EP2760774B1 - Device and method for monitoring shaft doors - Google Patents

Description

The invention relates to an apparatus and a method for monitoring shaft doors of an elevator installation.

Shaft door monitoring is used to ensure the safety of persons in the elevator system.

An elevator installation usually has an elevator shaft with a plurality of shaft doors and an elevator car which can be moved in the elevator shaft. Each shaft door is secured by a locking device. For the purpose of detection of an unlocking a shaft door contact is arranged on the locking device. The shaft door contacts of several shaft doors are connected in series in a closed circuit and form part of a safety circuit. The closed circuit is supplied with a basic voltage. When unlocking one of the shaft doors, which is not due to a customary user-related use of the elevator car, this safety circuit is interrupted by the associated shaft door contact. After such unlocking it must be assumed that a person is in the elevator shaft outside the elevator car. For example, this can be caused by a manual unlocking of the shaft door but also by a malfunction of the locking device. One embodiment of a lift installation according to the prior art is out WO9947447 A1 known.
Regardless of a subsequent re-locking an operating mode of the elevator system is adjusted. Path or speed limits are adopted in a driving pattern of the elevator car. This ensures that a person who is possibly on the elevator car or at the bottom of the elevator shaft has enough space. Instead, the elevator system can also be temporarily shut down. In both cases, a service technician then has to make sure on site that no person is in the elevator shaft outside the elevator car. Only then can he return the elevator system to an operating mode that corresponds to normal operation.

The problem with such an approach that the device for monitoring the shaft doors in a prolonged power failure, in which the Basic voltage in the safety circuit can not be maintained by a battery that is "blind". As a precaution, after a prolonged power failure, it must always be assumed that a person is in the shaft, although it is also possible that none of the shaft doors were unlocked during the power failure. Thus, in any case, a service specialist must be on site when the power supply is ensured again and the elevator system can be put back into normal operation.

The object of the invention is therefore to provide an apparatus and a method for monitoring shaft doors, which allow monitoring of the shaft doors during power outages.

The object is achieved by an elevator installation with at least one shaft door and a control device for monitoring movements for opening the shaft door, comprising a first energy self-sufficient counting device for counting the movements, which increments independently of an intact power supply in the case of one of these movements a first count, and a second counting means for counting the movements, which in case of one of these movements, when the power supply is intact, increments a second count and a comparison circuit which fetches and compares the first and second counts and generates a signal based on the comparison of the counts.

The object is further achieved by a method for monitoring movements for opening the shaft door, after which the comparison circuit sends request signals to the first counting and storage circuit and to the second counting and storage circuit, so that a transmission of the assigned count values to the comparison circuit is triggered , and the first count value is transmitted to the comparison circuit, and the second count value is transmitted to the comparison circuit, and by means of an algorithm of the comparison circuit, the first is compared with the second count value.

The invention is based on the finding that an elevator system expires in a dead state during a prolonged power failure. This occurs when additional power storage has been discharged during the power interruption itself, which are provided for the bridging of power interruptions. During the tensionless Condition, the shaft doors of the elevator system can not be monitored. As a result, access control in the elevator shaft is to some extent blind. After such a prolonged power interruption before recommissioning of the elevator system must therefore be assumed that opened a manhole door during the dead state, a person has entered the elevator shaft, and was closed again. In order to ensure the safety of this person, a service specialist on site must check the elevator shaft before recommissioning. Only then can the elevator system be released again for normal operation. In view of the fact that only in very few cases during this review is there actually a person in the elevator shaft, such an approach is unnecessarily costly. This includes both arrival and departure of the service technician as well as corresponding delays in the re-commissioning of the elevator system.

In order to minimize the resulting expenses, it was therefore attempted to change the monitoring for the shaft door so that even in the event of a pending restart after a de-energized state can be determined beyond doubt whether the shaft door was opened. This is achieved by a control device with two counting devices. One of these counters detects and stores a count corresponding to a number of movements to open the shaft door when the power supply is intact. Another counter detects and stores a count corresponding to a number of the same movements of the hoistway door, both intact and failed. If a comparison of these two counts results after a longer power interruption when the power supply is intact again, it can be concluded that the shaft door was not opened during the power failure. However, if these two counts are different, assume that the shaft door has been opened. In this case, the presence of the service technician on the elevator system for recommissioning is required. A further advantage is that with a recurring comparison of the two counts even during normal operation, a malfunction of the counting devices can be detected on the basis of different counts. Another advantage is the ability to monitor shaft doors or groups of shaft doors separately. This is useful, for example, in elevator systems with a high number of shaft doors, in order to be able to find a single shaft door, which has one Malfunction has. In addition, a malfunction of individual counting devices can be detected.

In a further development of the elevator installation, the energy self-sufficient counter device in each case has a shaft door associated sensor arrangement comprising a permanent magnet and an induction unit, wherein both the permanent magnet and the induction unit are arranged on the shaft door, that by a change in the relative position of the permanent magnet Induction unit, a voltage pulse is induced which increments the first count value as it moves to open the landing door. An embodiment of the sensor arrangement in this way has the advantage that the count of the first count value is non-mechanical, ie wear-free.

In a further development of the elevator installation, the permanent magnet is arranged on a first part of the shaft door and the induction unit is arranged on a second part of the shaft door, wherein the first part and the second part execute a relative movement relative to one another during the movement. It is advantageous that the induction unit and the permanent magnet of the sensor arrangement are arranged at a plurality of locations on the shaft door. In this way, the equipment of the shaft door with the sensor arrangement can be significantly simplified.

In addition, the self-powered counter may comprise a non-volatile first counting and storage circuit in which the first count is stored, which can be activated and operated by the voltage pulse from a de-energized state, and the voltage pulse in the movement to open the hoistway door first count is that increments the first count. It is thus possible to use energy from the movements for opening and closing the shaft door, yet to detect and count the movements for opening the shaft door by means of a selection circuit.

In addition, the induction unit may be formed of a ferromagnetic element, preferably a Wiegand wire or a pulse wire, and an induction coil. In this way, it is possible that the voltage pulse is sufficiently rich in energy to enable the counting and storage of the first count energy self-sufficient. potential Problems that can occur due to the detection of low-energy voltage pulses can thus be prevented.

In a further development of the elevator installation, the second counting device comprises a non-volatile second counting and storage circuit. In this way, the second count value can be stored beyond a period of the failed power supply.

In a further development of the elevator installation, the first counting pulse with intact power supply increments the second counting value. Thus, a single detecting device in the form of the sensor arrangement can generate a count which can increment both the first count and the second count. A difference between the two counts results from the fact that the second count value is incremented only when the power supply is intact and the first count value is independent of the power supply. For example, expenses for installing further detecting devices on the shaft door can be saved.

In a further development of the elevator installation, the second counting device comprises a circuit which is closed in a closed position of the shaft door and which can be interrupted by the movement at a contact point, and a voltage detector which bridges the circuit and in the event of an interruption of the circuit when the power supply is intact causes the second count to be incremented. It is advantageous that an existing circuit at the shaft door can be used to increment the second count. This circuit can be subjected to an intact power supply with a basic voltage. This ensures that the second count value can only be incremented when the power supply is intact. The second counting device may comprise a non-volatile second counting and storage circuit, the voltage detector, when a voltage threshold is exceeded, generating a second counting pulse which increments the second counting value stored in the second counting and storing circuit. Thus, a potential difference across the pad can be used to increment the count of the second counter.

In a further development of the elevator installation, the shaft door comprises a locking device with two mutually movable parts, and the movement for opening the Shaft door is an unlocking process. It is advantageous that already the unlocking process of the shaft door can be used to detect the possible imminent opening of the shaft door.

In a further development of the method, the first count value is associated with a first time and the second count value with a second time, wherein the shaft door between the first and the second time is always closed. Thus, the first and second counts can be compared with each other without necessarily having these counts retrieved at the same time. Nevertheless, in normal operation, an equal value for the first and the second count would be expected.

In a development of the method, the comparison circuit generates a mismatch signal upon detection of a mismatch between the first and second count values. It is advantageous that the mismatch signal can be used to initiate further steps, for example the call of a service person or a check routine.

A period of "intact power supply" also includes a period of time during which the power supply of the control device is maintained by power storage devices arranged in the elevator installation. The period of the intact power supply is followed by a period of the dead state or the failed power supply. Power interruption, however, means that the power supply of the elevator system, which is provided for example by a power utility, is not in operation. Thus, from a period of power interruption and the period is included, in which the power supply of the control device is maintained by power storage.

Figur 1:

eine Aufzugsanlage mit mehreren Schachttüren;

Figur 2:

einen Ausschnitt einer Schachttür der Aufzugsanlage;

Figur 3:

eine erste Zählvorrichtung zur Zählung von Bewegungen zur Öffnung der Schachttür;

Figur 4:

eine Verriegelungseinrichtung der Aufzugsanlage mit einer ersten und einer zweiten Zählvorrichtung;

Figur 5:

eine beispielhafte Sensoranordnung der erwähnten zweiten Zählvorrichtung; und

Figur 6:

ein Schema einer erfindungsgemässen Kontrollvorrichtung

In the following the invention will be explained in more detail with reference to figures. Show it:

FIG. 1:

an elevator system with several shaft doors;

FIG. 2:

a section of a shaft door of the elevator system;

FIG. 3:

a first counting device for counting movements for opening the shaft door;

FIG. 4:

a locking device of the elevator installation with a first and a second counting device;

FIG. 5:

an exemplary sensor arrangement of said second counting device; and

FIG. 6:

a diagram of a control device according to the invention

FIG. 1 shows an elevator system 2. The elevator system 2 comprises a lift shaft 8 and a plurality of shaft doors 4a, 4b, 4c and a lift control, not shown. In the elevator shaft 8, an elevator car 6 can be moved along the elevator shaft 8 by means of a drive arrangement, not shown. In this case, the elevator car 6 executes a travel movement 14. The elevator shaft 8 can also include a floor area 12 and a head area 10 into which the elevator car 6 can not penetrate for safety reasons. Exemplary parts of this drive arrangement are a drive machine, a support element and deflection pulleys.

In an operating mode of the elevator installation 2 which corresponds to normal operation, the elevator cage 6 can be moved in the elevator shaft 8 in such a way that persons can enter and leave the elevator cage 6 through the shaft doors 4a, 4b, 4c. Shown is in FIG. 1 a position of the elevator car 6, which permits entry or exit of the elevator car 6 through the shaft door 4b. If a person gets into the elevator shaft 8, for example to the elevator car 6 through the shaft door 4a, or under the elevator car 6 through the shaft door 4c, it must be ensured that this person is not injured. "Boarding" in the elevator shaft 8 means that the person does not enter the elevator car 6 through the shaft door 4a, 4c, but enters the elevator shaft 8 outside the elevator car 6. This boarding is registered by the elevator control. Consequently, the elevator control can cause the operating mode of the elevator installation 2 to be changed. Thus, the floor area 12 and the head area 10 may be present, which in turn constitute safety areas into which the elevator car 6 can not penetrate. In order to be able to minimize dimensions of the elevator shaft 8, a driving pattern of the elevator car 6 can be adapted in the case of the changed operating mode. For example, a maximum speed of the travel movement 14 can be reduced or the security areas can be arranged such that the elevator car 6 can no longer reach positions in the elevator shaft 8 that would have to be reached for entering the elevator car 6 through the uppermost landing door 4a or the lowermost landing door 4c , A shift back the elevator installation 2 in the operating mode, which corresponds to normal operation can only after a review of the elevator system 2 on site by a service person to be completed.

In the FIGS. 2 to 6 At least parts of various embodiments of a control device according to the invention are shown.

FIG. 2 shows a section of a shaft door 4 of an elevator system. The shaft door 4 has a door frame 20 and a shaft door leaf 22, which can be opened by means of a shaft door opening movement O and then closed again by means of a shaft door closing movement S. The shaft door opening movement O is a movement for opening the shaft door 4. The shaft door closing movement S is a movement for closing the shaft door 4. The door frame 20 and the shaft door leaf 22 are mutually movable parts which at least in the shaft door opening movement O perform a relative movement to each other. The shaft door 4 is shown in a closed state. Shown are two parts 24a, 24b of a circuit 24. One of these parts 24a, 24b may be on the landing door leaf 22, a second corresponding part 24a, 24b may be disposed on the door frame 20. The circuit 24 also includes a contact point 26, the parts 24 a, 24 b of the circuit 24 conductively connects in the closed state of the shaft door 4. The circuit 24 is supplied with an intact power supply with a basic voltage. Once a shaft door opening movement O begins, the circuit 24 is interrupted at the contact point 26. This can be detected and monitored via a drop in the basic voltage. Instead of monitoring a single shaft door 4 of the elevator installation with such a circuit 24, a group of shaft doors, that is to say at least two shaft doors 4a, 4b, 4c, shown in FIG FIG. 1 to be integrated in circuit 24. For this purpose, the shaft doors 4a, 4b, 4c may be provided with such a contact point 26. The contact points 26 of the respective landing doors 4a, 4b, 4c can then be connected in series within the circuit 24. In the case of a shaft door opening movement O of one of the shaft doors 4a, 4b, 4c, the electric circuit 24 is interrupted and this shaft door opening movement O is detected. The in FIG. 2 explained circuit may be part of a counting device 30.

FIG. 3 shows a counting device 30 for counting movements to open a shaft door. The counting device 30 comprises a circuit 24, a voltage detector 32 and a non-volatile counting and storage circuit 34. The circuit comprises at least one contact point 26. The voltage detector 32 bridges the at least one contact point 26. The circuit 24 shown can be equal to the circuit as in FIG. 2 shown and described, be arranged. In the circuit 24 is a consumer 25, for example, a resistor disposed. An interruption at the contact point 26 causes a detected by means of the voltage detector 32 potential difference. A voltage threshold of the voltage detector 32 causes small voltage pulses acting on the voltage detector 32 not to generate a count pulse. Such small voltage pulses can certainly occur when the circuit 24 is closed, that is, when the contact points 26 are connected in a conductive manner. Only when the voltage threshold value is exceeded, that is, when at least one of the contact points 26 is interrupted, is the count pulse generated by the voltage detector 32. The count increments a count stored in the count and store circuit 34. Non-volatile is a memory unit of the count and store circuit 34 so that the incremented count remains stored even during a de-energized state.

FIG. 4 shows a locking device 40, a first self-powered counter 60 and a second counter 30 associated with a hoistway door 4. The locking device 40 has two mutually relatively movable parts 42, 44, wherein, for example, a movable first part 42 at an unlocking an unlocking movement E and a lock can perform a locking movement V. The locking device 40 is usually attached to a shaft door of the landing door 4, but may also be attached to other elements of the landing door 4. Components of the second counting device 30 are a circuit 24 having a contact point 26a, 26b, a voltage detector 32 associated with the circuit 24 and a non-volatile second counting and storage circuit 34. The circuit 24 is arranged on the mutually movable parts 42, 44, as already stated in the description of FIG. 2 is explained. The second counting device 30 may be constructed as described in the description FIG. 3 can be seen.

The unlocking E causes unlocking the shaft door leaf, so that the shaft door 4 thereafter usually can be opened. Accordingly, the unlocking movement E is a movement to open the shaft door 4. The unlocking movement E causes the circuit 24 is interrupted. Accordingly, unlocking operations the shaft door 4 counted with an intact power supply and stored by means of a count in a memory unit of the second counting and storage circuit 34.

Components of the first counting device 60 are a first non-volatile counting and storage circuit 64 and a sensor arrangement 50, which is arranged on the locking device 40. The sensor arrangement 50 comprises a permanent magnet 52 and an induction unit 54, for example a coil. The permanent magnet 52 is disposed on one of the two parts 42, 44 of the locking device 40. The induction unit 54 is arranged on the corresponding one of the two parts 42, 44 of the locking device 40. As well as contact points 26a, 26b of the second counting device 30 can be connected in series to monitor a plurality of shaft doors, also sensor assemblies 50 of the first counting device 60 can be connected in series. Both parts 52, 54 of the sensor arrangement 50 can be arranged so that a voltage pulse is induced in the unlocking movement E and in the locking movement V by the permanent magnet 52 in the induction unit 54. This voltage pulse can be declared at the onset of unlocking E by means of a selection circuit 62 as a first count. The first count pulse is used to increment a first count stored in a memory unit of the first counting and storage circuit 64. The energy of the voltage pulse is also used to activate and operate the first counting and storage circuit 64 from a de-energized state so as to allow incrementing of the first count value. This means that an energy input, which goes beyond a relative movement of the permanent magnet 52 to the induction unit 54, for counting the unlocking movement E and incrementing the first count within the first counting device 60 is not necessary. The first counting device 60 is energy self-sufficient.

The counters 30, 60 are disposed on at least one landing door such that when the power supply is intact, both counters 30, 60 have counts equal to when the counters 30, 60 are not malfunctioning. In addition to the unlocking movements E which the second counting device 30 registers with intact power supply and stores by means of the second counting value, the first counting device 60 registers and stores the unlocking movements by means of the first counting value E occurring during the dead state.

It is also possible that the described circuit 24 with the contact points 26a, 26b and the associated voltage detector 32 are not components of the second counting device 30 of the described embodiments. Accordingly, in addition to incrementing the first count within the first count and memory circuit 64, the first count generated by the sensor assembly 50 may be used to intact power supply to increment the second count of the second count and store circuit 34.

Such a sensor arrangement 50 of the energy self-sufficient counter 60 can also be used in addition to in FIG. 2 shown elements of the counting device 30 or according to the above, instead of these elements of the counting device 30 at the at least one landing door 4a, 4b, 4c of FIG. 2 be arranged to detect the shaft door opening movements O.

The sensor arrangement 50 or at least one of the counting devices 30, 60 can be connected by bus system to a comparison circuit of the control device according to the invention.

FIG. 5 shows an exemplary sensor arrangement 50 of the aforementioned energy self-sufficient first counting device. The sensor arrangement 50 comprises a permanent magnet 52, an induction unit 54 and a connection 59 to remaining components, not shown, of the energy self-sufficient first counting device. The induction unit 54 comprises a ferromagnetic element 56 and an induction coil 58. The permanent magnet 52 and the induction unit 54 are fixed to corresponding parts of a landing door, which can perform relative movements to each other. One of the relative movements is a movement to the opening O, E of the shaft door. A second of the relative movements may be a movement to close S, V of the shaft door. The ferromagnetic element 56 may be formed, for example, from a Wiegand wire or a pulse wire. The ferromagnetic element 56 is capable of assisting, upon approaching, increasing accumulation of energy in the magnetic field existing between it and the permanent magnet 52, this energy being diverted from the kinetic energy of the relative movements O, E, S, V. Reached the permanent magnet 52 with respect to the ferromagnetic element 56 a certain position and thus the prevailing in the ferromagnetic element 56 magnetic field strength of a certain size, so the accumulated energy is also when the approach is extremely slow, released suddenly. Such an abruptly changing magnetic field generates in the induction coil 58 a high-energy voltage pulse which is sufficient for incrementing a first count value stored in the energy-autonomous first counting device. Any arrangement of the permanent magnet 52 and the induction unit 54, preferably comprising the ferromagnetic element 56 and the induction coil 58, which allows the mentioned sufficiently high release of energy, is possible.

EP1550845 shows by way of example how an interconnection of a similar counting device can be performed.

FIG. 6 1 shows a diagram of a control device 80 according to the invention. The control device 80 comprises a first self-powered counter 60, a second counter 30 and a comparator 70. The first counter 60 comprises a first counter and memory circuit 64, the second counter 30 comprises a second counter and counter Memory circuit 34. Elements of the two counting devices 30, 60 are in the comments on the FIGS. 2 to 5 described and in FIG. 6 Not shown. Within the first counting device 60, a first count is stored, within the second counting device 30, a second count is stored.

• Die Vergleichsschaltung 70 sendet Anforderungssignale an die erste Zähl- und Speicherschaltung 64 und an die zweite Zähl- und Speicherschaltung 34, so dass eine Übermittlung der zugeordneten Zählwerte an die Vergleichsschaltung 70 ausgelöst wird.
• Der erste Zählwert wird an die Vergleichsschaltung 70 übermittelt.
• Der zweite Zählwert wird an die Vergleichsschaltung 70 übermittelt.
• Mittels eines Algorithmuses vergleicht die Vergleichsschaltung 70 den ersten Zählwert mit dem zweiten Zählwert.

A method for monitoring shaft doors consists of the following steps:

• The comparison circuit 70 sends request signals to the first counting and storage circuit 64 and to the second counting and storage circuit 34, so that a transmission of the associated count values to the comparison circuit 70 is triggered.
• The first count value is transmitted to the comparison circuit 70.
• The second count value is transmitted to the comparison circuit 70.
• By means of an algorithm, the comparison circuit 70 compares the first count value with the second count value.

A comparison of the two counts provides useful information about the state of the elevator system. Accordingly, a corresponding thereto, ie on the comparison of Count based signal X can be generated, which can be reused. If it results from the comparison of the two counts that they do not match, a mismatch signal can be generated. Accordingly, a defect of the control device 80 may be present or during a period of failure of the power supply, a movement to open the shaft door has been detected by the self-powered first counter 60. Since the control device 80 is provided as a safety-relevant device in the elevator installation, an alarm signal can be triggered and the elevator installation can be put into a corresponding operating mode. For example, this alarm signal can provide a prior check of the elevator installation by a service specialist as a prerequisite for further operation of the elevator installation in normal operation.

With an intact power supply, a transmission of request signals according to the mentioned method step can take place on the basis of a freely selectable retrieval plan, so that malfunctions of the first or second counting device 30, 60 can be detected when the power supply is intact.

The control device 80 can also comprise elements of an elevator control of an elevator installation. In these elements data are processed, which concern signals for opening doors of the elevator installation. Thus, for example, it can be determined to what extent a status of the first count corresponds to a status of the second count. A comparison of a first count with a second count, wherein the two counts represent a number of movements to open the landing door at different times, is allowed only if between a first time that can be assigned to the first count and a second time , which can be assigned to the second count, no detected by the control device 80 movement to open the shaft door is done.

Other not shown known electrical components and circuits may be part of the in the FIGS. 2 to 6 be shown control device to enable signal processing according to this document.

Claims (15)

1. Lift installation (2) with

   - at least one shaft door (4, 4a, 4b, 4c) and

   - a monitoring device (80) for monitoring movements (O, E) for opening the shaft door (4, 4a, 4b, 4c), characterised in that the monitoring device comprises:

   - a first, energy-autonomous counting device (60) for counting the movements (O, E), which independently of the intact power supply increment a first count value in the case of one of these movements (O, E), and

   - a second counting device (30) for counting the movements (O, E), which when the power supply is intact increments a second count value in the case of one of these movements (O, E), and

   - a comparison circuit (70) which calls up and compares the first and second count values and can generate a signal (X) based on the comparison of the count values.
2. Lift installation (2) according to claim 1, characterised in that the energy-autonomous counting device (60) comprises a respective sensor arrangement (50), which is associated with the shaft door (4, 4a, 4b, 4c) and which comprises a permanent magnet (52) and an induction unit (54), wherein both the permanent magnet (52) and the induction unit (54) are so arranged at the shaft door (4, 4a, 4b, 4c) that through a change in the relative position of the permanent magnet (52) with respect to the induction unit (54) a voltage pulse is induced which in the case of the movement for opening (O, E) the shaft door (4, 4a, 4b, 4c) increments the first count value.
3. Lift installation (2) according to claim 2, characterised in that the permanent magnet (52) is arranged on a first part (20) of the shaft door (4, 4a, 4b, 4c) and the induction unit (54) is arranged on a second part (22) of the shaft door (4, 4a, 4b, 4c), wherein the first part (20) and the second part (22) execute a movement relative to one another when the movement (O, E) takes place.
4. Lift installation (2) according to claim 2 or 3, characterised in that the energy-autonomous counting device (60) comprises a non-volatile first counting and memory circuit (64) in which the first count value is stored and which from a voltage-free state can be activated and operated by the voltage pulse, and the voltage pulse in the case of the movement (O, E) for opening of the shaft door (4, 4a, 4b, 4c) is a first count pulse which increments the first count value.
5. Lift installation (2) according to any one of claims 2 to 4, characterised in that the induction unit (54) is formed from a ferromagnetic element (56), preferably a Wiegand wire or a pulse wire, and an induction coil (58).
6. Lift installation (2) according to any one of the preceding claims, characterised in that the second counting device (10) comprises a non-volatile second counting and memory circuit (34).
7. Lift installation (2) according to any one of claims 4 to 6, characterised in that when the voltage supply is intact the first count pulse increments the second count value.
8. Lift installation (2) according to any one of claims 1 to 6, characterised in that the second counting device (30) comprises:

   - a current circuit (24),

   - which in a closed setting of the shaft door (4) is closed and

   - which can be interrupted at a contact point (26, 26a, 26b) by the movement (O, E) and

   - a voltage detector (32) which bridges the current circuit (24) and in the case of interruption of the current circuit (24) has the effect, when the power supply is intact, that the second count value is incremented.
9. Lift installation (2) according to claim 8, characterised in that the current circuit (24) is acted on by a basic voltage when the power supply is intact.
10. Lift installation (2) according to one of claims 8 and 9, characterised in that the voltage detector (32) when a voltage threshold value is exceeded generates a second count pulse which increments the second count value stored in the second counting and memory circuit (34).
11. Lift installation (2) according to any one of claims 8 to 10, characterised in that the shaft door (4, 4a, 4b, 4c) comprises a locking device (40) with two parts (42, 44), which are movable relative to one another and between which the contact point (26a, 26b) is arranged, and the movement (E) for opening the shaft door (4) is an unlocking process.
12. Method in a lift installation (2) for monitoring movements for opening the shaft door (4, 4a, 4b, 4c) according to any one of the preceding claims, characterised in that the comparison circuit (70) transmits demand signals to the first counting and memory circuit (64) and to the second counting and memory circuit (34) so that communication of the associated count values to the comparison circuit (70) is triggered and the first count value is communicated to the comparison circuit (70) and the second count value to the comparison circuit (70) and the first count value is compared with the second value by means of an algorithm of the comparison circuit (70).
13. Method according to claim 12, characterised in that a first time instant is associated with the first count value and a second time instant with the second count value, wherein the shaft door (4, 4a, 4b, 4c) is always closed between the first and second time instants.
14. Method according to one of claims 12 and 13, characterised in that the comparison circuit (70) generates a non-correspondence signal in the case of detection of non-correspondence of the first count value with the second count value.
15. Method according to claim 14, characterised in that the non-correspondence signal triggers an alarm signal.

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