DE8808040U1 - Device for the non-destructive examination of elongated, magnetically conductive elements - Google Patents

Description

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¹ Case 4889/GER

COAL INDUSTRY (PATENTS) LIMITED, Hobaft House, Grosvenor Place, London SW1X 7AEj United Kingdom

Device for the non-destructive examination of elongated, magnetically conductive elements.

The invention relates to a device for the non-destructive examination of elongated, magnetically conductive elements and is used in particular to check the uniformity and condition of an element in a non-destructive manner, such as a wire rope, a metal pipe or a rod, which consist of magnetically conductive material.

For safety reasons it is essential to be able to check the condition of wire ropes and hoists intended for load-bearing purposes such as mine shaft hoists to ensure that, for example, in a rope made up of many strands, there has not been a break in any of the wires which would result in weakening of the wire rope at the point of breakage. It is also necessary to ensure that there is no deterioration within the wire rope due to corrosion or wear. Wire rope is normally oiled or greased during manufacture, but moisture can still enter and cause local rusting within the wire rope, weakening the strands of the wire rope and ultimately leading to breakage. This type of corrosion is not normally detectable by visual inspection and it is necessary to examine the wire rope by some other method to determine if corrosion or deterioration is occurring.

For this purpose, state -of-the-art proposals are known,

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to check the condition of elongated magnetically conductive elements, using magnetic sensors, and for example such a system is described in British Patent 1 539 313. In this known construction a magnet is provided with tubular pole pieces through which the wire rope is drawn, and Hall effect sensors are incorporated in the pole pieces to detect the magnetic flux generated and to detect modulations in the magnetic flux caused by liquids in the conducting path through the wire rope.

Another example is described in European Patent 0 239 537, in which two stacks of permanent magnets generate magnetic fields that oppose each other and which magnetize the wire rope passed between them. Faults in the wire rope are detected by monitoring the changes in the magnetic fluxes.

The object of the present invention is to propose an improved form of non-destructive testing of wire ropes using magnetic devices which do not use Hall effect devices in direct connection with the pole pieces of a magnet, but which have these devices located more centrally for much more efficient operation.

This task is performed in a device for the non-destructive investigation of elongated, magnetically conductive elements

3ö is essentially solved by providing a housing with two parts connected to one another by hinges, the housing containing a pair of magnetic poles which are arranged at the same distance around an element to be examined, the same poles being arranged diametrically opposite one another and first and second sensor devices being provided surrounding the element and between the poles of the magnetic device.

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The first sensor direction may contain windings which extend around the element and which detect local defects in the element.

The winding can be either saddle-shaped or conveniently kidney-shaped and can contain a large number of turns.

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of Hall effect sensors arranged radially around the element to sense flux changes indicative of corrosion or wear within the body of the element. The second sensor means is preferably arranged between the longitudinally spaced apart components of the first sensor means, with both sensor means being located between the pulse sections of the pair of magnetic means.

Each of the sensor devices can be connected to a corresponding display or recording device, for example a cassette recorder or a plotter. In addition or alternatively, a direct display can be provided so that a visual indication is given as soon as a defect is detected.

The element to be examined is moved past the device in operation and it may be necessary to provide means to compensate for the speed of movement, for example means may be used with appropriate circuits connected to the sensor means or a mechanical device such as a roller or wheel driven by the moving element may be used to generate a signal which makes the displayed output independent of the speed of the element relative to the device.

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The pair of magnetic devices can be formed by permanent magnets or by DC electromagnets.

The magnetic devices can be arranged with the sensor devices in a hinged component in order to be folded over an element to be examined.

The invention is explained in more detail below using an embodiment shown as an example in the drawings. The embodiment shown in the drawings serves to examine the quality of wire ropes made of steel wire that are used to suspend conveyor cages in the shaft system of a coal mine.

In the drawings shows:

Figure 1 is a side view of the device in its position on a rope to be examined;

Figure 2 is a sectional end view of the device of Figure 1 taken along the line II-II in Figure 1;

Figure 3 is a sectional view in the plane along III-III of Figure 1;

Figure 4 is a highly schematic representation of the device in its position on the rope;

Figures 5 and 6 show two forms of windings in schematic representation, as used in the first sensor device and

Figure 7 shows a waveform generated when a wire breakage occurs in the wire rope.

As illustrated in the drawings and in particular in Figures 1, 2 and 3, the device comprises a housing 1 which is divided into two halves 2, 3 which are connected to one another at 4 on one side by hinges and held together on the other side by quick-release latches. The device 1 is attached to a base 7 and a wire rope 8 can be passed through the housing 1.

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Attached to the upper half of the housing 2 is a spring-loaded arm 10 which is pivotally mounted on a support 12 at 11. The arm carries a wheel or roller 13 which is profiled and runs on the surface of the wire rope 8 under test and rotates as the wire rope is passed through the device 1. The wheel is connected to a shaft encoder in the lower part of the arm 10 at 14 and the encoder sends electrical signals via a flexible cable 15 to an outlet socket 16. Cables (not shown) are connected to the outlet socket 16 so that signals indicating the passage of the cable through the device can be picked up and recorded. S;

Inside the housing parts 2 and 3 there is an arrangement of magnets

provided, which in half 2 essentially consists of south pole magnets in the view of Figure 3 at the left end and north pole magnets at the right end. The magnetic arrangement in the upper half 3 is mirror-inverted, so that all south poles are in the direction of the left end in the view of Figure 3 and all north poles are towards the right end of the device. The arrangement is better seen from the schematic view according to Figure 4. The south poles are designated by the reference number 20 and the north poles by the reference number 21.

Between the south and north poles of each of the pole pieces, first sensor devices 22 are arranged, which consist of induction windings made up of many hundreds of wire turns, which are tightly wrapped around the rope 8

3Q. The shape of the windings can be designed as a saddle-shaped winding, as shown in Figure 5, or as a kidney-shaped winding, as shown in Figure 6. The purpose of the special shape of the windings is that the two halves 2 and 3 can be separated from each other at the hinges 4 when the device

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the associated circuits are provided in the middle of the device 1 surrounding the wire rope 8. The output signal from the sensor devices 22 and 23 is fed to a final output unit 24 (Figure 1) to enable connection to a recording device.

The sensor devices measure the magnetic flux flowing longitudinally outside the wire rope and effectively also measure the metallic cross-sectional area of the wire rope. This measurement is used to determine the degree of wear or corrosion in the wire rope as variations in the magnetic flux are monitored. The flux paths between the magnetic poles 20, 21 are both in the same direction within the

wire rope and these paths are marked 26 in Figure 4.

In operation, the latch 6 is opened to allow a wire rope to be introduced into the device 1 and the two halves 2, 3 are then moved together about the hinges and secured together. Starting from a given zero position, the wire rope is then moved through the device at a steady and continuous speed and by means of appropriate instruments connected to the outlets 16 and 24, any change in the flux path through the wire rope is detected by a distortion of the magnetic field surrounding the wire rope which is detected by one of the first sensor means 22. If there is a break in one of the wires of the wire rope, this will result in a pulse in the waveform as indicated in Figure 7, to which reference will now be made. In Figure 7, the two ends 30 of a wire in the wire rope are shown separated from each other by a break surface 31. The waveform shown below the ends 30 at 32 is shown as constant on either side of the break, but will appear as a deflection 33 when the break 31 occurs. The position of each break is determined by recording the length of wire rope through the device 1 by the number of revolutions made by the wheel 13, which is recorded by the steering encoder 14 and recorded in the form of an electrical signal.

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sent to the recording device to determine the exact location of the break point within the wire rope, which can then be marked»
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Similarly, the second sensor means 23 monitor changes in the magnetic flux on the outside of the wire rope and a signal representative of the metallic cross-sectional area is received from the Hall sensors. If the metallic cross-sectional area of the wire rope remains constant and there is no corrosion or rust, the flux path will give a constant output signal. If rust or rust has occurred inside the wire rope, this flux path is changed and the change in external flux detected by the Hall sensors is recorded and monitored. This is then related to the length of wire rope passing through the device and an estimate can be made as to whether the corrosion is sufficiently severe to make the wire rope unsafe for further use or whether it can continue to be used.

If required, the recording device can be designed to trigger a marking device which places a mark on the wire rope around the corresponding area where a break or corrosion has been detected.

Guides 28 are _provided in the device to ensure that the wire rope is positioned exactly between the magnetic poles 20 and 21 and the sensor devices 22, 23. The guides 28 are preferably made of non-magnetic material with extremely low coefficients of friction, which ensures that the resistance exerted by the device during pulling is constant.

The magnetic strength of the pole pieces 20, 21 is chosen so that the surface of the rope within the device is substantially magnetically saturated. The magnetic means may be either permanent magnets or direct current magnets. Since the device 1 is constructed in two halves with the arrangement 4 _{, it} is obvious that the device can be easily mounted on a

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wire rope can be fitted* without the end of the wire rope having to be threaded through the device* This is particularly useful when only certain areas of a wire rope are to be examined for corrosion or breakage, as the device can easily be fitted in the selected area without many metres of wire rope having to be passed through the device to be examined unnecessarily*

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to keep records of the wire rope being examined so that regular examinations can be recorded and compared, which represents a significant safety factor,

All features and advantages of the invention arising from the description, claims and drawings, including structural details and spatial arrangements, can be essential to the invention both individually and in any combination.

Claims (5)

Case 4889/GER Patent Attorneys Erosa&Brose
Dip!.!ng.Kes1A.Bro3et
Dipi. Ing. D. Karl Brose D-8023 Puflach/Mönchen Wioner Sir. 2. TtH. 080/79330 71-72 £·· ^UUrn DBr-au COAL INDUSTRY (PATENTS) LIMITED, Hobart House, Grosvenor Place, London SW1X 7AE, United Kingdom PROTECTION CLAIMS
15 1. Device for the non-destructive examination of elongated, magnetically conductive elements, characterized in that the device has a housing (1) with two parts (2, 3) connected by hinges (4), that the housing (1) contains a pair of magnetic poles (20, 21) which are arranged in such a way that they are at the same distance from an element (8) to be examined, surrounding it, with like poles being arranged diametrically opposite one another, and that a first sensor 25. sensor device (22) and a second sensor device (23) surround the element (8) and are arranged between the poles (20, 21) of the magnets. 2. Device according to claim 1, characterized in that the first sensor device (22) contains windings which the element (8) and which detect local defects in the element (8). 3. Device according to claim 2, characterized in that each winding has a saddle-shaped configuration. 4. Device according to claim 2, characterized in that each I ti * ' · tMI I 111 It t 4 4* 4% Il Il ft I till Ill Ill Ill I · I Il Il Il Il * Winding has a kidney-shaped shape. 5. Device according to one of claims 2, 3 or 4, characterized in that the first sensor device (22) contains windings with a large number of turns. 6. Device according to one of the preceding claims, characterized in that the second sensor device (23) contains a plurality of Hall effect sensors which are arranged radially around the element (8) in order to detect flux changes which are indicative of corrosion or wear within the element (8). 7. Device according to one of the preceding claims, characterized in that the second sensor device (23) is arranged between components of the first sensor device (22) which are arranged at a distance in the longitudinal direction. 8. Device according to one of the preceding claims, characterized in that both sensor devices (22, 23) are arranged longitudinally between the pole pieces (20, 21) of the pair of magnetic devices. 9. Device according to one of the preceding claims, characterized in that measuring devices (10, 11, 12, 13, 14) are provided for measuring the length of the element (8) which has passed through the device. 10. Device according to claim 9, characterized in that the measuring means comprise a roller (13) which is in engagement with the element (8) and is rotated by movement of the element, the roller (13) being connected to a light encoder arranged to send an electrical signal to a recording or monitoring device, the magnitude of which depends on the amount of rotation of the roller. 11. Device according to one of the preceding claims, characterized in that outlet devices (16, 24) are provided, # ■» ** ·« # · t4 it I « I » tit · · · · &bull; « 1« I · «·< tit * i 4 i«ii < t a i before connecting a display or recording device or a direct display device. 5 12, Device according to one of the preceding claims», characterized in that guide devices (28) are provided* to guide the element (13) in the housing of the device during the movement of the Element to be positioned correctly by the device io