Method and apparatus for measuring a clearance between an external toothing of a drive shaft mounted in a gearbox housing and an internal toothing of a brake disc

Abstract

Method for measuring a clearance between an external toothing (42) of a drive shaft (2) mounted in a gearbox housing (8) and an internal toothing (40) of a brake disc (36) in a drive of an elevator system, the brake disc being mounted with its internal toothing (40) on the external toothing (42), without removing the brake disc (36) from the drive shaft (2) for the measurement, comprising the steps - rotationally fixed mounting of a pointer (4) projecting radially from the drive shaft (2) on the drive shaft (2), - fixed arrangement of a length gauge (6) on the gear housing (8) in a position in which the pointer (4) and the length gauge (6) are aligned in a zero position relative to each other, - Rotating the drive shaft (2) with a rotating tool (44) acting on the drive shaft (2) against the fixed brake disc (36) from a zero position to a position in which the teeth of the external toothing (42) of the drive shaft (2) strike the teeth of the internal toothing (40) of the brake disc (36), - Reading the measured value (22) displayed by the length gauge (6) for the adjustment path traveled by the pointer (4) during the previous rotational movement of the drive shaft (2) in the area of ​​the length gauge (6), - Evaluating the measured value (22) read from the length gauge (6), wherein the step of rotating the drive shaft (2) with a rotating tool (44) acting on the drive shaft (2) against the fixed brake disc (36) from a zero position to a position in which the teeth of the external toothing (42) of the drive shaft (2) strike the teeth of the internal toothing (40) of the brake disc (36) is carried out with a specific torque value.

Description

[0001] The present invention relates to a method for measuring a play between an external toothing of a drive shaft mounted in a gear housing and an internal toothing of a brake disc in a drive of an elevator installation according to claim 1, as well as to a device for measuring a play between an external toothing of a drive shaft mounted in a gear housing and an internal toothing of a brake disc according to the preamble of claim 6.

[0002] In elevator construction, it is known to use electric drives for the rotating drive of traction sheaves, onto which a suspension element is placed, allowing an elevator car to be moved up or down in an elevator shaft. A brake disc is mounted on the drive shaft and is used to slow the movement of the elevator car and / or to immobilize the elevator car in a position in the elevator shaft. To ensure reliable transmission of the braking force to the drive shaft, the drive shaft has external teeth and the brake disc has internal teeth, which are designed to match each other so that, when these components are new, the brake disc sits on the drive shaft with or almost no play.

[0003] With intensive and prolonged use of the electric drive, the teeth of the external and internal gearing can wear down due to the frequent load changes and the friction that occurs under load on the tooth surfaces during use, resulting in increased play between the teeth. Increased play between the teeth initially only becomes noticeable in the form of reduced drive comfort, as the play leads to jolts in the travel behavior of the elevator car when the brake is applied or released, depending on the direction of travel and the load in the elevator car. While such a loss of comfort may still seem tolerable, wear on the teeth can also become relevant to the safety of the elevator system if the remaining tooth thickness is no longer sufficient to safely transfer the force moments occurring during braking from the brake disc to the drive shaft.In the worst case, the teeth can become so worn over the service life of the drive that the teeth can no longer transfer the braking torque exerted by the brake disc to the drive shaft and thus fail technically in their function.

[0004] For safety reasons, elevator systems are subject to ongoing technical inspections to verify their functionality and safety. However, due to the limited space required for elevator systems in buildings, the drives are typically difficult to access. It is also very difficult to disassemble a drive in the confined machine rooms to check for wear on drive components and then reassemble the drive. Such measures result in comparatively high costs.

[0005] In addition, the disassembly and subsequent reassembly of the drive takes some time, during which the elevator system is unavailable to the building's users. Downtimes of an elevator system caused by the disassembly and subsequent reassembly of the drive are particularly frustrating for the building's users if it is discovered that the drive components being inspected are still in safe working order.

[0006] DE 25 20 908 A1 discloses measuring the play between the external gearing of a drive shaft mounted in a gearbox and the internal gearing using a torque-resistant indicator mounted on the drive shaft and a plug-in shaft. It is not disclosed how this measurement method could be used in a drive for an elevator system.

[0007] It is the object of the present invention to propose a measuring method and a device with which it is possible to measure the play of the teeth of the external toothing on the drive shaft and the internal toothing of a brake disc mounted on the drive shaft without having to dismantle the drive.

[0008] The object is achieved for a generic method by the method steps of claim 1. The object is achieved by a generic device according to the characterizing features of claim 6.

[0009] In order to measure the free play between the teeth of the external gearing of the drive shaft, which mesh with each other in the operating position, and the internal gearing of the brake disc, a pointer is attached to the drive shaft in a radial direction and is non-rotatably mounted. If the drive shaft is rotated about its axis of rotation, the pointer moves with the drive shaft. The play between the teeth of the internal gearing and the external gearing is ideally not measurable because it does not exist, or it is, for example, 2 mm, although such a large play between adjacent intermeshing teeth already indicates high wear and suggests that the gearing needs to be repaired. The relatively narrow range of possible measured values ​​for the play in the gearing between the drive shaft and the brake disc, at most a few mm, shows that the drive shaft can only rotate by a few angular degrees oronly needs to be rotated by a fraction of an angle wheel to determine the amount of play between the teeth. Thus, the pointer connected to the drive shaft is also rotated by a maximum of only a few angular degrees during a measurement. However, over the length of the pointer in the longitudinal direction, the comparatively small play between the teeth of the gearing results in a movement at a measuring point remote from the drive shaft, which can be measured by a dial indicator.

[0010] The rotationally fixed fastening can be achieved by clamping the pointer onto the drive shaft, gluing it on or connecting it to the drive shaft in some other way in such a way that the relative position of the pointer does not change when the drive shaft rotates.

[0011] For a measurement, a length dial gauge is also fixedly mounted on the gearbox housing in a position where the pointer and the length dial gauge are aligned in a zero position. To ensure that the length dial gauge and the pointer can be aligned in a zero position, the pointer must be long enough to reach from the drive shaft to the location of the length dial gauge, and the pointer must be able to make contact with the length dial gauge without play. The length dial gauge can be mounted inside the gearbox housing or on its outside. The location is determined solely by practical considerations. Mounting the length dial gauge on the outside of the gearbox housing is advantageous because it then eliminates the need to open the gearbox housing.If the gearbox housing has openings in the wall that allow easy access to the interior of the gearbox housing, it is of course also possible to easily install the dial gauge inside the gearbox housing. If the dial gauge provides a calibration option that allows a current distance value resulting from the current spatial assignment of the pointer to the dial gauge to be reset to a zero value, it is not necessary to precisely align the pointer and the dial gauge. In this case, an at least approximately precise, but in any case play-free, alignment with each other, followed by a subsequent reset, is sufficient to subsequently perform a measurement.

[0012] A dial indicator can be a digital or mechanical length dial indicator. In a mechanical length dial indicator, a plunger is held in a guide in which the plunger can move axially against a mechanical spring. In this measurement case, the pointer, which is fixedly arranged on the drive shaft and in contact with the plunger, moves the plunger when the drive shaft rotates. The longitudinal movement of the plunger is transmitted via a rack to a gear wheel. The gear wheel is rigidly connected to a pointer that rotates in a watch case. As the pointer in the watch case rotates, it indicates the travel of the plunger on a dial located behind the pointer in the watch case. This travel can be read by an operator. Digital length dial indicators, for example, work with laser light, the reflection of which is measured and converted into a distance value.A digital length dial indicator based on a laser measuring method does not contact the pointer fixed on the drive shaft, but only measures its movement using a laser-assisted distance measurement before and after a rotation of the drive shaft.

[0013] The question of what is meant by a zero position depends on how the subsequent measurement is carried out.

[0014] If, in a first method of carrying out the measurement, the drive shaft is first rotated from a rest position in a first direction until the intermeshing teeth of the internal gearing and the external gearing block one another, then the measured value of the path covered by the pointer in the area of ​​the length dial gauge when the drive shaft is rotated in the first direction is read, the drive shaft is then rotated back to the rest position in order to then rotate the drive shaft from the rest position in the opposite second direction until the intermeshing teeth of the internal gearing and the external gearing block one another, and then the measured value of the path covered by the pointer in the area of ​​the length dial gauge when the drive shaft is rotated in the second direction is read, the zero position of the rotational position of the drive shaft is based on the angular position which it has in the rest position.The pointer and the dial gauge are positioned relative to each other so that, in this rotational position of the drive shaft, these two components indicate a zero adjustment range for the pointer and a travel range for the pointer connected to the drive shaft when the drive shaft is rotated from its rest position. A measured value for the clearance of the meshing teeth is determined by adding the measured travels for the rotation of the drive shaft from its rest position in the first and second directions.

[0015] In a second method of performing the measurement, the drive shaft is first rotated in a first direction until the intermeshing teeth of the internal and external gears lock each other. The resulting rotational position of the drive shaft forms the basis for the zero position of the pointer and the length dial gauge. The pointer and the length dial gauge are zeroed relative to each other in this rotational position of the drive shaft. The drive shaft is then rotated in the second direction opposite to the first direction until the intermeshing teeth of the internal and external gears lock each other. The distance traveled by the pointer during this rotational movement of the drive shaft can then be read on the length dial gauge.

[0016] Depending on how the zero position is set and the subsequent measurement is carried out, there are different ways of determining the length of the path covered by the pointer when the drive shaft is rotated during a measurement, starting from a zero position using the pointer and the dial gauge. However, the aim is always to rotate the drive shaft against the fixed brake disc using a twisting tool acting on the drive shaft from a zero position to a position in which the teeth of the external gearing of the drive shaft touch the teeth of the internal gearing of the brake disc. The path covered by the pointer when the drive shaft is rotated represents a measured value, which can then be converted into a value for the play between the teeth of the internal gearing and the external gearing.

[0017] During the measurement, the brake disc must be locked in place to provide a fixed point for the measurement against which the drive shaft is rotated. The brake disc can preferably be locked in place using the brake device acting on the brake disc.

[0018] An example of a twisting tool could be a handwheel connected to the drive shaft of the drive motor to manually rotate the drive shaft. It is also possible to apply a wrench or torque wrench to the drive shaft to rotate the drive shaft in the first and / or second direction. Finally, the drive motor itself can also be used to twist the drive shaft against the brake disc in the first and / or second direction during a measurement.

[0019] The measured value displayed and read by the dial gauge for the adjustment traveled by the pointer during the previous rotation of the drive shaft in the area of ​​the dial gauge can then be evaluated. The evaluation can consist of deciding whether the measured value read by the dial gauge is acceptable and indicates no need for repair, or whether the measured value indicates a need for repair of the gearing. This decision can be confirmed by comparing the measured values ​​with values ​​in a table that are classified as non-critical or critical for a given elevator drive.However, the evaluation can also be limited to converting the measured value for the travel of the pointer taken from the length dial gauge into a value that is representative of the amount of free play between the teeth of the internal gearing and the external gearing, for example into a mm value for the tooth play that the teeth of the internal gearing and external gearing have in relation to each other.From the value for the radius at which the measuring point for the length dial gauge is removed from the axis of rotation of the drive shaft and from the angular degree by which the drive shaft could be rotated during the measurement, which in turn can be calculated from the adjustment path read off the length dial gauge, the value for the free play exhibited by the internal toothing of a brake disc and the external toothing of a drive shaft can be calculated, particularly if the distance between the toothings and the axis of rotation of the drive shaft is known.For a specific elevator drive, values ​​for the measured travel and / or the free play corresponding to the measured travel can also be listed in a table. These values ​​can be used as comparison values ​​for evaluating the measurement taken and allow an assessment of whether the measured values ​​correspond to a critical or still acceptable level of free play in the gearing. An individual conversion of the measured value for the travel into a value for free play in the measured elevator drive is then unnecessary.

[0020] With the proposed method for measuring the clearance between the external gearing of a drive shaft mounted in a transmission housing and the internal gearing of a brake disc, it is not necessary to remove the brake disc from the drive shaft. Instead, it is sufficient to attach the pointer to the drive shaft, attach the dial gauge to the transmission housing, establish the zero position between the pointer and the dial gauge, and then move the drive shaft between the stops that limit the clearance between the teeth in order to display and read the travel of the pointer on the dial gauge during rotation of the drive shaft. The measured value for the travel can then be evaluated.

[0021] The device according to the invention comprises a pointer and a length dial gauge. The pointer extends from a base in a longitudinal direction and has a measuring point at a location remote from the base. The base is provided with a connecting means for permanently attaching the base with the pointer to a drive shaft. The connecting means can consist, for example, of a clamp, a magnet, a Velcro strip, or an O-ring, which is placed around the drive shaft and then tightened to the outer circumference of the drive shaft with a clamping element such that a stationary seat of the base with the pointer on the drive shaft is established. The length dial gauge has a dial gauge holder with a fastening means formed thereon for permanently attaching the length dial gauge to the gearbox housing.The fastening means can, for example, consist of a magnet or a suction cup, with which the length dial gauge can be connected to the gear housing at almost any installation location in such a way that the length dial gauge cannot be displaced from its position to another position during a measurement by a movement impulse exerted on the length dial gauge by the pointer. The device therefore essentially consists of the pointer and the length dial gauge, with which the adjustment path of a pivoting movement of the pointer can be measured. Using the connecting means and the fastening means, the device can be easily mounted to an existing elevator drive and in particular to a gear housing sufficiently firmly to be able to carry out an accurate measurement of the tooth play between the external toothing of the drive shaft and the internal toothing of a brake disc mounted on it.After a measurement, the device can also be easily removed from the elevator drive and reused in another elevator drive for another measurement.

[0022] According to the invention, the step of rotating the drive shaft against the fixed brake disc is carried out with a rotating tool acting on the drive shaft from a zero position to a position in which the teeth of the external gearing of the drive shaft strike the teeth of the internal gearing of the brake disc, with a specific torque value. If the drive shaft is moved with a specific torque value, the evaluation of the measured value determined by the length dial indicator can be carried out on a comparable data basis. Thus, if the torque with which the drive shaft is rotated is low, only a low measured value for the movement of the pointer may be displayed on the length dial indicator. However, the low measured value may be incorrect because the teeth of the internal and external gearing did not mesh properly with each other during such a measurement.A portion of the free play between the teeth of the gearing would be ignored in such a measurement, and any corresponding tooth wear would remain undetected. If the measured value determined under the influence of a torque that is too low is compared with the value from a table determined under the influence of a higher torque, and this is still classified as non-critical, the play measured with the lower torque could also be classified as non-critical based on the comparison with the table value, even though the measured value for the play would be higher under a comparably high torque and could possibly already be considered critical.Conversely, if the torque is too high, there is a risk that the measured play will be greater than a comparison value determined with a lower torque, and the measured value will be classified as critical, although the measured value measured under the influence of a lower torque would still be in a range that can be considered non-critical.

[0023] According to one embodiment of the invention, the length dial indicator is aligned at a right angle to the longitudinal center axis of the pointer in the zero position to the measuring point on the pointer. By aligning the length dial indicator at a right angle to the longitudinal center axis of the pointer, the conversion of the measured adjustment travel to a value for the gear play is simplified and standardized.

[0024] According to one embodiment of the invention, the output shaft of the drive motor and the drive shaft, onto which the brake disc is mounted, are connected to one another via a flexible coupling, and the pointer is fixedly connected to the drive shaft in an area located outside the flexible coupling. In elevator drives, flexible couplings are often installed between the drive motor and the traction sheave, onto which the support means of the elevator car are mounted. These couplings serve the purpose of absorbing vibrations from the drive motor and the downstream drive train. For example, claw couplings are used as flexible couplings in which the claws do not directly touch, but rather a polymer mass is arranged between the claws, which has a material-related elasticity. The polymer mass absorbs vibrations that act from the drive motor on the drive train.To avoid the possibility of the measurement result being falsified during a measurement due to the stretching and / or compression of the polymer mass of an elastic coupling, it is proposed to connect the pointer to the drive shaft in an area that lies outside the elastic coupling. During the measurement, a torque is applied to the drive shaft, which rotates it by the amount of play between the teeth of the internal gearing and the external gearing. However, the elasticity of the polymer mass resulting from the elastic coupling and a resulting additional angle of rotation that the twisting tool must cover during the measurement are not taken into account in the measurement because the elasticity-related rotational movement does not affect the adjustment path of the pointer during the measurement, as the pointer is connected to the drive shaft behind the elastic coupling.If the elasticity-related adjustment travel were included in the measurement, there is a risk that the play would be determined to be larger than it actually is. Alternatively, the pointer can also be fixed on the output shaft of the drive motor, on the side of the claw coupling facing the motor, if, for example, the elasticity-related adjustment travel can either be measured or at least approximately calculated from the measurement result.

[0025] According to one embodiment of the invention, the elevator system is de-energized for the measurement. The system can be de-energized mechanically, for example, by placing the counterweights of the elevator system on designated buffers, and / or the elevator system is de-energized electrically by de-energizing the electric drive. Any tension in the elevator system's drive train resulting from the counterweights and / or the electric drive cannot then distort the measurement result.

[0026] According to one embodiment of the invention, the drive shaft is turned during the measurement using a screw screwed into the front face, whereby the screw has been tightened to a defined torque value before the measurement. A screw screwed into the front face is often present in electric drive motors for elevator drives, for example, in order to attach a handwheel to the drive shaft in order to also be able to turn the electric drive manually. If the drive shaft is moved during the measurement on or over the screw screwed into the front face, measurement errors could arise if the screw is tightened with too little or too much torque. For this reason, it is advantageous to set the screw screwed into the front face to a defined torque value as the tightening torque before starting the measurement.

[0027] According to the invention, the connecting means has a clamping ring at the base, the free end of which can be placed around the drive shaft and inserted into a clamping lever as a further component of the connecting means. The clamping ring can be made of a flexible and elastic material in order to be able to adapt to different diameters of drive shafts. With a flexible clamping ring, it is easy to insert it into the interior of the gearbox housing, loop it around the drive shaft, and then insert the free end into the clamping lever. An elastic material also has the advantage of having a higher coefficient of friction. The friction forces that the tensioned clamping ring builds up in relation to the circumferential surface of the drive shaft are therefore higher, and the pointer sits more firmly on the drive shaft. The clamping lever can have a toggle lever mechanism in order to be able to build up correspondingly high clamping forces.The clamping lever can also be designed in such a way that it is pushed over a dead center during a clamping process in order to prevent it from automatically snapping back from the clamped position to a relaxed position.

[0028] According to one embodiment of the invention, the fastening means formed on the dial gauge holder is a magnetic holder. In ferromagnetic gear housings, a magnetic holder can generate sufficiently high holding forces to hold a linear dial gauge in its fixed position during a measurement. The magnetic holder can be easily placed on the gear housing and removed again after the measurement, without the need for special mounting equipment or assembly work.

[0029] Further modifications and embodiments of the invention can be found in the following description, the drawings and the claims.

[0030] The invention will be explained in more detail below using an exemplary embodiment. The figures show: Fig. 1: a front view of a device for measuring the free Fig. 2: a detailed view of the base of the pointer, Fig. 3: a side view of the pointer, and Fig. 4: a sectional view of a gearbox housing.

[0031] In Fig. 1 shows a device V for measuring the play between the external toothing of a drive shaft 2 mounted in a gear housing 8 and the internal toothing of a brake disk in a drive of an elevator system (not shown in detail in the drawing). A pointer 4 is fixedly attached to a drive shaft 2 and extends along a longitudinal direction L. In the exemplary embodiment, the pointer 4 has a length of 320 mm. The pointer 4 is supported on the drive shaft 2 by a base 12. The device V also includes a length dial gauge 6, which is mounted on the outside of a gear housing 8 via a dial gauge holder 16.

[0032] At an end of the pointer 4 remote from the base 12 is a measuring point 10, at which the plunger 20 of the length dial gauge 6 engages, via which a pivoting movement of the pointer 4 is displayed in the length dial gauge 6 as a measured value 22. In the position shown in the exemplary embodiment, the length dial gauge 6 is in the zero position and is aligned at a right angle to the longitudinal center axis LM of the pointer 4 with the measuring point 10 on the pointer 4. When the drive shaft 2 is rotated in the direction indicated by an arrow I, the pointer 4, which is fixedly connected to the drive shaft 2, moves in the direction of arrow II. The movement of the pointer 4 presses the plunger 20 in the direction of arrow III, whereupon the pointer in the length dial gauge 6 moves in the direction of arrow IV. The movement of the pointer in the length dial gauge 6 results in a measured value 22.The drive shaft 2 can only be rotated in one direction against the fixed brake disc if there is play between the teeth of the external toothing of the drive shaft 2 and the internal toothing of the brake disc.

[0033] In the exemplary embodiment, a clamping ring 24 is used as the connecting means 14 for the stationary attachment of the pointer 4 to the drive shaft 2. The clamping ring 24 is tensioned via a clamping lever 26 that is pivotally mounted on the base 12. The dial gauge holder 16 is fixedly connected to the gear housing 8 via a fastening means 18.

[0034] In Fig. Figure 2 shows a detailed view of the base 12 of the pointer 4. In the view shown, the clamping lever 26 is in an open position, in which a free end of the clamping ring 24 can be easily inserted into a hook receptacle located on the clamping ring 26 and removed therefrom in order to attach the pointer 4 to the drive shaft 2 or to detach it again.

[0035] In Fig. Figure 3 shows a side view of the pointer 4. The clamping ring 24a is correctly placed on the drive shaft 2 because it does not engage around the drive shaft 2 in the area of ​​an elastic coupling 28, in the exemplary embodiment a claw coupling, as is the case with the clamping ring 24b. If the clamping ring 24 is clamped onto the drive shaft 2 as in the case of the clamping ring 24b, there is a risk that a relative movement between the claws of the claw coupling, which is enabled by an elastic connecting means between the claws, will be transmitted to the pointer 4.

[0036] In Fig.4 shows a sectional view through a gear housing 8. The drive shaft 2 is driven via the output shaft 30 of the drive motor 32. The output shaft 30 of the drive motor 32 and the drive shaft 2 are drivingly connected to one another via the flexible coupling 28. In the exemplary embodiment, the drive force is transmitted to a traction sheave 34 via a planetary gear arranged downstream of the drive shaft 2. A suspension element can then be placed on the traction sheave 34, with which an elevator car is moved up and down in the elevator shaft of an elevator system. The sectional view shows the brake disk 36, to which a braking force can be exerted by the braking device 38. The braking force acting on the brake disk 36 is transmitted via the teeth of an internal toothing 40 to the teeth of an external toothing 42 formed on the outer circumference of the drive shaft 2.In the exemplary embodiment, the output shaft 30 of the drive motor 32 and the connected drive shaft 2 can be rotated via a handwheel as an example of a turning tool 44. Rotation with a defined torque is possible via the screw 46, to which, for example, a torque wrench can be attached.

[0037] The invention is not limited to the embodiment described above. It will be readily apparent to those skilled in the art to modify the embodiment to adapt it to the requirements of a specific application. List of reference symbols 2 drive shaft 4 hands 6 Length dial gauge 8 Gearbox housing 10 measuring points 12 Base 14 connecting devices 16 dial gauge holders 18 fasteners 20 pestles 22 measured value 24 clamping ring 26 clamping levers 28 elastic coupling 30 Output shaft 32 drive motor 34 traction sheave 36 brake disc 38 Braking device 40 internal gearing 42 external gearing 44 Twisting tool 46 Screw V device L Longitudinal direction LM longitudinal center axis

Claims

[1] Method for measuring a play between an external toothing (42) of a drive shaft (2) mounted in a gear housing (8) and an internal toothing (40) of a brake disc (36) in a drive of an elevator installation, which is placed with its internal toothing (40) on the external toothing (42) without dismantling the brake disc (36) from the drive shaft (2) for the measurement, comprising the steps - torsion-proof mounting of a pointer (4) on the drive shaft (2) in a radial direction, - fixed arrangement of a length dial gauge (6) on the gear housing (8) in a position in which the pointer (4) and the length dial gauge (6) are aligned in a zero position with respect to each other, - Rotating the drive shaft (2) with a rotating tool (44) acting on the drive shaft (2) against the fixed brake disc (36) from a zero position to a position in which the teeth of the external toothing (42) of the drive shaft (2) strike the teeth of the internal toothing (40) of the brake disc (36), - reading the measured value (22) indicated by the length dial gauge (6) for the adjustment path covered by the pointer (4) during the previous rotational movement of the drive shaft (2) in the area of ​​the length dial gauge (6), - Evaluating the measured value (22) read from the length dial gauge (6), wherein the step of rotating the drive shaft (2) with a rotating tool (44) acting on the drive shaft (2) against the fixed brake disc (36) from a zero position into a position in which the teeth of the external toothing (42) of the drive shaft (2) strike the teeth of the internal toothing (40) of the brake disc (36) is carried out with a specific torque value. [2] Method according to claim 1, characterized by that the length dial gauge (6) in the zero position is aligned at a right angle to the longitudinal center axis (LM) of the pointer (4) to a measuring point (10) on the pointer (4). [3] Method according to one of the preceding claims, characterized by that an output shaft (30) of a drive motor (32) and the drive shaft (2) onto which the brake disc (36) is mounted are connected to one another via an elastic coupling (28), and the pointer (4) is fixedly connected to the drive shaft (2) in a region which lies outside the elastic coupling (28). [4] Method according to one of the preceding claims, characterized by that the elevator system is de-energized for the measurement. [5] Method according to one of the preceding claims, characterized bythat the drive shaft (2) is rotated during the measurement on or via a screw (46) screwed into the front side, wherein the screw (46) has been tightened with a defined torque value before the measurement. [6] Device (V) for measuring a play between an external toothing (42) of a drive shaft (2) mounted in a gear housing (8) and an internal toothing (40) of a brake disc (36) in a drive of an elevator installation, which is placed with its internal toothing (40) on the external toothing (42) without dismantling the brake disc (36) from the drive shaft (2) for the measurement, with a pointer (4) and a length dial gauge (6), wherein the pointer (4) extends from a base (12) in a longitudinal direction (L) and has a measuring point (10) at a location remote from the base (12), the base (12) has a connecting means (14) for the stationary fastening of the pointer (4) on the drive shaft (2) and the length dial gauge (6) has a dial gauge holder (16) with a fastening means (18) formed thereon for fixed fastening of the length dial gauge (6) to the gear housing (8), characterized bythat the connecting means (14) has a clamping ring (24) on the base (12), which can be placed with a free end around the drive shaft (2) and can be inserted into a clamping lever (26) as a further component of the connecting means (14). [7] Device (V) according to claim 6, characterized by that the fastening means (18) formed on the dial gauge holder (16) is a magnetic holder.

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