Safety switching device

Abstract

To provide a safety switching device capable of minimizing the number of external terminals and reducing the effort required for cable installation without compromising functionality.SOLUTION: A safety switching device comprises a housing (12) and a circuit configuration (14) arranged in the housing. The circuit configuration includes two switching elements (16) arranged in a safety circuit (18) via first, second, third, and fourth terminals (20; 201 to 204) arranged on the housing. A fifth terminal (20; 205) which can apply a first input signal and a sixth terminal (20; 206) which can apply a second input signal are also provided on the housing. These input signals correspond to the start signals of switching elements. As a result, when the first signal is applied to the fifth terminal and the second input signal is applied to the sixth terminal, the safety circuit is closed. The circuit configuration further includes an electrical component (28) which extracts energy for its own operation from the electrical signals applied to the first, third, fifth, and sixth terminals (201, 203, 205, 206).SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a safety switching device for the safety-related interruption of a safety circuit. [Background technology]

[0002] Safety switching devices are the root and backbone of safe automation technology. As stand-alone devices, they monitor safety functions such as emergency stops, safety gates, light barriers, light grids, safety mats and many others. They perform a given safety function, for example ensuring the safe stopping of a controlled movement, monitoring the position of a movable guard and aborting a closing action if someone enters the protected area. They minimize risks and initiate a safe and reliable reaction in case of a failure or breach of the protected area. Safety switching devices can be found in almost all branches of mechanical and plant engineering, mainly where the number of safety functions is kept manageable.

[0003] Basically, a safety switching device is a switch which switches a safety circuit on or off depending on an input signal. The input signal is supplied to the safety switching device by a safety sensor or a safety transmitter (light barrier, emergency stop button, etc.) and when the safety sensor indicates a safe state, so that the safety switching device closes the safety circuit. If one of the input signals is lost, the safety switching device interrupts the safety circuit, which usually switches off the technical equipment or prevents its starting. Alternatively, the interruption of the safety circuit may also lead to another reaction of the technical equipment which results in a safe state.

[0004] Unlike normal switching relays, a safety switching device can (if wired correctly) ensure that neither a fault in the device itself nor a fault caused externally by a sensor or actuator leads to the loss of the safety function. For this purpose, a safety switching device may be equipped with additional special circuits or a special relay technology compared to a normal switching relay in order to ensure a safe switching process even in the case of a fault.

[0005] A typical design of a safety switching device is redundant: two relays with forcibly guided contacts provide the safety switching contacts, also called safe outputs. Two input circuits each control one of two internal switches. Summary of the Invention [Problem to be solved by the invention]

[0006] Since a separate safety switching device is generally used for each safety function, the number of safety switching devices, and therefore the space required in the associated control cabinet, increases with the safety functions of the technical installation.

[0007] The increasing number of safety switching devices required leads to the requirement to minimise the space required for one safety switching device. In addition to the actual switching elements, the number of external terminals is of decisive importance in this respect. The more external terminals are required in a safety switching device, the more installation space the device requires.

[0008] The object of the present invention is to provide an improved safety switching device which requires as little installation space as possible while increasing the expected range of functions, reduces the effort required for cable laying, and prevents errors during cable laying. [Means for solving the problem]

[0009] The object is solved by a safety switching device comprising a housing and a circuit arrangement arranged in the housing, the circuit arrangement comprising two switching elements, which can be arranged in the safety circuit via first, second, third and fourth terminals arranged in the housing and which are capable of redundantly closing the safety circuit when an activation signal is applied to each switching element. Furthermore, a fifth terminal and a sixth terminal are provided in the housing, to which a first input signal and a second input signal, respectively, corresponding to the activation signal of the switching elements can be applied, so that the safety circuit is closed when the first and second input signals are applied to the fifth and sixth terminals. The circuit arrangement arranged in the housing comprises a further electric element, which is configured to derive energy for its own operation from an electric signal applied to at least one of the first, third, fifth and sixth terminals.

[0010] The idea of ​​the present invention is therefore to provide a safety switching device that is arranged to take electrical energy from a signal applied to one of its terminals. The energy taken is used to operate an electric element within the safety switching device. In other words, the electric element takes the current required for its intended use from the energy taken from the signal.

[0011] The safety switching device may for example be a safety switching device specially designed for active sensors which actively supply an input signal which can take additional energy. In addition to controlling the internal switching element, the supplied energy can contribute to the power supply of at least one other element of the safety switching device. In this way, external terminals for a separate power supply can be dispensed with.

[0012] The reduced number of terminals allows the safety switching device to be arranged in a housing with smaller dimensions than a similar full switching device with external supply terminals. In particular the width of the housing with respect to the required installation space can be reduced. It is also conceivable to use the freed terminals for other functions. This makes it possible, for example, to increase the number of safety outputs of the safety switching device without the need to use a separate device or a device providing additional external terminals for the additional safety outputs. The ability to reduce the number of external terminals therefore contributes to an improvement by making it possible to use a smaller housing with the same functionality or by providing additional functionality with the same housing size. Furthermore, the reduced number of external terminals simplifies the wiring of the safety switching device and prevents incorrect wiring. In this way the object of the invention is completely solved.

[0013] In a further refinement, the electrical signal may be any one of the first input signal and the second input signal.

[0014] According to this refinement, energy for an additional electric element can be derived from one or both input signals. In this case, the safety switching device can be configured for a special application with active sensors. An active sensor is a safety sensor that supplies an input signal independently of the power supply to the safety switching device. The active sensor may have an output signal switching device (OSSD) for generating the input signal. As part of a safety sensor (in particular an electro-sensitive protective equipment (ESPE)), the output signal switching device can supply a signal that is interrupted in a fail-safe manner if the sensor part of the safety sensor is activated. By specializing the safety switching device for active sensors, a terminal for an outgoing signal intended for a passive sensor and supplied with potential by the safety switching device can be omitted. As a result, further external terminals in addition to the power supply terminals can be omitted or assigned differently when the safety switching device is specialized for active sensors.

[0015] In a further refinement, the electrical signal may be a potential which is switched by the switching element of the safety switching device.

[0016] According to this refinement, the energy for the further electric element is derived from the potential applied to the first or third terminal. The applied potential is the potential in the safety circuit which is switched by the switching element in the safe state. The switched potential can control a contactor in the power supply of the technical installation monitored by the safety switching device. In this case, the electric signal can be a DC voltage of 24 V, which is often used in industrial environments. The safety switching device can use this voltage to power further electric elements.

[0017] In a further refinement, the electrical signal may be electrically isolated from the other electrical elements.

[0018] According to this refinement, the safety switching device can be decoupled from the electric signal, so that the safety switching device is protected from overvoltages from the electric signal. The coupling can be inductive or capacitive. This effectively contributes to increasing the fault tolerance of the safety switching device.

[0019] In a further refinement, the additional electric element may be an operating indicator, in particular an LED.

[0020] The safety switching device may have a display (operation indicator) which indicates the operating state of the device. The operation indicator may be required by standards for the proper operation of the safety switching device. In a further refinement, the energy for activating the operation indicator may be derived from the electric signal, so that no additional power supply is required for the operation indicator. This design is particularly suitable if the operation indicator is the only electric element, apart from the safety switching device, which needs to be actively powered, since a separate power supply can be dispensed with entirely. In the case of an operation indicator, this can also be preferably coupled directly to the corresponding input signal or to the potential to be switched.

[0021] In a further refinement, the further electric element may have a first status indicator, which indicates the status of one of the switching elements. According to this refinement, the status display (status indicator) of the channel can be supplied with an operating voltage in a simple manner, so that a separate power supply is not required. This refinement can therefore also help to simplify the required device electronics.

[0022] In a further refinement, the additional electric element may be an electronic element (e.g. a microcontroller) which performs the safety-related tasks of the safety switching device. In this refinement, the energy absorbed by the signal can be used to supply a microcontroller which is used to control and monitor the safety switching device. According to this refinement, a separate power supply for the safety switching device can be dispensed with if the safety switching device has an extended range of functions which requires a microcontroller.

[0023] In a further refinement, the further electrical element may be electrically connected to the first, third, fifth and / or sixth terminals.

[0024] According to this refinement, further electric elements are connected to one or more terminals to which an electric signal can be applied. Depending on the type of electric signal, the electric elements can be connected to the terminals directly or via additional components. In this way, power supply can be realized simply and efficiently using an externally applied signal.

[0025] In a further refinement, the safety switching device may further comprise an electric component which is connected to the further electric element and provides a voltage and / or power supply for operating the further electric element. According to this refinement, a further electric component can be provided which converts the energy received from the electric signal for operating the further electric element. The electric component may be a resistor which is supplied with a voltage and which acts as a current source for, for example, an LED. It is also possible to use a rectifier or a voltage regulator. This design makes it possible to broaden the range of possible electric signals which can be used as an energy source.

[0026] In a further refinement, the safety switching device may comprise an energy storage device which buffers the energy for operating the further electric element, the electric signal charging the energy storage device. According to this refinement, an energy storage device can be provided upstream of the further electric element in order to supply the necessary energy for the electric element. The energy storage device may be an inductive or capacitive component which buffers or smooths the voltage or current required for the operation of the other electric components. This means that different electric signals can be used as energy sources. This design therefore contributes to effectively adapting the device to a larger number of electric signals.

[0027] In a further refinement, the housing may be provided with a seventh terminal to which a reference potential for the electronic device can be connected. According to this refinement, at least one additional terminal can be provided in order to make a uniform reference potential available. Using the reference potential, a supply voltage can be easily generated from an electrical signal, if this corresponds to a potential. It goes without saying that the potential connected to the second or fourth terminal can also be used as a reference potential, without the need for a seventh terminal.

[0028] In a further refinement, the additional electric elements can be powered exclusively from the energy extracted from the electric signal. According to this refinement, therefore, no further energy source is required to operate the additional electric elements. This refinement is therefore particularly suitable for reducing external terminals and simplifying the circuitry.

[0029] In a further refinement, the housing may have two side surfaces and a plurality of functional surfaces connecting the side surfaces, which together define an enclosed space in which the circuitry is disposed, the distance between the side surfaces defining a maximum width of the housing, and the terminals are disposed on the functional surfaces, which may be equal to or less than 22.5 mm.

[0030] The safety switching device may have a housing suitable for installation in a switch cabinet. Such a housing typically has a width that is many times smaller than the width and height of the housing. The housing may for example be box-shaped with two side surfaces and four functional surfaces connecting the sides. One of the functional surfaces (the front) faces the user when properly installed in the switch cabinet and carries the external terminals. The two side surfaces define the width of the housing. Reducing the external terminals therefore makes it possible to reduce the width of the housing.

[0031] It is understood that the features mentioned above and that will be described below can be used not only in the combinations indicated in each case, but also in other combinations or by themselves, without departing from the scope of the invention.

[0032] Examples of embodiments of the invention are illustrated in the drawings and are explained in more detail in the following description. [Brief description of the drawings]

[0033] [Figure 1] 1 shows a schematic diagram of a safety switching device according to a first embodiment of the present disclosure; [Diagram 2] FIG. 2 shows a schematic diagram of a safety switching device according to a second embodiment of the present disclosure. [Diagram 3] 1 shows a simplified schematic diagram outlining one application of a safety switching device according to the present disclosure; [Figure 4] FIG. 2 shows a simplified perspective view of an embodiment of a housing of a safety switching device according to the present disclosure; [Diagram 5] A safety switching device according to the prior art is shown as an example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0034] 1 shows in a schematic diagram a safety switching device according to a first embodiment to which the present disclosure relates, the safety switching device being designated as a whole by the reference number 10.

[0035] The safety switching device 10 comprises a housing 12 and a circuit arrangement (electronics) 14 arranged in the housing 12. The circuit arrangement 14 comprises two switching elements 16 (in particular forcibly guided relays), the contacts of which may be arranged in a safety circuit 18. The contacts of the two switching elements 16 are led to the outside via terminals 20 of the housing 12. The safety switching device 10 comprises at least a first terminal 201, a second terminal 202, a third terminal 203 and a fourth terminal 204 for redundantly leading the safety circuit via the contacts of the switching elements 16.

[0036] Furthermore, the safety switching device 10 has a first input circuit 22 and a second input circuit 24, which are also accessible from the outside via the terminals 20 of the housing 12. The first input circuit 22 is connectable to the outside via a fifth terminal 205 and the second input circuit 24 is connectable to the outside via a sixth terminal 206, whereby the input circuits 22, 24 are preferably connectable to the outside exclusively via the fifth and sixth terminals 205, 206. A first input signal from a safety sensor (not shown here) can be received via the fifth terminal 205 and a second input signal from a safety sensor (not shown here) can be received via the sixth terminal 206. The first and second input signals are then present at said fifth and sixth terminals 205, 206 of the safety switching device 10 when the safety sensor signals a safe state of the technical installation to be monitored.

[0037] When the first and second input signals are appropriately applied to the fifth and sixth terminals 205, 206, the input circuits 22, 24 supply an activation signal 26 to said two switching elements 16, on the basis of which the switching elements 16 close the safety circuit 18. If one of the input signals is absent or if the safety switching device 10 detects in any other way a malfunction of the input signals of the safety switching device 10 or of other devices, the activation signal 26 is not supplied, so that the switching element 16 interrupts the safety circuit 18 and thus forces a safe state in the technical equipment to be monitored.

[0038] The safety switching device 10 also comprises a further electrical element 28. The electrical element 28 may be part of the circuit arrangement 14 and may for example be arranged together with the switching element 16 and the input circuits 22, 24 on a common circuit board.

[0039] The electric element 28 may be any electric or electronic component which performs the functions of the safety switching arrangement 10 in addition to the switching element 16. In various embodiments, the electric element 28 may be a display (indicator), for example realized by one or more light-emitting diodes 30. Alternatively or additionally, the electric element 28 may be a control element, such as a microcontroller 31 or an FPGA, and may be responsible for the control functions of the safety switching arrangement. Such a control element could perform additional safety-related tasks of the safety switching arrangement 10, such as for example a continuous comparison of the input signals, cross-circuit detection or diagnostic functions. Of course, the electric element 28 is not limited to these functions.

[0040] The electric element 28 is configured to take energy for its operation from an electric signal applied to at least one of the first, third, fifth and / or sixth terminals 201, 203, 205, 206. The electric signal can correspond to one or both input signals or to a signal conducted via the safety circuit 18. The electric signal can for example be a static potential applied to the aforementioned terminals, from which it can take energy directly. Alternatively, a dynamic signal (clock signal) can be applied to the terminals, from which it can take energy, either from a static component or as an effective value.

[0041] The electrical element 28 may also be a safety-relevant element which contributes to the fulfilment of normative requirements which can be imposed on the safety switching device. It is for example conceivable that a safety switching device only fulfils said normative criteria if it is able to visualise its state or the state of its switching elements (channels) by means of an operation or status indicator. It is also conceivable that in addition to the safe switching of a safety circuit, the safety switching device must fulfil other functions provided by an electrical (integrated) circuit in order to realise a certain safety level.

[0042] Regardless of the type of the electric element 28, the energy required for the electric element 28 is taken from the electric signal present at the above-mentioned terminals. The safety switching device preferably does not have an additional power supply, such as a voltage or current source, for operating the electric element 28. By omitting an additional power supply for the additional electric element 28, external terminals provided for this purpose on the housing 12 can advantageously be omitted or used for other purposes.

[0043] The provision that the safety sensors connected to the input circuits 22, 24 are active safety sensors also makes it possible to dispense with additional terminals in the present safety switching device compared to known safety switching devices. Active safety sensors are characterised by being able to provide an input signal independently of the safety switching device 10.

[0044] In other words, these are devices that have their own power supply and are provided with an output signal switching device (OSSD) that can provide a safety input signal depending on the sensor part of the safety sensor. Unlike passive safety sensors such as emergency stop buttons, active safety sensors do not rely on a safety switching device to provide a switching potential for the safety sensor. Therefore, by being dedicated to active sensors, no additional terminals are required on the housing to provide a switching potential. Each input circuit therefore only requires one connection on the housing to receive the input signal of the active safety sensor.

[0045] If we limit ourselves to active safety sensors, then depending on the function, an electrical signal can be applied as input signal to the safety switching device, with the added advantage that energy not provided by the safety switching device can be taken from it. In the case of output signal switching devices (OSSDs), the input signal provided is called the OSSD signal, whose electrical characteristics are usually specified in standards for the various applications. It is therefore easy to provide power to other electrical elements based on the OSSD signal, since the power supply can be adapted to the electrical characteristics.

[0046] The electrical element 28 may for example be selected to be directly coupled to the OSSD signal so as to be energized when the OSSD signal is present. However, it is also conceivable to provide further components connected between the terminals of the electrical signal and the electrical element 28 or connected in parallel with the electrical element 28 in order to set a suitable voltage supply for the electrical element 28. The other components may be simple resistors or rectifying elements such as diodes. Furthermore, a voltage regulator may be connected between the terminals of the electrical signal and the electrical element 28 in order to set a defined and constant voltage at the electrical element 28. However, the present disclosure is not limited to any particular form of energy extraction.

[0047] In addition to the above-mentioned first to sixth terminals 201 to 206, the safety switching device may optionally have further terminals, as shown in the embodiment illustrated here. For example, the safety switching device may have a seventh terminal 207 and an eighth terminal 208. The seventh and eighth terminals 207, 208 form further safety outputs similar to the two safety outputs formed by the first and second terminals 201, 202 and the third and fourth terminals 203, 204. In this way, a safety output is formed in each case by two terminals 20, which are connected via the switching contacts of the switching element 16. As shown here, the safety switching device 10 may have three safety outputs.

[0048] A ninth terminal 209 may be provided in the safety switching device 10, which is coupled to the circuit arrangement 14 of the safety switching device 10. For example, a reference potential may be applied to the ninth terminal 209, which together forms a supply voltage for the other electrical elements 28. The reference potential may for example be a common earth potential for the circuit arrangement 14. In principle, such a potential could also be applied to the second or fourth terminal, so that no additional terminals would be necessary. However, measures would then have to be taken to galvanically decouple the reference potential from the other circuit arrangement 14.

[0049] Additionally, the safety switching device 10 may have further devices, circuits and terminals, as indicated by dotted lines in this embodiment. Another circuit may be a start circuit 32, which can be used for example to control the switch-on process. The start circuit 32 may receive a start signal via a tenth terminal 210 and may be designed such that the switching element 26 only closes the safety circuit 18 when the start signal is present. A diagnostic device 34 is also conceivable, providing a signal at an eleventh terminal 211 signalling the current switching state of the switching element.

[0050] Finally, the safety switching device 10 may have twelfth and thirteenth terminals 212, 213, which are connected via the contacts of the switching element 16 as well as the safety outputs (terminals 201-204; 207, 208), but not via positively driven normally open (NO) contacts, but via positively driven normally closed (NC) contacts. A normally open (NO) contact is a contact that closes the connection between the contacts when the switching element is activated (i.e. switched on), and a normally closed (NC) contact is a contact that opens the connection between the contacts when the switching element is activated. The twelfth and thirteenth terminals 212, 213 can be used as feedback circuits and can be connected to the starting circuit 32, for example to prevent false restarts.

[0051] According to the first embodiment, the safety switching device 10 may have thirteen terminals as shown here. However, as shown above, six terminals are sufficient for the main function of the safety switching device 10 (i.e. safe interruption of the safety circuit in response to redundant input signals). In the safety switching device 10 according to the first embodiment, the housing 12 can therefore be reduced in size compared to safety switching devices which usually have ten or more external terminals to provide their main function. Alternatively or in addition, free terminals may be used for other tasks. An example of this is shown in FIG. 2.

[0052] 2 shows in a schematic diagram a safety switching device according to a second embodiment of the present disclosure, the safety switching device here being designated as a whole by the reference number 10.

[0053] In FIG. 2, elements having the same functions are indicated by the same reference numerals as in FIG. 1, and detailed descriptions of these elements will be omitted.

[0054] The safety switching device 10 according to this second embodiment comprises a housing 12, a circuit arrangement 14, two switching elements 16, a plurality of terminals 20, and first and second input circuits 22, 24. The plurality of terminals 20 includes first to sixth terminals 201 to 206. Furthermore, the safety switching device 10 comprises an electric element 28 which, as explained for the first embodiment, derives its operating energy from an electric signal present at the first, third, fifth or sixth terminal.

[0055] As in the first embodiment, the seventh to thirteenth terminals 207 to 213 may be optionally provided in the second embodiment in the same manner.

[0056] The second embodiment differs from the first embodiment in the design of the switching element 16. Here, the switching element 16 has an additional actively driven NO contact, which is guided to the outside of the housing 12 via the fourteenth, fifteenth, sixteenth and seventeenth terminals 214, 215, 216, 217. The fourteenth and fifteenth terminals 214, 215 form a fourth safety output, and the sixteenth and seventeenth terminals 216, 217 form a fifth safety output of the safety switching device 10.

[0057] In the safety switching device 10 according to the second embodiment, five safety outputs can thus be advantageously provided without significantly increasing the number of external terminals 20 compared to prior art safety switching devices. This is made possible by removing or releasing external terminals in the input circuit or power supply of the safety switching device as a result of the described energy extraction.

[0058] FIG. 3 shows in a simplified schematic diagram an overview of possible applications of the safety switching device 10 according to the present disclosure.

[0059] FIG. 3 shows an automated robot 38 as technical installation 36 to be monitored. The robot 38 has a defined working area, in which a robot arm 40 can move. Access to the working area is protected by a safety sensor. Here, the safety sensor is a non-contact protective device (ESPE) in the form of a light grid 42. The light grid 42 has a first part 44 and a second part 46, between which a light beam can be exchanged. The light grid 42 signals a safe state only if the light beam is exchanged in a defined manner and no other errors have occurred in the light grid 42. The signaling occurs via an output signal switching device (OSSD) 48, which provides a redundant output signal (OSSD signal 50) if the light grid 42 is working correctly and no access to the technical installation 36 has been recorded.

[0060] The safety switching device 10 according to the embodiment of the present disclosure is connected to the output signal switching device 48 of the light grid 42, for example via a cable 52. The safety switching device 10 thus redundantly receives the OSSD signals 50 as first and second input signals and switches the switching element 16 accordingly. The switching element 16 is arranged in the safety circuit 18 in the manner described above, so that the redundant contactor 54 is energized when the OSSD signal 50 is provided by the light grid 42. Also, the normally open contacts 56 of the contactor 54 can be arranged in the power supply of the technical equipment 36, so that power is provided to the technical equipment 36 only if and as long as the output signal switching device 48 provides the OSSD signal 50. In this way, the safety switching device 10, in cooperation with the light grid 42, provides a safety function of monitoring access to the technical equipment 36.

[0061] The safety switching device 10 can be arranged in a control cabinet 58 together with other control devices. In particular, further switching devices can be arranged in the control cabinet 58, via which additional safety functions can be realized. The other safety switching devices are indicated here by dashed lines. The individual safety switching devices can be arranged next to each other on a top-hat rail 60. Terminals 20 for wiring and additional indicators 62 are respectively arranged on a front face 64 of the safety switching device, which face towards the user after installation in the switch cabinet 58. The width of the front face 64 essentially defines the required installation width 66 of the safety switching device and essentially depends on the number of required terminals 20 on the respective front face 64. A standard dimension for the installation width 66 of a single safety switching device is given as, for example, 22.5 mm.

[0062] By reducing the number of external terminals 20 of the safety switching device according to the present disclosure, the actual installation space required for the safety switching device in the control cabinet 58 can thus be reduced. At the same time, if no external power supply is required for the safety switching device, the wiring is simplified. In principle, by reducing the number of terminals 20, the risk of incorrect wiring can be effectively reduced.

[0063] FIG. 4 shows a simplified perspective view of an embodiment of a housing of a safety switching device according to the present disclosure.

[0064] According to Fig. 4, the safety switching device 10 is arranged in an essentially rectangular housing 12. The box-shaped housing 12 has two opposing side faces 68, 70 and, in this example, four functional faces 72, 74, 76, 78 connecting the side faces 68, 70. The functional face 72 corresponds to the front face 64 of the safety switching device 10 when the safety switching device 10 is mounted as intended in a control cabinet. For mounting, the housing 12 may for example have a holder for mounting on a top hat rail 60 on the functional face 78 opposite the front face 64.

[0065] The main operating and indicator elements of the safety switching device as well as the external terminals 20 are arranged on a functional face 72 which serves as the front face and which faces towards the user after installation in the control cabinet.

[0066] In this embodiment, six external terminals 20 and a display element 62 are provided on the front surface 72 of the safety switching device 10. The six external terminals 20 correspond to the first to sixth terminals 201 to 206 described above and can be realized, for example, by screw or spring-loaded terminals as commonly used in automation technology. The indicator 62 can, for example, have three indicators, indicating the operating state of the entire safety switching device and the individual states of the two switching elements. The indicator 62 can be considered as an electric element 28 within the meaning of the present disclosure and the power supply to the indicator can be provided via an electric signal applied to the terminals 201 to 206 in the manner described above.

[0067] By reducing the number of external terminals 20 in the manner described above, the installation width 66, which corresponds to the maximum distance between the side surfaces 68, 70, when the terminals 20 are arranged on the front surface 72 of the housing 12 in the manner customary in automation technology, can be advantageously reduced. In this way, a safety switching device 10 can be designed which is suitable for special safety functions (e.g. in conjunction with ESPE) as shown in Figure 3 and which has a smaller width 66 than a similar standard device. In addition, such a safety switching device advantageously reduces wiring costs and wiring errors.

[0068] Finally, Figure 5 shows a reference example of a safety switching device 80 according to the state of the art. The safety switching device 80 is distinguished from the safety switching device 10 according to the first embodiment of the present disclosure by a power supply 82 for the internal circuitry which can be coupled to an external power supply via two terminals 84, 86 on a housing 88.

[0069] In addition, the present embodiment differs in that there is no corresponding device for the above-mentioned retrieval of energy from the electrical signal applied to the other terminals and for the use of the retrieval of energy to supply electrical elements of the safety switching device that do not correspond to the switching element, rather, in the prior art, an additional power supply 82 in the safety switching device 80 supplies electrical elements within the scope of the present disclosure.

[0070] The prior art safety switching device 80 further includes two input circuits 90, 92, each having two external terminals on the housing 88. Additional terminals 94, 96 to the input circuits 22, 24 are used to provide output signals that can be switched via a passive safety sensor and fed back to inputs 98, 100. Thus, the safety relay 80 is not designed for specific use with active safety sensors, but rather for general use with either passive or active safety sensors.

[0071] The safety switching device 10 according to the first and second embodiments is characterized by a reduced number of external terminals or by different roles of the available terminals, but these embodiments only illustrate the subject matter of the invention by way of example, the invention being defined by the following claims.

Claims

1. A safety switching device (10) for driving a safety circuit (18) in a safety-related manner, comprising: A housing (12) and a circuit arrangement (14) disposed within the housing, the circuit arrangement (14) comprises two switching elements (16) which can be arranged in the safety circuit (18) via first, second, third and fourth terminals (20; 201-204) arranged on the housing (12), the switching elements (16) being capable of redundantly closing the safety circuit (18) when an activation signal is present at each switching element (16); a fifth terminal (20; 205) and a sixth terminal (20; 206) are provided on the housing (12) to which a first input signal and a second input signal corresponding to the activation signal of the switching element (16) can be applied, respectively, so that the safety circuit (18) is closed when the first and second input signals are applied to the fifth and sixth terminals (205, 206); The circuit arrangement (14) disposed within the housing (12) comprises an electrical element (28) configured to derive energy for its own operation from an electrical signal applied to at least one of the first, third, fifth and sixth terminals (201, 203, 205, 206).

2. 2. The safety switching device according to claim 1, wherein the electrical signal is one of the first input signal and the second input signal.

3. 2. A safety switching device according to claim 1, wherein the electrical signal is at a potential which is switched by the switching element (16).

4. 2. The safety switching device according to claim 1, wherein the electrical signal is electrically isolated from the electrical element (28).

5. 2. Safety switching device according to claim 1, wherein the electric element (28) is provided with an operating indicator, in particular an LED.

6. 2. The safety switching device according to claim 1, wherein the electrical element (28) comprises a first status indicator for indicating a status of one of the switching elements (16).

7. 2. Safety switching device according to claim 1, wherein the electric element (28) is an electronic element, in particular a microcontroller (31), which performs the safety-related tasks of the safety switching device (10).

8. 2. The safety switching device according to claim 1, wherein the electrical element (28) is electrically connected to any one of the first, third, fifth and sixth terminals (201, 203, 205, 206).

9. 2. The safety switching device according to claim 1, further comprising an electric component connected to the electric element (28) and for establishing at least one of a voltage supply and a power supply for operating the electric element (28).

10. 2. The safety switching device of claim 1, further comprising an energy storage device for buffering the energy for operating the electrical element (28), the electrical signal charging the energy storage device.

11. 2. A safety switching device according to claim 1, wherein the housing (12) is provided with a seventh terminal (207) to which a reference potential for the circuit arrangement (14) can be connected.

12. 2. The safety switching device according to claim 1, wherein the electric element (28) is powered exclusively from the energy extracted from the electric signal.

13. 13. The safety switching device according to any one of claims 1 to 12, wherein the housing (12) has two side surfaces (68, 70) and a number of functional surfaces (72, 74, 76, 78) connecting the side surfaces, which together define an enclosed space in which the circuit arrangement (14) is disposed, the spacing between the two side surfaces defining a maximum width (66) of the housing (12), and the terminal (20) is disposed on one of the functional surfaces (72, 74, 76, 78).

14. 14. Safety switching device according to claim 13, wherein said maximum width (66) is less than or equal to 22.5 mm.

15. A safety switching device according to any one of the preceding claims, wherein the first, second, third and fourth terminals (201-204) arranged on the housing represent two safety outputs, each capable of interrupting the safety circuit (18), and six further terminals (207, 208; 214-217) are provided on the housing (12), which form three further safety outputs.

16. The safety switching device according to any one of the preceding claims, wherein the first input signal is a coded signal, in particular an OSSD signal (50), and is provided by an output signal switching device (48) of a protection device, in particular a non-contact protection device.

17. The safety switching device according to any one of the preceding claims, wherein the terminals (20) of the safety switching device are screw terminals or spring terminals.

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