Elevator and method for terminating a maintance trip of an elevator

Abstract

The present disclosure concerns a method for terminating a maintenance trip of an elevator (1), the method including providing a maintenance trip termination command and, in response to the maintenance termination command, executing a maintenance trip termination routine, the maintenance trip termination routine including: a) controlling a hoisting motor (13.1) of a drive (13) to decelerate a car (11) in a controlled manner, b) upon standstill of the car (11), controlling a brake (13.2) of the drive (13) to change from a non-activated state into an activated state while controlling the hoisting motor (13.1) to provide a holding torque, c) controlling the hoisting motor (13.1) to reduce the holding torque, in particular in a continuous manner, while monitoring whether the car (11) is moving, and, only if a movement of the car (11) is detected in step (c), d) executing a safety parking routine, the safety parking routine including moving the car (11) into a safety parking position, deactivating the power supply of the hoisting motor (13.1) and blocking the elevator (1).

Description

[0001] ELEVATOR AND METHOD FOR TERMINATING A MAINTANCE TRIP OF AN ELEVATOR

[0002] The present disclosure is related to the field of elevators, control units for elevators and the controlling of maintenance trips of an elevator, in particular terminating a maintenance trip of an elevator.

[0003] During regular operation with passengers, an elevator is generally controlled via a car operation panel (COP) in the car and / or landing operation panels (LOPs) that are arranged outside the hoistway at the floors, typically next to the hoistway doors. In regular operation, an elevator is generally controlled to operate in a smooth, safe, and efficient manner, while providing a high comfort level for the passengers.

[0004] Alternatively, however, elevators can be operated in a dedicated maintenance mode for carrying out maintenance trips. Maintenance trips are as a matter of routine required during installation and service. The maintenance mode needs to be activated by a user action of an authorized person, such as an installation and / or service technician. In the maintenance mode, the elevator is controlled via a dedicated maintenance control panel that is typically arranged on the car top. For a maintenance trip, the person doing the maintenance trip can also be positioned on the car top, while the car itself is empty. Typically, maintenance trips are mainly controlled via three pushbuttons, namely an activation pushbutton (also known as enable button) and two direction pushbuttons for the upwards direction and the downwards direction, respectively. A maintenance trip is started by simultaneously operating the activation pushbutton and either of the direction pushbuttons. The maintenance trip continues as long as both of the pushbuttons are operated. If either of the pushbuttons is released, the maintenance trip is stopped immediately. The power supply of the hoisting motor is interrupted respectively deactivated, typically by releasing contactors in the power supply, and a brake of the elevator drive (also referred to as machine brake) is activated. In this way, the car is not stopped smoothly as it is the case in regular operation, but in an abrupt manner.

[0005] This way of terminating a maintenance trip, however, is not unproblematic. The abrupt stopping results in significant stress for various elevator components, far beyond the limits in regular operation. The wear of the corresponding elevator components is accordingly increased, and the lifetime reduced. Under adverse conditions, a defect may directly occur. EP3613691B1 discloses a method for terminating a maintenance trip with a soft stop in an advantageous and smooth manner. Here, the drive and accordingly the car are not stopped abruptly, but in a controlled manner. Thereby, the mechanical stress on the elevator is reduced and the comfort and safety of the person doing the maintenance trip are increased.

[0006] However, there remains a risk that results from a potential brake failure. If a maintenance trip is terminated by releasing the pushbuttons as mentioned before, the power supply of the hoisting motor is immediately interrupted, and the brake is activated as mentioned. Subsequently, the car is held in position and prevented from moving exclusively by the brake. In very rare cases, however, the brake may fail to provide the required braking force.

[0007] Such failure may be caused by a technical defect of the brake. More likely, however, is the presence of grease, oil or generally friction-reducing dirt on a brake disk. For large elevators with hydraulically actuated brakes a rupture or leakage in the hydraulic system may result in an uncontrolled spreading of hydraulic fluid. Further, also for electromagnetically actuated brakes as present in most elevators, grease, or oil of the lubrication of the drive bearings may spread in an uncontrolled manner, e.g., due to a lack of awareness when lubricating the bearings during maintenance work or resulting from a rupture or leakage of an automated lubrication system.

[0008] If the brake cannot provide the required holding torque, the car may generally start moving in an uncontrolled and accelerated manner under the influence of gravity at the end of the maintenance trip. This may cause a significant risk of injury for the person on the car top. It is noted in this context that for a typical elevator design with a car and a counterweight, such uncontrolled movement of the car is normally an upwards movement since the counterweight is generally heavier than the car with a single person.

[0009] It is an overall objective of the present disclosure to improve the elevator safety for maintenance trips in the event of a brake failure.

[0010] In an aspect, the overall objective is achieved by a method for terminating a maintenance trip of an elevator. The method may include providing a maintenance trip termination command. The method may further include, in response to the maintenance trip termination command, execut- ing a maintenance trip termination routine. The maintenance trip termination routine may include the steps of: a) controlling a hoisting motor of a drive to decelerate a car in a controlled manner, b) upon standstill of the car, controlling a brake of the drive to change from a non-acti- vated state into an activated state while controlling the hoisting motor to provide a holding torque, c) controlling the hoisting motor to reduce the holding torque, in particular in a continuous manner, while monitoring whether the car is moving, and, only if a movement of the car is detected in step (c), d) executing a safety parking routine, the safety parking routine including moving the car into a safety parking position, deactivating the power supply of the hoisting motor and blocking the elevator.

[0011] Step (d) is accordingly not executed if no movement of the car is detected in step (c).

[0012] The steps of a method in accordance with the present disclosure may be executed in the indicated sequence and without time overlap. This is generally assumed in the following. In some embodiments, however, a time overlap may be present and / or the step order may be altered.

[0013] Further it is assumed that at the beginning of the method the elevator is carrying out a maintenance trip, in particular according to a routine as generally known and explained above and further below. The car of the elevator typically moves with a velocity that is suited for maintenance trips. A typically present safety chain is assumed to be closed respectively uninterrupted while the car of the elevator is carrying out the maintenance trip.

[0014] In a further aspect, the overall objective is achieved by a control unit. The control unit may be configured to receive a maintenance trip termination command and to control, in response to the maintenance trip termination command, the execution of a maintenance trip termination routine according to any embodiment as discussed above and / or further below.

[0015] In a further aspect, the overall objective is achieved by an elevator. The elevator includes a hoistway, a car, a counterweight, a drive and a control unit. The car and the counterweight are arranged vertically movable in the hoistway. The car and the counterweight are coupled via a flexible traction member and are suspended by the traction member, The drive is coupled to the traction member for moving the traction member and thereby the car and the counterweight. The control unit is configured in accordance with the present disclosure as explained before and further below.

[0016] In a further aspect, the overall objective is achieved by a method for executing a maintenance trip of an elevator. The method may include controlling a hoisting motor of drive to move a car in a hoistway, in particular at constant velocity. The method may further include a person providing a maintenance trip termination command and executing a maintenance trip termination routine in accordance with any embodiment as discussed above and / or further below.

[0017] Steps (a) and (b) of the maintenance trip termination routine generally correspond to the termination of a maintenance trip with a soft stop according to the disclosure of EP3613691B1. In step (c) it is tested in accordance with the present disclosure whether the brake provides a sufficient braking force to maintain the car at standstill, i.e., without moving, while the drive is still active, but the hoisting motor generates continuously less holding torque. If the holding torque can be fully removed without the car moving, it is ensured that the required holding force is provided by the brake. The maintenance trip termination routine being successfully and safely completed may in an embodiment be indicated to the person, e.g., optically by means of an indicator light. In a particular embodiment, a maintenance trip indicator light is generally on during the maintenance trip and is switched off upon successful termination of the maintenance trip, in particular at the end of step (c), or vice versa.

[0018] If, on the other hand, the car starts moving as the holding torque is reduced, the brake provides an insufficient or no braking force, and the safety parking routine is executed. If such movement of the car is observed, step (c) is generally directly terminated and executing the safety parking routine in step (d) is initiated. It is noted that the movement of the car refers to a significant vertical movement in the hoistway, rather than minor vibrations or the like.

[0019] The safety parking position is a position of the car that can be maintained in a stable manner without the hoisting motor applying any torque and without the brake applying any braking force. As discussed further below, the safety parking position is an uppermost position of the car in the hoistway for a typical elevator installation, as generally assumed in the following. It is noted, however, that for a different elevator design the safety parking position may be different, in particular a lowermost position of the car in the hoistway. This would be the case, e.g., if the car is exceptionally heavier than the counterweight or for an elevator without counterweight.

[0020] It is noted that the person is present on the car top when the safety parking routine is executed. For the movement into the safety parking position, the hoisting motor is generally controlled to move the car with a velocity that is safe and sufficiently comfortable for the person, for example the typical velocity for maintenance trips. In the safety parking position, the person is generally trapped on the elevator top. As the safety parking routine is completed, the person can call for help to be released respectively rescued, e.g., using a cell phone and / or readily installed alarm equipment in the elevator hoistway, in particular the headroom. Also, a control element for providing an alarm, such as an alarm pushbutton, is typically present on the cartop, e.g., on the maintenance control panel. In an embodiment, a corresponding alarm notification is automatically sent, e.g., to a responsible unit, such as an operation center of the elevator manufacturer or a service provider who responsible for the elevator maintenance.

[0021] Blocking the elevator when the car has reached the safety parking position in particular includes maintaining the hoisting motor of the car in a deenergized state and ensuring that no power can be provided to the hoisting motor and generally the elevator cannot be put into operation again without dedicated user action of a qualified person such as a service technician.

[0022] Deactivating the power supply of the hoisting motor generally is done by respectively includes interrupting the power supply to a hoisting motor drive circuit, such as an inverter and / or frequency converter. For this purpose, the power circuitry of an elevator generally includes electromechanical switching devices, in particular contactors, in the power supply of the motor drive circuit. For safety reasons and in accordance with applicable regulations, a serial arrangement with two contactors may be foreseen, thereby providing redundancy. The corresponding contactor arrangement is referred to as contactor unit. The power drive circuit as such, however, may generally remain active and in standby. At the end of the safety parking routine, however, the motor drive circuit may be switched off.

[0023] The brake of the drive is designed as known in the art and typically acts on a motor shaft of the hoisting motor via a brake disk. The brake is generally passively biased into an active respectively engaged state where braking force is applied by way of springs. To be kept in a non-acti- vated or open state where no braking force is applied, an opening force needs to be permanently provided. The opening force acts against the force applied by the springs. For this purpose, an electromagnet is foreseen in some typical designs. The brake is accordingly in the activated state if the electromagnet is not energized and is in the non-activated state if the electromagnet is energized. Alternatively, however, the opening force may be provided differently, in particular hydraulically. The brake may in particular be a caliper brake with a brake disk on the drive shaft of the hoisting motor. It is further noted that for safety reasons and to meet applicable regulations, redundancy is typically foreseen by providing two separate and in particular separately actuated brake assemblies that are generally controlled in parallel. For the sake of conciseness, however, reference is generally made simply to a (single) brake throughout this document. Such brake may include one, two or more brake assemblies as mentioned.

[0024] It is noted that when initiating the safety parking routine in step (d), the brake is generally in the activated state from step (b). While it cannot provide sufficient braking force, it may still provide some braking force that would counteract the movement into the safety parking position. This can be avoided by bringing the brake into the non-activated state first. In an embodiment, the safety parking routine includes, prior to moving the car into the safety parking position, controlling the brake to change into the non-activated state.

[0025] In an embodiment, the safety parking routine includes providing an acoustical and / or optical alert by way of an alerting device. Such alert notifies the person on the cartop regarding the safety parking routine. The alert is favorably provided directly at the beginning of the safety parking routine and may be provided continuously as the car moves into the safety parking position. Optionally, the alert may be provided first and the movement of the car into the safety parking position may be started with some delay. This delay allows the person to alter its position and / or posture as required in the interest of safety before the car starts moving into the safety parking position. For providing an optical alert, a safety parking indicator light or the like may be foreseen at the maintenance control panel as alerting device. Also, the termination of the safety parking routine at which the car is in the safety parking position and the elevator is blocked may be indicated to the person. This may be done, e.g., by switching of the safety parking indicator light, or via a further indicator light.

[0026] In an embodiment, step (b) includes monitoring a state of the brake via a brake sensor. Step (c) is only executed upon the brake sensor indicating that the brake is in the activated state. Such brake sensor, e.g., in the form of an electrical contact sensor, optical sensor or magnetic sensor is generally foreseen at state-of-the art elevator brakes. Alternatively, subsequent step (c) may be executed with some delay after controlling the brake to change into the activated state, with the delay corresponding at least to the time required for the brake to change from the non-acti- vated into the activated state.

[0027] In an embodiment, monitoring whether the car is moving includes evaluating an encoder signal of an encoder coupled to a rotor of the hoisting motor. Such encoder is typically present. Any movement of the car is generally linked to a corresponding proportional rotor movement. Therefore, the rotor movement can serve as auxiliary measure for the car movement. In alternative embodiments, however, other types of sensors, such as a linear optical and / or magnetic encoder that directly measures the position of the car in the hoistway, or an, e.g., laser-optical distance sensor may be foreseen for monitoring whether the car is stationary respectively for detecting a car movement. Further, in dependence of the overall drive and control design, so-called sensorless measurement of the rotor movement respectively rotor position may be foreseen, based on electrical measurements at the hoisting motor. Corresponding designs and methods are known in the art. Further, a motion sensor, in particular an acceleration sensor at the car may be used.

[0028] In an embodiment, the safety parking routine includes, prior to moving the car into the safety parking position, controlling the hoisting motor to stop the movement of the car by providing a braking torque. Such design is favorable in that it ensures that the uncontrolled movement resulting from the lacking braking force is stopped and the car is stabilized prior to moving it into the safety parking position. In an embodiment, the braking torque is provided immediately at the beginning of the safety parking routine and an alert is provided as explained before, while the movement of the car into the safety parking position only starts with some delay.

[0029] In an embodiment, the car is in an uppermost position within a hoistway and a counterweight of the elevator is in a lowermost position and rests on a bumper in the safety parking position. This is the typical case for a standard elevator design where the car and a counterweight are coupled via a flexible traction member, such as one or more ropes or belts. The flexible traction member is, in turn, driven by the elevator drive respectively the hoisting motor. As the elevator is operated, the car and the counterweight move vertically in the hoistway in each case in opposite directions. Since the weight of the counterweight typically corresponds to the car plus half of the maximum payload and is especially heavier than the empty car plus a single person. Therefore, without any driving torque and without braking force, the counterweight will accordingly assume the lowest possible position, which is the position where it rests on the bumper that is generally present at the ground of the hoistway. The car will accordingly be in an uppermost position.

[0030] In an embodiment, the method includes, if the holding torque is fully removed in step (c) without a movement of the car being detected, deactivating a power supply of the hoisting motor. It is noted that for a typical elevator control design in accordance with the state of the art the power supply of the hoisting motor is in any case deactivated respectively interrupted if the person doing the maintenance trip releases the corresponding control elements. However, automatically deactivating the power supply of the hoisting motor may be done as a matter of principle.

[0031] In an embodiment, the method includes monitoring a safety chain of the elevator, and, if the safety chain is interrupted, deactivating the power supply of the hoisting motor, wherein, if the holding torque is fully removed in step (c) without a movement of the car being detected, the safety chain is favorably deactivated.

[0032] A safety chain is part of the standard safety installation of elevators. It includes a plurality of electrical switches and / or contacts that are arranged to provide a closed electrical circuit if the safety chain is closed. The safety chain is generally hard-wired. A closed respectively uninterrupted safety chain is required for operating the elevator, in particular for moving the car. An interruption of the safety chain respectively its electrical circuit causes the car to be stopped immediately. In particular, contacts of the contactors that provide electrical power to the motor drive circuit, e.g., a frequency converter, will open. Also, the brake will be activated respectively change into the activated state.

[0033] For carrying out a maintenance trip in the maintenance mode of an elevator, two control elements, typically pushbuttons, namely an activation pushbutton and either of the two direction pushbuttons need to be continuously operated, and releasing either of them results in an interruption of the safety chain, since all these control elements normally have contacts in the safety chain. For a design in accordance with the present disclosure, the safety chain generally needs to remain closed (i.e., the pushbuttons need to be continuously operated) while the maintenance trip termination routine is executed. Automatically deactivating the safety chain if no movement of the car is detected in step (c) as described before is favorable but not absolutely required. The expression pushbutton in this document refers to a monostable and typically spring-biased switching device with one or mor contacts that automatically assumes a released state if it is not operated.

[0034] For executing the safety parking routine, the safety chain is favorably active and needs to remain closed. Along with deactivating the power supply of the hoisting machine at the end of the safety parking routine and blocking the elevator, the safety chain may be deactivated.

[0035] In an embodiment, the maintenance trip termination command is provided by a person via a maintenance control panel that is arranged on the cartop.

[0036] For providing the maintenance trip termination command, a dedicated maintenance trip termination control element e.g., in the form of a pushbutton, may be foreseen. Such maintenance trip termination control element may be operated by the person on the car top, e. g. in addition to the activation button and either of the direction buttons as explained before. In other embodiments as explained in the following, however, the maintenance trip termination command is provided via an activation control element or direction control element as explained in the following. Providing the maintenance trip termination command may include switching a control element from a first actuated state into a second actuated state.

[0037] In an embodiment, the maintenance trip control panel includes two direction control elements, in particular direction pushbuttons, and an activation control element, in particular activation pushbutton. The activation control element and the direction control elements have in each case a released state and a first actuated, state. Execution of a maintenance trip requires a continuous operation of the activation control element and either of the direction control elements to be in their respective first actuated state. The activation control element may be a three-position control element having a second actuated state, and providing the maintenance trip termination command may include switching the actuation control element from its first actuated state into its second actuated state. Alternatively, the direction control elements are three-position control elements having a respective second actuated state, and providing the maintenance trip termination command includes switching the direction control element that is in the first actuated state into its second actuated state.

[0038] The element of a controlled that is operated by a user is referred to as actuation member. For a three-position pushbutton, the actuation member is operated by pressing it against the force of a spring for switching it from the released state into the first actuated state, and is switched into the second actuated state by further pressing it in the same direction. Alternatively, some or all of the control elements as mentioned before may, e.g., be realized as rotatory control elements with a rotatory knob as actuation member and may be spring -biased towards the released state. Favorably, the first actuated state corresponds in any case to an intermediate position of the actuation member, between the released state and the second actuated state.

[0039] A corresponding design of a three-position pushbutton that may in particular serve as direction pushbutton is disclosed in EP3613691B1, with the second actuation signal of EP3613691B1 corresponding to the maintenance trip termination command in accordance with the present disclosure. Other designs, however, may be used as well.

[0040] In an embodiment, executing the method for terminating a maintenance requires a person to constantly operate two separate control elements, wherein a safety chain of the elevator is interrupted if either of the control elements is released. These control elements may, e.g., be the activation control element and either of the direction control elements as mentioned. Interruption of the safety chain causes an immediate stop of the car and in particular causes the power supply of the hoisting motor to be deactivated, and the brake of the elevator drive to be activated. Also, executing the maintenance trip prior to providing the maintenance trip termination command requires the two separate control elements to be constantly operated as mentioned before.

[0041] In an embodiment, the hoisting motor is powered via a motor drive circuit of the elevator. The motor drive circuit may include an inverter and / or frequency converter. This is a typical design if the hoisting motor is, e.g., an AC synchronous motor. Other types of hoisting motors may require a correspondingly adapted hoisting motor drive circuit as generally known in the art. The motor drive circuit may be designed to receive power for its own operation and / or for powering the hoisting motor from a typically commercial, typically three-phase, external AC mains supply, and / or from an emergency power supply of the elevator. The motor drive circuit is favorably designed to stay operable, e.g., in a standby mode, in a deactivated state of the power supply of the hoisting motor.

[0042] In an embodiment, the drive is a gearless drive with a drive sheave for the traction member being directly arranged on the motor shaft. Other designs may be used as well. The drive may be arranged at any suited location in accordance with the overall design of the elevator. In some embodiments, the drive is arranged in a headroom of the hoistway or in a machine room above the hoistway. It is noted that the elevator is generally designed according to the state of the art and includes the typically present components and units, such safety equipment as generally known in the art and / or as required by applicable regulations, as well as a car door, hoistway doors, a COP and LOPs and the like.

[0043] In an embodiment, the maintenance trip termination command is received by a control unit and execution of the maintenance trip termination routine is controlled by the control unit. This type of embodiments allows an automated termination of a maintenance trip in accordance with the present disclosure. The control unit may also be designed to control operation of the elevator in regular operation and may accordingly be an elevator control unit.

[0044] The control unit may include components and functional units as generally known in the art, including analogue and / or digital circuitry as well as one or more computers, respectively microcontrollers and / or microprocessors with corresponding code. The control unit may be realized as single, compact unit or may be distributed. It may be installed in the hoistway, a dedicated machine room, or a combination thereof. A motor drive circuit may be a separate unit under control of the control unit or may be partly or fully integrated with the control unit.

[0045] The figures show:

[0046] Fig. 1 a schematic view of an exemplary elevator in accordance with the present disclosure;

[0047] Fig. 2 a schematic control structure of an exemplary elevator in accordance with the present disclosure;

[0048] Fig. 3 an operational flow of an exemplary method for controlling an elevator for a maintenance trip in accordance with the present disclosure.

[0049] It is noticed that structural figures are schematic and not to scale where not explicitly mentioned. Further, the relative position, arrangement and size of individual elements does not necessarily correspond to a practical arrangement. Identical reference signs are used for identical or like elements over the different figures where possible. In the following, exemplary embodiments in accordance are further illustrated with additional reference to the figures.

[0050] Figure 1 shows an embodiment of an elevator 1 in a side view. The elevator 1 includes a car 11 and a counterweight 12 that are coupled via a flexible traction member 14, such as one or multiple ropes or belts. The car 11 and the counterweight 12 are arranged vertically movable in a hoistway (not shown as such) in a guided manner. On the top of the car 11, a maintenance control panel 11.1 is arranged. It is noted that the elevator 1 further includes a COP in the car and a LOP at each landing respectively floor, which, however, are not shown.

[0051] The elevator 1 further includes a drive 13 with a hoisting motor 13.1, a brake 13.2 and a drive sheave 13.3 as generally known in the art. In the shown design, the drive 13 is a gearless drive with the drive sheave 13.3 being directly fixed on the motor shaft 13.4. Also, the brake 13.2 acts on the motor shaft 13.4. The motor shaft 13.4 is part of or coupled to the rotor of hoisting motor 13. 1. As mentioned before, the brake 13.2 may include two or more distinct brake assemblies (not separately shown) to provide redundancy, with each brake assembly having an active state and deactivated state.

[0052] The elevator 1 is in the shown design machine room -less, with the drive 13 being directly arranged in the headroom of the hoistway. As described in the general description, the brake is spring-biased towards an activated state where it provides a braking force. The brake 13.2 is exemplarily assumed to be an electromagnetic brake that is held in a non-activated state for a movement of the car 11 against the biasing force by an electromagnet (not separately shown). If the electromagnet is de-energized, the springs force the brake into the activated respectively engaging state. The brake 13.2 is typically realized in a redundant manner.

[0053] The traction member 14 is coupled to the drive 13 via the drive sheave 13.3 as generally known to allow movement of the car 11 and the counterweight 12 in opposite vertical directions by rotating the drive sheave 13.3.

[0054] Further, a bumper 15 for the counterweight 12 is shown which is mounted on the ground of the hoistway. In a lowermost position of the counterweight 12, corresponding to an uppermost posi- tion of the car 11, the counterweight 12 rests on the bumper 15 which is compressed accordingly. It is noted that further elements, such as a safety gear, an overspeed governor, a bumper for the car 11 and the like are generally also present as known in the art but are not shown in the interest of clarity.

[0055] In the following, reference is additionally made to Figure 2, showing an embodiment of the control structure of an elevator 1 in accordance with the present disclosure in a highly schematic functional view. In Figure 2, the major relevant flow of information respectively signals as well as power is indicated by dashed arrows. In the interest of clarity, only such elements respectively units are shown that are of relevance in the context of the present disclosure. It is noted that distinction between the single functional units does not imply any particular structural realization.

[0056] The elevator 1 includes a control unit 100 that generally controls operation of the elevator 1 and may be realized by general circuitry as well as microcontrollers and / or microcontrollers with corresponding code.

[0057] The power for the drive 13, in particular the hoisting motor 13.1, is during regular operation received from mains supply 130, generally a typically commercial three-phase AC mains supply. The hoisting motor 13.1 is powered under control of the control unit 100 via a motor drive circuit 110 that includes in the shown design an inverter as known in the art. As the hoisting motor 13.1 operates, the encoder 13.11 that is coupled to the rotor provides a corresponding feedback signal to the controller 100.

[0058] Between the mains supply 130 and the motor drive circuit 110, a contactor unit 120 with, e.g., two three-phase contactors in serial arrangement is arranged. Via the contactor unit 120, the power supply to the hoisting motor 13.1 may be interrupted and accordingly deactivated.

[0059] Further, the brake 13.2 is controlled by the control unit 100 to alternatively assume an activated respectively engaging state if it is not powered or a non-activated respectively disengaged state if it is powered. A brake sensor 13.21 is foreseen to provide a corresponding feedback sensor in dependence of the state of the brake 13.2.

[0060] The maintenance operation panel 11. 1 is arranged on the car top and is connected to the control unit 100. The maintenance control panel 11.1 in particular includes an activation pushbutton 11.11 as activation control element and two direction pushbuttons 111.12, 11.13 as direction control elements for the upwards and downwards direction, respectively. While the activation pushbutton 11.11 is a two-position pushbutton, having a released state and a first actuated state, the direction pushbuttons 11.12, 11. 13 are three-position pushbuttons as explained before in the general description and may further be in a second actuated state. Thereby, the direction control pushbuttons 11.12, 11.13 may also serve for providing a maintenance trip termination command. It is noted that a two-position pushbutton does not have a second activated state, in contrast to a three-position pushbutton.

[0061] Further, the maintenance control panel 11.1 has an indicator light 11. 14 as alerting device, such as a warning lamp, that is activated by the control unit 100 if a safety parking routine is executed. It is noted that the maintenance control panel 11.1 may include further control elements, such as an emergency power off button, an alarm pushbutton and / or a maintenance control panel activation switch that need to be operated prior to controlling the elevator 1 via the maintenance control panel. The maintenance control panel activation switch is generally biostable, i.e. is only operated for switching between its states.

[0062] As special part of the control unit 100, a safety chain 99 is foreseen. The safety chain 99 is generally designed as known in the art. Regarding the pushbuttons 11.11, 1.12, 13, it is noted that all of them have contacts in the safety chain if the elevator 1 is operated in the maintenance mode. For the safety chain 99 to be closed respectively uninterrupted, both the activation pushbutton 11.11 and either of the direction pushbuttons 11.12, 11.13 need to be simultaneously and continuously operated. For the direction pushbuttons 11.12, 11.13, their respective contact in the safety chain 99 is closed if they are in the first actuated state or their second actuated state, but not in the released state. Similarly, the contact of activation pushbutton 11.11 in the safety chain is closed if the activation pushbutton 11.11 is in its actuated state, but not in its released state. An interruption of the safety chain 99 results in the contactor unit 120 deactivating the power supply to the motor drive circuit 110 and accordingly the hoisting motor 13.1, as well as an activation of the brake 13.2 by interrupting the power supply of its electromagnet.

[0063] In the following, reference is additionally made to Figure 3, illustrating an exemplary operational flow for a maintenance trip in accordance with the present disclosure. At a start S, it is assumed that the elevator 1 is in a maintenance mode where its operation is controlled by a person on the car top via the maintenance control panel 11.1. Further it is assumed that the elevator is at standstill. Further, it is assumed that the safety chain 99 is continuously monitored and the elevator stops immediately if the safety chain is interrupted as mentioned before.

[0064] At step SOI, the person initiates a maintenance trip by operating the activation pushbutton 11.11 to assume its first actuated state and further operating either of the direction pushbuttons 11.12 or 11.13 to assume its first actuated state. In response, the control unit 100 controls the elevator drive 13 respectively the hoisting motor 13.1 to move the car 11 with a generally constant velocity, in dependence of the operated direction pushbutton 11.12 or 11.13, with the brake being deactivated.

[0065] For terminating the maintenance trip, the person provides a maintenance trip termination command in step S02 to the control unit 100 by operating the respective direction pushbutton 11.12, or 11.13 to assume its second actuated state, while continuously maintaining the activation pushbutton 11.1 in its first actuated state. It is noted that in preceding step SOI the state of the direction pushbuttons 11.11, 1.12 is continuously monitored by the control unit 100 (not explicitly shown).

[0066] Providing the maintenance trip termination command in step S02 causes the control unit 100 in step S03 to control the hoisting motor 13.1 to decelerate the car 11 in a continuous manner to standstill, followed by controlling the brake 13.2 to assume its activated state by switching off its electromagnet. As the brake sensor 13.21 indicates that the brake 13.2 is in the activated state and accordingly should provide the required braking force to maintain the car 11 stationary respectively at standstill, the operational flow proceeds with step S04. It is noted that during activation of the brake 13.2, the hoisting motor 13.1 provides a holding torque.

[0067] In step S04, the controller 100 controls the hoisting motor 13.1 to reduce the holding torque. In subsequent step S05, it is tested by evaluating the encoder signal of encoder 13.11 whether the rotor of the hoisting motor 13.1 and accordingly the car 11 have moved. In the negative case, the operational flow proceeds with step S06. In step S06, it is tested whether the holding torque is zero. In the negative case, the operational flow returns to step S04 to further reduce the holding torque. If it is determined on step S06 that the holding torque is zero, the operational flow proceeds with step S07. In step S07, the contactors of the contactor unit 120 are released, resulting in the power supply of the motor control circuit 110 and accordingly the hoisting motor 13.1 being interrupted. Further in step S07, the safety chain 99 is deactivated, and the operational flow ends in El . Successfully termination of the maintenance trip may be indicated to the person as mentioned before. This corresponds to the termination of the maintenance trip if the brake 13.2 provides the required braking force as intended. As long as the elevator is in the maintenance mode, a further maintenance trip may be started by again operating the activation pushbutton 11.11 and either of the direction pushbuttons 11.12, 1.33.

[0068] If, however, it is found in step S05 the holding torque that the car is moving, i.e., the signal of encoder 13.11 indicates a rotor movement, the operational flow proceeds with step S08 where a safety parking routine is executed. This is a situation where the brake 13.2 provides no or no sufficient braking force and, without countermeasures, an uncontrolled movement of car 11 as explained before would occur.

[0069] In the emergency parking routine, the hoisting motor 13.1 is first controlled in step S08a to provide a braking torque, thereby stopping the movement of the car 11 and bringing it to standstill. In subsequent step S08b, the brake 13.2 is controlled to assume the non-activated state and the hoisting motor 13.1 is controlled to move the car 11 into the safety parking position as explained, generally an uppermost position in the hoistway. In the safety parking position, the counterweight 12 is in its lowermost position and rests on its bumper 15. Finally in step S08c, the contactor unit 120 is controlled to deactivate the power supply of the hoisting motor 13.1 and the elevator is blocked to prevent further activation. Along with the before-mentioned steps of the safety parking routine, the alerting device respectively indicator light 11.14 is activated to alert the person on the car top. Completion of the safety parking routine may be indicated to the person, e.g., by switching off the indicator light 11. 14. In case of a safety parking routine being executed, the operational flow ends in E2. Now, the person on the car top may act, in particular call for help, to be rescued respectively released.

[0070] It is noted that for the here-described operational flow, the person needs to continuously operate the activation pushbutton 11. 11 and either of the direction pushbuttons 11.12, 11.13 to ensure that the safety chain 99 stays closed respectively uninterrupted. Optionally, however, steep S08 may include removing the pushbuttons 11.11, 11.12, 11.13 from the safety chain 99, e.g., by bridging their respective contacts of the safety chain 99. In this case, the safety parking routine can be executed even if either or both the activation pushbutton 11.11 and the previously operated direction pushbutton 11.12 or 11.13 are released by the person.

[0071] REFERENCE SIGNS

[0072] I elevator

[0073] I I car

[0074] 11.1 maintenance control panel

[0075] 11.11 activation control element (activation pushbutton)

[0076] 11.12, 11.3 direction control element (direction pushbutton)

[0077] 11.14 alerting device (indicator lamp)

[0078] 12 counterweight

[0079] 13 drive

[0080] 13.1 hoisting motor

[0081] 13.2 brake

[0082] 13.21 brake sensor

[0083] 13.3 drive sheave

[0084] 13.4 motor shaft

[0085] 13.11 encoder

[0086] 14 traction member

[0087] 15 bumper for counterweight

[0088] 99 safety chain

[0089] 100 control unit

[0090] 110 motor drive circuit

[0091] 120 contactor unit

[0092] 130 mains supply

Claims

CLAIMS1. A method for terminating a maintenance trip of an elevator (1), the method including providing a maintenance trip termination command and, in response to the maintenance termination command, executing a maintenance trip termination routine, the maintenance trip termination routine including: a) controlling a hoisting motor (13.1) of a drive (13) to decelerate a car (11) in a controlled manner, b) upon standstill of the car (11), controlling a brake (13.2) of the drive (13) to change from a non-activated state into an activated state while controlling the hoisting motor (13.1) to provide a holding torque, c) controlling the hoisting motor ( 13.1 ) to reduce the holding torque, in particular in a continuous manner, while monitoring whether the car (11) is moving, and, only if a movement of the car (11) is detected in step (c), d) executing a safety parking routine, the safety parking routine including moving the car (11) into a safety parking position, deactivating the power supply of the hoisting motor (13.1) and blocking the elevator (1).

2. The method according to claim 1, wherein the safety parking routine includes providing an acoustical and / or optical alert.

3. The method according to anyone of the preceding claims, wherein step (b) includes monitoring a state of the brake (13.2) via a brake sensor (13.21), and wherein step (c) is only executed upon the brake sensor (13.21) indicating that the brake (13.2) is in the activated state.

4. The method according to anyone of the preceding claims, wherein monitoring whether the car (11) is moving includes evaluating an encoder signal of an encoder (13.11) coupled to a rotor of the hoisting motor (13.1).

5. The method according to anyone of the preceding claims, wherein the safety parking routine includes, prior to moving the car (11) into the safety parking position, controlling the hoisting motor ( 13.1 ) to stop the movement of the car ( 11 ) by providing a braking torque .

6. The method according to anyone of the preceding claims, wherein in the safety parking position the car (11) is in an uppermost position within a hoistway and a counterweight (12) of the elevator is in a lowermost position and rests on a bumper (15).

7. The method according to anyone of the preceding claims, wherein the method includes, if the holding torque is fully removed in step (c) without a movement of the car (11) being detected, deactivating the power supply of the hoisting motor (13.1).

8. The method according to anyone of the preceding claims, wherein the safety parking routine includes, prior to moving the car (11) into the safety parking position, controlling the brake to change into the non-activated state.

9. The method according to anyone of the preceding claims, the method further including monitoring a safety chain (99) of the elevator (1), and, if the safety chain (99) is interrupted, deactivating the power supply of the hoisting motor (13.1), wherein, if the holding torque is fully removed in step (c) without a movement of the car being detected, the safety chain (99) is favorably deactivated.

10. The method according to anyone of the preceding claims, wherein the maintenance trip termination command is provided by a person via a maintenance control panel (11.1) that is arranged on a car top.

11. The method according to claim 10, wherein the maintenance control panel (1.11) includes two direction control elements, in particular direction pushbuttons (11.12, 11.13) and an activation control element, in particular activation pushbutton (11.1), wherein the activation control element and the direction control elements have in each case a released state and a first actuated, state, wherein execution of a maintenance trip requires a continuous operation of the activation control element and either of the direction control elements to be in their respective first actuated state, wherein the activation control element is a three-position control element having a second actuated state, and providing the maintenance trip termination command includes switching the actuation control element from its first actuated state into its second actuated state, or, alternatively,the direction control elements are three-position control elements having a respective second actuated state, and providing the maintenance trip termination command includes switching the direction control element that is in the first actuated state into its second actuated state.

12. The method according to anyone of the preceding claims, wherein the hoisting motor (13.2) is powered via a motor drive circuit (110) of the elevator (1), wherein the motor drive circuit (110) in particular includes an inverter and / or frequency converter.

13. The method according to anyone of the preceding claims, wherein the maintenance trip termination command is received by a control unit (100) and wherein execution of the maintenance trip termination routine is controlled by the control unit (100).

14. Control unit (100), the control unit (100) being configured to receive a maintenance trip termination command and, in response to receiving the maintenance trip termination command, to control execution of a maintenance trip termination routine in accordance with anyone of the preceding claims.

15. Elevator (1), the elevator (1) including a hoistway, a car (11), a counterweight (12), a drive (13) and a control unit (100) according to claim 14. wherein the car (11) and the counterweight (12) are arranged vertically movable in the hoistway, wherein the car (11) and the counterweight (12) are coupled via a flexible traction member (14) and are suspended by the traction member, wherein the drive (13) is coupled to the traction member (14) for moving the traction member (14) and thereby the car (11) and the counterweight (12).

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