Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
  • H01H47/00—Circuit arrangements not adapted to a particular application of the relay and designed to obtain desired operating characteristics or to provide energising current
  • H01H47/002—Monitoring or fail-safe circuits
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
  • H01H47/00—Circuit arrangements not adapted to a particular application of the relay and designed to obtain desired operating characteristics or to provide energising current
  • H01H47/002—Monitoring or fail-safe circuits
  • H01H47/004—Monitoring or fail-safe circuits using plural redundant serial connected relay operated contacts in controlled circuit

Definitions

• the present invention relates to a signaling device (other name: sensor, signal transmitter) for a safety circuit, with an input part for receiving an external state variable, with at least one switching element with an input and an output, and with a control part, which is designed for this purpose to control the at least one switching element from the external state variable such that one at the input applied signal to the output is switched through, i.e. appears at the output.
• a signaling device other name: sensor, signal transmitter
• the invention further relates to a safety circuit for safely switching off a dangerous system, with a safety controller that is designed to switch off the system fail-safe, and with a first and at least a second signaling device of the aforementioned type, which are connected in series to one another to the safety controller ,
• An operating control system receives setpoints and process variables of the system and uses them to generate control signals, which actuate the actuators of the system, using a predetermined control program.
• safety aspects ie the avoidance of dangers for people who are in the area of the system, are becoming increasingly important.
• systems that perform automated movements are now generally shielded by protective fences, light barriers, step mats and the like.
• emergency stop buttons when the system (or at least part of it) is to be switched off or otherwise brought into a safe state when actuated.
• safety-related signaling devices which therefore only generate status signals relevant for the protection of the system. conditions and make available, are generally not evaluated with the "normal" operational control of the system, but fed to a so-called safety controller or, in simpler cases, to a so-called safety switching device.
• safety control encompasses both simpler safety switching devices, such as those offered by the present applicant under the name PNOZ ® , and complex safety controls, such as the PLC-based PSS® from the applicant.
• safety controls differ from "normal” operational controls in that they are designed to be inherently fail-safe through measures such as redundant signal processing channels, regular self-tests and the like.
• simple operating controls also have error detection and prevention measures, but these are generally not sufficient to ensure that the system is safely shut down under all circumstances.
• the present invention relates to signaling devices, safety controls and safety circuits constructed therefrom which meet at least Category 3 of the European Standard EN 954-1, preferably the highest Category 4, or comparable safety requirements.
• the aforementioned EP 1 363 306 A2 describes a so-called safety switch, ie a signaling device, for monitoring the position of protective grilles, protective doors, machine clothing and similar protective devices.
• safety switches have an actuator with which the opening or closing position of the protective door can be determined in a fail-safe manner.
• safety switches are generally electromechanically constructed in practice and the necessary function tests and error monitoring, such as cross-circuit detection, are carried out by or at least with the help of the higher-level safety controller.
• Corresponding safety switches are therefore usually only approved in accordance with EN 954-1 or comparable standards in combination with the safety controller.
• EP 1 363 306 A2 proposes to integrate safety logic into the safety switch, as is already known from light barriers, light grids and other “intelligent” signaling devices
• Proposed safety switch two mutually redundant electronic switching elements, which are controlled by a fail-safe control part.
• An external release signal is looped through the switching elements, which is ultimately fed to the higher-level safety control.
• the release signal can thus be suppressed by the control part, which signals the safety control that the
• the enabled signal can also be looped through several safety switches connected in series, so that each of these safety switches detects the Fr can suppress input signal.
• Such a series connection of signaling devices has already been implemented in practice with electromechanical signaling devices, in which case the release signal was generated by the safety controller and looped back via the series-connected relay contacts of the individual signaling devices.
• the structure of the safety switches described in EP 1 363 306 A2 enables the higher-level safety control to react quickly, even if a larger number of signaling devices are connected to the safety control in series with one another.
• looping through the enable signal limits the maximum spatial distribution of the signaling devices connected in series.
• the entire series is "dead” if one of the signaling devices suppresses the release signal, be it due to a change in the actuator (opening the protective door or the like) or due to an internally detected functional error.
• the flexibility and performance of the safety switches described does not go beyond what has been possible for a long time with comparable relay-based signaling devices.
• a signaling device of the type mentioned in the introduction in which the input of the switching element is internally assigned a fixed potential, preferably a fixed high potential.
• the object is further achieved by a corresponding safety circuit in which the input of the at least one switching element in each signaling device is internally assigned a fixed potential, and in which the output of the at least one switching element in the first signaling device is fed to the control part of the second signaling device, and in which the control part of the second signaling device also controls the at least one switching element of the second signaling device as a function of the first signaling device.
• the new signaling device differs from the safety switch known from EP 1 363 306 A2 in that an enable signal is no longer looped through the at least one switching element. Rather, the release signal is now generated anew in each signaling device.
• the control part of a downstream, second signaling device of a series connection takes into account the output signal of the signaling device located upstream of it. It is therefore easily possible to simulate the looping of an enable signal through several signaling devices so that no difference can be seen from the point of view of the higher-level safety controller.
• the individual signaling devices in a row arrangement are not "dead" if an upstream signaling device has suppressed the release signal.
• a signaling device located downstream to send a message to other subsequent signaling devices and / or the higher-level safety controller by means of a data telegram or the like, which enables the entire safety circuit to react flexibly.
• the data telegram can be transmitted via the existing connections, as shown below with the aid of a preferred exemplary embodiment, ie the wiring effort is low despite increased flexibility.
• each signaling device takes on a repeater function due to the new wiring, and it is therefore possible to realize considerably larger distances between the signaling devices arranged in series with one another. This also enables more flexible plant planning.
• a group shutdown can also be easily implemented due to the new functionality of the signaling devices, since each signaling device in the row arrangement can generate a signal at its output independently of the upstream signaling devices.
• the new signaling device has at least one input, preferably a redundant safety input, for an external release signal which is fed to the control part, the control part also controlling the at least one switching element as a function of the release signal.
• the release signal is fed to the first signaling device by the safety controller.
• the signal connected through to the output of the at least one switching element is fed to the control part of the signaling device.
• the output signal of the switching element (and thus at least indirectly also the output signal of the signaling device) is fed back to the control part.
• the control section is thus able to detect device-internal malfunctions.
• This embodiment is also known per se from EP 1 363 306 A2 and has also been known for a long time from light barriers and other “intelligent” signaling devices and safety switching devices.
• the advantages of this embodiment only come into full advantage on the basis of the present invention, since each signaling device in a row arrangement can pass on an internal functional error regardless of the state of upstream signaling devices.
• control part of the signaling device is designed to detect a device-internal functional error and to generate a data telegram at its output with the aid of the at least one switching element.
• the data telegram is a pulse telegram, i.e. the control part switches the at least one switching element on and off in pulses.
• an address assigned to the signaling device can also be transmitted to the higher-level controller with little effort, so that the safety controller can individually identify each signaling device in a series connection.
• each signaling device has at least two redundant switching elements, each with an input and an output, each of the at least two redundant switching elements being assigned the fixed potential on the input side.
• This design already known per se from safety controls, in combination with the present invention has the advantage that the signaling device can report an internal functional error on the existing signal lines to the higher-level safety controller, even if one of the switching elements is the cause of the functional error.
• the redundancy provided in the known safety switching devices for safety reasons also leads to a higher availability here.
• the signaling device has an input for supplying an operating voltage, the operating voltage being supplied to the at least one switching element as a fixed potential.
• This configuration is particularly advantageous with regard to the repeater function of the new signaling device described above. Because the at least one switching element is connected to the operating voltage on the input side, large distances between a plurality of signaling devices can easily be bridged.
• the signaling device contains a movable actuator which can be moved between a first and at least a second spatial position, the external state variable being a current spatial position.
• the actuator is a transponder.
• the new signaling device is, in particular, a protective door switch, an emergency stop button, a limit or position switch, a sensor for a step mat or a manually operated start or command button.
• the actuator can be integrated in the signaling device or can also be be carried out separately, as is customary, for example, with protective door switches.
• the actuator can be connected to the signaling device optically, inductively, capacitively or in any other way. This configuration is preferred because the above-mentioned signaling devices are relatively simple components which have hitherto had practically no signal processing of their own. The expanded range of functions therefore comes into its own with these signaling devices.
• the use of the present invention in such "simple" signaling devices can also make the use of a higher-level safety controller for smaller applications superfluous by the signaling device activating an actuator without an intermediate safety control via its outputs.
• the new signaling device has a readback input for supplying an external readback signal from an actuator.
• the signaling device of this embodiment thus combines the previously separate functions “record state variable” (sensor) and “shutdown system” (signal processing). Small security applications can thus be implemented very inexpensively.
• the input part is designed to receive a physical measured variable, in particular a speed, a voltage and / or a current, as an external state variable.
• Sensors for recording such status variables are usually installed in a control cabinet, while emergency stop buttons, limit switches or position switches, protective door switches and similar signaling devices are usually installed on the system.
• the advantages mentioned above can also be transferred in the same way to such measuring sensors as signaling devices. For example, several speed monitors can be connected in series in the manner described here, so that multiple moving axes of a system can be monitored very cost-effectively in terms of safety.
• FIG. 1 shows a simplified illustration of a system in which a signaling device according to the present invention is used for security purposes
• FIG. 3 shows a safety circuit with two signaling devices of the type shown in FIG. 2 in a row arrangement
• FIG. 4 shows a time diagram with signal profiles when initializing a safety circuit according to FIG. 3
• Fig. 5 shows another embodiment of a new signaling device.
• a system that is protected with the aid of the invention is designated in its entirety by reference number 10.
• the system 10 here includes a robot 12, the automated movements of which would be dangerous for a person (not shown here) who would be in the range of motion of the robot 12. Therefore, the range of motion of the robot 12, as known per se, is secured with a protective door 14 and protective fences.
• An actuator 16 is attached to the protective door 14.
• a safety switch 18, more generally the fixed part of a signaling device according to the present invention, is located on a fixed frame against which the protective door 14 bears in the closed state.
• the safety switch 18 is connected to a safety controller 20 via several lines. On the output side, the safety controller 20 controls two contactors 22, 24, the contacts of which can interrupt the power supply 26 to the robot 12.
• the system 10 is shown here in simplified form.
• the protective door 14 is usually equipped with at least two safety switches 18 and corresponding actuators 16, one of the safety switches often being arranged in a concealed manner in order to make manipulations more difficult. It also contains one System often other signaling devices, such as emergency stop buttons or other protective door switches (not shown here).
• the required operational control for the robot 12 is not shown here for the sake of simplicity.
• one or more speed monitors can be connected to the drives and / or the moving axes of the robot.
• the safety controller 20 can be a safety relay in a simple scenario, as offered by the applicant under the name PNOZ ®. However, if numerous safety-related signaling devices are needed to protect the system 10, it is advantageous to use a more complex safety controller, such as those sold under the name PSS ® by the applicant safety controls. At least in the latter case, the safety controller 20 usually has a fieldbus connection and further interfaces for communication with the operating control (not shown here) and / or for communication with a higher-level master computer.
• the safety switch 18 has a two-channel redundant structure. Accordingly, the safety switch 18 here has two redundant microcontrollers 30, 32 which monitor one another, which is represented by a double arrow between the microcontrollers. In preferred exemplary embodiments, the microcontrollers are different, that is to say the safety switch 18 has a diverse structure.
• Reference numerals 34, 36 denote two electronic switching elements, which are shown here as field effect transistors. Alternatively, however, bipolar transistors or other, preferably electronic switching elements can also be used.
• the control connection (gate) of the switching element 34 is connected to the microcontroller 30.
• the input 38 (source) is connected to a line 40, to which an operating voltage U B is present during the operation of the safety switch 18.
• the output 42 (drain) is connected to a connection 44 to which the safety switch 18 can be externally wired.
• the output 42 of the switching element 34 thus forms an output signal of the safety switch 18.
• the second switching element 36 is connected to the microcontroller 32 at its control connection (gate). Its input 38 is also connected to operating voltage U B via line 40. Its output 42 is fed to a second output connection 46 of the safety switch 18.
• the signals at the outputs 42 of the switching elements 34, 36 are fed back to the microcontrollers 30, 32 via two voltage dividers 48, 50. This enables the microcontrollers 30, 32 to monitor the respective switching state of the switching elements 34, 36.
• Reference number 52 denotes an input part, with the aid of which the microcontrollers 30, 32 determine the current state of the actuator 16, in this case its spatial position.
• the Actuator 16 a transponder with a signal generating circuit 54 and a transmitting and receiving coil 56.
• An individual coding 58 is stored in the signal generating circuit 54.
• the input part 52 has a transmitting and receiving coil (shown here only symbolically), via which it sends out an interrogation signal.
• the signal generating circuit 54 in the actuator 16 is activated.
• the actuator 16 then sends the stored coding 58 back to the input part 52.
• There the coding 58 is demodulated from the received signal and made available to the microcontrollers 30, 32.
• the actuator 16 is outside the transmission and reception range of the input part 52, which is shown in FIG. 2 at position 16 '. In this case, there is no communication between actuator 16 and input part 52.
• the microcontrollers 30, 32 consequently do not receive any coding, which is interpreted as an open protective door 14. If a second protective door switch or at least a second actuator (not shown) is present, a defect in the actuator 16 or the input part 52 can also be detected.
• the input part 52 can be designed for other types of actuators.
• the actuator can also be integrated in the safety switch 18.
• the safety switch 18 could be an emergency stop button and the actuator in this case would be the push rod of the button.
• the input part 52 contains inductive, capacitive, optical or otherwise term sensors for determining a current position of a mechanically movable actuator.
• the invention can in principle also be applied to light barriers and other signaling devices which differentiate between at least two states.
• the input part is designed for the measurement recording of a physical state variable, as will be explained in more detail below with reference to FIG. 5.
• the safety switch 18 On the input side, the safety switch 18 here has three connections 60, 62, 64, which are each designed as safety inputs and are redundantly connected to the two microcontrollers 30, 32. External enable signals can be supplied redundantly to the microcontrollers 30, 32 via the connections 60 to 64. In addition, in a manner known per se, there is a connection 66 for supplying an operating voltage U B and a ground connection 68. It is understood that the connections mentioned are each accessible on the outside of a housing 70 of the safety switch 18.
• a safety circuit with two of the described safety switches 18 is designated in its entirety with the reference number 80. Otherwise, the same reference numerals designate the same elements as before.
• the two safety switches are labeled 18a and 18b for mutual distinction.
• the safety switch 18a is connected at its connections 60, 62 to outputs of the safety controller 20. These are preferably so-called clock outputs of the safety controller 20, on which two clock signals are different Frequency and / or phase are present, so that cross-circuit detection is possible both in the safety switch 18a and (by reading back, not shown here) in the safety controller 20.
• the safety switch 18a is connected to the operating voltage U B or ground at the connections 66, 68. On the output side, the connections 44, 46 of the safety switch 18a are led to the connections 60, 62 of the subsequent safety switch 18b.
• the two safety switches 18a, 18b are thus arranged in series with one another. In the arrangement shown, the safety switch 18b also receives operating voltage from the safety switch 18a. Alternatively, the safety switch 18b could also be connected to another source for the operating voltage U B.
• the two output signals of the safety switch 18b i.e. the signals present at its connections 44, 46 are fed to safety inputs of the safety controller 20.
• the safety controller 20 On the output side, the safety controller 20 is connected between the power supply 26 and a drive 82 to be switched off, for example an actuator of the robot 12. It is also shown schematically here that the safety controller 20 is connected via a fieldbus 84 to an operating controller 86 for the robot 12 and / or a higher-level master computer. For reasons of clarity, the actuators belonging to the safety switches 18a, 18b are not shown in FIG. 3.
• the functioning of the safety circuit 80 is as follows:
• the safety controller 20 After commissioning, the safety controller 20 generates two clock signals 88, 90 at its outputs, which the safety Switches 18a are supplied as release signals.
• the microcontrollers 30, 32 of the safety switch 18a monitor the current state of the associated actuator with the aid of the input part 52. If the actuator is in the area of the input part 52 and the enable signals 88, 90 are received without any problems, the microcontrollers 30, 32 generate two output signals with the aid of the switching elements 34, 36, which emulate the enable signals 88, 90. However, they could also differ from the clock signals 88, 90, for example with regard to their frequency.
• the second safety switch 18b receives the simulated release signals and, in turn, simulates these at the output if it also detects a closed protective door and proper functioning.
• the safety controller 20 receives the simulated release signals via the lines 92, 94.
• the microcontrollers 30, 32 open the switching elements 34, 36.
• the subsequent safety switch 18b consequently no longer receives the simulated release signals. This is recognized by the microcontrollers in the safety switch 18b and reported to the safety controller 20 by switching off the switching elements 34, 36. The latter can then switch off the drive 82.
• the signal flow takes place in the same way when the safety switch 18a detects a functional fault, for example a cross-circuit at the connections on the input or output side, a breakdown of one of the switching elements 34, 36 or another functional fault.
• a functional fault for example a cross-circuit at the connections on the input or output side, a breakdown of one of the switching elements 34, 36 or another functional fault.
• the safety switch 18a After a short wait time that is stored in the microcontrollers of all the safety switches 18a, 18b and the safety controller 20, the safety switch 18a generates a data telegram 96 on at least one of its output lines by pulsing at least one of the switching elements 34, 36 and opening them again.
• the subsequent safety switch 18b receives this data telegram and forwards it to the safety controller 20 in the same way. If necessary, he can also integrate further information into the data telegram 96.
• the data telegram 96 is implemented as in an asynchronous, serial interface, i.e. it starts with a defined start bit and ends with a defined stop bit. In between there is an arbitrary or fixed number of data bits.
• each data telegram 96 contains a defined number of pulses with a defined pulse duration. The meaning of each individual pulse depends on the protocol that is defined between the safety switches 18 and the safety controller 20.
• the safety switch 18b generates its own data telegram 96 if it in turn detects a functional error.
• the safety switch 18b can generate its data telegrams regardless of whether the safety switch 18a has opened or closed the switching elements 34, 36.
• the data telegrams of the safety switches 18a, 18b contain address information which identifies the safety switch that would like to report information to the higher-level safety controller 20.
• the respective address can be assigned to the safety switch 18a, 18b in different ways.
• each safety switch 18a, 18b can be provided with a multi-stage address selection switch (not shown here), at which the assigned address is set.
• the safety switches 18a, 18b each use the coding 58 of the actuators 16 assigned to them as the address.
• the safety switches 18a, 18b connected in series are assigned an address in an initialization mode after the safety circuit 80 has been started up.
• a preferred method of how this address assignment is carried out is shown in FIG. 4.
• the first safety switch 18 thus receives a permanent high at its input 60 and a single pulse at its input 62 after the operating voltage U B is switched on. As soon as it detects this, it simulates the signal present at its connection 60 (continuous high) at its output 44 (reference number 106). After a waiting time T, it then generates two pulses at its output 46, as in Reference numeral 108 shown.
• the waiting time T serves to recognize whether further impulses are received on the input side.
• the second safety switching device 18b receives the signals 106, 108 at its inputs 60, 62 and simulates them at its outputs 44, 46. In doing so, it adds a further individual pulse to the individual pulses 108 that it receives at connection 62.
• the pulse sequences shown at reference numbers 110, 112 are consequently present at the outputs of the second safety switch 18b.
• further safety switching devices 18c, 18d etc. would simulate a continuous high on one signal line (reference number 114) and a pulse train on the second signal line, and each safety switch would increase the pulse train by one pulse ,
• the safety controller 20 receives the signals according to the reference numbers 114, 116. From the signal 114, the safety controller 20 recognizes that the wiring of channel A is correct. The safety controller 20 recognizes from the pulse sequence 116 that the wiring of the channel B is correct. It can also determine the number of safety switches 18a, 18b etc. arranged in series from the number of pulses (minus 1). In the same way, each safety switch 18a, 18b can recognize its address from the number of pulses received. In this way, when the safety circuit 80 is switched on, an individual address can be automatically assigned to each safety switch arranged in series. If the safety circuit 80 is changed later, a new and correct address assignment to the then existing configuration takes place automatically when the system is switched on again.
• the flexibility of the new signaling devices is further increased here by the input connection 64, which has not been explained so far.
• This connection can be used to feed an external feedback signal into the safety switch 18. It is thus possible, for example, for the safety switch 18 to control a contactor with positively driven contacts independently, ie without a previously used safety switching device or a corresponding safety controller. It is sufficient if the positively driven break contact of the contactor is led to the feedback input 64 of the safety switch 18.
• signaling devices such as the safety switch 18 shown, have a further input connection for applying a start signal. This makes it possible to implement a monitored restart of the system without the usual safety control.
• the respective function of the signaling devices 18 can be parameterized via the input connection 64, as is described, for example, in DE 100 16 712 AI.
• parameters can be set from the outside using different transponder codes.
• FIG. 5 shows an exemplary embodiment of a new signaling device 100 as a speed monitor.
• the same reference numerals designate the same elements as before.
• the signaling device 100 differs from the signaling device 18 from FIG. 2 essentially in relation to the input part 102, which, in contrast to the input part 52, is designed here for measuring a rotational speed.
• the speed detection takes place in this exemplary embodiment without an encoder, in that the input part 102 taps the motor voltages of a rotary drive 104 and evaluates them with regard to their frequency.
• the signaling device 100 is designed as a standstill monitor, ie it monitors the achievement and compliance with a speed of zero. This can be done by the input part 102 tapping and monitoring the generator voltages generated by the expiring rotary drive 104, as is known per se from standstill monitors for safety-related applications.
• the input part 102 detects a voltage, a current or another physical variable using measurement technology, and the microcontrollers control the switching elements 34, 36 as a function of the detected variable, in particular as a function of the detected variable maintaining a predetermined target value.

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• Safety Devices In Control Systems (AREA)
• Burglar Alarm Systems (AREA)
• Circuits Of Receivers In General (AREA)
• Selective Calling Equipment (AREA)
• Emergency Protection Circuit Devices (AREA)
• Amplifiers (AREA)
• Alarm Systems (AREA)

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• 2005
  • 2005-03-23 EP EP05731057.5A patent/EP1738383B2/fr not_active Expired - Lifetime
  • 2005-03-23 ES ES05731057T patent/ES2342543T3/es not_active Expired - Lifetime
  • 2005-03-23 JP JP2007507686A patent/JP5089378B2/ja not_active Expired - Fee Related
  • 2005-03-23 DE DE200550009527 patent/DE502005009527D1/de not_active Expired - Lifetime
  • 2005-03-23 AT AT05731057T patent/ATE467224T1/de active
  • 2005-03-23 WO PCT/EP2005/003073 patent/WO2005101439A1/fr not_active Ceased
• 2006
  • 2006-10-16 US US11/581,742 patent/US7948391B2/en not_active Expired - Lifetime

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