EP2252537B1 - Measuring apparatus for an elevator system and an elevator system having such a measuring apparatus - Google Patents

Description

The invention relates to a measuring device for an elevator installation with at least one elevator car according to the preamble of the independent claim. In addition, the invention relates to a corresponding elevator installation.

Typically, elevator cars in elevator systems are each equipped with their own drive and their own braking system. The electronic control of the entire elevator system is often designed so that there should be no collisions of the individual elevator cars to stationary obstacles connected to a roadway, such as a roadway end or to an adjacent elevator car. Usually, the roadway is defined by a shaft and a track end by a shaft end. Instead, the roadway may also be designed as a truss or box construction or further. Under roadway here both the directly claimed by an elevator car room as well as the adjoining room, which is limited for example by the shaft space understood. Especially with an emergency stop or even with a normal floor stop of a cabin can not be guaranteed under all circumstances that an upper or lower located on the same roadway further elevator car can stop in time to avoid a collision. This could be avoided by giving the controller sufficient distances between the individual elevator cars and also adapted vertical speeds. Such a requirement, however, can not fully exploit the transport capacity of an elevator installation, which has an impact on the cost-benefit efficiency.

From the European patent EP 769 469 B1 Now an elevator system is known, which comprises means for opening the safety circuit of an elevator car, if it comes to an undesired approach to another elevator car. According to the Patent specification mentioned safety modules are present at each elevator car, which evaluate the cabin positions and speeds to possibly trigger braking operations on other elevator cars can. The individual safety modules must always know and evaluate the cabin positions and speeds of the other elevator cars involved in order to be able to react correctly in an emergency. This requires a special decision module, which is responsible for determining the stop commands in an emergency.

A similar complex solution is from the international patent application WO 2004/043841 A1 known. According to this patent application, infrared, laser or ultrasonic sensors which measure the distances to the adjacent elevator cars located above and below the elevator car can be arranged on each elevator car. In addition, it is proposed additionally to use a roadway or shaft information system, so that, for example, measuring strips arranged in the region of the roadway can be scanned by sensors on the elevator cars in the form of light barriers. Also, this electro-optical approach makes it possible to control the distance of the elevator cars and possibly also the distance to a roadway end, such as an upper or lower shaft end, and if necessary to intervene in the control to prevent a collision.

Especially in the international patent application WO 2004/043841 A1 described solution is complicated because it requires communication between different opto-electronic components of the elevator cars to allow statements about the current distance and the current speeds of the elevator cars.

Another solution will be in the US-A-6079521 described. In addition, the described solutions are difficult to initialize during commissioning, since all systems must be coordinated. The complexity of the systems may make these solutions susceptible to interference.

It is in view of the known arrangements, the object of the present invention to simplify the operation of an elevator installation.

The solution of the objects is achieved by the features of the independent claims. Advantageous developments of the invention are realized by the dependent claims.

The present invention is equally suitable for preventing a collision between two elevator cars that are relatively approaching, and for preventing a collision between an elevator car and a track end. In the following, equivalent variants of the measuring device according to the invention for an elevator installation will be described.

In a first variant, the measuring device according to the invention has an elevator installation with at least one elevator car, which is movable along a roadway of the elevator installation, via at least one transmitter and at least one receiver. In this case, a receiver is arranged on an elevator car and a transmitter on the roadway and / or a transmitter is arranged on an elevator car and a receiver on the roadway. The transmitter emits a beam at a first angle with respect to the direction of travel. The first angle is predetermined such that when the elevator car approaches an obstacle which is stationary relative to the roadway, the beam strikes the receiver.

The measuring device is according to the first variant so redundant interpretable. For this purpose, a transmitter are arranged on the roadway and a receiver on a first elevator car. A second pair of transmitter and receiver is reversed, that is, the transmitter on the elevator car and the receiver arranged on the roadway. In addition, a redundant design of the measuring device can also be achieved in that two transmitters are arranged on the roadway and two receivers on the elevator car.

In a second variant, the measuring device according to the invention has an elevator installation with at least one elevator car, which is movable along a roadway of the elevator installation, via at least one transmitter and at least one receiver. In this case, a receiver and a transmitter are arranged on an elevator car and / or a receiver and transmitter are arranged on a roadway. The transmitter emits a beam at a first angle with respect to the direction of travel. The first angle is predetermined such that when the elevator car approaches an adjacent elevator car or an obstacle which is stationary relative to the roadway, the beam strikes the receiver.

The measuring device according to the second variant preferably has at least one reflector which reflects a beam emitted by the transmitter to the receiver. If the transmitter and the receiver are arranged on the roadway, the reflector is attached to the elevator car. Conversely, the reflector is attached to the roadway, when the transmitter and receiver are arranged on the elevator car. Also in this second variant, the measuring device is redundant interpretable. For this purpose, a pair of transmitters and receivers are arranged on the elevator car and on the roadway. In addition, a redundant design of the measuring device can also be achieved in that two transmitters and two receivers are arranged on the elevator car or on the roadway.

In a third variant, the measuring device according to the invention has an elevator installation with at least one elevator car, which is movable along a roadway of the elevator installation, via at least one transmitter and at least one receiver. In this case, a receiver is arranged on a first elevator car, and a transmitter is arranged on a second elevator car. The transmitter emits a beam at a first angle with respect to the direction of travel. The first angle is predetermined so that when approaching the elevator cars, the beam hits the receiver.

The measuring system of the third variant can also be designed redundantly. An additional transmitter and receiver are in this case arranged on the elevator cars such that either two transmitters are arranged on a first elevator car and two transmitters are arranged on a second elevator car or a respective transmitter and receiver are arranged on a first and a second elevator car.

With knowledge of the above variants, it is open to the skilled person to realize a combination of all variants in an elevator installation. In addition, according to the three variants, the measuring device according to the invention can be equipped with one or more reflectors, which are arranged on an elevator car and / or on the roadway and reflect a beam incident from the transmitter to a receiver.

In all three variants, the sensor emits a beam that can be detected by an associated receiver. This transmitter and receiver pair and optionally one or more associated reflectors are arranged in the region of the roadway and the elevator cars so that when moving one or more elevator cars the beam of the transmitter on the receiver and / or possibly on a reflector generates a traveling measurement point. The receiver and / or the reflector thereby define a temporal or local reaction region in which a suitable reaction can be triggered. This reaction area can be used, for example, to compensate for system reaction times or building tolerances.

The receiver has a sensor area with one or more sensitive sensor areas for detecting the beam. If the sensor area is subdivided into several sections, these can preferably be evaluated separately. For this purpose, the receiver preferably comprises an evaluation system in order to be able to trigger an adapted reaction as a function of which of the sections the beam strikes.

Advantageously, this sensor area is arranged perpendicular to the elevator car or on the roadway. This minimizes the settling of dust particles on the sensor area. To better protect the sensor area from the deposition of dust particles, it is overhanging with respect to a vertical direction, i. with the sensitive sensor side inclined downwards in an angle range from 0 to 90 °, can be positioned. This variant is preferably used in conjunction with a reflector.

The beam generated by the transmitter can be based on different physical principles. The beam comprises electromagnetic, electrical, or magnetic waves, sound or light waves. The sensor area of the receiver is tuned to receive the beam depending on the selected variant. Preferably, transmitters and receivers are selected which transmit or receive infrared, laser or ultrasound beams.

The angle between the beam and the direction of travel can be set variably in time as a function of one or more parameters. In this case, a position, speed or acceleration of an elevator car, a distance, a relative speed and / or a relative acceleration and / or an operating state of the elevator installation can be selected as parameters.

An additional use variant of the measuring device according to the invention opens up, in particular, in the case of a receiver with a sensor region subdivided into a plurality of sections. Since each section can be evaluated separately, the sensor can be evaluated with regard to the position of an elevator car as long as it is within the range of the migrating measuring point. With an appropriate length of the sensor area and / or positioning of the transmitter, receiver and / or reflectors and / or the adjustment of the angle, the measuring device can also be used as absolute position detection device.

An advantage of the invention results from the simple arrangement of commercial components to realize a measuring device that realizes a distance control or a combined distance and speed control and / or determines a position of an elevator car relative to the road. A further advantage lies in the automatic determination of the distance by the receiver and the triggering of an autonomous reaction in case of undesired approach of an elevator car to a roadway end or to an adjacent elevator car. Furthermore, in conjunction with a local computing unit, the receiver is able to trigger a collision-preventing reaction based on speed information with a small amount of computation. In addition, the redundant design of the measuring device provides additional security and enables an autonomous and rapid collision-preventing reaction of an elevator car.

• Fig. 1A eine seitliche Ansicht einer ersten Aufzugsanlage gemäss Erfindung in einem ersten Zeitpunkt;
• Fig. 1B eine seitliche Ansicht der Aufzugsanlage nach Fig. 1A in einem späteren Zeitpunkt;
• Fig. 2 eine seitliche Ansicht eines Teils einer zweiten Aufzugsanlage gemäss Erfindung;
• Fig. 3 eine seitliche Ansicht eines Teils einer dritten Aufzugsanlage gemäss Erfindung.

In the following the invention will be described by means of exemplary embodiments and with reference to the drawings. Show it:

• Fig. 1A a side view of a first elevator installation according to the invention in a first time;
• Fig. 1B a side view of the elevator after Fig. 1A at a later date;
• Fig. 2 a side view of a portion of a second elevator installation according to the invention;
• Fig. 3 a side view of a portion of a third elevator installation according to the invention.

An elevator installation typically has at least one elevator cage which is suspended by means of a traction means. To compensate for the cabin weight, a counterweight of the elevator system is preferably provided, which is also connected to the traction means. To drive the elevator car, the elevator installation is equipped with a drive which comprises a traction sheave, a motor and optionally a holding brake. The traction sheave and the traction agent are in operative contact. The traction sheave and the engine are usually connected to each other via a shaft and / or a gear, so that the motor travels via the traction sheave dun traction means the elevator car.

The space traversed by the elevator car is predetermined by a roadway. The roadway includes the space required directly from the elevator car, as well as the adjoining room. Most of the time given by the roadway space is limited by a lift shaft. In this respect, the terms roadway and elevator shaft can be understood synonymously. The elevator shaft is laterally defined by four shaft walls and by a shaft ceiling and shaft bottom. The shaft ends indicate an area which comprises the shaft ceiling or the shaft floor and the adjacent upper or lower part of the shaft walls.

The measuring device has at least one transmitter and one associated receiver. The transmitter transmits a beam receivable by the receiver. The receiver can initiate a reaction directly or in conjunction with a connected control unit due to a received beam. Optionally, reflectors are also part of the measuring system. The reflectors reflect the beam transmitted by a transmitter directly or via one or more reflectors to a receiver. In the examples shown, the transmitter is preferably designed as a light source which emits a light beam in the visible or invisible wavelength range. Accordingly, the receiver has a photosensitive sensor area which allows receiving the light beam.

A first embodiment of the invention is in connection with the two snapshots in the Figures 1A and 1B described. Shown is a simple elevator installation 10 with an upper elevator car A1 and a lower elevator car A2, both substantially vertically independent on a common roadway 11, for example an elevator shaft 11, of the elevator installation 10 along a direction of travel z are movable. For this purpose, the elevator cars A1, A2 can be provided with a drive and a holding brake per elevator car A1, A2, or, for example, can be individually coupled to a central drive system in order to allow individual movement along the roadway 11. In addition, there are other approaches to individually move the elevator cars of a lift system. The elevator cars can also be moved horizontally or in another direction if the carriageway is oriented accordingly.

A measuring device is provided which comprises, for example, a first electro-optical measuring device 20 with a first transmitter, for example a light source 21, which is arranged in a lower region of the upper elevator car A1, as in FIGS Figures 1A and 1B indicated schematically. Particularly suitable light sources are light-emitting diodes which emit concentrated light. Even better are laser diodes or solid-state lasers.

Furthermore, the measuring device 20 comprises a first receiver 22, which comprises a photosensitive, first sensor region 22 in an upper region of the lower elevator car A2. As sensor region 22, photodiodes, phototransistors or other photosensitive elements can be used.

The first light source 21 is designed and arranged such that it outputs a focused first beam in the form of a light beam L1 at a first angle W1 with respect to the direction of travel z. In the example shown, the light beam L1 is directed downwards.

In Fig. 1A a snapshot is shown (distance between the cars is S1), where the upper elevator car A1 moves downwards at a speed v1 and the lower elevator car A2 stands still (v2 = 0). In the moment shown, the light beam L1 hits somewhere against a wall of the elevator shaft 11 somewhere above the lower elevator car A2.

Now reduces the relative distance of the two elevator cars A1 and A2 to a minimum distance S2, as in Fig. 1B shown, the light beam L1 first hits the sensor portion 22 of the receiver.

According to the invention, the first angle W1 is predetermined or adjusted such that, as the upper and lower elevator cars A1, A2 approach, the first light beam L1 strikes the first sensor region 22 as soon as the minimum distance S2 is reached. Thus, at this moment of impingement, the light beam L1 is detectable by the first receiver 22, 24, and this receiver 22, 24 initiates a response R1, which is passed on to a controller or the like, for example, via a line 23.

The present invention now allows various forms of implementation or expansion stages of the measuring device.

In the simplest form of implementation, a reaction can be triggered immediately upon first contact of the light beam L1 with the sensor region 22. In this case it is sufficient if the sensor region 22 has a size - in the sense of surface area - which makes it possible to ensure that reliable detection of the light beam L1 by the receiver 22, 24 is possible despite the fluctuations in the elevator installation 10 ,

Another embodiment of the invention is shown in Fig. 2 indicated. In this figure, a snapshot is shown shortly after the light beam L1 was first detected by a photosensitive portion 22.1 of the sensor portion 22.

The sections are preferably separately evaluable, ie they each have individual electrical connections. Preferably, in the various embodiments, a corresponding evaluation system 24 (or 24 and 28 in the case of Fig. 3 ) to provide an adapted response (R1, R2, R3, R4) in dependence of which it is possible to trigger on which of the sections 22.1 - 22.n the first light beam L1 strikes.

If one now the same distances as in the Figures 1A and 1B assuming the distance would be smaller than S2 in the moment shown.

Since the upper elevator car A1 continues to move toward the lower car A2 at the speed v1, the "light spot" generated by the light beam L1 shifts to the left. The measuring device can now be designed, programmed or set such that upon the first impact on the section 22.1 of the sensor region 22 an advance warning is issued as a reaction or the elevator installation 10, respectively the elevator car A1 and / or A2 is transferred to a pre-warning mode. If the light point now exceeds a predetermined further section 22.4 of the sensor region 22, then a final reaction can be triggered (for example an emergency stop by triggering the brake device or the safety brake of the upper and / or the lower elevator car A1, A2). This two-step approach adds security and helps prevent false tripping.

Based on Fig. 2 Now, another embodiment of the invention will be explained. As indicated by an arrow below the sensor area 22, the point of light travels to the left at a speed v1 * when the relative distance between the elevator cars A1, A2 is reduced at a speed v1. This speed v1 * allows a computational determination of the speed v1 using simple trigonometric approaches. For example, if the angle W1 is 45 degrees, then v1 = v1 * since tan 45 = 1. If the angle W1 is greater than 45 degrees, then v1 * is greater than v1. At smaller angles W1, v1 * becomes smaller than v1, ie one obtains a kind of reduction or deceleration. Such a slowing down can reduce the size of the sensor area 22, which may be advantageous since the corresponding sensors are expensive.

In Fig. 3 another variant is shown. This variant is currently preferred because it offers the greatest security. As shown, two electro-optical measuring devices are used. The first measuring device is designed analogously to the system shown in the preceding figures. The second measuring device can be identical, but sits almost mirror-inverted in the upper region of the lower elevator car A2. The corresponding second sensor area 26 is seated in the lower area of the upper elevator car A1.

In the example shown, both angles are equal, i. W1 = W2. The angles can also be specified or adjusted differently. With identical design of the electro-optical measuring device and if W1 = W2 applies, set both electro-optical measuring devices at the same time from signals, or trigger at the same time reactions R3, R4.

The figures schematically indicate that the receivers trigger reactions in each case. The nature of the reactions differs depending on the embodiment, programming or setting of the devices. In the figures, it is indicated that the receivers are capable of delivering signals or information via lines or other connections 23 or 27. These signals or information are then either processed before reactions are triggered, or they immediately trigger the responses, for example, by opening a switch that is part of a safety circuit.

There are numerous ways to accomplish the triggering of the reactions. The particular realization depends on various details of the respective elevator installation 10. If, for example, the elevator installation 10 has its own safety circuit per elevator car A1, A2, the safety circuit of the upper and / or lower elevator car A1, A2 can be interrupted by the receiver (s).

An elevator installation 10 preferably has one own safety circuit per elevator car A1, A2, in which several safety elements, such as safety contacts and switches, are arranged in a series connection. The corresponding elevator car A1 or A2 can only be moved if the safety circuit and thus also all safety contacts integrated in it are closed. The safety circuit is connected to the drive or the brake unit of the elevator installation 10 in order to interrupt the driving operation of the corresponding elevator car A1 or A2, if such a reaction is desired.

However, the invention can also be used in elevator systems which are equipped with a safety bus system instead of the mentioned safety circuit.

Alternatively or in addition to opening the safety circuits and the brakes of the respective elevator cars A1, A2 can be triggered.

Alternatively or additionally, any catch brakes of the respective elevator cars A1, A2 can be triggered.

• Öffnen eines Sicherheitskreises von mindestens einer Aufzugskabine A1, A2,
• Signal an eine Aufzugssteuerung,
• Auslösen einer Bremsvorrichtung von mindestens einer Aufzugskabine A1, A2,
• Auslösen einer Fangbremse von mindestens einer Aufzugskabine A1, A2,
• Überführen von mindestens einer Aufzugskabine A1, A2 in einen Vorwarnzustand,
• Anpassung der Vertikalgeschwindigkeit v1, v2 von mindestens einer Aufzugskabine A1, A2.

Depending on the embodiment, one or more of the following reactions can be triggered by the receivers 22, 24, or 26, 28:

• Opening a safety circuit of at least one elevator car A1, A2,
• Signal to an elevator control,
• Triggering a braking device of at least one elevator car A1, A2,
• Triggering a safety brake of at least one elevator car A1, A2,
• Transferring at least one elevator car A1, A2 into a pre-warning state,
• Adaptation of the vertical speed v1, v2 of at least one elevator car A1, A2.

So you can realize with the invention, a distance control or a combined distance and speed control.

The angles W1, W2 can be adjusted in a range of 0 to 90 ° with respect to the vertical direction z. Preferably, the angles W1, W2 are in the range between 0 and 60 degrees, and more preferably between 10 and 50 degrees.

Advantageously, the angle W1, W2 as a function of individual or several parameters, such as the position, speed or acceleration of an elevator car A1, A2, the distance, relative speed or relative acceleration of the elevator car A1, A2 to a reference point or the operating state of the elevator system 10, in time set variably.

By setting the angle W1, W2, for example, at a higher speed of the car A1, A2, the angle W1, W2 can be set smaller, so that the light beam L1, L2 falls on the receiver 22, 24 at an earlier point in time and thus increases an earlier time a reaction R1, R2, R3, R4 can trigger. At a lower speed, accordingly, the need for an early response R1, R2, R3, R4 is reduced, and thus a larger angle W1, W2 can be set. The relationship between acceleration and angle is analogous.

The operating condition of an elevator installation 10, such as in the inspection or maintenance state, often indicates a reduced maximum speed. Thus, in the case of an inspection trip of the elevator car A1, A2, the angle W1, W2 of the light beam L1, L2 can be increased already after the transfer of the elevator car A1, A2 into an inspection state, since the elevator car A1, A2 can only be moved at reduced speed.

The position of the elevator cars A1, A2 serves, for example, to determine the time of a variable adjustment of the angle W1, W2. Accordingly, a critical distance between the elevator cars A1, A2 or between an elevator car A1, A2 and the shaft end is defined. If this value is undershot, the variable setting of the angle W1, W2 begins.

If several elevator cars run in the same shaft 11, then a corresponding measuring device can also be provided between these elevator cars.

A second embodiment of the invention relates to an elevator installation with an elevator car which can be moved along a roadway or elevator shaft in the direction of travel. For this purpose, the elevator car A1 according to the first embodiment, for example, equipped with a drive and a holding brake. A measuring device is provided which, for example, comprises a first electro-optical measuring device with a first transmitter, for example a light source, which is arranged in a lower region of the upper elevator car.

Furthermore, the measuring device comprises a first receiver which comprises a photosensitive, first sensor region at the lower end of the roadway. The first light source is designed and arranged to emit a collimated first light beam at a first angle with respect to the direction of travel. In the example described, the light beam is directed downwards.

In a variant, the positions of the light source and the receiver can also be exchanged so that the receiver is positioned in the lower region of the elevator car and the light source in the region of the lower shaft end. In addition, corresponding sensor areas can also be provided at the upper shaft end of the elevator shaft in order to prevent a dangerous approach of the elevator cage to the upper shaft end.

A third embodiment of the invention relates to an elevator installation with an elevator car which is movable along a roadway or elevator shaft in the direction of travel. For this purpose, the elevator car according to the first embodiment, for example, equipped with a drive and a holding brake. A measuring device is provided which, for example, comprises a first electro-optical measuring device with a first transmitter, for example a light source, which is arranged in the region of the upper shaft end.

Furthermore, the measuring device comprises a first receiver which comprises a light-sensitive, first sensor region likewise spaced apart from the upper shaft end to the light source. The first light source is designed and arranged to emit a collimated first light beam at a first angle with respect to the direction of travel.

Furthermore, the measuring device has a reflector which is arranged in the upper region of the elevator car. The position of the reflector is so determined that when approaching the elevator car to the upper shaft end of the light beam impinges on the reflector and is reflected by this to the receiver of the measuring device. Preferably, the extension of the reflector and the photosensitive sensor region of the receiver are matched to one another, so that in the course of the approach of the elevator car to the upper shaft end of the light beam passes through the entire sensor area. In the example described, the light beam is directed downwards between the light source and the reflector and upwards to the receiver after the reflection.

In a variant, the light source and the receiver are arranged in the upper region of the elevator car and the reflector in the region of the upper shaft end. In addition, corresponding measuring devices can also be provided at the lower shaft end of the elevator shaft in order to prevent a dangerous approach of the elevator cage to the lower shaft end.

The operating principle of the measuring device of the second and third embodiments is the same as in connection with the other embodiments. In this respect, the variants described above can be combined almost arbitrarily with each other.

Claims (13)

1. Measurement apparatus (20) for an elevator system (10) having at least one elevator cab (A1, A2), which can be moved along a travel path (11) of the elevator system (10), the measurement apparatus (20) comprising at least one transmitter (21) and at least one receiver (22, 24), characterized in that

   - a receiver (22, 24) is arranged on an elevator cab (A1) and a transmitter (21) is arranged on the travel path, and/or in that

   - a transmitter (21) is arranged on an elevator cab (A1) and a receiver (22, 24) is arranged on the travel path,

   - the transmitter emitting a beam (L1) at a first angle (W1) relative to the direction of travel (z) and the first angle (W1) being specified such that when an elevator cab (A1, A2) approaches an obstacle that is stationary relative to the travel path (11), the beam (L1) impinges on the receiver (22).
2. Measurement apparatus (20) for an elevator system (10) having at least one elevator cab (A1, A2), which can be moved along a travel path (11) of the elevator system (10), the measurement apparatus (20) comprising at least one transmitter (21) and at least one receiver (22, 24), characterized in that

   - a receiver (22, 24) and a transmitter (21) are arranged on an elevator cab (A1, A2) and the measurement apparatus (20) comprises at least one reflector, which is arranged on the travel path (11), and the reflector reflects an incident beam (L1, L2) coming from the transmitter (21) to a receiver (22, 24), and/or in that

   - a receiver (22, 24) and a transmitter (21) are arranged on a travel path (11) and the measurement apparatus (20) comprises at least one reflector, which is arranged on the elevator cab (A1, A2), and the reflector reflects an incident beam (L1, L2) coming from the transmitter (21) to a receiver (22, 24),

   - the transmitter (21) emitting a beam (L1) at a first angle (W1) relative to the direction of travel (z) and the first angle (W1) being specified such that when the elevator cab (A1, A2) approaches an obstacle that is stationary relative to the travel path (11), the beam (L1) impinges on the receiver (22).
3. Measurement apparatus (20) for an elevator system (10) having at least two elevator cabs (A1, A2), which can be moved along a travel path (11) of the elevator system (10), the measurement apparatus (20) comprising at least one transmitter (21) and at least one receiver (22, 24), characterized in that

   - a receiver (22, 24) is arranged on a first elevator cab (A1, A2) and in that

   - a transmitter (21) is arranged on a second elevator cab (A1, A2) and emits a beam (L1) at a first angle (W1) relative to the direction of travel (z) and the first angle (W1) is specified such that when the elevator cabs (A1, A2) approach one another, the beam (L1) impinges on the receiver (22, 24).
4. Measurement apparatus (20) according to any of claims 1 to 3, characterized in that the angle (W1, W2) between the beam (L1, L2) and the direction of travel (z) can be temporarily variably adjusted on the basis of individual parameters or a plurality of parameters.
5. Measurement apparatus (20) according to claim 4, characterized in that a position, speed or acceleration of an elevator cab (A1, A2), a distance, a relative speed, and/or a relative acceleration of an elevator cab (A1, A2) at a reference point, and/or an operating state of the elevator system (10) are selected as parameters.
6. Measurement apparatus (20) according to any of the preceding claims, characterized in that the receiver (22, 24) has a sensor region (22) that is arranged perpendicularly on the elevator cab and/or the travel path (11).
7. Measurement apparatus (20) according to any of the preceding claims, characterized in that the beam (L1, L2) of the transmitter (21) produces a moving measurement point on the receiver (22, 24) or reflector.
8. Measurement apparatus (20) according to any of the preceding claims, characterized in that the receiver (22, 24) defines a temporal or spatial response region for triggering a response (R1, R2, R3, R4).
9. Measurement apparatus (20) according to any of the preceding claims, characterized in that the receiver (22) has a sensor region (22) having a plurality of sensitive portions (22.1 - 22.n) that can be separately evaluated.
10. Measurement apparatus (20) according to any of the preceding claims, characterized in that the receiver (22, 24) comprises an evaluation system (24) in order to be able to trigger an adapted response (R1, R2, R3, R4) depending on which of the portions (22.1 - 22.n) the beam (L1) impinges on.
11. Measurement apparatus (20) according to any of the preceding claims, characterized in that one or more of the following responses is/are triggered by the receiver (22, 24):

    - breaking a safety circuit of at least one elevator cab (A1, A2),

    - signal to an elevator control unit,

    - triggering a braking device of at least one elevator cab (A1, A2),

    - triggering a safety brake of at least one elevator cab (A1, A2),

    - putting at least one elevator cab (A1, A2) into an advance-warning state,

    - adapting the vertical speed (v1, v2) of at least one elevator cab (A1, A2).
12. Measurement apparatus (20) according to any of the preceding claims, characterized in that a distance check or a combined distance and speed check are carried out and/or a position of an elevator cab (A1, A2) relative to the travel path (11) can be determined by the measurement apparatus (20).
13. Elevator system (10) comprising a measurement apparatus (20) according to any of the preceding claims, wherein the elevator system (10) comprises at least one elevator cab (A1, A2) having one drive and one holding brake per elevator cab (A1, A2) and wherein a collision of the elevator cabs (A1, A2) is preventable by means of a response (R1, R2, R3, R4).

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