Device for magnetically detecting at least one defect in a metal reinforcing element and associated method

Abstract

According to the invention, the device (4) for continuously magnetically detecting at least one defect in a moving metal reinforcing element (1) comprises a first and a second magnetisation coil (5, 6) and a detection coil (7) that jointly delimit an inner passage (9) of longitudinal axis (X-X1). The first magnetisation coil (5) is configured to generate a continuous first magnetic induction field oriented towards the detection coil (7), the second magnetisation coil (6) being configured to generate a continuous second magnetic induction field oriented towards the detection coil (7). The detection coil (7) is configured to detect a magnetic-flux variation generated by the occurrence of a defect in the metal reinforcing element (1) moving longitudinally through the inner passage (9), the defect in the metal reinforcing element being detected based on the magnetic-flux variation.

Description

[0001] DESCRIPTION

[0002] Title of the invention: Magnetic detection device for at least one defect in a metallic reinforcement element and associated method

[0003] technical field

[0004] The present invention relates to the field of magnetic detection of defects in a metallic reinforcement element.

[0005] More specifically, the invention relates to a magnetic detection device for a defect in a metallic reinforcement element, and a method for magnetically detecting a defect in such an element.

[0006] Generally, the top of tires includes metal reinforcement cables, notably to be rigid under tension and to transmit forces and avoid deformation at high speed.

[0007] Metal 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 other applications such as agricultural, military, mining, etc.

[0008] Reinforcing cables are obtained from single strands assembled one on top of the other, for example in a helix.

[0009] The reinforcement cable may have defects that need to be identified.

[0010] The defects inherent in the transformation process of 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.

[0011] The 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.

[0012] To guarantee the reliability of the reinforcement cable, it is necessary to be able to reliably detect its various defects. Description of the invention

[0013] The present invention relates to a continuous magnetic detection device for at least one defect in a moving metallic reinforcement element.

[0014] The device includes a first magnetization coil, a second magnetization coil and a detection coil arranged between the first and second magnetization coils.

[0015] According to a general characteristic, the first magnetizing coil, the sensing coil and the second magnetizing coil jointly define an internal longitudinal axis passage for the metallic reinforcement element.

[0016] According to another general characteristic, the first magnetizing coil is configured to generate a first continuous magnetic induction field directed towards the sensing coil, and the second magnetizing coil is configured to generate a second continuous magnetic induction field of the same value as the first magnetic induction field and directed towards the sensing coil so that the resulting magnetic induction field of the first and second continuous magnetic induction fields taken at the center of the sensing coil is zero.

[0017] According to another general characteristic, the detection coil is configured to detect a variation in magnetic flux generated by the occurrence of a defect in the longitudinally moving metallic reinforcement element in the inner passage, the defect in the metallic reinforcement element being detected from the variation in magnetic flux.

[0018] By "metallic reinforcement element", we mean a metallic reinforcement cable obtained from single strands or unitary strands assembled one on top of the other, or one of the single metallic strands or unitary strands allowing the manufacture of this cable.

[0019] The reinforcing cable may consist of a single strand, or several strands assembled together. By "strand," we mean an assembly of individual strands wound helically around each other around the axis of elongation of the reinforcing cable.

[0020] 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 through the detection coil at the location of the defect.

[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 the latter of the variation in magnetic flux is not disturbed by the first and second fields, thus improving the sensitivity of detection of the variation in magnetic flux generated by the defect in the metallic reinforcement element.

[0022] Thus, the sensitivity of defect detection in the metallic reinforcement element is improved, which allows for the 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] Preferably, the windings of the first and second magnetizing coils are reversed.

[0024] Advantageously, the detection coil is centered between the first and second magnetization coils.

[0025] Preferably, the support for the first magnetizing coil is in contact on one side with the support for the sensing coil, and the support for the second magnetizing coil is in contact on the other side with the support for the sensing coil. Alternatively, it is possible to provide that the support for the sensing coil is spaced away from the supports for the first magnetizing coil and the supports for the second magnetizing coil.

[0026] Advantageously, the detection coil is configured to deliver a raw signal representative of the variation in magnetic flux which is generated by the appearance of the defect in the longitudinally moving metallic reinforcement element in the internal passage, the device further comprising filtering means configured to filter the raw signal representative of the variation in magnetic flux to obtain a filtered raw signal, a rectifier configured to rectify the filtered raw signal, means for determining a detection signal from the rectified filtered signal and comparison means for comparing the detection signal to a predetermined detection threshold.

[0027] Filtering methods include a low-pass filter or a band-pass filter.

[0028] Preferably, the device also includes an integrator configured to integrate the filtered and rectified raw signal, the detection signal being the filtered, rectified and integrated raw signal.

[0029] Advantageously, the comparison means are configured to compare the amplitude of the detection signal to the predetermined detection threshold.

[0030] Preferably, the comparison means are configured to determine 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.

[0031] The invention further relates to a method for the continuous magnetic detection of a defect in a moving metallic reinforcement element.

[0032] The process includes:

[0033] - the generation, by a first magnetization coil, of a first continuous magnetic induction field oriented towards a detection coil,

[0034] - the generation by a second magnetizing coil of a second continuous magnetic induction field oriented towards the sensing coil, the sensing coil being arranged between the first and second magnetizing coils such that the resulting magnetic induction field from the first and second continuous magnetic induction fields taken at the center of the sensing coil is zero, - a movement of the metallic reinforcement element within an internal passage jointly delimited by the first magnetizing coil, the sensing coil and the second magnetizing coil, and

[0035] - detection by the detection coil of a variation in magnetic flux which is generated by the appearance of a defect in the metallic reinforcement element moving longitudinally in the internal passage, the defect being detected from the variation in magnetic flux.

[0036] Preferably, the detection of the variation in magnetic flux by the detection coil includes:

[0037] - the output by the detection coil of a raw signal representative of the variation in magnetic flux generated by the appearance of the defect in the longitudinally moving metallic reinforcement element in the internal passage, and the determination of the defect in the metallic reinforcement element includes:

[0038] - determining a detection signal from the raw signal,

[0039] - a comparison of the detection signal to a predetermined detection threshold, and

[0040] - the determination of said defect in the metal reinforcement element being carried out from the result of the comparison.

[0041] Advantageously, the determination of the detection signal includes:

[0042] - filtering of the raw signal delivered by the detection coil using filtering means to obtain a filtered signal,

[0043] - a rectification of the raw filtered signal, and

[0044] - a determination of the detection signal from the filtered raw signal.

[0045] Preferably, the raw filtered and rectified signal is the detection signal.

[0046] Advantageously, the determination of the detection signal includes integrating the filtered and rectified raw signal, the detection signal being the filtered, rectified, and integrated raw signal. Preferably, the comparison of the detection signal includes comparing the amplitude of the detection signal to the predetermined detection threshold.

[0047] Advantageously, the 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.

[0048] 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.

[0049] The invention also relates to a method for manufacturing a metallic reinforcement element for tires.

[0050] The process includes:

[0051] - a step in unwinding the metallic reinforcement element from a coil,

[0052] - at least one magnetic detection step for the presence of a defect in the metallic reinforcement element according to the method as defined above, and

[0053] - a stoppage of the unwinding of the metallic reinforcement element of the coil when determining the presence of at least one defect in the metallic reinforcement element or counting the number of defects.

[0054] Brief description of the drawings

[0055] 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:

[0056] [Fig 1] is a schematic view of the cross-section of a tire reinforcement cable, [Fig 2] is a side view of the reinforcement cable shown in the figure

[0057] 1,

[0058] [Fig 3] schematically illustrates an example of a magnetic fault detection device for a metallic reinforcement cable according to an embodiment of the invention,

[0059] [Fig 4] is a schematic cross-sectional view of the magnetization and detection coils of the magnetic detection device in Figure 3,

[0060] [Fig 5] schematically illustrates an example of the evolution of a first magnetic field in a first magnetization coil of the magnetic detection device of figure 3,

[0061] [Fig 6] schematically illustrates an example of the evolution of a second magnetic field in a second magnetization coil of the magnetic detection device in Figure 3,

[0062] [Fig 7] schematically illustrates an example of the evolution of the total magnetic field resulting from the first and second magnetic fields in the coils of the magnetic detection device in Figure 3,

[0063] [Fig 8] schematically illustrates a method for magnetically detecting a defect in a metallic reinforcement cable according to an example of an implementation of the invention,

[0064] [Fig 9] schematically illustrates an example of the signals delivered by the magnetic detection device according to the embodiment of the invention and,

[0065] [Fig 10] schematically illustrates an example of a manufacturing process for the metallic reinforcement cable.

[0066] Detailed description

[0067] We refer to figure 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”.

[0068] By "monofrain", we mean an individual strand. As can be seen in figure 2, the monostrands 2 of the reinforcing cable 1 are assembled together by winding in a helix along an elongation axis AA of the metallic reinforcing cable 1. We denote P the helix angle of the assembly, for example between 0° and 30°.

[0069] The elongation axis AA forms the longitudinal axis of the metal reinforcement cable 1.

[0070] The illustrated metal reinforcement cable 1 comprises a single strand formed by the seven monostrands 2.

[0071] By strand, we mean an assembly of single strands 2 wound helix around 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.

[0072] The illustrated strand comprises an inner layer CI with a single strand 2, and an outer layer CE which extends radially around the inner layer CI and which has six strands 2.

[0073] The metal reinforcement cable illustrated in Figure 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.

[0074] Figures 3 and 4 schematically illustrate an example of a magnetic detection device 4.

[0075] The magnetic detection device 4 allows for the continuous detection of at least one fault in the moving metallic reinforcement cable 1. The fault may include a point fault or a structural fault.

[0076] The magnetic detection device 4 includes a first magnetization coil 5, a second magnetization coil 6 and a detection coil 7 arranged between the first and second magnetization coils 5, 6.

[0077] The magnetic detection device 4 further includes processing means 8 connected to the coils 5, 6, 7.

[0078] The support of the first magnetizing coil 5 is in contact on one side with the support of the detection coil 7 and the support of the second magnetizing coil 6 is in contact on the other side with the support of the detection coil 7.

[0079] The detection coil 7 is centered between the first and second magnetization coils 5, 6.

[0080] Each of the magnetization coils 5, 6 and the detection coil 7 has an annular shape. The magnetization coils 5, 6 and the detection coil 7 together define an internal passage 9 for the metallic reinforcement cable. The passage 9 runs longitudinally through the magnetic detection device 4. The passage 9 extends along a longitudinal axis X-X' of the magnetic detection device 4. The passage 9 is delimited by the bores of the magnetization coils 5, 6 and the detection coil 7. The axes of the bores of the magnetization coils 5, 6 and the detection coil 7 are coaxial with each other and with the longitudinal axis X-X'.

[0081] Each magnetization coil 5, 6 and detection coil 7 is formed of a copper wire wound around the axis X-X' to form a succession of turns 5a, 6a, 7a.

[0082] The winding formed by the turns 5a of the first magnetization coil 5 is reversed with respect to the winding formed by the turns 6a of the second magnetization coil 6 so that the first and second magnetization coils 5, 6 deliver opposite magnetic fields as explained below.

[0083] Each magnetization coil 5, 6 comprises, for example, between 2000 and 8000 turns 5a, 6a of less than 1 mm in diameter. The detection coil 7 comprises, for example, between 3000 and 9000 turns 7a of less than 1 mm in diameter.

[0084] It is assumed that the metal reinforcement cable 1 is drawn into the internal passage 9 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.

[0085] The metallic reinforcement cable 1 is, for example, unwound from a first rotating reel (not shown) to be wound onto a second rotating reel (not shown). The processing means 8 of the magnetic detection device include control means 10 for supplying voltage to the first and second magnetization coils 5, 6.

[0086] As will be described in more detail later, the processing means 8 also include filtering means 11, a rectifier 12, means for determining a detection signal from a filtered rectified raw signal 13, comparison means 14 and an integrator 15.

[0087] The filtering means 1 1 include a low-pass filter or a band-pass filter.

[0088] The control means 10 can supply the first and second magnetization coils 5, 6 with a DC voltage such that the first magnetization coil 5 generates a first continuous magnetic induction field directed towards the sensing coil 7, and the second magnetization coil 6 generates a second continuous magnetic induction field also directed towards the sensing coil. The first and second continuous magnetic induction fields are, for example, between 1 and 20 kA / m.

[0089] Figure 5 illustrates an example of the evolution of the first magnetic field generated by the first magnetization coil 5 along the longitudinal direction D of coils 5, 6, 7.

[0090] We denote B 1 the first magnetic field generated by the first magnetization coil 5.

[0091] 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.

[0092] Figure 6 illustrates an example of the evolution of the second magnetic field generated by the second magnetization coil 6 along the longitudinal direction D of the coils 5, 6, 7.

[0093] We denote B2 the second magnetic field generated by the second magnetization coil 6.

[0094] The second magnetization coil 6 is located between points D3 and D4. As the windings of the first and second coils 5, 6 are reversed, for a current of the same sign flowing through said coils 5 and 6, the value of the second field B2 is negative and minimal at the center of the second magnetization coil 6.

[0095] Figure 7 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 coils 5, 6, 7.

[0096] The resulting magnetic field is denoted by Btotal.

[0097] As previously stated, the first magnetization coil 5 is located between points DI and D2, and the second magnetization coil 6 is located between points D3 and D4. The detection coil 7 is located between points D2 and D3.

[0098] 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 6.

[0099] The value of the magnetic field is zero at the center of the detection coil 7.

[0100] 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.

[0101] Thus, when the metallic reinforcement cable 1 is drawn inside the sensing coil 7 in a longitudinal direction, the change in remanent magnetization created by the first magnetizing coil 5 and / or the change in the cross-section of the metallic reinforcement cable 1 generates a change in the magnetic flux in the sensing coil 7 at the location of the fault. The change in magnetic flux in the sensing coil 7 causes a change in the electromotive force across the terminals of the sensing coil 7.

[0102] Since the resulting magnetic field Btotal at the center of the detection coil 7 is zero, the detection coil 7 is not disturbed by the first and second fields B1, B2, thus improving the sensitivity of detection of the variation in magnetic flux generated by the fault and thus improving the sensitivity of detection of a fault in the metallic reinforcement cable 1.

[0103] Figure 8 schematically illustrates an example of a continuous magnetic defect detection method in the moving metallic reinforcement cable 1 implementing device 4.

[0104] During a first step 21 the first and second magnetizing coils 5, 6 are energized and generate the resulting magnetic field Btotal, and the metallic reinforcing cable 1 moves longitudinally inside the passage 9 of the magnetic detection device.

[0105] The first magnetic field B 1 generated by the first magnetizing coil 5 magnetizes the metal reinforcement cable 1 in such a way as to create a remanent magnetization in the metal reinforcement cable 1. The metal reinforcement cable 1 is continuously magnetized.

[0106] During a second step 22, the detection coil 7 detects each variation of the magnetic flux generated by the appearance of a fault in the reinforcement cable 1 during the longitudinal movement of the metallic reinforcement cable 1 in the passage 9 of the device.

[0107] The detection coil 7 delivers a raw signal representative of the variation in magnetic flux. This signal includes the electromotive force across the terminals of the detection coil 7.

[0108] During a third step 23, the determination means 13 determine a detection signal from the raw signal delivered by the detection coil 7.

[0109] To do this, the signal delivered by the detection coil 7 is filtered by the filtering means 1 1 to remove frequency noise.

[0110] When the filtering means 1 1 include a low-pass filter, the low-pass filter removes noises of frequencies higher than the cutoff frequency of said filter.

[0111] The cutoff frequency of the low-pass filter is determined based on the architecture of the reinforcement cable 1 and the parameters of the machines using the cable. For example, the cutoff frequency is 1000 Hz. The filtered raw signal is then rectified by the rectifier 12.

[0112] The determination means 13 determine the detection signal from the filtered rectified raw signal.

[0113] If the processing means 8 do not include the integrator 15, the detection signal determined by the determination means 13 is the raw signal filtered and rectified.

[0114] If the processing means 8 include the integrator 15, the raw filtered and rectified signal is integrated by the integrator 15. The detection signal determined by the determination means 13 is the integrated signal.

[0115] During a fourth step 24, the comparison means 14 detect at least one defect in the reinforcement cable 1 from the detection signal.

[0116] The detection signal is compared by the comparison means 14 to a predetermined detection threshold.

[0117] The amplitude of the detection signal is compared by the comparison means 14 to the predetermined detection threshold.

[0118] The determination of a defect in the metal reinforcement cable 1 is carried out from the result of the comparison.

[0119] When the absolute value of the detection signal amplitude is below 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.

[0120] 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 metallic reinforcement cable 1 is determined and the process continues to a sixth step 26.

[0121] During the sixth step 26, the unwinding of the metal reinforcement cable 1 is stopped, for example, so that it does not move through the reels 5, 6, 7 to remedy the detected defect, for example, by splicing the partially or completely broken metal reinforcement cable. 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.

[0122] The predetermined detection threshold is determined based on the architecture of the reinforcement cable 1, the type of fault to be detected and the parameters of the machine implementing the reinforcement cable 1.

[0123] Figure 9 illustrates an example of the signal delivered Sb by the detection coil 7, the filtered signal Sf, the filtered and rectified signal Sr and the detection signal Sd equal to the filtered and rectified signal Sr integrated by the integrator 15 according to time t, and the detection threshold Sde.

[0124] 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.

[0125] The duration between times t5 and t6 is greater than the duration between times t1 and t2 and the duration between times t3 and t4.

[0126] An incorrect positioning of at least one single strand is detected between times t5 and t6.

[0127] 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.

[0128] A partial break in the reinforcing cable 1 means that at least one single strand has a total break.

[0129] The detection device here includes magnetization coils 5 and 6 for generating continuous induction magnetic fields. Alternatively, these magnetization coils could be replaced by permanent magnets.

[0130] Figure 10 illustrates an example of a manufacturing process for the metallic reinforcement cable.

[0131] The process comprises first, second, third, fourth, fifth, sixth, and seventh successive series of manufacturing steps 31 to 37. Each series of manufacturing steps 31, 32, 33, 34, 35, 36, 37 implements the detection process described above at least once.

[0132] The first series of manufacturing steps 31 involves unwinding a metallic monostrand 38 from a reel 39.

[0133] The monostrand 38 undergoes a surface preparation step during a step 40.

[0134] The single strand 38 then passes through the magnetic detection device 4 before being wound onto a reel 41. The manufacturing process continues with the second series of manufacturing steps 32.

[0135] The coil 41 resulting from the first series of manufacturing steps 31 is the coil 41 a of the second series of manufacturing steps 32.

[0136] The second series of manufacturing steps 31 includes the unwinding of the metallic monostrand 38 from the reel 41 a.

[0137] During step 42, the monostrand 38 is dry drawn and then washed.

[0138] Next, the single strand 38 passes through the magnetic detection device 4 before being wound onto a reel 43.

[0139] Coil 43 resulting from the second series of manufacturing steps 32 is coil 43a from the third series of manufacturing steps 33.

[0140] The third series of manufacturing steps 33 includes the unwinding of the metallic monostrand 38 from the reel 43a.

[0141] The monostrand 38 is heat-treated during a step 44.

[0142] Next, the single strand 38 passes through the magnetic detection device 4 before being wound onto a reel 45.

[0143] Coil 45 resulting from the third series of manufacturing steps 33 is coil 45a from the fourth series of manufacturing steps 34.

[0144] The fourth series of manufacturing steps 34 includes the unwinding of the metallic monostrand 38 from the reel 45a.

[0145] The single strand 38 is brass-plated during a step 46.

[0146] Next, the single strand 38 passes through the magnetic detection device 4 before being wound onto a reel 47. The reel 47 resulting from the fourth series of manufacturing steps 34 is the reel 47a of the fifth series of manufacturing steps 35.

[0147] The fifth series of manufacturing steps 35 includes the unwinding of the metallic monostrand 38 from the reel 47a.

[0148] The monostrand 38 is wet drawn during a step 48.

[0149] Next, the single strand 38 passes through the magnetic detection device 4 before being wound onto a reel 49.

[0150] Coils 49a to 49i of the sixth series of manufacturing steps are coils of single strand 38 which correspond to coil 49 resulting from the fifth series of manufacturing steps.

[0151] The sixth series of manufacturing steps 36 involves the assembly of a plurality of single strands 38 wound on reels 49a to 49i to form the reinforcing cable 1.

[0152] During step 50, the single strands 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 shown is only indicative and may of course vary.

[0153] Next, the core 51 passes into the magnetic detection device 4.

[0154] 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.

[0155] Next, the reinforcement cable 1 passes through the magnetic detection device 4 before being wound onto a reel 53.

[0156] During step 52, a layer of monostrands 38 is assembled around the core 51.

[0157] Of course, the sixth series of manufacturing steps 36 can include in 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.

[0158] Coil 53 resulting from the sixth series of manufacturing steps

[0159] 36 is reel 53a of the seventh series of manufacturing steps 37. The seventh series of manufacturing steps 37 includes the unwinding of the reinforcing cable 1 from reel 53a.

[0160] 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.

[0161] If a defect is detected during one of the series 31 to

[0162] 37 steps, the unwinding of the reinforcing cable 1 or the single-strand metal 38 associated with this series of steps is stopped.

[0163] Alternatively, if a defect is detected during one of the series 31 to 37 of steps, the unwinding of the reinforcing cable 1 or the metallic single strand 38 continues in the series 31 to 37 of steps and the number of detected defects is counted.

Claims

DEMANDS 1. Device (4) for continuous magnetic detection of at least one defect in a moving metallic reinforcement element (1, 34) comprising: - a first magnetization coil (5), a second magnetization coil (6) and a detection coil (7) arranged between the first and second magnetization coils (5, 6), - the first magnetization coil (5), the detection coil (7) and the second magnetization coil (6) jointly defining an internal passage (9) with longitudinal axis (X-X') for the metallic reinforcement element, - the first magnetization coil (5) being configured to generate a first continuous magnetic induction field oriented towards the detection coil (7), the second magnetization coil (6) being configured to generate a second continuous magnetic induction field of identical value to that of the first magnetic induction field and oriented towards the detection coil (7) such that the resulting magnetic induction field of the first and second continuous magnetic induction fields taken at the center of the detection coil (7) is zero, and - the detection coil (7) being configured to detect a variation in magnetic flux generated by the appearance of a defect in the metallic reinforcement element (1) moving longitudinally in the internal passage (9), the defect in the metallic reinforcement element being detected from the variation in magnetic flux.

2. Device according to claim 1, in which the windings of the first and second magnetization coils are reversed.

3. Device according to claim 1 or 2, in which the sensing coil (7) is centered between the first and second magnetizing coils (5, 6).

4. A device according to any one of the preceding claims, wherein the support for the first magnetization coil (5) is in contact on one side with the detection coil support (7) and the support of the second magnetizing coil (6) is in contact on the other side with the support of the sensing coil (7).

5. Device according to any one of claims 1 to 4, wherein the detection coil (7) is configured to deliver a raw signal representative of the variation in magnetic flux generated by the appearance of the defect in the metallic reinforcement element (1, 34) moving longitudinally in the internal passage (9), the device (4) further comprising filtering means (11), configured to filter the raw signal representative of the variation in magnetic flux to obtain a filtered signal, a rectifier (12) configured to rectify the filtered raw signal, means for determining (13) a detection signal from the rectified filtered raw signal, and comparison means (14) for comparing the detection signal to a predetermined detection threshold.

6. Device according to claim 5, wherein the device (8) further includes an integrator (15) configured to integrate the filtered and rectified raw signal, the detection signal being the filtered, rectified and integrated raw signal.

7. Device according to claim 5 or 6, wherein the comparison means (14) are configured to compare the amplitude of the detection signal to the predetermined detection threshold.

8. Device according to claim 7, wherein the comparison means (14) are configured to determine said defect of the metallic reinforcement element (1, 34) when the absolute value of the amplitude of the detection signal is greater than the predetermined detection threshold.

9. A method for the continuous magnetic detection of a defect in a moving metallic reinforcing element (1), comprising: - a generation by a first magnetization coil (5) of a first continuous magnetic induction field oriented in the direction of a detection coil (7), - a generation by a second magnetization coil (6) of a second continuous magnetic induction field oriented in direction of the detection coil (7), the detection coil (7) being arranged between the first and second magnetization coils (5, 6), such that the resulting magnetic induction field from the first and second continuous magnetic induction fields taken at the center of the detection coil (7) is zero, - a movement of the metallic reinforcement element (1) within an internal passage (9) with a longitudinal axis (X-X') jointly delimited by the first magnetization coil (5), the detection coil (7) and the second magnetization coil (6), and - detection by the detection coil (7) of a variation in magnetic flux generated by the appearance of a defect in the metallic reinforcement element moving longitudinally in the inner passage (9), the defect being detected from the variation in magnetic flux.

10. A method according to claim 9, wherein the detection of the variation in magnetic flux by the detection coil comprises: - the output by the detection coil (7) of a raw signal representative of the variation in magnetic flux generated by the appearance of the defect in the longitudinally moving metallic reinforcement element in the internal passage (9), and the determination of the defect in the metallic reinforcement element includes: - determining a detection signal from the raw signal, - a comparison of the detection signal to a predetermined detection threshold, and - the determination of said defect in the metal reinforcement element being carried out from the result of the comparison. 1.

1. A method according to claim 10, wherein the determination of the detection signal comprises: - filtering of the raw signal delivered by the detection coil by filtering means (1 1 ) to obtain a filtered raw signal, - a rectification (12) of the filtered raw signal, and - a determination of the detection signal from the filtered raw signal.

12. Method according to claim 11, wherein the filtered and rectified raw signal is the detection signal.

13. Method according to claim 1 1 , 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.

14. A method according to any one of claims 10 to 13, wherein the comparison of the detection signal includes comparing the amplitude of the detection signal to the predetermined detection threshold.

15. Method according to claim 14, wherein the defect of the metallic reinforcement element (1, 34) is determined when the absolute value of the amplitude of the detection signal is greater than the predetermined detection threshold.

16. A method according to any one of claims 9 to 15, 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 mispositioning of at least one single strand in the metal reinforcement element.

17. Method for manufacturing a metallic reinforcement element (1) for a tire, the method comprising: - a step of unwinding the metallic reinforcement element (1, 34) from a coil (35, 42a, 48a, 53a, 53b), - at least one magnetic detection step for the presence of a defect in the metallic reinforcing element (1, 34) according to the method of any one of claims 9 to 16, and - a stoppage of the unwinding of the metallic reinforcement element (1, 34) of the coil when determining the presence of at least one defect in the metallic reinforcement element (1, 34) or a counting of the number of defects.

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