Tire comprising cables for reinforcing the carcass having low perviousness, and textile threads associated with the carcass reinforcement

Abstract

A tire having a radial carcass reinforcement, composed of at least one layer of metal reinforcing elements, the said tire comprising a crown reinforcement, itself topped radially by a tread, the said tread being joined to two beads via two sidewalls. The metal reinforcing elements of at least one layer of the carcass reinforcement are cords exhibiting, in the permeability test, a flow rate of less than 20 cm.sup.3/min and at least one layer of the carcass reinforcement is provided, on at least one face, with textile threads exhibiting, in the permeability test, a flow rate of between 1 and 3 cm.sup.3/min.

Claims

1. A tire comprising: a radial carcass reinforcement comprising at least one layer of metal reinforcing elements wherein the metal reinforcing elements of at least one layer of the radial carcass reinforcement are cords exhibiting, in a permeability test, a flow rate of less than 20 cm.sup.3/min, and wherein at least one layer of the radial carcass reinforcement is provided, on at least one face, with textile threads exhibiting, in the permeability test, a flow rate no less than 1 cm.sup.3/min and no greater than 3 cm.sup.3/min; a crown reinforcement; and a tread radially topping the crown reinforcement and joined to two beads via two sidewalls.

2. The tire according to claim 1, wherein the metal reinforcing elements of at least one layer of the carcass reinforcement are cords comprising at least two layers, and wherein at least one inner layer is sheathed with a layer consisting of a polymer composition.

3. The tire according to claim 1, wherein the metal reinforcing elements of at least one layer of the carcass reinforcement exhibit, in the permeability test, a flow rate of less than 10 cm.sup.3/min.

4. The tire according to claim 1, wherein the textile threads exhibit a diameter of between 0.2 and 0.35 mm.

5. The tire according to claim 1, wherein the textile threads exhibiting, in the permeability test, a flow rate no less than 1 cm.sup.3/min and no greater than 3 cm.sup.3/min are parallel to one another and oriented along a direction parallel to that of the metal reinforcing elements of the at least one layer of the carcass reinforcement.

6. The tire according to claim 1, wherein the textile threads exhibiting, in the permeability test, a flow rate no less than 1 cm.sup.3/min and no greater than 3 cm.sup.3/min are oriented mainly along a direction parallel to that of the metal reinforcing elements of the at least one layer of the carcass reinforcement and wherein the said textile threads are undulating around this main direction.

7. The tire according to claim 1, wherein the textile threads exhibiting, in the permeability test, a flow rate no less than 1 cm.sup.3/min and no greater than 3 cm.sup.3/min are oriented mainly along a straight direction and wherein the textile threads form an angle with the direction of the metal reinforcing elements of the said at least one layer of the carcass reinforcement which is greater than 10.

8. The tire according to claim 1, wherein the metal reinforcing elements of at least one layer of the carcass reinforcement are layered metal cords of [L+M] or [L+M+N] construction which can be used as reinforcing element of a tire carcass reinforcement, comprising a first layer C1 having L threads of diameter d.sub.1 with L ranging from 1 to 4, surrounded by at least one intermediate layer C2 having M threads of diameter d.sub.2 wound together in a helix according to a pitch p.sub.2 with M ranging from 3 to 12, the layer C2 optionally being surrounded by an outer layer C3 of N threads of diameter d.sub.3 wound together in a helix according to a pitch p.sub.3 with N ranging from 8 to 20, and wherein a sheath composed of a crosslinkable or crosslinked rubber composition based on at least one diene elastomer covers, in the construction [L+M], the first layer C1 and, in the construction [L+M+N], at least the layer C2.

9. The tire according to claim 8, wherein the diameter of the threads of the first layer (C1) is between 0.10 and 0.5 mm and wherein the diameter of the threads of the layers (C2, C3) is between 0.10 and 0.5 mm.

10. The tire according to claim 1, wherein the crown reinforcement is formed of at least two working crown layers of inextensible reinforcing elements, crossed from one layer to the other, forming, with the circumferential direction, angles of between 10 and 45.

11. The tire according to claim 1, wherein the crown reinforcement further comprises at least one layer of circumferential reinforcing elements.

12. The tire according to claim 1, wherein the crown reinforcement is supplemented radially on the outside by at least one additional ply, known as protective ply, of elastic reinforcing elements, which are oriented, with respect to the circumferential direction, with an angle of between 10 and 45 and in the same direction as the angle formed by the inextensible elements of the working ply radially adjacent to it.

13. The tire according to claim 1, wherein the crown reinforcement additionally comprises a triangulation layer formed of metal reinforcing elements forming, with the circumferential direction, angles greater than 60.

14. A tire comprising: a carcass reinforcement comprising at least one layer of metal reinforcing elements, wherein the metal reinforcing elements of at least one layer of the carcass reinforcement are cords comprising at least two layers, at least one inner layer being sheathed with a layer consisting of a polymeric composition, and wherein at least one layer of the carcass reinforcement is provided, on at least one face, with textile threads exhibiting, in a permeability test, a flow rate no less than 1 cm.sup.3/min and no greater than 3 cm.sup.3/min; a crown reinforcement; and a tread radially topping the crown reinforcement and joined to two beads via two sidewalls.

15. The tire according to claim 14, wherein the textile threads exhibit a diameter of between 0.2 and 0.35 mm.

16. The tire according to claim 14, wherein the textile threads exhibiting, in the permeability test, a flow rate no less than 1 cm.sup.3/min and no greater than 3 cm.sup.3/min are parallel to one another and oriented along a direction parallel to that of the metal reinforcing elements of the at least one layer of the carcass reinforcement.

17. The tire according to claim 14, wherein the textile threads exhibiting, in the permeability test, a flow rate no less than 1 cm.sup.3/min and no greater than 3 cm.sup.3/min are oriented mainly along a direction parallel to that of the metal reinforcing elements of the at least one layer of the carcass reinforcement and wherein the said textile threads are undulating around this main direction.

18. The tire according to claim 14, wherein the textile threads exhibiting, in the permeability test, a flow rate no less than 1 cm.sup.3/min and no greater than 3 cm.sup.3/min are oriented mainly along a straight direction and wherein the textile threads form an angle with the direction of the metal reinforcing elements of the said at least one layer of the carcass reinforcement which is greater than 10.

19. The tire according to claim 14, wherein the crown reinforcement is formed of at least two working crown layers of inextensible reinforcing elements, crossed from one layer to the other, forming, with the circumferential direction, angles of between 10 and 45.

20. The tire according to claim 14, wherein the crown reinforcement further comprises at least one layer of circumferential reinforcing elements.

21. The tire according to claim 14, wherein the crown reinforcement is supplemented radially on the outside by at least one additional ply, known as protective ply, of elastic reinforcing elements, which are oriented, with respect to the circumferential direction, with an angle of between 10 and 45 and in the same direction as the angle formed by the inextensible elements of the working ply radially adjacent to it.

22. The tire according to claim 14, wherein the crown reinforcement additionally comprises a triangulation layer formed of metal reinforcing elements forming, with the circumferential direction, angles greater than 60.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) Other advantageous details and characteristics of embodiments of the invention will emerge below from the description of the exemplary embodiments of the invention, with reference to FIGS. 1 to 7, which represent:

(2) FIG. 1, a meridional view of a diagram of a tire according to an embodiment of the invention,

(3) FIG. 2, a half-cutaway diagrammatic representation of a carcass reinforcement layer of the tire of FIG. 1 according to a first embodiment of the invention,

(4) FIG. 3, a half-cutaway diagrammatic representation of a carcass reinforcement layer of the tire of FIG. 1 according to a second embodiment of the invention,

(5) FIG. 4, a half-cutaway diagrammatic representation of a carcass reinforcement layer of the tire of FIG. 1 according to a third embodiment of the invention,

(6) FIG. 5, a diagrammatic representation of a cross-sectional view of a carcass reinforcement cord of the tire of FIG. 1,

(7) FIG. 6, a diagrammatic representation of a cross-sectional view of a first other example of a carcass reinforcement cord according to the invention,

(8) FIG. 7, a diagrammatic representation of a cross-sectional view of a second other example of a carcass reinforcement cord according to the invention.

(9) The figures are not represented to scale in order to make them easier to understand.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

(10) In FIG. 1, the tire 1, of size 315/70 R 22.5, comprises a radial carcass reinforcement 2 anchored in two beads 3 around bead wires 4. The carcass reinforcement 2 is formed of a single layer of metal cords. The carcass reinforcement 2 is wrapped by a crown reinforcement 5, itself topped by a tread 6. The crown reinforcement 5 is formed radially, from the inside towards the outside: of a first working layer formed of non-wrapped inextensible metal cords 11.35 which are continuous over the entire width of the ply and which are oriented with an angle equal to 18, of a second working layer formed of non-wrapped inextensible metal cords 11.35 which are continuous over the entire width of the ply, which are oriented with an angle equal to 18 and which are crossed with the metal cords of the first working layer, of a protective layer formed of elastic metal cords 635.

(11) These combined layers, constituting the crown reinforcement 5, are not represented in detail in the figures.

(12) FIG. 2 illustrates a half-cutaway representation of a carcass reinforcement layer 22 according to a first embodiment of the invention. This layer is composed of metal cords 27 oriented parallel with respect to one another and held between two layers 28, 29 of rubber mixture, referred to as calendaring layers. Cotton threads 20 are deployed on the outer surface (surface which is not in contact with the metal cords) of the calendaring layer 29, which cotton threads are parallel to one another and parallel to the metal cords 27.

(13) In accordance with an embodiment of the invention, the ratio of the spacing 21 between two cotton threads 20 to the spacing 23 between the metal cords 27 of the layer of the carcass reinforcement 22 is equal to 16 and thus greater than 10.

(14) The cotton threads 20 are deployed on the surface of the carcass reinforcement layer 22 which comes into contact with the bead wire 4.

(15) FIG. 3 illustrates a half-cutaway representation of a carcass reinforcement layer 32 according to a second embodiment of the invention. As in the case of FIG. 2, this layer is composed of metal cords 37 oriented parallel with respect to one another and held between two layers 38, 39 of rubber mixture, referred to as calendaring layers. Cotton threads 30 are deployed on the outer surface (surface which is not in contact with the metal cords) of the calendaring layer 39, which cotton threads exhibit an undulation around a main or mean axis oriented parallel to the direction of the metal cords 37. In accordance with the invention, the ratio of the spacing 31 between two cotton threads 30 to the amplitude of undulation 32 is equal to 0.63 and thus between 0.5 and 1.

(16) The ratio of the spacing 31 between two cotton threads 30 to the spacing 33 between the metal cords 37 of the layer of the carcass reinforcement 32 is equal to 11 and thus greater than 10.

(17) The ratio of the period of undulation 34 to the amplitude of undulation 32 of the cotton threads 30 is equal to 5.4 and thus between 5 and 20.

(18) As in the case of FIG. 2, the cotton threads 30 are deployed on the surface of the carcass reinforcement layer 32 which comes into contact with the bead wire 4.

(19) FIG. 4 illustrates a half-cutaway representation of a carcass reinforcement layer 42 according to the invention. This layer is composed of metal cords 47 oriented parallel with respect to one another and held between two layers 48, 49 of rubber mixture, referred to as calendaring layers. Cotton threads 40 are deployed on the outer surface (surface which is not in contact with the metal cords) of the calendaring layer 49, which cotton threads form an angle 41 with the direction of the metal cords 47 equal to 35. In accordance with the invention, the angle formed by the cotton threads 40 with the direction of the metal cords 47 is greater than 10.

(20) The ratio of the spacing 42 between two textile threads, measured along a direction parallel to the direction of the metal cords 47 of the carcass reinforcement layer 42 to the spacing 43 between the reinforcing elements of the carcass reinforcement layer 42, measured along a direction perpendicular to the direction of the said reinforcing elements of the carcass reinforcement layer 42, is equal to 22 and thus greater than 10 in accordance with the invention.

(21) As in the case of FIGS. 2 and 3, the cotton threads 40 are deployed on the surface of the carcass reinforcement layer 42 which comes into contact with the bead wire 4.

(22) In the three embodiments illustrated in FIGS. 2, 3 and 4, the cotton threads 20, 30 and 40 exhibit a diameter equal to 0.23 mm.

(23) The cotton threads 20, 30 and 40 exhibit, in the permeability test, measured as described above, a flow rate equal to 2 cm.sup.3/min and thus between 1 and 3 cm.sup.3/min in accordance with the invention.

(24) FIG. 5 illustrates a diagrammatic representation of the cross-section of a carcass reinforcement cord 51 of the tire 1 of FIG. 1. This cord 51 is a non-wrapped layered cord of 1+6+12 structure, composed of a central nucleus formed of a thread 52, of an intermediate layer formed of six threads 53 and of an outer layer formed of twelve threads 55.

(25) It exhibits the following characteristics (d and p in mm): 1+6+12 structure; d.sub.1=0.20 (mm); d.sub.2=0.18 (mm); p.sub.2=10 (mm); d.sub.3=0.18 (mm); p.sub.3=10 (mm); (d.sub.2/d.sub.3)=1;
with d.sub.2 and p.sub.2 respectively the diameter and the helical pitch of the intermediate layer and d.sub.3 and p.sub.3 respectively the diameter and the helical pitch of the threads of the outer layer.

(26) The core of the cord, composed of the central nucleus formed of the thread 52 and of the intermediate layer formed of the six threads 53, is sheathed with a rubber composition 54 based on non-vulcanized diene elastomer (in the raw state). The sheathing is obtained via a head for extrusion of the core composed of the thread 52 surrounded by the six threads 53, followed by a final operation in which the 12 threads 55 are twisted or cabled around the core thus sheathed.

(27) The aptitude for penetration of the cord 51, measured according to the method described above, is equal to 95%.

(28) The elastomeric composition constituting the rubber sheath 54 is produced from a composition as described above and exhibits, in the present case, the same formulation, based on natural rubber and on carbon black, as that of the calendaring layers 28;29, 38;39 and 48;49 of the carcass reinforcement which the cords are intended to reinforce.

(29) FIG. 6 illustrates a diagrammatic representation of the cross-section of another carcass reinforcement cord 61 which can be used in a tire according to the invention. This cord 41 is a non-wrapped layered cord of 3+9 structure, composed of a central core formed of a cord composed of three threads 62 twisted around one another and of an outer layer formed of nine threads 63.

(30) It exhibits the following characteristics (d and p in mm): 3+9 structure; d.sub.1=0.18 (mm); p.sub.1=5 (mm); (d.sub.1/d.sub.2)=1; d.sub.2=0.18 (mm); p.sub.2=10 (mm);
with d.sub.1 and p.sub.1 respectively the diameter and the helical pitch of the threads of the central core and d.sub.2 and p.sub.2 respectively the diameter and the helical pitch of the threads of the outer layer.

(31) The central core composed of a cord formed of the three threads 62 was sheathed with a rubber composition 64 based on non-vulcanized diene elastomer (in the raw state). The sheathing is obtained via a head for extrusion of the cord 62, followed by a final operation in which the 9 threads 63 are cabled around the core thus sheathed.

(32) The aptitude for penetration of the cord 61, measured according to the method described above, is equal to 95%.

(33) FIG. 7 illustrates a diagrammatic representation of the cross-section of another carcass reinforcement cord 71 which can be used in a tire according to the invention. This cord 71 is a non-wrapped layered cord of 1+6 structure, composed of a central nucleus formed of a thread 72 and of an outer layer formed of six threads 73.

(34) It exhibits the following characteristics (d and p in mm): 1+6 structure; d.sub.1=0.200 (mm); (d.sub.1/d.sub.2)=1.14; d.sub.2=0.175 (mm); p.sub.2=10 (mm);
with d.sub.1 the diameter of the nucleus and d.sub.2 and p.sub.2 respectively the diameter and the helical pitch of the threads of the outer layer.

(35) The central nucleus composed of the thread 72 was sheathed with a rubber composition 74 based on non-vulcanized diene elastomer (in the raw state). The sheathing is obtained via a head for extrusion of the thread 72, followed by a final operation in which the 6 threads 73 are cabled around the nucleus thus sheathed.

(36) The aptitude for penetration of the cord 71, measured according to the method described above, is equal to 95%.

(37) Tests were carried out with tires produced according to the invention in accordance with the representation of FIGS. 1, 2 and 5, and others with two types of reference tires.

(38) The first reference tires R1 differ from the tires according to the invention by cords 51 of the carcass reinforcement not comprising the sheathing layer 54 and not comprising cotton threads on the surface of the carcass reinforcement layer.

(39) The second reference tires R2 differ from the tires according to the invention by the presence of cotton threads on the surface of the carcass reinforcement layer exhibiting diameters equal to 0.37 mm and exhibiting, in the permeability test, measured as described above, a flow rate equal to 4.2 cm.sup.3/min.

(40) Rolling drum endurance tests were carried out on a test machine which applies a load of 4415 daN and a speed of 40 km/h on the tires, with oxygen-doped inflation of the tires. The tests were carried out for the tires according to the invention with conditions identical to those applied to the reference tires. The running operations are halted as soon as the tires exhibit damage to the carcass reinforcement.

(41) The tests thus carried out showed that the distances travelled with the reference tires R2 and the tires according to the invention are equivalent and total 300 000 km, whereas the reference tires R1 travelled only 250 000 km.

(42) Other rolling endurance tests on a vehicle driving axle were carried out by applying a load of 3680 daN and a speed of 40 km/h on the tires, with an inflation of the tires of 0.2 bar. The tests were carried out for the tires according to the invention with conditions identical to those applied to the reference tires. The running operations are carried out over a distance of 12 000 km or are halted as soon as the tires exhibit damage to the carcass reinforcement.

(43) The tests thus carried out showed that the distances travelled during each of these tests with the reference tires R2 and the tires according to the invention always made it possible to reach the 12 000 km, whereas the reference tires R1 travelled at most only 10 000 km.

(44) These first two tests, representative of conditions of use of the tires, demonstrate that the presence of the cords 51 of the carcass reinforcement comprising a sheathing layer 54 in combination with cotton threads present on the surface of the carcass reinforcement layer result in an improvement in the endurance of the tires.

(45) A third test, corresponding to severe conditions of use of the tires, was carried out. These tests are also carried out with the tires according to the invention and the reference tires R2. After a preliminary phase of stoving lasting twelve 12 weeks under a pure oxygen atmosphere, the tires are run on a rolling drum under conditions of load 20% greater than the nominal load and of inflation 20% greater than the nominal pressure.

(46) The tests thus carried out showed that the distances travelled during this test with the reference tires R2 are 15% less than those obtained with the tires according to the invention.

(47) These results demonstrate that the decrease in the flow rate measured according to the permeability test of the cotton threads deployed on the surface of the carcass reinforcement layer makes it possible to regain a performance in terms of endurance which is similar to that of the normal tires, in particular under particularly severe running conditions.