AU2022270964A1 - Two-layer multi-strand cable having improved surface fracture energy - Google Patents

Abstract

The invention relates to a multi-strand cable (50) comprising: an inner cable layer (Cl) consisting of K=1 inner strand (Tl) having three layers (C1, C2, C3), namely an inner layer (C1) consisting of Q inner metal wires (F1), an intermediate layer (C2) and an outer layer (C3) consisting of N outer metal wires (F3); and an outer cable layer (CE) consisting of L>1 outer strands (TE) having two layers (C1', C3'), wound around the inner cable layer (Cl), namely an inner layer (C1) consisting of Q' inner metal wires (FT) and an outer layer (C3') consisting of N' outer metal wires (F3'). The cable (50) has a surface fracture energy ES > 175 N.mm-1 with ES = (I), wherein (II) is the sum of the forces at rupture for Nc wires, (III) is the sum of the total elongation of the Nc wires, Cfrag is the weakening coefficient of the cable (50), and D is the diameter of the cable (50).

Description

TWO-LAYER MULTI-STRAND CABLE HAVING IMPROVED SURFACE FRACTURE ENERGY

[0001] The invention relates to cords and to a tyre comprising these cords.

[0002] A tyre for a construction plant vehicle, having a radial carcass reinforcement comprising a tread, two inextensible beads, two sidewalls connecting the beads to the tread and a crown reinforcement, disposed circumferentially between the carcass reinforcement and the tread, is known from the prior art, notably from document EP2426255B1. This crown reinforcement comprises four plies reinforced by reinforcing elements such as metal cords, the cords of one ply being embedded in an elastomer matrix of the ply.

[0003] This crown reinforcement comprises several working plies comprising several filamentary reinforcing elements. Each working filamentary reinforcing element is a two-layer multi-strand cord having an internal layer of the cord made up of K=1 three-layer internal strand comprising an internal layer made up of Q=3 internal metallic threads of diameter dl=0.40 mm, an intermediate layer M=9 intermediate metallic threads of diameter d2=0.40 mm wound around the internal layer and an external layer made up of N=15 external metallic threads of diameter d3=0.40 mm wound around the intermediate layer; an external layer of the cord made up of L=8 two-layer external strands comprising an internal layer made up of Q'=3 internal metallic threads of diameter dl'=0.35 mm and an external layer made up of N'=9 external metallic threads of diameter d3'=0.35 mm wound around the internal layer. The diameter of the unwrapped cord is equal to 5.27 mm for a force at break of 36 128 N.

[0004] On the one hand, as the tyre passes over obstacles, for example in the form of rocks, these obstacles risk perforating the tyre as far as the crown reinforcement. These perforations allow corrosive agents to enter the crown reinforcement of the tyre and reduce the life thereof.

[0005] On the other hand, it has been found that the cords of the crown plies may exhibit breakages resulting from relatively significant deformations and loads applied to the cord, notably as the tyre passes over obstacles.

[0006] One subject of the invention is a cord that makes it possible to reduce, or even to eliminate, the number of breakages and the number of perforations.

[0007] To this end, one subject of the invention is a two-layer multi-strand cord comprising: - an internal layer of the cord made up of K=1 three-layer internal strand comprising: - an internal layer made up of (a) Q internal metallic thread(s), - an intermediate layer made up of M intermediate metallic threads wound around the internal layer, and

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- an external layer made up of N external metallic threads of diameter d3 wound around the intermediate layer, - an external layer of the cord made up of L>1 two-layer external strands wound around the internal layer of the cord, comprising: - an internal layer made up of Q'=2, 3 or 4 internal metallic threads, and - an external layer made up of N' external metallic threads of diameter d3'wound around the internal layer, in which the cord has an energy-to-break per unit area ES 175 N.mm- with ES= E 1F x EA1 / Nc x Cfrag / D where:

- F, is the sum of the forces at break for the Nc threads, in Newtons; - Nc = Q+M+N+L x(Q'+N') is the total number of metallic threads; - D is the diameter of the cord, in mm;

- iE A is the sum of the total elongation of the Nc threads, and is dimensionless; - Cfrag is the dimensionless coefficient of weakening of the cord, with

sin(ocf) ( +NI Fmi)X sin (at) Cfag = 1 d3xd3r N x Cste where:

d3 and d3'are expressed in mm, af is the angle of contact between the external metallic threads of the internal strand and the external metallic threads of the external strands, expressed in radians, at is the helix angle of each external strand (TE) expressed in radians; Cste = 1500 N.mm 2 .

[0008] Because it has a relatively high energy-to-break per unit area, the cord according to the invention makes it possible to reduce perforations and therefore lengthen the life of the tyre and also reduce the number of breakages. Specifically, the inventors behind the invention have discovered that the determining criterion for reducing cord breakages was not only the force at break as widely taught in the prior art, but the energy-to-break per unit area which in the present application is represented by an indicator equal to the product of the force at break, the elongation at break, and the coefficient of weakening of the cord, divided by the diameter of the cord.

[0009] The coefficient of weakening makes it possible to take account of the loss of tensile behaviour of the cord caused by transverse weakening in inter-thread contacts at the level of the external metallic threads of the internal layer and of the external layer. This coefficient of weakening is dependent on the number of external metallic threads in the internal layer, on the angle of contact between the internal strand and the or each external strand, on the diameters d3 and d3' of the external metallic threads of the internal layer and of the external metallic threads of the external layer, respectively, on the helix angle of an external strand and on the 20252004_1 (GHMatters) P122747.AU force at break of an external strand. Thus, a robust cord will have a coefficient of weakening close to 1 and a weakened cord will have a suboptimal coefficient of weakening rather closer to 0.5.

[0010] Specifically, the cords of the prior art have either a force at break that is relatively high but a coefficient of weakening that is not optimal, such as Example 2 of EP2426255B1, or an optimal coefficient of weakening, namely one close to 1, but a force at break that is relatively low. In both instances, the cords of the prior art have a relatively low energy-to-break per unit area. The cord according to the invention, because of its relatively high coefficient of weakening and its relatively high force at break, exhibits a relatively high energy-to-break per unit area.

[0011] Any range of values denoted by the expression "between a and b" represents the range of values extending from more than a to less than b (namely excluding the end-points a and b), whereas any range of values denoted by the expression "from a to b" means the range of values extending from the end-point "a" as far as the end-point "b", namely including the strict end-points "a" and "b".

[0012] By definition, the diameter of a strand is the diameter of the smallest circle inside which the strand is circumscribed.

[0013] By definition, the diameter of the cord is the diameter of the smallest circle inside which the cord without the wrapper is circumscribed.

[0014] In the invention, the cord has two layers of strands, which means to say that it comprises an assembly made up of two layers of strands, neither more nor less, which means to say that the assembly has two layers of strands, not one, not three, but only two.

[0015] In one embodiment, the internal strand of the cord is surrounded by a polymer compound followed by the external layer.

[0016] Advantageously, the internal strand has cylindrical layers.

[0017] Advantageously, each external strand has cylindrical layers.

[0018] Highly advantageously, the internal strand and each external strand have cylindrical layers. It will be recalled that such cylindrical layers are obtained when the various layers of the strand are wound at different pitches and/or when the directions of winding of these layers differfrom one layerto the other.Astrand with cylindrical layers is very highly penetrable, unlike a strand with compact layers in which the pitches of all the layers are the same and the directions of winding of all the layers are the same, thereby exhibiting far lower penetrability.

[0019] The internal strand is a three-layer strand. The internal strand comprises a collection of threads which is made up of three layers of threads, neither more nor less, which means to say that the collection of threads has three layers of threads, not two, not four, but only three.

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[0020] The external strand is a two-layer strand. The external strand comprises a collection of threads which is made up of two layers of threads, neither more nor less, which means to say that the collection of threads has two layers of threads, not one, not three, but only two.

[0021] It will be recalled that, as is known, the pitch of a strand represents the length of this strand, measured parallel to the axis of the cord, after which the strand that has this pitch has made a complete turn around the said axis of the cord. Similarly, the pitch of a thread represents the length of this thread, measured parallel to the axis of the strand in which it is located, after which the thread that has this pitch has made a complete turn around the said axis of the strand.

[0022] What is meant by the direction of winding of a layer of strands or of threads is the direction that the strands or the threads form with respect to the axis of the cord or of the strand. The direction of winding is commonly designated by the letter Z or S.

[0023] The pitches, directions of winding, and diameters of the threads and of the strands are determined in accordance with standard ASTM D2969-04 of 2014.

[0024] The angle of contact between the external metallic threads of the internal strand and the external metallic threads of the external strands is the angle af indicated in Figure 6. In this schematic depiction of the cord according to the invention, the axis A-A' of the cord, around which the internal layer and the external layer are wound, has been indicated. In this depiction, only 2 metallic threads of the external layer of the external strand have been retained, in order better to see the angle af which is the angle of contact between the external metallic thread of the internal strand and the external metallic thread of the external strand. This is one of the relevant parameters in determining the coefficient of weakening of the cord because the smaller the angle of contact the less the weakening of the cord.

[0025] The helix angle of each external strand at is a parameter well known to those skilled in the art and can be determined using the following calculation: tan at = 2xt x Re/pe, in which formula pe is the pitch expressed in millimetres at which each external strand is wound, re is the radius of the helix of each external strand, expressed in millimetres, and tan refers to the tangent function. at is expressed in degrees.

[0026] By definition, the helix radius Re of the external layer of the cord is the radius of the theoretical circle passing through the centres of the external strands of the external layer in a plane perpendicular to the axis of the cord.

[0027] The total elongation At, a parameter well known to those skilled in the art, is determined for example by applying standard ASTM D2969-04 from 2014 to a thread that is tested in such a way as to obtain a force - elongation curve. The At is deduced from the curve obtained as being the elongation, in %, corresponding to the projection onto the elongation axis of the point

20252004_1 (GHMatters) P122747.AU on the force - elongation curve at which the thread breaks, namely the point at which the load increases to a maximum value of force at break (Fm) and then decreases sharply after breakage. When the decrease with respect to Fm exceeds a certain level, that means that breakage of the thread has occurred.

[0028] For preference, the strands do not undergo pre-shaping.

[0029] Advantageously, the cord is made of metal. The term "metal cord" is understood by definition to mean a cord formed of threads made up predominantly (i.e. more than 50% of these threads) or entirely (100% of the threads) of a metallic material. Such a metallic material is preferably implemented using a material made of steel, more preferably of pearlitic (or ferritic-pearlitic) carbon steel referred to as "carbon steel" below, or else of stainless steel (by definition steel comprising at least 11% chromium and at least 50% iron). However, it is of course possible to use other steels or other alloys.

[0030] When a carbon steel is advantageously used, its carbon content (% by weight of steel) is preferably comprised between 0.4% and 1.2%, notably between 0.5% and 1.1%; these contents represent a good compromise between the mechanical properties required for the tyre and the workability of the threads.

[0031] The metal or the steel used, whether in particular it is a carbon steel or a stainless steel, may itself be coated with a metal layer which, for example, improves the workability of the metal cord and/or of its constituent elements, or the use properties of the cord and/or of the tyre themselves, such as properties of adhesion, corrosion resistance or resistance to ageing. According to one preferred embodiment, the steel used is covered with a layer of brass (Zn Cu alloy) or of zinc.

[0032] For preference, the threads of the one same layer of a predetermined (internal or external) strand all have substantially the same diameter. Advantageously, the external strands all have substantially the same diameter. What is meant by "substantially the same diameter" is that the threads or the strands have the same diameter to within the industrial tolerances.

[0033] Advantageously, the external strands are wound in a helix around the internal strand with a pitch pe ranging from 40 mm to 100 mm and preferably ranging from 50 mm to 90 mm.

[0034] The cord according to the invention has an energy per unit area that is greatly improved by comparison with the cord of the prior art which has an energy per unit area of 171 N.mm-. The inventors behind the invention postulate the theory that the more inter-thread contacts there are, more particularly in the inter-strand areas which are the most stressing, namely the more contact there is between the external metallic threads of the internal strand and the external metallic threads of the external strands, the more the weakening load is diluted across the number of contacts. This contact load is dependent on the load that each strand is able to

20252004_1 (GHMatters) P122747.AU react, namely on the cord loading divided by the number of strands. In order to optimize these contacts, the inventors behind the invention are postulating the theory that it is necessary to have good geometric properties in the contact and more specifically in the angle of contact between the external metallic threads of the internal strand and the external metallic threads of the external strands in order to optimize the contacts inside the cord.

[0035] Avantageously, ES 180 N.mm-1 and for preference ES 185 N.mm-1.

[0036] Advantageously, the force at break Fr =EN F, x Cfrag is such that Fr - 25 000 N, for preference Fr 26 000 N and more preferably Fr 28 000 N. The force at break is measured in accordance with standard ASTM D2969-04. As described above, the cord has a relatively high force at break so as to maximize the energy-to-break per unit area.

[0037] Another subject of the invention is a cord extracted from a polymer matrix, the cord comprising: - an internal layer of the cord made up of K=1 three-layer internal strand comprising: - an internal layer made up of (a) Q internal metallic thread(s), - an intermediate layer made up of M intermediate metallic threads wound around the internal layer, and - an external layer made up of N external metallic threads of diameter d3 wound around the intermediate layer, - an external layer of the cord made up of L>1 two-layer external strands wound around the internal layer of the cord, comprising: - an internal layer made up of Q'=2, 3 or 4 internal metallic threads, and - an external layer made up of N' external metallic threads of diameter d3'wound around the internal layer, in which the extracted cord has an energy-to-break ES' 170 N.mm1 ES'= xwith A/ Nc x Cfrag'/ D where: FxNS

- EFItis the sum of the forces at break for the Nc threads, in Newtons; - Nc = Q+M+N+L x(Q'+N') is the total number of metallic threads; - D is the diameter of the cord, in mm;

- >El1Ais the sum of the total elongation of the Nc threads, and is dimensionless; - Cfrag' is the dimensionless coefficient of weakening of the cord, with

Cfrag' = 1 - (2 - Cp) xN )S ((at) where:

Cp is the penetration coefficient for the cord d3 and d3'are expressed in mm, af is the angle of contact between the external metallic threads of the internal strand and the external metallic threads of the external strands, expressed in radians, 20252004_1 (GHMatters) P122747.AU at is the helix angle of the external strands, expressed in radians; Cste = 1500 N.mm-2

.

[0038] For preference, ES' 175 N.mm-1, and more preferably ES' 180 N.mm-1.

[0039] The total elongation At of the extracted cord is measured in a similar way to the total elongation At of the cord defined hereinabove.

[0040] The coefficient of weakening Cfrag' takes account of the extent to which the polymer matrix penetrates the cord, through use of the inter-strand penetration coefficient Cp. In order to calculate this penetration coefficient, a transverse cross section is performed on the cord extracted using a saw. This operation is repeated ten times in order to obtain ten transverse cross sections on which a mean penetration coefficient Cp will be calculated. An electron microscope is then used to observe the regions of filling with the polymer compound of each extracted cord, using image-processing software to quantify the ratio of the non-metal surface area without polymer compound to the surface area filled with polymer compound in the zone of contact between the external strands and the internal strand. Thus, a well-penetrated cord will have a penetration coefficient close to 1 and a cord that is less well penetrated will have a penetration coefficient close to 0.5.

[0041] For preference, the polymer matrix is an elastomer matrix.

[0042] The polymer matrix, preferably elastomer matrix, is based on a polymer, preferably elastomer, compound.

[0043] What is meant by a polymer matrix is a matrix containing at least one polymer. The polymer matrix is thus based on a polymer compound.

[0044] What is meant by an elastomer matrix is a matrix containing at least one elastomer. The preferred elastomer matrix is thus based on the elastomer compound.

[0045] The expression "based on" should be understood as meaning that the compound comprises the mixture and/or the product of the in situ reaction of the various constituents used, some of these constituents being able to react and/or being intended to react with one another, at least partially, during the various phases of manufacture of the compound; it being possible therefore for the compound to be in the fully or partially crosslinked state or in the non-crosslinked state.

[0046] What is meant by a polymer compound is that the compound contains at least one polymer. For preference, such a polymer may be a thermoplastic, for example a polyester or a polyamide, a thermosetting polymer, an elastomer, for example natural rubber, a thermoplastic elastomer or a combination of these polymers.

[0047] What is meant by an elastomer compound is that the compound contains at least one elastomer and at least one other component. For preference, the compound containing at least

20252004_1 (GHMatters) P122747.AU one elastomer and at least one other component contains an elastomer, a crosslinking system, and a filler. The compounds that can be used for these plies are conventional compounds for the skim coating of filamentary reinforcing elements and comprise a diene elastomer, for example natural rubber, a reinforcing filler, for example carbon black and/or silica, a crosslinking system, for example a vulcanizing system, preferably containing sulfur, stearic acid and zinc oxide, and possibly a vulcanization accelerant and/or retarder and/or various additives. The adhesion between the metallic threads and the matrix in which they are embedded is afforded for example by a metallic coating, for example a layer of brass.

[0048] The values of the features described in the present application for the extracted cord are measured on or determined from cords extracted from a polymer matrix, notably an elastomer matrix, for example of a tyre. Thus, for example on a tyre, the strip of material radially on the outside of the cord that is to be extracted is removed in order to be able to see the cord that is to be extracted radially flush with the polymer matrix. This removal can be done by stripping using cutters and grippers, or else by planing. Next, the end of the cord that is to be extracted is uncovered using a knife. The cord is then pulled so as to extract it from the matrix, applying a relatively shallow angle in order not to plasticize the cord that is to be extracted. The extracted cords are then carefully cleaned, for example using a knife, so as to detach any remains of polymer matrix locally adhering to the cord, while taking care not to damage the surface of the metallic threads.

[0049] Advantageously, the extracted cord exhibits a force at break Fr'such that Fr' =7EF x Cfrag' such that Fr' 24 000 N, for preference Fr' 25 000 N and more preferably Fr' 27 000 N. The force at break is measured on the extracted cord in accordance with standard ASTM D2969-04.

[0050] The advantageous features described hereinbelow apply equally to the cord as defined above and to the extracted cord.

[0051] For preference, the cord has a diameter D such that D 5 6.0 mm, preferably such that 4.0 mm 5 D 5 5.5 mm. The diameter D is measured on the cord in accordance with standard ASTM D2969-04.

[0052] For preference, af is greater than or equal to 0° and preferably greater than or equal to 50.

[0053] For preference, af is less than or equal to 250 and preferably less than or equal to 200.

[0054] Over this range of angle of contact ranging from 00 to 250, the region of contact is maximized and the cord is relatively well penetrated by the polymer compound.

[0055] For preference, at is greater than or equal to 00 and preferably greater than or equal to 50.

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[0056] For preference, at is less than or equal to 200, preferably less than or equal to 150 and more preferably less than or equal to 100.

[0057] Over this range of helix angles, the loads of contact between external strands and the internal strand when tension is applied to the cord are minimized.

[0058] For preference, dl, d1', d2, d3, d3'range, independently of one another, from 0.25 mm to 0.50 mm, preferably from 0.30 mm to 0.45 mm and more preferably from 0.32 mm to 0.42 mm.

[0059] Advantageously, the external layer of the cord is saturated such that the inter-strand distance for the external strands defined, on a cross section of the cord perpendicular to the main axis of the cord, as being the shortest distance separating, on average, the circular envelopes in which two adjacent external strands are inscribed, is strictly less than 20 pm.

[0060] By definition, a saturated layer of cord is such that the inter-strand distance for the external strands is strictly less than 20 pm. The inter-strand distance of the external layer of external strands is defined, on a cross section of the cord perpendicular to the main axis of the cord, as being the shortest distance separating, on average, the circular envelopes in which two adjacent external strands are inscribed. Thus, this construction of the cord makes it possible to ensure good architectural stability of the external layer and the saturation of the external layer makes it possible to ensure that the external layer comprises a relatively high number of external strands and therefore exhibits a relatively high force at break.

[0061] The inter-strand distance E is the distance between the 2 centres of 2 adjacent external strands, the points A and B as shown in Figure 7, minus the diameter of the external strand.

[0062] As a preference, the threads of the one same layer of a predetermined (internal or external) strand all have substantially the same diameter. Advantageously, the external strands all have substantially the same diameter. What is meant by "substantially the same diameter" is that the threads or the strands have the same diameter give or take the industrial tolerances.

[0063] For that, working in an orthonormal 2D frame of reference, which is to say along the cross section of the cable, and taking OA as the direction of the abscissa axis, where 0 is the centre of the cord and considering the case where the external strands all have substantially the same diameter, the coordinates of the centres of 2 strands A and B are calculated: A=

[ReTE, 0], B= [ReTE X coS (2r/L); ReTE x sin( 2r/L)], where L is the number of external strands, ReTE is the helix radius of each external strand expressed in millimetres.

[0064] The helix radius of each external strand is calculated using the following formula: ReTE

= max (Re-minTE ; ReTEunsaturated) where ReminTE is the radius of winding that is obtained if the layer is oversaturated. This is the minimum radius for all the strands to be in contact.

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Re_min TE = 1/[( sin 2(rr/L)/DTE2) 2 -C 2(rr/L) x (2 r/pe)2 where L is the number of external strands, pe is the pitch, expressed in millimetres, at which each external strand is wound and DTE is the diameter of the external strand in millimetres, and ReTE unsaturated correspondsto an unsaturated or strictlysaturated architecture, Re TE unsaturated=

DT/2 + DTE/ 2 where DTI is the diameter of the internal strand in mm et DTE is the diameter of the external strand in millimetres.

[0065] The diameter of the external strand is calculated as follows: DTE=2 x Rel' + d1' + 2 x d3'where Re' is the radius of winding of the internal layer of the external strand, where - if the internal layer of the external strand contains 1 single internal metallic thread: Rel'= 0 - else Rel'= 1/[( sin2(rr/Q')/dl'/2)2-cos2(rr/Q') x (2 r/pl')2 where Q' is the number of metallic threads in the internal layer of the external strand, d1' is the diameter of the metallic threads of the internal layer of the external strand in mm, and the pitch p1' is the pitch of the internal layer of the external strand in millimetres.

[0066] Next, the distance AB in a frame of reference is calculated using the following formula: AB= [(xb-xa) 2 + (yb-ya) 2 ] 11 2 and the inter-strand distance E=AB-DTE/ coS (at) X 1000 in microns

is then found, where DTE is the diameter of the external strand and at= atan (2 r ReTE /pe) is the helix angle of the external strand, where pe is the pitch, expressed in millimetres, at which each external strand is wound.

[0067] By contrast, a desaturated layer of cord is such that the inter-strand distance for the external strands is greater than or equal to 20 pm.

[0068] Advantageously, the external layer of the internal strand is desaturated.

[0069] By definition, a desaturated layer is such that there is enough space left between the threads to allow a polymer compound, preferably an elastomer compound, to pass. A desaturated layer means that the threads do not touch and that there is enough space between two adjacent threads to allow a polymer compound, preferably an elastomer compound, to pass. By contrast, a saturated layer is such that there is not enough space between the threads of the layer to allow a polymer compound, preferably an elastomer compound, to pass, for example because each pair of two threads of the layer touch one another.

[0070] By definition, the inter-thread distance of a layer is defined, on a cross section of the cord perpendicular to the main axis of the cord, as being the shortest distance separating, on average, two adjacent threads of the layer.

[0071] The inter-thread distance of the layer is calculated as follows: The radius of winding of the external layers of the external strands is calculated: Re3'=Rel'+dl'/2 + d3'/2

20252004_1 (GHMatters) P122747.AU where Rel' is the radius of winding of the internal layer of the external strand as defined hereinabove.

[0072] The inter-thread distance 13'is the distance between 2 centres of metallic threads minus the thread diameter as shown in Figure 8, the method of calculation is the same as that used for the external strands: A'= [Re3 , 0] B'= [Re 3 'x cos (2r/N') ; Re3'x sin( 2r/N')] A'B'=[ (xb'-xa') 2 + (yb'-ya')2]12

[0073] This then gives 13'= A'B'-d3'/cos(aC3') x 1000 where aC3' = atan(2 r R3'/p3') is the helix angle of the external layer of the external strand.

[0074] The sum S13' is the sum of the inter-thread distances separating each pair of adjacent external threads of the external layer.

[0075] The sum S2' is the sum of the inter-thread distances separating each pair of adjacent intermediate threads of the external layer.

[0076] For preference, the strands do not undergo pre-shaping.

[0077] Advantageously, the inter-thread distance of the external layer of the internal strand is greater than or equal to 5 pm. For preference, the inter-thread distance of the external layer of the internal strand is greater than or equal to 15 pm, more preferably greater than or equal to pm, more preferably still greater than or equal to 50 pm and highly preferably greater than or equal to 60 pm.

[0078] For preference, the inter-thread distance of the external layer of the internal strand is less than or equal to 100 pm.

[0079] Advantageously, the sum S13 of the inter-thread distances 13 of the external layer of the internal strand is greater than the diameter d3 of the external threads of the external layer.

[0080] Advantageously, each strand is of the type not rubberized in situ. What is meant by not rubberized in situ is that, prior to the strands being assembled with one another, each strand is made up of the threads of the various layers and does not have any polymer compound, notably any elastomer compound.

[0081] Advantageously, the external layer of each external strand is desaturated.

[0082] Advantageously, the inter-thread distance of the external layer of each external strand is greater than or equal to 5 pm. For preference, the inter-thread distance of the external layer of each external strand is greater than or equal to 15 pm, more preferably greater than or equal to 35 pm, more preferably still greater than or equal to 50 pm and highly preferably greater than or equal to 60 pm.

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[0083] For preference, the inter-thread distance of the external layer of each external strand is less than or equal to 100 pm.

[0084] Advantageously, the sum S13' of the inter-thread distances 13' of the external layer of each external strand is greater than or equal to the diameter d3' of the external threads of the external layer.

[0085] For preference, d1, d1', d2, d3, d3' range, independently of one another, from 0.12 mm to 0.45 mm and for preference from 0.15 mm to 0.40 mm.

[0086] In one embodiment, each internal thread has a diameter dl strictly less than the diameter d3 of each external thread and for preference, dl<d2=d3. In another embodiment, in which d1=d2=d3, it is possible to limit the number of different threads to be managed in the manufacture of the cord.

[0087] For preference, the external layer of the internal strand is wound around the internal layer of the internal strand in contact with the internal layer of the internal strand.

[0088] Advantageously, L=6, 7 or 8; for preference L=6 or 7 and more preferably L=6.

[0089] For preference, K=1 and L=6. In the cord in which K=1, the most severe transverse loadings are the transverse loadings exerted by the external strands on the internal strand.

[0090] Internal strand of the cord according to the invention

[0091] In one embodiment, Q=1.

[0092] Advantageously, M=3, 4, 5 or 6 and for preference M=4, 5 or 6.

[0093] Advantageously, N=9, 10, 11 or 12.

[0094] In another preferred embodiment, Q>1 and for preference Q=2, 3 or 4.

[0095] Advantageously, M =7, 8, 9 or 10 and for preference M=7, 8 or 9.

[0096] Advantageously, N=12, 13, 14 or 15 and for preference N=12, 13 or 14.

[0097] In a first alternative form, Q=2, M=7 or 8 and N=12 or 13.

[0098] In a second alternative form, Q=3, M=8 or 9 and N=13 or 14.

[0099] In a third alternative form, Q=4, M=9 or 10 and N=12, 13 or 14, for preference Q=4, M=9 and N=14.

[0100] Highly advantageously, each internal thread of the internal strand has a diameter dl equal to the diameter d2 of each intermediate thread of the internal strand and equal to the diameter d3 of each external thread of the internal strand. Thus, the same diameter of thread is preferably used in the internal, intermediate and external layers of the internal strand, thereby limiting the number of different threads that need to be managed during the manufacture of the cord.

[0101] External strands of the cord according to the invention

[0102] Advantageously, N'=7, 8, 9 or 10 and for preference N'=8 or 9.

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[0103] In a first alternative form, Q'=2 and N'=7 or 8, for preference Q'=2, N'=7.

[0104] In a second alternative form, Q'=3 and N'=7, 8 or 9, for preference Q'=3, N'=8.

[0105] In a third alternative form, Q'=4 and N'=7, 8, 9 or 10, for preference Q'=4, N'=9.

[0106] Highly advantageously, each internal thread of the external strand has a diameter d1' equal to the diameter d3' of each external thread of the external strand. Thus, the same diameter of thread is preferably used in the internal and external layers of the external strand, thereby limiting the number of different threads that need to be managed during the manufacture of the cord.

[0107] Advantageously, Q=4, M=9 and N=14 and Q'= 4 and N'=9, and d1=d3=d1'=d3'.

[0108] REINFORCED PRODUCT ACCORDING TO THE INVENTION

[0109] Another subject of the invention is a reinforced product comprising a polymer matrix and at least one cord or extracted cord as defined above.

[0110] Advantageously, the reinforced product comprises one or several cords according to the invention embedded in the polymer matrix and, in the case of several cords, the cords are arranged side-by-side in a main direction.

[0111] TYRE ACCORDING TO THE INVENTION

[0112] Another subject of the invention is a tyre comprising at least one extracted cord or a reinforced product as defined above.

[0113] What is meant by a tyre comprising an extracted cord, is a tyre comprising a cord of which the properties, measured after extraction from the tyre, are those of the extracted cord, this cord being, prior to being incorporated into the tyre, a cord such as the cord described hereinabove.

[0114] For preference, the tyre has a carcass reinforcement anchored in two beads and surmounted radially by a crown reinforcement which is itself surmounted by a tread, the crown reinforcement being joined to the said beads by two sidewalls, and comprising at least one cord as defined above.

[0115] In one preferred embodiment, the crown reinforcement comprises a protective reinforcement and a working reinforcement, the working reinforcement comprising at least one cord as defined hereinabove, the protective reinforcement being interposed radially between the tread and the working reinforcement.

[0116] The cord is most particularly intended for industrial vehicles selected from heavy vehicles such as "heavy-duty vehicles"- i.e. underground trains, buses, road haulage vehicles (lorries, tractors, trailers), off-road vehicles, agricultural vehicles or construction plant vehicles, or other transport or handling vehicles.

[0117] As a preference, the tyre is for a vehicle of the construction plant type. Thus, the tyre

20252004_1 (GHMatters) P122747.AU has a size in which the diameter, in inches, of the seat of the rim on which the tyre is intended to be mounted is greater than or equal to 40 inches.

[0118] The invention also relates to a rubber item comprising an assembly according to the invention, or an impregnated assembly according to the invention. What is meant by a rubber item is any type of item made of rubber, such as a ball, a non-pneumatic object such as a non pneumatic tyre casing, a conveyor belt or a caterpillar track.

[0119] A better understanding of the invention will be obtained on reading the examples which will follow, given solely by way of non-limiting examples and made with reference to the drawings, in which: - Figure 1 is a view in cross section perpendicular to the circumferential direction of a tyre according to the invention; - Figure 2 is a detail view of the region II of Figure 1; - Figure 3 is a view in cross section of a reinforced product according to the invention; - Figure 4 is a schematic view in cross section perpendicular to the axis of the cord (which is assumed to be straight and at rest) of a cord (50) according to one embodiment of the invention; - Figure 5 is a schematic view in cross section perpendicular to the axis of the cord (which is assumed to be straight and at rest) of an extracted cord (50') according to one embodiment of the invention; - Figure 6 is a schematic depiction of the angle af of the cord (50) of Figure 4; and - Figure 7 is a schematic view of different geometric parameters of the cord.

[0120] EXAMPLE OF A TYRE ACCORDING TO THE INVENTION

[0121] Aframe of reference X, Y, Z corresponding to the usual respectively axial (X), radial (Y) and circumferential (Z) orientations of a tyre has been depicted in Figures 1 and 2.

[0122] The "median circumferential plane" M of the tyre is the plane which is normal to the axis of rotation of the tyre and which is situated equidistantly from the annular reinforcing structures of each bead.

[0123] Figures 1 and 2 depict a tyre according to the invention and denoted by the general reference 10.

[0124] The tyre 10 is for a heavy vehicle of construction plant type, for example of "dumper" type. Thus, the tyre 10 has a dimension of the type 53/80R63.

[0125] The tyre 10 has a crown 12 reinforced by a crown reinforcement 14, two sidewalls 16 and two beads 18, each of these beads 18 being reinforced with an annular structure, in this instance a bead thread 20. The crown reinforcement 14 is surmounted radially by a tread 22

20252004_1 (GHMatters) P122747.AU and connected to the beads 18 by the sidewalls 16. A carcass reinforcement 24 is anchored in the two beads 18 and in this instance wound around the two bead threads 20 and comprises a turnup 26 positioned towards the outside of the tyre 20, which is shown here fitted onto a wheel rim 28. The carcass reinforcement 24 is surmounted radially by the crown reinforcement 14.

[0126] The carcass reinforcement 24 comprises at least one carcass ply 30 reinforced by radial carcass cords (not depicted). The carcass cords are positioned subtantially parallel to one another and extend from one bead 18 to the other so as to form an angle comprised between 800 and 900 with the median circumferential plane M (plane perpendicular to the axis of rotation of the tyre which is situated midway between the two beads 18 and passes through the middle of the crown reinforcement 14).

[0127] The tyre 10 also comprises a sealing ply 32 made up of an elastomer (commonly known as "inner liner") which defines the radially internal face 34 of the tyre 10 and which is intended to protect the carcass ply 30 from the diffusion of air coming from the space inside the tyre 10.

[0128] The crown reinforcement 14 comprises, radially from the outside towards the inside of the tyre 10, a protective reinforcement 36 arranged radially on the inside of the tread 22, a working reinforcement 38 arranged radially on the inside of the protective reinforcement 36 and an additional reinforcement 40 arranged radially on the inside of the working reinforcement 38. The protective reinforcement 36 is thus interposed radially between the tread 22 and the working reinforcement 38. The working reinforcement 38 is interposed radially between the protective reinforcement 36 and the additional reinforcement 40.

[0129] The protective reinforcement 36 comprises first and second protective plies 42, 44 comprising protective metal cords, the first ply 42 being arranged radially on the inside of the second ply 44. Optionally, the protective metal cords make an angle at least equal to 10, preferably in the range from 10 to 35 and more preferably from 15 to 30, with the circumferential direction Z of the tyre.

[0130] The working reinforcement 38 comprises first and second working plies 46, 48, the first ply 46 being arranged radially on the inside of the second ply 48. Each ply 46, 48 comprises at least one cord 50. Optionally, the working metal cords 50 are crossed from one working ply to the other and make an angle at most equal to 60, preferably in the range from 15 to 40, with the circumferential direction Z of the tyre.

[0131] The additional reinforcement 40, also referred to as a limiting block, the purpose of which is to absorb in part the mechanical stresses of inflation, comprises, for example and as known per se, additional metallic reinforcing elements, for example as described in FR 2 419 181 or FR 2 419 182, making an angle at most equal to 10, preferably in the range from 5 to

20252004_1 (GHMatters) P122747.AU

, with the circumferential direction Z of the tyre 10.

[0132] EXAMPLE OF A REINFORCED PRODUCT ACCORDING TO THE INVENTION

[0133] Figure 3 depicts a reinforced product according to the invention and denoted by the general reference 100. The reinforced product 100 comprises at least one cord 50, in this instance several cords 50, embedded in the polymer matrix 102.

[0134] Figure 3 depicts the polymer matrix 102, the cords 50 in a frame of reference X, Y, Z, in which the direction Y is the radial direction and the directions X and Z are the axial and circumferential directions. In Figure 3, the reinforced product 100 comprises several cords 50 arranged side-by-side in the main direction X and extending parallel to one another within the reinforced product 100 and collectively embedded in the polymer matrix 102. In this instance, the polymer matrix 102 is an elastomer matrix based on an elastomer compound.

[0135] CORD ACCORDING TO A FIRST EMBODIMENT OF THE INVENTION

[0136] Figure 4 depicts the cord 50 according to a first embodiment of the invention.

[0137] With reference to Figure 5, each protective reinforcing element 43, 45 and each hoop reinforcing element 53, 55 is formed, once it has been extracted from the tyre 10, of an extracted cord 50' as described below. The cord 50 is obtained by embedding in a polymer matrix, in this instance in a polymer matrix respectively forming each polymer matrix of each protective ply 42, 44 and of each hoop layer 52, 54 in which matrix the protective reinforcing elements 43, 45 and the hoop reinforcing elements 53, 55 are respectively embedded.

[0138] The cord 50 and the extracted cord 50' are made of metal and are of the multi-strand type with two cylindrical layers. Thus, it will be understood that there are two layers, not more, not less, of strands of which the cord 50 or 50' is made.

[0139] The cord 50 or the cord 50'comprises an internal layer CI of the cord which is made up of K=1 internal strand TI. The external layer CE is made up of L>1 external strands TE wound around the internal layer CI of the cord. In this particular instance, L=6, 7 or 8; for preference L=6 or 7 and more preferably L=6 and here L=6.

[0140] The cord 50 has an energy-to-break per unit area:

[0141] ES= mIx F xE At, / Nc x Cfrag / D = ((82+ (4 +9)x 401+6 x(4+9) x401) x 0.964x

0.0282 (1- .( .40 x( 9X*°x4l 1 )/5.24=36573x 0.0282x 0.964/5.24= 190 N. mm-1 .

[0142] With Nc = Q+M+N+L x(Q'+N') = 1+4+9+6 x(4+9)=92.

[0143] EINcA / Nc=0.0282.

20252004_1 (GHMatters) P122747.AU

[0144] Fr= Z"FmxCfrag= (82+ (4 +9)x401 +6x(4+9)x401)x0.964= 36 573x0.960= 35110 N.

[0145] The cord 50 also comprises a wrapper F (not depicted) made up of a single wrapping thread.

[0146] The extracted cord 50' has an energy-to-break per unit area:

[0147] ES'= E F xEN At, / Nc x Cfrag'/ D = (82+ (4 +9)x 401 +6 x(4+9) x401) x

0.0282(1 - (2 - 0.9)x sin(S.5 7/180) (6 x(4+9)x4°1) xsin(9.T/180)/5.24 = 189 N. mm. 0.40x0.40 9 X 1500

[0148] In order to calculate Cp, software is used to determine the ratio of the non-metal surface area without polymer compound to the surface area filled with polymer compound in the zone Scp of contact between the external strands and the internal strand. Here, the ratio averaged over 10 transverse cross sections is equal to 0.9.

[0149] Fr' = ZNS Fmx Cfrag'=(82+ (4 +9)x 401 +6 x(4+9) x401)x 0.960= 35112 N.

[0150] The external layer of the cords 50 and 50' is saturated. Thus, the inter-strand distance E of the external strands is strictly less than 20 pm. Here, E=0 pm.

[0151] af is greater than or equal to 0 and preferably greater than or equal to 5 and less than or equal to 250 and preferably less than or equal to 20. Here af = 5.5°.

[0152] at is greater than or equal to 0 and preferably greater than or equal to 5 and less than or equal to 200 preferably less than or equal to 150 and more preferably less than or equal to 10. Here at = 9.10.

[0153] Internal strands TI of the cords 50 and 50'

[0154] Each internal strand TI is a three-layer strand and comprises an internal layer C1 made up of Q=1 internal metallic thread F1, an intermediate layer C2 made up of M intermediate metallic threads F2 wound around the internal layer C1 and an external layer C3 made up of N external metallic threads F3 wound around the intermediate layer C2.

[0155] Here, Q=1.

[0156] Advantageously, M=3, 4, 5 or 6 and for preference M=4, 5 or 6. Here M=4.

[0157] Advantageously, N=9, 10 or 11. Here N=9.

[0158] The external layer C3 of each internal strand TI is desaturated. The inter-thread distance of the external layer of the internal strand is greater than or equal to 15 pm, more preferably greater than or equal to 35 pm and is here equal to 71 pm. The sum S13 of the inter thread distances 13 of the external layer C3 is greater than the diameter d3 of the external threads F3 of the external layer C3. Here, the sum S13=0.71 x 9 = 0.64 mm, which is a value greater than d3 = 0.40 mm.

[0159] dl, d2 and d3 range, independently of one another, range from 0.12 mm to 0.45 mm

20252004_1 (GHMatters) P122747.AU and preferably from 0.15 mm to 0.40 mm. Here d1=0.20 mm and d2=d3=0.40 mm.

[0160] External strands TE of the cords 50 and 50'

[0161] Each external strand TE has two layers and comprises an internal layer C1' made up of (a) Q'internal metallic thread(s) F'and an external layer C3'made up of N'external metallic threads F3'wound around the internal layer C1'.

[0162] Here, Q'=4.

[0163] N' =7, 8, 9 or 10 and for preference N'=8 or 9, and here N'=9.

[0164] The external layer C3' of each external strand TE is desaturated. Because it is desaturated, the inter-thread distance 13'of the external layer C3'which on average separates the N' external threads is greater than or equal to 5 pm. The inter-thread distance 13' of the external layer of each external strand is greater than or equal to 15 pm, more preferably greater than or equal to 35 pm, more preferably still greater than or equal to 50 pm and is here equal to 0.55 pm. The sum S13' of the inter-thread distances 13' of the external layer C3' is greater than the diameter d3' of the external threads F3' of the external layer C3'. Here, the sum S13'=61 x 9 = 0.55 mm, which is a value greater than d3'= 0.40 mm.

[0165] Each internal and external layer C1', C3' of each external strand TE is wound in the same direction of winding of the cord and of the internal and external layers C1, C3 of the internal strand TI. Here, the direction of winding of each layer of the cord and of the cord itself is Z.

[0166] Each internal and external thread of each external strand TE respectively has a diameter d1' and d3'. Each internal metallic thread Fl' of each external strand TE has a diameter d1' greater than or equal to the diameter d3' of each external metallic thread F3' of each external strand TE; for preference 1.00 5 d1'/d3' 5 1.20.

[0167] d1' and d3' range, independently of one another, from 0.12 mm to 0.45 mm and preferably from 0.15 mm to 0.40 mm. Here d1'=d3'=0.40 mm.

[0168] The cords 50 and 50'are such that Q=1, M=4 and N=9 ; Q'= 4 and N'=9.

[0169] At least 50% of the metallic threads, preferably at least 60%, more preferably at least % of the metallic threads, and highly preferably each metallic thread of the cord comprises a steel core having a composition in accordance with standard NF EN 10020 of September 2000, and a carbon content C>0.80% and preferably C > 0.82% and at least 50% of the metallic threads, preferably at least 60%, more preferably at least 70% of the metallic threads, and highly preferably each metallic thread of the cord comprises a steel core having a composition in accordance with standard NF EN 10020 of September 2000, and a carbon content C 5 1.20% and preferably C 5 1.10%. Here, each metallic thread comprises a steel core having a composition in accordance with standard NF EN 10020 of September 2000, and

20252004_1 (GHMatters) P122747.AU a carbon content C=1%.

[0170] Each thread has a breaking strength, denoted Rm, such that 2500 5 Rm 3100 MPa. The steel for these threads is said to be of SHT ("Super High Tensile") grade. Other threads may be used, for example threads of an inferior grade, for example of NT ("Normal Tensile") or HT ("High Tensile") grade, just as may threads of a superior grade, for example of UT ("Ultra Tensile") or MT ("Mega Tensile") grade.

[0171] METHOD FOR MANUFACTURING THE CORD ACCORDING TO THE INVENTION

[0172] One example of a method for manufacturing the multi-strand cord 50 will now be described.

[0173] Each aforementioned internal strand is manufactured according to known methods involving the following steps, preferably performed in line and continuously: - first of all, a first step of assembling, by cabling, the Q=1 internal thread F1 of the internal layer C1 at the pitch p1 and in the Z-direction to form the internal layer C1 at a first assembling point; - followed by a second step of assembling, by cabling or by twisting, the M=4 intermediate threads F2 around the internal thread F1 of the internal layer C1 at the pitch p2 and in the Z direction to form the intermediate layer C2 at a second assembling point; - followed by a third step of assembling, by cabling or by twisting, the N=9 external threads F3 around the M intermediate threads F2 of the intermediate layer C2 at the pitch p3 and in the Z-direction to form the external layer C3 at a third assembling point; - preferably a final twist-balancing step.

[0174] Each aforementioned external strand is manufactured according to known methods involving the following steps, preferably performed in line and continuously: - first of all, a first step of assembling, by cabling, the Q'= 4 internal threads F1' of the internal layer Cl'at the pitch p1'and in the S-direction to form the internal layer Cl'at a first assembling point; - followed by a second step of assembling, by cabling or by twisting, the N'=9 external threads F3' around the Q' internal threads F1' of the internal layer Cl' at the pitch p3' and in the S direction to form the external layer C3'at a second assembling point; - preferably a final twist-balancing step.

[0175] What is meant here by "twist balancing" is, as is well known to those skilled in the art, the cancellation of the residual torque (or the elastic return of the twist) applied to each thread of the strand, in the intermediate layer as in the external layer.

[0176] After this final twist-balancing step, the manufacture of the strand is complete. Each

20252004_1 (GHMatters) P122747.AU strand is wound onto one or more receiving reels, for storage, prior to the later operation of cabling together the elementary strands in order to obtain the multi-strand cord.

[0177] In order to manufacture the multi-strand cord of the invention, the method, as is well known to those skilled in the art, is to cable or twist together the strands previously obtained, using cabling or twisting machines rated for assembling strands.

[0178] Thus, the L external strands TE are assembled around the internal strand TI at the pitch pe and in the Z-direction to form the cord 50. Possibly, in a last assembly step, the wrapper F is wound, at the pitch pf and in the S-direction, around the assembly previously obtained.

[0179] The cord 50 is then incorporated by calendering into composite fabrics formed from a known compound based on natural rubber and carbon black as reinforcing filler, conventionally used for manufacturing crown reinforcements of radial tyres. This compound essentially contains, in addition to the elastomer and the reinforcing filler (carbon black), an antioxidant, stearic acid, an extender oil, cobalt naphthenate as adhesion promoter, and finally a vulcanization system (sulfur, accelerator and ZnO).

[0180] The composite fabrics reinforced by these cords have an elastomer compound matrix formed from two thin layers of elastomer compound which are superposed on either side of the cords and which have a thickness ranging between 1 and 4 mm, respectively. The skim pitch (spacing at which the cords are laid in the elastomer compound fabric) ranges from 4 mm to 8 mm.

[0181] These composite fabrics are then used as working ply in the crown reinforcement during the method of manufacturing the tyre, the steps of which are otherwise known to a person skilled in the art.

[0182] Table 1 below summarizes the characteristics of the various cords 50 and 50'.

[Table 1]

Cords 50 50' Q/M/N 1/4/9 1/4/9 dl/d2/d3 0.20/0.40/0.40 0.20/0.40/0.40 directionfor Z/inf Z/inf Cl/pitch p1 (mm)

TI direction for Z/10 Z/14 C2/pitch p2 (mm) direction for Z/20 Z/20 C3/pitch p3 (mm)

12 (pm)/S12 (mm) 21/0.08 21/0.08

20252004_1 (GHMatters)P122747.AU

71/0.64 2/0.64 13 (pm)/S13 (mm) Q'/N' 4/9 4/9

dl'/d3' 0.40/0.40 0.40/0.40

direction for S/10 S/10 TE C1'/pitch p1'(mm) direction for S/20 S/20 C3'/pitch p3'(mm)

13'(pm)/Sl3'(mm) 61/0.55 61/0.55

Direction of cord/pi/pe Z/inf/70 Z/inf/70 K 1 1 L 6 6 E (pm) 0 0 Fm threads at 0.20 mm (N) 82 82 Fm threads at 0.40 mm (N) 401 401 D (mm) 5.24 5.24 Av. At threads 0.0282 0.0282 af(°) 5.5 5.5 at(°) 9.1 9.1 Cfrag 0.964 Penetration Coeff - 0.900 Cfrag' - 0.960 Fr(N) 35245 Fr'(N) - 35110 ES (N.mm- 1) 190 ES'(N.mm- 1) - 189

COMPARATIVE TESTS

[0183] Evaluation of the enerqy-to-break per unit area

[0184] Various control cords and cords of the prior art were simulated.

[0185] Table 2 summarizes the characteristics of the cord of the prior art EDT (Example 2 from EP2426255).

[0186] [Table 2]

20252004_1 (GHMatters)P122747.AU

Cords EDT EDT' Q/M/N 3/9/15 3/9/15 dl1/d2/d3 0.40/0.40/0.40 0.40/0.40/0.40 direction for Cl/pitch p1 Z/6 Z/6 (mm) direction for C2/pitch p2 Z/12 Z/12 TI (mm) direction for C3/pitch p3 Z/18 Z/18 (mm)

12 (pm)/S12 (mm) 14/0.13 14/0.13

13 (pm)/S13 (mm) 5/0.08 5/0.08

Q'/N' 3/9 3/9

dl'/d3' 0.35/0.35 0.35/0.35

direction for Cl'/pitch p1' Z/10 Z/10 TE (mm) direction for C3'/pitch p3' Z/20 Z/20 (mm)

13'(pm)/SI3'(mm) 23/0.20 23/0.20

Direction of cord/pi/pe Z/inf/80 Z/inf/80 K 1 1 L 8 8 E(pm) 31 31 Fm threads at 0.35 mm (N) 350 350 Fm threads at 0.40 mm (N) 300 300 D (mm) 5.27 5.27 Av. At threads 0.0250 0.0250 af (°) 24.5 24.5 at (0) 8.8 8.8 Cfrag 0.927 Penetration Coeff - 0.7 Cfrag' - 0.906 Fr(N) 35476

20252004_1 (GHMatters)P122747.AU

Fr'(N) 43644 ES (N.mm- 1) 168 ES'(N.mm- 1) - 164

[0187] Tables 1 and 2 show that cords 50 and 50'exhibit an energy-to-break per unit area that is improved with respect to the cords of the prior art EDT and EDT'. Specifically, the cords EDT and EDT'have a relatively high coefficient of weakening but a relatively low force at break leading to an energy-to-break per unit area that is not sufficient to reduce the number of breakages and the number of perforations of the cords in the tyre. Thus, the cords according to the invention have an energy-to-break per unit area ES 175 N.mm-1 that is high enough to overcome these disadvantages.

[0188] The invention is not limited to the embodiments described above.

20252004_1 (GHMatters)P122747.AU

Claims (15)

1. Two-layer multi-strand cord (50) comprising: - an internal layer (CI) of the cord made up of K=1 internal strand (TI) having three layers (C1, C2, C3) comprising: - an internal layer (Cl) made up of (a) Q internal metallic thread(s) (Fl), - an intermediate layer (C2) made up of M intermediate metallic threads (F2) wound around the internal layer (Cl), and - an external layer (C3) made up of N external metallic threads (F3) of diameter d3 wound around the intermediate layer (C2), - an external layer (CE) of the cord made up of L>1 external strands (TE) having two layers (C1', C3') wound around the internal layer (CI) of the cord, comprising: - an internal layer (Cl') made up of Q'=2, 3 or 4 internal metallic threads (Fl'), and - an external layer (C3') made up of N'external metallic threads (F3') of diameter d3'wound around the internal layer (Cl'), characterized in that the cord (50) has an energy-to-break per unit area ES - 175 N.mm-1 with ES= Y nF x

Ocj A,/ Nc x Cfrag / D where:

- Ft1F is the sum of the forces at break for the Nc threads, in Newtons; - Nc = Q+M+N+L x(Q'+N') is the total number of metallic threads; - D is the diameter of the cord, in mm;

- 'E 1 Ais the sum of the total elongation of the Nc threads, and is dimensionless; - Cfrag is the dimensionless coefficient of weakening of the cord (50), with

sin(of) E + N1 F .)X Sin (at) Cfrag = 1 d3xd3r N x Cste where:

d3 and d3'are expressed in mm, af is the angle of contact between the external metallic threads (F3) of the internal strand (TI) and the external metallic threads (F3') of the external strands (TE), expressed in radians, at is the helix angle of each external strand (TE) expressed in radians; Cste = 1500 N.mm-2; with the total elongation At being determined by applying standard ASTM D2969-04 from 2014.

2. Cord (50) according to the preceding claim, wherein ES - 180 N.mm-1 and preferably ES 185 N.mm-1.

20252004_1 (GHMatters) P122747.AU

3. Cord (50) according to either one of the preceding claims, exhibiting a force at break Fr =Z F, x Cfrag such that Fr 25 000 N, for preference Fr 26 000 N and more preferably Fr 28 000 N.

4. Cord (50') extracted from a polymer matrix, the extracted cord (50') comprising: - an internal layer (CI) of the cord made up of K=1 internal strand (TI) having three layers (C1, C3) comprising: - an internal layer (Cl) made up of (a) Q internal metallic thread(s) (Fl) - an intermediate layer (C2) made up of M intermediate metallic threads (F2) wound around the internal layer (Cl), and - an external layer (C3) made up of N external metallic threads (F3) of diameter d3 wound around the intermediate layer (C2), - an external layer (CE) of the cord made up of L>1 external strands (TE) having two layers (C1', C3') wound around the internal layer (CI) of the cord, comprising: - an internal layer (Cl') made up of Q'=2, 3 or 4 internal metallic threads (Fl'), and - an external layer (C3') made up of N'external metallic threads (F3') of diameter d3'wound around the internal layer (Cl'), characterized in that the extracted cord (50') has an energy-to-break ES' 170 N.mm-1 with ES' Yj"SF, x

_iEN A,/ Nc x Cfrag'/ D where:

- E F, is the sum of the forces at break for the Nc threads, in Newtons; - Nc = Q+M+N+L x(Q'+N') is the total number of metallic threads; - D is the diameter of the cord, in mm;

- iEiA is the sum of the total elongation of the Nc threads, and is dimensionless; - Cfrag' is the dimensionless coefficient of weakening of the cord (50'), with

Cfrag' = 1 - (2 - Cp) x X +N FX ) where: Cp is the penetration coefficient for the cord d3 and d3'are expressed in mm, af is the angle of contact between the external metallic threads (F3) of the internal strand (TI) and the external metallic threads (F3') of the external strands (TE), expressed in radians, at is the helix angle of the external strands (TE), expressed in radians; Cste = 1500 N.mm-2 with the total elongation At being determined by applying standard ASTM D2969-04 from 2014.

20252004_1 (GHMatters) P122747.AU

5. Extracted cord (50') according to the preceding claim, wherein ES' 175 N.mm-1, and more preferably ES' 160 N.mm-1.

6. Cord (50, 50') according to any one of the preceding claims, wherein the diameter D of the cord (50, 50') is such that D 5 6.0 mm, preferably such that 4.0 mm 5 D 5 5.5 mm.

7. Cord (50, 50') according to any one of the preceding claims, wherein af is greater than or equal to 0 and preferably greater than or equal to 5°.

8. Cord (50, 50') according to any one of the preceding claims, wherein af is less than or equal to 250 and preferably less than or equal to 20.

9. Cord (50, 50') according to any one of the preceding claims, wherein at is greater than or equal to 0 and preferably greater than or equal to 5°.

10. Cord (50, 50') according to any one of the preceding claims, wherein at is less than or equal to 20, preferably less than or equal to 150 and more preferably less than or equal to 100.

11. Cord (50, 50') according to any one of the preceding claims, in which the external layer (CE) of the cord is saturated such that the inter-strand distance for the external strands defined, on a cross section of the cord perpendicular to the main axis of the cord (50), as being the shortest distance separating, on average, the circular envelopes in which two adjacent external strands (TE) are inscribed, is strictly less than 20 pm.

12. Cord (50, 50') according to any one of the preceding claims, in which the external layer (C3) of the internal strand (TI) is desaturated.

13. Cord (50, 50') according to any one of the preceding claims, in which the external layer (C3') of each external strand (TE) is desaturated.

14. Reinforced product (100), characterized in that it comprises a polymer matrix (102) and at least one extracted cord (50') according to any one of Claims 4 to 13.

15. Tyre (10), characterized in that it comprises at least one extracted cord (50') according to any one of Claims 4 to 13 or a reinforced product according to Claim 14.

20252004_1 (GHMatters) P122747.AU