TWO-LAYER MULTI-STRAND CABLE HAVING AN IMPROVED SURFACE ENERGY-TO-BREAK

Abstract

A multi-strand cord (50) comprises an internal layer (CI) made up of K=1 internal strand (TI) having two layers (C1, C3), with the internal layer (C1) being made up of Q internal metallic threads (F1) and the external layer (C3) being made up of N external metallic threads (F3), and an external layer (CE) made up of L>1 external strands (TE) having two layers (C1′, C3′) wound around the internal layer (CI), with the internal layer (C1′) being made up of Q′ internal metallic threads (F1′) and the external layer (C3′) being made up of N′ external metallic threads (F3′). The cord (50) has an energy-to-break per unit area ES≥145 N.Math.mm.sup.−1 with ES=Σ.sub.i=1.sup.NcF.sub.mi×Σ.sub.i=1.sup.NcA.sub.ti/Nc×Cfrag/D where Σ.sub.i=1.sup.NcF.sub.mi is the sum of the forces at break, Σ.sub.i=1.sup.NcA.sub.ti is the sum of the total elongation, Cfrag is the coefficient of weakening, and D is the diameter.

Claims

1.-15. (canceled)

16. A two-layer multi-strand cord (50) comprising: an internal layer (CI) of the cord made up of K=1 internal strand (TI) having two layers (C1, C3) comprising: an internal layer (C1) made up of Q=2, 3 or 4 internal metallic threads (F1), and an external layer (C3) made up of N external metallic threads (F3) of diameter d3 wound around the internal layer (C1); and 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 (C1′) made up of Q′=2, 3 or 4 internal metallic threads (F1′), and an external layer (C3′) made up of N′ external metallic threads (F3′) of diameter d3′ wound around the internal layer (C1′), wherein the cord (50) has an energy-to-break per unit area ES≥155 N.Math.mm.sup.−1 with ES=Σ.sub.i=1.sup.NcF.sub.mi×Σ.sub.i=1.sup.NcA.sub.ti/Nc×C.sub.frag/D where: Σ.sub.i=1.sup.NcF.sub.mi is a sum of forces at break for the Nc threads, in Newtons, Nc=Q+N+L×(Q′+N′) is the total number of metallic threads, D is the diameter of the cord, in mm, Σ.sub.i=1.sup.NcA.sub.ti is a sum of total elongation of the Nc threads and is dimensionless, and C.sub.frag is a dimensionless coefficient of weakening of the cord (50), with $C_{frag}=1-\left(\frac{\sin \left({\propto }_f\right)}{d3\times d{3}^{\prime }}\times \frac{\left({.Math.}_{i=1}^{Q^{\prime }+N^{\prime }}{F}_{mi}\right)\times \sin \left(\alpha t\right)}{N\times Cste}\right)$  where: d3 and d3′ are expressed in mm, α.sub.f is an 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, α.sub.t is a helix angle of each external strand (TE) expressed in radians, and Cste=1500 N.Math.mm.sup.−2.

17. The cord (50) according to claim 16, wherein ES≥160 N.Math.mm.sup.−1.

18. The cord (50) according to claim 16, wherein the cord (50) exhibits a force at break Fr=Σ.sub.i=1.sup.NcF.sub.mi×Cfrag such that Fr≥25,000 N.

19. A 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 two layers (C1, C3) comprising: an internal layer (C1) made up of Q=2, 3 or 4 internal metallic threads (F1), and an external layer (C3) made up of N external metallic threads (F3) of diameter d3 wound around the internal layer (C1); and 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 (C1′) made up of Q′=2, 3 or 4 internal metallic threads (F1′), and an external layer (C3′) made up of N′ external metallic threads (F3′) of diameter d3′ wound around the internal layer (C1′), wherein the extracted cord (50′) has an energy-to-break ES′≥150 N.Math.mm.sup.−1 with ES′=Σ.sub.i=1.sup.NcF.sub.mi×Σ.sub.i=1.sup.NcA.sub.ti/Nc×C.sub.frag′/D where: Σ.sub.i=1.sup.NcF.sub.mi is a sum of forces at break for the Nc threads, in Newtons, Nc=Q+N+L×(Q′+N′) is the total number of metallic threads, D is the diameter of the cord, in mm, Σ.sub.i=1.sup.NcA.sub.ti is a sum of total elongation of the Nc threads and is dimensionless, and C.sub.frag′ is the dimensionless coefficient of weakening of the cord (50′), with $C_{\mathrm{frag}}^{\prime }=1-\left(2-Cp\right)\times \left(\frac{\sin \left({\propto }_f\right)}{d3\times d{3}^{\prime }}\times \frac{\left({.Math.}_{i=1}^{Q^{\prime }+N^{\prime }}{F}_{mi}\right)\times \sin \left(\alpha t\right)}{N\times Cste}\right)$  where: Cp is the penetration coefficient for the cord, d3 and d3′ are expressed in mm, α.sub.f is an 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, α.sub.t is a helix angle of the external strands (TE), expressed in radians, and Cste=1500 N.Math.mm.sup.−2.

20. The cord (50) according to claim 16, wherein α.sub.f is greater than or equal to 0°.

21. The cord (50) according to claim 16, wherein α.sub.f is less than or equal to 25°.

22. The cord (50) according to claim 16, wherein α.sub.t is greater than or equal to 0°.

23. The cord (50) according to claim 16, wherein α.sub.t is less than or equal to 20°.

24. The cord (50) according to claim 16, wherein at least 50% of the metallic threads comprise a steel core having a composition in accordance with standard NF EN 10020 from September 2000 and a carbon content C>0.80%.

25. The cord (50) according to claim 16, wherein at least 50% of the metallic threads comprise a steel core having a composition in accordance with standard NF EN 10020 from September 2000 and a carbon content C≤1.20%.

26. The cord (50) according to claim 16, wherein the external layer (CE) of the cord is saturated, such that an inter-strand distance of the external strands is strictly less than 20 μm.

27. The cord (50) according to claim 16, wherein the external layer (C3) of the internal strand (TI) is desaturated.

28. The cord (50) according to claim 16, wherein the external layer (C3′) of each external strand (TE) is desaturated.

29. A reinforced product (100) comprising a polymer matrix (102) and at least one extracted cord (50′) according to claim 19.

30. A tire comprising at least one extracted cord (50′) according to claim 19.

31. A tire comprising the reinforced product according to claim 29.

Description

[0139] 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:

[0140] FIG. 1 is a view in cross section perpendicular to the circumferential direction of a tyre according to the invention;

[0141] FIG. 2 is a detail view of the region II of FIG. 1;

[0142] FIG. 3 is a view in cross section of a reinforced product according to the invention;

[0143] FIG. 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 a first embodiment of the invention;

[0144] FIG. 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 a first embodiment of the invention;

[0145] FIG. 6 is a view similar to that of FIG. 4 of a cord (60) according to a second embodiment of the invention;

[0146] FIG. 7 is a schematic depiction of the angle αf of the cord (50) of FIG. 4; and

[0147] FIG. 8 is a photograph of a cord (50) according to a first embodiment of the invention: and

[0148] FIG. 9 is a schematic view of different geometric parameters of the cord.

EXAMPLE OF A TYRE ACCORDING TO THE INVENTION

[0149] A frame 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 FIGS. 1 and 2.

[0150] 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.

[0151] FIGS. 1 and 2 depict a tyre according to the invention and denoted by the general reference 10.

[0152] 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 53180R63.

[0153] 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 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.

[0154] The carcass reinforcement 24 comprises at least one carcass ply 30 reinforced by radial carcass cords (not depicted). The carcass cords are positioned substantially parallel to one another and extend from one bead 18 to the other so as to form an angle comprised between 80° and 90° 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).

[0155] 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.

[0156] 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.

[0157] 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.

[0158] 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.

[0159] 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 10°, with the circumferential direction Z of the tyre 10.

[0160] Example of a Reinforced Product According to the Invention

[0161] FIG. 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.

[0162] FIG. 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 FIG. 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.

[0163] In this instance, the polymer matrix 102 is an elastomer matrix based on an elastomer compound.

[0164] Cord According to a First Embodiment of the Invention

[0165] FIG. 4 depicts the cord 50 according to a first embodiment of the invention.

[0166] With reference to FIG. 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.

[0167] 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.

[0168] 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.

[0169] The cord 50 has an energy-to-break per unit area

[00003]$ES={.Math.}_{i=1}^{Nc}{F}_{mi}\times {.Math.}_{i=1}^{Nc}{A}_{\mathrm{ti}}\times \mathrm{Cfrag}/D=\left(\left(4+9+6\times \left(4+9\right)\right)\times 401\right)\times 0.0282\times \left(1-\left(\frac{\sin \left(18.9\times \pi /180\right)}{0.4\times 0.4}\times \frac{\left(4+9\right)\times 401\times \sin (9.1\times \pi /180}{9\times 1500}\right)\right)/5.3=91\times 401\times 0.0282\times 0.879/5.3=171N.{\mathrm{mm}}^{-1}.\mathrm{Fr}={.Math.}_{i=1}^{Nc}{F}_m\times \mathrm{Cfrag}=91\times 401\times 0.879=32083N.$

[0170] The cord 50 also comprises a wrapper F (not depicted) made up of a single wrapping thread.

[0171] The extracted cord 50′ has an energy-to-break per unit area

[00004]${\mathrm{ES}}^{\prime }={.Math.}_{i=1}^{Nc}{F}_m\times {.Math.}_{i=1}^{Nc}{A}_t\times {\mathrm{Cfrag}}^{\prime }/D=\left(91\times 401\right)\times 0.0282\times \left(1-\left(2-0.9\right)\right)\times \left(\frac{\sin \left(18.9\times \pi /180\right)}{0.4\times 0.4}\times \frac{\left(4+9\right)\times 401\times \sin (9.1\times \pi /180}{9\times 1500}\right)/5.3=36491\times 401\times 0.0282\times 0.867/5.3=168N.{\mathrm{mm}}^{-1}.$

In order to calculate Cp, for example from the photograph in FIG. 8 of the cord 50′ in the composite, 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.

Fr=Σ.sub.i=1.sup.NcF.sub.m×Cfrag′=91×401×0.867=31 643 N.

[0172] 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 μm. Here, E=0 μm.

[0173] αf is greater than or equal to 0° and preferably greater than or equal to 5° and less than or equal to 25° and preferably less than or equal to 20°. Here αf=18.9°.

[0174] αt is greater than or equal to 0° and preferably greater than or equal to 5° and less than or equal to 20° preferably less than or equal to 15° and more preferably less than or equal to 10°. Here at =9.1°.

[0175] Internal Strands TI of the Cords 50 and 50′

[0176] Each internal strand TI is a two-layer strand and comprises an internal layer C1 made up of Q=2, 3 or 4 internal metallic threads F1 and an external layer C3 made up of N external metallic threads F3 wound around the internal layer C1.

[0177] Here, Q=4.

[0178] N=7, 8, 9 or 10 and for preference N=8 or 9, and here N=9.

[0179] 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 μm, more preferably greater than or equal to 35 μm, more preferably still greater than or equal to 50 μm and highly preferably greater than or equal to 60 μm and is here equal to 61 μm. The sum SI3 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 SI3=0.061×9=0.55 mm, which is a value greater than d3=0.40 mm.

[0180] Each internal and external thread of each internal strand TI respectively has a diameter d1 and d3. Each internal metallic thread F1 of each internal strand TI has a diameter d1 greater than or equal to the diameter d3 of each external metallic thread F3 of each internal strand TI; for preference 1.00≤d1/d3≤1.20.

[0181] d1 and 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. Here d1=d3=0.40 mm.

[0182] External Strands TE of the Cords 50 and 50′

[0183] Each external strand TE has two layers and comprises an internal layer C1′ made up of Q′=2, 3 or 4 internal metallic threads F1′ and an external layer C3′ made up of N′ external metallic threads F3′ wound around the internal layer C1′.

[0184] Here, Q′=4.

[0185] N′=7, 8, 9 or 10 and for preference N′=8 or 9, and here N′=9.

[0186] The external layer C3′ of each external strand TE is desaturated. Because it is desaturated, the inter-thread distance I3′ of the external layer C3′ which on average separates the N′ external threads is greater than or equal to 5 μm. The inter-thread distance I3′ of the external layer of each external strand is greater than or equal to 15 μm, more preferably greater than or equal to 35 μm, more preferably still greater than or equal to 50 μm and highly preferably greater than or equal to 60 μm and is here equal to 61 μm. The sum SI3′ of the inter-thread distances I3′ of the external layer C3′ is greater than the diameter d3′ of the external threads F3′ of the external layer C3′. Here, the sum SI3′=0.061×9=0.55 mm, which is a value greater than d3′=0.40 mm.

[0187] 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.

[0188] Each internal and external thread of each external strand TE respectively has a diameter d1′ and d3′. Each internal metallic thread F1′ 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≤d1′/d3′≤1.20.

[0189] d1′ and 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. Here d1′=d3′=0.40 mm.

[0190] The cords 50 and 50′ are such that Q=4 and N=9; Q′=4 and N′=9, and d1=d3=d1′=d3′. Here d1=d3=d1′=d3′=0.40 mm.

[0191] 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>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≤1.20% and preferably C≤1.10%. Here, each metallic thread comprises a steel core having a composition in accordance with standard NF EN 10020 of September 2000, and a carbon content C=1%.

[0192] Each thread has a breaking strength, denoted Rm, such that 2500 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.

[0193] Method for Manufacturing the Cord According to the Invention

[0194] One example of a method for manufacturing the multi-strand cord 50 will now be described.

[0195] Each aforementioned internal strand is manufactured according to known methods involving the following steps, preferably performed in line and continuously: [0196] first of all, a first step of assembling, by cabling, the Q=4 internal threads 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; [0197] followed by a second step of assembling, by cabling or by twisting, the N external threads F3 around the Q internal threads F1 of the internal layer C1 at the pitch p3 and in the Z-direction to form the external layer C3 at a second assembling point; [0198] preferably a final twist-balancing step.

[0199] Each aforementioned external strand is manufactured according to known methods involving the following steps, preferably performed in line and continuously: [0200] first of all, a first step of assembling, by cabling, the Q′=2, 3 or 4 internal threads 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; [0201] followed by a second step of assembling, by cabling or by twisting, the N′ external threads F3′ around the Q′ internal threads F1′ of the internal layer C1′ at the pitch p3′ and in the Z-direction to form the external layer C3′ at a second assembling point; [0202] preferably a final twist-balancing step.

[0203] 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.

[0204] After this final twist-balancing step, the manufacture of the strand is complete. Each 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.

[0205] 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.

[0206] 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.

[0207] 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).

[0208] 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.

[0209] 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.

[0210] Cord According to a Second Embodiment of the Invention

[0211] FIG. 6 depicts a cord 60 according to a second embodiment of the invention.

[0212] Unlike in the first embodiment described hereinabove, the cord 60 according to the second embodiment is such that Q=3 and N=8 and Q′=3 and N′=8.

[0213] Table 1 below summarizes the characteristics of the various cords 50, 50′ and 60.

TABLE-US-00001 TABLE 1 Cord 50 50′ 60 TI Q/N 4/9 4/9 3/8 d1/d3 0.40/0.40 0.40/0.40 0.40/0.40 direction for Z/10 Z/10 Z/10 C1/pitch p1 (mm) direction for Z/20 Z/20 Z/20 C3/pitch p3 (mm) I3 (μm)/SI3 (mm) 61/0.55 61/0.55 78/0.62 TE Q′/N′ 4/9 4/9 3/8 d1′/d3′ 0.40/0.40 0.40/0.40 0.40/0.40 direction for Z/10 Z/10 Z/10 C1′/pitch p1′ (mm) direction for Z/20 Z/20 Z/20 C3′/pitch p3′ (mm) I3′ (μm)/SI3′ (mm) 61/0.55 61/0.55 78/0.62 Direction of cord/pi/pe Z/inf/70 Z/inf/70 Z/inf/70 K 1 1 1 L 6 6 6 E (μm) 0 0 0 Fm (N) 401 401 401 D (mm) 5.3 5.3 4.9 Thread mean At 0.0282 0.0282 0.0282 Nc 91 91 77 αf (°) 18.9 18.9 5.4 αt (°) 9.1 9.1 8.6 Cfrag 0.879 — 0.968 Penetration Coeff — 0.9 — Cfrag′ — 0.867 — Fr (N) 32083 — 29896 Fr′ (N) — 31643 — ES (N .Math. mm.sup.−1) 171 — 173 ES′(N .Math. mm.sup.−1) — 168 —

Comparative Tests

[0214] Evaluation of the Energy-to-Break Per Unit Area

[0215] Various control cords and cords of the prior art were simulated.

[0216] Table 2 summarizes the characteristics of the control cord T1 and of the cord of the prior art EDT (Example 8 from WO2016017655).

TABLE-US-00002 TABLE 2 Cord EDT EDT′ TI Q/N 3/8 3/8 d1/d3 0.33/0.35 0.33/0.35 direction for C1/pitch p1 Z/10 Z/10 (mm) direction for C3/pitch p3 Z/20 Z/20 (mm) I3 (μm)/SI3 (mm) 53/0.42 53/0.42 TE Q′/N′ 3/9 3/9 d1′/d3′ 0.29/0.29 0.29/0.29 direction for C1′/pitch p1′ Z/10 Z/10 (mm) direction for C3′/pitch p3′ Z/20 Z/20 (mm) I3′ (μm)/SI3′ (mm) 21/0.19 21/0.19 Direction of cord/pi/pe Z/inf/70 Z/inf/70 K 1 1 L 6 6 E (μm) 98 98 Fm (N) 223 223 D (mm) 3.7 3.7 Thread mean At 0.0253 0.0253 Nc 83 83 αf (°) 9.0 9.0 αt (°) 6.7 6.7 Cfrag 0.938 — Penetration Coeff — 1 Cfrag′ — 0.938 Fr (N) 17572 — Fr′ (N) — 17572 ES (N .Math. mm.sup.−1) 120 ES′(N .Math. mm.sup.−1) — 120

[0217] Tables 1 and 2 show that cords 50, 50′ and 60 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≥150 N.Math.mm.sup.−1 that is high enough to overcome these disadvantages.

[0218] The invention is not limited to the embodiments described above.