WO2023094750A1

WO2023094750A1 - Reinforced product with fixed cable geometry, having intermediate bi-modulus behaviour

Info

Publication number: WO2023094750A1
Application number: PCT/FR2022/052126
Authority: WO
Inventors: Gaël PATAUT; Lucas LAUBY; Olivier REIX; Sébastien Noel
Original assignee: Compagnie Generale Des Etablissements Michelin
Priority date: 2021-11-25
Filing date: 2022-11-18
Publication date: 2023-06-01
Also published as: FR3129319A1; FR3129319B1

Abstract

The invention relates to a reinforced product (R1) comprising a polymer matrix (Ma) and at least one cable (50) comprising a single layer consisting of N metal reinforcing elements, said elements being either: - metal wires (F) having a diameter Df, with the metal reinforcing elements (54) having a diameter Dh which is the diameter of the theoretical circle passing through the centres of the wires (F) of the layer in a plane perpendicular to the main axis of the cable and a diameter D which is the outer diameter of the cable (50); - or strands (T) wound in a helix about a main axis (A), each strand (T) comprising a single layer (56) consisting of M > 1 of metal wires (FT) wound in a helix about an axis (B) having a diameter Df with the metal reinforcing elements (54) having a diameter Dh which is the diameter of the theoretical circle passing through the centres of the wires (FT) of the layer (56) in a plane perpendicular to the main axis of the strand (T) and a diameter D which is the outer diameter of the strand (T); with D, Dh and Df expressed in millimetres: 0.20 < Jr ≤ 0.30, with Jr=N/(π x (D-Df)) x (Dh x Sin(π/N) – (Df / Cos(α x π/180))), α being the helix angle, expressed in degrees, of each metal wire; the polymer matrix (Ma) has a secant elastic modulus MA10 at 10% deformation ranging from 2.5 to 18.0 MPa; the reinforced product (R1) has an Emax to Emin modulus ratio such that 1< Emax/Emin < 5, with Emin being the minimum secant elastic modulus from the load-elongation curve prior to the structural elongation point As and Emax being the maximum tangent modulus of the same load-elongation curve; and - the reinforced product (R) has a structural elongation As such that 0 < As < 3%.

Description

Reinforced product with fixed cable geometry presenting an intermediate bimodule behavior

[001] The present invention relates to a reinforced product and a tire comprising such a product.

[002] Although not limited to this type of application, the invention will be more particularly described with reference to a tire for passenger vehicles.

[003] By tire is meant a tire intended to form a cavity by cooperating with a support element, for example a rim, this cavity being capable of being pressurized to a pressure greater than atmospheric pressure. A tire according to the invention has a structure of substantially toroidal shape.

[004] Known from the state of the art is a tire comprising a crown reinforcement comprising bi-module cords as described in application WO 2020021006. In order to obtain a reinforced product having sufficient rigidity, it is however necessary to select the cable which has the expected rigidity once embedded in the polymer matrix.

[005] Thus, it is necessary to select cables according to the position for which it is intended in the tire and in particular in the crown ply which requires intermediate rigidity for the performance compromise of the tire and sufficient elongation for the step construction/curing of the tire and therefore a more or less marked bi-module behavior. This step can be long and tedious to select the reinforced product cable that meets the specifications.

[006] Usually, to vary the stiffness of a reinforced product, those skilled in the art mainly play on the architecture of the cable, for example by modifying the helix angle. Several cable geometries are therefore necessary to vary the rigidity of the reinforced product in order to adapt the reinforced product to the intended use.

[007] The aim of the invention is to provide a reinforced product whose control of the rigidity and the bi-module behavior is simplified by modifying the polymer matrix without modifying the cable.

[008] To this end, the subject of the invention is a reinforced product comprising a polymer matrix and at least one cable comprising a single layer consisting of N metal reinforcement elements wound in a helix, each metal reinforcement element of the layer describing, when the cable extends in a substantially rectilinear direction, a helix-shaped trajectory around a principal axis substantially parallel to the substantially rectilinear direction, so that, in a section plane substantially perpendicular to the principal axis, the distance between the center of each metal reinforcement element of the layer and the main axis is substantially constant and equal for all the metal reinforcement elements of the layer, the elements of metal reinforcement being:

- or metal wires having a diameter Df, with the metal reinforcing elements having a diameter Dh which is the diameter of the theoretical circle passing through the centers of the wires of the layer in a plane perpendicular to the main axis of the cable and a diameter D which is the outer diameter of the cable; Or

- or strands wound helically around a main axis, each strand comprising a single layer consisting of M>1 metal son wound helically around an axis having a diameter Df with the metal reinforcing elements having a diameter Dh which is the diameter of the theoretical circle passing through the centers of the yarns of the layer in a plane perpendicular to the main axis of the strand and a diameter D which is the outside diameter of the strand; with D, Dh and Df expressed in millimeters:

- the relative radial clearance Jr being such that: 0.20 < Jr < 0.30

With Jr=N/(ïT x (D-Df)) x (Dh x Sin(n7N) - (Df / Cos(a x TT/180))), a being the helix angle, expressed in degrees, of each wire;

- the polymer matrix has a secant elastic modulus MA10 at 10% deformation% determined according to standard NF ISO 37 of February 2018 ranging from 2.5 to 18.0 MPa;

- the reinforced product has a modulus ratio Emax to Emin such that 1 < Emax/Emin <5 with Emin being the minimum secant elastic modulus in tension, i.e. the slope of the straight line connecting the origin of the stress-elongation curve (0%; OMPa) obtained under the conditions of standard ASTM D 2969 - 04 of 2014 and Emax being the maximum tangent modulus of the same force-elongation curve; And

- the reinforced product has a structural elongation As such that 0<As<3% determined by standard ASTM D2969-04 of 2014.

[009] The inventors at the origin of the invention realized that by fixing the geometry of the cable and in particular its relative play, it was possible to control on the one hand the rigidity of the reinforced product by playing on the rigidity of the matrix polymer and on the other hand to vary the bimodule behavior of the reinforced product, always by varying the rigidity of the polymer matrix. Thus, the same cable can be used for different positions in the tire by varying the rigidity of the polymer matrix.

[010] The reinforced product according to the invention therefore makes it possible to significantly vary the rigidity of the reinforced product without changing the grade of steel or without varying the metal mass engaged.

[011] By elastomeric matrix is meant a matrix with elastomeric behavior resulting from the crosslinking of an elastomeric composition. The elastomeric matrix is thus based on the elastomeric composition. Just like the elastomeric matrix, the filling material is based on an elastomeric composition, here the same composition as that of the matrix in which the cable is embedded.

[012] The values of the characteristics Dh, D, Df, Dv, Rf and a as well as the other characteristics described below are measured on or determined from the cables either directly after manufacture, that is to say before any step of embedding in an elastomeric matrix, or extracted from an elastomeric matrix, for example from a tire, and having then undergone a cleaning step during which any elastomeric matrix is removed from the cable, in particular any material present inside the cable. To guarantee an original state, the adhesive interface between each metal reinforcement element and the elastomeric matrix must be removed, for example by electro-chemical process in a bath of sodium carbonate. The effects associated with the shaping step of the tire manufacturing process described below, in particular the elongation of the cords, are canceled out by the extraction of the ply and of the cord which resume, upon extraction, substantially their characteristics before the shaping step.

[013] The cable according to the invention comprises a single layer of helically wound metal reinforcing elements. In other words, the cable according to the invention comprises only one, not two, nor more than two layers of metal reinforcing elements wound in a helix. The layer consists of metal reinforcement elements, i.e. several metal reinforcement elements, not a single metal reinforcement element. In one embodiment of the cable, for example when the cable comes from its manufacturing process, the cable according to the invention consists of the layer of wound metal reinforcing elements, in other words the cable does not comprise any other metallic reinforcement element than those of the layer.

[014] In one embodiment, the cable is single helix. By definition, a single helix cable is a cable in which the axis of each metal reinforcement element of the layer describes a single helix, unlike a double helix cable in which the axis of each metal reinforcement element describes a single helix. first helix around the axis of the cable and a second helix around a helix described by the axis of the cable. In other words, when the cable extends in a substantially straight direction, the cable comprises a single layer of metal wire elements wound together in a helix, each metal reinforcing element of the layer describing a path in the form of a helix. around a main axis substantially parallel to the substantially straight direction so that, in a section plane substantially perpendicular to the main axis, the distance between the center of each metal reinforcement element of the layer and the main axis is substantially constant and equal for all the metallic reinforcement elements of the layer. On the contrary, when a double helix cable extends in a substantially straight direction, the distance between the center of each metallic reinforcement element of the layer and the substantially straight direction is different for all the elements of metallic reinforcement of the layer.

[015] In another embodiment of the invention, the cable is double helix.

[016] The cable according to the invention has no central metal core. We also speak of a 1xN structure cable or even an open-structure cable (“open-cord” in English). In the cable according to the invention defined above, the internal vault is empty and therefore devoid of any filling material, in particular devoid of any elastomeric composition. This is referred to as a cable without filler material.

[017] The vault of the cable according to the invention is delimited by the metal reinforcement elements and corresponds to the volume delimited by a theoretical circle, on the one hand, radially inside each metal reinforcement element and, on the other hand, tangent to each metal reinforcement element. The diameter of this theoretical circle is equal to the arch diameter Dv.

[018] By wire element is meant an element extending longitudinally along a main axis and having a section perpendicular to the main axis, the largest dimension G of which is relatively small compared to the dimension L along the main axis. By relatively low, it is meant that L/G is greater than or equal to 100, preferably greater than or equal to 1000. This definition covers both wireframe elements of circular section and wireframe elements of non-circular section, for example of polygonal section or oblong. Very preferably, each metal reinforcement element has a circular section.

[019] By metallic, we mean by definition a wire element consisting mainly (that is to say for more than 50% of its mass) or entirely (for 100% of its mass) of a metallic material. Each metallic reinforcement element is preferably made of steel, more preferably of pearlitic or ferrito-pearlitic carbon steel, commonly called by those skilled in the art carbon steel, or even stainless steel (by definition, steel comprising at least 10.5 % chromium).

[020] The structural elongation As, a quantity well known to those skilled in the art, is determined for example by applying the ASTM D2969-04 standard of 2014 to a reinforced product tested so as to obtain a force-elongation curve. The As is deduced on the curve obtained as the elongation, in %, corresponding to the point of intersection of the tangent to the elastic part of the force-elongation curve with the axis of the elongations. As a reminder, an elongation force curve includes, moving towards increasing elongations, a structural part, an elastic part and a plastic part. The structural part corresponds to a structural elongation of the cable resulting from the bringing together of the various metal reinforcement elements constituting the cable. In some embodiments, the layer of N metal reinforcing elements breaks down at the end of the structural part, due to the relatively low relative radial clearance Jr, causing a temporary increase in the modulus of the cable. The elastic part corresponds to an elastic elongation resulting from the construction of the cable, in particular the angles of the various layers and the diameters of the wires. The plastic part corresponds to the plastic elongation resulting from the plasticity (irreversible deformation beyond the elastic limit) of one or more metal reinforcement elements of the reinforced product.

[021] The relative radial play Jr is representative of the distance separating each pair of adjacent metal wire elements reduced to the length available to position the metal wire elements on the layer. Thus, the higher Jr, the greater the space separating two adjacent metallic wireframe elements compared to the maximum number of metallic wireframe elements that the layer could accommodate. Conversely, the smaller Jr, the smaller the space separating two adjacent metallic wireframe elements compared to the maximum number of metallic wireframe elements that the layer could accommodate. In the interval according to the invention, Jr makes it possible to maximize the number of metallic wire elements present on the layer and therefore the reinforcement capacity of the cable without however impairing the capacity for accommodation of longitudinal compression deformations.

[022] The Emax/Emin ratio is determined from the force-elongation curve obtained under the conditions of standard ASTM D 2969 - 04 of 2014 as shown in Figures 6 and 7.

[023] E min is the minimum secant elastic modulus in tension, i.e. the slope of the straight line connecting the origin of the stress-elongation curve (0%; OMPa) obtained under the conditions of the ASTM standard D 2969 - 04 of 2014, expressed in GPa.

[024] Emax is the maximum tangent modulus of this same force-elongation curve, expressed in GPa.

[025] The helix angle a is a quantity well known to those skilled in the art and can be determined by the following iterative calculation comprising 3 iterations and in which the index i indicates the number of the iteration 1, 2 or 3. Knowing the structural elongation As expressed in %, the helix angle a(i) is such that a(i)=Arcos [ (100/(100+As) x Cos [ Arctan ( (TT X Df ) / (P x Cos(a(i-1 )) x Sin(n7N )) ] ], where P is the pitch expressed in millimeters at which each metal reinforcement element is wound, N is the number of elements of metallic reinforcement of the layer, Df is the diameter of each metallic reinforcement element expressed in millimeters, Arcos, Cos and Arctan and Sin designating the arcosine, cosine, arctangent and sine functions respectively. say for the calculation of a(1), we take a(0)=0. At the third iteration, we obtain a(3)=a with at least one significant digit after the decimal point when a is expressed in degrees.

[026] The helix diameter Dh, expressed in millimeters, is calculated according to the relation Dh=P x Tan(a) / TT in which P is the pitch expressed in millimeters at which each metal reinforcement element is wound, a is l helix angle of each reinforcing element metal determined above and Tan the tangent function. The helix diameter Dh corresponds to the diameter of the theoretical circle passing through the centers of the metal reinforcement elements of the layer in a plane perpendicular to the axis of the cable.

[027] The arch diameter Dv, expressed in millimetres, is calculated according to the relation Dv=Dh- Df in which Df is the diameter of each metal reinforcement element and Dh the helix diameter, both expressed in millimetres.

[028] The diameter or apparent diameter, denoted D of the cable when the metal reinforcing elements are wires, is measured by means of a thickness comparator whose diameter of the keys is at least equal to 1.5 times the pitch P winding of the wired elements (one can cite for example the JD50 model of the KAEFER brand allowing an accuracy of 1/100 of a millimeter to be achieved, equipped with a type a key, and having a contact pressure close to 0.6N ). The measurement protocol consists of three repetitions of a series of three measurements (carried out perpendicular to the axis of the cable and under zero tension) of which the second and third of these measurements are carried out in a direction angularly offset from the previous one by a third of a turn, by the rotation of the direction of measurement around the axis of the cable or the strand.

[029] The diameter or apparent diameter, denoted D of the strand when the reinforcing elements are strands, is measured by wedging the cable between two perfectly straight bars 200 mm in length and by measuring the spacing in which the cable is embedded using the comparator described below. We can cite for example the JD50/25 model of the KAEFER brand allowing to reach an accuracy of 1/100 of a millimeter, equipped with a type a touch, and having a contact pressure close to 0.6N. The measurement protocol consists of three repetitions of a series of three measurements (carried out perpendicular to the axis of the cable and under zero tension).

[030] It is recalled that the pitch at which each metal reinforcing element is wound is the length traveled by this wire element, measured parallel to the axis of the cable in which it is located, at the end of which the wire element having this pitch performs a full turn around said axis of the cable.

[031] The optional features described below may be combined with each other insofar as such combinations are technically compatible.

[032] In an advantageous embodiment, all the metal wires have the same diameter Df.

[033] The cable of the reinforced product according to the invention is manufactured in accordance with a method and by implementing an installation described in the documents WO2016083265 and WO2016083267. Such a method implementing a splitting step is to be distinguished from a conventional wiring method comprising a single assembly step in which the metal reinforcing elements are wound helically, the step assembly being preceded by a step of preforming the metal reinforcement elements in order in particular to increase the value of the structural elongation. Such methods and installations are described in the documents EP0548539, EP1000194, EP0622489 or even EP0143767. During these processes, in order to obtain the highest possible structural elongation, the metallic monofilaments are individually preformed. However, this step of individual preformation of the metal monofilaments, which requires a particular installation, on the one hand, makes the method relatively unproductive compared to a method devoid of a preformation step without however making it possible to achieve high structural elongations. and, on the other hand, alters the metal monofilaments thus preformed due to friction with the preforming tools. Such an alteration creates incipient fractures at the surface of the metal monofilaments and is therefore harmful for the endurance of the metal monofilaments, in particular for their endurance under compression. The absence or presence of such preformation marks can be observed under an electron microscope at the end of the manufacturing process, or even more simply, by knowing the manufacturing process of the cable.

[034] By definition, the MA10 is the secant tensile modulus of elasticity of a vulcanized polymer matrix measured at 10% elongation from a stress-elongation curve produced according to the recommendations of the NF ISO 37 standard of February 2018. This is the elastic modulus of the mixture measured during a uniaxial tensile experiment, at an elongation value of 0.1 (i.e. 10% elongation, expressed as a percentage). A constant speed of uniaxial traction is imposed on the test piece, and its elongation and the force are measured. The measurement is carried out using an INSTRON-type tensile machine, at a temperature of 23°C, and a relative humidity of 50% (ISO 23529 standard). The conditions for measuring and using the results to determine the elongation and the stress are as described in standard NF ISO 37: 2018-02. The stress is determined for an elongation of 0.1 and the elastic modulus at 10% is calculated by calculating the ratio of this stress value to the elongation value. A person skilled in the art will be able to choose and adapt the dimensions of the test piece according to the quantity of mixture accessible and available, in particular in the case of taking samples from a finished product such as a tire.

[035] Any interval of values denoted by the expression "between a and b" represents the range of values going from more than a to less than b (i.e. limits a and b excluded) while any interval of values designated by the expression “from a to b” means the range of values going from a to b (that is to say including the strict limits a and b).

[036] By radial section or radial section here is meant a section or a section along a plane which comprises the axis of rotation of the tire.

[037] By axial direction is meant the direction substantially parallel to the axis of rotation of the pneumatic.

[038] Circumferential direction means the direction which is substantially perpendicular both to the axial direction and to a radius of the tire (in other words, tangent to a circle whose center is on the axis of rotation of the pneumatic).

[039] By radial direction, we mean the direction along a radius of the tire, that is to say any direction intersecting the axis of rotation of the tire and substantially perpendicular to this axis.

[040] The median plane (denoted M) is the plane perpendicular to the axis of rotation of the tire which is located halfway between the two beads and passes through the middle of the crown reinforcement. [041] The equatorial circumferential plane (denoted E) of the tire is the theoretical plane passing through the equator of the tire, perpendicular to the median plane and to the radial direction. The equator of the tire is, in a plane of circumferential section (plane perpendicular to the circumferential direction and parallel to the radial and axial directions), the axis parallel to the axis of rotation of the tire and located equidistant between the point radially outermost point of the tread intended to be in contact with the ground and the radially innermost point of the tire intended to be in contact with a support, for example a rim, the distance between these two points being equal to H.

[042] Orientation of an angle means the direction, clockwise or anti-clockwise, in which it is necessary to turn from a reference straight line, here the circumferential direction of the tire, defining the angle to reach the other line defining the angle.

[043] Advantageously, the metal reinforcement elements define an internal arch of the cable of diameter Dv, each metal reinforcement element having a diameter Df and a helix radius of curvature Rf defined by Rf=P/(ïT x Sin(2a )) with P the pitch of each metal reinforcement element expressed in millimeters and a the helix angle of each metal reinforcement element (54) and Dv=Dh-Df, in which Dv, Dh and Df being expressed in millimeters :

1.30 < Dv / Df < 4.50.

[044] The radius of curvature Rf, expressed in millimeters, is calculated according to the relationship Rf=P/(ïT x Sin(2a)) in which P is the pitch expressed in millimeters of each metal reinforcement element, a is the helix angle of each metal reinforcement element and Sin the sine function.

[045] Advantageously, θ<Rf/Df<30.

[046] Preferably, the total elongation At >1.5% determined by standard ASTM D2969-04 of 2014.

[047] Advantageously, the helix diameter Dh of each metal reinforcement element (54) is such that 0.70 mm <Dh <1.60 mm, preferably 0.75 mm <Dh <1.60 mm and more preferably 0.80 mm<Dh<1.60 mm. [048] Advantageously, Df is such that 0.10 mm <Df <0.50 mm, preferably 0.15 mm <Df <0.50 mm and more preferably 0.15 mm <Df <0.45 mm.

[049] Advantageously, Dv is such that Dv>0.40 mm, preferably 0.50 mm<Dv<1.20 mm.

[050] Preferably, each metal reinforcement element is wound at a pitch P such that 3 mm <P <15 mm, preferably 5 mm <P <13 mm and more preferably 7 mm <P <11 mm. It can also be seen that the reinforced product according to the invention allows a wider range of adjustment of the rigidity of the reinforced product than with other elastic cables by varying the pitch of the fabric.

[051] Advantageously, the diameter of the cable or the strand D <2.10 mm, preferably 0.90 mm <D <2.10 mm and more preferably 0.95 mm <D <2.05 mm.

[052] In a first preferred embodiment, each metallic reinforcement element of the cable is a metallic wire with N ranging from 3 to 18 and preferably from 4 to 15.

[053] In a second preferred embodiment, each metal reinforcing element of the cable is a strand with N ranging from 3 to 5, M ranging from 3 to 18 and preferably from 4 to 15.

[054] In this second preferred embodiment, the strands advantageously define an internal vault of the cable of diameter Dvc, each strand having a diameter D and a helix radius of curvature Rt defined by Rt=Pe/(ïT x Sin (2ae)) with Pe the pitch of each strand expressed in millimeters and ae the helix angle of each strand (T), Dvc, D and Rt being expressed in millimeters, the cable satisfies the following relationships: 5 < Rt / D < 550 and 0.10 < Dvc / D < 0.50.

[055] The cable of the reinforced product according to this second embodiment has excellent longitudinal compressibility and, all other things being equal, a relatively small diameter.

[056] On the one hand, the inventors at the origin of the invention hypothesize that, due to a sufficiently high radius of curvature Rt with respect to the diameter D of each strand, the cable is sufficiently ventilated, thus reducing the risk of buckling, due to the relatively large distance of each strand from the longitudinal axis of the cable, this distance allowing the strands to accommodate, through their helix, relatively high longitudinal compression deformations. On the contrary, the radius of curvature Rt of each strand of the cable of the state of the art being relatively small compared to the diameter D, the metallic wire elements are closer to the longitudinal axis of the cable and can accommodate, by their propeller, much lower longitudinal compression deformations.

[057] On the other hand, for a radius of curvature Rt of each strand that is too high, the cable according to the invention would have insufficient longitudinal rigidity in compression to ensure a reinforcement role, for example of tires. [058] In addition, for an internal vault diameter Dvc that is too high, the cable would have, relative to the diameter of the strands, a diameter that is too high.

[059] The values of the Dt, Dvc and Rt characteristics as well as the other characteristics described above are measured on or determined from the cables either directly after manufacture, that is to say before any step of embedding in a matrix elastomeric material, or extracted from an elastomeric matrix, for example from a tire, and then having undergone a cleaning step during which any elastomeric matrix, in particular any material present inside the cable, is removed from the cable. To guarantee an original state, the adhesive interface between each metal wire element and the elastomeric matrix must be removed, for example by electro-chemical process in a bath of sodium carbonate. The effects associated with the shaping step of the tire manufacturing process described below, in particular the elongation of the cords, are canceled out by the extraction of the ply and of the cord which resume, upon extraction, substantially their characteristics before the shaping step.

[060] The arch of the cable of the reinforced product according to this second embodiment is delimited by the strands and corresponds to the volume delimited by a theoretical circle, on the one hand, radially inside each strand and, on the other hand, tangent to each strand. The diameter of this theoretical circle is equal to the arch diameter Dvc.

[061] The helix angle of each strand ae is a quantity well known to those skilled in the art and can be determined by the following calculation: tan ae = 2xn x Re/Pe, formula in which Pe is the pitch expressed in millimeters in which each strand is wound, Re is the helix radius of each strand expressed in millimeters, and tan denotes the tangent function, ae is expressed in degrees.

[062] The helix diameter De, expressed in millimeters, is calculated according to the relation De=Pe x Tan(ae) / TT in which Pe is the pitch expressed in millimeters at which each strand is wound, ae is the angle d helix of each strand determined above and Tan the tangent function. The helix diameter De corresponds to the diameter of the theoretical circle passing through the centers of the strands of the layer in a plane perpendicular to the main axis of the cable.

[063] The arch diameter Dvc, expressed in millimetres, is calculated according to the relation Dvc=De- D in which t is the diameter of each strand and De the helix diameter, both expressed in millimetres.

[064] The radius of curvature Rt, expressed in millimeters, is calculated according to the relationship Rt=Pe/(ïT x Sin(2ae)) in which Pe is the pitch expressed in millimeters of each strand, ae is the angle of helix of each strand and Sin the sine function.

[065] It is recalled that the pitch at which each strand is wound is the length traveled by this wire element, measured parallel to the axis of the cable in which it is located, at the end of which the strand having this pitch makes a complete turn around said cable axis. [066] In this second preferred embodiment, the pitch of each strand Pe advantageously ranges from 20 mm to 120 mm.

[067] TIRE ACCORDING TO THE INVENTION

[068] Another subject of the invention is a tire comprising at least one reinforced product as defined above.

[069] Preferably, the tire comprises a crown comprising a tread and a crown reinforcement, two sidewalls, two beads, each sidewall connecting each bead to the crown, the crown reinforcement extending in the crown in a direction circumferential of the tire, the tire comprising a carcass reinforcement anchored in each of the beads and extending in the sidewalls and in the crown, the crown reinforcement being radially interposed between the carcass reinforcement and the tread, the crown reinforcement comprising at least one reinforced product as defined above.

[070] In an advantageous embodiment, the hooping reinforcement comprises a single hooping layer. The hooping reinforcement preferably consists of a hooping ply comprising the reinforced product according to the invention. This embodiment is particularly suitable for a tire for passenger vehicles, two-wheel vehicles, industrial vehicles chosen from vans, "Heavyweight", for example metro, bus, road transport vehicles (trucks, tractors, trailers), and preferably for passenger vehicles.

[071] In an advantageous embodiment, the hooping reinforcement is radially interposed between the working reinforcement and the tread. Thus, thanks to the use of metal cables, the hooping reinforcement exerts, in addition to its hooping function, a function of protection against perforations and shocks much more effective than a hooping reinforcement comprising wire elements of textile hooping reinforcement.

[072] In an advantageous embodiment, the or each hooping reinforcing wire element makes an angle strictly less than 10°, preferably less than or equal to 7° and more preferably less than or equal to 5° with the circumferential direction of the pneumatic.

[073] The invention will be better understood on reading the following examples, given solely by way of non-limiting examples and made with reference to the drawings in which:

- Figure 1 is a sectional view perpendicular to the circumferential direction of a tire (10) according to the invention;

- Figure 2 is a sectional view of a reinforced product (R) according to the invention;

- Figure 3 is a schematic sectional view perpendicular to the axis of the cable (assumed straight and at rest) of a cable (50) of the reinforced product (R) according to a first mode of realization of the invention;

- Figure 4 is a view similar to that of Figure 4 of a cable (50 ') of the reinforced product (R) according to a second embodiment of the invention;

- Figure 5 illustrates stress-elongation curves for reinforced products (R1;

R1 '; R1”; R1 ’”) according to a first mode of the invention comprising the cable (50);

- Figure 6 illustrates part of the stress-elongation curve for a reinforced product (R1) according to a first mode of the invention comprising the cable (50) and schematically represents the Emin and Emax modules; And

- Figure 7 illustrates part of the stress-elongation curve for a reinforced product (R2) according to a second embodiment of the invention comprising the cable (50') and schematically represents the Emin and Emax modules.

[074] EXAMPLE OF A TIRE ACCORDING TO THE INVENTION

[075] In Figure 1, there is shown an X, Y, Z mark corresponding to the usual directions respectively axial (X), radial (Y) and circumferential (Z) of a tire.

[076] There is shown schematically in Figure 1, a radial sectional view of a tire according to a first embodiment of the invention and designated by the general reference 10. The tire 10 is substantially of revolution around an axis substantially parallel to the axial direction X. The tire 10 is here intended for a passenger vehicle. [077] The tire 10 comprises a crown 12 comprising a crown reinforcement 14 comprising a working reinforcement 15 comprising two working plies 16, 18 of working reinforcing elements and a hooping reinforcement 17 comprising a hooping ply 19 of hooping reinforcement elements. The crown reinforcement 14 is surmounted by a tread 20 arranged radially outside the crown reinforcement 14. Here, the hooping reinforcement 17, the hooping ply 19, is radially interposed between the working reinforcement 15 and tread 20.

[078] The tire also comprises two sidewalls 22 extending the crown 12 radially inwards. The tire 10 further comprises two beads 24 radially inside the sidewalls 22 and each comprising an annular reinforcing structure 26, in this case a bead wire 28, surmounted by a mass of rubber 30 for bead filler, as well as a reinforcement of radial carcass 32.

[079] The carcass reinforcement 32 comprises at least one carcass ply comprising several reinforcing elements, the ply being anchored to each of the beads 24 by turning around the bead wire 28, so as to form in each bead 24 a strand forward 38 extending from the beads through the sidewalls towards the crown 12, and a return strand 40, the radially outer end 42 of the return strand 40 being radially outside the annular reinforcement structure 26. The reinforcement of carcass 32 thus extends from the beads 24 through the sidewalls 22 into the crown 12. The carcass reinforcement 32 is arranged radially inside the crown reinforcement 14 and the hooping reinforcement 17. The carcass reinforcement 32 comprises a single carcass ply 34.

[080] The tire 10 also includes an internal sealing layer 43, preferably made of butyl, axially inside the sidewalls 22 and radially inside the crown reinforcement 14 and extending between the two beads 24.

[081] Each working ply 16, 18, hooping 19 and carcass 34 comprises a polymeric composition in which are embedded reinforcing elements of the corresponding ply. Each polymeric composition, here an elastomeric composition, of the working plies 16, 18, of the hooping 19 and of the carcass 34 is produced in a conventional composition for calendering reinforcement elements conventionally comprising a diene elastomer, for example natural rubber , a reinforcing filler, for example carbon black and/or silica, a crosslinking system, for example a vulcanization system, preferably comprising sulfur, stearic acid and zinc oxide, and optionally a vulcanization accelerator and/or retarder and/or various additives.

With reference to FIG. 1, the single hooping ply 19 comprises at least the hooping reinforcing wire element constituted or formed by a filled cable 50 according to the invention embedded in the elastomeric matrix of the hooping ply 19 based of the elastomeric composition of the hooping ply 19.

[082] EXAMPLE OF A REINFORCED PRODUCT ACCORDING TO THE INVENTION

[083] There is shown in Figure 2 a reinforced product according to the invention and designated by the general reference R. The reinforced product R comprises at least one cable 50, in this case several cables 50, embedded in the polymer matrix Ma .

[084] In Figure 2, there is shown the polymer matrix Ma, the cables 50 in an X, Y, Z frame in which the Y direction is the radial direction and the X and Z directions are the axial and circumferential directions. In FIG. 2, the reinforced product R comprises several cables 50 arranged side by side in the main direction X and extending parallel to each other within the reinforced product R and collectively embedded in the polymer matrix Ma.

[085] Here, the polymer matrix Ma is an elastomeric matrix based on an elastomeric composition.

[086] The polymer matrix has a secant elastic modulus MA10 at 10% elongation determined according to standard NF ISO 37 of February 2018 ranging from 2.5 to 18.0 MPa. [087] The reinforced product R is the reinforced product R1. Here for the reinforced product R1, the secant elastic modulus MA10 at 10% elongation is 2.5 MPa. The reinforced product R1 has a modulus ratio Emax on Emin such that 1 < Emax/Emin <5 with Emin being the minimum secant elastic modulus in tension, that is to say the slope of the straight line connecting the origin of the stress-elongation curve (0%; OMPa) obtained under the conditions of standard ASTM D 2969 - 04 of 2014 and Emax being the maximum tangent modulus of the same force-elongation curve shown in Figure 6.

[088] Here Emin= 14 GPa.

[089] Here Emax=60 GPa.

[090] And Emax/Emin = 4.3 between 1 and 5.

[091] The reinforced product R1 has a structural elongation As such that 0<As<3% determined by standard ASTM D2969-04 of 2014.

[092] lci As= 1.8%.

REINFORCED PRODUCT CABLE ACCORDING TO A FIRST EMBODIMENT OF THE INVENTION

[093] There is shown in Figure 3 the cable 50 according to a first embodiment of the reinforced product of the invention.

[094] The cable 50 comprises a single layer consisting of N=11 metal reinforcement elements 54 wound in a helix, each metal reinforcement element 54 of the layer 52 describing, when the cable 50 extends in a substantially straight direction, a helix-shaped trajectory around a main axis (A) substantially parallel to the substantially rectilinear direction, so that, in a section plane substantially perpendicular to the main axis (A), the distance between the center of each metallic reinforcing element 54 of layer 52 and the main axis (A) is substantially constant and equal for all the metallic reinforcing elements 54 of layer 52, the metallic reinforcing elements 54 being metallic wires F (here 8 wires metal) having a diameter Df with the metal reinforcing elements 54 having a diameter Dh which is the diameter of the theoretical circle passing through the centers of the wires F of the layer in a plane perpendicular to the main axis of the cable and a diameter D which is the external diameter of cable 50 with D, Dh and Df being expressed in millimetres: - 0.20 < Jr < 0.30

With Jr=N/(ïT x (D-Df)) x (Dh x Sin(n7N) - (Df / Cos(a x TT/180))), a being the helix angle, expressed in degrees, of each wire F.

[095] Here Jr=0.24.

REINFORCED PRODUCT CABLE ACCORDING TO A SECOND EMBODIMENT OF THE INVENTION

[096] There is shown in Figure 4 the cable 50 'according to a second embodiment of the reinforced product of the invention.

[097] The 50' cable comprises a single layer made up of N=3 elements of metal reinforcements 54 wound in a helix, each metal reinforcement element 54 of the layer 52 describing, when the cable 50' extends in a substantially straight direction, a trajectory in the form of a helix around a main axis (A) substantially parallel to the substantially rectilinear direction, so that, in a section plane substantially perpendicular to the main axis (A), the distance between the center of each metal reinforcing element 54 of the layer 52 and the main axis (A ) is substantially constant and equal for all the metal reinforcement elements 54 of the layer 52, each metal reinforcement element 54 being T strands (here 3 strands) wound helically around a main axis (A), each T strand comprising a single layer 56 consisting of M>1 of metal wires FT wound in a helix around an axis (B) having a diameter Df with the metal reinforcement elements 54 having a diameter Dh which is the diameter of the theoretical circle passing through the centers of the wires FT of layer 56 in a plane perpendicular to the main axis of the strand T and a diameter D which is the outer diameter of the strand T with D, Dh and Df being expressed in millimeters:

- 0.20 < Day < 0.30

[098] Here Jr=0.24.

[099]

[0100] PROCESS FOR MANUFACTURING THE REINFORCED PRODUCT ACCORDING TO THE FIRST EMBODIMENT OF THE INVENTION

The cable 50 of the reinforced product R1 according to the first embodiment is produced according to the method described in application WO 2020/021006 by implementing an installation described in documents WO2016083265 and WO2016083267.

The reinforced product R1 is then obtained by embedding the cable 50 in a polymer matrix Ma. Here, the polymer matrix Ma is an elastomeric matrix.

[0103] PROCESS FOR MANUFACTURING THE REINFORCED PRODUCT ACCORDING TO THE SECOND EMBODIMENT OF THE INVENTION

[0104] The 50′ cable of the reinforced product R2 according to the second embodiment is produced according to the method described in the application WO2021140287.

The reinforced product R2 is then obtained by embedding the cable 50' in a polymer matrix Ma. Here, the polymer matrix Ma is an elastomeric matrix.

[0106] COMPARATIVE TESTS

The characteristics for the reinforced products of the first and second embodiments of the invention have been summarized in Tables 1 and 2 below. The stress-elongation curves of the reinforced products R1, RT, R1" and RT" were plotted with the cable 50 according to the first embodiment of the invention by applying the standard ASTM D 2969 - 04 of 2014 such as represented in FIG. 5 and the Emax/Emin ratio was determined as determined in FIG. 6 for R1, as well as the structural elongation As.

The results have been compiled in Table 1 below.

[0110] [Table 1]

according to the second embodiment of the invention by applying the standard ASTM D 2969 - 04 of 2014 and the Emax / Emin ratio was determined as shown in Figure 7, as well as the structural elongation As.

The Emax/Emin ratio was also determined, as well as the structural elongation

As for the reinforced product R2’.

The results have been compiled in Table 2 below for the reinforced products R2 and R2′.

[0114] [Table 2]

[0115] Tables 1 and 2 show that the reinforced products R1, R1 R1”, R1”, R2 and R2' according to the invention present a reinforced product using a cable with a predetermined geometry, in particular because of its relative clearance Jr whose rigidity and bi-module behavior can be controlled by modifying the polymer matrix without modifying the cable.

Thus, the reinforced products according to the invention make it possible to solve the problems mentioned in the preamble.

The invention is not limited to the embodiments described above.

Claims

CLAIMS Reinforced product (R), characterized in that it comprises a polymeric matrix (Ma) and at least one cable (50; 50') comprising a single layer (52) consisting of N metallic reinforcement elements (54) wound in helix, each metal reinforcing element (54) of the layer (52) describing, when the cable (50; 50') extends in a substantially straight direction, a helix-shaped trajectory around a main axis ( A) substantially parallel to the substantially rectilinear direction, so that, in a section plane substantially perpendicular to the main axis (A), the distance between the center of each metal reinforcement element (54) of the layer (52) and the main axis (A) is substantially constant and equal for all the metal reinforcement elements (54) of the layer (52), the metal reinforcement elements (54) being:

- or metal wires (F) having a diameter Df with the metal reinforcing elements (54) having a diameter Dh which is the diameter of the theoretical circle passing through the centers of the wires (F) of the layer in a plane perpendicular to the main axis of the cable and a diameter D which is the outside diameter of the cable (50);

- or strands (T) wound helically around a main axis (A), each strand (T) comprising a single layer (56) consisting of M>1 metal son (FT) wound helically around a axis (B) having a diameter Df with the metal reinforcing elements (54) having a diameter Dh which is the diameter of the theoretical circle passing through the centers of the threads (FT) of the layer (56) in a plane perpendicular to the main axis of the strand (T) and a diameter D which is the outside diameter of the strand (T); with D, Dh and Df expressed in millimeters:

- the relative radial clearance Jr being such that: 0.20 < Jr < 0.30 with Jr=N/(ïT x (D-Df)) x (Dh x Sin(n7N) - (Df / Cos(a x TT/ 180))), a being the helix angle, expressed in degrees, of each metal wire (F);

- the polymer matrix (Ma) has a secant elastic modulus MA10 at 10% deformation determined according to standard NF ISO 37 of February 2018 ranging from 2.5 to 18.0 MPa;

- the reinforced product (R) has a modulus ratio Emax to Emin such that 1 < Emax/Emin <5 with Emin being the minimum secant elastic modulus in tension, that is to say the slope of the straight line connecting the origin of the stress-elongation curve (0%; OMPa) obtained under the conditions of standard ASTM D 2969 - 04 of 2014 and Emax being the maximum tangent modulus of the same force-elongation curve; And - the reinforced product (R) has a structural elongation As such that 0<As<3% determined by standard ASTM D2969-04 of 2014. Reinforced product (R) according to the preceding claim, in which the metal reinforcement elements (54 ) defining an internal vault (58) of the cable with a diameter Dv, each metal reinforcement element (54) having a diameter Df and a helix radius of curvature Rf defined by Rf=P/(ïT x Sin(2a)) with P the pitch of each metallic reinforcement element expressed in millimeters and a the helix angle of each metallic reinforcement element (54) and Dv=Dh-Df, in which Dv, Dh and Df being expressed in millimetres:

1.30 < Dv / Df < 4.50. Reinforced product (R) according to the preceding claim, in which 9 <Rf/Df <30. Reinforced product (R) according to any one of the preceding claims, in which the total elongation At >1.5% determined by the standard ASTM D2969-04 of 2014. A reinforced product (R) according to any preceding claim, wherein the helix diameter Dh of each metal reinforcing member (54) is such that 0.70 mm < Dh < 1 , 60 mm, preferably 0.75 mm <Dh <1.60 mm and more preferably 0.80 mm <Dh <1.60 mm. Reinforced product (R) according to any one of the preceding claims, in which Df is such that 0.10 mm < Df < 0.50 mm, preferably 0.15 mm < Df < 0.50 mm and more preferably 0, 15mm<Df<0.45mm. Reinforced product (R) according to any one of Claims 2 to 6, in which Dv is such that Dv > 0.40 mm, preferably 0.50 mm < Dv < 1.20 mm. Reinforced product (R) according to any one of claims 2 to 7, in which each metallic reinforcing element (54) is wound at a pitch P such that 3 mm < P < 15 mm, preferably 5 mm < P < 13 mm and more preferably 7 mm < P < 11 mm, Reinforced product (R) according to any one of the preceding claims, in which D < 2.10 mm, preferably 0.90 mm < D < 2.10 mm and more preferably 0.95 mm<D<2.05 mm. Reinforced product (R) according to any one of claims 1 to 9, in which each metallic reinforcing element (54) of the cable (50) is a metallic wire (F) with N ranging from 3 to 18 and preferably from 4 15. Reinforced product (R) according to any one of claims 1 to 9, in which each metallic reinforcing element (54) of the cable (50') is a strand (T) with N ranging from 3 to 5, M ranges from 3 to 18 and preferably from 4 to 15. Reinforced product (R) according to the preceding claim, in which the strands (T) define an internal vault (V) of the cable (50') of diameter Dvc, each strand (T) having a diameter D and a radius of curvature of helix Rt defined by Rt=Pe/(ïT x Sin(2ae)) with Pe the pitch of each strand expressed in millimeters and ae the helix angle of each strand (T), Dvc, D and Rt being expressed in millimeters , the cable (50') satisfying the following relationships: 5<Rt/D<550 and 0.10<Dvc/D<0.50. Reinforced product (R) according to the preceding claim, in which the pitch of each strand Pe ranges from 20 mm to 120 mm. Tire (P), characterized in that it comprises at least one reinforced product (R) according to any one of Claims 1 to 13. Tire (P), according to the preceding claim, comprising a crown (12) comprising a strip (20) and a crown reinforcement (14), two sidewalls (22), two beads (24), each sidewall (22) connecting each bead (24) to the crown (12), the crown reinforcement (14 ) extending in the crown (12) in a circumferential direction (Z) of the tire (P), the tire (P) comprising a carcass reinforcement (32) anchored in each of the beads (24) and extending in the sidewalls (22) and in the crown (12), the crown reinforcement (14) being radially interposed between the carcass reinforcement (32) and the tread (20), the crown reinforcement (14) comprising at least one reinforced product (R) according to any one of claims 1 to 13.