Method for magnetically detecting at least one defect in a metallic reinforcement element and associated device

Abstract

A device (4) for the continuous magnetic detection of a defect in a moving metallic reinforcement element (1) is proposed. The device comprises: - first magnetization means (5) configured to generate a first continuous magnetic induction field so as to magnetize the moving reinforcement element (1), - detection means (6) configured to detect at least one change in magnetic flux generated by the occurrence of a defect in the moving reinforcement element (1) and to deliver a raw signal representative of the change in magnetic flux, and - comparison means (13) configured to compare a detection signal to a predetermined detection threshold representative of a defect, the detection signal being determined from the raw signal, and to determine the presence of at least one defect in the reinforcement element (13) from the result of the comparison. Figure for the abstract: Fig 3

Description

Title of the invention: Method for magnetically detecting at least one defect in a metallic reinforcement element and associated device. Technical field

[0001] The present invention relates to the field of magnetic detection of defects in a metallic reinforcement element.

[0002] More specifically, the invention relates to a magnetic detection device for the presence of a defect and a method for magnetically detecting a defect in such an element.

[0003] Generally the top of the tires includes metal reinforcement cables in particular to be rigid under tension and to transmit forces and avoid deformation at high speed.

[0004] Metallic reinforcement cables can also be integrated into other areas of the tires, whether for tires intended to equip a passenger vehicle or a heavy goods vehicle or for tires intended for other applications for example agricultural, military, mining, etc.

[0005] Reinforcing cables are obtained from single strands assembled one on top of the other, for example in a helix.

[0006] The reinforcing cable may have defects that need to be identified.

[0007] The point defects inherent in the process of transforming the reinforcing cable are caused by local changes in the magnetic properties of the reinforcing cable (magnetic permeability and remanent magnetization) and / or local changes in the cross-section of the reinforcing cable.

[0008] Architectural defects are caused in particular by the absence of a single strand, or a change in the helix pitch during the assembly operation of the single strands or a positioning defect of at least one single strand of the cable in relation to the other single strands of said cable, a weld or a partial break.

[0009] To guarantee the reliability of the reinforcement cable, it is necessary to be able to reliably detect its various defects. Description of the invention

[0010] The present invention relates to a method for the continuous magnetic detection of a defect in a moving metallic reinforcement element, the method comprising:

[0011] - a magnetization of the moving metallic reinforcing element by at least one first continuous magnetic induction field,

[0012] - a detection of at least one variation of a magnetic flux which is generated by the appearance of a defect in the moving metal reinforcement element,

[0013] - a comparison of a detection signal to a predetermined detection threshold representative of a fault, the detection signal being determined from a raw signal representative of the variation in magnetic flux, and

[0014] - a determination of the presence of at least one defect in the reinforcing element metallic from the result of the comparison.

[0015] By "metallic reinforcing element", we mean a metallic reinforcing cable obtained from single strands or unitary strands assembled one on top of the other, or one of the metallic single strands or unitary strands enabling the manufacture of this cable.

[0016] The reinforcing cable may comprise a single strand, or several strands assembled together. By "strand" is meant an assembly of individual strands wound helically around each other around the elongation axis of the reinforcing cable.

[0017] The presence of a defect in the metallic reinforcement element causes a variation in the magnetic properties (magnetic permeability and remanent magnetization) of the reinforcement element at the location of the defect or a variation in the cross-section of the reinforcement element, which in turn causes a variation in the magnetic flux generated by the passage of the metallic reinforcement element at the location of the defect.

[0018] Preferably, the method further comprises magnetizing the moving metallic reinforcement element by a second continuous magnetic induction field of identical value to that of the first magnetic induction field and of opposite direction to said first magnetic induction field.

[0019] Advantageously, the metallic reinforcement element is in motion inside an internal passage with a longitudinal axis delimited jointly by a first magnetization coil which generates the first continuous induction field and by a detection coil, and the variation of the magnetic flux which is generated during the longitudinal movement of the metallic reinforcement element in the internal passage, is detected by the detection coil and the raw signal representative of the variation of the magnetic flux is delivered by the detection coil.

[0020] Preferably, the inner longitudinal axis passage is jointly delimited by the first magnetization coil, by the detection coil and by a second magnetization coil which generates the second continuous induction magnetic field and which is arranged so that the detection coil is located between the first magnetization coil and the second magnetization coil, the induction magnetic field resulting from the first and second continuous induction magnetic fields taken at the center of the detection coil being zero.

[0021] Since the total magnetic field resulting from the first and second continuous induction magnetic fields taken at the center of the detection coil is zero, the detection by this of the variation of the magnetic flux is not disturbed by the first and second fields thus improving the sensitivity of detection of the variation of the magnetic flux generated by the defect of the metallic reinforcement element.

[0022] Thus, the sensitivity of detection of a defect in the metallic reinforcement element is improved, which allows detection of point defects generated by a variation in the magnetic properties of the metallic reinforcement element and of architectural defects generated by a variation in the cross-section of the metallic reinforcement element.

[0023] Advantageously, the determination of the detection signal includes:

[0024] - a filtering of the raw signal representative of the variation of the magnetic flux by filtering methods to obtain a filtered raw signal

[0025] - a rectification of the filtered raw signal, and

[0026] - a determination of the detection signal from the filtered rectified raw signal.

[0027] The filtering means include a low-pass filter or a band-pass filter.

[0028] Preferably, the raw filtered and rectified signal is the detection signal.

[0029] Advantageously, the determination of the detection signal includes an integration of the filtered and rectified signal, the detection signal being the filtered, rectified and integrated signal.

[0030] Preferably, the comparison of the detection signal includes the comparison of the amplitude of the detection signal to the predetermined detection threshold.

[0031] Advantageously, the presence of a defect in the metallic reinforcement element is determined when the absolute value of the amplitude of the detection signal is greater than the predetermined detection threshold.

[0032] Preferably, the determined defect includes a weld, a partial break in the metal reinforcement element, and / or a change in the cross-section of the metal reinforcement element and / or a misalignment of at least one single strand in the metal reinforcement element.

[0033] The invention further relates to a method for manufacturing a metallic reinforcement element for a tire, the manufacturing method comprising:

[0034] - a step in unwinding the metallic reinforcement element from a reel,

[0035] - at least one magnetic detection step for the presence of a defect in the element of metallic reinforcement according to the process as defined above, and

[0036] - a stoppage of the unwinding of the metallic reinforcement element of the coil during the determination of the presence of at least one defect in the metal reinforcement element.

[0037] The invention further relates to a device for the continuous magnetic detection of a defect in a moving metallic reinforcement element, the device comprising:

[0038] - of the first magnetization means configured to generate a first field continuous magnetic induction so as to magnetize the moving metallic reinforcing element,

[0039] - detection means configured to detect at least one variation of a magnetic flux that is generated by the appearance of a defect in the moving metallic reinforcement element and to deliver a raw signal representative of the variation in magnetic flux, and

[0040] - comparison means configured to compare a detection signal to a predetermined detection threshold representative of a defect, the detection signal being determined from the raw signal representative of the variation of the remanent magnetization of the metallic reinforcement element, and determine the presence of at least one defect of the metallic reinforcement element from the result of the comparison.

[0041] Preferably, the device includes second magnetization means configured to generate a second continuous magnetic induction field of identical value to that of the first magnetic induction field and of opposite direction to said first magnetic induction field so as to magnetize the moving metallic reinforcement element.

[0042] Advantageously, the first magnetization means comprise a first magnetization coil and the detection means comprise a detection coil, the first magnetization coil and the detection coil jointly defining a passage for the metallic reinforcement element.

[0043] Preferably, the second magnetization means comprise a second magnetization coil which is arranged so that the sensing coil is located between the first magnetization coil and the second magnetization coil, the resulting magnetic induction field of the first and second continuous magnetic induction fields taken at the center of the sensing coil being zero.

[0044] Advantageously, the device further comprises filtering means configured to filter the raw signal representing the variation of the magnetic flux to obtain a filtered raw signal, a rectifier configured to rectify the filtered signal and means for determining the detection signal from the filtered and rectified signal.

[0045] Preferably, the device further comprises an integrator configured to integrate the filtered and rectified raw signal, the detection signal being the filtered, rectified and integrated signal.

[0046] Advantageously, the comparison means are configured to compare the amplitude of the detection signal to the predetermined detection threshold.

[0047] Preferably, the comparison means are configured to determine the presence of said defect in the metallic reinforcement element when the absolute value of the amplitude of the detection signal is greater than the predetermined detection threshold. Brief description of the drawings

[0048] The present invention will be better understood and other objects, advantages and features will become apparent from the detailed description that follows, including embodiments given by way of illustration only and made with reference to the accompanying drawings, presented as non-limiting examples, which may serve to complete the understanding of the invention and the explanation of its implementation and, where appropriate, contribute to its definition, on which:

[0049] [Fig-1] is a schematic view of the cross-section of a reinforcing cable of the pneumatic,

[0050] [Fig.2] is a side view of the reinforcing cable illustrated in [Fig.1],

[0051] [Fig.3] schematically illustrates a magnetic fault detection device of a metallic reinforcement cable according to a first embodiment of the invention,

[0052] [Fig.4] is a schematic cross-sectional view of the magnetization and detection coils of the magnetic detection device of [Fig.3],

[0053] [Fig.5] schematically illustrates an example of a method for magnetically detecting a defect in a metallic reinforcement cable implementing the magnetic detection device of [Fig.3],

[0054] [Fig.6] schematically illustrates a magnetic fault detection device for a metallic reinforcement cable according to a second embodiment of the invention,

[0055] [Fig.7] is a schematic cross-sectional view of the magnetization and detection coils of the magnetic detection device of [Fig.6],

[0056] [Fig.8] schematically illustrates an example of the evolution of a first magnetic field in a first magnetization coil of the magnetic detection device of the [Fig.6],

[0057] [Fig.9] schematically illustrates an example of the evolution of a second magnetic field in a second magnetization coil of the magnetic detection device of [Fig.6],

[0058] [Fig. 10] schematically illustrates an example of the evolution of the total magnetic field resulting from the first and second magnetic fields in coils of the magnetic detection device of the [Fig. 6],

[0059] [Fig. 11] schematically illustrates a method for magnetically detecting a defect in a metallic reinforcement cable, implementing according to the magnetic detection device of [Fig. 6],

[0060] [Fig. 12] schematically illustrates an example of the signals delivered by the magnetic detection device according to the embodiments of the invention, and

[0061] [Fig. 13] schematically illustrates an example of a manufacturing process for the metallic reinforcement cable. Detailed description

[0062] Reference is made to [Fig.1] which schematically illustrates a cross-section of a metallic reinforcement cable 1 according to a first embodiment, comprising seven metallic monostrands 2 assembled according to a multilayer arrangement “1+6”.

[0063] By “single strand” we mean an individual strand.

[0064] As can be seen in [Fig.2], the single strands 2 of the reinforcing cable 1 are assembled together by helical winding along an elongation axis AA of the metallic reinforcing cable 1. We note [3] the helix angle of the assembly, for example between 0° and 30°.

[0065] The elongation axis AA forms the longitudinal axis of the metal reinforcement cable 1.

[0066] The illustrated metal reinforcement cable 1 comprises a single strand formed by the seven monostrands 2.

[0067] By strand, we mean an assembly of single strands 2 wound helix with each other around the elongation axis A - A of the metal reinforcement cable 1. For example, the single strands 2 have a diameter between 0.02 and 8 mm, preferably between 0.12 and 5.5 mm.

[0068] The illustrated strand comprises an inner layer CI comprising a single monostrand 2, and an outer layer CE which extends radially around the inner layer CI and which comprises six monostrands 2.

[0069] The metal reinforcement cable illustrated in [Fig.1] is given only as an example, and may have other designs with, for example, a different number of strands, and / or a different number of single strands, and / or a different arrangement of the single strands.

[0070] Figures 3 and 4 schematically illustrate a first example of a magnetic detection device 4.

[0071] The magnetic detection device 4 allows for the continuous detection of at least one defect in the moving metallic reinforcement cable 1. The defect may include a point defect or a structural defect.

[0072] The defect may include a point defect or an architectural defect.

[0073] The magnetic detection device 4 includes first magnetization means capable of generating a first continuous induction magnetic field so as to magnetize the metallic reinforcement cable 1.

[0074] The magnetic detection device 4 also includes detection means capable of detecting at least one variation in magnetic flux that is generated by the appearance of a defect in the moving metallic reinforcement cable 1, and to deliver a raw signal representative of the variation of the magnetic flux.

[0075] The magnetic detection device 4 further includes processing means 8 connected to the magnetization means and the detection means.

[0076] In the illustrated embodiment, the first magnetization means comprise a first magnetization coil 5 and the detection means comprise a detection coil 6.

[0077] The support of the first magnetization coil 5 is in contact with the support of the detection coil 6.

[0078] Each of the magnetization coils 5 and detection coils 6 have an annular shape.

[0079] The magnetization coils 5 and detection coils 6 jointly define an internal passage 7 for the metallic reinforcement cable. The passage 7 runs longitudinally through the magnetic detection device 4. The passage 7 extends along a longitudinal axis X-X' of the magnetic detection device 4. The passage 7 is delimited by the bores of the magnetization coils 5 and detection coils 6. The axes of the bores of the magnetization coils 5 and detection coils 6 are coaxial with each other and with the longitudinal axis X-X'.

[0080] Each coil of the magnetization coils 5 and detection coils 7 is formed of a copper wire wound around the axis X-X' to form a succession of turns 5a, 6a.

[0081] The magnetization coils 5 and detection coils 6 each comprise, for example, between 2000 and 8000 turns 5a, 6a of less than 1 mm in diameter.

[0082] It is assumed that the metal reinforcement cable 1 is drawn into the internal passage 7 of the device in a longitudinal direction indicated by the arrow F. The longitudinal displacement or movement of the metal reinforcement cable 1 can be carried out in a direction coaxial with the longitudinal axis X-X' of the magnetic detection device 4, or in a direction parallel to this axis.

[0083] The metal reinforcement cable 1 is for example unwound from a first rotating reel (not shown) to be wound onto a second rotating reel (not shown).

[0084] The processing means 8 of the magnetic detection device include control means 9 for supplying voltage to the first magnetization coil 5.

[0085] As will be described in more detail later, the processing means 8 also include filtering means 10, a rectifier 11, means for determining a detection signal from a filtered rectified raw signal 12, comparison means 13 and an integrator 14.

[0086] The filtering means 10 include a low-pass filter or a band-pass filter.

[0087] The control means 9 can supply the magnetizing coil 5 with a DC voltage so that the magnetizing coil 5 generates a continuous magnetic induction field. The continuous magnetic induction field is, for example, between 1 and 20 kA / m.

[0088] Fig. 5 schematically illustrates an example of a continuous magnetic detection method for a defect in the metallic reinforcement cable 1 implementing the device 4.

[0089] During a first step 21 the first magnetization coil 5 is energized and generates the magnetic field, and the metallic reinforcement cable 1 moves longitudinally inside the passage 7 of the magnetic detection device.

[0090] The magnetic field generated by the magnetizing coil 5 magnetizes the metal reinforcement cable 1 so as to create a remanent magnetization in the metal reinforcement cable 1. The metal reinforcement cable 1 is continuously magnetized.

[0091] The presence of a defect in the metal reinforcement cable 1 modifies the remanent magnetization and / or the cross-section of the metal reinforcement cable 1 at the location of the defect.

[0092] Thus, when the metallic reinforcement cable 1 is drawn inside the sensing coil 6 in a longitudinal direction, the variation in the remanent magnetization created by the magnetizing coil 5 and / or the variation in the cross-section of the metallic reinforcement cable 1 generates a variation in the magnetic flux in the sensing coil 6 at the location of the fault. The variation in the magnetic flux in the sensing coil 6 causes a variation in the electromotive force across the terminals of the sensing coil 6.

[0093] During a second step 22, the detection coil 6 detects each variation of the magnetic flux generated during the longitudinal movement of the metallic reinforcement cable 1 in the passage 7 of the device.

[0094] The detection coil 6 delivers a raw signal representative of the variation in magnetic flux. Said signal includes the electromotive force across the terminals of the detection coil 6.

[0095] During a third step 23, the determination means 12 determine a detection signal from the raw signal delivered by the detection coil 6.

[0096] To do this, the signal delivered by the detection coil 6 is filtered by the filtering means 10 to remove frequency noise.

[0097] When the filtering means 10 include a low-pass filter, the low-pass filter suppresses noises of frequencies higher than the cutoff frequency of said filter.

[0098] The cutoff frequency of the low-pass filter is determined according to the architecture of the reinforcement cable 1 and the parameters of the machines using the cable. The cutoff frequency is, for example, equal to 1000 Hz

[0099] The filtered raw signal is then rectified by the rectifier 11.

[0100] The determination means 12 determine the detection signal from the filtered and rectified raw signal.

[0101] If the processing means 8 do not include the integrator 14, the detection signal determined by the determination means 13 is the raw signal filtered and rectified.

[0102] If the processing means 8 include the integrator 14, the raw filtered and rectified signal is integrated by the integrator 14. The detection signal determined by the determination means 12 is the integrated signal.

[0103] During a fourth step 24, the comparison means 13 detect the presence of at least one defect in the reinforcement cable 1 from the detection signal.

[0104] The detection signal is compared by the comparison means 13 to a predetermined detection threshold representative of a defect.

[0105] The amplitude of the detection signal is compared by the comparison means 13 to the predetermined detection threshold.

[0106] The determination of the presence of a defect in the metal reinforcement cable 1 is carried out from the result of the comparison.

[0107] When the absolute value of the detection signal amplitude is less than the predetermined detection threshold (fifth step 25), the metal reinforcement cable 1 is considered to be free of defects. The process continues to step 22 while the metal reinforcement cable 1 continues to move longitudinally.

[0108] On the contrary, when the absolute value of the amplitude of the detection signal is greater than the predetermined detection threshold (fifth step 25), at least one defect in the metal reinforcement cable 1 is determined and the process continues to a sixth step 26.

[0109] During the sixth step 26, the unwinding of the metal reinforcement cable 1 is stopped, for example, so that it does not move in the reels 5, 6 to remedy the detected defect, for example by splicing the partially or totally broken metal reinforcement cable.

[0110] Alternatively, the number of defects in the metal reinforcement cable 1 is counted and the unwinding of the metal reinforcement cable 1 continues. The position of each detected defect is recorded.

[0111] The predetermined detection threshold is determined according to the architecture of the reinforcement cable 1, the type of fault to be detected and the parameters of the machine implementing reinforcement cable 1.

[0112] Figures 6 and 7 schematically illustrate a second example of the magnetic detection device 4.

[0113] The second example differs from the first example in that it further comprises second magnetization means capable of generating a second magnetic field continuous induction of the same value as the first magnetic induction and in the opposite direction to said first magnetic induction.

[0114] The second magnetization means comprise a second magnetization coil 30. The detection coil 6 is disposed between the first and second magnetization coils 5, 30.

[0115] The support of the first magnetization coil 5 is in contact on one side with the support of the detection coil 6 and the support of the second magnetization coil 30 is in contact on the other side with the support of the detection coil 6.

[0116] The detection coil 7 is centered between the first and second magnetization coils 5, 30.

[0117] The second magnetizing coil 30 has an annular shape. The magnetizing coils 5, 30 and the sensing coil 7 jointly define the inner passage 7 for the metal reinforcement cable. The passage 7, which extends along the longitudinal axis X-X', is defined by the bores of the magnetizing coils 5, 30 and the sensing coil 7. The axes of the bores of the magnetizing coils 5, 30 and the sensing coil 6 are coaxial with each other and with the longitudinal axis X-X'.

[0118] The second magnetization coil 30 is formed of a copper wire wound around the axis X-X' to form a succession of turns 30a.

[0119] The winding formed by the turns 5a of the first magnetization coil 5 is reversed with respect to the winding formed by the turns 30a of the second magnetization coil 30 so that the first and second magnetization coils 5, 30 deliver opposite magnetic fields as explained below.

[0120] Each magnetization coil 5, 30 comprises, for example, between 2000 and 8000 turns 5a, 6a of less than 1 mm in diameter. The detection coil 6 comprises, for example, between 3000 and 9000 turns 7a of less than 1 mm in diameter.

[0121] The control means 9 can supply the first and second magnetization coils 5, 30 with a DC voltage so that the first magnetization coil 5 generates a first continuous magnetic induction field directed towards the detection coil 5 and the second magnetization coil 30 generates a second continuous magnetic induction field directed towards the detection coil 6. The first and second continuous magnetic induction fields are for example between 1 and 20 kA / m.

[0122] Fig. 8 illustrates an example of the evolution of the first magnetic field generated by the first magnetization coil 5 along the longitudinal direction D of the coils 5, 6, 30.

[0123] We denote B1 the first magnetic field generated by the first magnetization coil 5.

[0124] The first magnetization coil 5 is located between points DI and D2. The value of the first field B1 is positive and maximum at the center of the first magnetization coil 5.

[0125] Fig. 9 illustrates an example of the evolution of the second magnetic field generated by the second magnetization coil 30 along the longitudinal direction D of the coils 5, 6, 30.

[0126] We denote B2 the second magnetic field generated by the second magnetization coil 30.

[0127] The second coil of magnetizations 30 is located between points D3 and D4.

[0128] As the windings of the first and second coils 5, 30 are reversed, for a current of the same sign passing through said coils 5 and 30, the value of the second field B2 is negative and minimal at the center of the second magnetization coil 30.

[0129] Fig. 10 illustrates an example of the evolution of a total magnetic field resulting from the first and second magnetic fields B1, B2 along the longitudinal direction D of the coils 5, 6, 30.

[0130] We denote Btotal the resulting magnetic field.

[0131] As previously stated, the first magnetizing coil 5 is located between points DI and D2, and the second magnetizing coil 30 is located between points D3 and D4. The first sensing coil 6 is located between points D2 and D3.

[0132] The value of the resulting field Btotal is positive and maximum at the center of the first magnetization coil 5 and the value of the resulting field Btotal is negative and minimum at the center of the second magnetization coil 30.

[0133] The value of the magnetic field is zero between the two magnetizing coils so that the magnetic field at the center of the detection coil 6, which is centered between the magnetizing coils 5 and 30, is zero.

[0134] The presence of a defect in the metal reinforcement cable 1 modifies the remanent magnetization and / or the cross-section of the metal reinforcement cable 1 at the location of the defect.

[0135] Thus, when the metallic reinforcement cable 1 is drawn inside the sensing coil 6 in a longitudinal direction, the variation in the remanent magnetization created by the first magnetizing coil 5 and / or the variation in the cross-section of the metallic reinforcement cable 1 generates a variation in the magnetic flux in the sensing coil 6 at the location of the fault. The variation in the magnetic flux in the sensing coil 6 causes a variation in the electromotive force across the sensing coil 7.

[0136] Since the resulting magnetic field Btotal at the center of the detection coil 6 is zero, the detection coil 6 is not disturbed by the first and second fields Bl, B2, thus improving the sensitivity of the detection of the variation in magnetic flux generated by the defect and thus improving the sensitivity of detecting a defect in the metallic reinforcement cable 1.

[0137] Fig. 11 schematically illustrates an example of a method for magnetically detecting the presence of a defect in the metallic reinforcement cable 1 implementing the second example of the device 4.

[0138] During a first step 41 the first and second magnetization coils 5, 30 are energized and generate the resulting magnetic field Btotal, and the metallic reinforcement cable 1 moves longitudinally inside the passage 7 of the magnetic detection device.

[0139] The first magnetic field B1 generated by the first magnetizing coil 5 magnetizes the metal reinforcement cable 1 so as to create a remanent magnetization in the metal reinforcement cable 1.

[0140] The process continues with steps 22, 23, 24, 25 and 26 as described above.

[0141] Figure 12 illustrates an example of the signal delivered Sb by the detection coil 6, of the filtered signal Sf, of the filtered and rectified signal Sr and of the detection signal Sd equal to the filtered and rectified signal Sr integrated by the integrator 14 according to time t, and the detection threshold Sde.

[0142] Between times t1 and t2, t3 and t4, t5 and t6, the absolute value of the amplitude of the detection signal Sd is greater than the detection threshold Sde.

[0143] The duration between times t5 and t6 is greater than the duration between times t1 and t2 and times t3 and t4.

[0144] A mispositioning of at least one single strand is detected between times t5 and t6.

[0145] The structure of the detection signal Sd between times t1 and t2 is characteristic of a partial rupture of the reinforcement cable 1 and the structure of the detection signal Sd between times t3 and t4 is characteristic of a weld of the reinforcement cable 1.

[0146] A partial break in the reinforcing cable 1 means that at least one single strand has a total break.

[0147] The detection device here comprises the magnetization coils 5, 30 for generating continuous induction magnetic fields. Alternatively, it would be possible to replace these magnetization coils with permanent magnets.

[0148] Fig. 13 illustrates an example of a manufacturing process for the metallic reinforcement cable.

[0149] The process comprises first, second, third, fourth, fifth, sixth and seventh series of successive manufacturing steps 31 to 37.

[0150] Each series of manufacturing steps 31, 32, 33, 34, 35, 36, 37 implements at least once the detection process described above.

[0151] The first series of manufacturing steps 31 involves unwinding a metallic monostrand 38 from a reel 39.

[0152] The monostrand 38 undergoes a surface preparation step during a step 40.

[0153] The monofilament 38 then passes into the magnetic detection device 4 before to be wound onto a 4L reel The manufacturing process continues with the second series of manufacturing steps 32.

[0154] The coil 41 resulting from the first series of manufacturing steps 31 is the coil 41a of the second series of manufacturing steps 32.

[0155] The second series of manufacturing steps 31 includes the unwinding of the metallic monostrand 38 from the reel 41a.

[0156] During a step 42, the monostrand 38 is dry drawn and then washed.

[0157] Next, the single strand 38 passes through the magnetic detection device 4 before being wound onto a reel 43.

[0158] The coil 43 resulting from the second series of manufacturing steps 32 is the coil 43a of the third series of manufacturing steps 33.

[0159] The third series of manufacturing steps 33 includes the unwinding of the metallic monostrand 38 from the reel 43a.

[0160] The monostrand 38 is heat-treated during a step 44.

[0161] Next, the single strand 38 passes through the magnetic detection device 4 before being wound onto a reel 45.

[0162] The coil 45 resulting from the third series of manufacturing steps 33 is the coil 45a of the fourth series of manufacturing steps 34.

[0163] The fourth series of manufacturing steps 34 includes the unwinding of the metallic monostrand 38 from the reel 45a.

[0164] The single strand 38 is brass-plated during a step 46.

[0165] Next, the single strand 38 passes through the magnetic detection device 4 before being wound onto a reel 47.

[0166] The coil 47 resulting from the fourth series of manufacturing steps 34 is the coil 47a of the fifth series of manufacturing steps 35.

[0167] The fifth series of manufacturing steps 35 includes the unwinding of the metallic monostrand 38 from the reel 47a.

[0168] The monostrand 38 is wet drawn during a step 48.

[0169] Next, the single strand 38 passes through the magnetic detection device 4 before being wound onto a reel 49.

[0170] The coils 49a to 49i of the sixth series of manufacturing steps are coils of single strand 38 which correspond to the coil 49 resulting from the fifth series of manufacturing steps.

[0171] The sixth series of manufacturing steps 36 includes the assembly of a plurality of single strands 38 wound on reels 49a to 49i to form the reinforcing cable 1.

[0172] During a step 50, the monostrands 38, each wound on one of the reels 49a, 49b, 49c, are assembled in a helix to form a core 51. The number of reels 49a, 49b, 49c illustrated is only indicative and may of course vary.

[0173] Next, the core 51 passes into the magnetic detection device 4.

[0174] During a step 52, the single strands 38 wound on the reels 49d to 49i are assembled on the core 51 to form the reinforcing cable 1. Here again, the number of reels 49a to 49i illustrated is only indicative and may vary.

[0175] Next, the reinforcing cable 1 passes through the magnetic detection device 4 before being wound onto a reel 53.

[0176] During step 52, a layer of monostrands 38 is assembled around the core 51.

[0177] Of course, the sixth series of manufacturing steps 36 can include at the step 52 the assembly of at least one additional layer around the core 51. Each step of assembling a layer is followed by passing the assembly obtained through the magnetic detection device 4 to detect a defect in the last layer assembled.

[0178] The coil 53 resulting from the sixth series of manufacturing steps 36 is the coil 53a of the seventh series of manufacturing steps 37.

[0179] The seventh series of manufacturing steps 37 includes the unwinding of the reinforcing cable 1 from the reel 53a.

[0180] During a step 54, the reinforcement cable 1 passes through the magnetization coil 5 to magnetize the reinforcement cable 1 then passes through the detection coil 6 then is cut to the desired length before being wound onto a coil 55.

[0181] If the presence of a defect is detected during one of the series 31 to 37 of steps, the unwinding of the reinforcing cable 1 or the single-strand metal 38 associated with this series of steps is stopped.

Claims

Demands

1. A method for the continuous magnetic detection of a defect in a moving metallic reinforcement element (1, 38), the method comprising: - magnetizing the moving metallic reinforcement element by at least a first continuous induction magnetic field, - detecting at least one variation in a magnetic flux which is generated by the appearance of a defect in the moving metallic reinforcement element, - comparing a detection signal to a predetermined detection threshold representative of a defect, the detection signal being determined from a raw signal representative of the variation in magnetic flux, and - determining the presence of at least one defect in the metallic reinforcement element (1, 38) from the result of the comparison.

2. Method according to claim 1, further comprising magnetizing the moving metallic reinforcement element (1, 38) by a second continuous magnetic induction field of identical value to that of the first magnetic induction field and of opposite direction to said first magnetic induction field.

3. A method according to claim 1 or 2, wherein: - the metallic reinforcing element (1) is in motion inside an internal passage (7) with longitudinal axis (X-X') delimited jointly by a first magnetizing coil (5) which generates the first continuous induction field and by a sensing coil (6), and wherein - the variation of the magnetic flux which is generated during the longitudinal movement of the metallic reinforcing element in the internal passage (7) is detected by the sensing coil (6) and the raw signal representing the variation of the magnetic flux is delivered by the sensing coil (6).

4. A method according to claim 3 dependent on claim 2, wherein the internal passage (7) with longitudinal axis (X-X') is jointly delimited by the first magnetizing coil (5), by the sensing coil (6), and by a second magnetizing coil (30) which generates the second continuous induction magnetic field and which is arranged so that the sensing coil (6) is located between the first magnetization coil (5) and the second magnetization coil (30), the resulting magnetic induction field from the first and second continuous magnetic induction fields taken at the center of the detection coil (6) being zero.

5. A method according to any one of claims 1 to 4, wherein the determination of the detection signal comprises: - filtering the raw signal representing the variation of the magnetic flux by filtering means to obtain a filtered signal, - rectifying the filtered raw signal, and - determining the detection signal from the rectified filtered raw signal.

6. Method according to claim 5, wherein the filtered and rectified raw signal is the detection signal.

7. A method according to claim 5, wherein the determination of the detection signal comprises an integration of the filtered and rectified raw signal, the detection signal being the filtered, rectified and integrated raw signal.

8. A method according to any one of claims 5 to 7, wherein the comparison of the detection signal includes comparing the amplitude of the detection signal to the predetermined detection threshold.

9. A method according to claim 8, wherein the presence of a defect in the metallic reinforcing element (1) is determined when the absolute value of the amplitude of the detection signal is greater than the predetermined detection threshold.

10. A method according to any one of claims 1 to 9, wherein the determined defect includes a weld, a partial break in the metal reinforcement element, and / or a change in the cross-section of the metal reinforcement element, and / or a misalignment of at least one single strand in the metal reinforcement element.

11. A method for manufacturing a metallic reinforcement element (1, 38) for pneumatics, the manufacturing method comprising: - a step of unwinding the metallic reinforcement element (1, 38) from a reel (39, 41, 41a, 43, 43a, 45, 45a, 47, 47a, 49, 49a, 49b, 49c, 49d, 49e, 49f, 49g, 49h, 49i, 53, 53a, 55), - at least one step of magnetically detecting the presence of a defect in the metallic reinforcement element (1, 38) according to the method of any one of claims 1 to 10, and - a stoppage of the unwinding of the metallic reinforcement element (1, 38) of the coil when determining the presence of at least one defect in the metallic reinforcement element (1, 38).

12. A device (4) for the continuous magnetic detection of a defect in a moving metallic reinforcement element (1, 38), the device comprising: - first magnetization means (5) configured to generate a first continuous magnetic induction field so as to magnetize the moving metallic reinforcement element (1, 38), - detection means (6) configured to detect at least one variation in a magnetic flux which is generated by the occurrence of a defect in the moving metallic reinforcement element (1), and to deliver a raw signal representative of the variation in magnetic flux, and - comparison means (13) configured to compare a detection signal to a predetermined detection threshold representative of a defect, the detection signal being determined from the raw signal representative of the variation in the remanent magnetization of the metallic reinforcement element (1, 38),and determine the presence of at least one defect in the metallic reinforcing element (1, 38) based on the comparison result.

13. Device according to claim 12, comprising second magnetization means (30) configured to generate a second continuous magnetic induction field of identical value to that of the first magnetic induction field and of opposite direction to said first magnetic induction field so as to magnetize the moving metallic reinforcement element (1, 38).

14. Device according to claim 12 or 13, wherein the first magnetization means comprise a first magnetization coil (5) and the detection means comprise a detection coil (6), the first magnetization coil (5) and the detection coil (6) jointly defining a passage (7) for the metallic reinforcement element.

15. A device according to claim 14 dependent on claim 13, wherein the second magnetization means comprise a second magnetization coil (30) which is arranged such that the sensing coil (6) is located between the first magnetization coil (5) and the second magnetization coil (30), the field magnetic induction resulting from the first and second continuous magnetic induction fields taken at the center of the detection coil (6) being zero.

16. Device according to any one of claims 12 to 15, further comprising filtering means (10) configured to filter the raw signal representing the variation of the magnetic flux to obtain a filtered signal, a rectifier (11) configured to rectify the filtered raw signal and means for determining (12) the detection signal from the filtered and rectified raw signal.

17. Device according to claim 16, further comprising an integrator (14) configured to integrate the filtered and rectified raw signal, the detection signal being the filtered, rectified and integrated signal.

18. Device according to claim 16 or 17, wherein the comparison means (13) are configured to compare the amplitude of the detection signal to the predetermined detection threshold.

19. Device according to claim 18, wherein the comparison means (13) are configured to determine the presence of said defect in the metallic reinforcement element when the absolute value of the amplitude of the detection signal is greater than the predetermined detection threshold.

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