation unit (9) of the safety sensor.

10. A monitoring device (20) according to one of claims 1 to 9, characterised in that the entire protective field (2) of the safety sensor is bypassed with the bypass unit (24), or in that several partial areas of the protective field (2) of the safety sensor are bypassed with the bypass unit (24).

11. A monitoring device (20) according to one of claims 1 to 10, characterised in that the bridging of the safety sensor is maintained for a predetermined period of time.

12. A monitoring device (20) according to claim 11, characterised in that the bridging is terminated if no object is detected in the protective field (2) by the safety switch.

13. A monitoring device (20) according to one of claims 1 to 12, characterised in that the protective field (2) is used to monitor access to a danger zone (21) of an installation (22).

14. A monitoring device (20) according to claim 13, characterised in that permissible objects are guided along a conveying path (26) through the protective field (2) of the safety sensor into the danger zone (21), permissible objects being distinguished from impermissible objects by means of the detection means.