Method and apparatus for monitoring elevator suspension rope condition

Abstract

A method for monitoring the condition of an elevator suspension rope (4), the elevator comprising: a car (2); a lifting machine (3) having a motor (32), a traction sheave (33) and a machine brake (34); one or more suspension ropes (4); and a counterweight (5); the car and the counterweight are suspended by said one or more ropes (4) guided over a single traction sheave (33) or a set of rotatable independent wheels comprised by the traction sheave for vertically moving the car (2) in the elevator shaft (1); the method comprises a) performing successive first and second measurement steps, in which in the first measurement step, the car (2) is parked to a first position (L1) in the shaft (1), in which position the total rope force (T1) on the car side is selected to be different from the total rope force (T2) on the counterweight side, and the car is locked in position in a vertically fixed manner relative to the shaft; enabling the traction rope wheel (33) or one of the independent wheels to rotate in the direction of a larger rope force (T1, T2); recording a first rotational angle difference ([delta] [phi] 1) of the traction sheave (33) or of the one independent wheel; and in a second measurement step: parking the car (2) to a second position (L2) in the shaft (1), in which position the total rope force (T1) on the car side is selected to be different from the total rope force (T2) on the counterweight side, and locking the car in position in a vertically fixed manner relative to the shaft; enabling the traction sheave (33) or the one independent sheave to rotate in the direction of a larger rope force (T1, T2); recording a second rotational angle difference ([delta] [phi] 2) of the traction sheave (33) or of the one independent wheel; and b) calculating a rope stiffness (EA) based on at least said first and said second measurements in at least two different vertical positions (L1, L2, Ln); c) indicating a rope condition based on the varying rope stiffness (EA). A device (100) for monitoring the condition of an elevator suspension rope (4).

Description

Technical Field

[0001] The invention relates to condition monitoring of suspension ropes of an elevator. The elevator is preferably an elevator for transporting passengers and / or freight. Background Art

[0002] An elevator may include a car, a shaft, a hoisting machine, suspension ropes and a counterweight. A separate or integrated car frame may surround the car.

[0003] A hoisting machine may be located in the shaft. The hoisting machine may include a drive, an electric motor, a traction sheave, and a mechanical brake. The hoisting machine may move the car up and down in the shaft. The mechanical brake may stop the rotation of the traction sheave, thereby stopping the movement of the elevator car.

[0004] The car frame can be connected to the counterweight by ropes via a traction sheave. The car frame can also be supported by guide members at guide rails extending in the vertical direction in the shaft. The guide rails can be attached to the side wall structure in the shaft with fastening brackets. When the car moves up and down in the shaft, the guide members keep the car in the appropriate position in the horizontal plane. The counterweight can be supported on the guide rails in a corresponding manner, and the guide rails are attached to the wall structure of the shaft.

[0005] The car may transport people and / or freight between landings of a building.The wall structure of the shaft may be formed by a solid wall or an open beam structure or any combination thereof.

[0006] Hoist suspension ropes have a limited lifespan due to wire breakage, rust and wear.

[0007] Reliable rope condition monitoring is required. Summary of the invention

[0008] An object of the present invention is to introduce an improved method and apparatus for condition monitoring of elevator suspension ropes.

[0009] Rope condition monitoring methods will be described based on stiffness measurements of the elevator suspension and the relationship between rope stiffness and life. Stiffness measurements utilize the car parking brake or safety equipment, and the elevator imbalance between the car and the counterweight. A decrease in rope stiffness indicates an increase in the number of wire breaks, which is a measure of the rope condition and remaining life.

[0010] The method according to the invention for monitoring the condition of a suspension rope of an elevator is defined in independent claim 1, wherein the elevator comprises

[0011] a car; a hoisting machine having a motor, a traction sheave and a machine brake; one or more slings; and a counterweight;

[0012] the car and the counterweight being suspended by said one or more ropes, which are guided over a single traction sheave or a set of rotatable independent wheels comprised by the traction sheave, for moving the car vertically in the elevator shaft;

[0013] The method includes

[0014] a) performing a first measurement step and a second measurement step in succession, wherein in the first measurement step:

[0015] parking the car to a first position in the shaft in which the total rope force on the car side is selected to be different from the total rope force on the counterweight side and locking the car vertically fixedly in position relative to the shaft;

[0016] Enables the traction sheave or one of the independent sheaves to rotate in the direction of greater rope force;

[0017] recording a first rotational angle difference of the traction sheave or the one independent wheel; and

[0018] In the second measurement step:

[0019] parking the car to a second position in the shaft in which the total rope force on the car side is selected to be different from the total rope force on the counterweight side and the car is locked vertically fixedly in position relative to the shaft;

[0020] enabling the traction sheave or said one independent wheel to rotate in the direction of greater rope force;

[0021] recording a second rotational angle difference of the traction sheave or the one independent wheel; and

[0022] b) calculating the rope stiffness based on at least said first measurement and said second measurement at at least two different vertical positions;

[0023] c) Indication of rope condition based on changing rope stiffness.

[0024] Preferred further details of the method are described below, which can be combined alone or in any combination with the device defined in independent claim 1 .

[0025] In a preferred embodiment, hardness measurement is performed automatically.

[0026] In a preferred embodiment, the method is programmed as a sequence in the elevator control system.

[0027] In a preferred embodiment the method comprises predicting the remaining rope life based on the varying rope stiffness.

[0028] In a preferred embodiment the method comprises indicating a need to replace the rope or the rope on one of said independent wheels based on a reduced rope stiffness.

[0029] In a preferred embodiment the method comprises indicating a restricted rope condition based on a reduced rope stiffness, preferably compared to the rope stiffness during a use phase of the rope, more preferably when the rope stiffness has decreased by 10% compared to the use phase.

[0030] In a preferred embodiment the hoist comprises means for counting rope bends, such as a bend counter, the method comprising indicating rope degradation when the rope stiffness relative to rope bends decreases, preferably when the slope of the rope stiffness curve is negative for 50 000 rope bends.

[0031] In a preferred embodiment the method comprises performing said first measurement and said second measurement and calculation to obtain the rope stiffness regularly, preferably once a week.

[0032] In a preferred embodiment, the method comprises performing parking of the car by closing a parking brake of the car.

[0033] In a preferred embodiment, the method comprises performing parking of the car by deactivating a safety device in the car.

[0034] In a preferred embodiment, the method comprises rotating the traction sheave is performed by opening a machine brake.

[0035] In a preferred embodiment, the first location in the shaft is a landing.

[0036] In a preferred embodiment, the second location in the shaft is a landing different from the first location.

[0037] In a preferred embodiment, the second position in the shaft is vertically different from the first position.

[0038] In a preferred embodiment, the first location in the shaft is the top landing.

[0039] In a preferred embodiment, the first location in the shaft is the bottom landing.

[0040] In a preferred embodiment, the first measurement is performed when the car is parked at the bottom landing and the second measurement is performed when the car is parked at the top landing, or respectively, the first measurement is performed when the car is parked at the top landing and the second measurement is performed when the car is parked at the bottom landing.

[0041] In a preferred embodiment, the method comprises at least one further measuring step:

[0042] parking the car to another position in the shaft, in which the total rope force on the car side is selected to be different from the total rope force on the counterweight side, and locking the car vertically fixedly in position relative to the shaft;

[0043] enabling the traction sheave or one of said single wheels to rotate in the direction of greater rope force;

[0044] recording a further rotational angle difference of the traction sheave or said one independent sheave;

[0045] The rope stiffness is calculated based on measurements at different vertical positions.

[0046] In a preferred embodiment, the further location in the shaft is a landing.

[0047] In a preferred embodiment, the method comprises performing a series of measuring steps over the entire travel height of the car, for example in steps of 5 m.

[0048] In a preferred embodiment, the method comprises recording the first rotation angle difference and the second rotation angle difference by means of an elevator sensor, such as a car encoder or a motor encoder.

[0049] In a preferred embodiment, the method includes recording the car position by an elevator sensor, such as a car encoder or a motor encoder or a unique magnet at each landing or a unique RFID tag at each landing.

[0050] In a preferred embodiment, the method comprises obtaining the rope stiffness EA from the equation:

[0051] in

[0052] C1 is the combined elasticity of the springs in the lift system (rope fixing spring, motor fixing, platform spring)

[0053] C2 is the elasticity of the rope

[0054] R is the radius of the traction sheave

[0055] ΔF is the change in total suspension rope force on the car side after the machine brake is opened

[0056] r is the winding ratio, and

[0057] where n sr is the number of suspension ropes.

[0058] The device for monitoring the condition of a suspension rope of an elevator according to the invention is defined in independent claim 15, comprising

[0059] An elevator comprising a car; a hoisting machine having a motor, a traction sheave and a machine brake; one or more slings; and a counterweight;

[0060] the car and the counterweight being suspended by said one or more ropes, which are guided over a single traction sheave or a set of rotatable independent wheels comprised by the traction sheave, for moving the car vertically in the elevator shaft;

[0061] The device also includes means for

[0062] a) performing a first measurement step and a second measurement step in succession, wherein in the first measurement step:

[0063] The car is parked in a first position in the shaft in which the total rope force on the car side is selected to be different from the total rope force on the counterweight side and the car is locked vertically fixedly in position relative to the shaft;

[0064] Enables the traction sheave or single wheel to rotate in the direction of greater rope force;

[0065] recording a first rotational angle difference of the traction sheave or one of said independent wheels; and

[0066] In the second measurement step:

[0067] the car is parked in a second position in the shaft in which the total rope force on the car side is selected to be different from the total rope force on the counterweight side and the car is locked vertically fixedly in position relative to the shaft;

[0068] enabling the traction sheave or said one independent wheel to rotate in the direction of greater rope force;

[0069] recording a second rotational angle difference of the traction sheave or the one independent wheel; and

[0070] b) calculating the rope stiffness based on at least said first measurement and said second measurement at at least two different vertical positions;

[0071] c) Indication of rope condition based on changing rope stiffness.

[0072] Preferred further details of the device are presented below, which further details can be combined with the device defined in independent claim 15 alone or in any combination.

[0073] In a preferred embodiment, the device comprises means for indicating the need to replace the rope or the rope on one of said independent wheels based on a reduction in rope stiffness.

[0074] In a preferred embodiment the device comprises means for indicating a restricted rope condition based on reduced rope stiffness.

[0075] In a preferred embodiment the hoist comprises means for counting rope bends, such as a bend counter, and for indicating rope degradation when the rope stiffness relative to the rope bends decreases.

[0076] In a preferred embodiment, the elevator comprises a parking brake in the car for locking the car in a vertically fixed position.

[0077] In a preferred embodiment, the elevator comprises a safety device in the car for locking the car in a vertically fixed position.

[0078] In a preferred embodiment, the first location in the shaft is a landing.

[0079] In a preferred embodiment, the second position in the shaft is vertically different from the first position.

[0080] In a preferred embodiment, the device comprises an elevator sensor, such as a car encoder or a motor encoder, for registering the first rotation angle difference and the second rotation angle difference.

[0081] In a preferred embodiment, the device includes an elevator sensor for recording the position of the car, such as a car encoder or a motor encoder or a unique magnet at each landing or a unique RFID tag at each landing.

[0082] In a preferred embodiment, the rope is configured to remain in position relative to the traction sheave during the measuring step.

[0083] The described method and device provide simple and reliable rope condition monitoring.

[0084] It has been found that the increase in the number of wire breaks is a measure of the rope condition and remaining life.

[0085] It has been found that the failure mode depends on the rope type and may also be elevator specific. Each rope has a discharge standard, which can be related to the number of wire breaks or the residual strength of the rope. For example, according to ASME A17.1-2010, Safety Code for Elevators and Escalators, the residual strength of the rope must not be less than 60% of the rated minimum breaking load.

[0086] The present invention provides rope condition monitoring which can predict remaining life and optionally signal when rope replacement is required. BRIEF DESCRIPTION OF THE DRAWINGS

[0087] The present invention will be described in more detail below by means of preferred embodiments with reference to the accompanying drawings, in which:

[0088] Figure 1 shows a side view of the lift,

[0089] Figure 2 A first arrangement for monitoring the condition of the suspension ropes of an elevator using a 1:1 rope ratio is shown.

[0090] Figure 3 A first device is shown with the parking brake or safety equipment engaged,

[0091] Figure 4 A first arrangement is shown with a vertically fixed car and an open machine brake,

[0092] Figure 5 A second apparatus for monitoring the condition of the suspension ropes of an elevator using a 2:1 rope ratio is shown.

[0093] Figure 6 A second device is shown with the parking brake or safety gear engaged,

[0094] Figure 7 A second arrangement is shown with a vertically fixed car and an open machine brake,

[0095] Figure 8 shows rope stiffness as a function of bending; and

[0096] Fig. 9 The derivative of the rope stiffness with respect to bending is shown as a function of bending. DETAILED DESCRIPTION

[0097] In the present drawings, the lift and the device are not shown to scale, but these drawings are schematic, illustrating the basic structure and operation of the preferred embodiment. In this case, the components indicated by the reference numerals in the drawings correspond to the components indicated by the reference numerals in this specification.

[0098] Figure 1 An arrangement is shown comprising an elevator with a car 2, a shaft 1, a hoisting machine 3, suspension ropes 4 and a counterweight 5. A separate or integrated car frame 6, also called slings, may surround the car.

[0099] A hoisting machine 3 may be positioned in the shaft 1. The hoisting machine may include a drive 31, an electric motor 32, a traction sheave 33 and a machine brake 34. The hoisting machine may move the car up and down in the shaft. The machine brake 34 may stop the rotation of the traction sheave 33, thereby stopping the movement of the elevator car 2.

[0100] exist Figures 2 to 4 In the embodiment, the car frame 6 is connected to the counterweight 5 by ropes 4 via the traction sheave 33, the first diverting pulley 21 and the second diverting pulley 22.

[0101] exist Figures 5 to 7 In the embodiment, the car frame 6 is connected to the counterweight 5 by ropes 4 via the traction sheave 33 and the counterweight pulley 23. The ropes 4 support the car 2 via the car pulley 24. The car pulley can be attached to the pulley beam 25, which is attached to the car 2.

[0102] The car and the counterweight are suspended by one or more ropes 4 guided over a single traction sheave 33 or a set of rotatable independent wheels comprised by the traction sheave for moving the car 2 vertically in the shaft 1 .

[0103] The car frame 6 is further supported with guide members 7 at guide rails 8 extending in the vertical direction in the shaft. The guide rails may be attached to a side wall structure 10 in the shaft with fastening brackets 9. The guide members 7 ensure vertical movement of the car 2 when the car moves up and down in the shaft 1. The counterweight 5 may be supported in a corresponding manner on guide rails attached to the wall structure of the shaft.

[0104] The safety gear 11 may be connected to the car frame 6 and to an overspeed governor rope extending vertically in the shaft 1. An automatic safety gear trigger may be attached to the car 2. The automatic safety gear trigger automatically engages the safety gear 11 in the event of a hoisting rope failure, or manually engages the safety gear 11 when it is necessary to fix the car in position relative to the shaft 1. The safety gear 11 mechanically engages the guide rail 8 when in use.

[0105] In some embodiments, a parking brake 12 (car brake 12) is attached to the car 2. The car brake 12 can be used to lock the car for the following reasons: the car brake 12 can be designed for a much higher number of cycles than the safety gear 11; the safety gear is a safety device used in an emergency; with the car brake 12, measurements can be made with an unloaded car 2 because the car brake 12 holds the load in both directions; generally, the safety gear 11 should be used for the entire car unless the safety gear 11 is bidirectional; and the car brake 12 can be electronically activated.

[0106] The automatic safety gear trigger has electrical contacts which are part of the elevator safety chain and are mechanically linked to the car safety gear through the overspeed governor rope.

[0107] The rope condition monitoring method comprises:

[0108] a) performing a first measurement step and a second measurement step in succession, wherein in the first measurement step:

[0109] parking the car 2 in the shaft 1 to a first position L1 (rope length L1 when the car is in the first position) in which the total rope force on the car side L1 is chosen to be different from the total rope force on the counterweight side T2 (the car 2 load must be different from the elevator balance load so that T1≠T2) and locking the car vertically fixed in position relative to the shaft;

[0110] enabling the traction sheave 33 or one of the independent sheaves to rotate in the direction of the larger rope force T1, T2, wherein the traction sheave can rotate in the direction of the larger rope force due to the imbalance and elasticity of the system;

[0111] Record the first rotation angle difference of the traction sheave 33 or the one independent wheel as well as

[0112] Afterwards, in a second measuring step, the measurement is repeated at another location:

[0113] parking the car 2 in the shaft 1 to a second position L2 (when the car is in the second position, the rope length is L2), in which the total rope force on the car side L1 is selected to be different from the total rope force on the counterweight side T2, and the car is locked in position vertically fixed relative to the shaft;

[0114] Enable the traction sheave 33 or the one independent wheel to rotate to the direction of the larger rope force T1, T2;

[0115] Record the second rotation angle difference of the traction sheave 33 or the one independent wheel as well as

[0116] b) calculating the rope stiffness EA based on at least said first measurement and said second measurement at at least two different vertical positions L1, L2, Ln;

[0117] c) Indication of rope condition based on the changing rope stiffness EA.

[0118] To improve measurement accuracy, preferably T1 and T2 are significantly different. For example, the car can be empty or loaded with nominal load.

[0119] The rope stiffness EA (E-modulus × area) can be obtained by the following equation:

[0120] in

[0121] C1 is the combined elasticity of the springs in the lift system (rope fixing spring, motor fixing, platform spring)

[0122] C2 is the elasticity of the rope

[0123] R is the radius of the traction sheave

[0124] ΔF is the change in total suspension rope force on the car side after opening the machine brake or safety device

[0125] r is the winding ratio, and

[0126] (2) where n sr is the number of suspension ropes.

[0127] Regardless of whether the device holding the car in place (parking brake 12 or safety equipment 11) is fixed to the car 2 or to the rope 6, the rope stiffness can be calculated from equations (1) and (2).

[0128] In an embodiment, the method comprises predicting a remaining rope life based on a varying rope stiffness.

[0129] Figure 8 The graph shows the change in rope stiffness during its service life.

[0130] Fig. 9 The slope of the stiffness curve during the life of the rope is shown.

[0131] The rope stiffness changes during its service life as the rope bends around the pulley. It can be roughly divided into three stages: A: the running-in stage, during which the wires are fixed tighter to each other and the rope stiffness increases rapidly; B: the use stage, during which the stiffness remains almost unchanged; C: the deterioration stage, during which the stiffness decreases due to wire breakage.

[0132] Based on the graph, the remaining life of the rope can be predicted. In particular, one or more alarm limits AL1, AL2, AL3 indicating the need to replace the rope can be defined based on the graph. The characteristics of the rope degradation stage C are firstly: the stiffness is reduced compared to the use stage (see Figure 8 ), followed by the negative slope of the stiffness curve (see Fig. 9 ).

[0133] In an embodiment the method comprises indicating a restricted rope condition based on a reduced rope stiffness, preferably compared to the rope stiffness during a use phase of the rope, more preferably when the rope stiffness has decreased by 10% compared to the use phase.

[0134] In order to identify rope degradation, the stiffness measurement described can be performed regularly and frequently. The measurement can be performed, for example, once a week at night when the lift is not in use. The measurement data is preferably saved in a log for further analysis.

[0135] In an embodiment, the method comprises performing said first measurement and said second measurement and calculation regularly, preferably once a week, to obtain the rope stiffness.

[0136] In order to calculate the slope of the stiffness curve as a function of bending, the lift may have a bending counter.

[0137] In an embodiment the hoist comprises means for counting rope bends, such as a bend counter, and the method comprises indicating rope degradation when rope stiffness decreases with respect to rope bends, preferably when the slope of the rope stiffness curve is negative for 50 000 rope bends.

[0138] In an embodiment, the method comprises indicating a need to replace the rope 4 or the rope on one of said independent wheels based on a reduced rope stiffness.

[0139] In an embodiment, the elevator comprises a parking brake 12 in the car for locking the car in a vertically fixed position.

[0140] In the exemplary embodiment, the car 2 is parked by closing the parking brake 12 of the car 2 .

[0141] In an embodiment, the elevator comprises a safety device 11 in the car 2 for locking the car so that it is vertically fixed.

[0142] In the embodiment, the car 2 is parked by closing the safety equipment 11 in the car.

[0143] Bidirectional safety equipment is able to hold the car in both directions, so the car load can be greater or less than the elevator balance load. For ordinary safety equipment, the car load must be greater than the elevator balance load. Safety equipment has a gap, which affects the traction sheave rotation angle when the machine brake is opened. However, when measuring in two or more vertical positions (such as the landing position), the effect of the gap is eliminated from the result.

[0144] In an embodiment, the method comprises that rotating the traction sheave 33 is performed by opening the machine brake 34 .

[0145] In the exemplary embodiment, the first location L1 in the shaft 1 is a landing.

[0146] To improve measurement accuracy, L1 and L2 are preferably very different. For example, measurements can be made on the bottom layer and the top layer. Measurements can also be made on more than two layers to improve accuracy and reliability.

[0147] In the exemplary embodiment, the second location L2 in the shaft 1 is a landing different from the landing in the first location L1 .

[0148] In an embodiment, the second position L2 in the shaft 1 is different from the first position L1 in the vertical direction.

[0149] In an embodiment, the first location L1 in the shaft 1 is the top landing.

[0150] In the embodiment, the first location L1 in the shaft 1 is the bottom landing.

[0151] In an embodiment, the first measurement is performed when the car is parked at the bottom landing and the second measurement is performed when the car is parked at the top landing, or respectively, the first measurement is performed when the car is parked at the top landing and the second measurement is performed when the car is parked at the bottom landing.

[0152] In an embodiment, the method comprises at least one further measuring step:

[0153] parking the car 2 to a further position Ln in the shaft 1 (rope length Ln when the car is in this further position) in which the total rope force on the car side L1 is selected to be different from the total rope force on the counterweight side T2 and the car is locked vertically fixedly in position relative to the shaft;

[0154] Enable the traction sheave 33 or one of the independent wheels to rotate to the direction of the larger rope force T1, T2;

[0155] Record the additional rotation angle difference of the traction sheave 33 or the one independent wheel

[0156] The rope stiffness EA is calculated based on the measurements at different vertical positions.

[0157] In the exemplary embodiment, the further location Ln in the shaft 1 is a landing.

[0158] By performing the measurements step by step over the entire travel height, it is possible to obtain the rope stiffness as a function of length. In an embodiment, the method comprises performing a series of measurement steps over the entire travel height of the car, for example in steps of 5 m. In this way, even short damaged sections of a long rope can be identified which would otherwise be hidden. The resolution of this type of measurement depends on the measurement interval.

[0159] In an embodiment, the hoist comprises means for counting rope bends, such as a bend counter, and for indicating rope degradation when the rope stiffness decreases relative to the rope bends.

[0160] The method can be based on the real, measured elasticity of the elevator in question. If the absolute value of the rope stiffness is to be calculated, the following prerequisites are required: the car mass M car and the counterweight mass M CWT, or rated load Q and balance percentage p; traction sheave radius R; winding ratio r; number of suspension ropes n sr .

[0161] If only the relative change in rope stiffness is to be calculated, no prerequisites are required.

[0162] Rope lengths L1 and L2 and traction sheave angle and It can be measured with existing sensors (eg car encoder and motor encoder) and read from the elevator control system.

[0163] In an embodiment, the method includes recording the first rotation angle difference and the second rotation angle difference by an elevator sensor such as a car encoder or a motor encoder.

[0164] In an embodiment, the method comprises recording the car positions L1, L2, ..., Ln by means of elevator sensors such as a car encoder or a motor encoder or a unique magnet per landing or a unique RFID tag per landing.

[0165] In an embodiment, the rope is configured to remain in position relative to the traction sheave during the measuring step.When the machine brake 34 is open, the rope will not slip because the T1 / T2 ratio is close to 1.

[0166] The traction sheave radius R may change during the life of the elevator due to wear. However, such changes are usually only a few thousandths and do not significantly affect the method. In some embodiments, coated ropes are used as suspension ropes. During the life of the elevator, the coating of the coated rope may change due to wear. However, such changes are usually small and do not significantly affect the method.

[0167] The parking brake 12 is typically designed to hold the full rated load Q. Since the imbalance between the car and the counterweight is always less than the rated load (eg 50% of Q), the parking brake should easily hold the imbalance used in this method.

[0168] In the described method, rope mass, moving cable mass, guide friction and pulley bearing friction are neglected.

[0169] The constant C1 is the overall elasticity of the springs in the elevator system. Changes in this constant can be used as an indicator of the condition of the springs.

[0170] This method can be used to measure the average stiffness of all suspension ropes.

[0171] If there is a separate bearing mounted traction sheave 33 for each suspension rope in the case of a suspension ratio of 1:1 and if there is a separate bearing mounted diverting pulley for each suspension rope in the case of a suspension ratio of 2:1, the stiffness of the separate suspension ropes 4 can be measured.

[0172] This can be achieved by rotating one wheel of the multi-wheel traction sheave at a time and measuring the rotation angle, i.e. the travel length of the rope in question. Respectively, measuring the change in the force of the rope with a force sensor gives the force and displacement of the rope and allows the stiffness of the rope to be calculated. The change in the force of the rope can be measured using a compensation device for equalizing and / or compensating the rope tension, which includes a force sensor at the car side. Each respective wheel can be rotated by a motor, or the respective wheels can be coupled to rotate freely.

[0173] This allows the ropes to be checked individually, giving a better solution.The car 2 does not even need to be locked in place with the parking brake 12, since it will not move anyway if only one wheel is rotated at a time.

[0174] The use of the invention is not limited to the elevator disclosed in the accompanying drawings. The invention can be used for any type of elevator, for example an elevator with or without a machine room, with or without a counterweight. The counterweight can be located on either or both side walls or the rear wall of the elevator shaft. The drive, motor, traction sheave and machine brake can be located somewhere in the machine room or in the elevator shaft. The elevator car guide rails can be positioned on opposite side walls of the shaft or on the rear wall of the shaft.

[0175] It is obvious to a person skilled in the art that, as technology advances, the inventive concept can be implemented in various ways.The invention and its embodiments are not limited to the examples described above but may vary within the scope of the claims.

Claims

1. A method for monitoring the condition of a suspension rope (4) of an elevator, the elevator comprising: A car (2); a hoisting machine (3) having a motor (32), a traction sheave (33) and a machine brake (34); one or more suspension ropes (4); and a counterweight (5); The car and the counterweight are suspended by the one or more ropes (4), which are guided over a single traction sheave (33) or a set of rotatable independent wheels comprised by the traction sheave for vertically moving the car (2) in the elevator shaft (1); The method comprises a) performing a first measurement step and a second measurement step in succession, wherein in the first measurement step: parking the car (2) in a first position (L1) in the shaft (1) in which the total rope force (T1) on the car side is selected to be different from the total rope force (T2) on the counterweight side and locking the car vertically fixedly in position relative to the shaft; enabling the traction sheave (33) or one of the independent wheels to rotate to a direction with a larger rope force (T1, T2); Recording a first rotation angle difference (Δφ1) of the traction sheave (33) or the one independent wheel; and In the second measurement step: parking the car (2) to a second position (L2) in the shaft (1) in which the total rope force (T1) on the car side is selected to be different from the total rope force (T2) on the counterweight side and the car is locked vertically fixedly in position relative to the shaft; enabling the traction sheave (33) or the one independent sheave to rotate to the direction of a larger rope force (T1, T2); Recording a second rotation angle difference (Δφ2) of the traction sheave (33) or the one independent wheel; as well as b) calculating the rope stiffness (EA) based on at least said first measurement and said second measurement at at least two different vertical positions (L1, L2, Ln); c) Indication of rope condition based on changing rope stiffness (EA).

2. The method according to claim 1, comprising predicting the remaining rope life based on the varying rope stiffness (EA).

3. The method according to claim 1 or 2, comprising indicating a need to replace the rope (4) or the rope on one of the independent wheels based on a reduced rope stiffness (EA).

4. Method according to any of claims 1 to 3, comprising indicating a restricted rope condition based on a reduced rope stiffness (EA), preferably compared to the rope stiffness during a use phase of the rope, more preferably when the rope stiffness has decreased by 10% compared to the use phase.

5. Method according to any of claims 1 to 4, wherein the hoist comprises means for counting rope bends, such as a bend counter, the method comprising indicating rope degradation when rope stiffness decreases with respect to rope bends, preferably when the slope of the rope stiffness curve is negative for 50 000 rope bends.

6. Method according to any one of claims 1 to 5, comprising performing the first measurement and the second measurement and calculation to obtain the rope stiffness (EA) regularly, preferably once a week.

7. Method according to any one of claims 1 to 6, comprising performing parking of the car (2) by closing a parking brake (12) of the car.

8. Method according to any one of claims 1 to 7, comprising performing the parking of the car (2) by deactivating a safety device (11) in the car.

9. Method according to any one of claims 1 to 8, comprising performing enabling the rotation of the traction sheave (33) by opening the machine brake (34).

10. The method according to any one of claims 1 to 9, wherein the first location (L1) in the shaft (1) is a landing.

11. The method according to claim 10, wherein the second location (L2) in the shaft (1) is a landing different from the landing in the first location (L1).

12. Method according to any one of claims 1 to 11, wherein the second position (L2) in the shaft (1) is different from the first position (L1) in the vertical direction.

13. The method according to any one of claims 1 to 12, comprising at least one further measuring step: parking the car (2) to a further position (Ln) in the shaft (1) in which the total rope force (T1) on the car side is selected to be different from the total rope force (T2) on the counterweight side and locking the car vertically fixedly in position relative to the shaft; enabling the traction sheave (33) or one of the independent sheaves to rotate to the direction of a larger rope force (T1, T2); Recording a further rotational angle difference (Δφn) of the traction sheave (33) or of the one independent sheave; The rope stiffness (EA) is calculated based on measurements at different vertical positions.

14. The method according to any one of claims 1 to 13 comprises recording the car position (L1, L2, ..., Ln) by means of an elevator sensor, such as a car encoder or a motor encoder or a unique magnet for each landing or a unique RFID tag for each landing.

15. A device (100) for monitoring the condition of a suspension rope (4) of an elevator, the device comprising An elevator comprising a car (2); a hoisting machine (3) having a motor (32), a traction sheave (33) and a machine brake (34); one or more suspension ropes (4); and a counterweight (5); The car and the counterweight are suspended by the one or more ropes (4), which are guided over a single traction sheave (33) or a set of rotatable independent wheels comprised by the traction sheave for vertically moving the car (2) in the elevator shaft (1); The device also includes means for a) performing a first measurement step and a second measurement step in succession, wherein in the first measurement step: The car (2) is parked in a first position (L1) in the shaft (1) in which the total rope force (T1) on the car side is selected to be different from the total rope force (T2) on the counterweight side and the car is locked vertically fixedly in position relative to the shaft; enabling the traction sheave (33) or the single wheel to rotate in the direction of greater rope force (T1, T2); Recording a first rotation angle difference (Δφ1) of the traction sheave (33) or one of the independent wheels; and In the second measurement step: The car (2) is parked in a second position (L2) in the shaft (1) in which the total rope force (T1) on the car side is selected to be different from the total rope force (T2) on the counterweight side and the car is locked vertically fixedly in position relative to the shaft; enabling the traction sheave (33) or the one independent sheave to rotate to the direction of a larger rope force (T1, T2); Recording a second rotation angle difference (Δφ2) of the traction sheave (33) or the one independent wheel; as well as b) calculating said rope stiffness (EA) based on at least said first measurement and said second measurement at at least two different vertical positions (L1, L2, Ln); c) Indication of rope condition based on changing rope stiffness (EA).

16. Device according to claim 15, comprising means for indicating the need to replace the rope (4) or the rope on one of the independent wheels based on a reduced rope stiffness (EA).

17. Device according to claim 15 or 16, comprising means for indicating a restricted rope condition based on reduced rope stiffness (EA).

18. An arrangement according to any one of claims 15 to 17, wherein the hoist comprises means for counting rope bends, such as a bend counter, and means for indicating rope degradation when rope stiffness decreases relative to rope bends.

19. Apparatus according to any one of claims 15 to 18, wherein the lift comprises a parking brake (12) in the car for locking the car in a vertically fixed position.

20. An arrangement according to any one of claims 15 to 19, wherein the lift comprises a safety device (11) in the car for locking the car in a vertically fixed position.

21. The device according to any one of claims 15 to 20, wherein the first location (L1) in the shaft (1) is a landing.

22. The device according to any one of claims 15 to 21, wherein the second position (L2) in the shaft (1) is different from the first position (L1) in the vertical direction.

23. The device according to any one of claims 15 to 22, comprising an elevator sensor, such as a car encoder or a motor encoder, for recording the first rotation angle difference and the second rotation angle difference (Δφ1, Δφ2, ..., Δφn).

24. The device according to any one of claims 15 to 23 comprises an elevator sensor for recording the car position (L1, L2, ..., Ln), such as a car encoder or a motor encoder or a unique magnet for each landing or a unique RFID tag for each landing.

25. The device according to any one of claims 15 to 24, wherein the rope is configured to remain in position relative to the traction wheel during the measuring step.

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