FI89107B - Method and arrangement for monitoring the condition of a lifting cable - Google Patents

Description

39107

METHOD AND APPARATUS FOR MONITORING THE CONDITION OF LIFTING ROPES

By dividing the separated application no. 904,344.

The present invention relates to a method and an apparatus for monitoring the condition of a hoisting rope according to the preamble of claim 1.

10 The most important wearing part of an elevator and crane is a hoisting rope. Monitoring its condition is one of the most common tasks of a maintenance man. In some countries, monitoring the condition of the hoisting rope is linked to mandatory lift inspections, while in others it is the sole responsibility of the lift maintenance company.

15

Monitoring the condition of a hoisting rope is usually based on a visual calculation of wire breaks, which is slow and involves uncertainties, such as variations in the skill and care of the maintenance man. In addition, breaks in the wire inside the hoisting rope due to, for example, a manufacturing defect 20 cannot then be detected.

DE 3839481 discloses a method for measuring, for example, variations in the cross-sectional area of metal ropes, in which changes in the axial magnetic flux of an axially magnetized rope are measured. Changes in axial magnetic flux are determined by measuring changes in radial magnetic flux to or from the rope. Flow changes are measured using two saddle windings placed on 30 opposite sides of the object to be measured. The target is magnetized in axially opposite directions in adjacent portions. The windings cover at least one area where the change in magnetic flux varies from zero to maximum.

Accordingly, DE 3839469 discloses a method for determining, for example, changes in the cross-sectional area of steel ropes, in which successive portions of the rope are magnetized in axially opposite directions and in which radial flux changes are detected by interconnected non-inductive means, such as Hall-elemen-5 roads.

The object of the present invention is to obviate the drawbacks of the prior art. According to the claims below, the condition of the hoisting rope is monitored by measuring the area of the rope 0 by measuring its reluctance, i.e. the magnetic conductivity of the whole rope. In this case, wire breaks are observed as sudden changes in reluctance, while rope wear causes a reduced reluctance to the center of the rope compared to the end of the rope that does not pass over the traction sheave.

5

By means of the invention, breaks in the hoisting rope can be calculated automatically and, in addition, the wear of the rope can be estimated on the basis of variations in its surface area.

The invention can be used either as an aid to a maintenance man or as a fixed safety device that gives an alarm when the ropes need to be replaced.

The invention has the following advantages: 5 - the monitoring of the condition of the hoisting ropes is speeded up, as the whole rope can be checked in one go at normal speed - the reliability of monitoring is substantially improved, as the device always works in the same way regardless of the service person; in addition to breaks, information can also be obtained on the difference in surface area between different parts of the rope - information on the need to replace ropes can be obtained early enough to order new ropes so that delivery time is not a problem - ropes can be used up when the rope is known

II

3 89107 condition and its change exactly.

In the following, the invention will be described in more detail by means of examples with reference to the accompanying drawings, in which

Figure 1 shows an apparatus according to the invention.

Figure 2 shows another apparatus according to the invention.

10

The invention comprises a sensor placed next to or on both sides of the hoisting rope and a signal processing device. It is advisable to place the sensor in an elevator near the traction sheave or in another place where the rope cannot swing.

15

In the solution according to the invention shown in Figure 1, a U-shaped iron core made of a thin plate with prongs l1, 12 through the ends of which the rope 1 passes, and a body 13 with windings 14 is arranged in the length-20 direction with respect to the rope. A constant current I is applied to the winding from the alternator. When the reluctance of the magnetic circuit changes, it causes a change in the flux, whereby the voltage UI measured by the measuring element 15 across the coil changes. As the break passes one end 11 or 12 of the heart, a voltage, 25, is displayed in the voltage Ui as well as at the other end. If an autocorrelation is calculated from this signal (in unit 16, where an A / D conversion is also performed), a function is obtained with a peak at a time proportional to the time difference T between the two pulses. Here the time difference T is 30 T = S / V (1) where s is the distance and v is the rope speed.

35 The autocorrelation function is further multiplied by the window function 11a in the unit 17, the emission range of which is adjustable, and is adjusted 4 89107 so as to pass through the peak just at time T. To do this, you need to know the speed of the rope. It can be measured, for example, by a friction cometer 18 installed in the same measuring device.

Yet another way of processing the signals 0 according to the previous figure is shown in Fig. 2. Here the speed measurement is performed by a pulse tachometer 18, the pulse number of which is chosen so that an equal number of pulses are always obtained on the path s, here 5. The voltage UI obtained from the previous circuit In the / O converter 20 using 5 tachometer pulses as a clock signal. The signal is applied to a level-sensitive comparator 21 with an output of 1 if the signal level exceeds the set value. In this case, one must think of looking for the first of the two pulses caused by the wire break. The output of the comparator now sets 0 to a shift register 22, the output of which in turn is multiplied by the converted voltage UI. If it was now a wire break, a new pulse is obtained in the fifth period, which passes through the multiplier 23, because the one caused by the first pulse had reached its end in the shift register. 2 5 The solutions according to Figures 1 and 2 can be used to improve the sensitivity of the system. They are particularly suitable for use in separate measuring devices.

It will be apparent to those skilled in the art that the various embodiments of the invention are not limited to the examples set forth above, but may vary within the scope of the claims set forth below.

Il.

Claims (9)

A method for checking the condition of the carrier line of a lifting device, which method comprises a magnetic flow directed along or across the line (1) and one or more adjacent the line or on different sides of the placed iron core (11 ... 13) forming a magnetic circuit, measuring the cross-sectional area of the rope by means of the change in the reluctance of the rope as a function of the cross-sectional area, which measured cross-sectional area 10 is used to assess the condition of the rope, characterized in that the iron core is provided with a winding (14) constant current flows and over which the voltage is measured and at which the speed of movement of the line is measured. 15 Method according to Claim 1, characterized in that the autocorrelation function of the voltage acting over the winding is determined and multiplied by a window function. 20 Method according to claim 2, characterized in that the window function of the window function is adjustable and that the window function is specially regulated for tree breakage identification so that it passes through the signal nail that occurs at the time difference (T) which arises when the tree break in the line passes by. core bed ends. Method according to claim 1, characterized in that the speed is measured with a pulse tachometer (18) or the like, whose pulses are used as clock pulses when the measured analog voltage is converted into digital form, which digital signal is fed to a comparator (21). where it is compared with the setpoint, which comparison is used for checking the condition of the line. I: 9 89107 5. A method according to claim 4, characterized in that, in particular for determining tree breakage, the comparator's output is fed to a shift register (22) or the like, the output of which is multiplied by the dull digital voltage signal. Apparatus for controlling the condition of the carrier (1) to a lifting device by measuring the magnetic properties of the carrier (1), which device comprises an iron core (11 ... 13) located adjacent to the carrier in the manner of the carrier (1). ) together with the iron core forms a longitudinal or transverse magnetic circuit, the device further comprising a sensor (14) which responds to the change in the reluctance of the magnetic circuit and an indicator (14,15) indicating this change, whereby the change in the reluctance can be determined. on the basis of the changes in the cross-sectional area of the line (1), characterized in that the sensor is a winding located on the iron core, wherein a constant voltage generator (14) is coupled to the winding and an output to the winding output coupled voltage sensing sensor (15) which measures the voltage variations in the winding poles and that the device comprises a means (18) which measures the line speed. Device according to claim 6, characterized in that it comprises a means (16) which forms the autocorrelation function of the voltage across the winding, a means (17) which forms a window function whose pass area is controlled as a function of speed and a multiplier which multiplies the outputs. from the means forming the autocorrelation function and the window function. Device according to claim 6, characterized in that the speed measuring means is a pulse tachometer or the like and the device comprises an A / D converter 35 (20) for converting the measured voltage into digital form, in which transducers the pulses from a pulse tachometer or the like are used as clock signals, and a comparator (21) in which the digital signal is compared with the setpoint and whose output signal is used for checking the condition of the line. 5 Device according to claim 8, characterized in that the device, in particular for determining tree breakage, is provided with a shift register (22) to which the comparator output is guided, and a multiplier (23) which multiplies the digital output voltage with the output of the shift register. li