Patent Application
20200180910
The invention concerns in general the technical field of elevators. Especially the invention concerns safety of elevators.
Typically an elevator system comprises an elevator car and a hoisting machine configured to drive the elevator car in an elevator shaft between floors. Furthermore, the elevator system comprises suspension means, such as a rope or a belt, for carrying, i.e. suspending the elevator car and a counterweight. For example, the elevator car may be arranged to one end of the elevator car suspension means and a counterweight may be arranged to the other end of the elevator car suspension means. Alternatively, the elevator car and the counterweight may be suspended with the elevator car suspension means by means of one or more diverter pulleys. Furthermore, the elevator system may comprise a final limit switch arranged to the elevator shaft within a door zone above the top floor. The final limit switch is configured to stop the movement of the elevator car in either direction, if the elevator car reaches an operating point of the final limit switch.
When the elevator system is installed or the elevator car suspension means are replaced with new elevator car suspension means, the length of the elevator car suspension means may be adjusted so that when the elevator car is at the top floor, the counterweight is configured to be a predefined overtravel distance from a buffer of the counterweight arranged at the bottom of the elevator shaft.
During the use of the elevator, the elevator suspension means elongates. Typically, the elevator suspension means elongate strongly, when they are new. After that the elongation stabilizes and remains substantially small until the lifetime of the rope or belt approaches to the end and the elongation of the rope or belt starts to increase again.
According to elevator safety regulations the final limit switch shall actuate, i.e. stop the movement of the elevator car, before the counterweight comes into contact with the buffer. When elevator suspension means have elongated so that the final limit switch does not stop the movement of the elevator car before the counterweight comes into contact with the buffer, the elevator does not fulfill the elevator safety requirements and it should be taken out of operation. In that case the counterweight comes into contact with the buffer before the final limit switch actuates. The elevator suspension means may be shortened so that the safety regulations are fulfilled again.
According to one prior art solution the operation of the final limit switch and a mechanical safety device is monitored and if it is detected that the operation of the final limit switch or the operation of the mechanical safety device do not fulfill the regulations anymore, the elevator is taken out of the operation. At least one disadvantage of the prior art solution is that the failure in the operation of the final limit switch is not detected until the elevator is required to be taken out of the operation.
An objective of the invention is to present a method and elevator system for defining an elongation of an elevator car suspension means. Another objective of the invention is that the method and elevator system for defining an elongation 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 and an elevator system as defined by the respective independent claims.
According to a first aspect, a method for defining elongation of an elevator car suspension means is provided, wherein the method comprises: obtaining periodically a value representing an overtravel distance of the elevator car, and defining the elongation of the elevator car suspension means on a basis of the periodically obtained values representing the overtravel distance of the elevator car.
The method may further comprise: defining a longtime trend of the overtravel distance on a basis of the periodically obtained values representing the overtravel distance, and defining a suitable moment for adjusting the length of the elevator car suspension means on a basis of the defined longtime trend.
Moreover, the method may further comprise defining the longtime trend on a basis of at least one elevator type specific parameter of said elevator together with the periodically obtained values representing the overtravel distance, wherein the at least one elevator type specific parameter may be at least one of the following: operating distance of a final limit switch, travel height, suspension ratio, load, number of ropes, type of ropes.
Alternatively or in addition, the method may comprise generating a first signal indicating a need for adjusting the length of the elevator car suspension means for an elevator service unit, in response to a detection that the periodically obtained value representing the overtravel distance meets a predefined first limit for the overtravel distance.
Moreover, the method may further comprise generating a second signal comprising an instruction to take the elevator car out of service for an elevator control unit, in response to a detection of that the periodically obtained value representing the overtravel distance meets a predefined second limit for the overtravel distance.
The value representing the overtravel distance may obtained by overcoupling a final limit switch arranged to the elevator shaft above the top floor; driving the elevator car upwards from a top floor until a counterweight comes into a contact with a buffer; and obtaining a distance travelled by the elevator car from the top floor up to a detection of an indication that the counterweight comes into a contact with the buffer, wherein said distance corresponds to the value representing the overtravel distance of the elevator car.
The indication may be detected by means of one of the following: detection of a change in a torque of a hoisting motor, detection of a movement of the buffer by means of a switch arranged to the buffer.
The method may further comprise: obtaining periodically a value representing settling of an elevator shaft, and defining the elongation of the elevator car suspension means on a basis of the periodically obtained values representing the overtravel distance of the elevator car and the periodically obtained values representing the settling of the elevator shaft, wherein the value representing the settling of the elevator shaft may be obtained by measuring the distance between top of the elevator shaft and a counterweight by means of a long-range distance meter, when the counterweight locates at a predefined reference location.
Alternatively or in addition, the method may further comprise obtaining an operating distance of a final limit switch in order to verify actual operating position of the final limit switch.
According to a second aspect, an elevator system for defining elongation of an elevator car suspension means is provided, the elevator system comprises: an elevator car, an elevator suspension means for carrying the elevator car, an elevator service unit, and an elevator safety control unit, wherein the elevator safety control unit is configured to obtain periodically a value representing an overtravel distance of the elevator car, and wherein the elevator safety control unit or the elevator service unit is configured to define the elongation of the elevator car suspension means on a basis of the periodically obtained values representing the overtravel distance of the elevator car.
The elevator safety control unit or the elevator service unit may further be configured to: define a longtime trend of the overtravel distance on a basis of the periodically obtained value representing the overtravel distance, and define a suitable moment for adjusting the length of the elevator car suspension means on a basis of the defined longtime trend.
Moreover, the elevator safety control unit or the elevator service unit may further be configured to define the longtime trend on a basis of at least one elevator type specific parameter of said elevator together with the periodically obtained values representing the overtravel distance, wherein the at least one elevator type specific parameter may be at least one of the following: operating distance of a final limit switch, travel height, suspension ratio, load, number of ropes, type of ropes.
Alternatively or in addition, the elevator safety control unit may be configured to generate a first signal comprising an instruction to take the elevator car out of service for an elevator control unit, in response to a detection that the obtained value representing the overtravel distance meets a predefined second limit for the overtravel distance.
Moreover, the elevator safety control unit may further be configured to generate a second signal comprising an instruction to take the elevator car out of service for an elevator control unit, in response to a detection that the obtained value representing the overtravel distance meets a predefined second limit for the overtravel distance.
The value representing the overtravel distance may be obtained by: overcoupling a final limit switch arranged to the elevator shaft above the top floor; driving the elevator car upwards from a top floor until a counterweight comes into a contact with a buffer; and obtaining a distance travelled by the elevator car from the top floor up to a detection of an indication that the counterweight comes into a contact with the buffer, wherein said distance corresponds to the value representing the overtravel distance of the elevator car.
The indication may be detected by means of one of the following: detection of a change in a torque of a hoisting motor, detection of a movement of the buffer by means of a switch arranged to the buffer.
The elevator safety control unit may further be configured to obtain periodically a value representing settling of an elevator shaft, wherein the elevator safety control unit or the elevator service unit may be configured to define the elongation of the elevator car suspension means on a basis of the periodically obtained values representing the overtravel distance of the elevator car and the periodically obtained values representing the settling of the elevator shaft, and wherein the system may comprise a long-range distance meter arranged to a top of the elevator shaft and configured to provide the value representing the settling of the elevator shaft by measuring the distance between top of the elevator shaft and a counterweight, when the counterweight locates at a predefined reference location.
Alternatively or in addition, the elevator safety control unit may further be configured to obtain an operating distance of a final limit switch in order to verify actual operating position of the final limit switch.
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 100 according to the invention may further comprise an elevator control unit 114 that may be configured to control the operation of the elevator system 100. The elevator control unit 114 may reside in a machine room 116. According to one embodiment a safety control unit 118 according to the invention may be implemented as a part of the elevator control unit 114 as illustrated in
The elevator system 100 according to the invention may further comprise an external elevator service unit 119 that may be communicatively coupled to the elevator safety control unit 118. The communication between the elevator safety control unit 118 and the elevator service unit 119 may be based on one or more known communication technologies, either wired or wireless. The elevator service unit 119 may be for example a service center, service company or similar.
Furthermore, the elevator system 100 according to the invention may comprise a final limit switch 120 arranged to the elevator shaft 106 within a door zone above the top floor 108a. The final limit switch 120 may be configured to stop the movement of the elevator car 102 in either direction, if the elevator car 102 reaches an operating point of the final limit switch 120.
The method according to the invention enables defining elongation of an elevator car suspension means 110 by monitoring an overtravel distance of the elevator car 102. Next an example of a method according to the invention is described by referring to
However, in case of an elevator of a newly built building, the overtravel distance may also change because of the settling of the building after the construction. Especially buildings made of concrete suffer from settling. The settling of the building occurs mainly during the first year of the building. The settling of the building causes also settling of the elevator shaft 106 arranged inside the building. The settling of the elevator shaft 106, in turn, may cause bending or compression of guide rails that are mounted in the elevator shaft 106 to guide the travel of the elevator car 102. The guide rails may be mounted, for example to the walls of the elevator shaft 106. In order to avoid the bending of the guide rails because of the settling of the elevator shaft, the guide rails are adjusted, i.e. remounted to the elevator shaft 106. By measuring the settling of the building, the remounting points of the guide rails may be defined. The settling may be defined by measuring distance between the top of the elevator shaft 106 and the counterweight 112.
In order to take into account the settling, the elevator safety control unit 118 obtains 203 periodically a value representing settling of the elevator shaft 106. The elevator system 100 may comprise a long-range distance meter 124 arranged at the top of the elevator shaft 106 to provide the value representing the settling of the elevator shaft 106. The long-range distance meter 124 may be arranged for example to the machine room 116 or to the ceiling of the elevator shaft 106. The long-range distance meter 124 may be for example a laser or Ultra Wideband (UWB) radio. When the counterweight 112 locates at a predefined reference location, the long-range distance meter 124 may be used to measure the distance between the top of the elevator shaft 106 and the counterweight 112. The measured distance is compared to an initial distance between the top of the elevator shaft 106 and the counterweight 112 measured, when the elevator system 100 is installed, and the difference between the measured distance and the initial distance corresponds to the settling of the elevator shaft 106. The predefined reference location of the counterweight 112 may be for example the location, where the counterweight 212 makes a contact with the buffer 220. The value representing the settling of the elevator shaft 106 may be obtained at regular or irregular intervals of time, i.e. the obtaining is repeated after a particular period of time. Alternatively or in addition, the value representing the settling of the elevator shaft 106 may be obtained every time, when the counterweight 112 locates at the reference position. Alternatively or in addition, the value representing the settling of the elevator shaft 106 may be obtained simultaneously with the overtravel distance measurement.
Moreover, in order to define the elongation of the elevator car suspension means 110 from the obtained overtravel distance, the portion caused by the settling of the building is removed from the obtained overtravel distance. As discussed above the settling of the building and the elevator shaft 106 occurs mainly during the first year of the building. Therefore, the measurement of the settling of the elevator shaft 106 is needed only until it may be noticed that the settling of the building and the elevator shaft 106 settles down, i.e. the settling of the building and the elevator shaft ends.
The defined elongation of the elevator car suspension means 110 may be an absolute value of the elongation of the elevator car suspension means 110 and/or rate of change of the elongation of the elevator car suspension means 110.
Alternatively or in addition, the elevator safety control unit 118 may communicate the obtained values to the elevator service unit 119 after the step 202 and the elevator service unit 119 may perform the step 204, i.e. define the elongation of the elevator car suspension means 110 on a basis of the periodically obtained values representing the overtravel distance of the elevator car 102. The communication between the elevator safety control unit 118 and the elevator service unit 119 may be continuous, i.e. real-time communication. Alternatively or in addition, the data, i.e. obtained overtravel distances and/or defined elongation of the elevator car suspension means 110, may be communicated from the elevator safety control unit 118 to the elevator service unit 119 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 118 or the elevator service unit 119 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 118 is full or almost full.
In case of One to One (1:1) roping the change of the overtravel distance is directly proportional to the elongation of the elevator car suspension means 110. In 1:1 roping one end of elevator suspension means 110 passes from the elevator car 102 over the pulley, i.e. the traction sheave, of the hoisting machine 104, over the secondary or divertor sheave, and then to the counterweight 112. With 1:1 roping the elevator car 102, counterweight 112, and the elevator suspension means 110 all travel at the same speed. In case of any other ropings, such as 1:2 roping, the elongation of the elevator car suspension means 110 may be defined by taking into account also a suspension ratio of the elevator suspension means 110 in addition to the overtravel distance.
When the elevator system is installed or the elevator car suspension means 110 are replaced with new elevator car suspension means 110, the length of the elevator car suspension means 110 is adjusted so that when the elevator car 102 is at the top floor 108a the counterweight 112 is configured to be a predefined overtravel distance, i.e. an initial value for the overtravel distance, from a buffer 122 of the counterweight 112 arranged at the bottom of the elevator shaft 106. The predefined overtravel distance may be defined so that the predefined overtravel distance is more than the operating distance of the final limit switch 120, i.e. the distance between the operating point of the final limit switch 120 and the roof level of the top floor 108a. If the predefined overtravel distance is equal or less than the operating distance of the final limit switch 120, the final limit switch 120 is not able to actuate, i.e. stop the movement of the elevator car 102, before the counterweight 112 comes into contact with the buffer 122. In that case the overtravel distance is less than the operating distance of the final limit switch 120 and the elevator safety regulations are not fulfilled. Furthermore, the operating distance of the final limit switch 120 may be preferably defined to be as short as possible, but the final limit switch 120 may not be arranged too close to the roof level of the top floor 108a so that the movement of the elevator car 102 is not stopped too easily, because it may reduce the availability of the elevators.
During the use of the elevator the elevator suspension means 110 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 102 that is empty is driven to the top floor 108a and the elevator is taken out of the normal operation. Furthermore, the final limit switch 120 is overcoupled in order to allow the elevator car pass the final limit switch 120 so that the final limit switch 120 does not stop the movement of the elevator car 102. Next the elevator car 202 is driven upwards with a reduced speed until the counterweight 112 reaches the buffer 122. The reduced speed may be for example less than 0.25 m/s. The overtravel distance corresponds to the distance travelled by the elevator car 102 upwards from the top floor 208 up to the detection of an indication that the counterweight 212 comes into a contact with the buffer 220. According to an embodiment of the invention a detection of a change in a torque of a hoisting motor indicates that the counterweight 112 reaches the buffer 122. The overtravel distance may be obtained for example with the elevator safety control unit 118. According to another embodiment of the invention a switch arranged to the buffer may be used to detect a movement of the buffer to indicate that the counterweight 112 reaches the buffer 122, i.e. comes into contact with the buffer 122. After obtaining the overtravel distance, the elevator car 102 is driven back to the top floor 108 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. The overtravel distance may be obtained at regular or irregular intervals of time, i.e. the obtaining is repeated after a period of time.
As discussed above, the distance between the top of the elevator shaft 106 and the counterweight 112 may be measured when the counterweight locates at a predefined reference location, e.g. when the counterweight 112 makes contact with the buffer 220, to provide the value representing the settling of the elevator shaft 106. The above described procedures to detect an indication that the counterweight 212 comes into a contact with the buffer 220 may also be used to detect that the counterweight 112 locates at the reference location for the measurement of the distance between the top of the elevator shaft 106 and the counterweight 112 to provide the value representing the settling of the elevator shaft 106.
Alternatively or in addition, the operating distance of the final limit switch 120 may be obtained concurrently with the overtravel distance. A distance travelled by the elevator car 102 from the top floor 108a up to the operating point of the final limit switch 120 corresponds to the operating distance of the final limit switch 120. The operation distance of the final limit switch 120 does not change during the use of the elevator. Thus, the periodical monitoring of the operation distance of the final limit switch 120 is not needed similarly as the periodical monitoring of the overtravel distance. However, the operating distance of the final limit switch 120 may be obtained at least once after the installation of the elevator system in order to ensure that the final limit switch 120 is arranged, i.e. installed, at the intended operating position of the final limit switch. This enables that the actual operating distance of the final limit switch 120 may be obtained and verified after the installation of the elevator.
The method according to the invention may further enable defining a suitable moment for adjusting, i.e. shortening, the length of the elevator car suspension means.
Furthermore, the elevator service unit 118 may generate a control signal for the elevator service unit 119, wherein the control signal comprises at least the suitable moment for adjusting the length of the elevator car suspension means 110. In response to receiving the control signal the elevator service unit 119 may be configured to instruct maintenance personnel to adjust the length of the elevator car suspension means 110. After adjusting the length of the elevator car suspension means 110 the elevator car may be returned back to the normal operation.
Alternatively or in addition, if the safety control unit 118 communicates the obtained values to the elevator service unit 119 after the step 202 the elevator safety service unit 119 may perform the steps 402 and 404, i.e. define the longtime trend and the suitable moment for adjusting the length of the elevator car suspension means 110. In response to defining the suitable moment for adjusting the length of the elevator car suspension means 110 the elevator service unit 119 may be configured to instruct maintenance personnel to adjust the length of the elevator car suspension means 110. After adjusting the length of the elevator car suspension means 110 the elevator car may be returned back to the normal operation.
In addition the longtime trend may be defined on a basis of at least one elevator type specific parameter of said elevator together with the periodically obtained values representing the overtravel distance. The at least one elevator type specific parameter may be at least one of the following: operating distance of the final limit switch 120, travel height, suspension ratio of the elevator car suspension means 110, load, number of ropes, type of rope(s) or belt.
The suitable moment for adjusting the elevator car suspension means 110 may be defined on a basis of the defined longtime trend so that the suitable moment is sufficiently before the overtravel distance is predicted to meet, i.e. be equal to or less than, the operating distance of the final limit switch 120.
Preferably the suitable moment for adjusting the elevator car suspension means 110 is defined so that the unavailability of the elevators may be minimized. The time frame allows that the maintenance, i.e. adjusting the length of the elevator car suspension means 110, may be provided when it suits best for the users of the elevator and/or the maintenance personnel. In the example illustrated in
Next another example of the method according to the invention for defining a suitable moment for adjusting the length of the elevator car suspension means is described by referring to
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 a method for a condition-based maintenance. The present invention enables further an automated method for defining the elongation of the elevator car suspension means. Moreover, the present invention may enable further an automated method for defining a need and/or a suitable moment for adjusting, i.e. shortening, the length 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. Furthermore, the present invention may allow that the need and/or suitable moment for maintenance, i.e. for adjusting the length of the elevator car suspension means, may be provided in advance before the operation of the elevator car is stopped. Thus, the availability of the elevators may be at least partly improved, because less maintenance breaks for performing condition inspections for the elevator car suspension means are needed.
Moreover, the present invention may enable the implementation of defining elongation the elevator car suspension means and/or a need and/or a suitable moment for adjusting the length of the elevator car suspension means a 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 defining elongation the elevator car suspension means and/or a need and/or a suitable moment for adjusting the length 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 overtravel distance 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.
| Number | Date | Country | Kind |
|---|---|---|---|
| PCT/FI2017/050685 | Sep 2017 | FI | national |
This application is a continuation of PCT International Application No. PCT/FI2018/050439 which has an International filing date of Jun. 12, 2018, and which claims priority to PCT International Application No. PCT/FI2017/050685 filed Sep. 28, 2017, the entire contents of both of which are incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/FI2018/050439 | Jun 2018 | US |
| Child | 16789969 | US |
