A buffer condition monitoring solution for an elevator

Abstract

The invention relates to a method for condition monitoring of an elevator buffer device (116, 118) of an elevator entity (102, 108). The method comprises: controlling (210) an elevator hoisting machinery system to drive the elevator entity (102, 108) to compress the elevator buffer device (116, 118); recording (220) a torque data of an elevator hoisting motor of the elevator hoisting machinery system during the compression of the elevator buffer device (116, 118) of the elevator entity (102, 108); and condition monitoring (230) of the elevator buffer device (116, 118) based on the recorded torque data. The invention relates also to an elevator control system (110) for condition monitoring of an elevator buffer device (116, 118) of an elevator entity (102, 108).

Description

[0001] A BUFFER CONDITION MONITORING SOLUTION FOR AN ELEVATOR

[0002] TECHNICAL FIELD

[0003] The invention concerns in general the technical field of elevators. Especially the invention concerns condition monitoring of elevator buffer devices.

[0004] BACKGROUND

[0005] An elevator system comprises an elevator car configured to travel along an elevator shaft between floors. The elevator system further comprises a buffer device arranged in a pit of the elevator shaft to soften stopping of a motion the elevator car, if the elevator car attempts to run over a bottom floor towards the pit. Further, a separate buffer device is provided in the pit to soften stopping of a motion of a counterweight, if the elevator car attempts to run over a top floor towards a top of the elevator shaft, by absorbing kinetic energy of the counterweight.

[0006] Elevator shaft space efficiency can be improved by reducing the height of headroom at the shaft top and pit at the shaft bottom. Reduced shaft end spaces require that enhanced safety measures at shaft ends be provided and maintained. For example, reducing pit height by using reduced buffers requires that the elevator overspeed monitoring is able to reduce the overspeed limit towards the shaft end. As one consequence of such developments, operational tolerances of elevator functionalities and components become less forgiving. The hoisting ropes are such a critical component the condition of which needs to be monitored carefully. In case of a reduced pit, it is the gradual stretching, in particular, that must be monitored. There is a requirement for free space between the counterweight and its buffer when the car is at the top landing to make sure that there will be no unintentional collision between the counterweight and its buffer.

[0007] Typically, the condition of the buffer devices may be inspected during maintenance visits, e.g. by a maintenance person. In order to be able to inspect the condition of the buffer devices, the maintenance person needs to enter the pit of the elevator shaft to make a visual check manually. The frequency of the need for inspection may depend on the type of the buffer device. For example, certain polyurethane buffer devices may be sensitive to water and other materials, which causes damages to the buffer devices. Typically, a certain lifetime is given for the buffer devices, e.g. by the buffer device manufacturer. During the maintenance visit also some other inspections from inside the pit are typically performed. For example, the free space under the counterweight may be measured during the maintenance visits by the maintenance person to ensure that there is no risk for unintentional collision with the buffer device.

[0008] Nowadays low pit elevator systems are becoming more common. In the low pit elevator systems, the inspections performed from inside the pit of the elevator shaft become challenging.

[0009] Therefore, there is a need to develop further solutions for condition monitoring elevator buffer devices.

[0010] SUMMARY

[0011] The following presents a simplified summary in order to provide basic understanding of some aspects of various invention embodiments. The summary is not an extensive overview of the invention. It is neither intended to identify key or critical elements of the invention nor to delineate the scope of the invention. The following summary merely presents some concepts of the invention in a simplified form as a prelude to a more detailed description of exemplifying embodiments of the invention.

[0012] An objective of the invention is to present a method and an elevator control system for condition monitoring of an elevator buffer device of an elevator entity. Another objective of the invention is that the method and the elevator control system for condition monitoring of an elevator buffer device of an elevator entity enable remote monitoring of the condition of the elevator buffer device.

[0013] The objectives of the invention are reached by a method and an elevator control system as defined by the respective independent claims.

[0014] According to a first aspect, a method for condition monitoring of an elevator buffer device of an elevator entity is provided, wherein the method comprises: controlling an elevator hoisting machinery system to drive the elevator entity to compress the elevator buffer device; recording a torque data of an elevator hoisting motor of the elevator hoisting machinery system during the compression of the elevator buffer device of the elevator entity; and condition monitoring of the elevator buffer device based on the recorded torque data. The condition monitoring of the elevator buffer device based on the recorded torque data may comprise: comparing the recorded torque data to reference torque data, and assessing the condition of the elevator buffer device based on the result of the comparison.

[0015] A difference between the recorded torque data and the reference torque data may indicate a deteriorated condition of the elevator buffer device.

[0016] The reference torque data may be defined during a commissioning of the elevator buffer device.

[0017] The elevator buffer device may comprise two or more buffer elements, and the condition monitoring of the elevator buffer device based on the recorded torque data may further comprise monitoring a condition similarity between the two or more buffer elements of the elevator buffer device.

[0018] A discontinuity in the recorded torque data may indicate dissimilarity in the condition of the two or more buffer elements of the elevator buffer device.

[0019] The elevator entity may be a counterweight, and the elevator buffer device may be a counterweight buffer device.

[0020] When the elevator entity is a counterweight, and the elevator buffer device is a counterweight buffer device, the method may further comprise measuring free space between the counterweight and the counterweight buffer device, when an elevator car is at a top floor.

[0021] The measuring of the free space between the counterweight and the counterweight buffer device may comprise: obtaining, from an encoder device, distance data representing a distance the elevator car is driven upwards from the top floor until the counterweight reaches the counterweight buffer device; and determining the free space between the counterweight and the counterweight buffer device based on the obtained distance data and the recorded torque data.

[0022] Alternatively, the elevator entity may be an elevator car, and the elevator buffer device may be an elevator car buffer device.

[0023] According to a second aspect, an elevator control system for condition monitoring of an elevator buffer device of an elevator entity is provided, wherein the elevator control system comprises: at least one processor; and at least one memory including computer program code; wherein the at least one memory and the computer program code are configured with the at least one processor, cause the elevator control system to perform: controlling an elevator hoisting machinery system to drive the elevator entity to compress the elevator buffer device; recording a torque data of an elevator hoisting motor of the elevator hoisting machinery system during the compression of the elevator buffer device; and condition monitoring of the elevator buffer device based on the monitored torque curve.

[0024] The condition monitoring of the elevator buffer device based on the recorded torque data may comprise that the elevator control system may be configured to: compare the recorded torque data to reference torque data, and asses the condition of the elevator buffer device based on the result of the comparison.

[0025] A difference between the recorded torque data and the reference torque data may indicate a deteriorated condition of the elevator buffer device.

[0026] The reference torque data may be defined during a commissioning of the elevator buffer device.

[0027] The elevator buffer device may comprise two or more buffer elements, and the condition monitoring of the elevator buffer device based on the recorded torque data may further comprise that the elevator control system may be configured to monitor a condition similarity between the two or more buffer elements of the elevator buffer device.

[0028] A discontinuity in the recorded torque data may indicate dissimilarity in the condition of the two or more buffer elements of the elevator buffer device.

[0029] The elevator entity may be a counterweight, and the elevator buffer device may be a counterweight buffer device.

[0030] When the elevator entity is a counterweight, and the elevator buffer device is a counterweight buffer device, the elevator control system may further be configured to measure free space between the counterweight and the counterweight buffer device, when an elevator car is at a top floor.

[0031] The measuring of the free space between the counterweight and the counterweight buffer device may comprise that the elevator control system may be configured to: obtain, from an encoder device, distance data representing a distance the elevator car is driven upwards from the top floor until the counterweight reaches the counterweight buffer device; and determine the free space between the counterweight and the counterweight buffer device based on the obtained distance data and the recorded torque data.

[0032] Alternatively, the elevator entity may be an elevator car, and the elevator buffer device may be an elevator car buffer device.

[0033] Various exemplifying and non-limiting embodiments of the invention both as to constructions and to methods of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific exemplifying and non-limiting embodiments when read in connection with the accompanying drawings.

[0034] The verbs “to comprise” and “to include” are used in this document as open limitations that neither exclude nor require the existence of unrecited features. The features recited in dependent claims are mutually freely combinable unless otherwise explicitly stated. Furthermore, it is to be understood that the use of “a” or “an”, i.e. a singular form, throughout this document does not exclude a plurality.

[0035] BRIEF DESCRIPTION OF FIGURES

[0036] The embodiments of the invention are illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings.

[0037] Figure 1 illustrates schematically an example of an elevator system.

[0038] Figure 2 illustrates schematically an example of a method for condition monitoring of an elevator buffer device of an elevator entity.

[0039] Figure 3 illustrates schematically a more detailed example of the method.

[0040] Figures 4-5 illustrate schematically other more detailed examples of the method.

[0041] Figure 6A illustrates schematically a simple example of the elevator system illustrating a free space between a counterweight and a counterweight buffer device. Figure 6B illustrates schematically a simple example of the elevator system illustrating a distance an elevator car is driven upwards from a top floor until a counterweight reaches a counterweight buffer device.

[0042] Figure 7 illustrates schematically yet another example of the method.

[0043] Figure 8 illustrates schematically an example of components of an elevator control system.

[0044] DESCRIPTION OF THE EXEMPLIFYING EMBODIMENTS

[0045] Figure 1 illustrates schematically an example of an elevator system 100. The elevator system 100 comprises an elevator car 102 configured to travel along an elevator shaft 104 between a plurality of floors (i.e. landings) 106a-106n, a counterweight 108, and an elevator control system 110. The elevator system 100 may also form an elevator group, i.e. group of two or more elevator cars 102 each travelling along a separate elevator shaft 104 configured to operate as a unit serving the same landings. The elevator system 100 further comprises a hoisting machinery system configured to drive the elevator car 102 along the elevator shaft 104 between the floors 106a-106n. The elevator hoisting machinery system may comprise for example an elevator hoisting motor (e.g. an electric motor) and a traction sheave 112 for lifting the elevator car 102. For illustrative purposes, only the traction sheave 112 of the elevator hoisting machinery system is shown in Figure 1A. The elevator car 102, the hoisting machinery system and the counterweight 108 are interconnected via an elevator hoisting rope arrangement 114 routed via a plurality of pulleys (for sake of clarity not shown in Figure 1 ), and the traction sheave 112. When the traction sheave 112 rotates, the elevator car 102 and the counterweight 108 are moving in a vertical direction (V) along the elevator shaft 104. The elevator hoisting rope arrangement 114 comprises at least one hoisting rope. The elevator system 100 further comprises a buffer device 116 for the elevator car 102 and a buffer device 118 for the counterweight 108. From now on throughout this application the buffer device 116 of the elevator car 102 is called an elevator car buffer device and the buffer device 118 of the counterweight 108 is called a counterweight buffer device. The elevator car buffer device 116 is arranged in the pit of the elevator shaft 104 to soften stopping of the motion of the elevator car 102, if the elevator car 102 attempts to run over a bottom floor 106a towards the pit, by absorbing kinetic energy of the elevator car 102. To soften the stopping of the motion of the elevator car 102 the elevator car buffer device 116 is compressed, when the elevator car 102 reaches, i.e. is driven against, the elevator car buffer device 116. Similarly, the counterweight buffer device 118 is arranged in the pit of the elevator shaft 104 to soften stopping of a motion of the counterweight 108, if the elevator car 102 attempts to run over a top floor 106n towards a top of the elevator shaft 104, by absorbing kinetic energy of the counterweight 108. To soften the stopping of the motion of the counterweight the counterweight buffer device 118 is compressed, when the counterweight 108 reaches, i.e. is driven against, the counterweight buffer device 118.

[0046] The elevator control system 110, e.g. an elevator controller, is configured at least to control the operations of the elevator system 100. The elevator control system 110 may be located inside a machine room 120 (as illustrated in the example of Figure 1 ) or at one of the floors 106a-106n, e.g. in a machine roomless elevator system. The elevator control system 110 is communicatively coupled to the other entities of the elevator system 100. The communication between the elevator control system 110 and the other entities of the elevator system 100 may be based on one or more known communication technologies, either wired or wireless. The implementation of the elevator control system 110 may be done as a stand-alone control entity or as a distributed control environment between a plurality of stand-alone control entities, such as a plurality of servers, providing distributed control resource. The elevator control system 110 may, for example, comprise one or more elevator controllers. The elevator control system 110 comprises an elevator drive system 122 for controlling the elevator hoisting motor of the elevator hoisting machinery system (e.g. power feed to the elevator hoisting motor, speed of the elevator hoisting motor, and torque of the elevator hoisting motor) in order to drive the elevator car 102 along the elevator shaft 104. The elevator system 100 may further comprise one or more known elevator related entities, e.g., user interface devices, elevator doors, sensor devices, safety circuit and devices, and / or elevator brakes, etc., which are not shown in Figure 1 for the sake of clarity. The elevator control system 110 may be communicatively coupled to a remote computing system 124. The communication between the elevator control system 110 and the remote computing system 124 may be based on one or more known communication technologies, either wired or wireless. The remote computing system 124 may, for example, comprise one or more computing entities located remotely from the elevator system 100. The remote computing system 124 may, for example, be at least one of the following: a cloud server, a service center, a data center, a remote monitoring system, a remote diagnostic system.

[0047] Next an example of a method for condition monitoring of an elevator buffer device 116, 118 of an elevator entity 102, 108 is described by referring to Figure 2. Figure 2 schematically illustrates the method as a flow chart. The method is performed by the elevator control system 110. The elevator entity 102, 108 may be the elevator car 102 or the counterweight 108. If the elevator entity 102, 108 is the elevator car 102, the elevator buffer device 116, 118 is the elevator car buffer device 116. If the elevator entity 102, 108 is the counterweight 108, the elevator buffer device 116, 118 is the counterweight buffer device 118. The elevator buffer device 116, 118 comprises at least one buffer element. The elevator buffer device 116, 118 may be a polyurethane (Pll) buffer, a spring buffer, or a hydraulic buffer, or any other type of a buffer device. The elevator buffer device 116, 118 implemented as the polyurethane buffer may comprise at least one polyurethane buffer element. The elevator buffer device 116, 118 implemented as the spring buffer may comprise at least one spring buffer element. The elevator buffer device 116, 118 implemented as the hydraulic buffer may comprise at least one hydraulic buffer element.

[0048] At step 210, the elevator control system 110 controls the elevator hoisting machinery system to drive the elevator entity 102, 108 to compress the respective elevator buffer device 116, 118. For example, the elevator drive system 122 of the elevator control system 110 may control the elevator hoisting motor of the elevator hoisting machinery system to drive the elevator entity 102, 108 to compress the elevator buffer device 116, 118. Because the elevator car 102 and the counterweight 108 are interconnected via the elevator hoisting rope arrangement 114, both elevator entities are driven at the same time, but in opposite directions. Thus, driving either one of the elevator entities 102, 108 upwards or downwards causes also that the other one of the elevator entities 102, 108 is driven downwards or upwards, respectively. In other words, when the elevator car 102 is driven upwards along the elevator shaft 104 the counterweight is driven downwards along the elevator shaft 104 at the same time, and vice versa. Due to safety reasons, the elevator car 102 is preferably empty, when the elevator entity 102, 108 is driven to compress the respective elevator buffer device 116, 118. If load (e.g. one or more passengers) is inside the elevator car 102, when the elevator entity 102, 108 is driven to compress the respective elevator buffer device, the mass of the elevator car 102 may be measured and the influence of the load of the elevator car 102 on torque data of the elevator hoisting motor of the elevator hoisting machinery system (that is recorded at step 220 as will be described) may be taken into account. The mass of the elevator car 102 may be measured using any elevator car load measurement method, for example, but not limited, by using a load weighing device.

[0049] At step 220, the elevator control system 110 records torque data of the elevator hoisting motor of the elevator hoisting machinery system during the compression the elevator buffer device 116, 118 of the elevator entity 102, 108. The torque data represents the torque of the elevator hoisting motor. The torque data may comprise a torque curve or one or more points of the torque curve. The torque curve represents the torque generated by the elevator hoisting motor as a function of time. The torque data may for example be determined by the drive system 122. The torque data may, for example, be determined based on electrical quantities of the elevator hoisting motor. The electrical quantities of the elevator motor comprise at least motor currents and motor voltages, i.e. currents and voltages supplied to the elevator hoisting motor. The electrical quantities of the elevator motor may further comprise frequencies of the motor currents and motor voltages.

[0050] When the elevator entity 102, 108 is driven to compress the respective elevator buffer device 116, 118, the buffer device 116, 118 starts to support the elevator entity 102, 108, which causes a change in an unbalance state at the traction sheave 112 of the elevator hoisting machinery system, which in turn causes that the torque of the elevator hoisting motor starts to change, e.g. increase. It may be assumed that the compression of the elevator buffer device 116, 118 follows substantially a behavior of an ideal spring. Especially when the elevator buffer device 116, 118 is a spring buffer, the compression of the elevator buffer device 116, 118 may be assumed to follow the behavior of the ideal spring. When the elevator buffer device 116, 118 is a Pll buffer or hydraulic buffer, the compression of the elevator buffer device 116, 118 does not necessarily fully follow the behavior of the ideal spring. However, also in case of the elevator buffer device 116, 118 being the Pll buffer or the hydraulic buffer, the compression of the elevator buffer device 116, 118 may be assumed to follow substantially the behavior of the ideal spring. When the elevator entity 102, 108 is driven to compress the respective elevator buffer device 116, 118, at the be- ginning the compression of the elevator buffer device 116, 118 is substantially linear. When the compression of the elevator buffer device 116, 118 is substantially linear, the change of the torque curve is also substantially linear and the slope of the torque curve may be determined based on a spring rate, i.e. spring constant, of the elevator buffer device 116, 118. The region, where the compression of the elevator buffer device 116, 118 is substantially linear, may be called as a linear region of the elevator buffer device 116, 118. When the elevator buffer device 116, 118 is compressed yet further, at some point the compression of the elevator buffer device 116, 118 is not substantially linear anymore, but starts to be non-linear instead. When the compression of the elevator buffer device 116, 118 is not linear anymore (i.e. outside the linear region of the elevator buffer device 116, 118), the spring constant does not apply anymore, which in turn means that the change of the torque curve is not substantially linear anymore, but starts to be non-linear instead. In other words, the change of the torque curve is assumed to be substantially linear, as long as it stays within the linear region of the elevator buffer device 116, 118.

[0051] At step 230, the elevator control system 110 monitors the condition of the elevator buffer device 116, 118 based on the recorded torque data. The condition monitoring of the elevator buffer device 116, 118 of the elevator entity 102, 108 may be performed periodically, e.g. according to a predefined schedule. For example, the condition monitoring may be performed predefined times per week, per month, or per year etc., e.g. once a month, or four times a year, etc. Alternatively or in addition, condition monitoring of the elevator buffer device 116, 118 of the elevator entity 102, 108 may be performed in response to receiving a control signal from the remote computing system 124. Figure 3 schematically illustrates the flow chart of Figure 2 in more detailed manner. Especially step 230, i.e. the step of monitoring the condition of the elevator buffer device 116, 118, becomes clear from Figure 3.

[0052] According to an example, the condition monitoring of the elevator buffer device 116, 118 based on the recorded torque data at step 230 may comprise monitoring a change of the torque data in comparison to reference torque data. This is performed at step 310, wherein the elevator control system 110 may monitor the change of the torque data in comparison to the reference torque data. Step 310 of monitoring the change of the torque data in comparison to the reference torque data is described more in detail in this application by referring to Figure 4. According to another example, the condition monitoring of the elevator buffer device 116, 118 based on the recorded torque data at step 230 may alternatively or in addition, comprise monitoring condition similarity between two or more buffer elements of the elevator buffer device 116, 118, if the elevator buffer device 116, 118 comprises two or more buffer elements. This is performed at step 320, wherein the elevator control system 110 may monitor the condition similarity between two or more buffer elements of the elevator buffer device 116, 118. Step 320 of monitoring the condition similarity is described more in detail in this application by referring to Figure 5.

[0053] Figure 4 illustrates schematically step 310, i.e. the step of monitoring the change of the torque data in comparison to reference torque data, of Figure 3 more in detail. At step 410, the elevator control system 110 compares the recorded torque data to the reference torque data. The reference torque data may be defined during a commissioning of the elevator buffer device 116, 118. When the elevator buffer device 116, 118 is taken in use, the elevator buffer device 116, 118 has a certain effect on the torque data, when the respective elevator entity 102, 108 is driven to compress the elevator buffer device 116, 118. However, in the course of time the condition of the elevator buffer device 116, 118 changes (e.g. deteriorates) due to, for example, buffer materials ageing. The change in the condition of the elevator buffer device 116, 118 causes a change in the effect of the elevator buffer device 116, 118 on the torque data. Thus, a change in the condition of the elevator buffer device 116, 118 may be detected based on the change in the torque data in comparison to the reference torque data. The reference torque data may comprise a reference torque curve or one or more points of the reference torque curve. The comparison of the recorded torque data and the reference torque data may comprise comparing one or more points of the torque curve comprised in the recorded torque data to the respective one or more points of the reference torque curve comprised in the reference torque data. If the recorded torque data comprises the torque curve and the reference torque data comprises the reference torque curve, the comparison of the recorded torque data and the reference torque data may comprise comparing the torque curve comprised in the recorded torque data to the reference torque curve comprised in the reference torque data. The reference torque data may, for example, be stored into a memory unit 820 of the elevator control system 110. Alternatively or in addition, the elevator control system 110 may provide the reference torque data to the remote computing system 124 and / or to a database for storing the reference torque data thereto.

[0054] At step 420, the elevator control system 110 may assess the condition of the elevator buffer device 116, 118 based on the result of the comparison at step 410. A difference between the recorded torque data and the reference torque data may indicate at step 430 a deteriorated condition of the elevator buffer device 116, 118. The difference between the recorded torque data and the reference torque data may, for example, appear as an increase in torque values in comparison to the reference torque data or as a decrease in torque values in comparison to the reference torque data. The deteriorated condition of the elevator buffer device 116, 118 means that the characteristics of the elevator buffer device 116, 118 have been changed substantially so that the elevator buffer device 116, 118 needs to be replaced with a new buffer device. Alternatively, no difference between the recorded torque data and the reference torque data may indicate at step 440 an acceptable condition of the elevator buffer device 116, 118. The acceptable condition of the elevator buffer device 116, 118 means that the characteristic of the elevator buffer device 116, 118 have not been changed at least substantially.

[0055] At step 450, the elevator control system 110 may generate a maintenance request in response to detecting, at step 430, the difference between the recorded torque data and the reference torque data (i.e. deteriorated condition of the elevator buffer device 116, 118). The maintenance request may, for example, comprise an instruction to replace the elevator buffer device 116, 118 with a new buffer device. The maintenance request may, for example, further comprise information representing the condition of the elevator buffer device 116, 118, e.g., the deterioration condition of the elevator buffer device 116, 118. The maintenance request may, for example, be generated to the remote computing system 124 and / or to maintenance personnel. The generation of the maintenance request in response to detecting, at step 430, the difference between the recorded torque data and the reference torque data (i.e. deteriorated condition of the elevator buffer device 116, 118) enables preventive maintenance of the elevator buffer device 116, 118, because the deteriorated condition of the buffer device 116, 118 may be detected and the maintenance personnel may be informed about the deteriorated condition of the elevator buffer device 116, 118 before a scheduled maintenance visit. Figure 5 illustrates schematically step 320, i.e. the step of monitoring the condition similarity, of Figure 3 more in detail. At step 510, the elevator control system 110 monitors the condition similarity between two or more buffer elements of the elevator buffer device 116, 118. A discontinuity, e.g., an abnormal shift, in the recorded torque data may indicate at step 520 dissimilarity in the condition of the two or more buffer elements of the elevator buffer device 116, 118. As discussed above, the change of the torque curve is assumed to be substantially linear as long as it stays within the linear region of the elevator buffer device 116, 118. However, in a situation where the elevator buffer device 116, 118 comprises two or more buffer elements, wherein the condition of at least one of the two or more buffer elements differs from the condition of the other buffer elements, the change of the torque curve may be substantially linear at the beginning, but a dissimilarity in the condition of the buffer elements of the elevator buffer device 116, 118, may cause a discontinuity in the torque curve. For example, if the elevator buffer device 116, 118 comprises two buffer elements, wherein one of the buffer elements (e.g. a second buffer element) has collapsed more than the other buffer element (e.g. a first buffer element), the change of the torque curve may be substantially linear, when the elevator entity 102, 108 starts to compress the first buffer element (i.e. the less collapsed buffer element), but when the elevator entity 102, 108 starts to compress also the second buffer element (i.e. the more collapsed buffer element) a distinguishable discontinuity in the torque curve, may be detected. Alternatively, if the discontinuity is not detected in the recorded torque data, it may indicate at step 530 similarity in the condition of the two or more buffer elements of the elevator buffer device 116, 118. The dissimilarity may, for example, be caused by a difference between the conditions of the two or more buffer elements. In other words, if the condition of the two or more buffer elements differs from each other, it causes the dissimilarity in the condition of the two or more buffer elements of the elevator buffer device 116, 118.The difference in the condition of the two or more buffer elements may, for example, be the amount of collapse, e.g., one or more of the buffer elements may be collapsed more than the other buffer elements, or any other difference in the condition of the two or more buffer elements. Alternatively or in addition, the dissimilarity may for example be caused by the two or more buffer elements being on different level. In other words, if top surfaces of the two or more buffer elements (i.e. the surfaces facing towards the elevator entity 102, 108) are on different level in the vertical direction, it may cause the dissimilarity in the condition of the two or more buffer elements of the elevator buffer device 116, 118.

[0056] At step 540, the elevator control system 110 may generate a maintenance request in response to detecting at step 520 the non-linear increase in the recorded torque data (i.e. dissimilarity in the condition of the two or more buffer elements of the elevator buffer device 116, 118). The maintenance request may, for example, comprise an instruction to replace at least one buffer element of the two or more buffer elements of the elevator buffer device 116, 118 with a new buffer element, replace the whole elevator buffer device 116, 118 with a new buffer device, and / or adjust the level of at least one buffer element of the two or more buffer elements of the elevator buffer device 116, 118. The maintenance request may, for example, further comprise information representing the dissimilarity in the condition of the two or more buffer elements. The maintenance request may, for example, be generated to the remote computing system 124 and / or to the maintenance personnel. The generation of the maintenance request in response to detecting at step 520 a non-linear increase in the recorded torque data (i.e. dissimilarity in the condition of the two or more buffer elements of the elevator buffer device 116, 118) enables preventive maintenance of the elevator buffer device 116, 118, because dissimilarity in the condition of the two or more buffer elements of the elevator buffer device 116, 118 may be detected and the maintenance personnel may be informed about the dissimilarity before a scheduled maintenance visit.

[0057] According to yet another example, wherein the elevator entity 102, 108 is the counterweight 108 and the elevator buffer device 116, 118 is the counterweight buffer device 118, the elevator control system 110 may further measure a free space between the counterweight 108 and the counterweight buffer device 118 (i.e. a free space under the counterweight 108), when the elevator car 102 is at the top floor 106n. The free space under the counterweight 108, when the elevator car 102 is at the top floor 106n, is the distance between the bottom surface of the counterweight 108 and the top surface of the counterweight buffer device 118. Figure 6A illustrates schematically a simple example of the elevator system 100 illustrating the free space (FS) between the counterweight 108 and the counterweight buffer device 118. The elevator system 100 of the example of Figure 6A may comprise the entities of the example elevator system 100 of Figure 1 and / or one or more other entities not shown in Figure 6A. Figure 7 illustrates schematically an example of the method for condition monitoring the elevator buffer device 116, 118 of the elevator entity 102, 108, wherein the method further comprises measuring of the free space between the counterweight 108 and the counterweight buffer device 118.

[0058] At step 710, the elevator control system 110 may obtain distance data. The elevator control system 110 may obtain the distance data from an encoder device 610. The encoder device 610 may be arranged to the elevator hoisting machinery system. The elevator control system 110 is communicatively coupled to the encoder device 610. The communication between the elevator control system 110 and encoder device 610 may be based on one or more known communication technologies, either wired or wireless. The obtained distance data represents a distance (D) the elevator car 102 is driven upwards from the top floor 106n until the counterweight 108 reaches the counterweight buffer device 118 (i.e. until the counterweight buffer device 118 begins to compress due to the counterweight 108). The elevator car 102 is driven upwards from the top floor 106n until the counterweight 108 reaches the counterweight buffer device 118 at step 210 as described above. Figure 6B illustrates schematically a simple example of the elevator system 100 illustrating the distance (D) the elevator car 102 is driven upwards from the top floor 106n until the counterweight 108 reaches the counterweight buffer device 118. The elevator system 100 of the example of Figure 6B may comprise the entities of the example elevator system 100 of Figure 1 and / or one or more other entities not shown in Figure 6B. The encoder device 610 may count the revolutions of the traction sheave 112 caused due driving of the elevator car 102 upwards from the top floor 106n until the counterweight 108 reaches the counterweight buffer device 118. The distance (D) travelled by the elevator car 102 upwards from the top floor 106n until the counterweight 108 reaches the counterweight buffer device 118 may be determined from the counted revolutions of the traction sheave 112. Because the vertical distance travelled by the counterweight 108 corresponds to the vertical distance travelled by the elevator car 102, the distance (D) corresponds to the free space (FS) between the counterweight 108 and the counterweight buffer device 118. After the obtaining the distance data the elevator control system 110 may record the torque data at step 220 as described above.

[0059] At step 720, the elevator control system 110 may determine the free space between the counterweight 108 and the counterweight buffer device 118 based on the obtained distance data and the recorded torque data. A starting point of the distance measurement is the point where the elevator car 102 is at the top floor 106n, and an end point of the distance measurement is the point where the counterweight 108 reaches the counterweight buffer device 118. The recorded torque data may be used to detect that the counterweight 108 reaches the counterweight buffer device 118, when the counterweight 108 is driven to compress the counterweight buffer device 118. In other words, the end point of the distance measurement may be determined based on the recorded torque data. As discussed above, when the counterweight 108 is driven to compress the counterweight buffer device 118, the buffer device 116, 118 starts to support the counterweight 108, which causes the change in the unbalance state at the traction sheave 112 of the elevator hoisting machinery system, which in turn causes that the torque of the elevator hoisting motor starts to change. This means that, when the counterweight 108 reaches the counterweight buffer device 118, it causes a noticeable change in the torque curve. Thus, a change in the torque data indicates that the counterweight reaches the counterweight buffer device 118.

[0060] At step 730, the elevator control system 110 may generate a maintenance request in response to detecting that the determined free space between the counterweight 108 and the counterweight buffer device 118 reaches and / or falls under a predefined free space limit. In other words, the elevator control system 110 may detect whether the determined free space between the counterweight 108 and the counterweight buffer device 118 reaches and / or falls under the predefined free space limit and if the elevator control system 110 detects that the determined free space between the counterweight 108 and the counterweight buffer device 118 reaches and / or falls under the predefined free space limit, the elevator control system 110 may generate the maintenance request. The maintenance request may, for example, comprise an instruction to adjust the free space between the counterweight 108 and the counterweight buffer device 118 by adjusting the length of the elevator ropes. The maintenance request may, for example, further comprise information representing the determined free space between the counterweight 108 and the counterweight buffer device 118. The maintenance request may, for example, be generated to the remote computing system 124 and / or to the maintenance personnel. The generation of the maintenance request in response to detecting at step 730 that the determined free space between the counterweight 108 and the counterweight buffer device 118 reaches and / or falls under the predefined free space limit enables preventive maintenance of the elevator system, because the reduced counterweight free space may be detected, and the maintenance personnel may be informed about the reduced free space before a scheduled maintenance visit.

[0061] In the example of Figure 7, step 230 (i.e. condition monitoring of the counterweight buffer device 118) is performed before step 720 (i.e. determining the free space). However, these method steps may also be performed in reverse order, i.e. step 720 may also be performed before step 230.

[0062] According to an example, the elevator control system 110 may further provide to the remote computing system 124 condition data comprising an indication of the results of the condition monitoring step 230 at least partly. This enables monitoring of the condition of the elevator buffer device 116, 118 of the elevator entity 102, 108 remotely from the elevator system 100. For example, the elevator control system 110 may provide to the remote computing system 124 condition data comprising an indication of the result of the assessment of the condition of the elevator buffer device 116, 118 at step 420, e.g. the deteriorated condition of the elevator buffer device 116, 118 or the acceptable condition of the elevator buffer device 116, 118. Alternatively or in addition, the elevator control system 110 may for example provide to the remote computing system 124 condition data comprising an indication of the result of the similarity assessment of the condition of the two or more buffer elements of the elevator buffer device 116, 118 at step 510, e.g. the dissimilarity in the condition of the two or more buffer elements of the elevator buffer device 116, 118 or the similarity in the condition of the two or more buffer elements of the elevator buffer device 116, 118. The elevator control system 110 may further provide to the remote computing system 124 condition data comprising an indication of the result of the determination of the free space between the counterweight 108 and the counterweight buffer device 118 at step 720, e.g. the determined free space between the counterweight 108 and the counterweight buffer device 118. This enables monitoring of the free space between the counterweight 108 and the counterweight buffer device 118 remotely from the elevator system 100.

[0063] According to another example, the elevator control system 110 may alternatively or in addition provide the recorded torque data to the remote computing system 124 to enable the condition monitoring of the elevator buffer device 116, 118 remotely from the elevator system 100. The remote computing system 124 may then perform the condition monitoring of the elevator buffer device based on the recorded torque data similarly as described above for the elevator control system 110. The elevator control system 110 may further provide the obtained distance data to the remote computing system 124 to enable measuring of the free space between the counterweight 108 and the counterweight buffer device 118 remotely from the elevator system 100. The remote computing system 124 may then perform the determination of the free space between the counterweight 108 and the counterweight buffer device 118 based on the distance data and the recorded torque data as described above for the elevator control system 110.

[0064] Figure 8 illustrates schematically an example of components of the elevator control system 110. The elevator control system 110 may comprise a processing unit 810 comprising one or more processors, the memory unit 820 comprising one or more memories, a communication unit 830 comprising one or more communication devices, and possibly a user interface (III) unit 840. The mentioned elements may be communicatively coupled to each other with e.g. a communication bus. The memory unit 820 may store and maintain portions of a computer program (code) 825, the recorded torque data, the reference torque data, the distance data, and any other data. The computer program 825 may comprise instructions which, when the computer program 825 is executed by the processing unit 810 of the elevator control system 110 may cause the processing unit 810, and thus the elevator control system 110 to carry out desired tasks, e.g. one or more of the method steps described above. The processing unit 810 may thus be arranged to access the memory unit 820 and retrieve and store any information therefrom and thereto. For sake of clarity, the processor herein refers to any unit suitable for processing information and control the operation of the elevator control system 110, among other tasks. The operations may also be implemented with a microcontroller solution with embedded software. Similarly, the memory unit 820 is not limited to a certain type of memory only, but any memory type suitable for storing the described pieces of information may be applied in the context of the present invention. The communication unit 830 provides one or more communication interfaces for communication with any other unit, e.g. the encoder device 610, other entities of the elevator system, one or more databases, and / or with any other unit. The user interface unit 840 may comprise one or more input / output (I / O) devices, such as buttons, keyboard, touch screen, microphone, loudspeaker, display and so on, for receiving user input and outputting information. The computer program 825 may be a computer program product that may be comprised in a tangible nonvolatile (non-transitory) computer-readable medium bearing the computer program code 825 embodied therein for use with a computer, i.e. the elevator control system 110.

[0065] The method and elevator control system 110 for condition monitoring of the elevator buffer device 116, 118 of the elevator entity 102, 108 described above enable remote monitoring of the condition of the buffer device elevator 116, 118, i.e. without a need to enter the pit of the elevator shaft 104 in order to be able to inspect the condition of the elevator buffer device 116, 118. This is especially beneficial in case of the low pit elevator systems having pit depth less than 500 millimeters. Furthermore, at least some of the embodiments enable remote monitoring of the free space between the counterweight 108 and the counterweight buffer device 118. As the condition of the elevator buffer device 116, 118 and / or the free space between the counterweight 108 and the counterweight buffer device 118 may be monitored remotely, the duration of the maintenance visits may be reduced, and the safety of the maintenance visits may be improved. Thus, also the inspection work needed to be performed at the elevator system 110 may be reduced. Furthermore, at least some of the embodiments enable preventive maintenance of elevator the buffer device 116, 118.

[0066] The specific examples provided in the description given above should not be construed as limiting the applicability and / or the interpretation of the appended claims. Lists and groups of examples provided in the description given above are not exhaustive unless otherwise explicitly stated.

Claims

CLAIMS1 . A method for condition monitoring of an elevator buffer device (116, 118) of an elevator entity (102, 108), the method comprising: controlling (210) an elevator hoisting machinery system to drive the elevator entity (102, 108) to compress the elevator buffer device (116, 118); recording (220) a torque data of an elevator hoisting motor of the elevator hoisting machinery system during the compression of the elevator buffer device (116, 118) of the elevator entity (102, 108); and condition monitoring (230) of the elevator buffer device (116, 118) based on the recorded torque data.

2. The method according to claim 1 , wherein the condition monitoring (230) of the elevator buffer device (116, 118) based on the recorded torque data comprises: comparing (410) the recorded torque data to reference torque data, and assessing (420) the condition of the elevator buffer device (116, 118) based on the result of the comparison.

3. The method according to claim 2, wherein a difference between the recorded torque data and the reference torque data indicates (430) a deteriorated condition of the elevator buffer device (116, 118).

4. The method according to any of claims 2 or 3, wherein the reference torque data is defined during a commissioning of the elevator buffer device (116, 118).

5. The method according to any of the preceding claims, wherein the elevator buffer device (116, 118) comprises two or more buffer elements, and wherein the condition monitoring (230) of the elevator buffer device (116, 118) based on the recorded torque data further comprises monitoring (320) a condition similarity between the two or more buffer elements of the elevator buffer device (116, 118).

6. The method according to claim 5, wherein a discontinuity in the recorded torque data indicates (520) dissimilarity in the condition of the two or more buffer elements of the elevator buffer device (116, 118).

7. The method according to any of the preceding claims, wherein the elevator entity (102, 108) is a counterweight (108), and the elevator buffer device (116, 118) is a counterweight buffer device (118).

8. The method according to claim 7, further comprising measuring free space between the counterweight (108) and the counterweight buffer device (118), when an elevator car (102) is at a top floor (106n).

9. The method according to claim 8, wherein the measuring of the free space between the counterweight (108) and the counterweight buffer device (118) comprises: obtaining (710), from an encoder device (610), distance data representing a distance the elevator car (102) is driven upwards from the top floor (106n) until the counterweight (108) reaches the counterweight buffer device (118); and determining (720) the free space between the counterweight (108) and the counterweight buffer device (118) based on the obtained distance data and the recorded torque data.

10. The method according to any of claims 1 to 6, wherein the elevator entity (102, 108) is an elevator car (102), and the elevator buffer device (116, 118) is an elevator car buffer device (116).

11. An elevator control system (110) for condition monitoring of an elevator buffer device (116, 118) of an elevator entity (102, 108), the elevator control system (110) comprising: at least one processor (810); and at least one memory (820) including computer program code (825); wherein the at least one memory (820) and the computer program code (825) are configured with the at least one processor (810), cause the elevator control system (110) to perform:controlling an elevator hoisting machinery system to drive the elevator entity (102, 108) to compress the elevator buffer device (116, 118); recording a torque data of an elevator hoisting motor of the elevator hoisting machinery system during the compression of the elevator buffer device (116, 118); and condition monitoring of the elevator buffer device (116, 118) based on the monitored torque curve.

12. The elevator control system (110) according to claim 11 , wherein the condition monitoring of the elevator buffer device (116, 118) based on the recorded torque data comprises that the elevator control system (110) is configured to: compare the recorded torque data to reference torque data, and asses the condition of the elevator buffer device (116, 118) based on the result of the comparison.

13. The elevator control system (110) according to claim 12, wherein a difference between the recorded torque data and the reference torque data indicates a deteriorated condition of the elevator buffer device (116, 118).

14. The elevator control system (110) according to any of claims 12 or 13, wherein the reference torque data is defined during a commissioning of the elevator buffer device (116, 118).

15. The elevator control system (110) according to any of claims 11 to 14, wherein the elevator buffer device (116, 118) comprises two or more buffer elements, and wherein the condition monitoring of the elevator buffer device (116, 118) based on the recorded torque data further comprises that the elevator control system (110) is configured to monitor a condition similarity between the two or more buffer elements of the elevator buffer device (116, 118).

16. The elevator control system (110) according to claim 15, wherein a discontinuity in the recorded torque data indicates dissimilarity in the condition of the two or more buffer elements of the elevator buffer device (116, 118).

17. The elevator control system (110) according to any of claims 11 to 16, wherein the elevator entity (102, 108) is a counterweight (108), and the elevator buffer device (116, 118) is a counterweight buffer device (118).

18. The elevator control system (110) according to claim 17, further configured to measure free space between the counterweight (108) and the counterweight buffer device (118), when an elevator car (102) is at a top floor (106n).

19. The elevator control system (110) according to claim 18, wherein the measuring of the free space between the counterweight (108) and the counterweight buffer device (118) comprises that the elevator control system (110) is configured to: obtain, from an encoder device (610), distance data representing a distance the elevator car (102) is driven upwards from the top floor (106n) until the counterweight (108) reaches the counterweight buffer device (118); and determine the free space between the counterweight (108) and the counterweight buffer device (118) based on the obtained distance data and the recorded torque data.

20. The elevator control system according to any of claims 11 to 16, wherein the elevator entity (102, 108) is an elevator car (102), and the elevator buffer device (116, 118) is an elevator car buffer device (116).

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