System for determining the thickness of a layer of rubber for a tire

{
  "publication_number": "US10113855B2",
  "country": "US",
  "kind": "B2",
  "title": "System for determining the thickness of a layer of rubber for a tire",
  "abstract": "A system for measuring a thickness of a layer of rubber material of a tire includes a sensor. The layer includes a joined face, which is joined to an adjacent metal reinforcement, and a free face, which is in contact with air. The sensor, which measures a distance d between the joined face and the free face, includes a source of a static magnetic field and a sensitive element whose output signal is a function of a level of a local magnetic field. The sensor is positioned in such a way that a magnetic field strength measured by the sensitive element varies when the distance d decreases.",
  "claims": [
    "1. A system for determining a thickness of a layer of rubber material of a tire, in which the layer of rubber material includes a joined face and a free face, the joined face being joined to an adjacent reinforcement made with at least one material having a magnetic permeability greater than a magnetic permeability of air, and the free face being in contact with air, the system comprising: a sensor configured to measure a distance D 1 between the joined face and a portion of the sensor, wherein the sensor includes: a static magnetic-field source, and a sensitive element whose output signal is a function of a level of a local magnetic field, the sensitive element being positioned so that a magnetic-field strength measured by the sensitive element varies when the distance D 1 decreases, wherein the distance D 1 is used to determine the thickness of the layer of rubber material, and wherein (a) the static magnetic-field source includes a first magnetic-field source and a second magnetic-field source with identical poles facing each other on opposite sides of the sensitive element, or (b) the static magnetic-field source includes a ring-shaped magnetic-field source surrounding the sensitive element.",
    "2. The system according to claim 1, wherein the static magnetic-field source includes at least one coil supplied with a direct electrical current.",
    "3. The system according to claim 2, wherein each of the at least one coil surrounds, or is surrounded by, a ferrite.",
    "4. The system according to claim 1, wherein the static magnetic-field source includes at least one permanent magnet.",
    "5. The system according to claim 4, wherein condition (a) is satisfied, and wherein each of the at least one permanent magnet has an axial magnetic field.",
    "6. The system according to claim 1, wherein condition (b) is satisfied.",
    "7. The system according to claim 5, wherein each of the at least one permanent magnet is a straight bar or a U-shaped bar.",
    "8. The system according to claim 6, wherein the static magnetic-field source includes a plurality of permanent magnets having a geometrical shape of a ring, and wherein axes of the permanent magnets are arranged in a plane that extends through a source line and are orientated perpendicularly to the source line.",
    "9. The system according to claim 8, wherein each permanent magnet is associated with a sensitive element positioned on the axis of the permanent magnet.",
    "10. The system according to claim 9, wherein each sensitive element is arranged on a point of the axis of the permanent magnet having a zero magnetic field when the layer of rubber material is absent.",
    "11. The system according to claim 4, wherein condition (a) is satisfied, and wherein the static magnetic-field source includes a plurality of uniaxially magnetized magnets, each of the uniaxially magnetized magnets being positioned radially with respect to the sensitive element such that a same pole orientation faces the sensitive element.",
    "12. The system according to claim 4, wherein condition (a) is satisfied, and wherein the static magnetic-field source includes a plurality of permanent magnets positioned in a source line.",
    "13. The system according to claim 12, wherein each permanent magnet has a north pole and a south pole, wherein the permanent magnets are positioned such that the poles are aligned with the source line, and wherein each pair of adjacent permanent magnets has inverted polarities such that poles having a same polarity face each other.",
    "14. The system according to claim 13, wherein the sensor includes a plurality of sensitive elements, each sensitive element being positioned between two adjacent permanent magnets.",
    "15. The system according to claim 1, wherein the sensitive element is one of: a magnetoresistive sensor, a magnetostrictive sensor, and an eddy current sensor.",
    "16. The system according to claim 1, wherein the system is positioned inside an electrically non-conductive casing made of materials having a magnetic susceptibility equal to zero or to a magnetic susceptibility of air or a vacuum environment.",
    "17. The system according to claim 16, wherein the casing is a portable casing.",
    "18. The system according to claim 16, wherein the casing is structured to be positioned on or embedded in a roadway.",
    "19. The system according to claim 16, further comprising electronic circuitry that determines the thickness of the layer of rubber material based on the distance D 1 and a predetermined distance between the portion of the sensor and an application face of the casing, the application face being structured for contacting the free face of the layer of rubber material.",
    "20. A method for determining a thickness d of a layer of rubber material of a tire, in which the layer of rubber material includes a joined face and a free face, the joined face being joined to an adjacent reinforcement made with at least one material having a magnetic permeability greater than a magnetic permeability of air, and the free face being in contact with air, the method comprising: measuring a distance D 1 between the joined face and a portion of a sensor by utilizing a system that includes: an electrically non-conductive casing made of materials having a magnetic susceptibility equal to zero or to a magnetic susceptibility of air or a vacuum environment, the casing being structured to include an application face for contacting the free face of the layer of rubber material, and the sensor, which is positioned in the casing and arranged to measure the distance D 1, the sensor including: a static magnetic-field source, and a sensitive element whose output signal is a function of a level of a local magnetic field, the sensitive element being positioned so that a magnetic-field strength measured by the sensitive element varies when the distance D 1 decreases; and determining the thickness d of the layer of rubber material based on the distance D 1, a predetermined distance between the portion of the sensor and the application face, and a predetermined dimension of the tire, wherein (a) the static magnetic-field source includes a first magnetic-field source and a second magnetic-field source with identical poles facing each other on opposite sides of the sensitive element, or (b) the static magnetic-field source includes a ring-shaped magnetic-field source surrounding the sensitive element.",
    "21. The method according to claim 20, wherein the layer of rubber material is a layer of remaining rubber material on a tread of the tire.",
    "22. The method according to claim 20, wherein the layer of rubber material is a layer of a sidewall or an internal rubber element of the tire.",
    "23. The method according to claim 20, wherein the determining of the thickness d of the remaining layer is performed by electronic circuitry of the system."
  ],
  "description_excerpt": "The present invention relates to a system for measuring the thickness of a layer of rubber, and more particularly to the measurement of the thickness of remaining rubber on a tread of a tyre.\n\nIn a known way, the tread of a pneumatic tyre, or more simply a tyre, regardless of whether it is to be fitted on a passenger vehicle or a heavy transport vehicle, is provided with a pattern comprising, notably, pattern elements or elementary blocks delimited by various main, longitudinal, transverse or oblique grooves, the elementary blocks also possibly comprising various finer slits or sipes. The grooves form channels intended to discharge the water during running on wet ground, and define the leading edges of the pattern elements.\n\nThe depth of the tread is at a maximum when a tyre is new. This initial depth may vary according to the type of tyre in question, as well as the use for which it is intended; by way of example, “winter” tyres generally have a pattern depth greater than that of “summer” tyres. When the tyre becomes worn, the depth of the elementary blocks of the pattern decreases and the stiffness of these elementary blocks increases. The increase in the stiffness of the elementary pattern blocks causes a reduction in some performance characteristics of the tyre, such as the grip on wet ground. The water discharge capacity also decreases markedly when the depth of the channels in the pattern decreases.\n\nIt is therefore desirable to be able to monitor the development of the wear of the tread of a tyre.",
  "cpc": [
    "G01B 7/26",
    "G01M 17/02"
  ],
  "ipc": [
    "G01B 7/26",
    "G01M 17/02"
  ],
  "assignees": [
    "Compagnie Generale des Etablissements Michelin SCA"
  ],
  "inventors": [
    "Thomas Ledoux",
    "Denis Martin",
    "Patrick Meneroud",
    "Grégory MICHAUD"
  ],
  "filing_date": "2014-06-20",
  "publication_date": "2018-10-30",
  "grant_date": "2018-10-30",
  "priority_date": "2013-06-20",
  "application_number": "US-201414899848-A",
  "family_id": "49510249",
  "cited_by_count": 7,
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}