Draw-wire sensor with a control unit and sensors

Abstract

The invention relates to a draw-wire sensor comprising a housing and / or frame. A wire reel on which a measuring wire can be wound and unwound is provided and rotatably mounted in the housing and / or frame. A drive drives the wire reel of the measuring wire. A measuring sensor records the rotation of the drive. In addition, a brake system and a processor-controlled control unit with a memory are provided. The control unit is configured to analyse the rotation of the drive recorded by the measurement sensor and to determine a wire draw-in speed and / or a wire draw-in acceleration. Based on status information from the brake system, the control unit can also detect whether there is a tear in the measuring wire, with the status information being recorded by means of a sensor system. In addition, the invention relates to a method for the safe operation of the draw-wire sensor and the use of the draw-wire sensor in a non-operating mode, in particular for transport, in a normal operating mode and for a reference run.

Description

[0001] Rope length sensor with a control unit and sensors

[0002] Technical area

[0003] The invention relates to a cable length sensor comprising a. a housing and / or frame, b. a cable drum rotatably mounted in the housing and / or frame, on which drum a measuring cable is provided so as to be windable and unwindable, c. a drive for the cable drum of the measuring cable, wherein the drive for the cable drum for winding and unwinding the measuring cable is formed by an electric motor, d. a measured value sensor for detecting the rotation of the drive, e. a braking system, f. a processor-controlled control unit with a memory, which is designed to evaluate the rotation of the drive detected by the measured value sensor and to determine a cable retraction speed and / or a cable retraction acceleration, to detect whether there is a tear in the measuring cable on the basis of status information from the braking system, wherein the status information is detected by a sensor.Furthermore, the invention relates to a method for the safe operation of the rope length sensor and the use of the rope length sensor in a non-operating mode, in particular for transport, in a normal operating mode and for a reference run.

[0004] Description

[0005] Rope length sensors are used, for example, to measure the distance by which a crane's boom has been extended. The rope length sensor contains a measuring rope that is wound around a rope drum. The rope drum is rotatably mounted in a housing and / or frame of the rope length sensor. When the measuring rope is pulled off the rope drum, the rope drum rotates. This rotation is measured by a sensor in a measuring transducer. It provides a measurement of the rope length pulled off the rope drum. For this purpose, the rope length sensor is attached to a reference point and the free end of the measuring rope is attached to a part that is moving relative to the reference point. The pulled-off rope length then provides the movement of the moving part. For example, the rope length sensor can be attached to a stationary part of a crane and the end of the measuring rope can be attached to the end of a crane boom.The signal from the rope length sensor can then be used to monitor the extension length of the crane boom. The rope drum is subject to a restoring torque, which can be applied by a spring motor, for example. The measuring rope is pulled out against this restoring torque. The measuring rope is guided out of the rope length sensor housing via a rope guide with low friction. This rope guide can be designed so that the rope can also be pulled out of the housing at an angle. Such rope guides can have a roller guide with two pairs of guide rollers arranged crosswise around the measuring rope. The rope guide can also be formed by a body provided with a guide bore and mounted so that it can pivot on all sides in a spherical bearing surface.

[0006] State of the art

[0007] DE 295 198 09 U1 relates to a cable drum arrangement for a cable length sensor with a housing and a cable drum arranged in the housing, mounted rotatably against the action of a return drive and guided for longitudinal movement, with a measuring cable wound onto the cable drum. The cable is guided out of the housing via a cable outlet fixed to the housing. Using an adjusting gear, the cable drum is adjustable in the axial direction within the housing according to its revolutions such that the turns of the measuring cable being unwound or wound onto the cable drum are essentially in the plane of the cable outlet. When the cable is wound onto the cable drum, one cable turn lies next to the other, with the cable being wound neatly onto the cable drum in one layer. The cable runs through a cable outlet fixed to the housing and thus has a defined position relative to the housing.To achieve this, the cable drum is moved axially by the actuating gear in accordance with the revolutions of the cable drum when winding or unwinding the cable, namely by one cable diameter with each revolution. The end plate has a threaded hole with which the end plate is mounted on a threaded spindle. The threaded spindle is non-rotatably attached to an end plate of the cylindrical housing. When the cable drum rotates, the end plate screws along the threaded spindle so that the end plate also moves axially with the rotation. The rotary movement of the cable drum is transmitted via off-center / axial guide rods / which extend through openings in the end plate of the cable drum to an input gear of a reduction gear. The input gear of a reduction gear is in turn connected to the input shaft of an angle encoder.

[0008] EP 2653428 A1 describes a cable length sensor comprising a housing and / or frame. A cable drum is rotatably mounted in the housing and / or frame, onto which a measuring cable can be wound and unwound. A sensor records the number of rotations of the cable drum. The cable length sensor also has a reset drive for the cable drum, which rewinds the unwound measuring cable onto the cable drum.

[0009] Common return drives use a spring motor. The springs of spring motors can lose their required elasticity over the course of their service life. In particular, applications with a high number of cycles and simultaneously long measuring lengths, such as those in high-bay warehouses, elevators, or automation systems, lead to a shortened service life due to the high load changes in the spring motor or mainspring. This results in high maintenance costs for this type of drive. In the worst case, continuous load can even lead to spring breakage. EP 1 014 031 B1 relates to a measuring cable displacement sensor. The measuring cable displacement sensor has a housing in which a cable drum is arranged which can rotate and be displaced longitudinally relative to the axis of rotation. A cable feedthrough fixed to the housing is provided for the measuring cable.A longitudinal drive for the cable drum with a spindle drive comprises a threaded spindle that can be screwed relative to a spindle nut. The longitudinal drive has an additional gear so that the rotation of the cable drum is transmitted to the spindle drive. A flat spring cascade is used as the return drive. Instead of the flat spring cascade, an electric motor with a corresponding control system can be used, which - similar to the spring cascade - is mounted coaxially on the right end of the shaft. The rotation speed during winding of the cable drum is limited by the use of a contactless, magnetic brake. The components involved must be made of an electrically conductive material.Since the winding takes place on the radially outer surface using a measuring cable, the magnets are preferably aligned longitudinally, i.e. parallel to the rotation axis of the cable drum, between two components adjacent in this axial direction. Due to the rotation of the cable drum, an eddy current is initially generated in the component carrying the brake magnet, regardless of the distance between the brake magnet and the component to be influenced. This eddy current creates a magnetic field that closes over the part not in the magnetic field and creates a braking torque. The braking effect is determined - in addition to the strength of the magnet used - very much by the distance between the magnet and the component to be influenced, which is why this distance can be adjustable. One disadvantage is that the eddy current brake acts in both directions. It therefore also brakes the extension.It is therefore suitable for moderate adjustment speeds. A further disadvantage is that the braking power only acts in a fixed ratio to the speed. This ratio is determined by the selection of magnets, air gap and materials. This means that the braking power cannot be changed during operation. With the state of the art, the braking power and the resulting speed reduction are effective at all times. In the design shown, an electric motor must therefore also overcome the braking torque of the eddy current brake. This has a negative effect on the dynamics and electrical effective power or efficiency. Furthermore, the reduction in retraction speed with increased adjustment speed of the system in the elevator direction can lead to slack rope and thus to the measuring rope jumping off the measuring drum.

[0010] Another disadvantage of conventional rope length sensors is that if the measuring rope breaks or the rope is accidentally released, an uncontrollable situation arises that can destroy the rope length sensor. In the worst case, the user could be injured when the rope snaps back into place.

[0011] Disclosure of the invention

[0012] The object of the invention is therefore to eliminate the disadvantages of the prior art and to provide a functionally reliable cable length sensor with a long service life, which can be safely controlled in particular in the event of a break in the measuring cable or an accidental release of the measuring cable.

[0013] The object of the invention is achieved by the features of the independent claims. Advantageous embodiments of the invention are described in the dependent claims.

[0014] In a first aspect, the invention preferably relates to a cable length sensor comprising a. a housing and / or frame, b. a cable drum rotatably mounted in the housing and / or frame, on which a measuring cable is provided so as to be windable and unwindable, c. a drive for the cable drum of the measuring cable, wherein the drive for the cable drum for winding and unwinding the measuring cable is formed by an electric motor, d. a measured value sensor for detecting the rotation of the drive, e. a braking system, f. a processor-controlled control unit with a memory, which is configured to evaluate the rotation of the drive detected by the measured value sensor and to determine a cable retraction speed and / or a cable retraction acceleration, to detect whether a tear is present in the measuring cable based on status information from the braking system, wherein the status information is detected via a sensor system.

[0015] The advantages of the cable length sensor according to the invention include, on the one hand, the service life of the cable length sensor is significantly increased, in particular through the use of an electric motor for the reset drive, and, on the other hand, safe and controlled operation can be guaranteed at all times.

[0016] Safe and controlled operation of the rope length sensor is primarily enabled by the fact that status information of the rope length sensor and / or its components can be recorded using suitable sensors, such as a transducer or other sensor technology, and evaluated by a control unit. Based on the control unit's evaluation, an operating state, such as a safety stop, can be set (preferably automatically) for the rope length sensor according to the invention. This allows necessary measures to protect the rope length sensor and, if necessary, also persons in the vicinity to be initiated immediately.

[0017] The cable retraction speed or acceleration can be used to determine whether the measuring cable is being retracted uncontrollably. Uncontrolled retraction of the measuring cable occurs, for example, if a user accidentally releases the measuring cable while pulling it out of the cable length sensor or if the measuring cable breaks, causing the measuring cable to snap or spring back due to the restoring torque of the drive.

[0018] As soon as an uncontrolled retraction is detected, the cable length sensor according to the invention preferably stops or brakes the drive or the restoring torque using its braking system, thus preventing uncontrolled snapping or rebounding and thus protecting the cable length sensor and bystanders from damage. The cable length sensor according to the invention can also determine, in particular based on the status information of the braking system via the control unit, whether there is a break in the measuring cable. In another preferred embodiment, the status information of the braking system can also be used to determine whether the measuring cable is fully wound onto the cable drum.

[0019] For the purposes of the invention, status information of the braking system preferably refers to specific data and parameters that describe a current status and / or the performance of the braking system. The status information can, for example, include information about the position of a braking component (e.g., a lever), information about a pressure in the braking system, information about a temperature of a braking component, information about brake pad wear, or other relevant measured variables. This data can be recorded by various sensors in the braking system and forwarded to a control unit.

[0020] The control unit preferably has a bidirectional data connection to the sensor system for recording the status information of the braking system, to the sensor, and / or to the motor or its motor control. It is understood that the bidirectional data connection can be configured either wirelessly or wired. The control unit can preferably be designed for the braking system in such a way, among other things, that the measuring cable can be braked dynamically.

[0021] As already described, the drive – i.e. the electric motor – is preferably designed to provide a reset torque for the cable length sensor and, in particular, to enable the winding or coiling of the measuring cable. Accordingly, the electric motor replaces a spring motor in conventional cable length sensors, in which the reset torque is achieved by the spring. In addition to the increased service life, the electric motor, via a motor controller and / or the control unit, enables the measuring cable to be pulled out of the cable length sensor with consistent force. With a spring motor, on the other hand, the force required to pull the measuring cable out of the cable length sensor continuously increases due to the spring tension. Furthermore, the amount of the reset torque can be changed or adjusted at any time via the motor controller and / or the control unit, depending on the respective requirements.

[0022] In a preferred embodiment, the torque of the drive or electric motor can also be determined by detecting electrical parameters. A motor controller can preferably be provided, which can also adjust the torque depending on requirements.

[0023] In a further preferred embodiment, the cable length sensor is supplied with energy or power via a voltage source. This can be a battery, an accumulator, or a direct power supply from the mains.

[0024] In a further preferred embodiment of the cable length sensor according to the invention, the braking system comprises an EMF braking system for braking the electric motor and a cable drum brake. This combination of braking devices enables improved control over the movement of the measuring cable. The EMF braking system offers the possibility of braking the electric motor quickly and precisely, which significantly improves safety and control during operation. At the same time, the cable drum brake complements this function by providing a direct brake for the cable drum, ensuring additional safety and reliability. The combination of these braking devices contributes overall to optimizing the operation of the cable length sensor, maximizing safety, and increasing the service life of the cable length sensor. The term "EMF" is preferably used as an abbreviation for "electromotive force."

[0025] According to the invention, the cable drum brake preferably has a brake lever that presses on the measuring cable lying on the cable drum to decelerate it. The cable drum brake can thus decelerate the cable drum without blocking it. Furthermore, it holds the windings of the measuring cable on the cable drum to prevent it from jumping off the cable drum.

[0026] In a further preferred embodiment of the cable length sensor according to the invention, a sensor system is assigned to the cable drum brake. The sensor system can preferably detect a stroke of the brake lever and transmit the detected stroke to the control unit, which can then evaluate whether a tear is present in the measuring cable. There are several suitable options for implementing the sensor system, including displacement sensors such as potentiometers, laser or ultrasonic sensors for distance measurement, magnetic sensors for detecting changes in the magnetic field, or optical sensors. Furthermore, the stroke of the brake lever can preferably also be used to determine whether the measuring cable is completely wound onto the cable drum.

[0027] In a further preferred embodiment of the cable length sensor according to the invention, the cable drum brake is designed to be spring-loaded and thus operates in a spring-loaded manner. This advantageously results in the cable drum brake remaining effective even when de-energized.

[0028] Furthermore, the cable drum brake is preferably designed to be actuated by a lifting magnet, an electric motor, a pneumatic lifting cylinder, and / or a hydraulic lifting cylinder. The use of a lifting magnet is particularly preferred. The brake is preferably released by controlling the lifting magnet, for example, via the control unit. This process is preferably monitored by sensors. In addition, the sensors preferably detect the stroke of the brake lever to detect the presence or absence of the measuring cable (cable break).

[0029] The sensor installed on the cable drum brake (preferably a stroke switch / stroke sensor) can detect four conditions in particular:

[0030] • ho = brake lever is directly on the cable drum (no measuring cable present

[0031] / rope break);

[0032] • hi = brake lever rests on the measuring cable on the cable drum;

[0033] • bi2 = brake lever rests on the collar of the rope drum flange

[0034] (Rope drum has passed its end position => rope break);

[0035] • hend = brake activated / brake lever is in the upper end position;

[0036] Preferably, the cable drum brake is activated when there is no supply voltage (device not in operation / transport), a reference run of the cable length sensor is being performed, a safety stop is activated, or the cable length sensor is operating in installation mode. In a further preferred embodiment, the cable length sensor is characterized in that the EMF braking system can generate a speed-dependent braking torque by short-circuiting all motor windings of the electric motor. The motor connected to the cable drum is thereby braked significantly, preventing the cable drum from overrunning.

[0037] Furthermore, the EMF braking system is preferably configured to be automatically activated in the event of a power interruption and to remain activated throughout the entire de-energized period. This ensures an additional level of safety.

[0038] In a further preferred embodiment, the control unit is configured to control the EMF braking system, the rope drum brake, and / or the electric motor. This centralized control allows the aforementioned components to be efficiently coordinated to ensure precise control of the rope length, braking functions, and the rope drive. The coordinated control enables improved performance, efficiency, and safety of the rope length sensor. It contributes to smooth operations, precise rope positioning, and rapid response to various operating situations.

[0039] In a further preferred embodiment, the cable length sensor has one or more interfaces via which status information and operating states can be transmitted to higher-level control devices. By transmitting status information and operating states (in real time), the higher-level control devices receive current and precise insights into the operation of the cable length sensor. This allows them to monitor operation, perform diagnostics, optimize performance parameters, and, if necessary, implement appropriate adjustments or measures to improve the efficiency and safety of the system.

[0040] For the purposes of the invention, an interface preferably refers to a defined connection or a specific point through which the cable length sensor can exchange information. The interface can take various forms, for example, electronic connections, communication protocols, sensors, or other technical devices capable of acquiring and transmitting data. Furthermore, higher-level control devices for the purposes of the invention preferably refer to central control systems or devices that coordinate and monitor the cable length sensor.

[0041] In a further preferred embodiment, the cable length sensor can be parameterized and controlled via one or more interfaces. This allows (customer-side) adaptation to different applications. In addition to (customer-side) parameterization before commissioning, the system can be controlled and parameters changed via the interface during runtime. This makes it possible to start different operating modes (e.g., setup mode / reference run / normal operation / etc.) as well as to change the response behavior of the safety shutdown.

[0042] If the optional interface is not used, the cable length sensor preferably operates autonomously with factory-set parameters and automatic execution of preset operating modes. In this case, some safety functions may be limited.

[0043] In a further preferred embodiment, the control unit is configured to control all components that are in data communication with it and to provide data via the interfaces for higher-level control devices connected to the cable length sensor and to process data received via the interfaces.

[0044] The control unit is preferably designed as a microcontroller. Depending on the control and data processing, the cable length sensor can operate in different modes. The cable length sensor can therefore preferably be switched to different operating modes via the control unit and / or one or more interfaces.

[0045] In a further preferred embodiment of the cable length sensor according to the invention, a brushless electric motor is provided as the drive. The use of a brushless electric motor as the drive for the cable length sensor offers advantages in the form of lower maintenance requirements, a longer service life, and higher efficiency compared to brushed motors. Furthermore, a brushless electric motor enables a more compact design and generates less heat.

[0046] In a further preferred embodiment, the electric motor is provided as an external rotor motor. A brushless external rotor motor is particularly preferred, which, thanks to its high torque reserves, can be directly coupled and operated without a gear in the cable length sensor.

[0047] In a further preferred embodiment of the cable length sensor according to the invention, a motor controller is provided, which is configured to control the electric motor and preferably to regulate the motor speed, acceleration, and torque. The integrated motor controller enables precise control of the electric motor. The motor speed, acceleration, and torque can be optimized depending on application requirements, which can lead to more efficient operation, better performance, and a longer service life of the motor.

[0048] In a further preferred embodiment, the EMF braking system is connected between the motor control and the electric motor. This enables precise and rapid control of the braking function.

[0049] In a further preferred embodiment, the motor controller has a bidirectional data connection with the control unit. The bidirectional data connection between the motor controller and the control unit in this embodiment enables efficient real-time communication. This allows control commands to be transmitted and received precisely, resulting in improved control precision and increased responsiveness of the cable length sensor.

[0050] In a further preferred embodiment of the cable length sensor according to the invention, the sensor is designed as an encoder in the electric motor and is mechanically connected to a motor shaft enclosed in the electric motor and the cable drum. Because the encoder is integrated into the electric motor, the cable length sensor can advantageously be designed very compactly. In a further preferred embodiment, however, the encoder is designed outside the motor. This allows for easier access, e.g., for maintenance purposes or replacement.

[0051] Furthermore, the encoder is preferably in unidirectional data connection with the motor control.

[0052] In a further aspect, the invention relates to a method for the safe operation of the rope length sensor of the above-mentioned type, wherein a break in the measuring rope, an uncontrolled retraction of the measuring rope and / or a fully wound-up state of the rope drum is detected via the control unit and the braking system is subsequently activated automatically. The control unit preferably accesses information values ​​from the sensors installed in the rope length sensor. Such a method enables the rope length sensor according to the invention to be operated safely at all times. The automated activation of the braking system thus protects the rope length sensor, as well as bystanders or objects, from damage or injury. This is preferably a fully automatic system, so that safe operation is possible without manual intervention.

[0053] A person skilled in the art will recognize that the advantages, technical effects, and preferred embodiments discussed in connection with the cable length sensor according to the invention apply analogously to the method for its safe operation. Likewise, all advantages, technical effects, and preferred embodiments described in the context of the method are transferable to the cable length sensor.

[0054] In a preferred embodiment, the rope length sensor can retract the measuring rope at a maximum rope retraction speed selected from the range 5 m / s to 20 m / s.

[0055] Furthermore, the cable length sensor can preferably retract the measuring cable with a maximum cable retraction acceleration, which is selected from the range 4 m / s 2 up to 25 m / s 2. Furthermore, it is preferred that the maximum torque of the drive can correspond to an amount selected from a range between 0.2 Nm and 5 Nm.

[0056] The above-mentioned values ​​for maximum rope retraction speed, maximum rope retraction acceleration, and maximum torque are theoretical values ​​that the rope length sensor can achieve. However, the claimed method for safe operation of the rope length sensor preferably prevents these values ​​from being reached, as thresholds or maximum limits are set for detecting irregularities that stop the rope length sensor before these maximum values ​​are reached.

[0057] In a further preferred embodiment, the method is characterized in that the braking system comprises an EMF braking system for braking the electric motor and a cable drum brake. Upon detection of a tear in the measuring cable, uncontrolled retraction of the measuring cable, and / or a fully wound-up state of the cable drum, the cable drum brake and the EMF braking system are activated simultaneously. The simultaneous activation of both braking devices in the braking system ensures particularly efficient braking performance. Preferably, in the event of a safety stop, the motor is also released, while the EMF braking system and the cable drum brake are immediately activated. Both braking devices in combination brake the measuring cable drum to a standstill in the shortest possible time. Furthermore, the combination of both braking devices prevents the measuring cable drum from overrunning and the measuring cable from jumping off.

[0058] In a further preferred embodiment, the method is characterized in that the break in the measuring cable and the fully wound state of the cable drum are detected by a sensor system detecting a brake lever stroke of the cable drum brake and transmitting it to the control unit. It is understood that the control unit analyzes the recorded sensor data and recognizes corresponding conditions, taking appropriate measures. The control unit preferably has appropriate means and algorithms (possibly also artificial intelligence algorithms) for analyzing the recorded data. A "break in the measuring cable" refers in particular to a continuous interruption in the continuous structure of the measuring cable. This can be caused by various factors, such as wear, mechanical overload or damage, corrosion, or other external influences.Such a crack in the measuring cable impairs the functionality of the cable and is therefore of particular importance for the safety and proper operation of a cable length sensor.

[0059] A "complete winding on the cable drum" preferably means that the measuring cable has been wound properly and, in particular, without overlaps or tangles on the cable drum. With a complete winding, there is preferably no excess measuring cable hanging from the cable length sensor; instead, a cable thimble located at the end of the measuring cable rests against the housing or the outlet opening of the cable length sensor. The entire possible windable length of the measuring cable is thus wound or coiled on the cable drum. Correct and complete winding is crucial to ensure that the cable can be used efficiently without disruptions that could impair the functionality of the system.

[0060] In a further preferred embodiment, the method is characterized in that an uncontrolled retraction of the measuring cable occurs when the cable retraction speed and / or the cable retraction acceleration exceeds a maximum limit value stored in the control unit, wherein the cable retraction speed and / or the cable retraction acceleration are determined by the rotation of the drive detected by the measuring sensor via the control unit.

[0061] It goes without saying that the control unit can also determine the cable pull-out speed and cable pull-out acceleration based on the rotation detected by the sensor.

[0062] A maximum limit in this context refers to a predefined value for the rope retraction speed and / or acceleration, which is programmed or stored in the control unit. As soon as the actually measured rope retraction speed and / or acceleration exceeds this predefined limit, this is identified as uncontrolled retraction of the measuring rope. The exact value of the maximum limit depends on the specific requirements, such as safety requirements, and the configuration of the rope length sensor.

[0063] The maximum limit value for the rope retraction speed may preferably correspond to an amount selected from a range between 5% and 90% of the maximum rope retraction speed,

[0064] The maximum limit value for the rope retraction acceleration may preferably correspond to an amount selected from a range between 5% and 90% of the maximum rope retraction acceleration.

[0065] A cable retraction or retraction speed and / or a cable retraction or retraction acceleration can preferably be determined by the control unit, for example, by evaluating the rotation of the motor or drive as a function of time. Since the cable drum on which the measuring cable is wound is mechanically connected to the drive shaft, the cable retraction or retraction speed or the cable retraction or retraction acceleration can be deduced accordingly.

[0066] Furthermore, it is possible for the control unit to also detect an uncontrolled retraction due to a stored minimum torque limit being undershot. However, the drive torque is not recorded via the transducer, but preferably via a motor controller. The minimum torque limit can preferably correspond to an amount selected from a range of 5% - 50% of the maximum torque. In a further aspect, the invention relates to the use of the cable length sensor of the type mentioned above in a non-operating mode, in particular for transport, wherein the electric motor is in an inactive state and the braking system, in particular a cable drum brake and an EMF braking system, is in an active state.This mode ensures that the rope is held securely during transport, which is particularly crucial during transport in vehicles or when moving the rope length sensor from one location to another. It minimizes the risk of rope damage or unwanted movement, contributing to the longevity and functionality of the rope length sensor. Preferably, the measuring rope can still be pulled out by an operator's hand when the rope length sensor is not in operation. Both braking devices (rope drum brake and EMF braking system) in combination preferably prevent the measuring drum from overrunning and the measuring rope from jumping off the rope drum. The measuring rope can also be wound back onto the rope drum by hand, preferably using a tool.

[0067] For transport, it is preferable to install an additional transport lock to prevent the measuring cable drum from twisting due to vibration.

[0068] In a further aspect, the invention relates to the use of the rope length sensor of the above-mentioned type for a reference run, wherein the measuring rope is initially at least partially unwound from the rope drum, wherein the electric motor and the rope drum brake are in an active state and the EMF brake system is in an inactive state, wherein the operating values ​​of the rope length sensor are set to a low rope retraction speed compared to normal operation and to a maximum rope retraction acceleration as well as a maximum torque, wherein the reference run is preferably terminated automatically when the rope retraction speed corresponds to a value of 0 m / s and the torque and a time exceed a threshold value stored in the control unit.

[0069] The reference run brings the rope length sensor into an operational state during commissioning or after a safety stop.

[0070] In a preferred embodiment - particularly with regard to a reference run - a cable retraction speed that is low compared to normal operation preferably corresponds to an amount selected from a range between 1% and 25% of the maximum cable retraction speed. For the purposes of the invention, operating values ​​are preferably the values ​​that are set for the operation of the cable length sensor in the respective operating mode via the control unit. The set operating values ​​for the cable retraction speed and cable retraction acceleration are based on the fact that no counterforce acts on the measuring cable and the measuring cable is virtually loose. If a counterforce acts on the measuring cable, the measuring cable is retracted at a cable retraction speed or cable retraction acceleration that is lower than the operating values.

[0071] The set operating value for the torque, however, is only achieved when the measuring cable is pulled in against a high resistance or a high counterforce, or when the measuring cable, for example, is in contact with the housing of the cable length sensor with the cable thimble. The set torque, as an operating parameter, is therefore the maximum torque that can be achieved by the cable length sensor in this mode. Since the measuring cable or the end of the measuring cable is usually loose during a reference run after being unwound from the cable length sensor, it is not pulled in with a maximum torque defined as an operating parameter, but with a torque reduced by this. Accordingly, large torque reserves are available.

[0072] During a reference run, the measuring cable is preferably wound / pulled in at a low speed and with reduced torque (high torque reserves are available) for safety reasons. Once the measuring cable is completely retracted (the cable thimble is preferably positioned at the cable exit) or the measuring cable is taut (the cable thimble is fixed at a point on the system remote from the device), the reference run is preferably completed, and the appropriate modes for further operation can be started.

[0073] The reference run operating mode is preferably terminated automatically when three conditions are met:

[0074] 1. the cable retraction speed preferably corresponds to a value of 0 m / s

[0075] 2. The torque preferably exceeds a threshold value stored in the control unit. This threshold value can preferably correspond to an amount selected from the range 30% - 90% of the maximum torque. 3. A time preferably exceeds a threshold value stored in the control unit. Preferably, the time from the moment the torque threshold value stored in the control unit is exceeded is recorded and compared with the threshold value (time). The threshold value (time) can preferably correspond to ls.

[0076] Regardless of the aforementioned conditions, the reference run can preferably also be terminated or interrupted by a so-called "timeout." This preferably records an additional time from the start of the reference run. As soon as a predefined operating time is exceeded, the rope length sensor will preferably interrupt the reference run and detect an error. The predefined operating time can correspond to a time selected from the range 10s - 60s. The selection of the predefined operating time depends in particular on the device size (faster retraction of the unwound rope for devices with shorter measuring or rope lengths).

[0077] In a further aspect, the invention relates to a use of the rope length sensor of the type mentioned above in an installation mode, wherein the measuring rope is first at least partially unwound from the rope drum by an operator while the electric motor is in an inactive state and the EMF braking system and the rope drum brake are in an active state; wherein the rope length sensor automatically detects that the measuring rope has been unwound from the rope drum and subsequently brings the EMF braking system into an inactive state and the electric motor into an active state and the torque of the electric motor is increased so that the measuring rope is retracted, wherein the operating values ​​of the rope length sensor are set to a low rope retraction speed compared to normal operation and a maximum rope retraction acceleration as well as a reduced torque compared to normal operation.The installation mode is primarily designed for safe and easy installation of the cable length sensor on appropriate systems. The operating parameters are modified (reduced) in such a way that the risk of accidental flicking of the measuring cable (e.g., the cable thimble slips from the installer's hand) is very low compared to a standard cable length sensor. Furthermore, the operating parameters set in this mode prevent uncontrolled retraction of the measuring cable and protect the cable length sensor from damage and cable breakage.

[0078] As already explained, operating values ​​refer to those values ​​that can (theoretically) be implemented by the rope length sensor in a given operating mode. However, the operating values ​​for the rope retraction speed or rope retraction acceleration are only implemented by the rope length sensor if the measuring rope is not subject to any counterforce and is retracted without resistance. If a counterforce or resistance is present, the measuring rope is retracted at a lower rope retraction speed or rope retraction acceleration.

[0079] The operating parameter for torque, on the other hand, is the value that can be applied by the cable length sensor when the measuring cable is retracted under strong resistance. At low resistance, a low torque is applied, and torque reserves are still available. For ease of operation, the measuring cable is slightly extended by an operator in installation mode during commissioning or after a safety stop. The cable length sensor preferentially detects the extension, deactivates the EMF braking system, activates the motor, and slowly increases the torque to the values ​​set for installation mode. A reference run is not required.

[0080] A reduced torque compared to normal operation - in particular with respect to an installation mode - may preferably correspond to an amount selected from a range between 30% and 100% of the maximum torque.

[0081] In a further preferred embodiment—particularly with regard to the installation mode—a low cable retraction speed compared to normal operation preferably corresponds to an amount selected from a range between 30% and 50% of the maximum cable retraction speed. In installation mode, a safety stop is preferably initiated if a limit value for the cable retraction speed and / or the cable retraction acceleration is exceeded.

[0082] The limit value for the rope retraction speed during installation mode can preferably correspond to an amount selected from a range between 5% and 25% of the maximum rope retraction speed,

[0083] The limit value for the rope retraction acceleration during the installation mode, on the other hand, can preferably correspond to an amount selected from a range between 5% and 25% of the maximum rope retraction acceleration.

[0084] In a further aspect, the invention relates to the use of the rope length sensor of the above-mentioned type in a normal operating mode, wherein the measuring rope is initially at least partially unwound from the rope drum, wherein the electric motor is in an active state and the braking system, in particular a rope drum brake and an EMF braking system, is in an inactive state, wherein the operating values ​​of the rope length sensor are set to a maximum rope retraction speed and maximum rope retraction acceleration as well as a maximum torque.

[0085] During normal operation, the basic functionality is similar to that of a spring-loaded cable length sensor. The measuring cable is moved by the cable length sensor, and the extension length is transmitted to the cable length sensor via a rotary encoder, e.g., a transducer. Unlike a spring-loaded cable length sensor, the operating parameters are monitored, and a safety stop is initiated if a deviation is detected (e.g., a cable break or uncontrolled retraction of the measuring cable).

[0086] A "normal operating mode" preferably refers to the state or functioning of the rope length sensor according to the invention when operating under typical or expected conditions. For example, the rope length sensor can be mounted on a fixed part of a crane, while the end of the measuring rope is attached to the crane's boom. In this embodiment, the rope length sensor monitors the extension length of the crane boom using its signals. The rope drum is subject to a restoring torque generated by the electric motor. The measuring rope is pulled out against this restoring torque and can, of course, also be retracted when the crane boom is retracted. It is important to note that the actual rope retraction speed is related to the retraction speed of the crane boom, and that the crane boom does not reach the maximum rope retraction speed, i.e., the preset operating value.

[0087] Therefore, as previously explained, the operating values ​​in this embodiment are theoretical values ​​that the rope length sensor can only achieve if certain conditions are met. For example, the maximum rope retraction acceleration and speed could only be achieved if there was no resistance or counterforce at all—that is, if the rope length sensor were decoupled from the crane boom mentioned as an example.

[0088] However, the rope length sensor preferably prevents the theoretically achievable maximum rope pull-out speeds and rope pull-out accelerations from being reached, since a safety stop is preferably activated beforehand.

[0089] In normal operating mode, a safety stop is preferably initiated if a limit value for the rope retraction speed and / or the rope retraction acceleration is exceeded.

[0090] The limit value for the rope retraction speed in normal operating mode can preferably correspond to an amount selected from a range between 10% and 90% of the maximum rope retraction speed,

[0091] The limit value for the rope retraction acceleration in normal operating mode, on the other hand, can preferably correspond to an amount selected from a range between 10% and 90% of the maximum rope retraction acceleration.

[0092] Furthermore, a safety stop can also be initiated if the torque exceeds a

[0093] The limit value for the torque can preferably correspond to an amount selected from a range between 5 % and 50 % of the maximum

[0094] torque,

[0095] Further embodiments are explained in more detail below with reference to the accompanying drawings. The invention is not intended to be limited solely to these listed embodiments. They serve merely to explain the invention in more detail. The present invention is intended to relate to all objects that a person skilled in the art would consider obvious for implementing the invention, now and in the future.

[0096] Short description of the drawing

[0097] Fig. 1 shows a schematic overall view of a cable length sensor according to the invention with electromotive retraction.

[0098] Fig. 2 shows a longitudinal section of the rope length sensor according to Fig.l.

[0099] Fig. 3 shows an overview of the control components and actuators in the cable length sensor

[0100] Preferred embodiments

[0101] Fig. 1 shows a schematic overall view of a cable length sensor 10 according to the invention with a drive 12, which is designed as an electric motor 14. In the present embodiment, a brushless servomotor is used as the electric motor 14. The cable length sensor 10 further comprises a base body 16 with a housing 18. Reference numeral 20 designates a sensor, which is arranged on a first end face 22 of the housing 18 in a sensor housing 24. It should be noted that a separate sensor 20 is not absolutely necessary. Alternatively, the sensor 20 can be designed—as an encoder—in the electric motor 14. In principle, both variants for the sensor 20 can also be used simultaneously for additional safety.

[0102] A measuring cable 32 is guided from a cable nozzle or cable outlet 30 of the housing 18 fixed to the housing. This measuring cable 32 is wound onto a cable drum 42 (not shown in Fig. 1) contained within the housing 18 of the cable length sensor 10. The electric motor 14, with a motor housing 28, is flanged onto a second end face 26 of the housing 18. The electric motor 14 is particularly configured to apply a restoring torque and replaces a spring motor of conventional cable length sensors. The applied restoring torque enables the measuring cable 32 to be wound onto the cable drum 42. However, the restoring torque is preferably also applied continuously as the measuring cable 32 is pulled out of the cable length sensor 10, so that an operator (or a device) must work against the restoring torque when pulling out the measuring cable 32.This ensures that the measuring cable 32 is properly unwound from the cable drum 42 – for example, even if an operator suddenly stops pulling it out and then pulls on the measuring cable 32 again. Without a continuously applied restoring torque, overlaps or tangling of the measuring cable 32 on the cable drum 42 could occur in such a case. The amount of the torque / restoring torque can be adjusted as needed via a motor control.

[0103] During operation of the cable length sensor 10, a control unit can detect critical situations, such as an uncontrolled retraction of the measuring cable 32 or a tear in the measuring cable 32, based on values ​​recorded by the sensor 20 and / or other sensors. In response, a braking system is activated, which preferably comprises a cable drum brake 33 and an EMF braking system 95 (not shown in Fig. 1).

[0104] Fig. 2 shows a longitudinal section of the cable length sensor 10, as shown in Figure 1. Where the figures correspond, the same reference numerals are used. The cable length sensor 10 comprises the base body 16. A shaft 34 is axially mounted in a bearing 35 in the end faces 22, 26 of the housing 18 of the base body 16. A splined hub 36 and a guide spindle 38 are slid onto the shaft 34 as a guide 40 for a cable drum 42. The guide spindle 38 is mounted on the shaft 34 by bearings 44, 46. The cable drum 42 is seated on the guide spindle 38. For this purpose, the cable drum 42 has a measuring drum flange 48, 50 on each of its end faces 47. The measuring drum flange 48 sits on the guide spindle 38 with a driver and a guide bush 52. Accordingly, the other measuring drum flange 50 sits on the spline hub 36 with a driver 53. The measuring cable 32 is wound on or off the circumference of the cable drum 42.The measuring cable 32 is provided in an unwindable manner, with one end of the measuring cable 32 located in the housing 18 being fastened to a cable suspension 54 on the cable drum 42. Due to its strength, the measuring cable 32 is designed as a wire cable 56 in the present embodiment. Other materials with sufficient strength, such as plastic fibers, are of course also conceivable as the measuring cable 32.

[0105] The shaft 34 is driven by the electric motor 14. Also visible here is a rotor 57 of the electric motor 14. 58 denotes a motor flange. The electric motor 14, with its motor housing 28, is flanged to the housing 18 via a motor mount 61. A motor shaft 60 connected to the rotor 57 is coupled to the shaft 34, which rotates with the cable drum 42. When winding or unwinding the measuring cable 32, the cable drum 42 is guided axially by the guide spindle 38 over the splined hub 36, so that the measuring cable 32 is always wound or unwound in a fixed position relative to the cable outlet 30.

[0106] The motor housing 28 contains a removable cover 62 with a sealing plug 64. Reference numeral 66 denotes a freewheel. A pressure washer 70 holds the freewheel 66 in position in the motor housing 28. The motor shaft 60 is secured with a clamping ring 72.

[0107] Control elements, such as a processor-controlled control unit, for the electric motor 14 are provided on a circuit board 74. The control unit 31 (see Fig. 3) acts preferentially on the control elements and triggers a braking operation when necessary.

[0108] The cable length sensor 10 is supplied with the required electrical voltage via a plug connection 76, which is arranged in a connector housing 78. This supply voltage is used, in particular, to supply the electric motor 14, the circuit board 74, the control unit 31, and the cable drum brake 33. The plug connection 76 can also contain data lines, in particular for parameterization and / or communication with a higher-level control system, and can thus act as an interface 37 (see Fig. 3).

[0109] The cable drum brake 33 comprises a brake housing 82 in which a solenoid 84 is arranged. The solenoid 84 contains a movable plunger 86, or piston and coils 88 with an iron core. The plunger 86 is guided by a compression spring 90 at the upper end in a pressure bushing 92, which is vertical in this case. The brake lever 94 is located at the lower end of the plunger 86. The compression spring 90 presses the plunger 86 against the brake lever 94. When voltage is applied to the coils 88, the plunger 86 is pulled away from the brake lever 94. The brake lever 94 then releases the measuring cable 32. Depending on the voltage applied to the coils 88, the brake pressure can be dynamically varied. In combination with the control unit 31, they thus also form control means for a dynamic braking process of the measuring cable 32.

[0110] Furthermore, a sensor system is provided which detects a stroke of the brake lever 94 and transmits the detected stroke to the control unit 31, which can evaluate based on this whether a tear is present in the measuring cable 32.

[0111] The shaft 34 extends through the end face 22 of the housing 18 and is connected to a sensor shaft 96 of the sensor 20 via a coupling 98. An adapter flange 100 is provided as a spacer element between the sensor 20 and the end face 22 of the housing 18, so that the coupling 98, in particular, is protected. Instead of the coupling 98, a gear (not shown) can be inserted under the adapter flange 100 if necessary. The adapter flange 100 can be designed differently if required, depending on the sensor 20 used.

[0112] The sensor 20 detects the rotation of the drive 12, based on which the control unit 31 can determine a cable retraction or cable extension speed and / or a cable retraction or cable extension acceleration.

[0113] For the safe operation of the cable length sensor 10, a break in the measuring cable 32, an uncontrolled retraction of the measuring cable 32, and / or a fully wound-up state of the cable drum 42 can be detected via the control unit 31. Subsequently, the cable drum brake 33 and the EMF braking system 95 (see Fig. 3) are automatically activated simultaneously. In the process, the brake lever 94 within the cable drum brake 33 presses on the measuring cable 32 lying on the cable drum 42. The EMF braking system 95, in contrast, generates a speed-dependent braking torque by short-circuiting all motor windings of the electric motor 14. TI

[0114] Fig. 3 shows an overview of the control components and actuators in the cable length sensor 10 according to the invention. The cable length sensor 10 is centrally controlled and / or regulated by the control unit 31.

[0115] To detect a break in the measuring cable 32 or to detect that the cable drum 42 is fully wound up, a sensor system assigned to the cable drum brake 33 records the brake lever stroke of the cable drum brake 33 and transmits the recorded values ​​to the control unit 31. The control unit 31 has algorithms that can analyze and evaluate the recorded values. If there is a break in the measuring cable 32 or the measuring cable 32 is fully wound up on the cable drum brake, the cable drum brake 33 is activated to brake the cable drum 42, and the EMF braking system 95 is activated to brake the electric motor 14.

[0116] To detect an uncontrolled retraction of the measuring cable 32, the control unit 31 evaluates the rotation of the drive 12 detected by the sensor 20 and first determines the cable retraction speed and / or the cable retraction acceleration. If the cable retraction speed and / or the cable retraction acceleration exceed a maximum limit value stored in the control unit 31, an uncontrolled retraction of the measuring cable 32 has occurred.

[0117] Furthermore, a motor control 93 can be provided, which is interposed between the control unit 31 and the electric motor 14 and is configured to control the electric motor 14 and preferably to regulate the motor speed, the acceleration and the torque.

[0118] Furthermore, a voltage source 51 is provided, which supplies the cable length sensor 10 and all components with power. This can be a battery, an accumulator, or a direct power supply from the mains.

[0119] In addition, the cable length sensor 10 preferably has two interfaces 37, via which, on the one hand, status information and operating states can be transmitted to higher-level control devices (output interface) and, on the other hand, via which the cable length sensor 10 can be parameterized and controlled (input interface). List of reference symbols

[0120] 10 Rope length sensor 54 Rope suspension

[0121] 12 drive 56 wire rope

[0122] 14 electric motor 57 rotor

[0123] 16 base body 58 motor flange

[0124] 18 Housing 60 Motor shaft

[0125] 20 Transducer 61 Engine mount

[0126] 22 first front side 62 cover

[0127] 24 sensor housings 64 sealing plugs

[0128] 26 second front side 66 freewheel

[0129] 28 Motor housing 70 Pressure washer

[0130] 30 Cable outlet of the housing 72 Clamping ring

[0131] 31 Control unit 74 Circuit board

[0132] 32 measuring cable 76 plug connection

[0133] 33 Cable drum brake 78 Connector housing

[0134] 34 Shaft 82 Brake housing

[0135] 35 bearing 84 lifting magnet

[0136] 36 splined hub 86 tappet

[0137] 37 interface 88 coils

[0138] 38 Guide spindle 90 Compression spring

[0139] 40 Guide 92 Pressure bushing

[0140] 42 Cable drum 93 Motor control

[0141] 44 bearings 94 brake levers

[0142] 46 bearings 95 EMK brake system

[0143] 47 End faces of the measuring drum 96 Sensor shaft

[0144] 48 Measuring drum flange 98 Coupling

[0145] 50 Measuring drum flange 100 Adapter flange

[0146] 51 Voltage source

[0147] 52 guide bushing

[0148] 53 drivers

Claims

Patent claims 1. Cable length sensor (10) comprising a. a housing (18) and / or frame, b. a cable drum (42) rotatably mounted in the housing (18) and / or frame, on which drum a measuring cable (32) can be wound up and unwound, c. a drive (12) for the cable drum (42) of the measuring cable (32), wherein the drive (12) for the cable drum (42) for winding up and unwinding the measuring cable (32) is formed by an electric motor (14), d. a measured value sensor (20) for detecting the rotation of the drive (12), e. a braking system, f. a processor-controlled control unit (31) with a memory, which is designed to evaluate the rotation of the drive (12) detected by the measuring sensor (20) and to determine a cable retraction speed and / or a cable retraction acceleration, to detect whether there is a tear in the measuring cable (32) on the basis of status information of the braking system, wherein the status information is detected via a sensor system.

2. Cable length sensor (10) according to claim 1, characterized in that the braking system comprises an EMF braking system (95) for braking the electric motor (14) and a cable drum brake (33).

3. Cable length sensor (10) according to claim 2, characterized in that the cable drum brake (33) has a brake lever (94) which presses on the measuring cable (32) lying on the cable drum (42) for braking.

4. Cable length sensor (10) according to claim 3, characterized in that the sensor system detects a stroke of the brake lever (94) and transmits the detected stroke to the control unit (31), which can evaluate based thereon whether a tear is present in the measuring cable (32).

5. Cable length sensor (10) according to one of claims 2 to 4, characterized in that the cable drum brake (33) is designed to be spring-loaded.

6. Cable length sensor (10) according to one of the preceding claims 2 - 4, characterized in that the cable drum brake (33) is designed to be actuated by a lifting magnet (84), an electric motor, a pneumatic lifting cylinder and / or hydraulic lifting cylinder.

7. Cable length sensor (10) according to one of claims 2 to 6, characterized in that the EMF braking system (95) can generate a speed-dependent braking torque by short-circuiting all motor windings of the electric motor (14).

8. Cable length sensor (10) according to one of claims 2 to 7, characterized in that the control unit (31) is designed to control the EMF brake system (95), the cable drum brake (33) and / or the electric motor (14).

9. Cable length sensor (10) according to one of claims 2 to 8, characterized in that the EMF braking system (95) is designed to be automatically activated in the event of an interruption of a power supply and to remain activated over an entire voltage-free period.

10. Rope length sensor (10) according to one of the preceding claims, characterized in that the rope length sensor (10) has one or more interfaces (37) via which status information and operating states can be transmitted to higher-level control devices.

11. Rope length sensor (10) according to one of the preceding claims, characterized in that the rope length sensor (10) can be parameterized and controlled via one or more interfaces (37). Rope length sensor (10) according to claim 10 or 11, characterized in that the control unit (31) is configured to control all components with which it has a data connection and to provide data for higher-level control devices connected to the rope length sensor (10) via the interfaces (37) and to process data received via the interfaces (37). Rope length sensor (10) according to one of the preceding claims, characterized in that the rope length sensor (10) can be switched to different operating modes via the control unit (31) and / or one or more interfaces (37). Rope length sensor (10) according to one of the preceding claims, characterized in that a brushless electric motor (14) is provided as the drive (12). Rope length sensor (10) according to one of the preceding claims, characterized in that the electric motor (14) is provided as an external rotor motor.Cable length sensor (10) according to one of the preceding claims, characterized in that a motor controller (93) is provided, which is configured to control the electric motor (14) and preferably to regulate the motor speed, acceleration, and torque. Cable length sensor (10) according to claim 16, characterized in that the EMF braking system (95) is connected between the motor controller (93) and the electric motor (14).

18. Cable length sensor (10) according to one of the preceding claims 16 or 17, characterized in that the motor control (93) is in bidirectional data connection with the control unit (31).

19. Cable length sensor (10) according to one of the preceding claims, characterized in that the measured value sensor (20) is designed as an encoder in the electric motor (14) or outside the electric motor (14), wherein the encoder is mechanically connected to a motor shaft (60) included in the electric motor (14) and to the cable drum (42).

20. Cable length sensor (10) according to claim 19, characterized in that the encoder is in unidirectional data communication with the motor control (93).

21. Cable length sensor (10) according to one of the preceding claims, characterized in that the control unit (31) is designed as a microcontroller.

22. Method for the safe operation of a cable length sensor (10) according to one of the preceding claims, wherein a tear in the measuring cable (32), an uncontrolled retraction of the measuring cable (32) and / or a completely wound-up state of the cable drum (42) is detected via the control unit (31) and the braking system is then automatically activated.

23. Method according to claim 22, characterized in that the braking system comprises an EMF braking system (95) for braking the electric motor (14) and a cable drum brake (33), wherein after the detection of a tear in the measuring cable (32), an uncontrolled retraction of the measuring cable (32) and / or a completely wound-up state of the cable drum (42), the cable drum brake (33) and the EMF braking system (95) are activated simultaneously.

24. Method according to claim 23, characterized in that the tear in the measuring cable (32) and the completely wound-up state of the cable drum (42) are detected by a sensor system detecting a brake lever stroke of the cable drum brake (33) and transmitting it to the control unit (31). Method according to one of the preceding claims 22-24, characterized in that an uncontrolled retraction of the measuring cable (32) occurs when the cable retraction speed and / or the cable retraction acceleration exceeds a maximum limit value stored in the control unit (31), wherein the cable retraction speed and / or the cable retraction acceleration are determined by the rotation of the drive (12) detected by the sensor (20) via the control unit (31). Use of the cable length sensor (10) according to one of the preceding claims 1 - 21 in a non-operating mode, in particular for transport, wherein the electric motor (14) is in an inactive state and the braking system, in particular a cable drum brake (33) and an EMF braking system (95), is in an active state. Use of the cable length sensor (10) according to one of the preceding claims 2 - 21 for a reference run, wherein the measuring cable (32) is initially at least partially unwound from the cable drum (42), wherein the electric motor (14) and the cable drum brake (33) are in an active state and the EMF braking system (95) is in an inactive state, wherein operating values ​​of the cable length sensor (10) are set to a low cable retraction speed compared to normal operation and to a maximum cable retraction acceleration as well as to a maximum torque, wherein the reference run is preferably terminated automatically when the cable retraction speed corresponds to a value of 0 m / s and the torque and a time exceed a threshold value stored in the control unit (31). Use of the cable length sensor (10) according to one of the preceding claims 2 - 21 in an installation mode, wherein the measuring cable (32) is first at least partially unwound from the cable drum (42) by an operator, while the electric motor (14) is in an inactive state and the EMF braking system (95) and the cable drum brake (33) are in an active state; wherein the cable length sensor (10) automatically detects that the measuring cable (32) has been unwound from the cable drum (42) and then brings the EMF braking system (95) into an inactive state and the electric motor (14) into an active state and the torque of the electric motor (14) is increased so that the measuring cable (32) is retracted, wherein operating values ​​of the cable length sensor (10) are set to a cable retraction speed that is low compared to normal operation and to a maximum cable retraction acceleration as well as to a torque that is reduced compared to normal operation.Use of the cable length sensor (10) according to one of the preceding claims 1 - 21 in a normal operating mode, wherein the measuring cable (32) is initially at least partially unwound from the cable drum (42), wherein the electric motor (14) is in an active state and the braking system, in particular a cable drum brake (33) and an EMF braking system (95), is in an inactive state, wherein the operating values ​​of the cable length sensor (10) are set to a maximum cable retraction speed and to a maximum cable retraction acceleration and to a maximum torque.

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