Device and method for detecting defects of objects containing metal cords

Abstract

The invention relates to a device (1) for detecting a positioning defect of one of the metal cords relative to another of the metal cords within an object comprising a plurality of metal cords, said device comprising:-a magnetic field generator (10) arranged to generate a magnetic field, referred to as an inspection magnetic field, and positioned facing the object, -a magnetic sensor (12), referred to as a "primary magnetic sensor", for measuring the intensity of the inspection magnetic field, said device (1) being characterized in that the inspection magnetic field has, before being deformed by the plurality of metal cords, at least one neutral point in which the intensity of the inspection magnetic field is zero, and the primary magnetic sensor (12) is arranged in a selected position corresponding to the position of the neutral point relative to the magnetic field generator (10).

Description

Technical Field

[0001] The present invention relates to the field of detecting defects in an object containing metal cords, and more specifically, to detecting positioning defects of one metal cord relative to another metal cord, and more specifically, to detecting defects in an object (e.g., a reinforcing ply containing multiple reinforcing metal cords embedded in a rubber-based matrix) that forms part of a tire. Background Art

[0002] During the tire manufacturing process, a metal carcass ply is wound around a thin liner, and the two edges of the carcass ply are welded to each other to make the carcass ply cylindrical.

[0003] However, the welding may have defects, which will cause irreversible quality problems once the tire curing step is carried out. Poor welding of the carcass ply will cause the tire to be damaged during driving, or to a lesser extent, cause premature wear of the tire or discomfort during driving. Therefore, the welding must be inspected after the carcass ply is laid.

[0004] Currently, different methods can be used for this inspection:

[0005] - Using a metal comb to determine the position and spacing of the edges at the welding point. This method is not necessarily reliable and requires operator intervention to operate the metal comb;

[0006] - Using a laser profiler to scan the carcass ply before and after welding. This method is costly due to the need for hardware and dedicated software for defect analysis.

[0007] Therefore, there is currently no low-cost and easy-to-use solution for inspecting the welding of the carcass ply (more generally, the reinforcing ply) during the tire manufacturing process. Summary of the Invention

[0008] An object of the present invention is to provide a low-cost, easy-to-implement, reliable, and preferably automated solution for detecting defects in an object containing multiple metal cords (e.g., the metal carcass ply of a tire).

[0009] According to a first aspect, there is provided a detection device for detecting positioning defects of one metal cord relative to another metal cord in an object containing multiple metal cords, the object being, for example, a reinforcing ply containing multiple reinforcing metal cords embedded in a rubber-based matrix, the device comprising:

[0010] - A magnetic field generator, preferably composed of a magnet or a coil, arranged to generate a magnetic field called an "inspection magnetic field" and positioned facing the object such that the multiple metal cords cause deformation of the inspection magnetic field,

[0011] - A magnetic sensor, called a "primary magnetic sensor", arranged to measure the intensity of an inspection magnetic field,

[0012] The device is characterized in that the inspection magnetic field has at least one neutral point with zero intensity of the inspection magnetic field before being deformed by a plurality of metal cords,

[0013] And the primary magnetic sensor is arranged relative to the magnetic field generator at a selected position corresponding to the position of the neutral point.

[0014] According to advantageous and non - restrictive features, taken individually or in any combination:

[0015] - The magnetic field generator has an annular shape centered on an axis called the "central axis of the generator" and defines a free internal space, and the adjustment system includes a support that supports the primary magnetic sensor and engages in the free internal space such that the primary magnetic sensor can move along the central axis of the generator to change the position of the primary magnetic sensor along the central axis of the generator;

[0016] - The device includes at least one stabilizing element, such as a roller, that can contact the object to maintain a constant distance between the primary magnetic sensor and the outer surface of the object;

[0017] - The device includes at least one suspension mechanism, such as a spring, that can elastically press the stabilizing element against the object;

[0018] - The device includes a secondary magnetic sensor separated from the primary magnetic sensor, which is not subjected to the inspection magnetic field and is arranged facing an area of the object to measure the intensity of a magnetic field, called the "background magnetic field", that predominates in the object in the absence of the inspection magnetic field;

[0019] - The device includes a sub - assembly that forms a set of three carriages arranged in a row in a direction called the "longitudinal direction" and hinged in pairs with each other such that the three carriages can conform to the outer surface of the object, each carriage being supported on the outer surface to provide at least three corresponding separate support areas in the longitudinal direction, and the carriages are respectively composed of:

[0020] - A primary carriage that supports the magnetic field generator and the primary magnetic sensor and preferably at least one primary stabilizing element, such as a primary roller, the axis of rotation of the at least one primary stabilizing element being perpendicular to the longitudinal direction, which enables the primary carriage to roll on the outer surface of the object while maintaining the magnetic field generator and the primary magnetic sensor at a constant predetermined distance from the outer surface,

[0021] - A secondary carriage that supports a secondary magnetic sensor and at least one secondary stabilizing element, preferably a secondary roller, the axis of rotation of the at least one secondary stabilizing element being perpendicular to the longitudinal direction, which enables the secondary carriage to roll on the outer surface while maintaining the secondary magnetic sensor at a predetermined constant distance from the outer surface.

[0022] - A third carriage that supports at least one third stabilizing element, preferably a third roller, the axis of rotation of the at least one third stabilizing element being perpendicular to the longitudinal direction, which enables the third carriage to roll on the outer surface.

[0023] According to another aspect, a detection assembly is proposed, characterized in that it comprises a detection device and a drive system as described above, the drive system enabling the outer surface of an object to make a relative travel movement with respect to the magnetic field generator and the primary magnetic sensor in a predetermined direction called the "scanning direction", and the secondary magnetic sensor being arranged in front of the primary magnetic sensor with respect to the scanning direction, such that the same area of the outer surface of the object is successively covered by the secondary magnetic sensor measuring the background magnetic field and then by the primary magnetic sensor measuring the inspection magnetic field deformed by multiple metal cords of the object.

[0024] According to another aspect, a method for detecting a positioning defect of one metal cord relative to another in a metal cord-containing object, the object being, for example, a reinforcing ply containing multiple reinforcing metal cords embedded in a rubber-based matrix, the method comprising the following steps:

[0025] a) Providing a magnetic field generator and a primary magnetic sensor to form a detection device, the primary magnetic sensor being arranged relative to the magnetic field generator at a selected position corresponding to the position of the neutral point, the neutral point corresponding to the point where the intensity of the inspection magnetic field generated by the magnetic field generator is zero before being deformed by the multiple metal cords.

[0026] b) Positioning the detection device relative to the object such that the magnetic field generator and the primary magnetic sensor face the object.

[0027] c) Moving the detection device relative to the object and continuously acquiring the primary signal received by the primary magnetic sensor.

[0028] d) Detecting in the primary signal a signal feature indicating a positioning defect of the metal cords of the object.

[0029] According to advantageous and non-limiting features, taken alone or in any combination:

[0030] - Step a) includes step a0): Adjusting the detection device by positioning the primary magnetic sensor relative to the magnetic field generator at a selected position.

[0031] - In step a0), the primary magnetic sensor (12) is positioned using an adjustment system (143), which can adjust the position of the primary magnetic sensor (12) relative to the magnetic field generator (10), for example by tightening, and hold the primary magnetic sensor (12) in a selected position fixed relative to the magnetic field generator (10). The adjustment system (143) is included in a support (14) called the "primary support", which supports the magnetic field generator (10) and the primary magnetic sensor (12) and is provided with the adjustment system (143);

[0032] - The magnetic field generator (10) has an annular shape centered on an axis (A) called the "central axis of the generator" and defines a free internal space (101). The adjustment system (143) includes a support portion (142) that supports the primary magnetic sensor (12) and engages in the free internal space (101). And wherein, in step a0), the support portion (142) supporting the primary magnetic sensor (12) moves along the central axis (A) of the generator to change the position of the primary magnetic sensor (12) along the central axis (A) of the generator;

[0033] - In step b), at least one stabilizing element (18), such as a roller, is set in contact with the object (2) to maintain a constant distance between the primary magnetic sensor (12) and the outer surface (22) of the object (2);

[0034] - In step b), the stabilizing element (18) is elastically pressed against the object (2) by a suspension mechanism (19), such as a spring;

[0035] - In step c), the detection device moves relative to the object such that the primary magnetic sensor is successively set at different positions relative to the object, the different positions including at least one position of interest and a nominal position. At the position of interest, the magnetic sensor is set facing an area of interest of the object where potential defects are to be detected. At the nominal position, the magnetic sensor is set facing a defect-free area of the object different from the area of interest, so as to measure the nominal magnetic field intensity of the primary signal;

[0036] - The signal characteristic indicating a positioning defect of the metal cord of the object is a local extremum relative to the nominal magnetic field intensity, the local extremum having a magnetic field intensity greater than a first threshold or less than a second threshold;

[0037] - In step d), if it is determined that there is a local extremum and if the extremum has a magnetic field strength greater than the first threshold, it is determined that there is a defect corresponding to the overlap of two metal cords, and if the extremum has a magnetic field strength less than the second threshold, it is determined that there is a defect corresponding to a gap greater than the nominal gap between two consecutive metal cords;

[0038] - The method includes a step of acquiring a secondary signal before acquiring the primary signal, the secondary signal corresponding to the change during the movement of a magnetic field called the "background magnetic field" which represents the dominant magnetic field in the object in the absence of the inspection magnetic field, and wherein step d) includes processing the primary signal by subtracting the secondary signal from the primary signal;

[0039] - The previous step of acquiring the secondary signal is implemented by a secondary magnetic sensor (16), the secondary magnetic sensor (16) being separated from the primary magnetic sensor (12) and not being subjected to the inspection magnetic field, and in the previous step of implementing the acquisition of the secondary signal, the secondary magnetic sensor is arranged facing the region of the object (2).

[0040] - In step b), the sub-assembly (13) is set in contact with the outer surface (22) of the object (2), the sub-assembly (13) forming a set of three carriages (130a, 130b, 130c), the three carriages (130a, 130b, 130c) being arranged in a row in a direction (D) called the "longitudinal direction" and being articulated in pairs with each other such that the three carriages (130a, 130b, 130c) can conform to the outer surface (22) of the object (2), each carriage being supported on the outer surface (22) so as to provide at least three corresponding separate support regions in the longitudinal direction (D), the carriages (130a, 130b, 130c) being respectively composed of:

[0041] - A primary carriage (130a) which supports the magnetic field generator (10) and the primary magnetic sensor (12) and preferably at least one primary stabilizing element (18a) which is a primary roller, the axis of rotation (Xa) of the at least one primary stabilizing element (18a) being perpendicular to the longitudinal direction (D), which enables the primary carriage (130a) to roll on the outer surface (22) of the object (2) while maintaining the magnetic field generator (10) and the primary magnetic sensor (12) at a predetermined constant distance from the outer surface (22),

[0042] - A secondary carriage (130b) that supports a secondary magnetic sensor (16) and at least one secondary stabilizing element (18b), preferably a secondary roller, the axis of rotation (Xb) of the at least one secondary stabilizing element (18b) being perpendicular to the longitudinal direction (D), which enables the secondary carriage (130b) to roll on the outer surface (22) while maintaining the secondary magnetic sensor (16) at a predetermined constant distance from the outer surface (22).

[0043] - A third carriage (130c) that supports at least one third stabilizing element (18c), preferably a third roller, the axis of rotation (Xc) of the at least one third stabilizing element (18c) being perpendicular to the longitudinal direction (D), which enables the third carriage to roll on the outer surface (22) of the object (2).

[0044] To implement the previous step of obtaining the secondary signal and step c) of moving the detection device (1) relative to the object (2) and continuously obtaining the primary signal received by the primary magnetic sensor (12), the carriages (130a, 130b, 130c) roll on the outer surface (22) of the object (2) such that the same region of the object (2) first faces the primary carriage (130a), then the secondary carriage (130b), and finally the third carriage (130c).

[0045] - Step d) includes processing of the primary signal, which includes at least one of the following processing operations: filtering using a low-pass filter, calculating the absolute value of the signal, normalizing, thresholding, and combinations of these processing operations.

[0046] - The method is implemented to detect a positioning defect of one metal cord relative to another in a reinforcing ply containing metal cords extending along sides that are not parallel to the sides of the reinforcing ply. Description of the Drawings

[0047] Other features and advantages of the present invention will become apparent by reading the following description of the preferred embodiments. The description will be given with reference to the accompanying drawings, in which:

[0048] Figure 1 Shows a defect detection device used on an object;

[0049] Figure 2 Shows a part of an object without any defects;

[0050] Figure 3 Shows a part of an object with a cord gap defect;

[0051] Figure 4 Shows a part of an object with a cord overlap defect;

[0052] Figure 5 shows a support for holding a primary magnetic sensor and a magnetic field generator;

[0053] Figure 6 shows the magnetic field generator;

[0054] Figure 7 shows the magnetic field generator and the inspection magnetic field;

[0055] Figure 8 is a cross-sectional view of the support for holding the primary magnetic sensor and the magnetic field generator;

[0056] Figure 9 shows a device including three carriages, wherein a primary carriage holds the magnetic field generator and the primary magnetic sensor;

[0057] Figure 10 shows the steps of a defect detection method;

[0058] Figure 11 shows the signal received by the primary magnetic sensor. DETAILED DESCRIPTION

[0059] Device

[0060] Referring to Figure 1 , there is provided a detection device 1 for detecting a positioning defect of one metal cord relative to another in a plurality of metal cords 20 in an object 2. The metal cords 20 are preferably provided in a non-metallic matrix 21, preferably an elastomeric matrix such as a rubber-based matrix.

[0061] The object 2 is, for example, a reinforcing ply including a plurality of reinforcing metal cords embedded in a rubber-based matrix 21, such as a carcass ply or a crown ply of a tire. Thus, the object 2 can be a composite object including metal and rubber.

[0062] The object 2 can also be a bead wire for holding a tire in place on a rim.

[0063] Referring to Figure 2 , the object 2 includes a plurality of metal cords 20 arranged in a theoretical arrangement. For example, the cords 20 can be arranged in a regular pattern, such as equidistant from each other and parallel to each other. More specifically, as Figure 2 shown, the cords 20 can be distributed at a predetermined nominal pitch ε1, which is the center distance between adjacent cord segments. The cords can also be arranged at different distances from each other. The cords 20 can be, for example, straight or wavy.

[0064] The cord 20 preferably extends in a direction not parallel to the sides of the object 2. In the case of a tyre ply, the sides of the ply generally represent the boundaries in the width direction, i.e. the edges that axially delimit the ply, are parallel to each other and extend in the circumferential direction of the tyre. In the case of a carcass ply, the cords 20 are generally perpendicular to the sides of the ply. In the case of a crown ply, the cords 20 are generally oriented obliquely with respect to the sides.

[0065] The object 2 may have defects. More specifically, there may be a positioning defect of one of the metal cords 20 of the object 2 with respect to another of the metal cords 20. As Figure 3 shown, the defect may for example include a spacing ε2 between two consecutive metal cords 20, which spacing ε2 is greater than the expected nominal gap between two consecutive metal cords 20. As Figure 4 shown, the defect may also include an overlap of two metal cords 20.

[0066] More specifically, the object 2 may have a defect in the weld 23 between two edges of the object 2. The edges of the object 2 are the sides of the object 2 that join the respective sides of the object 2 together. Thus, the edges of the object 2 extend in a direction not parallel to the sides of the object 2. The edges preferably extend parallel to the cords 20, and thus the weld 23 generally extends parallel to the cords 20. In the case of a carcass ply, the edges and thus the weld 23 are generally perpendicular to the sides of the ply. In the case of a crown ply, the edges and thus the weld 23 are generally oriented obliquely with respect to the sides. The weld 23 is a region of the object 2 that may particularly have defects if the weld 23 is not well welded. The weld 23 generally constitutes an area of interest for defect detection of the object 2.

[0067] Referring to Figure 5 , the detection device 1 includes a magnetic field generator 10. The magnetic field generator 10 is for example a magnet, an electromagnet or a coil.

[0068] Advantageously, the magnetic field generator 10 is a single element, i.e. a single magnet, a single electromagnet or a single coil. In other words, the magnetic field generator 10 is not constituted by a combination of elements such as a combination of magnets.

[0069] The magnetic field generator 10 generates a magnetic field referred to as the "inspection magnetic field". A coil has the advantage of enabling better control of the magnetic field parameters.

[0070] As Figure 5 shown, the magnetic field generator 10 preferably has an annular shape centred on an axis A referred to as the "central axis of the generator" and defines a free internal space 101. It should be understood that the central axis A of the generator is the axis of rotation of the magnetic field generator 10. Preferably, the magnetic field generator 10 has an annular shape with a rectangular cross-section.

[0071] Preferably, the central axis A of the generator corresponds to the axis connecting the north and south poles of the magnetic field generator 10.

[0072] The magnetic field generator 10 may have other shapes, preferably a rotationally symmetric shape centered on the central axis A. The magnetic field generator 10 may, for example, be a hollow ring or an annular cylinder with a circular cross-section.

[0073] Referring to Figure 6 , the magnetic field generator 10 is designed such that the north and south poles are arranged one above the other. Thus, the magnetic field generator 10 includes a north part 102 and a south part 104, and in the example of the magnetic field generator 10 having an annular shape centered on the central axis A, each of the north part 102 and the south part 104 has an annular shape centered on the central axis A.

[0074] When checking that the magnetic field is not subject to magnetic interference related to metal elements (thus, for example, when the magnetic field generator 10 is far enough from the metal cords 20 of the object 2 such that the checking magnetic field is not deformed by the said metal cords 20 of the object 2), the checking magnetic field has at least one neutral point where the intensity is zero. "Zero" refers to the magnetic field intensity, the absolute value of which is preferably equal to 0 tesla. It should be understood that the neutral point is an inherent point of the magnetic field of the magnetic field generator 10.

[0075] Preferably, one or more neutral points of the magnetic field of the magnetic field generator 10 are located on the axis connecting the north and south poles of the magnetic field generator 10.

[0076] As Figure 7 shown, at the neutral points P1 and P2, the magnetic field lines of the checking magnetic field basically cancel each other out, and the intensity value of the checking magnetic field is basically zero. Therefore, at the neutral point, the deformation of the magnetic field lines of the checking magnetic field can be easily detected, because it can be inferred that the magnetic field lines of the checking magnetic field are deformed just by detecting that the magnetic field intensity at the neutral point is no longer zero, or at least has a specific deviation from the zero intensity value.

[0077] As Figure 5 shown, the detection device 1 further includes a magnetic sensor 12, referred to as the "primary magnetic sensor". The primary magnetic sensor 12 is configured to acquire a magnetic signal so as to measure the magnetic field intensity value. More specifically, the primary magnetic sensor 12 is arranged to measure the intensity of the checking magnetic field.

[0078] Preferably, the primary magnetic sensor 12 is a Hall effect sensor.

[0079] The primary magnetic sensor 12 is arranged relative to the magnetic field generator 10 at a selected position corresponding to the position of the neutral point of the checking magnetic field. Thus, in the absence of magnetic interference that can cause deformation of the checking magnetic field, it is assumed that the primary magnetic sensor 12 measures the magnetic field intensity that is not affected by the checking magnetic field.

[0080] Thus, the primary magnetic sensor 12 is arranged to measure the magnetic field strength at the neutral point. Thus, the primary magnetic sensor 12 is arranged to detect a change in the strength of the inspection magnetic field at the neutral point, thereby detecting a deformation of the inspection magnetic field.

[0081] Preferably, with reference to Figure 5 and Figure 8 , the device 1 includes a support 14 referred to as the "primary support". The primary support 14 supports the magnetic field generator 10 and the primary magnetic sensor 12.

[0082] According to a particular embodiment, the primary support 14 includes a first support portion 141 and a second support portion 142. The magnetic field generator 10 is fastened to the first support portion 141, and the primary magnetic sensor 12 is fastened to the second support portion 142.

[0083] The primary support 14 is preferably provided with an adjustment system 143 that can adjust the position of the primary magnetic sensor 12 relative to the magnetic field generator 10.

[0084] For example, as Figure 8 shown, the first support portion 141 includes a first thread 1411, and the second support portion 142 includes a second thread 1421 that is complementary to the first thread 1411. The second support portion 142 can be tightened through the first support portion 141, so that the position of the primary magnetic sensor 12 relative to the magnetic field generator 10 can be adjusted by screwing in or out the second support portion 142 that is tightened through the first support portion 141. In this example, the adjustment system 143 is considered to include the first support portion 141 and the second support portion 142.

[0085] According to Figure 8 the embodiment in which the magnetic field generator 10 shown has an annular shape, it can be understood that the second support portion 142 engages in the free internal space 101 defined by the magnetic field generator 10, so that the second support portion 142 can be moved along the central axis A of the generator by screwing in or out.

[0086] Preferably, as Figure 9 shown, the device 1 includes a secondary magnetic sensor 16 that is separated from the primary magnetic sensor 12. The secondary magnetic sensor 16 is intended to be arranged so as not to be subjected to the inspection magnetic field. In other words, the secondary magnetic sensor 16 is far enough from the magnetic field generator 10 such that the strength of the inspection magnetic field received by the secondary magnetic sensor 16 is zero. Thus, the secondary magnetic sensor 16 is arranged such that when the device 1 is arranged facing the object 2, the area of the object 2 facing the secondary magnetic sensor 16 is not subjected to the inspection magnetic field.

[0087] The secondary magnetic sensor 16 is arranged to measure the intensity of a magnetic field referred to as the "background magnetic field", which represents the residual magnetic field of the object 2, i.e., the magnetic field that predominates in the object 2 in the absence of an inspection magnetic field. This residual magnetic field may be due to the magnetization of the object 2, and more specifically, the magnetization of the metal cords of the object 2, for example, after a magnet has been placed near the object 2 for a certain period of time. The background magnetic field may also represent the magnetic field of the environment of the device 1 and the object 2, such as an industrial environment, which may include different magnetic tools.

[0088] Preferably, as Figure 9 shown, the device 1 includes at least one stabilizing element 18 that is capable of contacting the object 2 in order to maintain a constant predetermined distance between the magnetic field generator 10 and the object 2 and between the primary magnetic sensor 12 and the object 2 when the device 1 is in use. The predetermined distance depends in particular on the size and density of the cords 20. For example, the predetermined distance may be on the order of a few millimeters, such as 4 millimeters.

[0089] More specifically, as Figure 1 shown, when the device 1 is in use, the stabilizing element 18 is capable of contacting the outer surface 22 of the object 2. "In use" means that the device 1 is used to detect defects in the object 2. In use, it is desirable to maintain a predetermined distance between the magnetic field generator 10 and the object 2 such that, during use, in any region of the object 2 opposite the magnetic field generator 10, the object 2 is subjected to the inspection magnetic field in a similar manner. Similarly, in use, it is desirable to maintain a predetermined distance between the primary magnetic sensor 12 and the object 2 such that the primary magnetic sensor 12 measures the object 2 under similar conditions during use. According to an embodiment in which the device 1 includes the secondary magnetic sensor 16, when the device 1 is in use, the stabilizing element 18 can also maintain a constant predetermined distance between the secondary magnetic sensor 16 and the object 2.

[0090] The stabilizing element 18 preferably is capable of allowing the object 2 to move relative to the device 1 while in contact with the object 2. More specifically, preferably, the stabilizing element 18 is capable of rolling on the object 2.

[0091] The stabilizing element 18 may take the form of a roller as in the examples shown in Figure 1 and Figure 9 shown. The roller is capable of controlling the direction of movement of the device 1 relative to the object 2. The roller can also distribute the contact surface between the device 1 and the object 2 and control the distance between the primary magnetic sensor 12 and the object 2 (and optionally can also control the distance between the secondary magnetic sensor 16 and the object 2). The stabilizing element 18 may also be a load-bearing ball, for example. The diameter of the roller or the ball may depend on the diameter of the drum around which the object 2 is wound. The diameter of the roller or the ball may be on the order of a few centimeters, such as 2 centimeters.

[0092] Advantageously, with reference to Figure 9, the device 1 includes at least one suspension mechanism 19 which, when the device 1 is in use, can elastically press the stabilizing element 18 against the object 2. The suspension mechanism 19 can, for example, include a spring.

[0093] The stabilizing element 18 and the suspension mechanism 19 can also compensate for any inaccuracies in the positioning of the device 1 relative to the object 2 by means of a robotic arm.

[0094] According to Figure 9 the preferred embodiment shown, the device 1 includes a subassembly 13 which forms a set of three carriages 130a, 130b, 130c arranged in a row in a direction D called the "longitudinal direction". According to this embodiment, the device includes at least three stabilizing elements 18a, 18b, 18c.

[0095] As Figure 1 shown, the three carriages 130a, 130b, 130c are articulated in pairs with each other such that they can conform to the outer surface 22 of the object 2 by each being supported on the outer surface 22. When the device 1 is in use and each carriage 130a, 130b, 130c is supported on the outer surface 122 of the object 2, the device 1 thus has at least three separate support regions in the longitudinal direction D (corresponding respectively to the three carriages 130a, 130a, 130c). Thus, the device 1 is stably positioned relative to the object 2 and, during the use of the device 1, the distance between the primary magnetic sensor 12 and the object 2 remains constant.

[0096] The three carriages 130a, 130b, 130c include a primary carriage 130a, a secondary carriage 130b and a third carriage 130c.

[0097] The primary carriage 130a supports the magnetic field generator 10 and the primary magnetic sensor 12. The primary carriage 130a also preferably supports at least one stabilizing element 18a called a "primary stabilizing element".

[0098] Preferably, as Figure 9 shown, the primary stabilizing element 18a is a roller called a "primary roller" whose axis of rotation Xa is perpendicular to the longitudinal direction D. Thus, the primary stabilizing element 18a enables the primary carriage 130a to roll on the outer surface 22 of the object 2 while maintaining the magnetic field generator 10 and the primary magnetic sensor 12 at a constant predetermined distance from the outer surface 22.

[0099] The secondary carriage 130b supports the secondary magnetic sensor 16 and at least one secondary stabilizing element 18b. The secondary stabilizing element 18b is preferably a roller called a "secondary roller", the axis of rotation Xb of which is perpendicular to the longitudinal direction (D). The secondary roller 18b enables the secondary carriage 130b to roll on the outer surface 22 while keeping the secondary magnetic sensor 16 at a predetermined constant distance from the outer surface 22.

[0100] The third carriage 130c supports at least one third stabilizing element 19c. The third stabilizing element 19c is preferably a roller called a "third roller", the axis of rotation Xc of which is perpendicular to the longitudinal direction D. The third roller 19c enables the third carriage 130c to roll on the outer surface 22.

[0101] Preferably, the carriages 130a, 130b, 130c are connected to each other by pivot joints, usually at a certain spacing.

[0102] As Figure 9 shown, the device 1 includes at least one suspension mechanism 19 for applying pressure to at least one of the carriages 130a, 130b, 130c (in Figure 9 this case, the primary carriage 130a) such that when the device 1 is in use, at least one of the brackets 130a, 130b, 130c is pressed against the object 2.

[0103] As described above, the carriages 130a, 130b, 130c are arranged in a row. Thus, the carriages 130a, 130b, 130c include a front carriage, a central carriage and a rear carriage, as Figure 9 shown, the front carriage is the first of the carriages 130a, 130b, 130c in the primary direction S in the longitudinal direction D. In use, during the relative movement of the device 1 with respect to the object 2, the same area of the object 2 first faces the front carriage, then the central carriage, and finally the rear carriage.

[0104] Preferably, the front carriage corresponds to the secondary carriage 130b, the central carriage corresponds to the primary carriage 130a, and the rear carriage corresponds to the third carriage 130c.

[0105] The front carriage, the central carriage and / or the rear carriage can be pressured by the suspension mechanism 19.

[0106] The device 1 further includes a processing unit such as a processor. The processing unit is capable of acquiring and analyzing the signals received by the primary magnetic sensor 12 and the secondary magnetic sensor 16.

[0107] Component

[0108] As described above, the device 1 is capable of moving relative to the object 2. Accordingly, a detection component is proposed, which includes the device 1 and at least one moving system capable of relatively moving the device 1 with respect to the object 2.

[0109] According to a preferred embodiment, the mobile system can move the outer surface 22 of the object 2 in a predetermined direction B, called the "scanning direction", facing the magnetic field generator 10 and the primary magnetic sensor 12, as Figure 1 shown. Here, "move" refers to the relative movement of the outer surface 22 with respect to the device 1, and is not limited to the movement of the outer surface. The movement can be achieved by moving the device 1 relative to the outer surface 22 of the object 2.

[0110] The mobile system can be a robotic arm. Preferably, the device 1 can be attached to the robotic arm. The robotic arm can move the device 1 and hold it stably in a specific position facing the object 2.

[0111] According to a preferred embodiment, the object 2, which is usually the carcass ply of a tire, is unwound around a drum, and the mobile system is a drive system that rotates the drum, thereby rotating the object 2, and its outer surface 22 moves facing the device 1. Conversely, the drum can be fixed, and the drive system can rotate the device 1 relative to the drum.

[0112] Preferably, the scanning direction B is such that the secondary magnetic sensor 16 is arranged in front of the primary magnetic sensor 12 with respect to the scanning direction. In other words, the secondary carriage 130b is arranged in front of the primary carriage 130a with respect to the scanning direction. Therefore, the mobile system is designed such that in use, the same area of the outer surface 22 of the object 2 is successively covered by the secondary magnetic sensor 16 and then by the primary magnetic sensor 12.

[0113] Method

[0114] With reference to Figure 10 , a method is proposed for detecting a positioning defect of one of the metal cords 20 relative to another of the metal cords 20 in an object containing a plurality of metal cords 20 using the device 1.

[0115] Advantageously, the method is implemented to detect a positioning defect of one of the metal cords 20 relative to another of the metal cords 20 in a reinforcing ply (e.g., the carcass ply of a tire) containing metal cords 20 that do not extend parallel to the edges of the reinforcing ply.

[0116] The method preferably includes step a0): positioning the primary magnetic sensor 12 relative to the magnetic field generator 10 such that the primary magnetic sensor 12 is set at a selected position corresponding to the position of the neutral point of the inspection magnetic field (i.e., the magnetic field emitted by the magnetic field generator 10). Step a0) is a step of adjusting the device 1.

[0117] To this end, step a0) preferably includes step a01): the processing unit acquires the no-load signal received by the primary magnetic sensor 12 when the primary magnetic sensor 12 is not subjected to a magnetic field (in particular, when checking the magnetic field). In other words, when the primary magnetic sensor 12 is not near any magnetic interference, the magnetic field intensity is measured, which is called the "no-load magnetic field". Then, step a0) preferably includes step a02): the primary magnetic sensor 12 is arranged relative to the magnetic field generator 10 such that the signal received by the primary magnetic sensor 12 is equal to the no-load signal. Therefore, when the primary magnetic sensor 12 measures the no-load signal in the checking magnetic field, it can be considered that the primary magnetic sensor 12 is arranged at the neutral point of the checking magnetic field.

[0118] Step a02) includes moving the primary magnetic sensor 12 relative to the current generator 10. In particular, according to a specific embodiment, for example, by screwing in / screwing out, the second primary support portion 142 supporting the primary magnetic sensor 12 translates along the central axis A of the generator relative to the first primary support portion 141 supporting the magnetic field generator 10.

[0119] Preferably, as described above, the central axis A of the generator corresponds to the axis connecting the north and south poles of the magnetic field generator 10. Therefore, it can be understood that translating the second primary support portion 142 along the central axis A of the generator enables the primary magnetic sensor 12 to be easily positioned at the neutral point of the checking magnetic field.

[0120] The method includes step a): providing the device 1 adjusted in this way.

[0121] Then, the method includes step b): positioning the device 1 relative to the object 2 such that the magnetic field generator 10 and the primary magnetic sensor 12 are positioned facing the object 2, and more specifically, facing the outer surface of the object 2.

[0122] Preferably, the device 1 is positioned relative to the object 2 such that the axis connecting the north and south poles of the magnetic field generator 10 is perpendicular to the plane tangent to the outer surface 22 of the object 2.

[0123] It can be understood that the magnetic field is free. In other words, the magnetic field is not guided, for example, by branches that can allow the circulation of the magnetic field.

[0124] Preferably, the device 1 is arranged such that one or more stabilizing elements 18 of the device 1 are in contact with the object 2. Therefore, the distances between the object 2 and the magnetic field generator 10 and between the object 2 and the primary magnetic sensor 12 are known, and as long as the stabilizing elements 18 of the device 1 are in contact with the object 2, this distance is considered constant.

[0125] When the device 1 is positioned in this way, check that the magnetic field is distorted due to the metal cord 20 of the object 2. Here, the device 1 is considered not to be positioned facing the defect of the object 2. In other words, the device 1 is not positioned facing the area of the object 2 where a defect may exist (for example, the welding area called the "area of interest" between the two edges of the metal reinforcing cord of the tire).

[0126] Preferably, initially, and thus during the implementation of step b), the device 1 is positioned so as not to face the defect of the object 2.

[0127] In this position, the primary magnetic sensor 12 is considered to be in a position called the "nominal position" and receives a signal called the "nominal signal", which has a magnetic field strength called the "nominal intensity". In other words, when the primary magnetic sensor 12 is positioned facing the object 2 and not facing the defect, the primary magnetic sensor 12 receives the nominal signal, which is caused by the distortion of the inspection magnetic field caused only by the interference between the inspection magnetic field and the metal cord 20 of the object 2. This nominal signal is actually the basic signal and indicates the signal that should be received by the primary magnetic sensor 12 when no defect is detected in the object 2.

[0128] According to one embodiment, step b) further includes positioning the secondary magnetic sensor 16 to face the object 2. This includes, for example, setting the stabilizing element 18b in contact with the secondary carriage 130b that supports the secondary magnetic sensor 16, so that the magnetic sensor is set at a known distance from the object 2.

[0129] According to one embodiment, step b) includes setting the subassembly 13, which includes a set of three carriages 130a, 130b, 130c arranged in a column in the longitudinal direction D. The carriages 130a, 130, 130c are positioned such that the longitudinal direction D is collinear with the planned movement direction of the device 1 relative to the object 2. Advantageously, the carriages 130a, 130b, 130c are positioned such that the longitudinal direction D is collinear with the planned scanning direction of the outer surface 22 of the object 2. In other words, the carriages 130a, 130b, 130c are positioned in a column in the scanning direction. Preferably, the carriages 130a, 130b, 130c are positioned such that the front carriage is the secondary carriage 130b, the central carriage is the primary carriage 130a, and the rear carriage is the third carriage 130c.

[0130] Step b) can be achieved, for example, by operating the robotic arm 3 of the device 1.

[0131] Then, the method includes step c) of moving the device 1 relative to the object 2. According to one embodiment, the device 1 is moved, for example, by a robotic arm while the object 2 remains stationary. According to another embodiment, the object 2 is set to move relative to the device 1 while the device 1 remains stationary, for example, by a robotic arm.

[0132] Preferably, the object 2 is wound around the drum and is rotatable about its axis of rotation by a movement system that acts as a drive system. As a result, the outer surface 22 of the object 2 travels in the scanning direction facing the magnetic field generator 10 and the primary magnetic sensor 12. Preferably, the drive system drives the object 2 such that the object 2 performs only one complete rotation. Instead, the drive system can drive the magnetic field generator and the primary magnetic sensor so that they travel relative to the drum.

[0133] Thus, it can be understood that during the relative movement, each region of the object 2 that travels facing the magnetic field generator 10 is subjected to the inspection magnetic field.

[0134] According to a particular embodiment, as explained, preferably, during the relative movement, the same region of the outer surface 22 of the object 2 is successively covered by the secondary magnetic sensor 16 and then by the primary magnetic sensor 12. When the region of the object 2 faces the secondary magnetic sensor 16, that region is thus advantageously not magnetized by the magnetic field generator 10. As a result, the secondary magnetic sensor 16 receives a secondary signal corresponding to the background magnetic field (i.e., corresponding to the residual magnetic field of the object 2 and / or the magnetic field of the environment), and this secondary signal is advantageously independent of any magnetization of the object 2 due to the magnetic field generator 10.

[0135] According to an embodiment in which the device 1 includes the secondary magnetic sensor 16, step c) includes the processing unit continuously acquiring the secondary signal received by the secondary magnetic sensor 16. The secondary signal corresponds to the variation of the background magnetic field intensity during the relative movement.

[0136] Step c) further includes the processing unit continuously acquiring the primary signal received by the primary magnetic sensor 12. The primary signal varies in particular according to the variation of the intensity of the inspection magnetic field during the relative movement.

[0137] Preferably, during the relative movement, the primary magnetic sensor 12 is continuously arranged at different positions relative to the object 2, and the different positions include at least one position of interest and a nominal position, at the position of interest, the primary magnetic sensor 12 is arranged facing the region of interest of the object 2. As described above, the region of interest corresponds to the region of the object 2 that may have a defect, i.e., the region where potential defects are to be detected. The nominal position corresponds to the position where the primary magnetic sensor 12 is not arranged facing the defect of the object 2. In other words, it is desired that the device 1 is arranged facing the object 2 such that it faces at least one region of interest and at least one defect-free region. Positioned facing at least one defective region so that the nominal magnetic field intensity of the primary signal can be determined in order to be able to detect the variation of the primary signal intensity relative to the nominal intensity. Positioned facing at least one region of interest so that the primary signal can be acquired in order to detect the presence of a defect in that region of interest.

[0138] The method includes step d) of detecting in the primary signal a signal feature indicative of a positioning defect of the metal cord 20 of the object 2. Step d) is preferably implemented by a processing unit. Step d) preferably includes the processing unit analyzing and processing the primary signal.

[0139] Preferably, step d) includes processing of the primary signal, which processing includes subtracting the secondary signal received by the secondary magnetic sensor 16 from the primary signal received by the primary magnetic sensor 12. This makes it possible to purify the primary signal by subtracting from the primary signal the variation in the magnetic field strength associated with the background magnetic field.

[0140] Step d) may include different processing operations to facilitate the analysis of the primary signal. Thus, step d) may include, for example, at least one of the following processing operations: filtering with a low-pass filter, calculating the absolute value of the signal, normalizing, and thresholding. These different operations may, for example, eliminate background noise or flatten the signal, thus making the signal clearer and easier to interpret. Combinations of these operations may also be implemented to process the primary signal.

[0141] The signal feature indicative of a positioning defect of the metal cord of the object is a local extremum of the primary signal. The local extremum corresponds to a local maximum of the primary signal greater than a first threshold or to a local minimum of the primary signal less than a second threshold. For example, showing the primary signal (i.e., the variation over time of the magnetic field strength measured by the primary magnetic sensor 12) Figure 11 shows a local extremum E1 corresponding to a local maximum of the primary signal. The first threshold and the second threshold are defined relative to the nominal signal. For example, the measured magnetic field strength corresponding to the first threshold may correspond to a strength that is a specific difference greater than the nominal strength. Similarly, for example, the measured magnetic field strength corresponding to the second threshold may correspond to a strength that is a specific difference less than the nominal strength. It should be understood that the first threshold is greater than the nominal strength and the second threshold is less than the nominal strength.

[0142] The presence of a local extremum indicates a variation between the magnetic field strength of the primary signal and the nominal strength (i.e., the magnetic field strength of the primary signal corresponding to the magnetic field generator 10 being set without defects facing the object 2). This indicates a deformation of the inspection magnetic field. A deformation of the inspection magnetic field indicates a potential defect of the object 2.

[0143] Advantageously, if it is determined that there is a local extremum and if the magnetic field strength of this local extremum is greater than the first threshold, it can be determined that there is a defect corresponding to the overlap of two metal cords 20. However, if it is determined that there is a local extremum and if the magnetic field strength of this local extremum is less than the second threshold, it can be determined that there is a defect corresponding to a gap greater than the nominal gap between two consecutive metal cords 20.

[0144] According to a particular embodiment, the absolute value of the magnetic field strength of the primary signal (it can be considered that a process for calculating the absolute value of the signal is implemented) is utilized, which can facilitate the analysis of the primary signal. In this case, it can be understood that all values of the processed primary signal are positive values.

[0145] If a defect is detected, various measures can be taken. For example, the object 2 can be properly replaced or modified to eliminate the defect.

[0146] The present invention is not limited to the embodiments described and illustrated in the drawings. Modifications can be made without departing from the overall scope of the present invention, particularly in terms of the composition of various technical features, or by substituting technical equivalents.

Claims

1. A detection device (1) for detecting a positioning defect of one of a plurality of metal cords (20) relative to another of the plurality of metal cords (20) in an object (2) comprising a plurality of metal cords (20), the object (2) being, for example, a reinforcing ply comprising a plurality of reinforcing metal cords (20) embedded in a rubber-based matrix (21), the device (1) comprising: - A magnetic field generator (10), preferably composed of a magnet or a coil, arranged to generate a magnetic field called the "inspection magnetic field", and positioned facing the object (2) such that the plurality of metal cords (20) cause deformation of the inspection magnetic field. - A magnetic sensor (12) called a "primary magnetic sensor", arranged to measure the intensity of the inspection magnetic field. The device (1) is characterized in that the inspection magnetic field has at least one neutral point where the intensity of the inspection magnetic field is zero before being deformed by the plurality of metal cords (20). And the primary magnetic sensor (12) is arranged relative to the magnetic field generator (10) at a selected position corresponding to the position of the neutral point.

2. The device (1) according to claim 1, characterized in that, The device (1) comprises a support (14) called a "primary support", which supports the magnetic field generator (10) and the primary magnetic sensor (12), and is equipped with an adjustment system (143) that can adjust the position of the primary magnetic sensor (12) relative to the magnetic field generator (10), for example by tightening, to reach the selected position and hold the primary magnetic sensor (12) in the selected position fixed relative to the magnetic field generator (10).

3. The device (1) according to claim 2, characterized in that, The magnetic field generator (10) has an annular shape centered on an axis (A) called the "central axis of the generator" and defines a free internal space (101), and the adjustment system (143) comprises a support portion (142) that supports the primary magnetic sensor (12) and engages in the free internal space (101) such that the primary magnetic sensor (12) can move along the central axis (A) of the generator to change the position of the primary magnetic sensor (12) along the central axis (A) of the generator.

4. The device (1) according to any one of the preceding claims, characterized in that, The device (1) comprises at least one stabilizing element (18), such as a roller, that can come into contact with the object (2) to maintain a constant distance between the primary magnetic sensor (12) and the outer surface (22) of the object (2).

5. The device (1) according to claim 4, characterized in that, The device (1) comprises at least one suspension mechanism (19), such as a spring, that can elastically press the stabilizing element (18) against the object (2).

6. The device (1) according to one of the preceding claims, characterized in that, The device (1) comprises a secondary magnetic sensor (16) separated from the primary magnetic sensor (12), which is not subjected to the inspection magnetic field and is arranged facing a region of the object (2) to measure the intensity of a magnetic field called the "background magnetic field", which represents the magnetic field prevailing in the object (2) in the absence of the inspection magnetic field.

7. The device (1) according to claim 6, characterized in that, The device (1) comprises a sub - assembly (13) which forms a set of three carriages (130a, 130b, 130c), the three carriages (130a, 130b, 130c) being arranged in a row in a direction (D) called the "longitudinal direction", and being hinged pairwise to each other such that the three carriages (130a, 130b, 130c) can conform to the outer surface (22) of an object (2), each carriage being supported on the outer surface (22) so as to provide at least three corresponding separate support areas in the longitudinal direction (D). The carriages (130a, 130b, 130c) respectively consist of: - A primary carriage (130a) which supports a magnetic - field generator (10) and a primary magnetic sensor (12) and at least one primary stabilizing element (18a), preferably a primary roller, the axis of rotation (Xa) of the at least one primary stabilizing element (18a) being perpendicular to the longitudinal direction (D), which enables the primary carriage (130a) to roll on the outer surface (22) of the object (2) while keeping the magnetic - field generator (10) and the primary magnetic sensor (12) at a predetermined constant distance from the outer surface (22). - A secondary carriage (130b) which supports a secondary magnetic sensor (16) and at least one secondary stabilizing element (18b), preferably a secondary roller, the axis of rotation (Xb) of the at least one secondary stabilizing element (18b) being perpendicular to the longitudinal direction (D), which enables the secondary carriage (130b) to roll on the outer surface (22) while keeping the secondary magnetic sensor (16) at a predetermined constant distance from the outer surface (22). - A third carriage (130c) which supports at least one third stabilizing element (18c), preferably a third roller, the axis of rotation (Xc) of the at least one third stabilizing element (18c) being perpendicular to the longitudinal direction (D), which enables the third carriage to roll on the outer surface (22) of the object (2).

8. A detection component, characterized in that, It comprises a detection device (1) and a drive system according to any one of claims 6 and 7, the drive system enabling the outer surface (22) of the object (2) to make a relative travel movement with respect to the magnetic - field generator (10) and the primary magnetic sensor (12) in a predetermined direction (B) called the "scanning direction", and the secondary magnetic sensor (16) being arranged ahead of the primary magnetic sensor (12) with respect to the scanning direction (B) such that the same area of the outer surface (22) of the object (2) is successively covered by the secondary magnetic sensor (16) measuring the background magnetic field and then by the primary magnetic sensor (12) measuring the inspection magnetic field deformed by the multiple metal cords (20) of the object (2).

9. A method for detecting a positioning defect of one of a plurality of metal cords (20) relative to another of the plurality of metal cords (20) in an object (2) comprising a plurality of metal cords (20), said object (2) being, for example, a reinforcing ply comprising a plurality of reinforcing metal cords (20) embedded in a rubber-based matrix (21), the method comprising the following steps: a) Providing a magnetic field generator (10) and a primary magnetic sensor (12) to form a detection device (1), the primary magnetic sensor (12) being arranged relative to the magnetic field generator (10) at a selected position corresponding to the position of a neutral point, the neutral point corresponding to the point at which the intensity of the inspection magnetic field generated by the magnetic field generator (10) is zero before being deformed by the plurality of metal cords (20); b) Positioning the detection device (1) relative to the object (2) such that the magnetic field generator (10) and the primary magnetic sensor (12) are arranged facing the object (2); c) Moving the detection device (1) relative to the object (2) and continuously acquiring a primary signal received by the primary magnetic sensor (12); d) Detecting, in the primary signal, a signal feature indicative of a positioning defect of the metal cords of the object (2).

10. The method according to claim 9, wherein, Step a) includes step a0): Adjusting the detection device (1) by positioning the primary magnetic sensor (12) relative to the magnetic field generator (10) at the selected position.

11. The method according to claim 10, wherein, In step a0), the primary magnetic sensor (12) is positioned using an adjustment system (143) which is capable of adjusting the position of the primary magnetic sensor (12) relative to the magnetic field generator (10), for example by tightening, and holding the primary magnetic sensor (12) in the selected position fixed relative to the magnetic field generator (10), the adjustment system (143) being included in a support (14) called a "primary support", said support (14) supporting the magnetic field generator (10) and the primary magnetic sensor (12) and being provided with the adjustment system (143).

12. The method according to claim 11, wherein, The magnetic field generator (10) has an annular shape centered on an axis (A) called the "central axis of the generator" and defines a free internal space (101), the adjustment system (143) including a support portion (142) which supports the primary magnetic sensor (12) and engages in the free internal space (101), and wherein, in step a0), the support portion (142) supporting the primary magnetic sensor (12) moves along the central axis (A) of the generator to change the position of the primary magnetic sensor (12) along the central axis (A) of the generator.

13. The method according to any one of claims 9 to 12, wherein, In step b), at least one stabilizing element (18), such as a roller, is provided in contact with the object (2) to maintain a constant distance between the primary magnetic sensor (12) and the outer surface (22) of the object (2).

14. The method according to claim 13, wherein In step b), the stabilizing element (18) is elastically pressed against the object (2) by a suspension mechanism (19), such as a spring.

15. The method according to any one of claims 9 to 14, wherein, In step c), the detection device (1) moves relative to the object (2), such that the primary magnetic sensor (12) is successively placed at different positions relative to the object (2), said different positions including at least one position of interest and a nominal position, at said position of interest, the magnetic sensor is placed facing an area of interest of the object (2) where potential defects are to be detected, and at said nominal position, the magnetic sensor is placed facing an area of the object (2) that is free of defects and is different from the area of interest, so as to measure the nominal magnetic field strength of the primary signal.

16. The method according to claim 15, wherein, The signal feature indicating a positioning defect of the metal cord of the object (2) is a local extremum relative to the nominal magnetic field strength, and the local extremum (E1) has a magnetic field strength greater than a first threshold or less than a second threshold.

17. The method according to claim 16, wherein, In step d), if it is determined that there is a local extremum, and if the extremum has a magnetic field strength greater than the first threshold, it is determined that there is a defect corresponding to the overlap of two metal cords (20), and if the extremum has a magnetic field strength less than the second threshold, it is determined that there is a defect corresponding to a gap greater than the nominal gap between two consecutive metal cords (20).

18. The method according to any one of claims 9 to 17, comprising a step of acquiring a secondary signal prior to acquiring the primary signal, the secondary signal corresponding to a change during a movement of a magnetic field called a "background magnetic field" which represents the magnetic field prevailing in the object (2) in the absence of an examination magnetic field, and wherein, Step d) includes processing the primary signal by subtracting the secondary signal from the primary signal.

19. The method according to claim 18, wherein The previous step of acquiring the secondary signal is implemented by the secondary magnetic sensor (16), which is separated from the primary magnetic sensor (12) and is not subjected to the inspection magnetic field. In the previous step of implementing the acquisition of the secondary signal, the secondary magnetic sensor is placed facing an area of the object (2).

20. The method according to claim 19, wherein In step b), the subassembly (13) is placed in contact with the outer surface (22) of the object (2). The subassembly (13) forms a set of three carriages (130a, 130b, 130c), and said three carriages (130a, 130b, 130c) are arranged in a row in a direction (D) called the "longitudinal direction" and are hinged pairwise to each other, such that the three carriages (130a, 130b, 130c) can conform to the outer surface (22) of the object (2). Each carriage is supported on the outer surface (22) so as to provide at least three corresponding individual support areas in the longitudinal direction (D). The carriages (130a, 130b, 130c) respectively consist of: - The primary carriage (130a), which supports the magnetic field generator (10) and the primary magnetic sensor (12) and preferably at least one primary stabilizing element (18a) that is a primary roller. The axis of rotation (Xa) of the at least one primary stabilizing element (18a) is perpendicular to the longitudinal direction (D), which enables the primary carriage (130a) to roll on the outer surface (22) of the object (2) while maintaining the magnetic field generator (10) and the primary magnetic sensor (12) at a predetermined constant distance from the outer surface (22). - A secondary carriage (130b) that supports a secondary magnetic sensor (16) and at least one secondary stabilizing element (18b), preferably a secondary roller, the axis of rotation (Xb) of the at least one secondary stabilizing element (18b) being perpendicular to the longitudinal direction (D), which enables the secondary carriage (130b) to roll on the outer surface (22) while maintaining the secondary magnetic sensor (16) at a predetermined constant distance from the outer surface (22). - A third carriage (130c) that supports at least one third stabilizing element (18c), preferably a third roller, the axis of rotation (Xc) of the at least one third stabilizing element (18c) being perpendicular to the longitudinal direction (D), which enables the third carriage (130c) to roll on the outer surface (22) of the object (2). Wherein, in order to implement the previous step of obtaining the secondary signal and step c) of moving the detection device (1) relative to the object (2) and continuously obtaining the primary signal received by the primary magnetic sensor (12), the carriages (130a, 130b, 130c) roll on the outer surface (22) of the object (2) such that the same area of the object (2) first faces the primary carriage (130a), then the secondary carriage (130b), and finally the third carriage (130c).

21. The method according to any one of claims 9 to 20, wherein, Step d) includes processing of the primary signal, the processing including at least one of the following processing operations: filtering with a low-pass filter, calculating the absolute value of the signal, normalizing, thresholding, and combinations of these processing operations.

22. The method according to any one of claims 9 to 21, the method being implemented to detect a positioning defect of one of the metal cords (20) relative to another of the metal cords (20) in a reinforcing ply that includes metal cords (20) extending not parallel to the edges of the reinforcing ply.

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