Method for magnetically detecting a variation in the cross-section of a metal reinforcing element and associated device

Abstract

The invention relates to a device (4) for magnetic detection of an abnormal variation in the cross-section of a moving metal reinforcing element. The device comprises: - magnetizing means (5) configured to generate a periodic induction magnetic field so as to magnetize the metal reinforcing element (1) over its entire moving length, - detection means (6) configured to detect a variation in the magnetic flux generated by the moving metal reinforcing element (1) and to deliver a raw signal representative of the magnetic flux of the moving metal reinforcing element (1), and - first comparison means (14) configured to compare a first detection signal with at least a first detection threshold, the first detection signal being determined from the raw signal, and to detect an abnormal variation in the cross-section of the metal reinforcing element (1) on the basis of the result of the first comparison.

Description

[0001] DESCRIPTION

[0002] Title of the invention: Method for magnetically detecting a variation in the cross-section of a metallic reinforcement element and associated device

[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 method for magnetically detecting the variation of the section and a device for magnetically detecting the variation of the section in such a metallic reinforcement element.

[0006] Generally, the top of the 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 individual wires 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 point 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] Architectural defects are caused, in particular, by the absence of a single strand, a change in the helix pitch during the assembly of the single strands, a misalignment of at least one strand of the cable relative to the other strands, a total break, or a partial break. To guarantee the reliability of the reinforcement cable, it is necessary to be able to reliably detect these various defects.

[0012] Description of the invention

[0013] The present invention relates to a method for the continuous magnetic detection of abnormal variations in the cross-section of a moving metallic reinforcement element. The method comprises:

[0014] - magnetization of the moving metallic reinforcement element along its entire length by a periodic induction magnetic field to create regular variations in remanent magnetization in the moving metallic reinforcement element,

[0015] - detection of a variation in magnetic flux generated by the moving metallic reinforcement element,

[0016] - at least one initial comparison of a first detection signal to a first detection threshold, the first detection signal being determined from a raw signal representative of the variation in magnetic flux in the moving metallic reinforcement element, and

[0017] - detection of an abnormal variation in the cross-section of the metal reinforcement element from the result of the first comparison.

[0018] By "metal reinforcing element" we mean a metal reinforcing cable obtained from individual wires or strands assembled one on top of the other, or one of the individual metal wires or strands used to manufacture 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] By "abnormal variation" of the cross-section of a metal reinforcement element, we mean a variation in the cross-section of the reinforcement element which becomes less than a predetermined threshold cross-section value.

[0021] The presence of a defect in the metallic reinforcement element causes 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.

[0022] The abnormal variation in the cross-section of the metal reinforcement cable is representative of a defect involving a total break in the reinforcement element, a partial break in the reinforcement element or a decrease in the cross-section of the reinforcement element.

[0023] Preferably, the metallic reinforcement element is in motion inside an internal passage with a longitudinal axis delimited by a magnetizing coil that generates the periodic induction magnetic field and by a sensing coil, and the detection of 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 sensing coil and the raw signal representative of the variation of the magnetic flux in the moving metallic reinforcement element is delivered by the sensing coil.

[0024] Advantageously, determining the first detection signal includes:

[0025] - filtering of the raw signal by initial filtering means to obtain a filtered raw signal comprising peaks, and

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

[0027] Preferably, the process further includes rectification of the filtered raw signal, and integration of the raw, filtered and rectified signal to obtain a peak signal.

[0028] Preferably, the first detection threshold is determined from the peak signal value and the first detection signal is the peak value of the raw, filtered and rectified signal, the abnormal variation of the detected section being representative of a partial rupture of the reinforcing element.

[0029] Preferably, the first detection signal is the peak signal, and the first detection threshold is equal to a predetermined detection value. The abnormal variation in the detected cross-section is representative of a complete failure of the reinforcing element or a reduction in its cross-section. Preferably, the comparison of the first detection signal includes comparing the maximum value of the first detection signal to the first detection threshold.

[0030] Advantageously, the abnormal variation in the cross-section of the metal reinforcement element is determined when the maximum value of the first detection signal is less than the first detection threshold for a first predetermined duration.

[0031] Preferably, the method includes a second comparison of a second detection signal to a second detection threshold and a third comparison of the second detection signal to a third detection threshold, the second detection signal being the peak signal, the first detection signal being the peak value of the raw, filtered and rectified signal, the first detection threshold being determined from the value of the peak signal, the second threshold being equal to a predetermined detection value and the third threshold being equal to a fraction of the predetermined detection value.

[0032] Advantageously, the first comparison includes comparing the amplitude of the first detection signal to the first detection threshold, the second comparison includes comparing the amplitude of the second detection signal to the second detection threshold, and the third comparison includes comparing the amplitude of the second detection signal to the third detection threshold.

[0033] Preferably, the abnormal variation in the cross-section of the metal reinforcement element is determined when the amplitude of the first detection signal is less than the first detection threshold for a first predetermined duration or the amplitude of the second detection signal is less than the second detection threshold for a second predetermined duration or the amplitude of the second detection signal is less than the third detection threshold for a third predetermined duration.

[0034] The invention further relates to a method for manufacturing a metallic reinforcement element for pneumatic tires, the manufacturing method comprising: - a step of unwinding the metallic reinforcement element from a reel,

[0035] - a manufacturing step,

[0036] - at least one step of magnetic detection of the variation in the cross-section of the metallic reinforcement element according to the process as defined above, and

[0037] - a stoppage of the unwinding of the metallic reinforcement element of the coil upon detection of an abnormal variation in the cross-section of the reinforcement element.

[0038] Preferably, the manufacturing step is a surface preparation step, or dry wire drawing and washing, or heat treatment, or brass plating, or assembly of a plurality of reinforcing elements.

[0039] The invention further relates to a magnetic detection device for abnormal variations in the cross-section of a moving metallic reinforcement element. The device comprises:

[0040] - magnetization means configured to generate a periodic induction magnetic field so as to magnetize the metallic reinforcing element along its entire length to create regular variations in remanent magnetization in the moving metallic reinforcing element, - detection means configured to detect a variation in magnetic flux in the moving metallic reinforcing element and to deliver a raw signal representative of the variation in magnetic flux in the moving metallic reinforcing element, and

[0041] - first means of comparison configured to compare a first detection signal to at least a first detection threshold, the first detection signal being determined from the raw signal representative of the magnetic flux in the moving metallic reinforcement element, and to detect the abnormal variation of the cross-section of the metallic reinforcement element from the result of the first comparison.

[0042] Preferably, the magnetizing means comprise a first magnetizing coil and the sensing means comprise a sensing coil, the magnetizing coil and the sensing coil jointly defining a longitudinal axis passage for the reinforcing element, the sensing coil being configured to deliver the raw signal representative of the magnetic flux in the moving metallic reinforcing element.

[0043] Advantageously, the device further includes first filtering means configured to filter the raw signal representative of the magnetic flux in the moving metallic reinforcement element to obtain a filtered raw signal including dips.

[0044] Preferably, the device further includes a rectifier configured to rectify the filtered raw signal, and second filtering means configured to integrate the filtered and rectified raw signal and deliver a peak signal identical to the filtered, rectified and integrated raw signal.

[0045] Advantageously, the device further includes determination means configured to determine the peak value of the raw, filtered and rectified signal, and to deliver the first detection signal identical to the peak value of the raw, filtered and rectified signal.

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

[0047] Preferably, the first means of comparison are configured to determine the abnormal variation in the cross-section of the metallic reinforcement element when the amplitude of the first detection signal is below the first detection threshold for a first predetermined duration.

[0048] Advantageously, the device includes second means for comparing a second detection signal to a second detection threshold and third means for comparing the second detection signal to a third detection threshold, the second detection signal being the peak signal, the first detection threshold being determined from the value of the peak signal, the second threshold being equal to a predetermined detection value, and the third threshold being equal to a fraction of the predetermined detection value. Brief description of the drawings

[0049] 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:

[0050] [Fig 1] is a schematic view of the cross-section of a tire reinforcement cable,

[0051] [Fig 2] is a side view of the reinforcing cable illustrated in figure 1,

[0052] [Fig 3] schematically illustrates a magnetic detection device for variations in the cross-section of a metallic reinforcement cable according to an example of an embodiment of the invention,

[0053] [Fig 4] is a schematic cross-sectional view of the magnetization and detection coils of the magnetic detection device in Figure 3,

[0054] [Fig 5] schematically illustrates an example of a magnetic detection method for variations in the cross-section of a metallic reinforcement cable, implementing the magnetic detection device of Figure 3.

[0055] [Fig 6] schematically illustrates examples of the evolution of the electromotive force generated at the terminals of the detection coil as a function of time, and of the evolution of the supply voltage of the magnetization coil as a function of time,

[0056] [Fig 7] illustrates an example of detecting a partial break in the metal reinforcement cable,

[0057] [Fig 8] illustrates an example of detecting a variation in the cross-section of the metal reinforcement cable,

[0058] [Fig 9] illustrates an example of detecting a complete break in the metal reinforcement cable, and

[0059] [Fig 10] schematically illustrates an example of a manufacturing process for the metal reinforcement cable. Detailed description

[0060] 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”.

[0061] By “single strand” we mean an individual strand.

[0062] As can be seen in Figure 2, the single strands 2 of the reinforcing cable 1 are joined together by helical winding 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°.

[0063] The elongation axis AA forms the longitudinal axis of the metal reinforcement cable 1.

[0064] The illustrated metal reinforcement cable 1 comprises a single strand formed by the seven monostrands 2.

[0065] By strand, we mean an assembly of single strands 2 wound helically 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 0.20 and 1.40 mm, more preferably between 0.12 and 5.5 mm.

[0066] 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.

[0067] 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.

[0068] Figures 3 and 4 schematically illustrate an example of a magnetic detection device 4.

[0069] The magnetic detection device 4 detects abnormal or unusual variations in the cross-section of the moving metal reinforcement cable 1. Abnormal variations in the cross-section of the metal reinforcement cable 1 indicate a fault, which may include a point fault or a structural fault.

[0070] The magnetic detection device 4 includes magnetization means capable of generating a periodic induction magnetic field so as to magnetize the metallic reinforcement cable 1.

[0071] The magnetic detection device 4 also includes detection means capable of detecting a variation in the magnetic flux in the moving metal reinforcement cable 1, and of delivering a raw signal representative of the magnetic flux in the moving metal reinforcement cable 1.

[0072] The magnetic detection device 4 further includes processing means 8 connected to the magnetization means and the detection means.

[0073] In the illustrated embodiment, the magnetization means include a magnetization coil 5 and the detection means include a detection coil 6.

[0074] The magnetization coil support 5 is in contact with the detection coil support 6.

[0075] Each of the magnetization coils 5 and detection coils 6 have an annular shape.

[0076] The magnetizing coils 5 and the sensing coils 6 together define an internal passage 7 for the metallic reinforcement cable. The passage 7 runs longitudinally through the magnetic sensing device 4. The passage 7 extends along a longitudinal axis X-X' of the magnetic sensing device 4. The passage 7 is delimited by the bores of the magnetizing coils 5 and the sensing coils 6. The axes of the bores of the magnetizing coils 5 and 6 are coaxial with each other and with the longitudinal axis X-X'.

[0077] 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. The magnetization coils 5 and detection coils 6 each comprise, for example, between 5000 and 10000 turns 5a, 6a with a diameter between 0.05 mm and 0.1 mm.

[0078] It is assumed that the metal reinforcement cable 1 is carried along its entire length in 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.

[0079] 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).

[0080] The processing means 8 of the magnetic detection device include control means 9 for supplying voltage to the magnetization coil 5.

[0081] As will be described in more detail later, the processing means 8 also include first filtering means 10, second filtering means 11, a rectifier 12, means for determining a detection signal from a rectified filtered raw signal 13, first comparison means 14, second comparison means 15, third comparison means 16, a first counter 17, a second counter 18 and a third counter 19.

[0082] The first 10 filtering methods include a bandpass filter.

[0083] The control means 9 can supply the magnetizing coil 5 with a periodic voltage so that the magnetizing coil 5 generates a periodic magnetic induction field. The magnetic induction field is, for example, between 1 and 10 kA / m.

[0084] Figure 5 schematically illustrates an example of a magnetic detection method for an abnormal variation in the cross-section of the metal reinforcement cable 1 implementing the device 4. During a first step 20 the magnetization coil 5 is energized and generates the magnetic field, and the metal reinforcement cable 1 moves longitudinally inside the passage 7 of the magnetic detection device according to the arrow F shown in Figure 3.

[0085] The magnetic field generated by the magnetizing coil 5 magnetizes the metal reinforcement cable 1 along its entire length, creating regular variations in remanent magnetization in the moving metal reinforcement cable 1. A periodic remanent magnetization is thus created in the metal reinforcement cable 1.

[0086] The passage of a remanent magnetization Mr through the detection coil 6 generates an electromotive force Emax equal to: in which:

[0087] - S is the cross-section of the metal reinforcement cable 1,

[0088] -po is the magnetic permeability of the reinforcing cable material 1,

[0089] -V is the speed of movement of the reinforcement cable 1 in the detection coil 6,

[0090] - N is the number of turns 6a of the detection coil 6,

[0091] - Mr is the remanent magnetization of the reinforcement cable 1, and

[0092] - d is the distance from the center of the magnetizing coil 5 to the center of the sensing coil 6.

[0093] Thus, when the metallic reinforcement cable 1 is driven inside the detection coil 6 in a longitudinal direction and the cross-section S of the reinforcement cable 1 is constant, the electromotive force Emax describes peaks of the same amplitude.

[0094] Figure 6 illustrates an example of the evolution of the voltage U supplying the magnetization coil 5 and the electromotive force Emax generated at the terminals of the detection coil 6 as a function of time t.

[0095] The voltage U supplying the magnetization coil 5 is for example a square wave voltage with zero average value and period T0. From an instant t0 to an instant tl, the cross-section S of the reinforcement cable 1 is equal to a first value SI.

[0096] At time tl, the section S of the reinforcement cable 1 is equal to a second value S2 less than the first value SI.

[0097] From time t0 to time tl, the electromotive force Emax generated in the detection coil by the passage of the reinforcement cable 1 magnetized by the magnetization coil 5 includes periodic bursts of period TO with amplitude varying between values ​​-E l and E l , E l being a positive value.

[0098] From the instant tl, the electromotive force Emax generated in the detection coil by the passage of the reinforcement cable 1 magnetized by the magnetization coil 5 includes periodic bursts of period TO and amplitude varying between values ​​-E2 and E2, E2 being a positive value.

[0099] The value E2 is less than the value E1.

[0100] During a second step 21, the detection coil 6 detects the variation in magnetic flux generated during the longitudinal movement of the metallic reinforcement cable 1 in the passage 7 of the device.

[0101] The detection coil 6 delivers the raw signal representing the magnetic flux in the moving metallic reinforcement cable 1. This signal includes the electromotive force across the terminals of the detection coil 6.

[0102] During a third step 22, the determination means 13 determine a first detection signal and a second detection signal from the raw signal delivered by the detection coil 6.

[0103] To do this, the signal delivered by the detection coil 6 is filtered by the first filtering means 10 to extract the peaks of the electromotive force Emax.

[0104] The bandpass filter of the first filtering means 10 is centered on the period TO so as to extract the peaks of the electromotive force Emax.

[0105] Then the filtered raw signal is rectified by rectifier 12.

[0106] The first detection signal is the raw, filtered, and rectified signal. Furthermore, the raw, filtered, and rectified signal is smoothed by the second filtering means 1 1, which deliver a peak signal representative of the integration of the raw, filtered, and rectified signal.

[0107] The second means of filtering 1 1 include, for example, a low-pass filter.

[0108] The second detection signal is the peak signal.

[0109] During a fourth step 23, the first comparison means 14 detect an abnormal variation in the cross-section of the reinforcing cable 1 representative of the partial rupture of the reinforcing cable 1 from the comparison of the first detection signal to a first detection threshold, the second comparison means 15 detect a decrease in the cross-section of the reinforcing cable 1 from the comparison of the second detection signal to a second detection threshold, and the third comparison means 16 detect an abnormal variation in the cross-section of the reinforcing cable 1 representative of the total rupture of the reinforcing cable 1 from the comparison of the second detection signal to a third detection threshold.

[0110] The amplitude (maximum value or peak value) of the first detection signal is compared by the first comparison means 14 to the first detection threshold determined from the value of the peak signal.

[0111] The first detection threshold is, for example, equal to 0.95 times the peak signal value.

[0112] The value of the second detection signal is compared by the second means of comparison 15 to a second detection threshold equal to a predetermined detection value.

[0113] The value of the second detection signal is further compared by the third means of comparison 16 to a third detection threshold determined from the predetermined detection value.

[0114] The predetermined detection value is, for example, equal to the electromotive force across the terminals of the detection coil 6 when a fault-free reference reinforcement cable 1 passes over it. The third detection threshold is, for example, equal to 0.2 times the predetermined detection value.

[0115] When the amplitude of the first detection signal exceeds the first threshold, the value of the second detection signal exceeds the second threshold, and the value of the third detection signal exceeds the third threshold (fifth step 24), the metal reinforcement cable 1 is considered compliant and free of any abnormal cross-sectional variation (no defects). The process continues to step 21 while the metal reinforcement cable 1 continues to move longitudinally.

[0116] When the amplitude of the first detection signal is less than the first detection threshold or the value of the second detection signal is less than the second threshold or the value of the second detection signal is less than the third threshold (fifth step 24), the process continues to a sixth step 25.

[0117] When the amplitude of the first detection signal is less than the first detection threshold, during a seventh step 26, the first counter 17 is started for a first predetermined duration equal for example to 4 seconds.

[0118] If during the first predetermined time, the amplitude of the first detection signal is again greater than the first detection threshold (seventh step 27), the process continues to step 21 and the first counter 17 is reset.

[0119] If, during the first predetermined period, the amplitude of the first detection signal remains below the first detection threshold (seventh step 27), an abnormal variation in the cross-section of the metal reinforcement cable 1 is detected. The metal reinforcement cable 1 is partially ruptured, and the process continues to an eighth step 28.

[0120] When the value of the second detection signal is less than the second detection threshold, during a ninth step 29, the second counter 18 is started for a second predetermined duration equal for example to 15 seconds.

[0121] If during the second predetermined time, the value of the second detection signal is again greater than the second detection threshold (tenth step 30), the process continues to step 21 and the second counter 18 is reset.

[0122] If, during the second predetermined time, the value of the second detection signal remains below the second detection threshold (tenth step 30), an abnormal variation in the cross-section of the metal reinforcement cable 1 is detected. The metal reinforcement cable 1 has a cross-section smaller than a reference cross-section, and the process continues to the eighth step 28.

[0123] When the value of the second detection signal is less than the third detection threshold, during an eleventh step 31, the third counter 19 is started for a third predetermined duration equal for example to 2 seconds.

[0124] If during the third predetermined time, the value of the second detection signal is again greater than the third detection threshold (twelfth step 32), the process continues to step 21 and the third counter 19 is reset.

[0125] If, during the third predetermined time, the value of the second detection signal remains below the third detection threshold (twelfth step 30), an abnormal variation in the cross-section of the metal reinforcement cable 1 is detected. The metal reinforcement cable 1 is completely ruptured, and the process continues to the eighth step 28.

[0126] During the eighth step 28, 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.

[0127] Alternatively, the detection device 4 may include only the first means of comparison to detect a variation in the cross-section of the metal reinforcement cable 1 or a total or partial rupture of the metal reinforcement cable 1.

[0128] According to yet another variant, the detection device 4 may include first means of comparison for detecting a variation in the cross-section of the metal reinforcement cable 1 or a total or partial rupture of the metal reinforcement cable 1, and second means of comparison for detecting a variation in the cross-section of the metal reinforcement cable 1 or a total or partial rupture of the metal reinforcement cable 1.

[0129] Figure 7 illustrates an example of detection of a partial break in the metal reinforcement cable 1.

[0130] The Emax l curve represents the electromotive force generated at the terminals of the detection coil 6 as a function of time t, the Sr curve represents said rectified electromotive force, the Sc curve represents the peak signal as a function of time t and the SI curve represents the first detection threshold.

[0131] Up to a time tl O, the instantaneous maximum values ​​of Emax l are greater than the first detection threshold SI.

[0132] At time t10, an instantaneous maximum value of Emax l is less than the first detection threshold SI. The first counter 17 is started. As the instantaneous maximum values ​​of Emax l remain less than the first detection threshold SI during the first predetermined duration Tl, at time t20 when the first counter 17 reaches the first duration Tl, the partial rupture of the metal reinforcement cable 1 is detected.

[0133] Partial breakage of the metal reinforcement cable 1 is caused by the breakage of at least one of the single strands of the metal reinforcement cable 1, at least one of the single strands of the metal reinforcement cable 1 not being cut.

[0134] Figure 8 illustrates an example of detecting an abnormal variation in the cross-section of the metal reinforcement cable 1.

[0135] The Emax l curve represents the electromotive force generated at the terminals of the detection coil 6 as a function of time t, the Sc curve represents the peak signal as a function of time t and the S2 curve represents the second detection threshold.

[0136] Up to a time t30, the peak signal Sc is greater than the second detection threshold S2.

[0137] At time t30, the peak signal Sc is below the second detection threshold S2. The second counter 18 is started. As the peak signal Sc remains below the second detection threshold S2 for the second predetermined duration T2, at time t40, when the second counter 19 reaches the second duration T2, the abnormal variation in the cross-section of the metal reinforcement cable 1 is detected.

[0138] The abnormal variation in the cross-section of the metal reinforcement cable 1 is here a decrease in the cross-section of the metal reinforcement cable 1 caused for example by the breakage of a single strand of said cable 1 or a change in the helix pitch during the operation of assembling the single strands of said cable 1 or a positioning defect of at least one single strand of said cable 1 in relation to the other single strands of said cable 1.

[0139] Figure 9 illustrates an example of detection of a total break in the metal reinforcement cable 1.

[0140] The Emax l curve represents the electromotive force generated at the terminals of the detection coil 6 as a function of time t, the Sc curve represents the peak signal as a function of time t and the S3 curve represents the third detection threshold.

[0141] Up to a time t50, the peak signal Sc is above the third detection threshold S3.

[0142] At time t50, the peak signal Sc is below the third detection threshold S3. The third counter 19 is started. As the peak signal Sc remains below the third detection threshold S3 for the third predetermined duration T3, at time t60, when the third counter 19 reaches the third duration T3, the total rupture of the metal reinforcement cable 1 is detected.

[0143] The total breakage of the metal reinforcement cable 1 is caused by the breakage of all the single strands of the metal reinforcement cable 1.

[0144] Figure 10 illustrates an example of a manufacturing process for the metallic reinforcement cable.

[0145] The process comprises first, second, third, fourth, fifth, sixth and seventh series of manufacturing steps 31 to 37 successive.

[0146] The sixth series of manufacturing steps 36 implements the detection process described previously at least once. The first series of manufacturing steps 31 involves unwinding a metallic single strand 38 from a reel 39.

[0147] The single strand 38 is descaled and then boraxed during a step 40 before being wound onto a reel 41. The manufacturing process continues with the second series of manufacturing steps 32.

[0148] 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.

[0149] The second series of manufacturing steps 31 includes the unwinding of the metallic monostrand 38 from the reel 41 a.

[0150] During a step 42, the monofilament 38 is dry drawn and then washed before being wound onto a reel 43.

[0151] Coil 43 resulting from the second series of manufacturing steps 32 is coil 43a from the third series of manufacturing steps 33.

[0152] The third series of manufacturing steps 33 includes the unwinding of the metallic monostrand 38 from the reel 43a.

[0153] The single strand 38 is heat-treated during a step 44 before being wound onto a reel 45.

[0154] Coil 45 resulting from the third series of manufacturing steps 33 is coil 45a from the fourth series of manufacturing steps 34.

[0155] The fourth series of manufacturing steps 34 includes the unwinding of the metallic monostrand 38 from the reel 45a.

[0156] The single strand 38 is brass-plated during a step 46 before being wound onto a reel 47.

[0157] Coil 47 resulting from the fourth series of manufacturing steps 34 is coil 47a from the fifth series of manufacturing steps 35.

[0158] The fifth series of manufacturing steps 35 includes the unwinding of the metallic single strand 38 from the reel 47a.

[0159] The single strand 38 is wet drawn during a step 48 before being wound onto a coil 49. 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.

[0160] 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.

[0161] During step 50, the monostrands 38, each wound on one of the reels 49a, 49b, 49c, are braided to form a core 51. The number of reels 49a, 49b, 49c illustrated is only indicative and may of course vary.

[0162] Next, the core 51 passes through the magnetization coil 5 to magnetize the core 51, then passes through the detection coil 6.

[0163] 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.

[0164] Next, the reinforcement cable 1 passes through the magnetization coil 5 to magnetize the reinforcement cable 1, then through the detection coil 6 before being wound onto a coil 53.

[0165] During step 52, a layer of monostrands 38 is assembled around the core 51.

[0166] 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 magnetization coil 5 and then through the detection coil 6 to detect a defect in the last layer assembled.

[0167] Coil 53 resulting from the sixth series of manufacturing steps 36 is coil 53a from the seventh series of manufacturing steps 37.

[0168] The seventh series of manufacturing steps 37 involves unwinding the reinforcement cable 1 from the reel 53a.

[0169] During a step 54, the reinforcement cable 1 can pass 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.

[0170] Alternatively, during step 54, the reinforcement cable 1 does not pass through the magnetization coil 5 and the detection coil 6.

Claims

DEMANDS 1. A method for magnetically detecting an abnormal variation in the cross-section of a moving metallic reinforcing element (1, 34), the method comprising: - magnetization of the moving metallic reinforcing element (1, 34) along its entire length by a periodic induction magnetic field to create regular variations in remanent magnetization in the moving metallic reinforcing element (1, 34), - detection of a variation in magnetic flux in the moving metallic reinforcing element (1, 34), - at least one initial comparison of a first detection signal to a first detection threshold, the first detection signal being determined from a raw signal representative of the variation of the magnetic flux in the moving metallic reinforcement element (1, 34), and - detection of an abnormal variation in the cross-section of the metallic reinforcement element (1, 34) from the result of the first comparison.

2. A method according to claim 1, wherein: - the metallic reinforcing element (1, 34) is in motion inside a passage (7) with a longitudinal axis (X-X') delimited by a magnetization coil (5) which generates the periodic magnetic induction field and by a detection coil (6), and in which - the detection of the variation of the magnetic flux which is generated during the longitudinal movement of the metallic reinforcement element in the inner passage (7) is detected by the detection coil (6) and the raw signal representing the variation of the magnetic flux in the moving metallic reinforcement element (1, 34) is delivered by the detection coil (6).

3. A method according to claim 1 or 2, wherein the determination of the first detection signal comprises: - filtering of the raw signal by first filtering means (10) to obtain a filtered raw signal comprising peaks, and - a determination of the first detection signal from the filtered raw signal.

4. Method according to claim 3, further comprising rectification of the filtered raw signal, and integration of the raw, filtered and rectified signal to obtain a peak signal.

5. Method according to claim 4, wherein the first detection threshold is determined from the peak signal value, and the first detection signal is the peak value of the raw, filtered and rectified signal, the abnormal variation of the detected section being representative of a partial rupture of the reinforcing element (1, 34).

6. Method according to claim 4, wherein the first detection signal is the peak signal and the first detection threshold is equal to a predetermined detection value, the abnormal variation in the detected section being representative of a total rupture of the reinforcing element (1, 34) or of a decrease in the section of the reinforcing element (1, 34).

7. A method according to any one of claims 5 and 6, wherein the comparison of the first detection signal includes comparing the maximum value of the first detection signal to the first detection threshold.

8. Method according to claim 7, wherein the abnormal variation in the cross-section of the metallic reinforcement element is determined when the amplitude of the first detection signal is less than the first detection threshold for a first predetermined duration.

9. Method according to claim 4, comprising a second comparison of a second detection signal to a second detection threshold and a third comparison of the second detection signal to a third detection threshold, the second detection signal being the peak signal, the first detection signal being the peak value of the raw signal, filtered and rectified, the first detection threshold being determined from the value of the peak signal, the second threshold being equal to a predetermined detection value and the third threshold being equal to a fraction of the predetermined detection value.

10. Method according to claim 9, wherein the first comparison comprises the comparison of the amplitude of the first detection signal to the first detection threshold, the second comparison comprises the comparison of the amplitude of the second detection signal to the second detection threshold, and the third comparison comprises the comparison of the amplitude of the second detection signal to the third detection threshold. 1 1. Method according to claim 10, wherein the abnormal variation of the cross-section of the metal reinforcement element is determined when the amplitude of the first detection signal is less than the first detection threshold for a first predetermined duration or the amplitude of the second detection signal is less than the second detection threshold for a second predetermined duration or the amplitude of the second detection signal is less than the third detection threshold for a third predetermined duration.

12. Method for manufacturing a metallic reinforcement element (1) for a tire, the manufacturing process comprising: - a step of unwinding the metallic reinforcing element (1, 34) from a coil (35, 42a, 48a, 53a, 53b) at a non-zero speed, - a manufacturing step (40, 42, 44, 46, 50, 52, 54), - at least one magnetic detection step of the variation in the cross-section of the metallic reinforcing element (1) according to the method of any one of claims 1 to 11, and - a stoppage of the unwinding of the metallic reinforcement element (1) upon detection of an abnormal variation in the cross-section of the reinforcement element (1, 34).

13. Method according to claim 12, wherein the manufacturing step is a surface preparation step (40), or dry wire drawing and washing (42), or heat treatment (44), or brassing (42), or assembly of a plurality of reinforcing elements (52).

14. Magnetic detection device (4) for abnormal variation in the cross-section of a moving metallic reinforcing element (1, 34), the device comprising: - magnetizing means (5) configured to generate a periodic induction magnetic field so as to magnetize the metallic reinforcing element (1, 34) along its entire length to create regular variations in remanent magnetization in the moving metallic reinforcing element, - detection means (6) configured to detect a variation in magnetic flux in the moving metallic reinforcing element (1, 34) and to deliver a raw signal representative of the variation in magnetic flux in the moving metallic reinforcing element (1, 34), and - first means of comparison (14) configured to compare a first detection signal to at least a first detection threshold, the first detection signal being determined from the raw signal representative of the magnetic flux in the moving metallic reinforcement element (1, 34), and to detect an abnormal variation in the cross-section of the metallic reinforcement element (1, 34) from the result of the first comparison.

15. Device according to claim 14, wherein the magnetization means comprise a first magnetization coil (5) and the detection means comprise a detection coil (6), the magnetization coil (5) and the detection coil (6) jointly delimiting a longitudinal axis (X-X') passage (7) for the reinforcement element, the detection coil (6) being configured to deliver the raw signal representative of the magnetic flux in the moving metallic reinforcement element (1, 34).

16. Device according to claim 14 or 15, further comprising first filtering means (10) configured to filter the raw signal representative of the magnetic flux in the moving metallic reinforcement element (1, 34) to obtain a filtered raw signal comprising dips.

17. Device according to claim 16, further comprising a rectifier (12) configured to rectify the filtered raw signal, and second filtering means (11) configured to integrate the signal raw filtered and rectified and deliver a peak signal identical to the raw filtered, rectified and integrated signal.

18. Device according to claim 17, further comprising determination means (13) configured to determine the peak value of the raw, filtered and rectified signal, and deliver the first detection signal identical to the peak value of the raw, filtered and rectified signal.

19. Device according to any one of claims 14 to 18, wherein the first comparison means (14) are configured to compare the amplitude of the first detection signal to the first detection threshold.

20. Device according to claim 19, wherein the first comparison means (14) are configured to determine the abnormal variation in the cross-section of the metallic reinforcement element (1, 34) when the amplitude of the first detection signal is less than the first detection threshold for a first predetermined duration.

21. Device according to claim 18, comprising second means for comparing (15) a second detection signal to a second detection threshold and third means for comparing (16) the second detection signal to a third detection threshold, the second detection signal being the peak signal, the first detection threshold being determined from the value of the peak signal, the second threshold being equal to a predetermined detection value and the third threshold being equal to a fraction of the predetermined detection value.

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