This application claims the benefit of the European Patent Application EP 19383043.7 filed on November 26, 2019

The present disclosure relates to methods for controlling a brake of a traction system of an elevator cabin. The present disclosure further relates to brake release systems of a traction system of an elevator cabin and elevator systems having the brake release system.

BACKGROUND

Modern wind turbines are commonly used to supply electricity into the electrical grid. Wind turbines generally comprise a rotor mounted on top of a wind turbine tower, the rotor having a rotor hub and a plurality of blades. The rotor is set into rotation under the influence of the wind on the blades. The operation of the generator produces the electricity to be supplied into the electrical grid.

When maintenance works are required inside wind turbines, hoists are often used in the form of elevator-like structures where a lift platform or an elevator cabin for the transportation of people and/or equipment is hoisted up and/or down within the wind turbine tower. Wind turbines are often provided with working platforms arranged at various heights along the height of the tower with the purpose of allowing workers to leave the cabin and inspect or repair equipment where intended. These sorts of elevator systems are also known in other applications, such as e.g. factories, construction sites, cranes, silos, chimneys and all sorts of towers.

Elevator systems may include an elevator cabin suspended within a hoistway or elevator path by wire ropes. The term wire rope is herein used to denote a relatively thick cable. But in the art, the terms cables and wire ropes are often used interchangeably. In some systems, e.g. for some electric elevators, a counterweight may be provided depending on e.g. the available space. Other systems normally do not comprise a counterweight. In further examples, the elevator cabin may be driven by a rack and pinion arrangement. In these cases, the rack is usually provided along the elevator path and the pinion is usually arranged in the elevator cabin and a motor for driving the pinion may be mounted in or on the elevator cabin.

Elevator systems may additionally comprise taut lines or cables, a rail, a ladder or any other rigid guiding element extending all the way from the top to the bottom of the elevator path. These elevator systems are sometimes referred as “ladder-guided”, “mast-guided” or “cable-guided”. Such rigid structures provide stabilization to the elevator cabin and avoid horizontal displacement of the elevator cabin in long elevator paths, as for example in elevator systems of wind turbines.

The service elevators may comprise a driving system for lifting and lowering the elevator cabin. In some examples, the driving system may be a traction system involving the use of a traction wire or a traction chain. The traction system may comprise a housing including a driving or a traction mechanism, e.g. a motor driving a traction or driving sheave. The driving mechanism may be mounted on or attached to the elevator cabin. The motor may typically be an electrical motor, although in principle other motors could be used. The driving mechanism engages a traction wire or a traction chain for lifting and lowering the elevator cabin. The elevator cabins may therefore be supported by the traction wire or by the traction chain.

In other examples, the driving system may comprise a rack and a pinion system. A motor may drive a pinion which engages the rack for lifting and lowering the elevator cabin. The pinion may thus be a driving mechanism. In further examples, the driving system may comprise a drum hoist around which a wire may be wound and unwound.

The driving system of service elevators may further incorporate an electromagnetic brake. The electromagnetic brake may engage the driving mechanism to stop vertical movement of the elevator cabin. The electromagnetic brake may stop the rotation of the traction or driving sheave of the driving mechanism. The electromagnetic brake may generally comprise a brake spring pressing a brake shoe to block the rotation of the driving mechanism. In some examples, the brake shoe may block the rotation of the traction sheave, e.g. by engaging a shaft of the motor or the traction sheave. When electric energy is supplied to the electromagnetic brake, an electromagnetic magnet is energized for separating away the brake shoe or pad from the rotating member, e.g. the shaft of the motor or the traction sheave. Accordingly, the electromagnetic brake may stop the vertical movement of the elevator cabin when no power is supplied and may allow the vertical movement when energized. This may be a system to prevent the elevator cabin from unintentional descent during a power failure that disables the motor of the traction mechanism. Other systems or devices, e.g. fall arrest devices, may be additionally used for blocking the movement of the elevator cabin.

Some driving or hoisting systems may further comprise a speed descent control system to limit or control the descent speed of the elevator cabin. In some examples, the speed descent control system may comprise a centrifugal brake. The centrifugal brake is activated when the elevator cabin speed exceeds a predetermined limit value. This predetermined limit value may be higher than typical operating speed values. In some examples, the speed control system may comprise a capacitor brake system. The capacitor brake system may power the electrical motor for controlling the descent of the elevator cabin. In this example, the descent speed may be lower than the typical operating speed value.

In addition to this electromagnetic brake, a “secondary safety device” or “fall arrest device” can be mounted on or attached to the elevator cabin, directly or through supporting structures. Such a fall arrest device serves as a back-up for the main electromagnetic brake for example in case of failure of the service elevator or breakdown of the traction wire rope. The fall arrest device may typically incorporate some form of sensing mechanism to monitor the elevator’s speed. The secondary safety device or the fall arrest device may automatically block the elevator and inhibit any further downward movement if the sensing mechanism detects an overspeed of the elevator cabin, i.e. when the elevator cabin might be falling. The speed detection mechanism in this sense acts as an overspeed detector.

A hoisting wire rope of the service elevator or a dedicated safety wire rope may pass through an entry hole in the fall arrest device, through the interior of the fall arrest device and exit the safety device through an exit hole at an opposite end. Some form of clamping mechanism for clamping the hoisting wire rope or the safety wire rope when an unsafe condition exists (i.e. when the overspeed detector trips) may be incorporated in the safety device.

Blocking the safety device has to be fast enough for adequately stopping the elevator cabin when an overspeed is detected. Therefore, the fall arrest device needs to be precisely calibrated. Fall arrest devices are therefore periodically inspected to detect operation failures. Before using the elevator system, checking or testing the correct functioning of the fall arrest device may be required or at least recommended. In some examples, testing a fall arrest device may involve lifting the elevator from a departure platform few centimeters. Then the fall arrest device may be activated, for instance, by turning a lock lever inside the elevator cabin. The safety wire is thus clamped by the jaws and the fall arrest device thus blocks the safety wire. The user may activate a down button to make the cabin go down, but the service elevator should not descend. Then, the user may try to perform a manual descent by releasing the electromagnetic brake of the traction system. The fall arrest device should thus hold the load.

In some examples, testing a fall arrest device may comprise performing a drop test. In a drop test, a fall of the elevator cabin is forced to cause the activation of the fall arrest device. The speed control system, e.g. a centrifugal brake ora capacitor brake system, may be deactivated or dismounted. In addition, the electromagnetic brake may be released. Accordingly, the descent of the elevator cabin is allowed and the fall arrest device is triggered when a predetermined descent speed is reached.

A user, e.g. a wind turbine maintenance operator, may manually release the electromagnetic brake from inside the elevator cabin to allow descending the elevator cabin. This may occur during a power failure or in certain maintenance operations, e.g. testing a fall arrest device. The user may move a lever provided inside the elevator cabin to release the electromagnetic brake as to allow the elevator cabin to move to the ground or to a platform. The lever may be connected to the electromagnetic brake through a mechanical connection to counteract the force exerted by the spring. When the electromagnetic brake is released, e.g. in the open position, the speed descent control system, e.g. a centrifugal brake, may be used to prevent an excessive speed of the elevator cabin during an emergency-controlled descent.

In some examples, e.g. in systems having a centrifugal brake, descent speed during an emergency-controlled descend, i.e. after releasing the electromagnetic brake, may be higher than in normal operation. As the speed of the elevator cabin during an emergency-controlled descent may be higher than in normal operation, users may force the elevator cabin to perform a quicker descent by releasing the electromagnetic brake. This may produce a misuse of the traction system which may cause a premature wear in some components of the driving system, e.g. the centrifugal brake, as they are operating at a speed higher than the normal operation speed.

Furthermore, in wind turbines, descending from the nacelle to the ground may involve several minutes. Thus, the users forcing the release of the electromagnetic brake may keep the lever pushed or activated during several minutes. The user may get tired and the pushing force applied on the lever may be reduced after some time and, consequently, the electromagnetic brake may only be partially released. This may cause a premature wear in the electromagnetic brake, e.g. in the brake pad, and in the other components of the driving system.

In addition, during a power failure some safety sensors are not powered and, therefore, data provided by these safety sensors cannot be taken into account during an emergency-controlled descent. Accordingly, the elevator cabin may still descent in unsafe situations such as overload in the elevator cabin or with obstacle within the elevator path.

The present disclosure provides examples of systems and methods that at least partially resolve some of the aforementioned disadvantages.

Service elevators and related driving systems comprising electromagnetic brakes are not only used in wind turbine towers, but instead may be found in many different sites and tall structures, e.g. factories, construction sites or cranes. Elevator cabins or lifting platforms having these driving systems with electromagnetic brakes may also be used in building maintenance units for performing maintenance operations, e.g. cleaning, on a structure and in temporary suspended platforms for providing temporary access during the erection of a building or a structure.

SUMMARY

In a first aspect, a method for controlling a brake of a driving system for lifting and lowering an elevator cabin of an elevator system is provided. The method comprises operating a release switch to release the brake, determining an operating condition of the elevator system and comparing the determined operating condition with a predetermined operating condition. If the determined operating condition corresponds with the predetermined operating condition, then powering the brake with a power storage device to release the brake. The release switch may be operated by a user inside the elevator cabin.

According to this aspect, a user inside the elevator cabin may operate a release switch to deactivate the brake, e.g. an electromagnetic brake. However, an effective release of the brake is performed if the predetermined operating condition is met. Otherwise, the brake is not released regardless of the wish of the user. This may prevent the user from intentionally causing the release of the brake at any time. The brake may thus be released under certain conditions, therefore the release of the brake no longer relies only on the user’s force applied to the brake pads. Therefore, a misuse of the driving system may be avoided.

The predetermined operating conditions are those operating conditions or scenarios of the elevator system in which a manual descent can be allowed. For example, a predetermined operating condition may be a power failure or a maintenance operation.

As the brake may be released only in predetermined scenarios the number of activations of the speed descent control system, e.g. a centrifugal brake, may be reduced. Thus, the misuse of the driving system may be avoided and a premature wear in the centrifugal brake to limit the speed of the elevator cabin may be at least reduced. Hence, maintenance tasks may be reduced and safety may be enhanced.

The instruction to release the brake is performed by operating a release switch by a user inside the elevator cabin. The release switch may thus be operable by a user inside the elevator cabin. Variations of the force applied by the user to the release switch may not induce a partially release of the brake. Accordingly, as the release of the brake is no longer caused by the force of the user, a partial release of the brake may be prevented. So, a premature wear in the electromagnetic brake, particularly in the brake pad may be at least reduced. A premature wear in other components of the elevator system such as a guiding system may also be reduced. In addition, accuracy and reliability of controlling a brake may be improved.

Furthermore, as the power storage device may power the brake, e.g. an electromagnetic brake, the brake may be controlled independent from the power grid. For example, the brake may be released in a grid loss event.

In some examples, if the determined operating condition does not correspond with the predetermined operating condition, then brake is kept in an engaging position. Consequently, the elevator cabin cannot descend by releasing or opening the brake and the elevator cabin can only descend by operating the motor of the driving system, e.g. moving a driving sheave of a traction system, as the normal or standard operation of the elevator cabin. In some examples, e.g. when the driving system comprises a centrifugal brake, descent’s speed may be lower when the movement is caused by a normal operation than when a manual descent is performed.

The driving system may be a traction system or rack and pinion system. The driving system may comprise a driving mechanism arranged on or in the elevator cabin.

In some examples, the method may comprise receiving data from one or more safety sensors. Based on this data an unsafe condition of the elevator system may be determined. If an unsafe condition is determined, the brake may be maintained in an engaging position, preventing the movement of the elevator cabin. Therefore, the descent of the elevator cabin may be performed in a safety manner.

The safety sensors may comprise for example at least one of: a door lock sensor, an overload sensor, a bottom obstruction device, an ultimate top limit switch. These safety sensors may be self-powered or may be powered by a power storage device. The power storage device may be a dedicated power storage device for one or for a group of safety sensors or maybe the power storage device powering the brake. Accordingly, safety sensors may be taken into account during a manual descent. Safety of a manual descent is improved, even in grid loss events.

In some other examples, the method may comprise determining a brake release time indicative of a time during which the brake is released. The determined brake release time may be compared with a predetermined brake release time or a predetermined brake release time threshold. If the brake release time is equal or higher than the predetermined brake release time, then positioning the brake in an engaging position for blocking the elevator cabin.

In some examples, the brake release time may be determined for a single manual descent. In this way, long manual descents, e.g. from a nacelle of a wind turbine to a ground, may be prevented in some conditions. In some examples, the brake release time may be the accumulated brake release time from a period of time, e.g. from the installation of the brake pads. Thus, the lifespan of the brake pad may be enhanced and so the release of brake may be achieved under safer conditions. The elevator system may comprise a timer to measure the brake release time for a single manual descent or an accumulated brake release time, e.g. for several manual descents. The timer may be integrated in a controller. In a further aspect, a brake release system of a driving system for lifting and lowering an elevator cabin of an elevator system is provided. The brake release system comprises a brake for blocking a movement of the elevator cabin, a power storage device to power the brake and a release switch for releasing the brake, the release switch being in communication with a controller. The release switch may be operable by a user inside the elevator cabin. The brake release system further comprises a controller configured to determine an operating condition of the elevator system, compare the determined operating condition with a predetermined operating condition and instruct the power storage device to power the brake for releasing the brake if the determined operating condition corresponds with the predetermined operating condition.

Advantages derived from this second aspect may be similar to those mentioned regarding the method of the first aspect. Namely, the brake release system may prevent a misuse of the brake as the brake system can only be disengaged under certain conditions.

In a further aspect, the present disclosure provides an elevator system. The elevator system comprises an elevator cabin, a driving system having a driving mechanism supported by the elevator cabin for driving the elevator cabin along an elevator path, and a brake release system according to any of the examples herein described.

Advantages derived from this further aspect may be similar to those mentioned regarding the method of the first aspect.

In another aspect, the present disclosure provides a wind turbine tower comprising an elevator system according to any of the examples herein described.

Throughout the present disclosure, expressions such as above, below, beneath, under, upper, bottom, lower, etc are to be understood taking into account the construction of an elevator or the like in an operating condition as a reference.

Throughout the present disclosure, a switch is to be understood as a button, a selector, or any kind of user interface device to send a command to a controller. In this sense, a release switch may a button, a selector, or any kind of user interface device to send a command to release the brake to a controller. The release switch may be operable by a user located inside the elevator cabin. Throughout the present disclosure, manual descent or an emergency-controlled descent is to be understood as a lowering operation of the elevator cabin along the elevator path by releasing a brake.

Throughout the present disclosure, elevator cabin means any type of platform, basket or cabin that is used for lifting or lowering people along structures or towers. An elevator system means a system comprising an elevator cabin according to any of the examples herein disclosed which may be lifted and lowered.

Throughout the present disclosure, an elevator path is to be understood as a space, passage or trajectory through which the elevator cabin or the like may travel upwards and downwards. In a wind turbine tower, the elevator path is thus defined inside the tower. There may be a closed space inside the tower along which an elevator cabin travels. Alternatively, the space inside the tower through which the elevator travels may be open.

BRIEF DESCRIPTION OF THE DRAWINGS Non-limiting examples of the present disclosure will be described in the following, with reference to the appended drawings, in which:

Figure 1 schematically illustrates a view of one example of a wind turbine; Figure 2 schematically illustrates a partial view of an elevator system according to an example of the present disclosure;

Figure 3 schematically illustrates schematically illustrates a partial view of a traction system according to an example of the present disclosure;

Figure 4 schematically illustrates a brake release system according to an example of the present disclosure; and

Figure 5 shows a flowchart of a method for controlling a brake of a traction system according to one example of the present disclosure.

DETAILED DESCRIPTION OF EXAMPLES In these figures, the same reference signs have been used to designate matching elements. Some parts have not been illustrated for the sake of clarity. Also for an enhanced comprehension of the present disclosure, the elevator path EP will be illustrated in the attached figures as a longitudinal axis in a direction followed by an elevator cabin 22 or other similar suspended platform as it moves upwards or downwards in operation. Although the examples of the present disclosure have been described related to a wind turbine tower, the present methods and systems are not limited to that purpose and could be used in other applications such as e.g. factories, construction sites, cranes, silos, chimneys and all sorts of towers or structures. Figure 1 schematically illustrates a view of one example of a wind turbine 100. As shown, the wind turbine 100 comprises a tower 101, a nacelle 103 mounted on the tower 101, a hub 104 coupled to the nacelle 103 and some blades 102 coupled to the hub 104. Inside the nacelle 103 a generator can produce electrical energy as will be apparent to those skilled in the art. Power and communication cables for transmitting electric power and signals from or to the generator may run through the interior of the tower 101. The wind turbine tower 101 may comprise an elevator system 20 according to any of herein disclosed examples. Particularly, Figure 2 schematically illustrates a partial view of an elevator system 20 according to an example. The elevator system 20 of Figure 2 comprises an elevator cabin 22, a traction system

23 having a driving mechanism 40 supported by the elevator cabin 22 for driving the elevator cabin along an elevator path EP. The elevator cabin 22 of Figure 2 is wire- guided by guide wires 21. The elevator system 20 comprises a brake release system 10. The brake release system 10 may correspond to any of the herein disclosed examples. Details about the release system 10 will be set forth later on. Instead of a traction system, the driving system may be a rack and a pinion system.

As per Figure 3, the traction system 23 may comprise a traction wire 24 and the driving mechanism 40 may engage with traction wire 24. In some examples, a traction chain may be used rather than a traction wire. In another not illustrated example, the driving system may comprise a rack and a pinion engaging with the rack. The driving mechanism 40 may comprise a motor 41 such as an electric motor, which may drive a driving sheave 42 through a gearbox 43. The driving mechanism 40 may further comprise a centrifugal brake 31 installed between the motor 41 and the gearbox 43, and an electromagnetic brake 14. The driving sheave 42 will be linked to the traction wire as already known in the art. In some examples, instead of a centrifugal brake, other types of speed descent control system such as a capacitor brake system may be used.

The electromagnetic brake 14 may engage a rotating part of the of the driving mechanism. This rotating part may be a shaft of the motor, a gear or a shaft of the gearbox or a driving sheave. The electromagnetic brake may comprise a brake spring pressing a brake shoe or pad to engage the rotating part, e.g. the shaft of the motor. The electromagnetic brake 14 may comprise an engaging position in which the rotation of the driving mechanism is blocked and a releasing position in which the driving mechanism can rotate. In traction systems, the rotation of the driving sheave is blocked in the engaging position and can rotate in the releasing position. Accordingly, when power is supplied to the electromagnetic brake, the electromagnetic brake is released, and the driving mechanism, e.g. traction sheave, may rotate causing a vertical movement of the elevator cabin. On the contrary, when no power is supplied to the electromagnetic brake, brake pads block the driving mechanism, e.g. the traction sheave, preventing a vertical movement of the elevator cabin.

The exemplary elevator system 20 may further comprise one or more safety sensors in communication with the controller 12 and a power storage device 13. In some examples, the safety sensors may be powered by a dedicated power storage device. For example, an independent or dedicated battery may power a one or a plurality of safety sensors.

The safety sensors of this example comprise at least one of an overload sensor 31 , a bottom obstruction device 32, an ultimate top limit switch 33 and a door lock sensor 34. These types of safety sensors are briefly discussed in the following.

The overload sensor 31 may be connected to the driving system. If an overload is detected, the driving system may prevent a vertical movement of the elevator cabin. The overload sensor may be connected to the controller to control the power delivered to the brake.

The bottom obstruction device 32 may interrupt descent if the cabin or other similar suspended platform encounters an obstacle or touches the ground so as to minimize or prevent impact with the person or object.

The emergency or ultimate top limit switch 33 indicates that elevator cabin has reached the maximum allowed height. The ultimate top limit switch may interrupt ascent and descent when activated. When the top ultimate limit switch is activated or engaged only manual descent may be possible.

The door lock sensor 34 may be configured to monitor whether the door of the elevator cabin is closed or not. If the door is not closed, the elevator cabin is not allowed to move along the elevator path EP. In some examples, the door lock sensor may further control if the door is locked.

Furthermore, the elevator system 20 may also have more safety sensors than those described above. These safety sensors may be located in several devices and places such as hatches or windows locks of the cabin, or in a so-called “catwalk” platform. “Catwalk” platform is an extendable platform which may be installed in front of the cabin, under a sliding door, in order to make safer the evacuation procedure. The “catwalk” platform may have a safety switch that, when is extended, prevents the cabin from moving. The safety switch of the catwalk may be fed by the power storage device 13.

The elevator system 20 may further comprise a fall arrest device 35 connected to the elevator cabin 22. The fall arrest device may be comprised in cable-guided elevator systems and in rack and pinion systems. The fall arrest device may comprise an overspeed detector and a blocking system for blocking the elevator cabin when an overspeed is detected by the overspeed detector. The blocking system may be manually activated, e.g. for testing the fall arrest device, and may be connected to the controller 12. As the fall arrest device may be in communication with the controller 12, an operating condition of testing a fall arrest device may be determined or detected by the controller.

Figure 4 schematically illustrates a brake release system 10 according to an example. The brake release system 10 of this figure comprises a brake 14 for blocking a movement of the elevator cabin 22. The movement of the elevator may be upwards or downwards along the elevator path EP. The brake may be an electromagnetic brake according to any of the examples herein disclosed. The brake release system of Figure 4 further comprises a power storage device 13 to power the brake 14. The power storage device may be a battery, a supercapacitor or the like, that may feed the electromagnetic brake 14. The power storage device may also power other components of the brake release system or of the elevator system. For example, the power storage device may power a safety sensor, e.g. an overload sensor 31 , a bottom obstruction device 32, an ultimate top limit switch 33 or a door lock sensor 34. In this figure, the brake release system comprises a brake release switch 11 to release the brake. The brake release switch 11 may be in communication with a controller 12. The release switch may thus send a command or instruction to the controller for releasing the brake. The release switch 11 may be a button, a hold-to-run device, a selector, a returnable selector or any user interface device to send a command to the controller. The release switch may be arranged inside the elevator cabin. The release switch may thus be operable by a user inside the elevator cabin. In some examples, the release switch may be arranged at a user’s control box. The user’s control box may be arranged inside the elevator cabin. The user’s control box may comprise buttons and/or switches to control the operation of the elevator system.

The controller 12 of this figure is configured to determine an operating condition of the elevator system 20, compare the determined operating condition with a predetermined operating condition, and instruct the power storage device 13 to power the brake 14 for releasing the brake, if the determined operating condition corresponds with the predetermined operating condition.

The controller 12 may be a hardwired controller. A hardwired controller may comprise combinational logic units that generates control signals. The control logic may be implemented with gates, flip-flops, decoders, and other digital circuits. The hardwired controller may comprise switches connected through cables. Hardwired controller may be more robust than other types of controller.

The controller 12 may be configured to carry out any of the methods disclosed herein. The controller may thus disable a command performed by the user if a predetermined condition is not met.

The controller 12 may include one or more processor(s) and associated memory device(s) configured to perform a variety of computer-implemented functions (e.g., performing the methods, steps, calculations and the like and storing relevant data as disclosed herein). The controller 12 may perform various different functions, such as receiving, transmitting and/or executing control signals and controlling the overall operation of the brake release system. The controller may be programmed to control the overall operation based on information received from the dedicated sensors like those hereinbefore mentioned. Thus, the controller 12 may be in communication with, at least, safety sensors and the power storage device 13.

As used herein, the term “processor” refers not only to integrated circuits referred to in the art as being included in a computer, but also refers to a controller, a microcontroller, a microcomputer, a programmable logic controller (PLC), an application specific integrated circuit, and other programmable circuits. The processor is also configured to compute advanced control algorithms and communicate to a variety of Ethernet or serial-based protocols (Modbus, OPC, CAN, etc.). Additionally, the memory device(s) may comprise memory element(s) including, but not limited to, computer readable medium (e.g., random access memory (RAM)), computer readable non-volatile medium (e.g., a flash memory), a floppy disk, a compact disc-read only memory (CD- ROM), a magneto-optical disk (MOD), a digital versatile disc (DVD) and/or other suitable memory elements. Such memory device(s) may be configured to store suitable computer-readable instructions that, when implemented by the processor(s), configure the controller to perform the various functions as described herein.

In some examples, the controller 12 may a dedicated controller to control the operation of the brake release system. In some examples, the controller 12 may be a main controller controlling the operation of the elevator system.

The controller 12 of this figure is communicatively coupled to the overload sensor 31, to the bottom obstruction device 32, to the ultimate top limit switch 33 and to the door lock sensor 34. The controller may be further in communication with the fall arrest device 35 to e.g. detect a maintenance condition of testing the fall arrest device.

In some examples, the controller 12 may be connected to an electrical grid to monitor the power supply. The connection to the electrical grid will be apparent for those skilled in the field, so no further details will be provided.

In some examples, the controller 12 may be further configured to keep the brake 14 in engaging position if the determined operating condition does not correspond with the predetermined operating condition, and so the cabin is not allowed to move upwards or downwards. In some examples, the controller may be further configured to bring the brake into an engaging position if the determined operating condition does not correspond with the predetermined operating condition, and so the elevator cabin is no longer allowed to move upwards or downwards. These may be performed by controlling the power delivered by the power storage device to the brake.

Figure 5 shows a flowchart of a method 200 for controlling a brake of a driving system according to one example of the present disclosure. The method 200 for controlling a brake 14 of a driving system 23 for lifting and lowering an elevator cabin 22 of an elevator system 20 is disclosed in Figure 5. The driving system may be a traction system having a driving mechanism engaging with a traction cable. The method comprises operating 201 a release switch 11 to release the brake 14. The user actuates the release switch to perform a so-called “manual descent”. The user may actuate the release switch from inside the elevator cabin. The method further comprises determining 202 an operating condition of the elevator system, comparing 203 the determined operating condition with a predetermined operating condition. In addition, the method comprises powering 204 the brake with the power storage device 12 to release the brake 14, when the determined operating condition corresponds with the predetermined operating condition.

In an example, if the determined operating condition does not correspond with the predetermined operating condition, the method 200 may then comprise keeping the brake in an engaging position. Accordingly, the brake is released when the elevator system is in a predetermined operating condition.

In some examples, the predetermined operating condition may comprise a power failure. A power failure may comprise a power cut off, a thermal sensor activation, an electrical protection activation and/or any other to cut the power supply from the grid. The power failure condition may involve an evacuation to a bottom departure platform of the tower. The user inside the cabin 22 may operate the release switch 11 with the aim of disabling the brake 14 and causing a descent of the cabin. The release switch may thus be operable by a user inside the elevator cabin. Then, the controller 12 may receive the command and check whether the power failure operating condition is met. For instance, the controller 12 may receive data from a sensor to monitor the power supply to the cabin. If the power failure operating condition is met, the controller 12 may send a command to the power storage device 13 to power the brake 14. Brake 14 may then be released and the cabin may move downwards. Therefore, when a user operates a release switch to release the brake and a power failure is determined, the power storage device powers the brake, e.g. an electromagnetic brake, to release or open the brake.

In some examples, the predetermined operating condition may comprise a maintenance operation. Accordingly, a manual descent may be allowed if a predetermined maintenance operation is determined.

In some examples, the maintenance operation may comprise testing a fall arrest device of the elevator system, for example a daily test of the fall arrest device 35. The test may be performed as usual except for the manual brake release.

In some examples, when the fall arrest device 35 is activated to clamp the safety wire, an input may be received by the controller 12 from a sensor or the like linked to the fall arrest device. This way the controller 12 may determine that a fall arrest device test is being performed. As testing a fall arrest device may be one of the predetermined operating conditions, a release of the brake may be permitted. The user may operate the release switch 11 and the controller 12 may send a command to the power storage device to feed the brake 14. The brake may be released and the load of the cabin may be held by the fall arrest device 35 to check that the fall arrest device is working properly.

In some examples, e.g. in a drop test of a fall arrest device, the controller may determine that testing a fall arrest device is performed or is going to be performed. The controller may thus allow the power storage device to feed the brake. The elevator cabin may consequently descend in an emergency descent to force the activation of the fall arrest device.

In some examples, the maintenance operation may comprise resetting an ultimate top limit switch. An input may be received by the controller 12 if the ultimate top limit switch 33 is triggered. This way the controller 12 may determine that the ultimate top limit switch has been triggered. The controller may determine that resetting the ultimate top limit switch is being performed or is to be performed. As resetting the ultimate top limit may be one of the predetermined operating conditions, the controller may allow releasing the brake. The user may operate the release switch 11 and the controller 12 may send a command to the power storage device to feed the brake. The brake may be released and the cabin may descend in spite of the ultimate top limit switch 33. When the cabin moves downwards the ultimate top limit switch 33 may recover its no- triggered condition and so the ultimate top limit switch 33 may be reset. Consequently, the cabin can only be allowed to move along the elevator path EP in the normal operation.

The method 200 may further comprise receiving data from one or more safety sensors. Based on this received data, an unsafe condition or a safe condition of the elevator system 1 may be determined.

The one or more safety sensors may comprise at least one of: a door lock sensor, an overload sensor and a bottom obstruction device.

According to an example, the method 200 may further comprise keeping the brake 14 in an engaging position if an unsafe condition is determined and so the cabin 22 may be prevented from moving downwards or upwards. The method 200 may further comprise bringing the brake 14 into an engaging position if an unsafe condition is determined to stop the cabin.

The unsafe condition may be determined by the controller 12 on the basis of data received from one or more safety sensors. By way of example, in an unsafe condition, the controller may prevent the release of the brake 14 or may cut the power fed to brake 14.

If the controller 12 receives data from safety sensors related to a safety issue such as overload, it may determine an unsafe condition. Thus, the power storage device 13 does not feed the brake 14 and the brake 14 may remain engaged. The controller 12 may also receive data related to the safety issue when the cabin 22 is already in motion. By way of example, the bottom obstruction device may detect an obstacle in the elevator path EP and send corresponding data to the controller 12. Then, the controller 12 may send a command to the power storage device 13 to stop powering the brake 14. This way, the brake 14 may go back to the engaged condition and the elevator cabin may stop.

Controller 12 may receive data from safety sensors in any of the predetermined operating conditions, so that brake could not be fed in case of an unsafe condition of the elevator system is determined when the elevator system is operating according to any of the examples of predetermined conditions herein disclosed.

When a safe condition is determined, the brake 14 may be released or may be kept in a released position and so the cabin 22 may move downwards.

The brake 14 may be in an engaging position before operating the switch to release the brake or may be in a disactivated position.

The method may further comprise determining a brake release time indicative of a time during which the brake is released. The determined brake release time may be compared with a predetermined brake release time or a predetermined brake release threshold. If the brake release time is equal or higher than the predetermined brake release time, then positioning the brake in an engaging position for blocking the elevator cabin. Positioning the brake in an engaging position may comprise powering the brake 14 with the power storage device 13 to release the brake 14. The controller 12 may be configured to measure time or duration of brake release and compare this time with a predetermined brake release time. If the determined time is lower than the predetermined brake release threshold then the brake 14 may be powered. If the determined time is equal to or higher, then brake 14 may not be powered. In some examples, the controller 12 may compute accumulated time of each release. If the accumulated time is lower than threshold then the brake 14 may be powered. If the accumulated time is higher than threshold then powering the brake 14 is prevented.

Although only a number of examples have been disclosed herein, other alternatives, modifications, uses and/or equivalents thereof are possible. Furthermore, all possible combinations of the described examples are also covered. Thus, the scope of the present disclosure should not be limited by particular examples, but should be determined only by a fair reading of the claims that follow. If reference signs related to drawings are placed in parentheses in a claim, they are solely for attempting to increase the intelligibility of the claim, and shall not be construed as limiting the scope of the claim.