WO2019175398A1

WO2019175398A1 - Elevator arrangement enabling methods for determining and monitoring a minimum counterweight to buffer distance

Info

Publication number: WO2019175398A1
Application number: PCT/EP2019/056563
Authority: WO
Inventors: Archana PILLAI; Om Prakash
Original assignee: Inventio Ag
Priority date: 2018-03-16
Filing date: 2019-03-15
Publication date: 2019-09-19

Abstract

An elevator arrangement (1) is proposed as comprising an elevator cabin (3), a counterweight (5), a drive engine (9), an elevator controller (13), some elongate suspension traction media(15) and a buffer (17) arranged at a lower end of the travel path of the counterweight (5) such as to support the counterweight (5) with a stopper lever (19) upon the counterweight (5) being displaced downwards beyond a predetermined lower limit position (31). The elevator arrangement (1) further comprises a lower limit sensor arrangement (27) being positioned and configured such as to be actuated upon the counterweight (5) being displaced downwards beyond the predetermined lower limit position (31). The lower limit sensor arrangement (27) may be implemented with a light barrier arrangement. Additionally, the elevator arrangement (1) may comprise a pre-limit sensor arrangement (29) being positioned and configured such as to be actuated upon the counterweight (5) being displaced downwards beyond a predetermined pre-limit position (33), the predetermined pre-limit position (33) being upward of the predetermined lower limit position (31). Using these sensor arrangements (27, 29), a minimum counterweight- buffer-distance (37) may be automatically monitored and, if required, may be measured in a beneficial manner.

Description

Elevator arrangement enabling methods for determining and monitoring a minimum counterweight to buffer distance

The present invention relates to a method for determining a minimum distance between a counterweight and a buffer in an elevator arrangement, a method for monitoring such minimum counterweight-buffer-distance and an elevator arrangement being specifically configured for enabling such methods.

An elevator arrangement generally comprises an elevator cabin to be displaced between various floors in a building. Together with a counterweight, the elevator cabin is suspended by elongate suspension traction media comprising for example a plurality of ropes or belts. By displacing the suspension traction media using a drive engine, the elevator cabin and the counterweight are each driven along travel paths in opposite directions within an elevator shaft.

Generally, at a bottom of the elevator shaft, i.e. at a pit, a buffer is provided at a location underneath the travel path of the counterweight. Such buffer serves for supporting the counterweight in case the counterweight is moved beyond a predetermined lower limit position, for example as a result of a damage in the elevator arrangement or in case of an emergency. By supporting the counterweight in such situation, an integrity of the counterweight as well as of the elevator shaft may be protected. For such purpose, the buffer typically comprises a movable stopper lever. A motion of the stopper lever may be decelerated and/or damped. The stopper lever extends underneath the travel path of the counterweight and its upper end substantially coincides with the predetermined lower limit position at which the counterweight shall be supported by the buffer.

In normal operation, the components of the elevator arrangement shall be configured such that the counterweight is never displaced beyond the predetermined lower limit position. For such purpose, for example a length of the elongate traction suspension media and the dimensions of the cabin and the counterweight are selected such that even in a situation where the cabin is driven to the uppermost floor to be served by the elevator arrangement and, accordingly, the counterweight is displaced to the lowermost position along its travel path, the counterweight is not displaced to a level at or underneath the predetermined lower limit position. Accordingly, under intended normal operation conditions, the counterweight should never be supported by the stopper lever of the buffer.

However, upon continued operation of the elevator arrangement, for example the traction suspension media tend to stretch. Due to such or similar modifications, the position to which the counterweight is displaced upon the elevator cabin being driven to the uppermost floor position may change over time and may gradually come closer to the predetermined lower limit position. Generally, it should be avoided that the buffer supports the counterweight during normal operation of the elevator arrangement. A reason is for example that upon the

counterweight being supported by the buffer and therefore further motion of the counterweight being stopped, the drive engine may continue to attempt displacing the suspension traction media such that, on the one side, the elevator cabin is further lifted while, on the other side, the counterweight may no more move in a downward direction

(downwards in the shaft) such that the suspension traction media may become slack in a portion between the counterweight and the drive engine. However, any slack in the suspension traction media should be avoided as, for example, a traction between the drive engine and the suspension traction media could suddenly fail such that, on the one side, the previously slack portion of the suspension traction media is suddenly tightened again while, on the other side, the elevator cabin suddenly sinks almost in a freefall, thereby risking comfort or even safety of passengers in the cabin. ln order to avoid situations in which the buffer supports the counterweight during normal operation of the elevator arrangement, a minimum counterweight-buffer-distance should be monitored. Such minimum counterweight-buffer-distance shall be defined as the distance between a lowermost portion of the counterweight and an uppermost portion of the buffer, i.e. generally a position of the stopper level of the buffer. Therein, the minimum counterweight-buffer-distance is to be determined in a situation where the counterweight is driven to a lowermost position accessible during normal operation of the elevator arrangement, i.e. without ignoring for example any end-of-path- limits hindering driving the elevator cabin beyond an uppermost floor level during normal operation. The minimum counterweight-buffer-distance is sometimes also referred to as“run-by”. Generally, characteristics of the elevator arrangement and particularly of its suspension traction media are configured such that such minimum counterweight-buffer- distance exceeds a minimum limit of for example 150 mm but at least, under all circumstances during normal elevator operation, should never shrink to zero.

Conventionally, the minimum counterweight-buffer-distance is monitored by technicians inspecting the elevator arrangement on a regular basis.

For example, a monitoring procedure may be executed as follows: Two technicians inspect the elevator arrangement. A first technician goes to a top landing, puts the elevator arrangement into an“inspection mode” and makes a cabin top entry using a cabin top entry procedure. A second technician opens a landing door at a bottom floor of the elevator shaft and enters the pit of the elevator shaft using a pit entry procedure. The first technician then takes the elevator cabin up to align with the top landing, thereby causing the counterweight to come to its lowermost accessible position, i.e. to come close to the buffer. The second technician inside the pit may then for example remove a counterweight screen guard. The second technician then may physically measure the minimum counterweight-buffer-distance between the counterweight and the buffer using for example a conventional scale. Based on the measured distance, the second technician may make necessary adjustments on the counterweight and/or on the suspension traction media. After such adjustments, the second technician may again measure the distance between the counterweight and the buffer to ensure that the minimum counterweight- buffer-distance is set correctly. Finally, the processes performed at the beginning of the inspection procedure may be reversed for putting the elevator arrangement back into its normal operation conditions.

However, such conventional monitoring procedure may have various drawbacks. For example, repeatedly inspecting the elevator arrangement by two technicians requires substantial human labour and therefore costs. Furthermore, having one technician working in the pit of the elevator shaft always bears a risk of this technician being injured by elevator components, particularly by the counterweight being above the technician. This is particularly true in cases where the elevator component’s motion is not controlled by the second technician in the pit but for example by the first technician being located remote to the second technician. Alternative approaches for measuring the minimum counterweight-buffer- distance have been developed but generally are either technically complex or not sufficiently reliable. Accordingly, there may be a need for an improved method for determining a minimum counterweight-buffer- distance and for an improved method for monitoring the minimum counterweight-buffer- distance. Particularly, there may be a need for such methods which require reduced human labour, reduced efforts and/or reduced costs and/or which allow avoiding hazardous situations for technicians and/or which may improve a reliability in operating an elevator arrangement. Furthermore, there may be a need for an elevator arrangement enabling performing such methods.

Such needs may be met with the subject-matter of the independent claims. Advantageous embodiments are defined in the dependent claims and in the following specification.

According to a first aspect of the present invention, an elevator arrangement is proposed, the elevator arrangement comprising an elevator cabin, a counterweight, a drive engine, an elevator controller and elongate suspension traction media extending between the elevator cabin and the counterweight such as to displace the elevator cabin and the counterweight along opposite travel paths upon the suspension traction media being displaced by the drive engine under control of the elevator controller. The elevator arrangement furthermore comprises a buffer with a stopper lever arranged at a lower end of the travel path of the counterweight such as to support the counterweight with the stopper lever upon the counterweight being displaced downwards beyond a

predetermined lower limit position. Finally, the elevator arrangement comprises a lower limit sensor arrangement being positioned and configured such as to be actuated upon the counterweight being displaced downwards beyond the predetermined lower limit position. According to a second aspect of the present invention, a method for determining a minimum counterweight-buffer-distance in an elevator arrangement according to an embodiment of the first aspect of the invention is proposed. Therein, the minimum counterweight-buffer- distance is defined as extending between a lowermost end of the counterweight and the stopper lever of the buffer. The method comprises at least the following steps, preferably, but not necessarily, in the indicated order: (i) the elevator cabin is driven to an uppermost floor; (ii) the elevator cabin is then further driven in an upward direction (upwards in the shaft) until, at an upper limit cabin position, an alarming signal is issued by the lower limit sensor arrangement upon being actuated due to the counterweight being displaced downwards beyond the predetermined lower limit position; (iii) a travelling distance travelled by the elevator cabin upon being displaced between the uppermost floor and the upper limit cabin position is measured; and (iv) the minimum counterweight-buffer-distance is determined as being equal to the measured travelling distance.

According to a third aspect of the invention, a method for monitoring a minimum counterweight-buffer- distance is proposed for an elevator arrangement according to a specific embodiment of the first aspect of the invention in which the elevator arrangement comprises a pre-limit sensor arrangement arranged at a pre-limit position. Therein a warning signal for requesting inspection is issued and transmitted to a remote control centre upon the pre-limit sensor arrangement being actuated.

Ideas underlying embodiments of the present invention may be interpreted as being based, inter alia and without restricting a scope of the invention, on the following observations and recognitions.

As explained above, conventional approaches for monitoring the counterweight-buffer- distance in an elevator arrangement required periodical inspection of the elevator arrangement and particularly required labour-intensive and/or safety-critical procedures to be performed for determining a current counterweight-buffer- distance.

The approach described herein allows avoiding at least substantial portions of the efforts required for such inspections and/or counterweight-buffer-distance determination by employing suitable technical means in the elevator arrangement to be monitored.

Specifically, it is proposed to include a lower limit sensor arrangement into the elevator arrangement. Such lower limit sensor arrangement shall be positioned and configured such that it is actuated as soon as the counterweight is displaced in a downward direction down to a level at which the counterweight is supported by the buffer, i.e. as soon as the counterweight travels further downward beyond the predetermined lower limit position. In other words, the lower limit sensor arrangement may automatically detect when the lower end of the counterweight reaches the stopper lever of the buffer such as to be substantially supported by the buffer.

Such automatic detection of an engagement between the counterweight and the buffer may be beneficially used in methods according to embodiments of the invention relating to both, determining the minimum counterweight-buffer-distance in accordance with the second aspect of the invention as well as monitoring such counterweight-buffer- distance in accordance with the third aspect of the invention.

For example, in an embodiment of the method according to the second aspect of the invention, an actuation information provided by the lower limit sensor arrangement may be beneficially used in a procedure for determining the minimum counterweight-buffer- distance.

In an example of the proposed method, the elevator cabin may first be driven to an uppermost floor, i.e. the highest floor in a building served by the elevator arrangement. Upon reaching such uppermost floor, for example operation limits normally limiting the operation of the elevator arrangement in order to thereby prevent further upward displacement of the elevator cabin beyond such uppermost floor may be temporarily deactivated. Subsequently, the elevator cabin is further driven in an upward direction such as to reach levels higher than the uppermost floor. Upon such upward driving of the elevator cabin, the counterweight is displaced in the opposite direction and continuously comes closer down to the buffer limiting its travel path. The upward driving of the elevator cabin is continued until the counterweight reaches the stopper lever of the buffer, i.e. until the counterweight is lowered beyond the predetermined lower limit position. At that stage of the procedure, the lower limit sensor arrangement is automatically actuated and issues a signal referred to herein later as an“alarming signal”. Such alarming signal may be recognised by the inspecting technician and may be understood as indicating that the counterweight has reached the level of the buffer. Accordingly, at that stage of the procedure, the travelling distance which has been travelled in the upward direction by the elevator cabin since the elevator cabin has left the level of the uppermost floor may be measured. This travelling distance corresponds to the distance the counterweight has travelled in the downward direction between a lowermost level where the counterweight is stopped during normal operation, i.e. when the cabin reaches the uppermost floor, and the predetermined lower limit position where the counterweight begins to be supported by the buffer. Accordingly, this travelling distance corresponds to the minimum

counterweight-buffer- distance to be determined.

Such entire method may be performed and controlled by a single technician. No second technician is required. The process of displacing the elevator cabin and the counterweight may be under full control of the single technician. Particularly, the technician may perform the entire method while being in the cabin or being at the landing of the uppermost floor. No technician needs to enter the pit of the elevator shaft.

Accordingly, the presence of the lower limit sensor arrangement in the elevator arrangement proposed herein enables that the minimum counterweight-buffer- distance may be determined easily by a single technician and with minimum risk for the technician. Furthermore, as the lower limit sensor arrangement may be technically simple and/or cost-effective, the described benefits for the method for determining the minimum counterweight-buffer-distance may be implemented reliably and/or at minimal costs. Particularly, minimal changes in software and/or hardware of the elevator arrangement may be required.

According to an embodiment of the second aspect of the invention, the travelling distance corresponding to the minimum counterweight-buffer-distance may be measured manually by a technician.

In other words, the proposed method for determining the minimum counterweight-buffer- distance may be executed by a technician, preferably a single technician. Therein, the technician may for example control motions of the elevator cabin and of the

counterweight by suitably instructing the elevator controller. Furthermore, the technician may manually measure the distance travelled by the elevator cabin after the elevator cabin’s position has exceeded the uppermost floor level and upon the technician being informed that the counterweight has reached the level of the buffer, such information being obtained upon receiving the alarming signal issued by the lower limit sensor arrangement. For example, the technician may manually measure the travelling distance using a conventional scale or similar tools. Accordingly, due to being precisely informed about the travelling distance, this distance being both, identical to the counterweight- buffer-distance and being easy to be measured by a technician, the entire method of determining the minimum counterweight-buffer- distance may be performed by a single technician not necessarily requiring substantial technical skills.

According to a specific embodiment of the elevator arrangement, the elevator arrangement further comprises a so-called pre-limit sensor arrangement. This pre-limit sensor arrangement is positioned and configured such as to be actuated upon the counterweight being displaced downwards beyond a predetermined pre-limit position.

Therein, the predetermined pre-limit position is upwards of the predetermined lower limit position.

In other words, in addition to the lower limit sensor arrangement, the elevator arrangement may comprise the pre- limit sensor arrangement at a level higher than the predetermined lower limit position at which the lower limit sensor arrangement is positioned. Accordingly, the pre-limit sensor arrangement is actuated when the counterweight is displaced in a downward direction and reaches the predetermined pre limit position, i.e. substantially before reaching the predetermined lower limit position. Particularly, the predetermined pre-limit position may be situated at a level somewhere in between the level of the predetermined lower limit position and a level at which the lower end of the counterweight is intended to stop in a condition as originally installed, i.e. before any deterioration or wear was applied to elevator components and thereby extended for example the counterweight’s scope of motion.

For example, according to a specific embodiment, the predetermined pre-limit position may be positioned at least 5 cm, preferably at least 10 cm, more preferably about 14 ± 3 cm, upwards of the predetermined lower limit position. However, the

predetermined pre-limit position should be less than 1 m, preferably less than 50 cm, upwards of the predetermined lower limit position.

Such selection of the level of the predetermined pre-limit position relative to the level of the predetermined lower limit position is assumed to be beneficial. On the one hand, upon reaching the predetermined pre-limit position during normal operation, the components of the elevator arrangement have already undergone some substantial wear or deterioration such that inspection may be necessary. On the other hand, this wear or deterioration is not yet safety-critical and substantially more wear or deterioration has to occur before the counterweight reaches the buffer such that sufficient time remains for inspecting the elevator arrangement.

The provision of the additional pre- limit sensor arrangement enables benefits for the method for monitoring the minimum counterweight-buffer-distance in the elevator arrangement as proposed in accordance with embodiments of the third aspect of the invention.

Particularly, the pre-limit sensor arrangement may be configured for outputting a warning signal upon being actuated. Such warning signal may be a signal which may be output and transmitted to other devices or persons in order to thereby informing that the counterweight has reached the predetermined pre- limit position. Accordingly, such warning signal may be interpreted as indicating that at least a specific wear or deterioration already took place within the components of the elevator arrangement such that the counterweight, during normal operation, does no more stop at an lowermost position as intended upon constructing the elevator arrangement but does move further downwards until reaching the predetermined pre-limit position. While such wear or deterioration may not yet be critical for the safety of the operation of the elevator arrangement as the counterweight does not yet reach the predetermined lower limit position, i.e. is not yet supported by the buffer, such issuing of a warning signal may indicate that the elevator arrangement should be inspected.

For example, according to a specific embodiment, the pre-limit sensor arrangement may be configured for transmitting the warning signal to a remote control centre. ln other words, upon the pre-limit sensor arrangement being actuated, the issued warning signal may be transmitted to a remote control centre. The remote control centre may be located external to the elevator arrangement, for example far away from the elevator arrangement. Such remote control centre may monitor various characteristics of the elevator arrangement. Based on such monitored characteristics, for example inspection procedures may be planned. Particularly, upon receiving the warning signal from the pre- limit sensor arrangement, an inspection may be planned in which, inter-alia, the actual minimum counterweight-buffer- distance may be determined by a technician visiting the elevator arrangement and measuring this distance for example in accordance with an embodiment of the second aspect of the present invention. Accordingly, due to the information provided with the warning signal, inspections may be suitably triggered upon substantial wear or deterioration actually having occurred within the elevator system. On the other hand, unnecessary inspections and/or unnecessary efforts for determining the minimum counterweight-buffer- distance, as they where usual upon conventionally inspecting the elevator arrangement on a periodical basis, may be avoided.

This has the advantage, that as long as pre-limit sensor does not output a warning, no technician needs to visit the elevator arrangement.

According to an embodiment, the lower limit sensor arrangement may be configured for outputting an alarming signal upon being actuated.

In other words, while the pre-limit sensor arrangement may only issue a warning signal for warning that any potentially negative condition may occur in the elevator arrangement in the future and therefore inspection of the elevator arrangement in the near future is required, actuation of the lower limit sensor arrangement may result in an actual alarming signal being issued. Such alarming signal may indicate that a potentially negative condition has actually occurred within the elevator arrangement and that therefore immediate action may be required. For example, according to a specific embodiment, the lower limit sensor arrangement may be configured for transmitting the alarming signal to the elevator controller. In such case, the alarming signal transmitted to the elevator controller upon the lower limit sensor arrangement being actuated may be interpreted by the elevator controller as requesting a modification of an operation status of the elevator arrangement to allow a limited operation of elevator for passenger usage.

The modification of the operation status initiated upon receiving the alarming signal may be such that any potentially safety-critical situations and/or situations compromising for example the integrity of the elevator arrangement may be avoided. For example, as the issued alarming signal indicates that the counterweight has been lowered until reaching the buffer, i.e. until being supported by the stopper lever, and therefore potentially critical situations may occur upon further operating the elevator arrangement due to e.g. portions of the suspension traction media being slack, operation of the elevator arrangement may be immediately stopped upon the elevator controller receiving the alarming signal.

Alternatively, in reaction to receiving the alarming signal, the elevator controller may modify the operation status of the elevator arrangement such as to at least prevent the elevator arrangement from driving the elevator cabin to an uppermost floor. According to another embodiment of the elevator arrangement, the lower limit sensor arrangement and/or the pre-limit sensor arrangement each comprise a capacitive sensor. The capacitive sensor being adapted to change its capacity when the counterweight gets closer to it. The counterweight might contain a foil or any other plate-like structure to change the capacity of the capacitive sensor significantly when the counterweight passes the capacitive sensor.

A capacitive sensor is a contactless and cheap sensor arrangement and therefore advantageous for sensing a counterweight as discussed above and in the following. According to another embodiment of the elevator arrangement, the lower limit sensor arrangement and/or the pre-limit sensor arrangement each comprises a tactile sensor. The tactile sensor being activated by the counterweight when it comes close or passes by the tactile sensor. The counterweight might comprise an attached piece, e.g. an arm-like construction, which is oriented away from the counterweight towards the tactile sensor so that when the counterweight reaches a predefined position, the attached piece activates the tactile sensor.

A tactile sensor is reliable and cheap sensor arrangement and therefore advantageous for sensing a counterweight as discussed above and in the following. According to an embodiment of the elevator arrangement, the lower limit sensor arrangement and/or the pre-limit sensor arrangement each comprise a light source and a light detector such as to form a light barrier arrangement with a light barrier crossing the travel path of the counterweight at a height corresponding to the predetermined lower limit position and/or at a height corresponding to the predetermined pre-limit position, respectively.

According to a further embodiment of the elevator arrangement the lower limit sensor arrangement is one of the sensor types of the list comprising a light barrier arrangement, a capacitive arrangement or a tactile arrangement, whereas the pre- limit sensor arrangement is one of the sensor types of the list comprising a light barrier arrangement, a capacitive arrangement or a tactile arrangement. A combination of any of the above-mentioned sensor arrangement may increase the reliability of the system and is therefore advantageous for sensing a counterweight as discussed above and in the following. While a light barrier may not function reliably anymore because of dirty accumulated on either the light source or the light detector, a capacitive sensor is less sensitive to dirt. While a capacitive sensor may be sensitive to any object, which comes close to it, the tactile sensor is only triggered if the sensor is touched. A combination of any of these sensors therefore increases the reliability of the sensor arrangement and thus the security of the elevator arrangement. ln the embodiment of the light barrier, the lower limit sensor arrangement may be established with a light source and detector arrangement forming a light barrier which crosses the downward projection of the counterweight along its travel path at a height corresponding to the predetermined lower limit position. Alternatively or additionally, the pre-limit sensor arrangement may be established with another light source and detector arrangement forming another light barrier which crosses the downward projection of the counterweight along its travel path at a height corresponding to the predetermined pre limit position. lmplementing the lower limit sensor arrangement and/or the pre-limit sensor arrangement with light barrier sensor arrangements enables a technically simple and reliable realisation of the inventive elevator arrangement. The light barrier sensor arrangements may be cheap in both, their production as well as their installation in the elevator arrangement. Furthermore, as the light barrier sensor arrangements may be actuated without any mechanical interaction being required, a detection of a critical position of the counterweight may be established without risking that continued wear may deteriorate a detection capability.

For example, according to an embodiment, the light source may be fixed to a first guide rail and the light detector may be fixed to a second guide rail of the elevator arrangement.

The first and second guide rails may be arranged at opposite sides with respect to the travel path of the counterweight for guiding the counterweight upon being displaced along the travel path. In other words, components of the light barrier sensor arrangement may be installed to opposing guide rails guiding the counterweight’s motion. Accordingly, the light barrier established with such arrangement spans via the downward projection of the

counterweight along its travel path at a height corresponding to the predetermined pre limit position and/or at a height corresponding to the predetermined lower limit position. Accordingly, when reaching the predetermined pre- limit position or the predetermined lower limit position, the counterweight will automatically interrupt the local light barrier and thereby actuate the associated the pre- limit sensor arrangement or the associated lower limit sensor arrangement, respectively. Installing the components of the light barrier arrangements to the guide rails may be implemented in a technically simple manner and/or at low costs.

It shall be noted that possible features and advantages of embodiments of the invention are described herein partly with respect to an elevator arrangement, partly with respect to a method for determining a current minimum counterweight-buffer- distance and partly with respect to a method for monitoring such a current minimum counterweight-buffer- distance. One skilled in the art will recognize that the features may be suitably transferred from one embodiment to another and features may be modified, adapted, combined and/or replaced, etc. in order to come to further embodiments of the invention. In the following, advantageous embodiments of the invention will be described with reference to the enclosed drawings. However, neither the drawings nor the description shall be interpreted as limiting the invention. Fig. 1 shows a side view of an elevator arrangement according to an embodiment of the invention.

Fig. 2 shows a front view onto a buffer underneath a counterweight in an elevator arrangement according to an embodiment of the invention.

Fig. 3 shows a top view onto a buffer in between guide rails of an elevator arrangement according to an embodiment of the invention. The figures are only schematic and not to scale. Same reference signs refer to same or similar features.

Fig. 1 shows an embodiment of an elevator arrangement 1. The elevator arrangement 1 comprises an elevator cabin 3 and a counterweight 5 to be displaced in opposite directions within an elevator shaft 7. The elevator cabin 3 and the counterweight 5 are suspended by elongate suspension traction media (STM) 15 including a plurality of ropes or belts. Furthermore, the elevator arrangement 1 comprises a drive engine 9, an operation of which is controlled by an elevator controller 13. The drive engine 9 comprises a traction sheave 11 for displacing the STM 15 in order to thereby drive the elevator cabin 3 to one of a plurality of floors 59. Upon being displaced along the elevator shaft 7, the counterweight 5 is guided along its travel path using guide shoes 23 engaging with guide rails 25 arranged at opposite sides of the travel path.

Upon the elevator cabin 3 being driven between a lowermost floor 61 and an uppermost floor 63 served by the elevator arrangement 1 , the counterweight 5 is displaced in an opposite direction. Accordingly, when the elevator cabin 3 is situated at the uppermost floor 63, the counterweight 5 is situated at its lowermost allowable position close to a pit 8 of the elevator shaft 7 and approximately at a level of the lowermost floor 61, as shown in Fig. 1.

A buffer 17 is arranged in the pit 8 at a location underneath the travel path of the counterweight 5. The buffer 17 comprises a stopper lever 19 being movable in a vertical direction. At its upper end, the stopper lever 19 comprises a horizontal stopper plate 21. The stopper plate 21 may be supported by a spring 20. The buffer 17 may serve for dampening a motion of the counterweight 5 in case the counterweight 5 is displaced downwards beyond its lowermost allowable position, for example due to a malfunction or damage within the elevator arrangement 1. Generally, under normal operation conditions, the elevator cabin 3 may be driven to its uppermost allowable position at the uppermost floor 63, i.e. such that the bottom of the cabin 3 is substantially aligned with the bottom of the uppermost floor 63 but, due to limiting restrictions, may not be driven further upwards beyond such uppermost allowable position. Under intended operation conditions, for example a length of the suspension traction media 15 is dimensioned such that, when the cabin 3 is driven to its uppermost allowable position, the counterweight 5 is driven to its lowermost allowable position and, in this lowermost allowable position, a minimum counterweight-buffer- distance 37 remains between a lowermost end 35 of the counterweight 5 and an upper surface of the stopper plates 21 at the stopper lever 19 of the buffer 17. Such minimum counterweight-buffer- distance 37 is typically between 10 cm and 50 cm, depending for example on other characteristics of the elevator arrangement 1 such as a height of its elevator shaft 7. Due to such minimum counterweight-buffer-distance 37, the

counterweight 5 should never come into mechanical contact with the stopper lever 19, i.e. the counterweight 5 should not be supported by the buffer 17, during normal operation of the elevator arrangement 1.

However, for example due to wear or degradation of the suspension traction media 15 and accordingly lengthening of the STM 15, the lowermost allowable position of the counterweight 5 may successively move downwards during the life of the elevator arrangement 1. Accordingly, upon the counterweight 5 coming closer to the buffer 17, the minimum counterweight-buffer- distance 37 shrinks. If no countermeasures would be taken, the counterweight 5 would sooner or later come into mechanical contact to the buffer 17 when driven to its lowermost position and, upon the counterweight 5 being supported by the buffer 17, further displacing the STM 15 via the driving engine 9 could result in the STM 15 becoming locally slack.

As any slack in the STM 15 has to be avoided, the condition of the components of the elevator arrangement 1 and particularly of the STM 15 should be monitored such that an excessively reduced minimum counterweight-buffer-distance 37 is detected sufficiently before becoming critically small.

Conventionally, such monitoring was performed during periodical inspections in which the minimum counterweight-buffer- distance 37 was manually measured by two technicians, a first technician controlling the elevator controller 13 for controlling the displacement of the elevator cabin 3 towards the uppermost floor 63 and a second technician entering the pit 8 and locally measuring the minimum counterweight-buffer- distance 37.

In order to reduce the efforts necessary for inspecting the elevator arrangement 1 and, particularly, in order to avoid risks for any technicians, it is proposed to equip the elevator arrangement 1 with some technical provisions which enable simplified and more secure methods of monitoring the minimum counterweight-buffer-distance 37 and for determining the actual minimum counterweight-buffer-distance 37 in the elevator arrangement 1.

As shown in more details in Figs. 2 and 3, such provisions include at least a specific lower limit sensor arrangement 27 to be mounted within the elevator shaft 7. The lower limit sensor arrangement 27 is positioned and configured such that it is actuated upon the counterweight 5 being displaced downwards beyond a predetermined lower limit position 31 at which the buffer 17 begins to mechanically support the counterweight 5.

Furthermore, such provisions preferably additionally include a pre-limit sensor arrangement 29 which is positioned and configured such that it is actuated upon the counterweight 5 being displaced downwards beyond a predetermined pre-limit position 33. This pre- limit position 33 is located upwards of the predetermined lower limit position 31 by some distance 51 of between typically 10 cm and 20 cm, for example 14 cm.

On the other hand, at least in an initial configuration of the elevator arrangement 1, i.e. before any wear or deterioration has taken place and has lengthened for example the STM 15, the pre- limit position 33 is located substantially below the lowermost end 35 of the counterweight 5 upon the counterweight 5 being in its lowermost allowable position. A distance 53 between the pre-limit position 33 and such lowermost end 35 of the counterweight 5 lowered to its lowermost allowable position in the initial configuration of the elevator arrangement 1 may be more than 5 cm, preferably more than 10 cm. In a preferred embodiment, the lower limit sensor arrangement 27 and/or the pre-limit sensor arrangement 29 may be implemented using a lower limit light barrier arrangement 42 and a pre-limit light barrier arrangement 46, respectively.

The lower limit light barrier arrangement 42 comprises a light source 43 and a light detector 45. A light ray 44 emitted by the light source 43 spans a distance between the light source 43 and the light detector 45. Accordingly, the light ray 44 forms a light barrier such that the lower limit sensor arrangement 27 is actuated upon the light ray 44 being interrupted for example by the lowermost end 35 of the counterweight 5 entering the space between the light source 43 and the light detector 45.

Therein, the lower limit light barrier arrangement 42 is positioned such that the level of the light ray 44 substantially coincides with the upper end of the buffer 17, i.e., in the example shown, substantially coincides with the level of the upper surface of the horizontal stopper plate 21 of the stopper lever 19. Therein,“substantially coincide” may be interpreted such that the level of the light ray 44 deviates from the level of the upper end of the buffer 17 by less than an acceptable tolerance. Such acceptable tolerance may depend on characteristics of the elevator arrangement 1 and may typically be in a range of between a few millimetres to some centimetres, for example in between 2 mm and 2 cm. Similarly, the pre-limit light barrier arrangement 46 may comprise a light source 47 and a light detector 49. A light ray 48 emitted by the light source 47 crosses a space towards the light detector 49. Accordingly, a light barrier formed by the light ray 48 is interrupted as soon as the counterweight 5 comes closer to the buffer 17 when positioned at its lowermost allowable position due to for example wear-induced lengthening of the STM 15, such that its lowermost end 35 blocks the space between the light source 47 and the light detector 49 of the pre-limit light barrier arrangement 46.

The lower limit barrier arrangement 42 and/or the pre-limit barrier arrangement 46 or at least their respective light detectors 45, 49 may be adapted for transmitting an actuation signal towards other components of the elevator arrangement 1. Such signal transmission may be implemented using hardwiring or wireless techniques.

For example, a signal output by one of the light detectors 45, 49 may be transmitted towards the elevator controller 13 such that the elevator controller 13 may control the operation of the drive engine 9 in accordance with such signals.

In a specific implementation, the light detectors 45, 49 may for example be hardwired to a landing operation panel (LOP) 39 at the lowermost floor 61. From there, any sensor signals may be forwarded for example towards the elevator controller 13 communicating with this LOP 39.

Alternatively or additionally, signals output by one of the light detectors 45, 49 may be transmitted to a remote control centre 41 being external to the elevator arrangement 1 such that for example any future inspections of the elevator arrangement 1 may be suitably planned at such remote control centre 41 taking into account the signals of at least one of the light detectors 45, 49.

In the embodiment shown in the figures in various perspectives, the light sources 43, 47 and light detectors 45, 49 of the lower limit sensor arrangement 27 and the pre-limit sensor arrangement 29, respectively, are arranged at a first guide rail 25 and at an opposite second guide rail 26 of the elevator arrangement 1 using fixation brackets 57. Accordingly, the light rays 44, 48 formed by the lower limit light barrier arrangement 42 and the pre-limit light barrier arrangement 46, respectively, cross a space between these opposing guide rails 25, 26 such that the counterweight 5 guided by these guide rails 25,

26 first actuates the pre-limit sensor arrangement 29 and then actuates the lower limit sensor arrangement 27 upon being displaced downwards beyond its intended lowermost allowable position towards the predetermined lower limit position 31. This is visualised in Fig.l and 2 with the arrow representing a travelling distance 69 and in Fig. 3 with a downward projection 55 of the counterweight 5 shown as a dotted rectangle.

By using the additional hardware including the lower limit sensor arrangement 27 and, optionally, the pre-limit sensor arrangement 29 and optionally using some additional software, beneficial embodiments of a method for monitoring the minimum counterweight-buffer- distance and/or of a method for determining the minimum counterweight-buffer- distance may be implemented.

First, an embodiment of the method for monitoring the minimum counterweight-buffer- distance shall be described.

In normal operation, when the elevator cabin 3 has been driven to the uppermost floor 63 and, therefore, the counterweight 5 is at its lowermost allowable position close to the lowermost floor 61, the light rays 44, 48 of both, the lower limit light barrier arrangement 42 and the pre-limit light barrier arrangement 46 remain uninterrupted. This indicates permissible minimum counterweight-buffer- distances 37 on the counterweight side.

Over a period of time, for example the STM 15 may lengthen such that the minimum counterweight-buffer- distance 37 may go below a permissible value of for example 140 mm, this value corresponding to the distance 51 between the lower limit position 31 and the pre-limit position 33. In such situation, the counterweight 5 interrupts the light ray 48 of the pre-limit light barrier arrangement 46 when the elevator cabin 3 is on the uppermost floor 63. Accordingly, upon being actuated in such way, the pre- limit sensor arrangement 29 outputs a warning signal. This warning signal may be transmitted for example towards the remote control centre 41. Upon receiving such warning signal, a technician in the remote control centre 41 may realise that there is a need for the technician’s visit at the elevator arrangement 1.

Alternatively, the warning signal of the pre-limit sensor arrangement 29 may be transmitted to another elevator component such as for example to the landing operating panel 39. Upon receiving such warning signal, a message may be issued at the landing operating panel 39. For example, the LOP 39 may display the message“inspection required” or similar on a screen. Upon reading such message, for example a user may call a technician for visiting the elevator arrangement 1.

While waiting for the technician’s visit, the elevator arrangement 1 may continue its normal operation. During the subsequent visit, the technician may inspect the elevator arrangement 1 and, if necessary, may initiate corrective actions. For example, the technician may correct the minimum counterweight-buffer-distance 37 e.g. by lifting the counterweight 5 and shortening a fixation to the STM 15, i.e. by for example an effective belt adjustment.

In case, the belt adjustment is not taken care of in due time, the belts of the STM 15 may further elongate such that, sooner or later, the counterweight 5, when positioned at its lowermost position, approaches the lower limit position 31.

In such situation, the counterweight 5 does not only touch the stopper plate 21 of the buffer 17 but, furthermore, interrupts the light ray 44 of the lower limit light barrier arrangement 42. The lower limit sensor arrangement 27 then outputs an alarming signal.

Such alarming signal may be transmitted for example towards the elevator controller 13. As a reaction thereto, the elevator controller 13 may modify an operation status of the elevator arrangement 1. For example, the elevator controller 13 may immediately stop the entire operation of the elevator arrangement 1. A call back for a technician visit may be generated and may either be communicated by a user or using remote monitoring approach. Alternatively, the elevator controller 13 may be put to a restricted use in which the uppermost floor 63 is no more served by the elevator cabin 3. Optionally, a normal call back may be generated.

Next, an embodiment of the method for determining the actual minimum counterweight- buffer-distance shall be described.

In an example of the proposed method, the elevator cabin 3 may first be driven to the uppermost floor 63. For that purpose, a technician visiting the elevator arrangement 1 may take the elevator cabin 3 to the topmost landing using e.g. a normal cabin call. At that stage, an elevator cabin level difference with respect to a floor level (corresponding to a landing sil) may be measured.

Subsequently, the technician may set the elevator arrangement into an installation operation mode, for example by setting a special command in a human-machine- interface. In such installation operation mode, the elevator cabin 3 may be allowed to travel upwards beyond a normal upper end of its travel path. Accordingly, the elevator cabin 3 is then further driven in an upward direction, using for example a recall panel. Such upward motion is continued until, when the elevator cabin 3 reaches an upper limit cabin position 65, the alarming signal is issued by the lower limit sensor arrangement 27 due to the fact that the counterweight 5 was displaced beyond the predetermined lower limit position 31 and therefore actuates the lower limit sensor arrangement 27. Until such moment, the elevator cabin 3 was displaced by a travelling distance 67. The travelling distance 67 of the elevator cabin 3 corresponds to a travelling distance 69 of the counterweight 5 of same length but opposite direction.

In reaction to receiving the alarming signal, the elevator controller 13 immediately stops the motion of the drive engine 9. Accordingly, the elevator cabin 3 immediately stops as soon as the light ray 44 of the lower limit light barrier arrangement 42 is interrupted by the counterweight 5.

The technician may then measure the elevator cabin level difference with respect to the floor level (landing sil). For example, the technician may measure the corresponding travelling distance 67 manually, for example using a scale. In other words, a value by which the elevator cabin 5 has gone upwards with respect to the actual floor level may be calculated. Such value corresponding to the travelling distance 67 will be the same as the minimum counterweight-buffer- distance 37 of the counterweight side.

Accordingly, with the proposed method, a need for a pit entry for measuring the minimum counterweight-buffer- distance may be eliminated. Furthermore, a need for a second technician may be eliminated. A simple scale may be used for measuring a travelling distance 67 corresponding to the minimum counterweight-buffer- distance 37. This may be done while the technician is standing on the landing. A motion of the elevator cabin 3 may be under full control of the technician. Implementing embodiments of the proposed method may require minimal costs and/or minimal changes in software or hardware.

Finally, it should be noted that the term“comprising” does not exclude other elements or steps and the“a” or“an” does not exclude a plurality. Also, elements described in association with different embodiments may be combined. It should also be noted that reference signs in the claims should not be construed as limiting the scope of the claims. List of reference signs

1 elevator arrangement

3 elevator cabin

5 counterweight

7 elevator shaft

8 pit

9 drive engine

11 traction sheave

13 elevator controller

15 suspension traction media

17 buffer

19 stopper lever

20 spring

21 stopper plate

23 guide shoe

25 guide rail

27 lower limit sensor arrangement

29 pre-limit sensor arrangement

31 lower limit position

33 pre-limit position

35 lowermost end of the counterweight

37 minimum counterweight-buffer- distance

39 landing operating panel

41 remote control centre

42 lower limit light barrier arrangement

43 light source of lower limit sensor arrangement

44 light ray of lower limit light barrier arrangement

45 light detector of lower limit sensor arrangement

46 pre-limit light barrier arrangement

47 light source of pre-limit sensor arrangement

48 light ray of pre-limit light barrier arrangement

49 light detector of pre-limit sensor arrangement 51 distance from lower limit position to pre- limit position

53 distance from pre-limit position to lowermost end of counterweight

55 downward projection of the counterweight

57 fixation bracket

59 floor

61 lowermost floor

63 uppermost floor

65 upper limit cabin position

67 travelling distance of elevator cabin

69 travelling distance of counterweight

Claims

Claims:

1. Elevator arrangement (1), comprising:

an elevator cabin (3);

a counterweight (5);

a drive engine (9);

an elevator controller (13);

elongate suspension traction media (15) extending between the elevator cabin (3) and the counterweight (5) such as to displace the elevator cabin (3) and the counterweight (5) along opposite travel paths upon the suspension traction media (15) being displaced by the drive engine (9) under control of the elevator controller (13);

a buffer (17) with a stopper lever (19) arranged at a lower end of the travel path of the counterweight (5) such as to support the counterweight (5) with the stopper lever (19) upon the counterweight (5) being displaced downwards beyond a predetermined lower limit position (31); and

a lower limit sensor arrangement (27) being positioned and configured such as to be actuated upon the counterweight (5) being displaced downwards beyond the

predetermined lower limit position (31). 2. Elevator arrangement of claim 1, further comprising a pre- limit sensor arrangement (29) being positioned and configured such as to be actuated upon the counterweight (5) being displaced downwards beyond a predetermined pre-limit position (33), the predetermined pre-limit position (33) being upwards of the predetermined lower limit position (31).

3. Elevator arrangement of claim 2, wherein the predetermined pre- limit position (33) is positioned at least 5cm upwards of the predetermined lower limit position (31).

4. Elevator arrangement of one of claims 2 and 3, wherein the pre-limit sensor arrangement (29) is configured for outputting a warning signal upon being actuated.

5. Elevator arrangement of claim 4, wherein the pre-limit sensor arrangement (29) is configured for transmitting the warning signal to a remote control centre (41).

6. Elevator arrangement of one of the preceding claims, wherein the lower limit sensor arrangement (27) is configured for outputting an alarming signal upon being actuated. 7. Elevator arrangement of claim 6, wherein the lower limit sensor arrangement

(27) is configured for transmitting the alarming signal to the elevator controller (13).

8. Elevator arrangement of one of the preceding claims, wherein at least one of the lower limit sensor arrangement (27) and the pre-limit sensor arrangement (29), respectively, comprises a light source (43, 47) and a light detector (45, 49) such as to form a light barrier crossing the travel path of the counterweight (5) at least at one of a height corresponding to the predetermined lower limit position (31) and a height corresponding to the predetermined pre-limit position (33), respectively. 9. Elevator arrangement of claim 8, wherein the light source (43, 47) is fixed to a first guide rail (25) and the light detector (45, 49) is fixed to a second guide rail (26), the first and second guide rails (25, 26) being arranged at opposite sides with respect to the travel path of the counterweight (5) for guiding the counterweight (5) upon being displaced along the travel path.

10. Method for determining a minimum counterweight-buffer-distance (37) in an elevator arrangement (1) according to one of claims 1 to 9, the minimum counterweight- buffer-distance (37) extending between a lowermost end (35) of the counterweight (5) and the stopper lever (19) of the buffer (17), the method comprising:

driving the elevator cabin (3) to an uppermost floor (63);

further driving the elevator cabin (3) in an upward direction until, at an upper limit cabin position (65), an alarming signal is issued by the lower limit sensor arrangement (27) upon being actuated due to the counterweight (5) being displaced downwards beyond the predetermined lower limit position (31);

measuring a travelling distance (67) travelled by the elevator cabin (3) upon being displaced between the uppermost floor (63) and the upper limit cabin position (67); and determining the minimum counterweight-buffer- distance (37) as being equal to the measured travelling distance (67).

11. Method of claim 10, wherein the travelling distance (67) is measured manually by a technician.

12. Method for monitoring a minimum counterweight-buffer- distance (37) in an elevator arrangement (1) according to claim 2, wherein a warning signal for requesting inspection is issued and transmitted to a remote control centre (41) upon the pre-limit sensor arrangement (29) being actuated.

13. Method of claim 12, wherein an alarming signal for requesting modification of an operation status of the elevator arrangement (1) is issued and transmitted to the elevator controller (13) upon the lower limit sensor arrangement (27) being actuated.