HOOPING REINFORCEMENT FOR A TIRE OF A HEAVY DUTY CIVIL ENGINEERING VEHICLE

Abstract

A hoop reinforcement is provided for a tire for a heavy vehicle of construction plant type. The crown reinforcement (3) of the tire (1), radially on the inside of a tread (2), comprises a protective reinforcement (6), a working reinforcement (5) and a hoop reinforcement (7). The hoop reinforcement (7) is formed by a circumferential winding, in the circumferential direction (XX), of a ply of metallic reinforcers (8) forming an angle at most equal to 2.5 with the circumferential direction (XX), extending from an initial radially inner end (81) to a final radially outer end (82), forming a spiral, such that the hoop reinforcement (7) comprises at least two hooping layers (71, 72) around the entire circumference and at least three hooping layers (71, 72, 73) over an angular sector A, delimited by the initial and final ends (81, 82), respectively, of the hoop reinforcement (7). The hoop reinforcement (7) comprises at least one discontinuity (9) positioned circumferentially between the initial end (81) and final end (82), respectively, and any discontinuity (9) is positioned circumferentially, with respect to the initial or final end (81, 82), forming an angle (B1, B2) at least equal to 90.

Claims

1.-16. (canceled)

17. A tire for a heavy vehicle of construction plant type, the tire comprising: a crown reinforcement radially on the inside of a tread and radially on the outside of a carcass reinforcement, the crown reinforcement comprising a protective reinforcement, a working reinforcement, and a hoop reinforcement, the protective reinforcement, which is radially outermost in the crown reinforcement, comprising at least one protective layer, the protective layer comprising metallic reinforcers that form an angle at least equal to 10 with a circumferential direction XX tangential to the circumference of the tire, the working reinforcement comprising at least two working layers, each working layer comprising metallic reinforcers that form an angle at least equal to 15 and at most equal to 45 with the circumferential direction XX and are crossed from one working layer to the next, and the hoop reinforcement being formed by a circumferential winding, in the circumferential direction XX, of a ply of metallic reinforcers extending from an initial radially inner end to a final radially outer end, forming a spiral, such that the hoop reinforcement comprises at least two hooping layers around the entire circumference and at least three hooping layers over an angular sector A, delimited by the initial and final ends, respectively, of the hoop reinforcement, the metallic reinforcers of the hoop reinforcement forming an angle at most equal to 2.5 with the circumferential direction XX, wherein the hoop reinforcement comprises at least one discontinuity positioned circumferentially between the initial end and the final end, respectively, and any discontinuity is positioned circumferentially, with respect to the initial end or the final end, forming an angle at least equal to 90.

18. The tire according to claim 17, wherein the hoop reinforcement comprises at least two discontinuities, which are circumferentially positioned between the initial end and the final end, respectively, and form an angle C at least equal to 90 between one another.

19. The tire according to claim 17, wherein any discontinuity has a rectilinear mean line that forms an angle D strictly less than 90 with the circumferential direction XX.

20. The tire according to claim 19, wherein any discontinuity has a rectilinear mean line that forms an angle D at least equal to 15 and at most equal to 45 with the circumferential direction XX.

21. The tire according to claim 20, wherein any discontinuity has a rectilinear mean line that forms an angle D at least equal to 25 and at most equal to 40 with the circumferential direction XX.

22. The tire according to claim 17, wherein any discontinuity has a width LD at least equal to 10 mm and at most equal to 90 mm.

23. The tire according to claim 22, wherein any discontinuity has a width LD at most equal to 70 mm.

24. The tire according to claim 17, wherein any discontinuity is formed by an elastomeric filling material having a dynamic shear modulus G.sub.R* at least equal to the dynamic shear modulus G.sub.E* of the elastomeric coating material of the metallic reinforcers of the hoop reinforcement.

25. The tire according to claim 17, wherein any discontinuity is formed by an elastomeric filling material having a composition identical to that of the elastomeric coating material of the metallic reinforcers of the hoop reinforcement.

26. The tire according to claim 17, wherein the length of the angular sector A delimited by the initial and final ends, respectively, of the hoop reinforcement is at least equal to 0.6 m.

27. The tire according to claim 17, wherein the length of the angular sector A delimited by the initial and final ends, respectively, of the hoop reinforcement is at most equal to 1.2 m.

28. The tire according to claim 17, wherein the length of the angular sector A delimited by the initial and final ends, respectively, of the hoop reinforcement is zero.

29. The tire according to claim 17, wherein the hoop reinforcement is radially comprised between two working layers of the working reinforcement.

30. The tire according to claim 17, wherein the metallic reinforcers of the hoop reinforcement are elastic.

31. The tire according to claim 30, wherein the metallic reinforcers of the hoop reinforcement are multistrand ropes of structure 1N comprising a single layer of N strands wound in a helix, each strand comprising an internal layer of M internal threads wound in a helix and an external layer of P external threads wound in a helix around the internal layer.

32. The tire according to claim 31, wherein N=3 or N=4.

33. The tire according to claim 31, wherein M=3, 4 or 5.

34. The tire according to claim 31, wherein P=7, 8, 9, 10 or 11.

35. A method of manufacturing the tire according to claim 17 comprising: a step of producing the hoop reinforcement, in which the hoop reinforcement is obtained by circumferentially winding in a spiral at least two portions of a ply of metallic reinforcers, made up of mutually parallel metallic reinforcers coated in an elastomeric coating material, and by butt welding the adjacent ends of two successive ply portions, each butt weld forming a discontinuity formed by an elastomeric filling material.

Description

[0071] The invention is illustrated in FIGS. 1 to 7, which are not depicted to scale in order to make them easier to understand:

[0072] FIG. 1 shows a cutaway perspective view of the crown of a tyre 1 according to the prior art, having: [0073] a tread 2 radially on the outside of a carcass reinforcement 4, [0074] the crown reinforcement 3 comprising a protective reinforcement 5, a working reinforcement 6 and a hoop reinforcement 7, [0075] the protective reinforcement 5, which is radially outermost in the crown reinforcement 3, comprising two protective layers (51, 52), each protective layer (51, 52) comprising metallic reinforcers that form an angle at least equal to 10 with a circumferential direction (XX) tangential to the circumference of the tyre, [0076] the working reinforcement 6 comprising two working layers (61, 62), each working layer (61, 62) comprising metallic reinforcers that form an angle at least equal to 15 and at most equal to 45 with the circumferential direction (XX) and are crossed from one working layer to the next, [0077] the hoop reinforcement 7 being formed by a circumferential winding, in the circumferential direction (XX), of a ply of metallic reinforcers 8 extending from an initial radially inner end 81 to a final radially outer end 82, forming a spiral, such that the hoop reinforcement 7 comprises at least two hooping layers (71, 72).

[0078] FIG. 2 shows a meridian section through the crown of a tyre 1 according to the invention, having: [0079] a tread 2; [0080] a carcass reinforcement 4; [0081] a crown reinforcement 3 comprising a working reinforcement 5 comprising two working layers 51 and 52, a hoop reinforcement 7 comprising a winding of two turns of circumferential reinforcers 71 and 72, and a protective reinforcement 6 comprising two protective layers 61 and 62.

[0082] FIG. 3 shows a discontinuity 9 of the hooping layer 72, the mean line of which forms an angle D with the circumferential direction XX. The hooping layer 72 is radially on the outside of the working layer 61, which is itself radially on the outside of the carcass reinforcement 4.

[0083] FIG. 4 shows the connection of the discontinuity 9 between two portions of plies of metallic reinforcers 8. This connection, realized by an elastomeric coating material, is characterized by its width LD at least equal to 10 mm and at most equal to 90 mm, and by its thickness E, which is at least equal to that of the ply of metallic reinforcers.

[0084] FIG. 5 shows the schematic diagram of the manufacture of the hoop reinforcement by winding in a spiral a ply of metallic reinforcers 8, which starts from an end 81, continues through a second turn, and then over an angular sector A in which three hooping layers (71, 72, 73) are superposed. The winding ends at an end 82.

[0085] FIG. 6 shows the invention with a second hooping layer comprising a discontinuity 9 resulting from the incorporation of a waste ply of metallic reinforcers in the second winding turn. The discontinuity 9 forms an angle B1 with the initial end 81 and forms an angle B2 with the final end 82.

[0086] FIG. 7 differs from FIG. 6 by the elimination of the overlap and by the incorporation of two waste plies of metallic reinforcers in the second winding turn. The two resulting discontinuities 91 and 92 form an angle C at least equal to 90 with one another.

[0087] The invention was carried out on a tyre for a heavy vehicle of construction plant type of size 40.00R57. The tyre according to the invention differs from the prior art tyre by the realization of the hoop reinforcement. Whereas the prior art tyre was obtained by continuous winding of the hoop through two turns, for the invention, hooping was carried out by winding a succession of portions of layers joined together by a butt connection.

[0088] The result presented in Table 1 below corresponds to the difference in cost of the hoop reinforcement of the two tyre variants:

TABLE-US-00001 TABLE 1 Prior art: Invention: spiral hoop Variant which reinforcement includes butt laid in two welds in the continuous production Differ- turns without of the hoop ence discontinuity reinforcement (%) Comments Hoop 91 86 5% The superposition rein- of the weld over forcement a length of 1 m (kg) causes a 5% increase in mass of the hoop reinforcement

[0089] By eliminating the overlaps of the hooping layers, during the production of the butt welds, the saving in material cost is estimated to be 5%.