Hybrid reinforcing element with differential twist

Abstract

A reinforcing element includes a single strand of high-modulus textile monofilaments and a single strand of low-modulus textile monofilaments. The strand of high-modulus textile monofilaments and the strand of low-modulus textile monofilaments are wound around each other in a direction D3 with a twist R3. The strand of high-modulus textile monofilaments has a residual twist R1 in a direction D1. The strand of low-modulus textile monofilaments has a residual twist R2 in a direction D2. The residual twists R1 and R2 have a relationship such that: when R2 is substantially non-zero, R1>R2, and when R2 is substantially zero, R1 is substantially non-zero.

Claims

1. A reinforcing element comprising: a single strand of high-modulus textile monofilaments; and a single strand of low-modulus textile monofilaments, wherein the strand of high-modulus textile monofilaments and the strand of low-modulus textile monofilaments are wound around each other in a direction D3 with a twist R3, wherein the strand of high-modulus textile monofilaments has a residual twist R1 in a direction D1, wherein the strand of low-modulus textile monofilaments has a residual twist R2 in a direction D2, wherein the residual twists R1 and R2 have a relationship such that: when R2 is substantially non-zero, R1>R2, and when R2 is substantially zero, R1 is substantially non-zero, and wherein the directions D1, D2, and D3 are identical when R2 is substantially non-zero, and the directions D1 and D3 are identical when R2 is substantially zero.

2. The reinforcing element according to claim 1, wherein the high-modulus textile monofilaments are made of an aromatic polyamide.

3. The reinforcing element according to claim 1, wherein the low-modulus textile monofilaments: are made of a material selected from a group including: celluloses, polyvinyl alcohols, polyketones, aliphatic polyamides, polyesters, polybenzazoles, and polyimides, or are a mixture of monofilaments each made of a material selected from the group.

4. The reinforcing element according to claim 1, wherein R3 is in a range of from 200 twists per meter to 450 twists per meter.

5. The reinforcing element according to claim 1, wherein a twist factor of the reinforcing element is in a range of from 130 to 200.

6. The reinforcing element according to claim 1, wherein R1 is in a range of from 10 twists per meter to 150 twists per meter.

7. The reinforcing element according to claim 1, wherein, when R2 is substantially non-zero, R2 is in a range of from 10 twists per meter to 100 twists per meter.

8. The reinforcing element according to claim 1, wherein a ratio R1/R3 is in a range of from 0.05 to 0.45.

9. The reinforcing element according to claim 1, wherein a product R1R3 is greater than or equal to 3000.

10. The reinforcing element according to claim 1, wherein: a ratio R3/R2 is in a range of from 0.10 to 10.50, and R3 is in a range of from 200 twists per meter to 450 twists per meter.

11. The reinforcing element according to claim 1, wherein a ratio R1/R2 is in a range of from 1.90 to 10.00.

12. The reinforcing element according to claim 1, wherein a count T1 of the strand of high-modulus textile monofilaments is in a range of from 90 tex to 400 tex.

13. The reinforcing element according to claim 1, wherein a count T2 of the strand of low-modulus textile monofilaments is in a range of from 80 tex to 350 tex.

14. A semifinished product, comprising: a reinforcing element according to claim 1; and an elastomer, wherein the reinforcing element is embedded in a matrix of the elastomer.

15. A tire comprising a reinforcing element according to claim 1.

16. The tire according to claim 15, further comprising: two beads, each of the beads including an annular reinforcing structure; and a carcass reinforcement anchored in each of the beads by a turnup around the annular reinforcing structure, wherein the carcass reinforcement includes the at least one reinforcing element.

17. A method of manufacturing a reinforcing element, the method comprising steps of: obtaining a strand of high-modulus textile monofilaments having an initial twist R1 in a direction D1; obtaining a strand of low-modulus textile monofilaments having an initial twist R2 in a direction D2; and winding the strand of high-modulus textile monofilaments and the strand of low-modulus textile monofilaments around each other in a direction D3 with a twist R3 so that: the strand of high-modulus textile monofilaments has a residual twist R1 in a direction D1, and the strand of low-modulus textile monofilaments has a residual twist R2 in a direction D2, wherein the residual twists R1 and R2 have a relationship such that: when R2 is substantially non-zero, R1>R2, and when R2 is substantially zero, R1 is substantially non-zero, and wherein the directions D1, D2, and D3 are identical when R2 is substantially non-zero, and the directions D1 and D3 are identical when R2 is substantially zero.

18. The method according to claim 17, wherein R1<R2.

19. The method according to claim 17, wherein R1<R3.

20. The method according to claim 17, wherein D1 and D2 are identical.

21. A reinforcing element comprising: a single strand of high-modulus textile monofilaments; and a single strand of low-modulus textile monofilaments, wherein the strand of high-modulus textile monofilaments and the strand of low-modulus textile monofilaments are wound around each other in a direction D3 with a twist R3, wherein the strand of high-modulus textile monofilaments has a residual twist R1 in a direction D1, wherein the strand of low-modulus textile monofilaments has a residual twist R2 in a direction D2, wherein the residual twists R1 and R2 have a relationship such that: when R2 is substantially non-zero, R1>R2, and when R2 is substantially zero, R1 is substantially non-zero, and wherein a twist factor of the reinforcing element is in a range of from 130 to 200.

22. A reinforcing element comprising: a single strand of high-modulus textile monofilaments; and a single strand of low-modulus textile monofilaments, wherein the strand of high-modulus textile monofilaments and the strand of low-modulus textile monofilaments are wound around each other in a direction D3 with a twist R3, wherein the strand of high-modulus textile monofilaments has a residual twist R1 in a direction D1, wherein the strand of low-modulus textile monofilaments has a residual twist R2 in a direction D2, wherein the residual twists R1 and R2 have a relationship such that: when R2 is substantially non-zero, R1>R2, and when R2 is substantially zero, R1 is substantially non-zero, and wherein, when R2 is substantially non-zero, R2 is greater than or equal to 20 twists per meter.

23. A reinforcing element according to claim 22, wherein a ratio R1/R3 is in a range of 0.13 to 0.36, wherein a ratio R3/R2 is in a range of from 2 to 8.25, wherein R3 is in a range of from 250 twists per meter to 400 twists per meter, wherein a ratio R1/R2 is in a range of from 1.90 to 5, and wherein a product R1R3 is greater than or equal to 15000.

24. A reinforcing element according to claim 22, wherein a ratio R1/R3 is in a range of 0.20 to 0.35, wherein a ratio R3/R2 is in a range of from 2 to 7.10, wherein R3 is in a range of from 280 twists per meter to 400 twists per meter, wherein a ratio R1/R2 is in a range of from 1.90 to 2.5, and wherein a product R1R3 is greater than or equal to 15000.

25. A reinforcing element according to claim 24, wherein a count T1 of the strand of high-modulus textile monofilaments is in a range of 100 to 350 tex, and wherein a count T2 of the strand of low-modulus textile monofilaments is in a range of 90 to 290 tex.

26. A reinforcing element according to claim 24, wherein a count T1 of the strand of high-modulus textile monofilaments is in a range of 140 to 210 tex, and wherein a count T2 of the strand of low-modulus textile monofilaments is in a range of 120 to 190 tex.

27. A reinforcing element according to claim 24, wherein the high-modulus textile monofilaments have a final modulus greater than 25 cN/tex, wherein the low-modulus textile monofilaments have a final modulus less than or equal to 25 cN/tex.

28. A reinforcing element according to claim 22, wherein a ratio R1/R2 is in a range of from 1.90 to 2.5.

29. A reinforcing element according to claim 22, wherein, when R2 is substantially non-zero, R2 in a range of from 20 twists per meter to 60 twists per meter.

30. The reinforcing element according to claim 22, wherein the low-modulus textile monofilaments are made of a material selected from a group including: celluloses, polyvinyl alcohols, polyketones, aliphatic polyamides, polybenzazoles, and polyimides.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will be better understood from reading the following description, which is given solely by way of non-limiting example and with reference to the drawings in which:

(2) FIG. 1 is a view in radial section of a tire designed to run flat according to a first embodiment of the invention;

(3) FIG. 2 illustrates a detail view of a reinforcing element of the tire of FIG. 1;

(4) FIGS. 3 and 4 are views similar to that of FIG. 1 of tires respectively according to second and third embodiments; and

(5) FIG. 5 represents forceelongation curves for various reinforcing elements.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

(6) When using the term radial, a distinction should be made between several different uses of the word by the person skilled in the art. Firstly, the expression refers to a radius of the tire. It is in that sense that a point A is said to be radially inside a point B (or radially on the inside of the point B) if it is closer to the axis of rotation of the tire than is the point B. Conversely, a point C is said to be radially outside a point D (or radially on the outside of the point D) if it is further from the axis of rotation of the tire than is the point D. Progress radially inwards (or outwards) will mean progress towards smaller (or larger) radii. It is this sense of the word that applies also when radial distances are being discussed.

(7) On the other hand, a reinforcing element or a reinforcement is said to be radial when the reinforcing element or the reinforcing elements of the reinforcement make an angle greater than or equal to 65 and less than or equal to 90 with the circumferential direction.

(8) Finally, a radial cross section or radial section here means a cross section or a section in a plane which contains the axis of rotation of the tire.

(9) An axial direction is a direction parallel to the axis of rotation of the tire. A point E is said to be axially inside a point F (or axially on the inside of the point F) if it is closer to the median plane of the tire than is the point F. Conversely, a point G is said to be axially outside a point H (or axially on the outside of the point H) if it is further from the median plane of the tire than is the point H.

(10) The median plane of the tire is the plane which is perpendicular to the axis of rotation of the tire and which lies at equal distances from the annular reinforcing structures of each bead.

(11) A circumferential direction is a direction which is perpendicular both to a radius of the tire and to the axial direction.

(12) Examples of a Tire According to the Invention

(13) FIG. 1 schematically depicts, viewed in radial section, a tire according to a first embodiment of the invention denoted by the general reference 10. The tire 10 is of the run-flat type. The tire 10 is for a passenger vehicle.

(14) The tire 10 comprises a crown 12 comprising a crown reinforcement 14 comprising a working reinforcement 15 comprising two working plies 16, 18 and a hooping reinforcement 17 comprising a hooping ply 19. The crown reinforcement 14 is surmounted by a tread 20. Here, the hooping reinforcement 17 is arranged radially on the outside of the working reinforcement 15. The hooping reinforcement 17 is interposed radially between the working reinforcement 15 and the tread 20. Two self-supporting sidewalls 22 extend the crown 12 radially inwards.

(15) The tire 10 further comprises two beads 24 radially on the inside of the sidewalls 22 and each comprising an annular reinforcing structure 26, in this instance a bead wire 28, surmounted by a mass of bead apex filling rubber 30, and also a radial carcass reinforcement 32.

(16) The carcass reinforcement 32 preferably comprises a single carcass ply 34 of reinforcing elements 36, the carcass reinforcement 32 being anchored in each of the beads 24 by a turn-up around the annular reinforcing structure 26, so as to form, within each bead 24, a main strand 38 extending from the beads through the sidewalls towards the crown, and a turn-up 40, the radially outer end 42 of the turn-up 40 being substantially midway up the height of the tire. The carcass reinforcement 32 extends from the beads 24 through the sidewalls 22 towards the crown 12. The crown reinforcement 14 is arranged radially on the outside of the carcass reinforcement 32. Thus, the crown reinforcement 14 is radially interposed between the carcass reinforcement 32 and the tread 20.

(17) The rubber compositions used for the crown plies 16, 18 and carcass ply 34 are conventional compositions for the calendering of reinforcing elements, typically based on natural rubber, carbon black, a vulcanization system and the usual additives. The textile reinforcing element and the rubber composition which coats it are bonded together for example using a standard adhesive of RFL type.

(18) The tire 10 also comprises two sidewall inserts 44, arranged axially on the inside of the carcass reinforcement 32. These inserts 44 with their characteristic crescent-shaped radial cross section are intended to reinforce the sidewall. They comprise at least one polymer composition, preferably a rubber blend. Document WO 02/096677 gives several examples of rubber blends that can be used to form such an insert. Each sidewall insert 44 is capable of helping to support a load corresponding to a portion of the weight of the vehicle during a run-flat situation.

(19) The tire also comprises an airtight inner layer 46, preferably made of butyl, located axially on the inside of the sidewalls 22 and radially on the inside of the crown reinforcement 14 and extending between the two beads 24. The sidewall inserts 44 are located axially on the outside of the inner layer 46. Thus, the sidewall inserts 44 are positioned axially between the carcass reinforcement 32 and the inner layer 46.

(20) The hooping ply 19 comprises hooping textile reinforcing elements 36 according to the invention that form an angle of at most equal to 10, preferably ranging from 5 to 10, with the circumferential direction Z of the tire 10. As an alternative, reinforcing elements not in accordance with the invention could be used. Such reinforcing elements comprise, for example, two strands of textile monofilaments made of a heat-shrink material, for example in this instance of polyamide-6,6, each strand consisting of two 140-tex spun yarns which have been twisted together (on a direct cabling machine) at 250 twists/meter.

(21) The carcass ply 34 comprises textile reinforcing elements 36 according to the invention, one of which is illustrated in FIG. 2. The reinforcing elements 36 are parallel to one another. Each reinforcing element 36 is radial. In other words, each reinforcing element 36 extends in a plane substantially parallel to the axial and radial directions of the tire 10.

(22) Each reinforcing element 36 comprises a single high-modulus strand 54 of textile monofilaments, here made of an aromatic polyamide, for example of aramid, and a single low-modulus strand 56 of textile monofilaments, here made of polyester or of aliphatic polyamide, for example of polyester, wound together in a helix one around the other in a direction D3 with a twist R3. Each reinforcing element 36 is made up of a strand 54 and of a strand 56.

(23) Here, the direction D3 is the S direction. The twist R3 of the reinforcing element 56 ranges from 200 to 450 twists per meter, preferably from 250 to 400 twists per meter, more preferably from 280 to 400 twists per meter, and here R3=340 twists per meter.

(24) The polyester is selected from polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, polybutylene naphthalate, polypropylene terephthalate or polypropylene naphthalate. In this instance, the polyester is polyethylene terephthalate (PET).

(25) The count T1 of the high-modulus strand 54 of monofilaments ranges from 90 to 400 tex, preferably from 100 to 350 tex, and more preferably from 140 to 210 tex. Here, T1=167 tex. The count T2 of the low-modulus strand 56 of monofilaments ranges from 80 to 350 tex, preferably from 90 to 290 tex, and more preferably from 120 to 190 tex. Here, T2=144 tex.

(26) The high-modulus strand 54 of monofilaments has a substantially non-zero residual twist R1 in the direction D1. The low-modulus strand 56 of monofilaments has a residual twist R2 in the direction D2. According to the invention, R1>R2 when R2 is substantially non-zero, and R1 is substantially non-zero when R2 is substantially zero.

(27) The residual twist R1 of the high-modulus strand 54 of monofilaments ranges from 10 to 150 twists per meter, preferably from 20 to 120 twists per meter, and more preferably from 50 to 110 twists per meter. Here, R1=100 twists per meter.

(28) The residual twist R2 of the low-modulus strand 56 of monofilaments ranges from 10 to 100 twists per meter, preferably from 15 to 75 twists per meter, and more preferably from 20 to 60 twists per meter so that the condition R1>R2 or R1>0 is met, depending on whether R2 is substantially non-zero or zero. Here, R2=50 twists per meter.

(29) Here, since R2 is substantially non-zero, D1 and D2 are identical. Preferably, D1, D2 and D3 are identical and in this instance are the S direction.

(30) When R2 is substantially zero, D1 and D3 are identical.

(31) The ratio R1/R3 ranges from 0.05 to 0.45, preferably from 0.10 to 0.40, preferably from 0.13 to 0.40, more preferably from 0.13 to 0.36 and more preferably still, from 0.20 to 0.35. Here, R1/R3=0.29.

(32) The product R1.Math.R3 is greater than or equal to 3000, preferably greater than or equal to 15000, preferably greater than or equal to 30000. Here R1.Math.R3=34000. In other embodiments, R1.Math.R3 is greater than or equal to 44000. The product R1.Math.R3 is less than or equal to 48000.

(33) The reinforcing element 36 is such that the ratio R3/R2 and the value of R3 satisfy R3/R2 ranging from 0.10 to 10.50 and R3 ranging from 200 to 450 twists per meter, preferably R3/R2 ranging from 2.00 to 8.25 and R3 ranging from 250 to 400 twists per meter, preferably R3/R2 ranging from 2.00 to 7.10 and R3 ranging from 280 to 400 twists per meter. More preferably still, R3/R2 and R3 satisfy R3/R2 ranging from 3.20 to 8.75 and R3 ranging from 235 to 375 twists per meter. Here, R3/R2=6.80, for R3=340 twists per meter.

(34) Furthermore, the reinforcing element 36 is such that the ratio R1/R2 ranges from 1.90 to 10.00, preferably from 1.90 to 5.00 and more preferably from 1.90 to 2.50. Here, R1/R2=2.00.

(35) The reinforcing element 36 has a twist factor K ranging from 130 to 200, preferably from 140 to 190. Here, K=160.

(36) The final modulus Mf1 of the high-modulus strand 54 of textile monofilaments is greater than or equal to 30 cN/tex, preferably greater than or equal to 35 cN/tex and more preferably greater than or equal to 40 cN/tex. Here, Mf1=64.5 cN/tex.

(37) The final modulus Mf2 of the low-modulus strand 56 of textile monofilaments is greater than or equal to 20 cN/tex, preferably greater than or equal to 15 cN/tex and more preferably greater than or equal to 10 cN/tex. Here, Mf2=7.1 cN/tex.

(38) The ratio Mf1/Mf2 of the final modulus of the high-modulus strand 54 of textile monofilaments to the final modulus of the low-modulus strand 56 of textile monofilaments is greater than or equal to 2, preferably greater than or equal to 5, and more preferably greater than or equal to 7. For preference, Mf1/Mf2 is less than or equal to 15 and preferably less than or equal to 10. Here, Mf1/Mf2=9.1.

(39) The force at break of the reinforcing element 36 is greater than or equal to 30 daN, preferably greater than or equal to 35 daN. Here, Fr=37.5 daN on the reinforcing element 36 coated with a layer of adhesive, for example a layer of adhesive of RFL type and Fr=38.1 daN on the loomstate reinforcing element 36 with no layer of adhesive.

(40) The values described above are measured on direct-from-manufacture reinforcing elements. As an alternative, the values described above are measured on reinforcing elements extracted from a semifinished product or from a tire.

(41) FIGS. 3 and 4 depict tires according to second and third embodiments of the invention respectively. Elements similar to those of the first embodiment are denoted by identical references.

(42) Unlike the tire 10 of the first embodiment, the tire 10 according to the second embodiment in FIG. 3 is not designed to run flat. Therefore it does not have the sidewall inserts 44.

(43) In an alternative form, the tire 10 of the second embodiment comprises hoop reinforcing elements according to the invention. In another alternative form, the tire 10 of the second embodiment comprises hoop reinforcing elements not in accordance with the invention.

(44) Unlike the tire of the second embodiment, the tire 10 according to the third embodiment in FIG. 4 comprises a sidewall reinforcement 48 preferably comprising a single sidewall reinforcing ply 50.

(45) The sidewall reinforcement 48 is arranged axially on the outside of the main strand 38 and extends, within each bead 24, axially on the outside of the turnup 40 of the carcass ply 34. As an alternative, the sidewall reinforcement 48 may be arranged radially between the main strand 38 and the turnup 40 of the carcass ply 34.

(46) The radially inner end 52 of the sidewall reinforcement 48 is radially on the inside of the radially outer end 53 of the turnup 40 of the carcass reinforcement 32. The radially outer end 54 of the sidewall reinforcement 25 is axially on the inside of the axially outer end 55 of the crown ply radially adjacent to the sidewall reinforcement 48, in this instance the radially innermost working ply 18. Other configurations of the ends 52 and 54 with respect to the ends 53 and 55 are possible and described for example in WO2014040976.

(47) In this third embodiment, the sidewall reinforcement comprises reinforcing elements according to the invention.

(48) It is also possible to conceive of a tire according to the third embodiment comprising hooping reinforcing elements which may or may not be in accordance with the invention and carcass reinforcing elements which may or may not be in accordance with the invention.

(49) Method of Manufacturing the Reinforcing Element

(50) A method of manufacturing a reinforcing element 36 will now be described. The method according to the invention can be implemented using ring-type threading machines well known to those skilled in the art but can also be implemented using direct cabling machines.

(51) In a step of obtaining the high-modulus strand 54 of textile monofilaments, the starting point is a high-modulus spun yarn of textile monofilaments and this spun yarn is twisted in a direction D1 with an initial twist of R1. This yields the strand 54.

(52) In another step, this time of obtaining the low-modulus strand 56 of textile monofilaments, the starting point is a low-modulus spun yarn of textile monofilaments and this spun yarn is twisted in a direction D2 with an initial twist of R2. This yields the strand 56.

(53) Each spun yarn (more properly referred to as yarn), in the initial state, which means to say without any twist; is formed in the well-known way of a plurality of elementary textile monofilaments, typically several tens to several hundreds, of very fine diameter generally less than 25 m. Within each strand 54, 56, the textile monofilaments find themselves deformed into a helix around the axis of the fiber strand.

(54) D1 and D2 are identical and here are the Z direction. In addition, R1<R2 where here R1=240 twists per meter and R2=290 twists per meter.

(55) The high-modulus and low-modulus strands 54, 56 of textile monofilaments are then wound around one another in a direction D3 with a twist R3 so that, on the one hand, the high-modulus strand of textile monofilaments has a residual twist R1, in this instance substantially non-zero, in a direction D1 and, on the other hand, the low-modulus strand of textile monofilaments has a residual twist R2 in a direction D2. The residual twists R1 and R2 are such that R1>R2 when R2 is substantially non-zero, and R1 is substantially non-zero when R2 is substantially zero. In this instance, in the example of the reinforcing element 36, R1>R2.

(56) To this end, the strands 54, 56 are wound with a twist R3 such that R1<R3 and R2<R3 and where here R3=340 twists per meter in the direction D3 which is the opposite of the directions D1 and D2.

(57) Comparative Tests and Measurements

(58) Characteristics of the reinforcing element 36 according to the invention, of another reinforcing element 37 according to the invention, and of other reinforcing elements that act as comparative examples are compared in Table 1. For all these reinforcing elements, T1=167 tex and T2=144 tex. The PET is marketed by the company Hyosung under the trade name HSP40 NAA. The aramid is marketed by the company Teijin under the trade name Twaron 1000.

(59) The breaking strengths, determined in accordance with the standard ASTM D 885/D 885MA of January 2010, are measured at 20 C. on loomstate reinforcing elements, (which means to say elements with no adhesive) which have been subject to prior conditioning. Prior conditioning means the storage of the reinforcing elements (after drying) for at least 24 hours, prior to measurement, in a standard atmosphere in accordance with European standard DIN EN 20139 (temperature of 20+/2 C.; relative humidity of 65+/2%).

(60) The count (or linear density) of the elementary strands or of the reinforcing elements is determined in accordance with standard ASTM D1423. The count is given in tex (weight, in grams, of 1000 m of productremembering that: 0.111 tex is equal to 1 denier).

(61) The endurance is determined by conducting a bending endurance test in accordance with ASTM D430-06 (method A), during which test a semifinished product comprising several reinforcing elements embedded in an elastomer matrix is made to move back and forth in contact with a pulley. After 600 000 cycles, the reinforcing elements are extracted from the elastomer matrix and the force at break Ft is measured. This force at break Ft is compared with the force at break Fr before the bending endurance test. The % dropoff Dt is given by the difference relationship (1Ft/Fr).Math.100, and the endurance is given by the relationship 100.Math.Ft/Fr and is reported in Table 1.

(62) FIG. 5 gives the force-elongation curves CI to CV, C36 and C37 of various comparative reinforcing elements I to V, 36 and 37 according to the invention.

(63) TABLE-US-00001 TABLE 1 I II III IV V 36 37 Curve C.sub.I C.sub.II C.sub.III C.sub.IV C.sub.V C.sub.36 C.sub.37 R1 (t .Math. m.sup.1)/D1 290/Z 290/Z 240/Z 240/Z 340/Z 240/Z 240/Z R2 (t .Math. m.sup.1)/D2 290/Z 290/Z 240/Z 240/Z 340/Z 290/Z 290/Z R1 (t .Math. m.sup.1)/D1 0/S 50/S 100/S 50/S 0/S 100/S 50/S R2 (t .Math. m.sup.1)/D2 0/S 50/S 100/S 50/S 0/S 50/S 0/S R3 (t .Math. m.sup.1)/D3 290/S 340/S 340/S 290/S 340/S 340/S 290/S Twist factor 136 160 160 136 160 160 136 Endurance 100 NM NM 94 >100 170 100 Force at break (daN) 38.3 36.6 36.5 38.3 36.8 38.1 39.8

(64) The indication NM indicates that the value was not measured.

(65) A comparison between the reinforcing elements I and V illustrates the known effect of the twist R3 on the force at break and endurance mentioned in the preamble of the present application. By increasing from R3=290 t.Math.m.sup.1 (I) to R3=340 t.Math.m.sup.1 (VI), the endurance is improved, but the force at break of the reinforcing element is reduced.

(66) A comparison between the reinforcing elements I, II and III shows that two residual twists R1, R2, such that R1=R2, do not make it possible to compensate for the drop in force at break which is associated with the increase in twist R3 of the reinforcing element.

(67) A comparison between the reinforcing elements I and IV shows that two residual twists R1, R2, such that R1=R2, while keeping a twist R3 identical to the reinforcing element I lead to a force at break that remains the same, but with still a drop in endurance.

(68) A comparison between the reinforcing elements I and 36 shows that, in accordance with the invention, two residual twists R1, R2, with R1 such that R1>R2, make it possible to obtain both a force at break that is equivalent to that of the control I and an endurance that is very markedly improved by comparison with that of the control I because of a twist R3=340 t.Math.m.sup.1 higher than that of the control (R3=290 t.Math.m.sup.1).

(69) A comparison between the reinforcing elements I and 37 shows that, in accordance with the invention, two residual twists R1, R2, with R1 such that R1>R2, make it possible to obtain both an endurance that is equivalent to that of the control I and a force at break that is improved because of a twist equal to that of the control I (R3=290 t.Math.m.sup.1).

(70) A comparison between the reinforcing elements IV and 37 shows that, for the same twist R3=290 t.Math.m.sup.1, the substantially non-zero two residual twists R1, R2 such that R1=R2 of the reinforcing element IV lead to a drop in endurance by comparison with the control I unlike the reinforcing element 37 in which, for this same twist R3=290 t.Math.m.sup.1, R1>R2 allows the force at break to be improved without reducing the endurance.

(71) The invention is not limited to the embodiments described above.

(72) Specifically, the carcass reinforcement 32 of the tire could comprise two carcass plies 34.

(73) An embodiment could also be conceived of in which the turnup 40 extends up between the crown ply 18, and the main strand 38.

(74) It will also be possible to combine the characteristics of the various embodiments described or envisaged above, with the proviso that these characteristics are compatible with one another.