FIXING SYSTEM FOR HOUSING FOR MEASURING CHARACTERISTICS OF A TIRE

Abstract

A ground attachment system (1) for a tire characteristics detection unit (15).sub.7 comprises an attachment plate (2) comprising a plurality of recesses (3) distributed over the surface of the attachment plate, a plurality of frustoconical clamping rings (4), and a plurality of cylindrical guide tunnels (5) arranged in the detection unit (15), the clamping rings (4) and the guide tunnels (5) each comprising a complementary conical portion (6, 7) converging towards the attachment plate (2) when the ring (4) is in the clamping position in a tunnel (5).

Claims

1.-8. (canceled)

9. A ground attachment system for a unit for detecting characteristics of tires, the attachment of the unit being configured so as to withstand stresses associated with having numerous vehicles drive over the unit, the ground attachment system comprising: (i) an attachment plate comprising a plurality of recesses distributed over a surface of the attachment plate; (ii) a plurality of frustoconical clamping rings; and (iii) a plurality of cylindrical guide tunnels arranged in the unit, wherein the frustoconical clamping rings and the cylindrical guide tunnels each comprise a complementary conical portion converging toward the attachment plate when the frustoconical clamping ring is in a clamping position in a tunnel.

10. The ground attachment system according to claim 9, wherein the conical portion of each of the frustoconical clamping rings is shaped in a median portion of an external profile of the frustoconical clamping rings.

11. The ground attachment system according to claim 9, wherein the conical portion of each of the cylindrical guide tunnels is shaped on an internal profile of the cylindrical guide tunnels at an exit from the tunnel.

12. The ground attachment system according to claim 9, wherein the cylindrical guide tunnels are integrally formed with the unit.

13. The ground attachment system according to claim 9, wherein the cylindrical guide tunnels are inserts fixed in holes in the unit.

14. The ground attachment system according to claim 9, wherein a level of clamping of each of the frustoconical clamping rings is adjusted by a screw passing through the frustoconical clamping ring and cooperating with an attachment plate.

15. The ground attachment system according to claim 9, wherein clamping of each of the frustoconical clamping rings is adjusted by a screw passing through the frustoconical clamping ring and cooperating with a nut arranged in the attachment plate.

16. A tire characteristics detection assembly comprising: a unit for detecting tire characteristics; and the ground attachment system according to claim 9.

Description

DESCRIPTION OF THE FIGURES

[0021] All the embodiment details are given in the description which follows, which is supplemented by FIGS. 1 to 5, which are given solely by way of non-limiting examples and in which:

[0022] FIG. 1 is a perspective view of an example of a tyre characteristics detection assembly;

[0023] FIG. 2 is a top view of an exemplary attachment plate;

[0024] FIG. 3 is a perspective view of an exemplary electronic unit for detecting characteristics of tyres;

[0025] FIG. 4 is a schematic sectional representation of an exemplary attachment system for a tyre characteristics measurement unit;

[0026] FIG. 5 is an alternative embodiment of the attachment system of FIG. 4.

DETAILED DESCRIPTION OF THE INVENTION

[0027] Tyre Characteristics Measurement Unit

[0028] FIG. 1 illustrates an example of a known assembly 30 for measuring the thickness of a layer of rubbery material of a tyre 41 of a vehicle 40, such as that described in document FR3007517. The assembly 30 comprises an electronic unit 15 for detecting characteristics of tyres and an attachment plate 2 as illustrated in FIGS. 2 and 3. When the vehicle 40 is driving over the electronic tyre characteristics detection unit 15, sensors make it possible to carry out one or more measurements, such as measurements of the tread thickness of the tyre 41. To carry out the measurements, the device is preferably placed in a location that makes it easy for the vehicles 40 to drive over it. The manner in which the unit is attached is therefore advantageously designed to withstand the significant stresses associated with many vehicles driving over it. These stresses require reliable and durable fastening, as described in the following figures.

[0029] FIG. 2 illustrates an example of an attachment plate 2. In this example, the plate is divided into two parts joined to each other to provide a larger width. The attachment plate 2 is fixed to the ground by a conventional means, such as for example a layer 21 of adhesive. The plate has a plurality of recesses 3. In the example illustrated, the recesses 3 are aligned in the longitudinal direction of the plate, parallel to the edges and spaced apart regularly. Each of the 3 recesses can accommodate a frustoconical clamping ring 4 (described later in relation to FIGS. 4 and 5). The length of the attachment plate 2 is preferably greater than that of the electronic tyre characteristics detection unit 15 that is to be attached, and the number of recesses 3 is greater than the number of frustoconical clamping rings 4 that are to be housed in order to allow the unit 15 to be positioned at a plurality of locations along the longitudinal axis L-L of the attachment plate 2. The geometry of the attachment plate 2 and the installation method then make it possible to easily reposition the system by a few centimetres to best match the statistical distribution of the drive-over events, which becomes known once the system has been in use for a time.

[0030] FIG. 3 illustrates an exemplary embodiment of an electronic tyre characteristics detection unit 15. In the example, this unit is in the form of a bevelled slab in order to make it easier for the vehicle 40 to get on and off the unit. A slot can be arranged in the unit 15 in order to make it possible to carry out the measurements.

[0031] Attaching the Unit to the Plate

[0032] FIGS. 4 and 5 illustrate an exemplary embodiment of the attachment system 1. In these examples, the unit 15 is attached to the plate 2 by means of a plurality of frustoconical clamping rings 4 inserted into the same number of cylindrical guide tunnels 5, whose shapes and dimensions match those of the rings 4. These complementary shapes and dimensions are provided so as to allow easy positioning of the rings 4 in the tunnels before tightening, then to provide double-action clamping when the clamping screw 8 is put in place and tightened.

[0033] Each ring has an annular body, with an axial bore for inserting a clamping screw 8. The external profile of a ring comprises a conical portion 6, extending over all or part of the lateral face of the ring. In the examples illustrated in FIGS. 4 and 5, the conical portion 6 is arranged in the median zone of the ring, i.e. substantially at mid-height of the outer periphery. To allow attachment of a unit 15 without axial play, and without radial play, the unit comprises a plurality of cylindrical guide tunnels 5 distributed over the surface of the unit in order to provide a plurality of attachment points. Each of the tunnels consists of a through-opening provided in the unit. In the examples illustrated, the internal profile of the tunnels is cylindrical, with a conical portion 7 provided in the vicinity of the face of the unit which is in contact with the plate 2 when the unit 15 is attached to the latter.

[0034] Thus, by virtue of this complementary architecture of the rings 4 and the tunnels 5, the frustoconical clamping rings 4 and the cylindrical guide tunnels 5 comprise a complementary conical portion 6, 7 converging towards the attachment plate 2. A clamping screw 8, passing through the ring 4 and screwing directly into the plate 2 (which is drilled and threaded for that purpose) or into a nut 9 provided under the plate, makes it possible to attach the unit so that the clamping exerts a holding force that is both axial and radial. The axial clamping force pushes the unit against the mounting plate. The radial clamping force acts uniformly over the entire circumference of the ring and produces a holding force over the entire internal face of the tunnel. The material of the ring is advantageously chosen to deform slightly under the action of the tightening of the screw 8, so as to press on the conical portion 7 of the tunnel over 360°.

[0035] Drilled-Hole Tunnel or Ring Tunnel

[0036] Depending on the type of embodiment provided, the cylindrical tunnel 5 may be integral with the detection unit 15, as illustrated in the example of FIG. 4. In this case, the tunnel is for example produced by drilling into the unit. As a variant, the cylindrical tunnels 5 are provided in inserts 10 secured in the unit 15, as illustrated in the example of FIG. 5. This embodiment allows tunnels to be made with a material different from that of the unit.

[0037] Operating Principle of the Magnetic Sensor for Measurement of Tyre Characteristics

[0038] The sensor of known type makes it possible to measure the thickness of a layer of rubbery material of a tyre, for example the tread. In a conventional manner, such a layer has a face joined to an adjacent reinforcement produced with at least one material with a magnetic permeability greater than the magnetic permeability of air and a free face in contact with the air. The sensor is designed to measure the distance between the joined face and the free face of the layer of rubbery material.

[0039] The sensor has a static magnetic field source and a sensitive element, the output signal of which depends on the level of the local magnetic field, disposed such that the magnetic field strength measured by the sensitive element varies when the distance to be measured decreases.

[0040] The thicknesses of the tread have a very small thickness to be measured. Consequently, the measurement needs to be extremely precise.

[0041] In order to ensure a precise and reliable measurement, it is necessary for the different elements that make up the measurement chain to be held perfectly, if possible without play or with as little play as possible. The slightest play between the elements of the sensor and/or between the elements of the sensor and the unit could impair the quality or reliability of the measurements. As previously described, the elements are secured so as to minimize vibrations and/or movement of the parts of the system.

[0042] Materials

[0043] The solution is sized to withstand the braking of a truck at 70 km/h, and to withstand hundreds of thousands of axle drive-over events. The choices of material and geometry of the frustoconical clamping ring 4 and of the cylindrical tunnel 5 and of the plate 2 are provided to withstand mechanical stresses, in particular shearing, compression, and hammering effects.

[0044] The plate is advantageously made using a thermosetting material that has low water absorption and is resistant to hydrocarbons. The choice of a thermosetting material makes it possible to have excellent electrical permittivity, magnetic permeability and low dielectric losses.

[0045] The attachment plate 2 is advantageously made of polyester, preferably reinforced with glass fiber (GPO3). GPO3 is also a material having low surface tension, good porosity and good affinity to many bonding resins.

[0046] The frustoconical clamping rings 4 are advantageously made of polyamide, preferably PA 66, which is advantageous on account of its resilience, low flow and chemical resistance.

[0047] A material is preferably provided for the plate 2 of higher hardness than that of the frustoconical clamping ring 4, which makes it possible to obtain a degradation of the rings 4 before that of the plate 2. Indeed, the replacement of the frustoconical clamping rings 4 is simple and economical compared to that of the plate 2.

TABLE-US-00001 Reference numerals employed in the figures  1 Ground attachment system for unit  2 Attachment plate  3 Recess  4 Frustoconical clamping ring  5 Cylindrical guide tunnel  6 Conical ring portion  7 Conical tunnel portion  8 Screw  9 Nut 10 Insert 15 Measurement unit (for example for measuring tyre characteristics) 20 Coating 21 Adhesive 30 Assembly for detecting tyre characteristics 40 Vehicle 41 Tyre