Patent Grant
11511969
The invention concerns in general the technical field of elevators. Especially the invention concerns safety of elevators.
Elevators comprise suspension means, such as a rope or a belt, for carrying an elevator car. Traditionally, steel ropes have been used as the elevator ropes. Typically, the ropes or belts elongates during the use of the elevator. The elongation is a result from a normal wear, fatigue etc. The elongation of the ropes or belts causes that the condition of the ropes or belts deteriorates during the use of the elevator. Thus, at some point the elongated ropes or belts needs to be replaced. If the elongated rope or belt is not replaced, there will be a potential risk of a serious accident.
Typically, condition, such as deterioration or ending of the lifetime, of the steel ropes has been recognized visually in situ for example by counting wire breaks of the rope, by measuring a diameter of the rope, by measuring rust output from the rope, and/or by measuring the size of the wear lenses of the wires of the rope. However, if the steel ropes are coated for example with a polyurethane coating, the traditional recognition methods may not be used or the traditional recognition methods are not reliable. For example, the wire breaks of the rope may remain hidden under the coating. Furthermore, nowadays the manual recognition methods should be replaced with automated method in order to enhance the safety of the elevators.
Furthermore, according to some prior art solutions the condition of the suspension means may be defined or monitored by measuring the electrical resistance of the suspension means, determining the stiffness of the suspension means, or by ac voltage measurements.
Thus, there is a need for further development of the recognition methods of condition of the elevator suspension means, such as ropes or belts.
An objective of the invention is to present a method, an elevator safety control unit, and an elevator system for defining a condition of an elevator car suspension means. Another objective of the invention is that the method, the elevator safety control unit, and the elevator system for defining a condition of an elevator car suspension means improve at least partly the safety of the elevators.
The objectives of the invention are reached by a method, an elevator safety control unit, and an elevator system as defined by the respective independent claims.
According to a first aspect a method for defining a condition of an elevator car suspension means is provided, wherein the method comprises detecting a rate of change of elongation of the elevator car suspension means in order to define the condition of the elevator car suspension means.
The method may comprise: obtaining periodically a value representing the elongation of the elevator car suspension means; defining a change value representing a rate of change of the elongation of the elevator car suspension means as a function of time based on the periodically obtained values representing the elongation of the elevator car suspension means; and generating, in response to a detection that the change value meets a limit for allowed change, an indication representing a change of the condition of the elevator car suspension means.
The limit for the allowed change may be defined based on previously defined change values.
The value representing the elongation of the elevator car suspension means may be one of the following: an overtravel distance of the elevator car, a distance between the elevator car and a counterweight along the elevator car suspension means, a position of the counterweight.
The change value representing the rate of change of the elongation of the elevator car suspension means may be one of the following: rate of change of the elongation of the elevator car suspension means, change of an overtravel distance of the elevator car, change of a distance between the elevator car and a counterweight along the elevator car suspension means, change in a position of the counterweight.
Furthermore, the indication may comprise an instruction to take the elevator car out of service and/or to replace the elevator car suspension means with a new elevator car suspension means.
According to a second aspect, an elevator safety control unit for defining a condition of an elevator car suspension means is provided, the elevator safety control unit comprising: at least one processor, and at least one memory storing at least one portion of computer program code, wherein the at least one processor being configured to cause the elevator safety control unit at least to detect a rate of change of elongation of the elevator car suspension means in order to define the condition of the elevator car suspension means.
The elevator safety control unit may be configured to: obtain periodically a value representing the elongation of the elevator car suspension means; define a change value representing a rate of change of the elongation of the elevator car suspension means as a function of time based on the periodically obtained values representing the elongation of the elevator car suspension means; and generate, in response to a detection that the change value meets a limit for allowed change, an indication representing a change of the condition of the elevator car suspension means.
The limit for the allowed change may be defined based on previously defined change values.
The value representing the elongation of the elevator car suspension means may be one of the following: an overtravel distance of the elevator car, a distance between the elevator car and a counterweight along the elevator car suspension means, a position of the counterweight.
The change value representing the rate of change of the elongation of the elevator car suspension means may be one of the following: rate of change of the elongation of the elevator car suspension means, change of an overtravel distance of the elevator car, change of a distance between the elevator car and a counterweight along the elevator car suspension means, change in a position of the counterweight.
Furthermore, the indication may comprise an instruction to take the elevator car out of service and/or to replace the elevator car suspension means with a new elevator car suspension means.
According to a third aspect, an elevator system for defining a condition of an elevator car suspension means is provided, wherein the elevator system comprising: an elevator car, an elevator suspension means for carrying the elevator car, and an elevator safety control unit, wherein the safety control unit is configured to detect a rate of change of elongation of the elevator car suspension means in order to define the condition of the elevator car suspension means.
The elevator system may further comprise an elevator service unit, wherein the elevator safety control unit may be configured to: obtain periodically a value representing the elongation of the elevator car suspension means, and wherein the elevator safety control unit or the elevator service unit may be configured to: define a change value representing a rate of change of the elongation of the elevator car suspension means as a function of time based on the periodically obtained values representing the elongation of the elevator car suspension means; and generate, in response to a detection that the change value meets a limit for allowed change, an indication representing a change of the condition of the elevator car suspension means.
Alternatively, the elevator system may further comprise an elevator service unit, wherein the elevator safety control unit may be configured to: obtain periodically a value representing the elongation of the elevator car suspension means, and define a change value representing a rate of change of the elongation of the elevator car suspension means as a function of time based on the periodically obtained values representing the elongation of the elevator car suspension means; and wherein the elevator service unit may configured to: generate, in response to a detection that the change value meets a limit for allowed change, an indication representing a change of the condition of the elevator car suspension means.
The exemplary embodiments of the invention presented in this patent application are not to be interpreted to pose limitations to the applicability of the appended claims. The verb “to comprise” is used in this patent application as an open limitation that does not exclude the existence of also un-recited features. The features recited in depending claims are mutually freely combinable unless otherwise explicitly stated.
The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objectives and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.
The embodiments of the invention are illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings.
The elevator system 200 according to the invention may further comprise an elevator control unit 214 that may be configured to control the operation of the elevator system 200. The elevator control unit 214 may reside in a machine room 216. According to one embodiment a safety control unit 218 according to the invention may be implemented as a part of the elevator control unit 214 as illustrated in
The elevator system 200 according to the invention may further comprise an external elevator service unit 219 that may be communicatively coupled to the elevator safety control unit 218. The communication between the elevator safety control unit 218 and the elevator service unit 219 may be based on one or more known communication technologies, either wired or wireless. The elevator service unit 219 may be for example a service center, service company or similar.
The method according to the invention enables defining a condition of the elevator car suspension means 210 by detecting a rate of change of elongation of the elevator car suspension means 210. The method according to the invention comprises detecting the rate of change of elongation of the elevator car suspension means 210 in order to define the condition of the elevator car suspension means 210, wherein the condition of the elevator suspension means 210 may be for example ending of the lifetime.
Next an example of a method according to the invention is described by referring to
The limit for the allowed change may be defined based on previously defined change values, i.e. a history data defined based on the periodically obtained values representing the elongation of the elevator car suspension means 210. After a strong elongation of the elevator car suspension means 210 (when they are new) the rate of change of the elongation of the elevator car suspension means 210 stabilizes and remains substantially steady. Then rate of change of the elongation of the elevator car suspension means 210 is substantially small and substantially constant. Thus, the limit for the allowed change may be defined to be the substantially constant rate of change of the elongation of the elevator car suspension means 210, when rate of change of the elongation of the elevator car suspension means 210 is stable and steady. Alternatively or in addition, the limit for the allowed change may be the constant rate of change of the elongation of the elevator car suspension means 210, when the change of the overtravel distance is stable and steady, added with a margin of error. When the rate of change of the elongation of the elevator car suspension means 210 starts to increase again, it is an indication that the condition of the elevator car suspension means 210 has changed, i.e. the lifetime of the elevator car suspension means 210 has ended.
Above it is described that the elevator safety control unit 218 performs all the method steps 302-308. Alternatively, the elevator safety control unit 218 may communicate the obtained values representing the elongation of the elevator car suspension means 210 to the elevator service unit 219. The elevator service unit 219 may then perform the method steps 304-308, namely definition 304 of the change value and generation 308 of the indication in response to the detection 306 that the change value meets the limit for allowed change. Alternatively or in addition, the elevator safety control unit 218 may perform the method steps 302 and 304 and the defined change value representing the rate of change of the elongation of the elevator car suspension means 210 may be communicated to the elevator service unit 219. After that the elevator service unit 219 may perform for example the method steps 306 and 308.
The communication between the elevator safety control unit 218 and the elevator service unit 219 may be continuous, i.e. real-time communication. Alternatively or in addition, the data, i.e. obtained values representing the elongation of the elevator car suspension means 210 and/or defined change values, may be communicated from the elevator safety control unit 218 to the elevator service unit 219 according to a predefined time scheme. The communication of the data according to the predefined time scheme means that the data is not communicated continuously or in real-time. Instead the data may be communicated at a time instant, which the elevator safety control unit 218 or the elevator service unit 219 defines to be suitable for the communication. The suitable time instant may be for example one of the following: regular time interval, irregular time interval, when no data memory of the elevator safety control unit 218 is full or almost full.
According to one embodiment of the invention the rate of change of the elongation of the elevator car suspension means may be detected by observing an overtravel distance of the elevator car, i.e. the obtained value representing the elongation of the elevator suspension means 210 is the overtravel distance of the elevator car.
When the elevator system is installed or the elevator car suspension means 210 are replaced with new elevator car suspension means 210, the length of the elevator car suspension means 210 is adjusted so that when the elevator car 202 is at the top floor 208a, the counterweight 212 is configured to be a predefined overtravel distance, i.e. an initial value for the overtravel distance, from a buffer 220 of the counterweight 212 arranged at the bottom of the elevator shaft 206. The predefined overtravel distance may be defined so that the predefined overtravel distance is more than an operating distance of a final limit switch, i.e. a distance between the operating point of the final limit switch and the roof level of the top floor 208a. The elevator system 200 may comprise the final limit switch arranged to the elevator shaft within a door zone above the top floor 208a. The final limit switch is configured to stop the movement of the elevator car 202 in either direction, if the elevator car 202 reaches the operating point of the final limit switch. Furthermore, the operating distance of the final limit switch may be preferably defined to be as short as possible, but the final limit switch may not be arranged too close to the roof level of the top floor so that the movement of the elevator car 202 is not stopped too easily, because it may reduce the availability of the elevators.
During the use of the elevator the elevator suspension means 210 elongates, which in turn causes that the overtravel distance decreases. Next one example for obtaining a value representing the overtravel distance is described. First the elevator car 202 that is empty is driven to the top floor 208a and the elevator is taken out of the normal operation. Next the elevator car 202 is driven upwards with a reduced speed until the counterweight 212 reaches the buffer 220. The reduced speed may be for example less than 0.25 m/s. A detection of a change in a torque of a hoisting motor indicates that the counterweight 212 reaches the buffer 220. The overtravel distance corresponds to the distance travelled by the elevator car 202 upwards from the top floor 208a up to the detection of the change in the torque of the hoisting motor indicating that the counterweight 212 comes into a contact with the buffer 220. The overtravel distance may be obtained for example with the elevator safety control unit 218. After obtaining the overtravel distance, the elevator car 202 is driven back to the top floor 208a and the elevator is returned back to the normal operation. The above described example is non-limiting example and the present invention is not limited to that. Thus, the overtravel distance may be obtained also by any other way.
Next an example of detecting the rate of change of the elongation of the elevator car suspension means by observing the overtravel distance of the elevator car is described by referring to
The limit for the allowed change of the overtravel distance may be defined based on previously defined change of the overtravel distance, i.e. a history data defined based on the periodically obtained values representing the overtravel distance of the elevator car 202.
When the rate of change of the elongation of the elevator car suspension means 210 starts to increase again, the overtravel distance starts to decrease steeper than previously obtained overtravel distance, i.e. the slope of the curve 402 starts to increase, which is an indication that the condition of the elevator car suspension means 210 has changed, i.e. the lifetime of the elevator car suspension means 210 has ended. This point is illustrated in
As described above the elevator safety control unit 218 may perform all the method steps 402-408. Alternatively, the elevator safety control unit 218 may communicate the periodically obtained overtravel distances to the elevator service unit 219 and the elevator service unit 219 may perform the of the method steps 404-408, namely definition 404 of the change of the overtravel distance and generation 408 of the indication in response to the detection 406 that the change value meets the limit for allowed change. Alternatively or in addition, the elevator safety control unit 218 may perform the method steps 402 and 404 and the defined change value representing the rate of change of the elongation of the elevator car suspension means 210 may be communicated to the elevator service unit 219. After that the elevator service unit 219 may perform for example the method steps 406 and 408.
According to another embodiment of the invention the rate of change of the elongation of the elevator car suspension means 210 may be detected by observing a distance between the elevator car 202 and the counterweight 212 along the elevator suspension means 210. Next this embodiment is described by referring to
The safety control unit 218 defines 604 a change value representing the rate of change of the elongation of the elevator car suspension means as a function of time based on the periodically obtained the distances between the elevator car 202 and the counterweight 212, wherein the change value is a change of the distance between the elevator car 202 and a counterweight 212 along the elevator suspension means 210. In response to a detection 606 that the change of the distance between the elevator car 202 and the counterweight 212 along the elevator suspension means 210 meets a limit for allowed change of the distance between the elevator car 202 and the counterweight 212 the safety control unit 218 generates 608 an indication representing a change of the condition of the elevator car suspension means 210. The change of the condition of the elevator car suspension means 210 may represent that the lifetime of the elevator car suspension means 210 is facing the end.
The limit for allowed change of the distance between the elevator car 202 and the counterweight 212 along the elevator suspension means 210 may be defined based on previously defined change of the distance between the elevator car 202 and the counterweight 212 along the elevator suspension means 210. As described above after a strong elongation of the elevator car suspension means 210 (when they are new) the rate of change of the elongation of the elevator car suspension means 210 stabilizes and remains substantially steady. It means that the distance between the elevator car 202 and the counterweight along the elevator car suspension means 210 changes, i.e. increases, gradually and substantially constantly as the time passes because of the elongation of the elevator car suspension means 210. Thus the limit for allowed change of the distance between the elevator car 202 and the counterweight 212 along the elevator suspension means 210 may be defined to be the constant change of the distance between the elevator car 202 and the counterweight 212, when the change of the distance is substantially constant. Furthermore, the limit for the allowed change of the distance between the elevator car 202 and the counterweight 212 may be the constant change of the distance between the elevator car 202 and the counterweight 212 along the elevator suspension means 210, when the change of the distance is substantially constant, added with a margin of error.
When the rate of change of the elongation of the elevator car suspension means 210 starts to increase again, the distance between the elevator car 202 and the counterweight 212 along the elevator suspension means 210 starts to change, i.e. increase, more strongly than previously, which is an indication that the condition of the elevator car suspension means 210 has changed, i.e. the lifetime of the elevator car suspension means 210 has ended. Thus, the detection that the change of the distance between the elevator car 202 and the counterweight 212 along the elevator suspension means 210 meets the limit for allowed change of distance between the elevator car 202 and the counterweight 212 indicates that the rate of change of the elongation of the elevator car suspension means 210 starts to increase, which in turn means that the condition of the elevator car suspension means 210 has changed.
As describe above the elevator safety control unit 218 may perform all the method steps 602-608. Alternatively, the elevator safety control unit 218 may communicate the obtained position information of the elevator car 202 and counterweight 212 or the obtained distance between the elevator car and the counter weight 212 along the elevator suspension means 210 to the elevator service unit 219 and the elevator service unit 219 may perform the of the method steps 604-608, namely definition 604 of the change of the distance between the elevator car 202 and the counterweight 212 and generation 608 of the indication in response to the detection 606 that the change value meets a limit for allowed change. Alternatively or in addition, the elevator safety control unit 218 may perform the method steps 602 and 604 and the defined change value representing the rate of change of the elongation of the elevator car suspension means 210 may be communicated to the elevator service unit 219. After that the elevator service unit 219 may perform for example the method steps 606 and 608.
The above described embodiments of the present invention enable implementation of defining the condition of the elevator car suspension means by using already existing components of the elevator system 200.
According to another embodiment of the invention the rate of change of the elongation of the elevator car suspension means 210 may be detected by observing a position of the counterweight 212. Next this embodiment is described by referring to
The safety control unit 218 defines 704 a change value representing the rate of change of the elongation of the elevator car suspension means 210 as a function of time based on the periodically obtained the positions of the counterweight 212, wherein the change value is a change of the position of the counterweight 212. In response to a detection 706 that the change of position of the counterweight 212 meets a limit for allowed change of the position of the counterweight 212, the safety control unit 218 generates 608 an indication representing a change of the condition of the elevator car suspension means 210. The change of the condition of the elevator car suspension means 210 may represent that the lifetime of the elevator car suspension means 210 is facing the end.
The limit for allowed change of the position of the counterweight 212 in relation to the fixed reference position may be defined based on previously defined change of the position of the counterweight 212 in relation to the fixed reference position. As described above after a strong elongation of the elevator car suspension means 210 (when they are new) the rate of change of the elongation of the elevator car suspension means 210 stabilizes and remains substantially steady. It means that the position of the counterweight 212 in relation to the fixed reference position changes, gradually and substantially constantly as the time passes because of the elongation of the elevator car suspension means 210. Thus, the limit for allowed change of position of the counterweight 212 in relation to the fixed reference position may be defined to be the constant change of the position of the counterweight 212 in relation to the fixed reference position, when the change of the position of the counterweight 212 in relation to the fixed reference position is substantially constant. Furthermore, the limit for the allowed change of the position of the counterweight 212 in relation to the fixed reference position may be the constant change of the position of the counterweight 212 in relation to the fixed reference position, when the change of the position of the counterweight 212 in relation to the fixed reference position is substantially constant, added with a margin of error.
When the rate of change of the elongation of the elevator car suspension means 210 starts to increase again, the position of the counterweight 212 in relation to the fixed reference position starts to change, more strongly than previously, which is an indication that the condition of the elevator car suspension means 210 has changed, i.e. the lifetime of the elevator car suspension means 210 has ended. Thus, the detection that the change of the position of the counterweight 212 in relation to the fixed reference position meets the limit for allowed change of the position of the counterweight 212 in relation to the fixed reference position indicates that the rate of change of the elongation of the elevator car suspension means 210 starts to increase, which in turn means that the condition of the elevator car suspension means 210 has changed.
As describe above the elevator safety control unit 218 may perform all the method steps 702-708. Alternatively, the elevator safety control unit 218 may communicate the obtained position information of the counterweight 212 to the elevator service unit 219 and the elevator service unit 219 may perform the of the method steps 704-708, namely definition 704 of the change of the position of the counterweight 212 in relation to the fixed reference position and generation 708 of the indication in response to the detection 706 that the change value meets a limit for allowed change. Alternatively or in addition, the elevator safety control unit 218 may perform the method steps 702 and 704 and the defined change value representing the rate of change of the elongation of the elevator car suspension means 210 may be communicated to the elevator service unit 219. After that the elevator service unit 219 may perform for example the method steps 706 and 708.
The indication generated at the steps 308, 408, 608, or 708 may comprise an instruction to take the elevator car 202 out of service and/or to replace the elevator car suspension means 210 with a new elevator car suspension means. The indication, such as a control signal, may be generated for the elevator control unit 214 in order to stop the operation of the elevator. Furthermore, the elevator car 202 may be instructed to stop at the nearest floor 208a-208n and to leave doors open. Alternatively or in addition, the indication, such as a control signal, may be generated to the elevator service unit 219. Preferably, the generated indication may be transmitted to the elevator service unit 219 in real time. In response to receiving the indication the elevator service unit 219 may be configured to instruct maintenance personnel to inspect the condition of the elevator car suspension means 210 and/or to replace the elevator car suspension means 210 with a new elevator car suspension means. This enables a condition-based maintenance. Alternatively or in addition, the indication or may be for example a visual indication or sound indication for a service or maintenance personnel to inspect the condition of the elevator car suspension means 210 and/or to replace the elevator car suspension means 210 with a new elevator car suspension means.
The present invention as hereby described provides great advantages over the prior art solutions. For example, the present invention improves at least partly the safety of the elevators. Furthermore, the present invention enables an automated method for a condition-based maintenance. Alternatively or in addition the present invention enables an automated method for defining the condition of the elevator car suspension means. This also allows that the monitoring of a condition of the elevator car suspension means may be performed remotely, which in turn improves at least partly the availability of the elevators, because less maintenance breaks for performing condition inspections for the elevator car suspension means are needed. Furthermore, the present invention enables defining the condition of a coated rope or a belt. Moreover, at least some embodiments of the present invention enables implementation of defining the condition of the elevator car suspension means by using already existing components of the elevator system. Thus, additional expensive components are not needed. The use of already existing components of the elevator system 200 that meet good Safety Integrity Level (SIL) accuracy requirements enables that the condition of the elevator car suspension means may be defined so that good SIL accuracy requirements are met. SIL may be used to indicate a tolerable failure rate of a particular safety function, for example a safety component. SIL is defined as a relative level of risk-reduction provided by the safety function, or to specify a target level of risk reduction. SIL has a number scheme from 1 to 4 to represent its levels. The higher the SIL level is, the greater the impact of a failure is and the lower the failure rate that is acceptable is.
The term “normal operation” of an elevator is used in this patent application to mean the operation of the elevator, wherein the elevator car is configured to drive in the elevator shaft between floors in order to serve passengers and/or to carry loads. The normal operation of the elevator covers also the time periods, when the elevator car is configured to wait at a floor an instruction to move to another floor.
The term “door zone” is used in this patent application to mean a zone extending from a lower limit below floor level to an upper limit above the floor level in which a landing door and an elevator car door are in mesh and operable. The door zone may be determined to be from −400 mm to +400 mm for example. Preferably, the door zone may be from −150 mm to +150 mm. When arriving to the door zone the elevator car is allowed to begin to open the doors even before the elevator car is stopped.
The verb “meet” in context of a limit is used in this patent application to mean that a predefined condition is fulfilled. For example, the predefined condition may be that the limit for allowed change is reached and/or exceeded.
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.
This application is a Continuation of PCT International Application No. PCT/US2017/054022, filed on Sep. 28, 2017, which is hereby expressly incorporated by reference into the present application.
| Number | Name | Date | Kind |
|---|---|---|---|
| 6073728 | Olsen | Jun 2000 | A |
| 20170022028 | Cortona | Jan 2017 | A1 |
| Number | Date | Country |
|---|---|---|
| 106660741 | May 2017 | CN |
| 11 2015 003 122 | Mar 2017 | DE |
| 5-262474 | Oct 1993 | JP |
| 6-144744 | May 1994 | JP |
| 2012-171776 | Sep 2012 | JP |
| 2012171776 | Sep 2012 | JP |
| WO-2016002370 | Jan 2016 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 20200223667 A1 | Jul 2020 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/US2017/054022 | Sep 2017 | US |
| Child | 16832568 | US |
