DEVICE AND METHOD FOR MONITORING A SWITCH

Description

TECHNICAL FIELD

[0001] The present invention relates to a device and a method for monitoring the operating state of a switch, in particular its end positions. STATE OF THE ART

[0002] In most switch designs, movable parts of the switch (switch blades and, if applicable, the switch frog) are mechanically adjusted between a left and right end position to provide a route. In the end positions, the switch is mechanically locked by a switch lock. Switches can be remotely controlled by a signal box. To move the switch between the left and right end positions, a switch drive with a servomotor is used for remotely controlled switch gears. In certain switch designs, such as long, high-speed switch gears, multiple switch drives can be arranged on a single switch gear.

[0003] In the Fig. 1A switch 1 is schematically illustrated in its left end position L, in which Fig. 2 in its right end position R. The designations "left" and "right" refer to an absolute reference system of the switch, namely the position relative to the direction of travel F in which the switch forms a junction. The end positions L and R are therefore also referred to as absolute positions. In the layout design and in the interlocking software, reference is made exclusively to these absolute positions.

[0004] The switch drive can be arranged in different ways on the switch. In particular, it can be arranged on the left or right side of the switch with respect to the direction of travel F. Figures 1 and 2A switch drive 2 is shown schematically, which is arranged to the left of the switch. The switch drive 2 can have a push rod 3, with which the movable parts of the switch are moved from the left to the right end position and vice versa. When the push rod 3 is extended, the switch assumes the left end position ( Fig. 1 ), with the push rod 3 retracted, the right end position ( Fig. 2 ). If the switch drive is mounted on the right instead of the left, the situation is exactly the opposite. The relationship between the operating state of the switch drive (push rod retracted or extended) and the absolute position of the switch (left or right end position) depends on how the switch drive is mounted on the switch.

[0005] For several decades, a standardized electrical interface has existed between the interlocking and the point machine in the form of the so-called "four-wire interface." This interface is widely used in German-speaking countries. The interface has four connectors, designated X1, X2, X3, and X4. These four connectors transmit both the drive power for the actuator during switching operations and currents for monitoring the position of the point in the idle state. Examples of point machines that operate with the four-wire interface include the Siemens S 700 K, Thales FieldTrac 6341 L700H, and Thales FieldTrac 6343 L826H systems.

[0006] The four-wire interface can be used in two operating modes: switchover mode and monitoring mode. A control device in the interlocking system switches between the two operating modes.

[0007] During switchover operation, a three-phase current of 400 VAC is applied to the actuator from the interlocking via the interface. The phase position of the actuator windings determines its direction of rotation. The actuator switches the switch between its two end positions.

[0008] In monitoring mode, a DC voltage, typically in the range of 48 to 60 VDC, is applied to two of the four terminals of the four-wire interface in the interlocking system. These are terminals X1 and X3 for monitoring the left end position, and terminals X2 and X3 for monitoring the right end position. The interlocking system measures the resulting current through these terminals; the resulting voltage at the other two terminals is determined. Based on the voltage and current measurements, it can be determined whether the switch has reached the monitored end position.

[0009] In the Figures 3 and 4is an example and in a very schematic form a switch drive with a four-wire interface in the left ( Fig. 3 ) or right end position ( Fig. 4 ) is illustrated. Monitor operation via the four-wire interface is explained in more detail below.

[0010] The four-wire interface has proven itself over decades. However, a significant disadvantage of the four-wire interface is that the circuit is symmetrical with respect to the X1 and X2 connections (see Figures 3 and 4 This makes it impossible to detect in the signal box if connections X1 and X2 are accidentally swapped. Swapping the connections can result in the switch being operated in a different absolute position than intended, which can result in serious accidents.

[0011] To make matters worse, in monitoring mode, it's not the absolute position of the switch (left or right end position) that's determined, but rather the position of the push rod ("extended" or "retracted"). However, as explained above, the absolute position of the switch, which corresponds to a specific position of the push rod, depends on which side of the switch the switch drive is mounted on. This further increases the risk that the interlocking system, in monitoring mode, will infer an incorrect absolute position of the switch via the four-wire interface.

[0012] It is therefore necessary to ensure correct installation by performing a system inspection every time after maintenance work. This is very labor-intensive and time-consuming.

[0013] In addition to the four-wire interface, other types of interfaces are also known for switch control. For example, there is the system-related 7-wire interface, which has separate wires for switch operation and monitor operation. In some systems, monitor operation can be carried out with pulsed DC currents. These interfaces also present similar problems to the four-wire interface.

[0014] EP 1 524 167 A2 discloses a circuit arrangement for generating a railway-safe feedback signal for an executed command. The command is fed to a first railway unit and transmitted via a line to a second railway unit for execution. The command is transmitted via a two-wire line using an alternating current source contained in the first railway unit. The feedback signal is generated from the current flowing between the first and second railway units. PRESENTATION OF THE INVENTION

[0015] It is an object of the present invention to provide a device for checking the operating status of a point which makes it possible to determine the operating status in the interlocking system in a manner redundant with traditional monitoring operation. In particular, the device should be usable in such a way that it makes it possible to determine the absolute position of a point in the interlocking system. The device should be operable via an already existing line between the point drive and the interlocking system, in particular via a four-wire interface, i.e. the use of the device should not require any additional electrical lines. When operated via a four-wire interface, the monitoring result should be independent of a swapping of connections X1 and X2.

[0016] This object is achieved by a device according to claim 1. Further embodiments are specified in the dependent claims.

[0017] A device for monitoring the operating status of a switch is specified, which has: a device for determining the operating state of the switch; a readout signal generator which cooperates with the device for determining the operating state and is designed to generate a readout signal, wherein the readout signal is an AC signal with at least one readout frequency whose value depends on the determined operating state of the switch; and a first coupling device for coupling the readout signal generated by the readout signal generator into an electrical line between a switch drive of the switch and a signal box.

[0018] According to the invention, a readout signal in the form of an AC signal is coupled into a line between the point machine and the interlocking system. The readout signal contains at least one oscillation whose frequency depends on the operating state of the point. The frequency content of the readout signal thus indicates the operating state of the point. The readout signal can be extracted from the line in the interlocking system, and the frequency content of the AC signal can be analyzed to monitor the operating state of the point. The readout signal can be transmitted via an existing line; therefore, no separate line is required for the use of the device according to the invention. This makes the device according to the invention easy to retrofit into existing systems.

[0019] In particular, the device according to the invention can be operated on a traditional four-wire interface. When operated on a four-wire interface, the device according to the invention can correctly display the operating status of the switch even if the X1 and X2 connections on the interface are swapped.

[0020] When used with a four-wire interface, the device according to the invention can be configured so that the readout signal generator does not require a separate power supply, since in traditional monitoring mode of the point machine, a DC voltage is always present between at least two terminals of the four-wire interface. This voltage can be used as the supply voltage for the readout signal generator.

[0021] If the device for determining the operating status is arranged on the switch independently of the switch drive, the device according to the invention can monitor the absolute position of the switch, regardless of the side of the switch on which the switch drive is located.

[0022] The device for determining the operating status can also be located in the switch drive. In this case, this device determines the position of the switch relative to the switch drive instead of the absolute position. Even in this case, the device according to the invention has the advantages of providing redundancy compared to traditional monitoring operation and being robust against interchanging the X1 and X2 connections of the four-wire interface.

[0023] In some embodiments, the readout signal contains only a single oscillation with a specific readout frequency at any given time, i.e., the readout signal in this case does not represent a superposition of multiple oscillations with different frequencies. However, it is also conceivable for the readout signal to represent a superposition of multiple (e.g., two, three, or four) oscillations with different readout frequencies. The value of all readout frequencies preferably lies in a frequency range between 100 Hz and 50 kHz, in particular between 100 Hz and 20 kHz, between 100 Hz and 10 kHz, or between 100 Hz and 5 kHz. All frequency specifications refer to the sinusoidal fundamental oscillation, neglecting the harmonic components. Preferably, the harmonic components of the readout signal are small (amplitude of each harmonic component less than 10%, preferably less than 2% of the amplitude of the fundamental oscillation), i.e.Preferably, the readout signal at any given time essentially corresponds to a single sine wave or a superposition of a few, for example, two or three, sine waves in the specified frequency range. Low-frequency AC signals in the specified frequency range are preferred because they are reliably transmitted even on unshielded cables. This allows for very robust and reliable signal transmission over existing cables using simple means. On the other hand, it is preferred that the readout signals only have frequencies that are sufficiently above the mains frequency of 50 Hz.

[0024] All readout frequencies preferably assume only discrete values. These values ​​are preferably dichroic with respect to one another. A set of frequencies is referred to as dichroic in this document if none of the frequencies is a multiple of any other frequency and if the difference or sum of any two frequencies does not correspond to any of the other frequencies. This prevents harmonics and / or nonlinear effects from confusing a combination of two readout frequencies with another readout frequency. The readout frequency values ​​can, in particular, correspond to the frequencies of the well-known DTMF tone dialing system in telephony, as defined in ITU-T Standard Q.23 (11 / 88). These frequencies are 697, 770, 852, 941, 1209, 1336, 1477, and 1633 Hz.

[0025] The device for determining the operating status can comprise one or more end position testers. An end position tester indicates whether the switch has reached one of its end positions (left or right end position). An end position tester can, for example, have a mechanical switch, an inductive sensor or an optoelectric sensor. The end position tester can, for example, be directly assigned to a switch tongue and arranged in such a way that it indicates whether the switch tongue in question is correctly positioned on the corresponding stock rail. For this purpose, the end position tester can be arranged, for example, on the relevant tongue, on the corresponding stock rail or on the switch lock for the relevant tongue. If the end position tester is directly assigned to a switch tongue, the end position tester determines the absolute position of the switch. The end position tester can also be arranged in the switch drive and detect the end position of the switch relative to the switch drive.

[0026] In some embodiments, the device for determining the operating state can have a first end position tester for detecting a first end position of the switch, and a second end position tester for detecting a second end position of the switch. The readout signal generator can then be configured to generate a readout signal with a readout frequency that assumes at least a first value when the first end position tester indicates that the switch is in the first end position, and to generate a readout signal with a readout frequency that assumes at least a second value when the second end position tester indicates that the switch is in the second end position.

[0027] In the simplest case, the readout frequency assumes a first constant value in the first end position and a second constant value in the second end position, with these values ​​being different. Alternatively, the readout frequency can also vary in each of the two end positions according to a temporal sequence of two or more different values, with at least one of these values ​​differing between the two end positions. It is also conceivable for the readout signal in each of the two end positions to represent a superposition of two or more oscillations with a corresponding number of readout frequencies, with the value of at least one readout frequency differing between the two end positions.

[0028] The device may further comprise an evaluation device designed to be arranged remotely from the switch, in particular in a signal box. The evaluation device may comprise: a second coupling device for coupling the readout signal coupled into the line by the first coupling device out of the line; and an analysis device configured to perform a spectral analysis of the coupled-out readout signal and, depending on a result of the spectral analysis of the readout signal, to generate an output signal representing the operating state of the switch.

[0029] The analysis device can be constructed in a conventional manner using analog and / or digital hardware. In a simple embodiment, the analysis device comprises a plurality of narrowband filters to isolate the spectral components at the discrete values ​​of the readout frequencies used by the readout signal generator from the extracted readout signal, as well as an amplitude measuring device to determine the amplitude of the respective spectral component at each of these values. In other embodiments, the analysis device can, for example, have an ADC to digitize (sample) the extracted readout signal, and it can have a digital signal processor to analyze the digitized readout signal using known digital signal processing methods such as FFT or DFT, in order to determine a frequency spectrum of the readout signal.

[0030] The analysis device generates at least one output signal based on the performed spectral analysis. For example, the analysis device can be configured to generate an output signal with a first value representing a first end position of the switch if the extracted readout signal has a first readout frequency pattern, and to generate an output signal with a second value representing a second end position of the switch if the extracted readout signal has a second readout frequency pattern. In the simplest case, the first and second readout frequency patterns can each consist of a single readout frequency whose value differs between the first and second end positions.The analysis device can also be configured to generate an output signal with a third value that represents a state in which the switch is neither in the left nor the right end position if the extracted readout signal contains neither the first nor the second readout frequency pattern. The output signal can be output, for example, as a digital value or it can be output, for example, optically.

[0031] At train stations, a large number of points are often operated from a common interlocking system. From the interlocking system, the cables are bundled for several points in a main cable to remote cable distributors, from where individual four-wire cables are routed as spur cables to the individual points. Due to the bundling in the main cable, electromagnetic crosstalk can occur between lines belonging to different points. From a safety perspective, it is of great importance to ensure that the extracted readout signals are reliably assigned to the corresponding point. For this purpose, the evaluation device can have an interrogation signal generator designed to generate an interrogation signal. The second coupling device can then be designed to couple the interrogation signal into the line, and the first coupling device can be designed accordingly to extract the interrogation signal from the line.The readout signal generator can be configured to receive the extracted interrogation signal and modify the readout signal depending on the extracted interrogation signal. In this way, it can be ensured, in the sense of a "challenge-response" scheme, that the signal analyzed in the analysis device actually originates from the associated switch and not from another switch.

[0032] The interrogation signal can, similar to the readout signal, be an AC signal with at least one interrogation frequency.

[0033] In a simple embodiment, the readout signal generator can, for example, be designed such that it only outputs a readout signal to the first coupling device when it receives an interrogation signal with a predetermined frequency value.

[0034] However, more complex embodiments are also possible which further reduce the risk of incorrect assignment between the evaluation device and the switch. In preferred embodiments, the interrogation signal generator is designed such that it changes the interrogation frequency according to a sequence of at least two different values, i.e. the interrogation signal has a time-varying interrogation frequency pattern. The readout signal generator can then be designed to change the value of the readout frequency depending on the value of the interrogation frequency. For example, the readout signal generator can be designed to generate the readout signal at an assigned value of the readout frequency for each value of the interrogation frequency. In this way, a readout frequency pattern is created whose rhythm corresponds to the interrogation frequency pattern and which follows the interrogation frequency pattern with a slight time delay.

[0035] The sequence of polling frequency values ​​can be pseudorandomly timed. The polling signal generator can have a random generator that determines a pseudorandom period within specified limits, after which the polling signal generator switches to the next polling frequency value. However, the timing can also be predefined, which differs from switch to switch.

[0036] The timing timescale, i.e., the period from one change in the query frequency to the next, is preferably in the range of approximately 20 ms to 500 ms. The minimum period to be selected depends in particular on the values ​​used for the query and readout frequencies; these periods are advantageously at least five times, and preferably at least ten times, the inverse of the smallest frequency value used to enable reliable detection of the frequencies used.

[0037] To further reduce the risk of crosstalk between lines belonging to different switches, the interrogation signal generator can be configured to transmit the interrogation signal to the second coupling device only for a predetermined period of time, e.g., for 2 to 10 seconds, after each switchover of the switch. After that, it can no longer transmit an interrogation signal to the second coupling device until the next switchover of the switch. Accordingly, the readout signal generator can be configured to transmit the readout signal to the first coupling device only as long as it is receiving an interrogation signal. This ensures that AC signals are only transmitted over the line for a very limited period of time, and crosstalk to other lines outside of this period is avoided.

[0038] The present invention further provides a method for monitoring the operating state of a switch, which is defined by claim 11.

[0039] All of the above statements regarding the device of the present invention apply equally to the method of the present invention. In particular, all of the above-mentioned method steps for which the device of the present invention is designed can actually be carried out within the scope of the method of the present invention.

[0040] In particular, the readout frequency preferably lies in a low-frequency range between 100 Hz and 50 kHz. The readout frequency preferably assumes only discrete values ​​that are dichroic to each other.

[0041] The method may in particular comprise the following steps: Extracting the readout signal coupled into the line from the line in an evaluation device arranged remotely from the switch; performing a spectral analysis of the extracted readout signal; and generating an output signal depending on a result of the spectral analysis, wherein the output signal represents the operating state of the switch.

[0042] The procedure may include the following steps: Generating an interrogation signal in the evaluation device, wherein the interrogation signal can in particular be an AC signal with a variable interrogation frequency pattern; coupling the interrogation signal into the line at the evaluation device; coupling the interrogation signal out of the line; and changing the readout signal depending on the coupled interrogation signal.

[0043] The interrogation signal can be an AC signal with at least one interrogation frequency. The interrogation frequency can be varied according to a sequence of at least two different values. The sequence can, in particular, be pseudorandomly timed. The value of the readout frequency can be varied depending on the value of the interrogation frequency. It is conceivable to couple the interrogation signal and the resulting readout signal into the line only during a predetermined period after a switch has been switched. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Preferred embodiments of the invention are described below with reference to the drawings, which are for illustrative purposes only and are not to be construed as limiting. In the drawings: Fig. 1 a schematic representation of a switch in its left end position; Fig. 2 a schematic representation of a switch in its right end position; Fig. 3 a schematic circuit diagram of a four-wire interface with the associated switch drive in the left end position; Fig. 4 a schematic circuit diagram of a four-wire interface with the associated switch drive in the right end position; Fig. 5 a device for monitoring the operating state of a switch according to a first embodiment in the left end position of the switch; Fig. 6 the device according to Figure 5in the right end position of the switch; Fig. 7 the signal box part of a device for monitoring the operating status of a switch according to a second embodiment; Fig. 8 the switch-side part of the device for monitoring the operating status of a switch according to the second embodiment; and Fig. 9 a schematic diagram illustrating the interrogation frequencies and the associated readout frequencies during operation of the device according to the Figures 7 and 8 . DESCRIPTION OF PREFERRED EMBODIMENTS

[0045] In the Figures 1 and 2 A switch 1 is illustrated in a highly schematic manner. The switch drive 2 is located on the left side of the switch in the direction of travel F. The two switch tongues are moved between a left and a right end position of the switch via a push rod 3. In the Figure 1 the switch is shown in the left end position L, in which Figure 2 in the right end position R.

[0046] The Figures 3 and 4 illustrate a four-wire interface with an associated switch drive. The four-wire interface has four connectors, X1, X2, X3, and X4. In practice, the wires of an electrical cable are connected to it. Conceptually, the wires then form the connectors X1, X2, X3, and X4.

[0047] The point machine has a three-phase drive motor with motor windings L1, L2, and L3. A first end of motor winding L1 is connected to terminal X1 of the four-wire interface, a first end of motor winding L2 is connected to terminal X2, and a first end of motor winding L3 is connected to terminal X3. The second end of motor winding X1 is alternately connected to terminal X4 or to the second end of motor winding L3 via a first end position contact m1 that acts as a changeover switch. The second end of motor winding L2 is alternately connected to terminal X4 or to the second end of motor winding L3 via a second end position contact m2 that also acts as a changeover switch.

[0048] The end position contacts are "make before break" type switches, i.e. when the respective end position contact switches, it first briefly connects its three terminals to each other in an intermediate state.

[0049] In the Figure 3 the end position contacts are in a position corresponding to the left end position L of the switch. In this position, terminal X1 of the four-wire interface is connected to terminal X3 via motor winding L1, the first end position contact m1, and the motor winding L3, and terminal X2 is connected to terminal X4 via motor winding L2 and the second end position contact m2.

[0050] In switching mode, a three-phase current with a suitable phase position is applied to terminals X1 to X4. This causes the drive motor to switch the switch from the left to the right end position. Switching mode is of secondary importance for the present invention and will therefore not be discussed in detail.

[0051] In traditional monitoring operation, a DC monitoring voltage is applied to terminals X2 and X3 to monitor the left end position, and the resulting current through terminal X3 and the voltage between terminals X1 and X4 are measured. When the switch is in the left end position, the measured voltage between terminals X1 and X4 essentially corresponds to the monitoring voltage, and the measured current is very low. If the left end position has not been reached or the switch has been opened, the second end position contact m2 is in a different position. In this case, the measured voltage between terminals X1 and X4 is zero, and the measured current is significantly increased.

[0052] In the Figure 4the end position contacts are in a position corresponding to the right end position R of the switch. In this position, terminal X1 of the four-wire interface is connected to terminal X4 via motor winding L1 and the first end position contact m1, and terminal X2 is connected to terminal X3 via motor winding L2, the second end position contact m2, and the motor winding L3.

[0053] In traditional monitoring operation, a DC monitoring voltage is applied to terminals X1 and X3 to monitor the right end position, and the resulting current through terminal X3 and the voltage between terminals X2 and X4 are measured. When the switch is in the right end position, the measured voltage between terminals X2 and X4 essentially corresponds to the monitoring voltage, and the measured current is very low. If the right end position has not been reached or the switch has been opened, the first end position contact m1 is in a different position. In this case, the measured voltage between terminals X2 and X4 is zero, and the measured current is significantly increased.

[0054] As is readily apparent from the above explanations, interchanging connections X1 and X2 results in the left end position being mistaken for the right end position in traditional monitoring mode, and vice versa. This can lead to serious accidents during operation.

[0055] The present invention provides a monitoring device that makes it possible to correctly detect the position of the switch even if the connections X1 and X2 are swapped.

[0056] In the Figure 4is illustrated in a highly schematic form how such a monitoring device can be connected to the four-wire interface in such a way that it can draw its power requirements directly from the interface in traditional monitoring operation. For this purpose, a readout signal generator 20 of the monitoring device, described in more detail below, is connected to the terminals X1, X2, and X3 of the four-wire interface by means of diodes D1, D2 in such a way that the monitoring voltage is available as the supply voltage to the readout signal generator 20 in both the left and right end positions. The readout signal generator 20 contains a protective circuit that switches off the readout signal generator 20 and protects it from overvoltage when a three-phase alternating voltage is applied to the terminals X1 to X4.The readout signal generator 20 interacts with a device 10, described in more detail below, for determining the operating state of the switch 1 and a coupling device 30, also described in more detail below, which is inserted into the line to the connection X3.

[0057] The Figures 5 and 6illustrate, in highly schematic form, a first embodiment of a monitoring device. In this embodiment, the device 10 for determining the operating state has a first end position tester 11 and a second end position tester 12. The end position testers 11, 12 are completely independent of the end position contacts m1, m2 of the point drive. Each end position tester 11, 12 interacts directly with a tongue of the point 1. It is closed when the respective tongue is in contact with the associated stock rail, and it is open when the corresponding tongue is away from the associated stock rail. The end position testers can be, for example, mechanical contacts, inductive sensors, or optoelectric sensors.

[0058] In the Figure 5 The left end position is shown. The first end position checker 11 is open, and the second end position checker 12 is closed. Figure 6The right end position is shown. Now the first end position checker 11 is closed, and the second end position checker 12 is open.

[0059] In this embodiment, the readout signal generator 20 comprises two separate tone generators 21 and 22. The first tone generator 21 generates a readout signal in the form of an electrical AC signal with a first fixed frequency precisely when the first end position tester 11 is closed. The second tone generator 22 generates a readout signal with a second fixed frequency precisely when the second end position tester 12 is closed. The first and second frequencies are dichroic to each other in the sense defined above.

[0060] The respective readout signal is sent to the aforementioned coupling device 30. The coupling device 30 couples the readout signal into the wire of line 4 connected to terminal X3 of the four-wire interface. This transmits the readout signal to the interlocking system. For example, the coupling device 30 can comprise a transformer that simultaneously provides galvanic isolation between line 4 and the output of the readout signal generator 20.

[0061] An evaluation device (not shown) in the interlocking system monitors line 4 and analyses whether a readout signal has been received and, if so, at what frequency. If the evaluation device detects a readout signal at the first frequency, it emits an output signal with a first value, meaning that the switch is in the left end position. If the evaluation device detects a readout signal at the second frequency, it emits an output signal with a second value, meaning that the switch is in the right end position. If the evaluation device does not detect a readout signal, it emits an output signal with a third value, meaning that the switch is neither in the left nor the right end position or there is a fault.

[0062] In the embodiment described above, the readout signal generator 20 generates a readout signal for each end position with a readout frequency that assumes a fixed value. Instead of a fixed frequency value, the readout signal generator 20 can also generate a more complex frequency pattern in each of the two end positions. For example, the readout signal generator 20 can also generate a simultaneous superposition or temporal sequence of two or more dichroic frequencies in each end position. It is also conceivable for the readout signal generator to generate a readout signal even when both the first end position tester 11 and the second end position tester 12 are open, in order to be able to distinguish this operating state from a malfunction.

[0063] The readout signal generator 20 can, of course, be constructed differently than shown. For example, instead of two separate tone generators 21, 22, the readout signal generator 20 can comprise a single analog or digital signal generator whose frequency can be varied according to the positions of the end-of-travel detectors 11 and 12.

[0064] In the Figures 7 and 8 A second embodiment of a monitoring device is illustrated in a highly schematic form. Figure 7 the signal box part of the monitoring device, while the Figure 8 the parts arranged on the switch represent a monitoring device.

[0065] The interlocking system contains a control circuit 5 and a monitoring circuit 6. An isolating relay 8 alternately connects control circuit 5 or monitoring circuit 6 to the interlocking terminals X1-X4 of a four-wire interface. In changeover mode, control circuit 5 applies a three-phase alternating voltage to these terminals, with the phase position depending on the desired changeover direction. In monitoring mode, monitoring circuit 6 applies a monitoring voltage to two of the four terminals of the four-wire interface and measures the resulting current and the voltage at the other two terminals, as described in more detail above.

[0066] Additionally, an evaluation device 40 of the monitoring device is arranged in the interlocking system. The evaluation device 40 comprises a second coupling device 50, an analysis device 60, a query signal generator 70, and a control computer 80. The control computer 80 controls the control circuit 5, the monitoring circuit 6, and the isolating relay 8. The control computer 80 also controls the analysis device 60 and the query signal generator 70.

[0067] The second coupling device 50 decouples the readout signal coupled in at the switch from the line 4 and forwards the decoupled readout signal to the analysis device 60.

[0068] The analysis device 60 performs a spectral analysis of the extracted readout signal. In the present embodiment, it comprises several frequency analyzers FR3 to FR10. Each frequency analyzer monitors whether the extracted readout signal contains an oscillation of a specific frequency. In particular, the frequency analyzer FR3 monitors whether the extracted readout signal contains an oscillation of the frequency f3, the frequency analyzer FR4 monitors whether the extracted readout signal contains an oscillation of the frequency f4, etc. For this purpose, each frequency analyzer can contain a narrowband filter at the corresponding frequency and a circuit for determining the amplitude of the oscillation at this frequency. Based on the spectral analysis performed, the analysis device 60 generates an output signal with a specific value, which value represents a specific operating state of the switch.

[0069] The interrogation signal generator 70 generates an interrogation signal. The interrogation signal is an AC signal whose frequency (the "interrogation frequency") alternates between two values ​​f1 and f2 according to a pseudorandom sequence. For this purpose, the interrogation signal generator 70 in the present embodiment has two tone generators FG1 and FG2, with the tone generator FG1 generating an interrogation signal with frequency f1 and the tone generator FG2 generating an interrogation signal with frequency f2. The control computer 80 controls the two tone generators FG1 and FG2 so that they are activated alternately. For this purpose, the control computer 80 has a random number generator. Based on random numbers generated by the random number generator, the control computer determines pseudorandom times at which switching between the tone generators FG1 and FG2 occurs.

[0070] In the Figure 9A corresponding interrogation signal A is illustrated as an example. During a period ta the value of the interrogation frequency is f2, during the subsequent period tb this value is f1, and during the subsequent period tc this value is f2 again. The interrogation signal A interrupts as soon as the switchover occurs from monitor mode to changeover mode. In this example the switchover now takes place from the left to the right end position. The switchover then takes place back to monitor mode and the interrogation signal generator starts to send out an interrogation signal again. In this example the value of the interrogation frequency is f2 again during the period td, during the subsequent period te this value is f2, etc. The length of the periods ta, tb, tc, td, te, etc. varies within certain limits, e.g. between 50 ms and 500 ms, according to a pseudo-random pattern.

[0071] With the help of the second coupling device 50, the query signal A is coupled into line 4 of the four-wire interface between the signal box and the switch drive. With the help of the first coupling device 30, the query signal is decoupled from line 4 at the switch (see Fig. 8 )

[0072] In the present example, the readout signal generator 20 has two narrowband frequency analyzers FR1 and FR2, which determine whether an interrogation signal with frequency f1 or f2 has been transmitted. If an interrogation signal with frequency f1 has been transmitted, the corresponding frequency analyzer FR1 activates two tone generators FG3 and FG5. If, however, an interrogation signal with frequency f2 has been transmitted, the corresponding frequency analyzer FR2 activates two tone generators FG4 and FG6. If the left end position tester 11 indicates that the switch is in the left end position, the output of the tone generators FG3 and FG4 is connected to the first coupling device 30. If, however, the right end position tester 12 indicates that the switch is in the right end position, the output of the tone generators FG5 and FG6 is connected to the first coupling device 30.

[0073] As in the Figure 9As illustrated by way of example, a readout signal S is generated by the readout signal generator 20 and coupled into line 4 by the first coupling device 30 whenever the interrogation signal generator 70 transmits an interrogation signal A. Due to the signal propagation times, the readout signal S follows the interrogation signal A with a slight delay Δt. The readout signal S has a variable readout frequency that alternates between two values ​​at the same rhythm as the interrogation frequency. In the left end position of the switch, these are the values ​​f3 and f4; in the right end position, these are the values ​​f5 and f6.

[0074] Overall, the readout signal generator 20 generates a readout signal S that clearly correlates with the interrogation signal A generated by the interrogation signal generator 70. This allows a reliable association between the evaluation device 40 in the interlocking system and the associated readout signal generator 20 at the switch to be established, even if there is a risk that signals from readout signal generators with the same frequency from other switches will be coupled into line 4 due to crosstalk.

[0075] In order to prevent crosstalk of the interrogation signals A and readout signals S to other monitoring devices via the supply line of the monitoring circuit 6, a low-pass filter 7 is arranged in the DC voltage supply of the monitoring circuit 6.

[0076] To further reduce the risk of crosstalk, after each switch change (so-called switch cycle), the query signal A is transmitted for a limited period of time only and then switched off. Accordingly, the readout signal S is also transmitted for a limited period of time only. Based on this, the response signal is generated and evaluated. If the response signal indicates the correct position of the switch, the route is released. After that, no more AC signals are sent over the line until the next switch cycle, thus eliminating the risk of crosstalk to other lines. Further monitoring of the switch position is then carried out exclusively via traditional DC monitoring mode.

[0077] Typically, one switch cycle lasts a few seconds, e.g., 5 seconds. The interrogation signal can then also be transmitted for a few seconds, e.g., 2 to 10 seconds, preferably 3 to 5 seconds. During this period, the interrogation frequency changes its value several times, e.g., five to twenty times. This is sufficient to clearly identify the frequency pattern of the interrogation frequency and the resulting pattern of the readout frequency, and to correlate these frequency patterns with each other.

[0078] For some types of turnouts, especially long high-speed turnouts, more than one end position detector may be provided for each end position. For example, two end position detectors 11, 13 may be provided along the turnout for the left end position, and two end position detectors 12, 14 may also be provided for the right end position (see Fig. 8). In this case, the readout signal generator 20 can easily be expanded with additional tone generators FG7, FG8, FG9, FG10 to monitor the switching states of the additional end position testers 13 and 14. These tone generators emit readout signals with their own readout frequencies, which are assigned to these end position testers and differ from the readout frequencies f3, f4, f5, and f6 of the tone generators FG3, FG4, FG5, and FG6. Such additional end position testers can also be used to monitor the position of the switch frog, if this is also movable.

[0079] Of course, the readout signal generator 20 can also be constructed differently than described above. In particular, the readout signal generator 20 can comprise a digital signal processor that generates the readout signals at the frequencies mentioned under program control.

[0080] If the monitoring circuit 6 is operated in a pulsed mode, the monitoring device according to the present invention is preferably also operated in a correspondingly pulsed mode. This is particularly the case when the readout signal generator 20 draws its power from the monitoring circuit 6 via the four-wire interface.

[0081] Of course, a large number of modifications to the present embodiments are possible without departing from the scope of the invention. In particular, the readout signal generator 20, the analysis device 60, and the interrogation signal generator 70 can also be constructed in a manner other than that described above. Any elements with at least two switching states can be used as end position testers, provided that the switching states can be influenced by the position of the switch. In addition to the end positions, further parameters of the switch can be checked in the same way if necessary. For example, further switching elements can interact with the readout signal generator, whereby these switching elements are arranged such that they clearly detect the approach of the switch. LIST OF REFERENCE SYMBOLS

[0082] 1 Switch 80 Tax calculator 2 Switch drive 3 push rod A query signal 4 Line AC alternating voltage 5 Control circuit DC DC voltage 6 Supervisory circle D1, D2 diode 7 Low-pass filter f1, f2 Query frequency 8 Isolating relay f3-f10 Readout frequency 10 Operating status determination FG1-FG10 Transmitter module 11-14 Limit switch FR1-FR10 Receiver module 20 Readout signal generator F Direction of travel 21 first signal generator L left end position 22 second signal generator L1-L3 Motor winding 30 first coupling device m1, m2 Switch 40 Evaluation device R right end position 50 second coupling device S Readout signal 60 Analysis device X1-X4 Connections 70 Interrogation signal generator

Claims

1. A device for monitoring the operating state of a turnout (1), comprising: an operating state determination device (10) for determining the operating state of the turnout (1); a readout signal generator (20) which cooperates with the operating state determination device (10) and is configured to generate a readout signal (S), the readout signal (S) being an AC signal with at least one readout frequency; and a first coupling device (30) for coupling the readout signal (S) generated by the readout signal generator (20) into an electrical line (4) between a turnout drive (2) of the turnout (1) and a signal box, characterised in that the readout signal generator (20) is configured to generate the readout signal (S) in such a way that the readout frequency assumes a value (f3, f4, f5, f6) that depends on the determined operating state of the turnout (1), so that the frequency content of the readout signal indicates the operating state of the turnout.

2. The device according to claim 1, wherein the operating state determination device (10) is configured to be arranged on the turnout (1) independently of the turnout drive (2).

3. The device according to claim 1 or 2, wherein the readout frequency is in a frequency range between 100 Hz and 50 kHz.

4. The device according to any one of the preceding claims, wherein the readout frequency assumes exclusively discrete values (f3, f4, f5, f6) which are dichroic to one another.

5. The device according to any one of the preceding claims, wherein the operating state determination device (10) comprises a first end position detector (11) for detecting a first end position (L) of the turnout (1), wherein the operating state determination device (10) comprises a second end position detector (12) for detecting a second end position (R) of the turnout (1), wherein the readout frequency assumes at least one first value (f3, f4) when the first end position detector (11) indicates that the turnout (1) is in the first end position (L), and wherein the readout frequency assumes at least one second value (f5, f6) when the second end position detector (12) indicates that the turnout (1) is in the second end position (R).

6. The device according to any one of the preceding claims, further comprising an evaluation device (40), wherein the evaluation device (40) is configured to be arranged remotely from the turnout (1), and wherein the evaluation device (40) comprises: a second coupling device (50) for outcoupling the readout signal (S), which was coupled into the line (4) by the first coupling device (30), from the line (4); and an analysis device (60) configured to carry out a spectral analysis of the outcoupled readout signal (S) and, depending on a result of the spectral analysis of the readout signal, to generate an output signal representing the operating state of the turnout (1).

7. The device according to claim 6, wherein the evaluation device (40) further comprises a query signal generator (70) which is configured to generate a query signal (A), wherein the second coupling device (50) is configured to couple the query signal (A) into the line (4), wherein the first coupling device (30) is configured to outcouple the query signal (A) from the line (4), wherein the readout signal generator (20) is configured to receive the outcoupled query signal (A) and to change the readout signal (S) as a function of the outcoupled query signal (A).

8. The device according to claim 7, wherein the query signal (A) is an AC signal with at least one query frequency.

9. The device according to claim 8, wherein the query signal generator (70) is configured to change the query frequency in accordance with a sequence of at least two different values (f1, f2), wherein the sequence may in particular be clocked pseudo-randomly, and wherein the readout signal generator (20) is configured to change the value of the readout frequency (f3, f4, f5, f6) as a function of the value of the query frequency (f1, f2).

10. The device according to any one of the preceding claims, wherein the device is configured to be operated at a four-wire interface for the turnout drive (2), wherein the readout signal generator (20) is preferably configured in such a way that it draws its supply voltage via the four-wire interface when the turnout drive (2) is operated via the four-wire interface in monitoring mode.

11. A method for monitoring the operating state of a turnout (1), comprising the steps: determining the operating status of the turnout (1); generating a readout signal, wherein the readout signal (S) is an AC signal with at least one readout frequency; and coupling the readout signal (S) into at least one electrical line (4) between a turnout drive (2) of the turnout (1) and a signal box, characterised in that the readout frequency assumes a value (f3, f4, f5, f6) which depends on the determined operating state of the turnout (1), so that the frequency content of the readout signal indicates the operating state of the turnout.

12. The method according to claim 11, wherein the readout frequency lies in a frequency range between 100 Hz and 50 kHz and / or wherein the readout frequency assumes discrete values which are dichroic to one another.

13. The method according to claim 11 or 12, comprising the steps of: outcoupling of the readout signal (S), which was coupled into the line (4), from the line (4) in an evaluation device (40) arranged remotely from the switch (1); performing a spectral analysis of the outcoupled readout signal (S); and generating an output signal as a function of a result of the spectral analysis, the output signal representing the operating state of the switch (1).

14. The method according to any one of claims 11 to 13, comprising the steps of: generating a query signal (A) in the evaluation device (40); coupling the query signal (A) into the line (4) at the evaluation device (40); outcoupling the query signal (A) from the line (4); and changing the readout signal (S) depending on the outcoupled query signal (A).

15. The method according to claim 14, wherein the query signal (A) is an AC signal with at least one query frequency, wherein the query frequency is changed according to a sequence of at least two different values (f1, f2), wherein the sequence may in particular be clocked pseudo-randomly, and whereby the value of the readout frequency (f3, f4, f5, f6) is changed depending on the value (f1, f2) of the query frequency.