EP3617114A1 - Method and monitoring device for monitoring a safety chain circuit in a lift system - Google Patents

Abstract

A method and a monitoring device (31) for monitoring a safety chain circuit (2) in an elevator installation (1) are described. The safety chain circuit (2) has a plurality of safety switches (17) interconnected with one another and at least one tap connection (41). An electrical voltage is applied between end regions of the safety chain circuit (2). The method comprises measuring a current electrical voltage between the tap connection (41) and a reference connection (43). The reference connection (43) is either another one of the tap connections (41) or a connection (45) held at a predetermined voltage level. The current electrical voltage is measured such that at least three, but preferably significantly more, different voltage levels can be distinguished. The safety chain circuit (2) is then monitored taking into account the measured current electrical voltage. For example, excessive changes in the measured voltage that occur over time can indicate wear in components of the safety chain circuit (2). With the approach described here, the integrity of a safety chain circuit (2) can be monitored and, for example, signs of wear and tear in safety switches (17) can be recognized at an early stage, so that maintenance measures can be planned in good time and failures of the elevator system (1) can be avoided.

Description

The present invention relates to a method and a monitoring device for monitoring a safety chain circuit in an elevator system.

Elevator systems are used, for example, to vertically transport people within buildings between different floors. In order to be able to guarantee the safety of people, certain safety-critical operating conditions within the elevator system must be continuously monitored. For example, it must be ensured that an elevator car is only moved when its elevator door and an adjacent floor door are completely closed and therefore no one can be in the door area. In addition, it should be ensured that the elevator car does not move faster than a predetermined speed limit, that the elevator car does not move outside a travel range provided for this purpose, that no emergency switch of the elevator system has been actuated, etc.

In order to be able to monitor the individual safety-critical operating conditions, a switch can be provided that changes its switching state, for example, in the event of excessive changes in the monitored operating condition. The switch can be equipped with a sensor that switches the switching state of the switch depending on the operating condition to be monitored.

For example, door switches can be provided as safety switches in the elevator installation, which monitor a closed state of the elevator door or a storey door and which, for example, are only in their closed switching state when the door is completely closed. Other types of safety switches can monitor other safety-related operating conditions in the elevator system.

The multiple safety switches are typically electrically connected to one another. The safety switches can be connected to one another in series or in some cases in parallel. Since the safety within the elevator installation is to be monitored with the aid of such a circuit and at least some of the safety switches are connected in series in the manner of a chain, such a circuit is referred to herein as a safety chain circuit. An electrical voltage is typically applied between ends of such a safety chain circuit, so that monitoring of the electrical voltage can be used to identify whether the safety chain circuit has been interrupted at any point.

In general, operation of the elevator system and in particular moving of the elevator car are only permitted if the safety chain circuit is continuously closed, i.e. is not interrupted at any point. For example, depending on the switching state of the safety chain circuit, a main power supply to the elevator system can be established or interrupted, so that a power supply to a drive of the elevator system is reliably interrupted when the safety chain circuit changes to its open state.

For example, door switches can be provided on all doors of the elevator system and can be connected to one another in series as part of the safety chain circuit. In this case, the safety chain circuit is only closed when all door switches are closed. Accordingly, the elevator car can only be moved if all doors of the elevator system are closed. Similarly, the safety chain circuit can only be closed if an emergency switch integrated in it has not been opened by actuation, a switch monitoring the speed of the elevator car has not been opened when an overspeed occurs, etc.

In order to be able to allow certain desired operating states or operating modes, it can be provided that individual ones of the safety switches can be bridged temporarily and taking into account high safety requirements. For example, during an inspection of the elevator system, it may be necessary to be able to move the elevator car even when the elevator doors are open. For example, it may also be desirable to be able to slightly adjust a level of the elevator car when the elevator doors are open, after this level changes, for example, when passengers enter the elevator car or when passengers leave the elevator cabin, since without such a level compensation, referred to as "relevant", there is a step formation at the transition between a floor of the elevator car and the floor of the adjacent floor would come. Furthermore, it may also be desirable to start opening the doors of the elevator system shortly before the elevator car actually reaches a destination floor, for example in order to enable faster entry and exit from the cabin. To enable such special functions, it may be necessary to construct the safety chain circuit in a more complex manner in order, for example, to temporarily enable bridging of individual circuit segments of the safety chain circuit.

With conventional safety chain circuits, it can thus be ensured that the elevator system is only operated in safe operating states or in safe operating conditions. It is monitored whether the safety chain circuit is continuous, i.e. all safety switches connected in series are closed or whether the safety chain circuit is interrupted, i.e. at least one of the safety switches is open.

However, cases are conceivable in which the safety chain circuit is interrupted, even though no condition that actually jeopardizes the safety of the elevator system is present. Similar to the dangerous conditions that are actually present, the operation of the elevator system is also interrupted in this case of a “false alarm”. On the one hand, this can cause inconvenience for the passengers of the elevator installation. On the other hand, this may make it necessary to check and / or to maintain the elevator system, for example by a technician visiting the elevator system and examining the safety chain circuit to find out why it was interrupted.

Among other things, there may be a need for a method and a device by means of which the reliability and / or functionality of a safety chain circuit in an elevator system can be improved, in particular in that unnecessary interruptions in the operation of the elevator system and / or unnecessary checks by the elevator system Technicians largely can be avoided. There may also be a need for an elevator installation with such a device, for a computer program product for executing or controlling such a method and / or for a computer-readable medium with such a computer program product stored thereon.

Such a need can be met by the subject matter according to one of the independent claims. Advantageous embodiments are defined in the dependent claims and the description below.

According to a first aspect of the invention, a method for monitoring a safety chain circuit in an elevator installation is proposed. The safety chain circuit has a plurality of safety switches connected to one another and at least one tap connection. An electrical voltage is applied between end regions of the safety chain circuit. The method comprises measuring a current electrical voltage between the tap connection and a reference connection. The reference connection is a different one of the tapping connections or a connection held at a predetermined voltage level. The current electrical voltage is measured in such a way that at least three different voltage levels can be distinguished. The safety chain circuit is then monitored taking into account the measured current electrical voltage.

According to a second aspect of the invention, a monitoring device for monitoring a safety chain circuit in an elevator system is proposed. The safety chain circuit has a plurality of safety switches which are connected to one another and a plurality of tap connections which are connected between serially adjacent safety switches. The monitoring device is configured to execute or control the method according to an embodiment of the first aspect of the invention.

According to a third aspect of the invention, an elevator installation with a monitoring device according to an embodiment of the second aspect of the invention is proposed.

According to a fourth aspect of the invention, a computer program product is proposed which contains computer-readable instructions which, when executed by a processor, instruct the processor to execute or to control a method according to an embodiment of the first aspect of the invention.

According to a fifth aspect of the invention, a computer-readable medium with a computer program product stored thereon according to an embodiment of the fourth aspect of the invention is proposed.

Possible features and advantages of embodiments of the invention can, inter alia and without restricting the invention, be viewed as based on the ideas and knowledge described below.

As already indicated in the introduction, a safety chain circuit can be interrupted in elevator systems, although there is actually no safety-critical state in the elevator system. In addition to opening safety switches, other circumstances can also lead to the safety chain circuit being interrupted.

For example, switch contacts within a safety switch can oxidize over time, so that the safety switch no longer switches reliably. In particular, such oxidized switch contacts can be mechanically connected to one another in a closed state of the safety switch, but can nevertheless not establish an electrical connection.

It must be taken into account here that many of the safety switches included in a safety chain circuit are normally always closed and are only opened in exceptional or emergency cases. This applies, for example, to safety switches for monitoring overspeed, safety equipment, a buffer and / or an emergency stop switch. Other safety switches such as door contact switches are opened and closed regularly. Both operating modes can have a wear-promoting effect under certain conditions.

Alternatively, breaks or interruptions in a wiring of the safety chain circuit can lead to an interruption of the same. In particular, wires, connections, plugs, terminals or the like can break, for example due to wear.

The aim is therefore not only to be able to monitor the current switching state of the safety chain circuit, but also its integrity. In particular, the aim is to be able to recognize at an early stage whether the safety chain circuit is damaged, for example, by wear. For example, damage within the safety chain circuit should be recognized, which can lead to interruptions in the safety chain circuit and thus to false alarms.

In order to achieve this, it is proposed not only to monitor whether the safety chain circuit is currently closed or open, but also to additionally monitor how intrinsic properties of the safety chain circuit behave.

To summarize briefly, an electrical voltage is to be measured along the security chain circuit or partial areas thereof in order to be able to draw conclusions about the intrinsic properties of the security chain circuit.

Conventionally, one or more tap connections are provided on a safety chain circuit. An electrical voltage is applied to end regions of the safety chain circuit. A tap connection is used to be able to tap the electrical voltage prevailing at a specific position along the safety chain circuit.

For example, a tap connection at an end region of the safety chain circuit can be used to check whether the applied electrical voltage is short-circuited along the entire safety chain circuit, from which it can be deduced that the safety chain circuit is continuously closed.

If necessary, tap connections can be provided on the safety chain circuit at several different positions. In this way it can be detected, for example, at which point an interruption in the safety chain circuit occurred.

However, in the conventional monitoring of a safety chain circuit, it is only checked whether the voltage present at a tap connection is above or below a limit value, in order to be able to conclude from this whether the safety chain circuit is open or closed. In other words, when measuring the voltage at a tap connection, only two different voltage levels are distinguished.

In contrast to this, in the method proposed here, a current electrical voltage at a tap connection is to be measured such that at least three different voltage levels can be distinguished. Preferably four, five, at least ten, at least 20 or even at least 50 different voltage levels can be distinguished. If necessary, voltage levels can be continuous or quasi-continuous within a voltage interval, i.e. with negligibly small voltage differences between neighboring voltage values.

By measuring the voltage present at a tap connection with a large number of possible voltage levels, it is not only possible to differentiate whether the safety chain circuit is currently open or closed, but can also be used to draw conclusions as to which intrinsic properties prevail within the safety chain circuit, since these often affect an electrical resistance through the safety chain circuit and thus influence the voltage applied to the tap connection. For example, signs of corrosion on safety switches can lead to increased electrical resistances by the safety switches and thus cause local voltage drops within the safety chain circuit.

In particular, according to one embodiment, the safety chain circuit can take into account changes in the measured current electrical voltage be monitored over time.

In other words, the voltage applied to a tap connection can be measured continuously or periodically over time, and changes in this electrical voltage can be used to infer changes in the safety chain circuit.

In contrast to conventional voltage measurements, in which only changes in voltage from a level on this side of a threshold to a level beyond the threshold are recognized and an opening or closing of the safety chain circuit can be concluded therefrom, the fact that there are more than two voltage levels differentiates here voltage changes can be observed, which occur over time, while the safety chain circuit remains closed.

For example, from changes in voltage that occur while the voltage is still in a range on this side or beyond the threshold value, conclusions can be drawn about the intrinsic properties of the safety chain circuit to be monitored. In principle, the more voltage levels that can be distinguished here, the more precisely changes in the measured current electrical voltage can be detected and the more precisely changes in the intrinsic properties of the safety chain circuit can be inferred.

For example, according to one embodiment of the invention, the electrical voltage can be measured at the beginning of a monitoring process and stored as the initial value. During the monitoring process, the current electrical voltage can then be measured and compared with the initial value.

In other words, the electrical voltage present at a tap connection can be measured, for example, directly after a safety chain circuit has been installed, ie in its new state. This measured initial value can be stored as a reference value, for example in a data memory provided in the elevator installation itself or also in an external data memory. During the subsequent monitoring process, the currently prevailing electrical one Voltage can be tapped continuously or at regular time intervals at the tap connection, and the measured value measured in the process is compared with the stored initial value. Any intrinsic properties of the safety chain circuit to be monitored can be inferred from any differences between the two values. If, for example, such differences exceed a predetermined amount, it can be assumed that wear phenomena have occurred within the safety chain circuit, which at least require maintenance, possibly also repair or replacement, of components of the safety chain circuit.

According to one embodiment of the invention, the voltage is measured as a digital measured value with several bits and analyzed for monitoring the safety chain circuit.

In other words, the voltage should not only be measured and analyzed as a binary measured value with two levels, ie "ON" or "OFF" or "1" or "0". Such a binary measured value could be reproduced digitally with a single bit. Instead, the voltage should be reproduced and analyzed digitally by a measured value with several bits. A multitude of voltage levels can be reproduced with the multiple bits. For example, up to 2 ⁿ voltage levels can be represented with n bits (n = 2, 3, 4, ...). The more bits the measured value comprises, the more voltage levels can be distinguished and the more precisely the voltage levels can be measured and analyzed. The electrical voltage can, for example, be measured analogously and then converted into the digital measured value using an analog-digital converter.

According to one embodiment, the safety chain circuit can be subdivided into a plurality of serially connected segments and a tap connection can be provided in each case between adjacent segments. The method can then include measuring a current electrical voltage between a tap terminal adjacent to the segment and a reference terminal for each of the segments.

In other words, the entire safety chain circuit can be composed of several segments. For example, a single segment can be Monitoring of a single function can be provided within the elevator installation. One or more safety switches can be integrated in each segment. The segments can be interconnected in series. A tap connection can be provided between serially adjacent segments. The safety chain circuit thus has a plurality of tap connections, the number of tap connections generally corresponding to the number of segments minus 1.

By measuring the electrical voltage present at one of the tap connections with respect to a reference connection, not only information about the integrity of the safety chain circuit as a whole, but also information about an integrity of the segment of the safety chain circuit adjacent to the respective tap connection can be derived. Such more detailed information can help, for example, a maintenance technician to find defective or weary components within a safety chain circuit.

According to one embodiment of the invention, the current electrical voltage can be measured between the tap connection and a connection held at a fixed, predetermined voltage level.

In other words, a connection can be provided for the safety chain circuit which is specifically kept at a certain fixed voltage level. This voltage level can correspond, for example, to the level of electrical grounding. The voltage present at the tap connection can then be measured relative to the voltage level which is predetermined at the connection. Such a measuring arrangement is easy to implement and / or can make statements about absolute voltage values and / or changes in absolute voltage values at one or more tap connections.

Alternatively, according to one embodiment of the invention, the current electrical voltage between the tap connection and a tap connection serially adjacent to the tap connection can be measured.

In other words, in the event that the safety chain circuit is divided into several segments and several tap connections are provided, the current one electrical voltage can be measured between a tap connection and an adjacent tap connection. For example, the electrical voltage can be measured between two tap connections delimiting a segment. It can be irrelevant which absolute voltages are present at the two tap connections. Instead, only a difference between these two absolute voltages is measured. This allows conclusions to be drawn about a voltage drop in the partial region of the safety chain circuit lying between the two tap connections, ie for example a voltage drop within one of the segments of the safety chain circuit. This can allow a statement about the intrinsic integrity within this sub-area or segment. This in turn can provide valuable information to a maintenance technician, for example.

According to a further alternative embodiment of the invention, in addition to the voltage measurement, a current electrical current strength can be measured through a segment of the safety chain circuit which is delimited by the tap connection. A current electrical resistance through the segment can then be calculated from the measured current electrical voltage and the measured current electrical current strength. The safety chain circuit can thus be monitored taking into account the calculated current electrical resistance.

In other words, not only the voltage applied to a tap connection, but also the current strength flowing through a segment of the safety daisy-chain circuit delimited by the tap connection can be measured. An electrical resistance along the relevant segment can then be calculated on the basis of these two measured values.

Measuring only the voltage present at the tap connection can be influenced in that, for example, the electrical voltage applied to the end regions of the safety chain circuit can vary for various reasons. Such variations in the electrical voltage applied from the outside can possibly lead to misinterpretations of the voltage measured at the tap connection. However, if the current strength is also measured in addition, such variations in the externally applied electrical voltage can have no influence remain because the electrical resistance calculated from this is independent of the voltage applied from outside through a segment. Monitoring of the safety chain circuit can thus be made even more reliable.

An embodiment of the monitoring device according to the second aspect of the invention can have as components at least one voltage source, at least one voltage measuring device and an analysis device. The voltage source is configured to generate an electrical voltage between end regions of the safety chain circuit. The voltage measuring device is configured to measure the current electrical voltage between one of the tap connections and a reference connection. The analysis device is configured to analyze the measured current electrical voltage and to generate a monitoring signal depending on a result of the analysis.

The voltage source can be, for example, a power supply unit or a battery. The voltage source can generate a DC voltage or an AC voltage. The voltage source can generate the voltage constant over time.

The voltage measuring device can be a voltmeter. The voltage measuring device can be electrically connected between a tap connection and a reference connection, in particular it can be hard-wired. In particular, the voltage measuring device can be connected between a tap connection and a connection held at a fixed electrical potential, for example a grounded connection. Alternatively, the voltage measuring device can be connected between two tap connections adjacent along the safety chain circuit. The voltage measuring device can measure the voltage analogously and then digitize it if necessary. Alternatively, the voltage measuring device can measure the voltage digitally. Digital measurement values can include several bits.

The analysis device can analyze the voltages measured by the voltage device, for example, in such a way that changes over time and / or changes relative to a reference value, in particular relative to an initial value, can be detected.

In addition to the components mentioned, the monitoring device can comprise further components. For example, a current measuring device can be used to measure the current through segments of the safety chain circuit in order to be able to derive electrical resistances therefrom. Furthermore, a signal generation device and / or a signal transmission device can be used to generate monitoring signals and / or to transmit them to other devices based on information derived from the analysis device. The monitoring signals can provide information directly or after suitable processing as to whether significant changes, in particular wear-related changes, have been detected in the safety chain circuit which, for example, make maintenance or repair appear necessary. The monitoring signals can be transmitted, for example, to an elevator control provided in the elevator installation and / or to an elevator monitoring center which is remote from the elevator installation.

The monitoring device can be designed to be programmable. In particular, the monitoring device can be configured as part of a programmable elevator control. Accordingly, the monitoring device can be enabled by suitable hardware, suitable software or a combination of hardware and software to carry out or control embodiments of the monitoring method described herein. The software can be designed as a computer program product with computer-readable instructions, which, when executed on a processor of the monitoring device, instruct the processor to carry out or control method steps of the monitoring method described. The computer program product can be formulated in any computer language. The computer program product can be stored on any computer-readable medium such as, for example, a flash memory, a CD, a DVD, a ROM or another non-volatile storage medium. Alternatively, the computer program product can be stored on a computer, in particular a server or a cloud, from where it can be downloaded via a network, for example the Internet.

It is noted that some of the possible features and advantages of the invention herein, with respect to different embodiments, partially limit the Monitoring method and partially the monitoring device are described. A person skilled in the art recognizes that the features can be combined, transmitted, adapted or exchanged in a suitable manner in order to arrive at further embodiments of the invention.

Embodiments of the invention are described below with reference to the accompanying drawings, wherein neither the drawings nor the description are to be interpreted as limiting the invention.

Fig. 1 shows an elevator system with a monitoring device according to an embodiment of the present invention.

Fig. 2 shows a safety chain circuit which is monitored by means of a method according to an embodiment of the present invention.

The figures are only schematic and are not to scale. The same reference numerals in the different figures designate the same or equivalent features.

Fig. 1 shows an elevator installation 1 with a monitoring device 31 according to an embodiment of the present invention.

The elevator installation 1 comprises an elevator car 5 and a counterweight 7, which can be held with suspension means 9 in the form of belts and can be displaced vertically within an elevator shaft 3 by the suspension means 9 being driven by a drive machine 11. The drive machine 11 is controlled by an elevator control 13. A power supply from a power source 15 to the drive machine 11 can be established or interrupted using a main switch 39.

A safety chain circuit 2 is provided in the elevator installation 1. The safety chain circuit 2 comprises a multiplicity of safety switches 17 which are arranged distributed over the elevator installation 1 and which states or conditions can determine within the elevator system 1 and then change their switching state.

For example, door contact switches 19 can monitor a closed state of shaft doors 21 on different floors 33. A position monitoring switch 23 can, for example, monitor whether a ladder 25 is correctly positioned within the elevator shaft 3 and thus, for example, does not protrude into a travel path of the elevator car 5. Another door contact switch 29 can monitor a closed state of a car door 27.

The safety switches 17 can be at least partially connected in series and connected to the monitoring device 31, for example, via a wiring 35. In the monitoring device 31, electrical voltages can be processed by the safety chain circuit 2 and possibly other signals, for example the safety switch 17, using an analysis device 37. Based on the results of the analysis device 37, the monitoring device 31 can then influence a switching state of the main switch 39.

Fig. 2 illustrates a safety chain circuit 2 and a monitoring device 31 for monitoring the safety chain circuit 2.

Several safety switches 17 are connected in series in the safety chain circuit 2. For example, the position monitoring switch 23, an end limit switch, an emergency stop switch, an overspeed switch, a plurality of door contact switches 19 on shaft doors and a door contact switch 29 on the cabin door can be connected in series.

A bridging circuit 55 can be provided in order to be able to temporarily bridge areas of the safety chain circuit 31.

For example, door zone switches 57 can be used to detect when the elevator car 5 is in the vicinity of a final stop position on one of the floors 33 and can then temporarily bridge the area of the safety chain circuit 2 that includes the door contact switches 19, 29. This can be a Level compensation ("releveling") and / or premature opening of the shaft and cabin doors 21, 27 are made possible.

An electrical voltage is applied between end regions of the safety chain circuit 2 with the aid of a voltage source 47. The voltage source 47 can generate a voltage that is preferably constant over time in relation to a ground potential at a ground connection 45. The safety chain circuit 2 is protected with the aid of a fuse 51.

As long as the safety chain circuit 2 is completely closed, the main switch 39 is also kept in the closed state, so that a power supply can be established between the elevator control 13 and the drive machine 11 with a motor 59 integrated therein and an activatable brake 61. As soon as the safety chain circuit 2 is interrupted by opening one of its safety switches 17, the main switch 39 is also opened and the power supply to the drive machine 11 is interrupted, so that the motor 59 can no longer generate mechanical power and the brake 61 is automatically activated.

Similar types of safety switches 17 or safety switches 17, which are intended to monitor similar functions or conditions within the elevator installation 1, can form segments 63 of safety switches 17 connected directly in series.

At least one tap connection 41 is provided on the safety chain circuit 2, at which an electrical voltage present locally on the safety chain circuit 2 can be tapped. In the example shown, 63 tap connections 41 are provided between adjacent segments.

The monitoring device 31 has a plurality of voltage measuring devices 49, by means of which a currently applied electrical voltage can be measured between a tap connection 41 and a reference connection 43.

In the example shown, a tap connection 41 is provided between two adjacent segments 63, on which one of the voltage measuring devices 49 has one local electrical voltage can tap. In the example shown, the reference connection 43 is also connected to the ground connection 45, so that it is kept at a fixed electrical potential. Alternatively, however, an adjacent tap connection 41 can also serve as a reference connection 43.

The voltage measuring device 49 is designed to distinguish at least three, but preferably significantly more, different voltage levels in the measured current electrical voltage. For example, the voltage measuring device 49 can be designed with a voltmeter whose analog measured values are converted into digital measured values with several bits by means of an analog digital converter.

The voltages or voltage levels measured by the voltage measuring devices 49 can be analyzed in the analysis device 37. Depending on the measured voltages, the analysis device 37 can generate a monitoring signal. This monitoring signal can be transmitted, for example, to the elevator control 13 and / or an external elevator monitoring center.

The analysis device 37 can, in particular, monitor changes in the measured current electrical voltages over time. For this purpose, for example, at the beginning of a monitoring process, that is to say, for example, immediately after installation of the elevator installation 1, an electrical voltage applied to one of the tap connections 41 can be measured and stored as an initial value. At a later point in time during the monitoring process, an then actually measured electrical voltage at the tap connection 41 can be compared with the initial value. If these two voltage values differ excessively, this can be interpreted as an indication that electrical properties within the safety chain circuit 2 have changed significantly. This can in turn be viewed as an indicator that wear has occurred within the safety chain circuit 2, which could make maintenance or repair necessary, for example. The analysis device 37 can then generate a corresponding monitoring signal.

In order to make monitoring of the safety chain circuit 2 even more robust, the monitoring device 31 can also have a current measuring device 53. This current measuring device 53 can for example be connected in series as an ammeter in the safety chain circuit 2. If both a voltage or a voltage drop across one of the segments 63 of the safety chain circuit 2 and the current intensity flowing through this segment 63 are known, an electrical resistance can be calculated through this segment 63. Changes in this electrical resistance can serve as a robust indicator of signs of wear, for example on safety switches 17 in this segment 63.

In summary, embodiments of the present invention can make it possible to recognize not only a switching state but also, for example, wear-related changes in a safety chain circuit 2 of an elevator system 1.

In the case of conventional safety chain circuits 2, for example, oxidation processes which can occur over time in safety switches 17 were not monitored. The elevator system 1 was operated accordingly until such oxidation processes became critical and, for example, the safety chain circuit 2 was interrupted. The operation of elevator system 1 was then interrupted. Passengers could be locked in the cabin and a maintenance technician might have to service the elevator as soon as possible.

To avoid this, it is proposed here to monitor the intrinsic state of the safety chain circuit 2 by measuring electrical voltages at tap connections 41 and checking them for changes. As a result, oxidation processes on safety switches 17, terminals or wiring can be recognized. If these become critical, this can be communicated to a maintenance technician early on, for example. The maintenance technician can thus, for example, check the integrity of its safety chain circuit 2 when he next visits the elevator system 1 before failures actually occur. Failures of the elevator system 1 and in particular blocking of passengers can thus be avoided. In addition, unnecessary and / or urgent visits to the maintenance technician can be avoided.

Since microcontrollers which are already designed to measure electrical voltages with analog inputs are mostly already used in today's elevator controls, embodiments of the method proposed here can usually be implemented without considerable technical outlay, in particular without expensive additional hardware. In some cases it may be sufficient to change the controller software only.

Accordingly, the operator of an elevator can save considerable costs for maintenance measures without having to significantly increase the costs for the elevator installation 1.

In conclusion, it should be pointed out that terms such as "having", "comprehensive", etc. do not exclude other elements or steps, and terms such as "a" or "an" do not exclude a large number. Furthermore, it should be pointed out that features or steps which have been described with reference to one of the above exemplary embodiments can also be used in combination with other features or steps of other exemplary embodiments described above. Reference signs in the claims are not to be viewed as a restriction.

Reference list

1

Elevator system

2

Safety chain circuit

3

Elevator shaft

5

Elevator cabin

7

Counterweight

9

Suspension means

11

Prime mover

13

Elevator control

15

Power source

17

Safety switch

19

Door contact switch of a landing door

21

Landing door

23

Position monitoring switch

25

ladder

27

Cabin door

29

Door contact switch of a cabin door

31

Monitoring device

33

floor

35

wiring

37

Analysis device

39

Main switch

41

Tap connections

43

Reference connection

45

Earth connection

47

Voltage source

49

Voltage measuring device

51

fuse

53

Current measuring device

55

Bypass circuit

57

Door zone switch

59

engine

61

brake

63

segment

Claims (13)

Method for monitoring a safety chain circuit (2) in an elevator system (1), the safety chain circuit (2) having a plurality of safety switches (17) interconnected with one another and at least one tap connection (41), and an electrical voltage being applied between end regions of the safety chain circuit (2) ,
the method comprising measuring a current electrical voltage between the tap connection (41) and a reference connection (43),
wherein the reference connection (43) is a connection selected from the group comprising another one of the tap connections (41) and a connection (45) held at a predetermined voltage level,
the current electrical voltage being measured such that at least three different voltage levels can be distinguished,
wherein the safety chain circuit (2) is monitored taking into account the measured current electrical voltage. The method of claim 1, wherein the safety chain circuit (2) is monitored taking into account changes in the measured current electrical voltage over time. Method according to one of the preceding claims, wherein at the beginning of a monitoring process the electrical voltage is measured and stored as an initial value and during the monitoring process the current electrical voltage is measured and compared with the initial value. Method according to one of the preceding claims, wherein the voltage is measured as a digital measured value with a plurality of bits and is analyzed to monitor the safety chain circuit (2). Method according to one of the preceding claims, wherein the safety chain circuit (2) is subdivided into a plurality of serially connected segments (63) and wherein a tap connection (41) is provided in each case between serially adjacent segments (63),
the method for each of the segments (63) comprising measuring a current electrical voltage between a tap connection (41) adjacent to the segment (63) and a reference connection (43). Method according to one of the preceding claims, wherein the current electrical voltage between the tap connection (41) and a connection (45) held at a predetermined voltage level is measured. Method according to one of claims 1 to 5, wherein the current electrical voltage between the tap connection (41) and a tap connection (41) serially adjacent to the tap connection (41) is measured. Method according to one of claims 1 to 5, wherein in addition a current electrical current strength is measured by a segment (63) of the safety chain circuit (2) delimited by the tap connection (41), the current electrical voltage and the current electrical current being measured current electrical resistance is calculated by the segment and the safety chain circuit (2) is monitored taking into account the calculated current electrical resistance. Monitoring device (31) for monitoring a safety chain circuit (2) in an elevator system (1),
The safety chain circuit (2) has a plurality of interconnected safety switches (17) and a plurality of tap connections (41) connected between serially adjacent safety switches (17),
wherein the monitoring device (31) is configured to execute or control the method according to one of claims 1 to 8. Monitoring device according to claim 9, comprising: a voltage source (47) for generating an electrical voltage between end regions of the safety chain circuit (2), at least one voltage measuring device (49) for measuring the current electrical voltage between one of the tap connections (41) and a reference connection (43), and an analysis device (37) for analyzing the measured current electrical voltage and for generating a monitoring signal depending on a result of the analysis. Elevator system (1) with a monitoring device (31) according to one of Claims 9 and 10. Computer program product which contains computer-readable instructions which, when executed by a processor, instruct the processor to carry out or to control a method according to one of claims 1 to 8. Computer-readable medium with a computer program product stored thereon according to claim 12.

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