| DE3139415A1 | 1983-04-21 |
| 1. | A means of detecting, measuring and/or controlling tensions of strands in rope laying machines and wires in stranding machines, characterized in that the means is a forcetoelectrical signal transducer adapted to be mounted at each strand or wire direction change fairlead, preferably fairleads prior to strand or wire entry into a preformer head at the closer, a signal transmission means for transmission of the signals to a receiving means and signals processing means. |
| 2. | A means of detecting, measuring and/or controlling tensions of strands in rope laying machines and wires in stranding machines as claimed in claim 1, characterized in that the transducers at each fairlead are those employing magnetoelastic effect. |
| 3. | A means of detecting, measuring and/or controlling tensions of strands in rope laying machines and wires in stranding machines as claimed in either one of claims 1 or 2, characterized in that a radio or other wireless transmitter is used as the signals transmission means. |
| 4. | A means of detecting, measuring and/or controlling tensions of strands in rope laying machines and wires in stranding machines as claimed in any one of claims 1 to 3, characterized in that the angle of deflection of the strands or wires at the fairleads, from directions leading from the reels to a direction directed to the closer lies between 10 degrees and 20 degrees. |
| 5. | A means of detecting, measuring and/or controlling tensions of strands in rope laying machines and wires in stranding machines as claimed in any one of claims 1 to 4, characterized in that noise induced in the signal by the friction effects of the strands or wires passing over the transducer, gravity acting on the mass of the strands or wires, centripetal force acting on the strands or wires, and/or vibration both in the machine parts and the strands or wires themselves, is processed by signal processing software and hardware to enhance useful signals or signals bearing determinable relationships to useful signals. |
| 6. | A means of detecting, measuring and/or controlling tensions of strands in rope laying machines and wires in stranding machines as claimed in claim 5, characterized in that signaltonoise enhancement algorithms are implemented in the signal processing means which include the techniques of detecting periodicity of force variation and statistical probability of random scatter of the force. |
| 7. | A means of detecting, measuring and/or controlling tensions of strands in rope laying machines and wires in stranding machines as claimed in any one of claims 1 to 6, characterized in that the useful signals are displayed continuously to the operator of the machine as an aid to him to enhance his existing technique of carrying out the tensions control function. |
| 8. | A means of detecting, measuring and/or controlling tensions of strands in rope laying machines and wires in stranding machines as claimed in any one of claims 5 to 7, characterized in that the processing to provide useful signals is extended to provide feedback to a control means for automated control of the tensions of strands on a continuous operating basis. |
| 9. | A means of detecting, measuring and/or controlling tensions of strands in rope laying machines and wires in stranding machines, as herein generally described. |
| 10. | A means of detecting, measuring and/or controlling tensions of strands in rope laying machines and wires in stranding machines, as herein specifically described with reference to the drawings and as illustrated. |
| 11. | A rope laying machine or a wire stranding machine which is characterized by a means of detecting, measuring and/or controlling tensions of strands in the machine as claimed in any one of claims 1 to 10. AMENDED CLAIMS [received by the International Bureau on 05 June 2001 (05.06.01); original claims 111 replaced by amended claims 16 (2 pages)] 1. A means of detecting, measuring and/or controlling tensions of strands in rope laying machines and wires in stranding machines, in which the means is a forcetoelectrical signal transducer adapted to be mounted at each strand or wire direction change fairlead prior to strand or wire entry into a preformer head at the closer, a signal transmission means for transmission of the signals to a receiving means and signals processing means, characterized in that the transducers at each fairlead are those employing magnetoelastic effect and each fairlead is a bush incorporated in the transducer itself, the with the strand or wire passed through the bore of the bush and in operation sliding through the bore, and in that the signal processing means includes a CPU programmed to process each raw signal by removal of noise induced in the signal by the friction effects of the strands or wires passing over the transducer, gravity acting on the mass of the strands or wires, centripetal force acting on the strands or wires, and/or vibration both in the machine parts and the strands or wires themselves, to enhance useful signals or signals bearing determinable relationships to useful. signals. |
| 12. | 2 A means of detecting, measuring and/or controlling tensions of strands in rope laying machines and wires in stranding machines as claimed in claim 1, characterized in that the CPU carries out the processing according to protocol and algorithm designs developed in interactive mode with a particu) ar machine. |
| 13. | 3 A means of detecting, measuring and/or controlling tensions of strands in rope laying machines and wires in stranding machines as claimed in claim 2, characterized in that signaltonoise enhancement algorithms are implemented in the signa'processing means which include the techniques of detecting periodicity of force variation and statistical probability of random scatter of the force. |
| 14. | 4 A means of detecting, measuring and/or controlling tensions of strands in rope laying machines and wires in stranding machines, as herein generally described. |
| 15. | 5 A means of detecting, measuring and/or controlling tensions of strands in rope laying machines and wires in stranding machines, as herein specifically described with reference to the drawings and as illustrated. |
| 16. | 6 A rope laying machine or a wire stranding machine which is characterized by a means or detecting, measuring and/or controlling tensions of strands in the machine as claimed in any one of claims 1 to 10. STATEMENT UNDER ARTICLE 19.1 The following comments refer to the claims as now submitted to be amended under article 19. The document DE 31 39 415 A Kuster discloses a strand or wire tension measuring device, consisting of force transducer rollers 20 next to the bores in the rotating front base plate through which the strand or wire passes to the closer. According to the present inventor, the use of rollers (i. e jocky pulleys) has not succeeded in practice due to mechanical tumbersomeness, lack of durability and unreliable measurement of tensions, which it is inferred is due to effects including the variable action of gravity on the heavy rollers as the machine rotates, larger centripetal forces and larger vibrations. (page 3, lines 1 to 6). The invention claims the combining of each fairlead as a bush forming part of the transducer. Service trials over a period have proved that the arrangement is durable and has the advantage of simplicity and robustness. (page 6, lines 13 to 15). The bushes are much lighter than rollers, causing smaller force variations due to rotation, smaller centripetal forces and less prone to vibration. The use of bushes is counterintuitive because of friction of the strand or wire passing over the transducer bush would incline the skilled person to anticipate adverse effects on measurement, which is not the case. The present invention furthermore claims the use of transducers which exhibit magnetoelastic effects which are less prone to radio interference and other interferences. This is not disclosed by the document even though it does disclose the use of radio to transmit the signal from the rotating parts. The document DE 31 39 415 A discloses that the output signals are in each case compared to a set value in a comparator circuit, the difference is passed in suitable form to automatically control the braking devices. The present invention claims a CPU programmed to remove noise related to friction effects, gravity, centripetal force and vibration. In claims 2 and 3 the present invention claims a CPU carrying out a protocol and algorithm designs developed in interactive mode with a particular machine by detecting periodicity of force variation and statistical probability of random scatter. Thus the present invention is focused on improving the signal obtained from the transducer, whereafter the signal can be used as required. (page 5, lines 3 to 13). The improvement of the signal is not disclosed by the document DE 31 39 415 A, at all. It is notable that strand forming and rope laying machines are still being operated by empirical methods relying on the operator's experience (page 1, lines 16 to 25 and also noted in the document). It is respectfully submitted that the present invention as now defined by the characterizing features of the claims to be introduced by amendment under article 19, has taken the technology to a more advanced level than that disclosed in the document DE 31 39 415 A. |
BACKGROUND OF THE INVENTION Although wire ropes were first developed in the 19th century and their design was almost entirely empirical until the 1950's, since then extensive development of wire rope design has taken place and there has been substantial progress in theoretical analysis of rope designs, made possible by the computing power of modern computers. Thus the common cable lay as well as Lang's lay ropes are long established, also equal lay length and unequal lay length. Cross laid and non-spin ropes as well as compact strand ropes, triangular ropes and flat outer strand crush resistant ropes have found application in deep level mining in which development in South Africa has been pre-eminent. Plastic impregnation, sometimes combined with advanced lubrication approaches has received useful application in some fields.
Against this background of advanced development it is remarkable that strand forming and rope laying machines are still being operated in some respects by empirical methods. One of these is in respect of the tension of the strands as they are led into the closing die or mandrel in which the rope is formed. This tension derives from the tension at which the strands are paid out from the reels, the latter being provided with brakes to adjust this tension. In a typical example, the tension is set from time to time while the machine is stationary by manual testing of tension of each strand by pulling on it orthogonally to its path and experience in setting the brake straps on each reel. This relies on the operator's"feel"and knowledge of the machine from experience and hence the assessment is qualitative and subjective.
An analogous situation obtains with strand forming machines, where the tensions of the wires are adjusted by a combination of manual testing and empirical experience.
These approaches have an inherent tendency to inaccuracy and if there are significant differences between tensions of the strands, slack strands result (especially in non-spin ropes), the finished rope developing a corkscrew, wave or sunken strand phenomenon. Corkscrewing is the condition where the finished rope follows a corkscrew shape, due to one or more strands being significantly tighter than others. Some grounds exist for the suggestion by users that fatigue life of ropes is adversely affected by these conditions. These problems have not received much attention by rope makers in the past, probably due to the skill of operators and the fortunate circumstance that the rope laying machines have an inherent tendency to ameliorate the effects of tension variations. At the closing mandrel or die the closing action tends to"milk"out slackness in some of the strands, that is, the die keeps the slack ahead of it and past the die the tensions are more even.
However, in the constant striving for higher standard wire ropes, a need to better control tensions is foreseen. Efforts to achieve this improvement have not achieved practical success, and some machines are witness to installations which have been de-activated because they are ineffective in practical conditions, disturb practical operation cycles, do not give reliable results or do not remain in working order for long.
An example is a modified braking system on the reels, e. g. electromagnetic braking in feedback arrangements using load current and back electromagnetic force effects. Systems applied at the reels have an inherent shortcoming in several respects, however. It is difficult to compensate for changing effective diameter of the rope as it unreels from the reel, ruffled coils cause fluctuations in tension as trapped coils cause peaks in drag and the strands from different reels travel through different fairleads and conduits to the closer.
Another approach has been placing of jockey pulleys against the strands against spans of the strands, but these too have not succeeded in practice. This has been due to mechanical cumbersomeness and lack of durability as well as unreliable measurement of tensions, which it is inferred is due to effects including the variable action of gravity on the heavy jockey pulleys as the machine rotates, centripetal forces and vibration.
Still another approach has been a three-roller deflection system which, however, is adversely affected the tell tales used and hence the flat lay freedom between the locking rollers and the tell tales. In addition to this problem for the operators, they experience difficulties in the setting up of the system.
The problem which is faced therefore is to provide a means of measuring strand tension in a rope making machine which is effective in practical application. From the measured tension more reliable manual setting of the reel brakes can be made or feedback systems can be designed for automated adjustment and maintenance of tensions during rope making.
SUMMARY OF THE INVENTION The solution according to the present invention is to provide a means of detecting, measuring and/or controlling tension of a strand in rope laying machines and a wire in stranding machines, characterized in that the means is a force-to-electrical signal transducer to be mounted at a strand or wire direction change fairlead, preferably a fairlead prior to strand or wire entry into a pre-former head at the closer, a signal transmission means for transmission of the signal to a receiving means and signal processing means.
Usually one transducer will be provided at the fairlead for each strand or wire, e. g. in a 12 strand rope closing machine, a transducer will be provided at each of the 12 fairleads, however, there can be grounds for only some but not all fairleads to have transducers.
The transducer at each fairlead preferably is one employing a magneto-elastic effect, but piezo-electric, strain gauge and load cell and other suitable physical effects can be used in appropriate devices to provide a signal responsive to force resulting from strand tension.
The use of a radio or other wireless (e. g. ultra-sonic, infra-red, etc) transmitter conveniently enables the signal to be monitored and processed as required during rotation of the machine, thus not only while the machine is stationary. The fairlead prior to the closer is one giving a substantial angle of deflection of the strand or wire, from a direction leading from the reel to a direction directed to the closer. A suitable angle, for example, which is found existing in typical machines, is of the order of 15 degrees, say between 10 degrees and 20 degrees. The force exerted on the transducer caused only by the strand or wire tension is related by a suitable trigonometric factor to the strand or wire tension. This force or a signal bearing a simple relationship (e. g. direct proportionality) to the force is described herein as the "useful signal".
However, the total force exerted on the transducer is a complex product of not only the strand or wire tension, but also the friction effects of the strand or wire passing over the transducer (whether by sliding or rolling), causing a difference between strand or wire tension before and after the fairiead and the direction of the resultant force, gravity acting on the mass of the strand or wire which constantly varies in relative direction to the transducer as the machine rotates, centripetal force which varies according to machine rotational speed and vibration both in the machine parts and the strand or wire itself. All of these effects are recognised as contributing to noise tending to mask the useful signal.
According to a preferred embodiment of the invention, the signal processing means is adapted to distinguish the useful signal from the noise by techniques which include detecting periodicity of force variation and statistical probability of random scatter of the force and processing the signal in a manner by which the useful signal or a signal bearing a determinable relationship to the useful signal is produced.
In general, in accordance Wit1 this invention known signai-to-noise enhancement algorithms can be implemen ed in the signal processing means. The latter is conveniently a suitably configured computer hardware and software.
The useful signal can be used according to the invention in a number of ways. A first option is as a mere supervisory check on existing operation of the machine, thus focusing on monitoring the operator or devices already used for detection and/or control of the tensions for supervisory or investigational and recording purposes. A second option is to display continuously the useful signal to the operator of the machine as an aid to him to enhance his existing technique of carrying out the tension control function. The archiving of the useful signal can afford a useful purpose as a part of the specification of the rope produced, to enable refuting clams of strand tension differentials or of guaranteeing conformance to specified standards, or mere historical reference, should a rope show problems in service.
The invention also covers the extension of the processing to provide feedback to a control means for automated control of the tensions of strands on a continuous operating basis.
The feedback to the automatic tension control may include the use of gravity generated electrical power, possibly by means of a pendulum and stepper motor to generate the electrical power on the rotating machine in favour of the use of slip rings. This electrical power could be stored in a battery for use to drive another device to adjust the tension of the strand. The feedback control of this mechanism could be by means of a radio telemetry system.
The invention will be more fully described with reference to the drawings, in which:- figure 1 is a front elevation of a transducer used in the invention, figure 2 is a side elevation of the transducer, figure 3 is a cross sectional side elevation of a fairlead bush used in the transducer, figure 4 is a schematic view of a rope closing machine showing installation of the invention, figure 5 is a schematic illustration of a system implementing the invention, figure 5a is a trigonometric sketch indicating a principle of deriving a reaction force on the transducer, figure 6 is a chart record of tension measurements made during trials of the invention, figure 7 is a further chart showing readings from the unloaded transducer, and figure 8 is a chart showing measurements before and after a tension adjustment had been made.
As shown in figures 1 to 3, the transducer 1 has a fairlead bush 2 fitted into it. The bush 2 has carefully formed radiuses 3 and is made of a high carbon alloy steel which may also be surface hardened to take service conditions. The strand (or wire) is passed through the bush bore 4 and in operation slides in the bore. The radiuses 3 minimise contact pressure peaks. Service trials over a period have proved that the arrangement is durable and has the advantage of simplicity and robustness. The transducer is one operating on a magneto-elastic effect which has advantages in this application, including absence of installation calibration requirement and of calibration drift, high overload tolerance, high spring constant with resulting elevated natural resonance frequency and immunity to environmental factors, including radio frequency interference.
Figure 4 shows in very simplified schematic form a rope closing machine 20 which rotates on a bed 21. Strands 22 run from reels or bobbins 23 ultimately to a fairlead 24 located immediately before a pre-former head 25 from which the strands pass through the three roller helix preformer 26 and the closing head 27 to emerge as the finished rope 28. The transducers are located on the fairlead 24, one for each strand. An analogous arrangement is made for stranders.
Figure 5 shows a system 10 installed according to the invention.
The friction in the bore of the transducer 12 results in the strand 11 (or wire) tension increasing through the bore, the resultant force on the transducer can be calculated by trigonometrical methods. Depending on the precise circumstances, or making simplifying assumptions as indicated in figure 5a, a simplified relationship, is :- F = T sin A where F is the force on the transducer, T is the strand (or wire) tension, and A is the angle of deviation of the strand through the transducer fairlead bush.
OR T=F sin A Thus, for example, where the force measured by the transducer is 0,4 kN, and the angle of deflection is 13 degrees, with the strand approaching the fairlead at right angles as shown, the derived strand tension is 1,78 kN.
As shown in figure 5, the transducer 12 relays a signal related to the force exerted on it by the strand (or wire) to a transmitter 13 mounted on the rotating parts of the machine. the transmitter sends a radio signal 14 to a receiver 15 mounted at a convenient location. This in turn relays the signal to a processor 16 which is a CPU of suitable capacity. A monitor 17 is available to display the processed signals continuously. The CPU has a hard drive to store all signals received and archive them for retrieval at any later stage if required. The CPU is programmed to process the raw signals by removal of noise from them, according to protocols and algorithm designs which can be developed in inter active mode with a particular machine.
This can take account of vibrational modes and other factors unique to each machine. The software can identify cyclical components in the raw signal over various periods of time; in particular, a cyclical periodicity related to the rotational speed of machine can be factored into the CPU, to enable removal of this factor from the signal. Statistical scatter can be processed to remove it by suitable software applied to the raw signal.
Thus figure 6 shows a pattern of signals received as raw data from a single transducer. Each dot represents one reading, the full pattern is taken over a period of 3 minutes. The pattern shows a cyclical repetition of ten cycles over this period.
The cyclical shape is inferred to result from the gravitational effect varying approximately sinusoidally the force on the load cell, as the machine rotates. This can be removed by application of a suitable Fourier analysis. To this must be added a compensation for centripetal force on the strand. The remaining random scatter of the dots can be processed by suitable statistical analysis, or simple arithmetic or geometric averaging.
The monitor can be used to give a readout for the machine operator on a continuous basis, giving for example, a bar chart indication of tension for each strand, perhaps shown between limit markers for the limits of tolerance according to a standard specified.
Figure 7 shows a pattern of signals (the scales both horizontally for time and vertically for force level are not necessarily the same) obtained when the machine is rotated without any strand in the fairlead bush. This confirms the cyclical effect due to gravity and could be used by subtraction to process the raw signal obtained in operation. The machine was stationary for a short period at 30.
Figure 8 shows dots in a range 31 obtained over an extended period of running, with screen wrap round taking place, that is, so that many passes are shown on the single sheet. The solid line 32 indicates an extended period when the machine was not running. The pattern of dots 33 show the increase in tension which followed an adjustment by the operator.
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