Device for measuring the thickness of the remaining rubber of an identified tire during retreading using an electromagnetic jet.

Abstract

The invention relates to a system that implements an inspection process for an identified tire during retreading, characterized in that the system comprises a thickness measurement device (100) including an electromagnetic jet (106) incorporating a horn antenna (106a) extended by a cylinder including a cylindrical tip (106b). The invention also relates to an inspection process for an identified tire during retreading, the inspection process implemented by the disclosed system. The invention further relates to a retreading method including the inspection process implemented by the disclosed system. Figure for the abstract: Fig. 5

Description

Title of the invention: Device for measuring the thickness of the remaining rubber of an identified tire during retreading using an electromagnetic jet. Technical field

[0001] The invention relates to a device for measuring the thickness by electromagnetic jet of the remaining rubber of an identified tire during retreading. Context

[0002] In industrial sectors (such as tire retreading), the measurement and characterization of materials are routinely carried out in manufacturing and quality control workshops. In the context of their use, it is often necessary to find new technological approaches to accurately measure spatial distances and to measure the layer thickness of a section of a tire intended for retreading.

[0003] Several technologies have already been tested or developed to determine the thickness of a material (either a material to be removed or a material intended for inclusion in a product during manufacturing). For example, there are magnetic sensors that use eddy currents, but these do not allow for precise distance measurements because the thickness is averaged over the entire surface of the sensor (the deeper the penetration into the material, the larger the sensor must be). For a system using this type of technology, the spatial resolution is low (due to the size of the sensor), and therefore the system cannot handle significant curvature of an object.

[0004] Ultrasonic measurements also exist, which require a coupling to perform the measurement. Data interpretation is often difficult, and accuracy can be low.

[0005] In addition, there is thermography which requires direct heating (for example, by an infrared lamp) or indirect heating (for example, by induction) of the product being measured, which implies a significant consumption of energy.

[0006] There are also traditional wave sensors whose thickness measurement is carried out by Terahertz wave (for example, as disclosed by the Applicant's patent FR3117210).

[0007] Other technologies based on optical technologies have been systematically ruled out since they do not penetrate or penetrate opaque materials very little.

[0008] Among the measurement methods commonly used to characterize the properties of materials are waveguide and free-space techniques in the microwave range. Although these methods are reliable and efficient, they have some Disadvantages: Measurements in waveguides are destructive, and measurements in free space require a large, often flat, sample. Furthermore, the "traditional" systems that implement these long-established methods have characteristics directly dependent on the wavelength used, including: - A spatial resolution power dependent on the diffraction limit defined by the Rayleigh criterion, i.e. approximately X / 2. - The ability to discriminate and characterize (e.g., thickness...) materials depends on the frequency band used. The wider the frequency band, the more precise the characterization. - Restricted penetration into materials, induced by the dispersion of the emission power on the wavefront.

[0009] To overcome these limitations, the electromagnetic jet concept was introduced as a method for local free-space characterization (see Ghaddar, Ali et al. “Electromagnetic Jet Towards Characterization Applications,” 17th Microwave and Materials Characterization Days, https: / / hal.science / hal-04059278 (April 2023) (“Ghaddar reference”)). The electromagnetic jet is derived from the photonic jet concept where a dielectric sphere, illuminated by a near-field wave, can focus fundamentally into a beam whose width is narrower than the diffraction limit (see Ghaddar reference 1) (citing Chen, Zhigang and Taflove, Allen, “Photonic nanojet enhancement of backscattering of light by nanoparticles: a potential novel visible-light ultramicroscopy technique,” ​​Opt. Express, vol. 12, no. 7, p. 1214, doi: 10.1364 / OPEX. 12.001214 (2004) ("the Chen reference").Ghaddar observes that "this beam has a high intensity and propagates over several wavelengths in the form of a quasi-plane wave," and therefore the photonic jet has been widely studied and applied in industry and laboratory tools.

[0010] With reference to [Fig. 1] (which corresponds to [Fig. 1] of the Ghaddar reference), an electromagnetic beam 10 is designed to study the electromagnetic response of a simple material composed of a substrate with a ground plane on the back face. The electromagnetic response of multilayer systems with different refractive indices can be treated analytically using Maxwell's equations (it is known that Maxwell's equations describe the propagation of electromagnetic waves in any type of medium).

[0011] By way of example, the electromagnetic jet 10 comprises a horn antenna (or "antenna") 10a loaded with polytetrafluoroethylene (or "PTFE"). The horn antenna 10a extends along a predetermined height H defined between a predetermined minimum diameter d and a predetermined maximum diameter D. The horn antenna 10a is extended by a cylinder also made of PTFE. This cylinder includes a cylindrical tip 10b of predetermined height h and predetermined radius R at the antenna outlet. The cylindrical tip 10b forms a transient part at the antenna input, minimizing reflections due to the change in medium (air / PTFE).

[0012] An electromagnetic wave encounters two different media at the exit of the horn antenna 10a: the cylindrical tip 10b of the PTFE in the center, surrounded by air at the ends. The portion of the wave traveling through the air has a faster propagation speed than the portion of the wave propagating through the PTFE. The wavefront at the exit of the horn antenna has a concave shape, and the wave takes on a convex shape at the tip after passing through it (this deformation is explained by the difference in propagation speed between the air and the PTFE). Subsequently, Fonde refraction towards the air amplifies the convexity of the wave, resulting in a more intense spot at the tip 5 mm from its end. Thus, the difference in propagation speed between the air and the PTFE is the cause of the focusing phenomenon of the electromagnetic jet 10.The focused wave exhibits a significant field concentration and appears to be less distorted, to the point that it can be considered approximately planar.

[0013] It is understood that the cylindrical tip 10b of the electromagnetic jet 10 is not limited to the geometry shown in [Fig. 1]. For example, the cylindrical tip 10b could be replaced by two or more concentric cylinders, by an elongated rectangular tip, or by another geometry that functions as equivalent to the cylindrical tip 10a.

[0014] Thus, it is appreciated that there is good agreement between the response of a material detected by an electromagnetic beam such as that shown in [Fig. 1] and a theoretical response of that material when illuminated by a plane wave. By using this type of beam focused near or below the diffraction limit, the electromagnetic beam makes it possible to offer new measurement systems in industry, including in the microwave and terahertz ranges. This method, which performs localized measurements in free space without damage, has favorable characteristics, including, but not limited to: - Stronger penetration into carbonaceous materials compared to conventional methods; - Increased spatial accuracy (X / 10 minimum instead of X / 2 with conventional systems); - A very localized and homogeneous focus; - Very good detection and discrimination of materials; and - A possibility of characterizing metallic oxidation.

[0015] In the field of tire manufacturing and maintenance, retreading is a process known for restoring a worn tire to working order by renewing the tread rubber and the ply(ies). During the retreading process, the old tread materials are removed and replaced with new materials. Referring to [Fig. 2], when retreading a tire identified as P, the worn carcass is "carded" (see the "Carded Area" of [Fig. 2]), that is, an attempt is made to remove as much of the remaining tread thickness as possible (see the "Uncarded Worn Area" of [Fig. 2]) and to leave the minimum amount of rubber above the first ply N (being a metallic and / or textile and / or other material ply known in the field of tires).

[0016] The electromagnetic jet concept has recently seen increasing progress due to its applications in detection and imaging, ranging from the optical domain to microwave frequencies. Thus, the disclosed invention employs an innovative electromagnetic jet sensor that enables near-field detection and / or measurement, allowing for the measurement of remaining tread thickness while maintaining good spatial accuracy during the retreading of an identified tire. Summary of the invention

[0017] The invention relates to a system that implements an inspection process for an identified tire during retreading, characterized in that the system comprises: - a thickness measurement device comprising an electromagnetic jet incorporating a horn antenna which extends along a predetermined height defined between a predetermined minimum diameter and a predetermined maximum diameter, the horn antenna being extended by a cylinder comprising a cylindrical tip having a predetermined height and a predetermined radius at the exit of the antenna; - a means of generating signals in a predetermined frequency band, the emitted frequency band of which is chosen according to the properties of the identified tire; and a communication network that manages incoming data to the system from the measuring device, the communication network incorporating one or more communication servers each comprising one or more processors operationally connected to a memory configured to store an application for analyzing data representative of the tires identified to be inspected, the processor(s) comprising an analysis application execution module that performs data processing, whose processor(s) are capable of executing programmed instructions stored in memory to implement the steps of the inspection process.

[0018] In one embodiment of the system of the invention, the electromagnetic jet of the measuring device is made of polytetrafluoroethylene.

[0019] In one embodiment of the system of the invention, the measuring device comprises a robot having a measuring device supported by a pivoting elongated arm, the measuring device extending from the elongated arm to a free end which allows the installation of the electromagnetic jet; so that the measuring device is fixed in such a way as to allow its rotation relative to the free end and also to allow its spinning around a predefined axis of rotation during the inspection process.

[0020] In one embodiment of the system of the invention, the means for generating signals from the measuring device includes a synthesizer disposed at the free end of the measuring device.

[0021] In one embodiment of the system of the invention, the frequency band emitted by the means for generating signals is between 20 and 40 GHz inclusive.

[0022] In one embodiment of the system of the invention, the electromagnetic jet has a variable resolution depending on the contrast of the materials from / . / 10 to / . / 100.

[0023] In one embodiment of the system of the invention, the system further comprises a vector network analyzer (VNA).

[0024] The invention also relates to an inspection process for an identified tire during retreading, the inspection process implemented by the disclosed system, characterized in that the inspection process includes the following steps; - a first step in which the measurement device employs at least one of a frequency domain spectroscopy - cavity resonance (FDS-CR) method and a time domain spectroscopy - cavity resonance (TDS-CR) method, this step including a step of calculating a fast Fourier transform (FFT); - a second step in which the spectrum determined in the first step is divided by a reference spectrum, such that: - where the wavelength is a submultiple of the thickness, the wave enters into exact resonance with the substrate, and the return signal of the wave is at its minimum; - a third step of performing an Inverse Fourier Transform (iFFT) before specific signal processing, so that the signal processing is carried out in the time domain; - a fourth signal processing step including a thickness calculation according to the following expression: [Math 2]

[0025] Where: - e; represents the thickness of a layer i; - c represents the speed of light; - Δt represents the propagation delay between two interfaces representing an input interface and an output interface of layer i; and - n'i represents the real part of the refractive index of the material of layer i; - and a final step including a calculation step of a fast Fourier transform (FFT) performed on the cleaned signal; so that, at the end of the inspection process, the processed frequency transfer function is obtained.

[0026] In one embodiment of the inspection process of the invention, the fourth step of the inspection process comprises: - a step to obtain the refractive index of a part of the identified tire, where the refractive index is represented according to the following expression: [Math 3] n = n'+in"where: n' represents the real part of the complex refractive index related to the wave propagation speed; and - n” represents the imaginary part of the complex refractive index related to the absorption of the wave; - and a step to determine the behavior of the wave through the materials it passes through, in which the angle of the refracted wave is governed by the following expression: [Math 4] t^sin#! = ;where: - ni represents the refractive index of a first substrate; and - n2 represents the refractive index of a second substrate.

[0027] In one embodiment of the inspection process of the invention, the fourth step of the inspection process further includes a step to determine the refractive index of the identified tire parts for a given frequency band according to the following expression:

[0028] [Math.5] ni = 2^f Or : - ej represents the thickness of layer i; - c represents the speed of light; - Df represents the frequency difference between two successive resonances; and - n; represents the refractive index of the material in layer i.

[0029] In one embodiment of the inspection process of the invention, during the fourth stage of the inspection process, each interface in the time domain generates Gaussians which are discriminated in the form of the center of the Gaussians.

[0030] The invention further relates to a retreading process comprising the disclosed inspection process.

[0031] In one embodiment of the retreading process of the invention, the retreading process further comprises at least one of the following steps: - a step involving positioning an identified tire within a processing area where the inspection device processes it; and - a step in carrying out a tire repair process identified using at least one suitable processing tool.

[0032] Other aspects of the invention will become evident from the following detailed description. Brief description of the drawings

[0033] The nature and various advantages of the invention will become more evident upon reading the following detailed description, together with the accompanying drawings, in which the same reference numbers designate identical parts throughout, and in which: [Fig.1] Fig.1 represents an embodiment of an electromagnetic jet used by the invention. [Fig.2] Fig.2 represents a schematic view of a tire during retreading having carded and non-carded areas. [Fig.3] The [Fig.3] represents a schematic view demonstrating a link between A / and A / . [Fig.4] Fig.4 represents a schematic view of an electromagnetic wave and the relationship between its frequency and the round-trip propagation time. [Fig.5] Fig.5 represents an embodiment of a measuring device of the invention which implements a process for inspecting the tire(s) identified during retreading. [Fig.6] Fig.6 represents a comparison of the spatial resolution obtained during detection as a function of the type of horn antenna used. [Fig.7] Fig.7 represents a schematic view of a simulation in which the plane wave is very localized and focused at the output of a perturbator. [Fig.8] Fig.8 represents a flow diagram of an inspection process implemented by the measuring device of the invention during a retreading process. [Fig.9] [Fig. 10] Fig.9 and Fig. 10 represent diopters representing interfaces between two layers of a substrate. [Fig. 11] The [Fig. 11] represents resonance points that correspond to different frequencies or wavelengths in a substrate. [Fig. 12] [Fig. 12] represents a ratio between the refractive indices of the substrates.

[0034] [Fig. 13] [Fig. 13] represents a schematic cross-sectional view of a method of manufacturing a known tire. [Fig. 14] The [Fig. 14] represents a uniform focal width of an electromagnetic jet used by the measuring device of the [Fig.5] with respect to an identified tire. Detailed description

[0035] To understand the measurement system of the invention and the use of the electromagnetic jet, it is helpful to introduce the underlying theoretical study. It is understood that electromagnetic phenomena are represented using the electric field (E) and the magnetic field (H), which are two vector physical quantities. The intrinsic properties of a medium are represented by the electrical permittivity (e), electrical conductivity, magnetic permeability (p), and magnetic losses (p'). Electrical conductivity and magnetic loss characterize the capacity of a medium to absorb the electrical and magnetic energy of a wave propagating through that medium (see Gazave, Julien, "Contribution to the implementation of numerical simulation methods for studying the vulnerability of electrical systems subjected to the radiative and electromagnetic environment of the Laser Mégajoule," Thesis No. 70-2007, University of Limoges (2007)).

[0036] In the frequency domain, the inventors observed that the reflection coefficient exhibits an alternation of constructive and destructive resonances. Considering that the frequency difference A / between two successive resonances corresponds to the time A / for the wave to propagate back and forth in a substrate (i.e., a "medium"), [Fig. 3] represents a diagram to demonstrate this relationship between A / and A / . [Fig. 3] illustrates the penetration of an electromagnetic wave (or "EM wave") onto the upper surface of a substrate at time t, the arrival of the EM wave at the lower surface at time t + At / 2, and the return of the EM wave to the upper surface at time t + A / . The interference observed on the reflection spectrum corresponds to the result of the superposition of the incident wave and the wave that has returned to the upper surface after being reflected from the lower surface.

[0037] On this basis, the thickness of a sample can be detected from the reflection coefficient in the frequency domain. Figure 4 shows the diagram of an EM wave and the relationship between its frequency and the round-trip propagation time. The Fourier transform allows the signal to be converted from the time domain to the frequency domain (or vice versa): [Math 1] / af^c / \ j^where the signal F(°') is the reflection coefficient of the EM wave measured in frequency sweep (°! represents the frequency pulsation of the EM wave).

[0038] To study this basic conversion from frequency domain to time domain, the inventors consider a signal representing the reflection coefficient of a substrate, calculated analytically from Maxwell's equations.

[0039] To study this basic conversion from frequency domain to time domain, the inventors consider a signal representing the reflection coefficient of a substrate, calculated analytically from Maxwell's equations.

[0040] With further reference to the figures, in which the same numbers identify identical elements, [Fig. 5] represents an embodiment of a measuring device (or "device") 100 of the invention. The measuring device 100 may be part of a retreading system (or "system") in which an inspection process is carried out during the retreading of one or more tires. The measuring device 100 of the invention implements such an inspection process, enabling the measurement, by electromagnetic jet, of the thickness of a tire (and / or a portion of a tire) during retreading.

[0041] In one embodiment of the measuring device 100 of the invention, the measuring device 100 comprises a robot having a measuring peripheral 102 supported by a pivoting elongated arm 104. The measuring peripheral 102 extends from the elongated arm 104 to a free end 102a which allows the installation of an electromagnetic jet 106. The electromagnetic jet 106, being of the type shown in [Fig. 1], comprises a horn antenna 106a and a cylindrical tip 106b, both made of PTFE. The measuring device 106 is mounted in such a way as to allow its rotation about the longitudinal axis and also to allow its rotation around a predefined axis of rotation during an inspection process. As an example, the attachment of the electromagnetic jet 106 to the measuring device 102 can be achieved by screwing an adapter onto the free end 102a of the measuring device.It is understood that the attachment of the electromagnetic jet 106 to the measuring device 102 can be achieved by one or more known attachment methods (including, without limitation, welding, bonding, and equivalent methods). Thus, the robot facilitates the inspection of a variety of tires without interrupting the rotation and / or movement of the electromagnetic jet 106.

[0042] The measuring device 100 is set in motion so that the measuring device 102 can perform the inspection of an identified tire during retreading. The term "identified tire" (in the singular or plural) is used here to refer to a tire being retreaded and present in the physical environment of the system incorporating the measuring device 100 (the physical environment being, for example, a retreading facility incorporating the measuring device 100).

[0043] It is understood that the configuration of the measuring device 100 is given by way of example. For example, the measuring device 100 may include a fixed robot installed in a manufacturing facility, attached, for example, to a support from which the robot extends (for example, a base not shown). In this case, it is understood that the robot may be attached to a ceiling, a wall, a floor, or any support that allows the inspection process to be carried out. It is understood that the measuring device 100 may include at least one mobile robot. By "mobile," it is understood that the measuring device may be set in motion either by integrated means of motion (for example, one or more integrated motors) or by non-integrated means of motion (for example, one or more mobile means, including autonomous mobile means).It is understood that the measuring device 100 can be a conventional industrial robot, a collaborative robot, or even a delta or cable robot.

[0044] Referring again to [Fig. 5], the measuring device 100 further includes a means for generating signals in a predetermined frequency band. By way of example, the measuring device 100 includes a synthesizer 108 disposed at the free end 102a of the measuring device 102. It is understood that the frequency band emitted by the synthesizer 108 is chosen according to the characteristics of the tires intended for an inspection process. In one embodiment, the chosen frequency band is between 20 and 40 GHz inclusive.

[0045] The use of the electromagnetic jet 106 allows for precise control of the width and length of a plane wave pocket thanks to the design of a dielectric perturbator. Thus, the small width of the electromagnetic jet 106 (given the major diameter D of the cylindrical nozzle 106b) makes it possible to focus the measurement on a very small area. This property allows for a unique spatial resolution (as described below). Furthermore, the width of the electromagnetic jet 106 is "straight" and "stable" along the length of a useful inspection area, which makes the spatial resolution homogeneous over a distance of a few wavelengths. The combination of these characteristics, as well as the refraction properties implemented by the electromagnetic jet 106, promotes the concentration of the plane wave intensity in the useful area. Once past the useful area, the wave diverges again in the form of spherical waves.The electromagnetic jet maintains a uniform focal width, thus ensuring consistent accuracy. Concentrating the wave intensity in the useful area allows for better penetration of absorbing materials.

[0046] The incorporation of the electromagnetic jet makes it possible to lower the detection limit below the conventional diffraction limit (being on the order of X / 2). Conventionally, the diffraction limit is based on calculations for standard optical systems. Most often, the Rayleigh criterion is used as a reference. This technique cannot be applied to electromagnetic jets, so another method of comparison between different systems must be found. In this case, known methods associated with the FWHM (or "Full Width at Half Maximum") of the main lobe of the Airy disk generated by the analyzed system are used.

[0047] To perform an inter-system comparison independently of wavelength (or operating frequency), a dimensionless ratio denoted d / X is used, where d is the FWHM width and X is the wavelength. By comparing different conventional systems (particularly, the empty horn antenna 6A and the horn antenna equipped with a Fresnel lens 6B) (see [Fig. 6]) with the electromagnetic jet (represented by the horn antenna with the cylindrical tip 6C) (see [Fig. 6]), it is found that the electromagnetic jet allows performance well below the equivalent characteristics compared to the conventional diffraction limit (as shown below in Table 1).

[0048] [Tables 1] @30GHz, i.e., X = 0.00999m » 0.01m FWHM or d (in m) Ratio d / X Empty horn antenna 0.039 3.9 Horn antenna with Fresnel lens 0.012 1.2 Horn antenna with cylindrical tip 0.008 0.8

[0049] The electromagnetic jet has a variable resolution depending on the contrast of the materials from X / 10 to X / 100.

[0050] As can be anticipated, the electromagnetic jet offers the possibility of utilizing the generated plane waves, and consequently, all the common characterization methods associated with plane waves, as well as other methods more specific to the electromagnetic jet. Characterization by electromagnetic jet is performed within the jet's useful zone; currently, it is restricted to the plane wave region. Referring to [Fig. 7], a simulation is shown in which the plane wave is highly localized in a focused area at the perturbator's output (represented in the figure by the "plane wave pocket"). Within a material with a higher refractive index than air (for example, an eraser with n=3.15), the plane wave vector is very pronounced, and the waves are significantly plane. This region forms the basis of all electromagnetic jet-based measurements.Thus, characterization is understood as the determination of one or more properties of a material or a complex structure of different kinds. natures (for example, a multi-layer product that is part of an identified tire).

[0051] It is understood that frequency domain spectroscopy (FDS) and time domain spectroscopy (TDS) are used in all areas of electromagnetic spectroscopy. Consequently, these methods are also applicable to electromagnetic beam spectroscopy. The FDS method, having a long measurement rate, is usable over large thicknesses. The TDS method, having a fast measurement rate, is usable over small thicknesses.

[0052] With reference to Figures 8 to 13, a detailed description is given by way of example of embodiments of an inspection process carried out by the measuring device 100 of the invention. It is understood that a system incorporating the measuring device 100 can implement the process in any physical environment without prior knowledge of the tires to be inspected.

[0053] As used herein, the term “process” or “method” may include one or more steps performed by at least one computer system comprising one or more processors to execute instructions that perform the steps. Unless otherwise indicated, any sequence of steps is given by way of example and does not limit the processes described to any particular sequence.

[0054] By initiating an embodiment of the inspection process that is part of a retreading process, the process includes a first step (see "Step 1" in [Fig. 8]) in which the measuring device 100 employs a frequency domain spectroscopy - cavity resonance (FDS-CR) method and / or a time domain spectroscopy - cavity resonance (TDS-CR) method. Each method is an additive treatment to the conventional FDS or TDS method, which uses standing waves to measure thickness. This approach is therefore based on the frequency domain, unlike conventional FDS and TDS methods, which use the time domain.Using the frequency domain increases the accuracy, dispersion, and stability of the measurement compared to the time domain approach, while having a restricted frequency band with a fine frequency step.

[0055] The first step of the inspection process includes a step of calculating a fast Fourier transform (or "FFT"). This calculation makes it possible to preserve the essential characteristics of the spectra while reducing the volume of calculations to be performed.

[0056] It is observed that when working in conventional TDS or FDS, the process for determining the thickness of a portion of an identified tire remains the same, whether the portion of the identified tire to be inspected is single-layer or multi-layer. The time transfer function resulting from the FDS or TDS (out of a signal processing step of an inspection process implemented by the measuring device 100) (see Step 4 of [Fig.8]) allows obtaining the majority of the data necessary for the thickness calculation in a metric quantity.

[0057] Referring again to [Fig. 8] and further to Figures 9 and 10, in the time domain, a diopter represents an interface between two layers 1 and 2. During the signal processing stage of an inspection process implemented by the measuring device, each interface (or diopter) (1, 2, 3) generates Gaussians that are discriminated in the form of the center of the Gaussians (or "peaks") (see peaks 1, 2, 3 in [Fig. 10]). Various techniques can be used to improve the detection of the Gaussians representing the diopters. This step also allows for improvement of the signal-to-noise ratio through various techniques (including, but not limited to, filtering, windowing, deconvolution, likelihood algorithms, and artificial intelligence on time series).

[0058] This approach is relevant in the case of a thickness measurement system with a conventional THz measuring machine whose frequency band is very wide (for example, 110-170 GHz or 220-330 GHz) and the measurement step is large (for example, 151 measurements over this band). In contrast, electromagnetic jet technology makes it possible to use a vector network analyzer (or "VNA") with an extremely fine frequency step (around 1000 measurements over the band) to compensate for the narrow frequency band used (around 20-40 GHz).

[0059] During the use of the frequency domain in the first stage of the inspection process, the phenomenon of standing waves (and, more specifically, the constructive and destructive resonances that occur in a substrate during a frequency scan) allows for maximum utilization of the VNA capabilities (in fine frequency scanning) while minimizing the impact of the narrow usable frequency band with the electromagnetic beam (22-40 GHz). This data is supported by the SI reflection coefficient obtained from the analysis of the quadrupole (samples / substrate) using the VNA. This method uses the same basic principles as Fabry-Perrot interferometers. When the thickness of a substrate is precisely a fraction of a wavelength, the wave resonates with the substrate, and the resonance becomes destructive.During the frequency sweep at the measurement point, the wave penetrates the material and is reflected at each interface (or "diopter").

[0060] The inspection process includes a second step (see "Step 2" in [Fig. 8]) in which the spectrum resulting from Step 1 is divided by the reference spectrum. Referring to [Fig. 11], if the wavelength is a submultiple of the thickness, the wave resonates exactly with the substrate, and the return signal of the wave is at its minimum (low point). If the wavelength is not a submultiple of The thickness, but only a fraction of it, is affected by the substrate's constructive or destructive resonance. Thus, the low points of the curve are the resonance points, corresponding to the different frequencies where the wavelength in the substrate is "synchronized" with the substrate's thickness.

[0061] It is difficult to directly use the frequency domain data from the second stage of the inspection process: they are noisy, thus requiring appropriate signal processing. Therefore, the inspection process includes a third stage (see "Step 3" in [Fig. 8]) of performing an Inverse Fourier Transform (or "iFFT") before specific signal processing (e.g., filtering, windowing, etc.). In this way, the desired signal processing is carried out, for practical reasons, in the time domain. Once the signal has been "cleaned up," it is necessary to return to the frequency domain to take full advantage of this method.

[0062] The inspection process includes a fourth step (see "Step 4" in [Fig. 8]) of signal processing of an inspection process implemented by the measuring device 100. This step includes a thickness calculation that is very similar to that of the time domain. However, this calculation involves a frequency difference A / instead of a time difference A / . The thickness of a layer is calculated as follows: [Math 2] cAf “ 2nt

[0063] Where: - ej represents the thickness of layer i; - c represents the speed of light; - Δt represents the time delay between two interfaces (Δt being the input and output interfaces of the layer); and - n; represents the real part of the refractive index of the material in layer i.

[0064] During this fourth step, to calculate the thickness of a product of an identified tire to be inspected, its refractive index, which is a dimensionless value, must be obtained. In an absorbing medium, the refractive index is represented as a complex number: [Math 3] n = n' + m" where: n' represents the real part of the complex refractive index related to the wave propagation speed; and - n” represents the imaginary part of the complex refractive index related to the absorption of the wave.

[0065] The refractive index also allows us to determine the behavior of the wave through the materials it passes through, thanks to Snell's law. Referring to [Fig. 12], a substrate Medium 1 is defined by the refractive index nB and a substrate Medium 2 is defined by the refractive index n2. The reflected wave has the same angle as the incident wave, i.e., 01=02. Thus, the angle of the refracted wave is governed by the following expression: [Math 4] It should be noted that if the incident wave is at the normal (vertical) to Medium 2, it will be reflected on this same normal (and therefore will return to the same point). This is the most favorable case for thickness measurement. The system incorporating measuring device 100 therefore uses a position at the normal to the product being measured.

[0066] If the identified tire components composing the layers are previously characterized (i.e., the complex refractive index of the layers is known), the calculation remains simple and requires only a reflection measurement. It is therefore possible to determine the refractive index of the identified tire components for a given frequency band by creating charts on calibrated materials and using the thickness measurement equation adapted for determining the refractive index:

[0067] [Math.5] neither ~ 2nd,Af Or : - e; represents the thickness of layer i; - c represents the speed of light; - Df represents the frequency difference between two successive resonances; and - n; represents the refractive index of the material of layer i.

[0068] The inspection process includes a final step (see "Step 5" in [Fig. 8]) in which a Fast Fourier Transform (or "FFT") calculation step is repeated on the cleaned signal. At the end of the inspection process (i.e., the "Output" in [Fig. 8]), the processed frequency transfer function is obtained.

[0069] With electromagnetic beaming, the frequency band is limited. However, it is possible to perform a large number of measurement points, and the signal can be cleaned up. In this way, the wave is modified to create an extremely high resolution region that distinguishes the details of the material from a substrate, thus enabling more precise material separation and / or characterization. By performing more measurement points, it becomes possible to detect and clean up the "peaks" to return to the time domain.

[0070] With reference to Figures 13 and 14, the inspection process is applied within the framework of a retreading process that includes the inspection process. When considering the characteristics of a tire to be retreaded, its geometry must be taken into account. A tire is an object with a known geometry, generally comprising several superimposed layers of rubber (or "layers"), as well as a metallic or textile fiber structure constituting a carcass that reinforces the tire's structure. The type of rubber and the type of reinforcement are chosen according to the desired final characteristics. Figure 13 includes a schematic representation of a 200 tire, which typically includes two circumferential beads designed to allow the tire to be attached to a rim. Each bead includes an annular reinforcing bead.The construction of a tire is typically described by a representation of its components in a meridian plane, that is, a plane containing the tire's axis of rotation. The radial, axial, and circumferential directions respectively refer to the directions perpendicular to the tire's axis of rotation, parallel to the tire's axis of rotation, and perpendicular to any meridian plane. The terms "radially," "axially," and "circumferentially" mean, respectively, "along a radial direction," "along the axial direction," and "along a circumferential direction" of the tire. The terms "radially inside" and "radially outside" mean "closer to, or farther from, the tire's axis of rotation, respectively, along a radial direction."

[0071] The tire 200 also includes a tread 202 intended to make contact with a ground via a tread surface 202a. It is reinforced by a reinforcement, or "carcass," which generally comprises a plurality of reinforcing layers, each having a plurality of reinforcing cords embedded in a layer of rubber-based material. More specifically, a crown reinforcement comprises a working reinforcement 204 and a reinforcing reinforcement 206. The working reinforcement 204 has working layers represented by layers 204a and 204b.

[0072] The tire 200 also comprises two sidewalls (one sidewall 208 being shown in [Fig. 13]) and two reinforced ribs 210 with a bead 212. A radial carcass layer 214 extends from one rib to the other, surrounding the bead in a known manner. The tread 202 has reinforcements made up, for example, of superimposed layers having known reinforcing threads. In some embodiments, the tire may include a rubber compound 216 that dissipates static electricity produced during rolling.

[0073] The tread 202 is delimited, in the radial direction, by two circumferential surfaces, the outermost of which is the tread surface 202a and whose innermost radial surface is called the tread depth. The tread depth (or "bottom surface") is defined as the area of ​​the tread surface translated radially inward by a radial distance equal to the tread depth. It is common for this depth to decrease over the outermost axially circumferential portions (called "shoulders") of the tread.

[0074] Furthermore, the tread of a tire is delimited, along the axial direction, by two lateral surfaces. The tread is further constituted by one or more rubber compounds. The term "rubber compound" designates a rubber composition comprising at least one elastomer and a filler.

[0075] To achieve good grip on wet surfaces, cutouts are arranged in the tread 12. A cutout is defined as either a well, a groove, an incision, or a circumferential groove, and forms a space opening onto the tread surface 12a. The performance of a tread pattern must remain sufficiently consistent despite wear to ensure the tire's longevity. Consequently, it is necessary to maintain a certain thickness of rubber material between the bottom face of the cutouts (grooves or grooves) and the reinforcing elements to guarantee the tire's durability. For example, grooves must be wide enough to allow the evacuation of liquid present on the ground surface regardless of the stage of wear of the tread 202.

[0076] Referring to [Fig. 14], an electromagnetic jet 106 maintains a uniform focal width (and therefore uniform accuracy) with respect to a tire P' identified for retreading. The concentration of the Fonde intensity emitted in the useful zone allows for better penetration of the absorbing materials of the tire P'. In this use case, these characteristics make it possible to follow transverse and longitudinal curvatures (for example, at the tire shoulders) as closely as possible to their evolution, and they also make it possible to obtain the same measurement certainty on the product depth as with a convergent wave or an eddy current sensor.

[0077] The tires that can be treated by the inspection device 100 during the retreading process include grooves and furrows (but it is understood that the repair device is also capable of treating "slick" type tires).

[0078] A system of which the inspection device 100 is a part does not require knowledge of the architecture of a tire to control the thickness. Thus, this approach allows retreading plants to adapt to unknown architectures and, consequently, opens up the possibility of precisely retreading several types of tires.

[0079] A retreading process incorporating the inspection process includes other known steps, including: - a step of positioning an identified tire in a processing area where the inspection device 100 processes it; and - a step in carrying out a tire repair process identified using at least one suitable processing tool.

[0080] To properly manage the handling of the measuring device 100 (for example, the handling of the robot and the positioning of the electromagnetic jet 106 as shown in [Fig. 5]), the tires being inspected must be identified. Thus, the detection data could refer to a plurality of representative recordings of the tire positions (and the products incorporated therein) tracked over time. For example, the detection data could include one or more positions from recordings of the positions of a reference point on a portion of an identified tire over time or at defined time intervals; sensor data taken over time; a video stream that has been processed using a computer vision technique; and / or data indicating the operating status of the measuring device 100 over time.In some cases, the detection data may include representative data of one or more continuous movements of the measuring device 100 before it stops to inspect one or more products of a tire identified during an inspection process. The detection system could therefore be configured to generate the movement data of the measuring device 100.

[0081] To implement the computer-based inspection process, an industrial system incorporating the measuring device 100 may include a communication network (or "network") that manages incoming data to the system from various sources (for example, from at least one measuring device 100). The communication network incorporates one or more communication servers (or "servers"), each comprising one or more processors operationally connected to memory. The memory is configured to store an application for analyzing data representative of the tires and products being analyzed. The processor(s) include an analysis application execution module that performs data processing, and the processor(s) are capable of executing programmed instructions stored in memory to implement the steps of the inspection process.

[0082] The incoming data of a system incorporating the measuring device 100 may include general information concerning the identified tire. General information includes stored data concerning the identification of the inspected tire (including, without limitation, its production origin, production date, materials incorporated in its production, and geometric parameters).

[0083] The inspection process may incorporate a machine learning method based on data obtained from the inspected tire. The algorithm used analyzes the tire (and the products incorporated within it) to position and operate the measuring device 100. It is understood that such a process may be part of an existing manufacturing process. One or more neural networks (e.g., one or more CNNs) may be trained with ground truth data generated using sensor data representative of the movement of the measuring device 100, including the positioning of the measuring device 102 and the electromagnetic jet 106.

[0084] The industrial system incorporating the measuring device 100 of the invention (and / or an installation incorporating this system) may include pre-programmed management information. For example, an inspection process setting may be associated with the parameters of the typical physical environments in which the system operates. In embodiments of the invention, the measuring device 100 (and / or an industrial system incorporating this device) may receive voice commands or other audio data representing, for example, an inspection start or stop. A request may be made that includes a request for the current status of an ongoing inspection cycle. A generated response may be represented audibly, visually, tactilely (for example, using a haptic interface), and / or virtually and / or augmented.This response, along with the corresponding data, can be recorded in a neural network.

[0085] For all embodiments of the automatic repair system, a monitoring system could be implemented. At least part of the monitoring system can be provided in a portable device such as a mobile network device (e.g., a mobile phone, a laptop computer, one or more portable network-connected devices (including augmented reality and / or virtual reality devices), wearable network-connected clothing / jewelry, and / or any combination thereof). It is conceivable that detection and comparison steps could be performed iteratively.

[0086] The terms "at least one" and "one or more" are used interchangeably. The ranges presented as being "between a and b" encompass the values ​​"a" and "b".

[0087] Although particular embodiments of the disclosed apparatus have been illustrated and described, it will be understood that various changes, additions, and modifications can be made without departing from the spirit or scope of this disclosure. Therefore, no limitations should be imposed on the scope of the invention described except those set forth in the appended claims.

Claims

Demands

1. A system that implements an inspection process for an identified tire during retreading, characterized in that the system comprises: - a thickness measuring device (100) including an electromagnetic jet (106) incorporating a horn antenna (106a) extending along a predetermined height (H) defined between a predetermined minimum diameter (d) and a predetermined maximum diameter (D), the horn antenna (106a) being extended by a cylinder including a cylindrical tip (106b) having a predetermined height (A) and a predetermined radius (R) at the antenna exit; - a means of generating signals in a predetermined frequency band, the emitted frequency band of which is chosen according to the properties of the identified tire;and a communication network that manages the data entering the system from the measuring device (100), the communication network incorporating one or more communication servers each comprising one or more processors operationally connected to a memory configured to store an application for analyzing data representative of the tires identified to be inspected, the processor(s) comprising an analysis application execution module that performs the data processing, the processor(s) of which are capable of executing programmed instructions stored in memory to implement the steps of the inspection process.

2. The system of claim 1, wherein the electromagnetic jet (106) of the measuring device (100) is made of polytetrafluoroethylene (PTFE).

3. The system of claim 1 or claim 2, wherein the measuring device (100) comprises a robot having a measuring peripheral (102) supported by a pivoting extended arm (104), the measuring peripheral (102) extending from the extended arm (104) to a free end (102a) which allows the installation of the electromagnetic jet (106); such that the fixing of the measuring device (106) is made so as to allow its rotation relative to the free end (102a) and also allowing its spinning around a predefined axis of rotation during the inspection process.

4. The system of claim 2 or claim 3, wherein the means for generating signals from the measuring device (100) comprises a synthesizer (108) disposed at the free end (102a) of the measuring device (102).

5. The system of any one of claims 1 to 4, wherein the frequency band emitted by the means for generating signals is between 20 and 40 GHz inclusive.

6. The system of any one of claims 1 to 5, wherein the electromagnetic jet has a variable resolution depending on the contrast of the materials from X / 10 to / . / 100.

7. The system of any one of claims 1 to 6, further comprising a vector network analyzer (VNA).

8. An inspection process for an identified tire during retreading, the inspection process implemented by the system of any one of claims 1 to 7, characterized in that the inspection process comprises the following steps; - a first step in which the measuring device (100) employs at least one of a frequency-domain spectroscopy-cavity resonance (FDS-CR) method and a time-domain spectroscopy-cavity resonance (TDS-CR) method, this step comprising a step for calculating a fast Fourier transform (FFT); - a second step in which the spectrum determined in the first step is divided by a reference spectrum, such that: - where the wavelength is a submultiple of the thickness, the wave resonates exactly with the substrate, and the return signal of the wave is at its minimum;and - a third step of performing an Inverse Fourier Transform (iFFT) before specific signal processing, so that the signal processing is carried out in the time domain; - a fourth signal processing step including a thickness calculation according to the following expression: cA / Where:; - ej represents the thickness of a layer i; - c represents the speed of light; - Dt represents the propagation delay between two diopters representing an input interface and an output interface of layer i; and - n'i represents the real part of the refractive index of the material of layer i; - and a final step including a calculation step of a fast Fourier transform (FFT) done on the cleaned signal; so that, at the end of the inspection process, the processed frequency transfer function is obtained.

9. The inspection process of claim 8, wherein the fourth stage of the inspection process comprises: - a step to obtain the refractive index of a portion of the identified tire, where the refractive index is represented according to the following expression: n = n' + m' where: n' represents the real part of the complex refractive index related to the wave propagation speed; and - n' represents the imaginary part of the complex refractive index related to the wave absorption; - and a step to determine the behavior of the wave through the materials it passes through, wherein the angle of the refracted wave is governed by the following expression: iSine?! = n2sin#3; where: - ni represents the refractive index of a first substrate; and - n2 represents the refractive index of a second substrate.

10. The inspection process of claim 9, wherein the fourth stage of the inspection process further comprises a step for determining the refractive index of the identified tire parts for a given frequency band according to the following expression: ni = 2^f 0Û ' - ej represents the thickness of layer i;

11.

12.

13. - c represents the speed of light; - Df represents the frequency difference between two successive resonances; and - n; represents the refractive index of the material in layer i. The inspection process of any one of claims 8 to 10, wherein, during the fourth stage of the inspection process, each interface (1, 2, 3) in the time domain generates Gaussians which are discriminated in the form of the center of the Gaussians. A retreading process comprising the inspection process of any one of claims 8 to 11. The retreading process of claim 12 further comprising at least one of the following steps: - a step of positioning an identified tire in a processing space where the inspection device 100 processes it; and - a step of carrying out a repair process for the identified tire using at least one suitable processing tool.

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