Tread Layer For An Aircraft Tire

Abstract

A tire for an aeroplane with the tread (2) comprising two shoulder ribs (6) having an axial width L.sub.S, each shoulder rib (6) comprises cavities (8) that open onto the tread surface (3), forming an opening surface (81) inscribed in a circle of diameter D. These cavities (8) are distributed circumferentially at a circumferential spacing P and along a periodic curve (9) having a period T and an amplitude A. The circumferential spacing P between two consecutive cavities (8) is at most equal to 0.2 times the period T of the periodic curve (9), the period T of the periodic curve (9) is at most equal to the circumferential length L.sub.C of the contact patch (31), and the amplitude A of the periodic curve (9) is at most equal to 0.5 times the axial width L.sub.S of the shoulder rib (6).

Claims

1. Tire for an aeroplane, comprising: a tread adapted to come into contact with the ground via a tread surface over a contact patch of circumferential length L.sub.C and axial width L.sub.A when the tire inflated to its recommended nominal pressure is subjected to a radial deflection equal to 32%; the tread extending radially from a bottom surface to the tread surface over a radial height H, extending axially from a first tread edge to a second tread edge, and extending circumferentially around the entire periphery of the tire; the tread comprising two axially external circumferential ribs referred to as shoulder ribs, each extending axially from a tread edge to a circumferential groove over an axial width L.sub.S, wherein each shoulder rib comprises cavities that open onto the tread surface, forming an opening surface inscribed in a circle of diameter D, in that the cavities of each shoulder rib are distributed circumferentially at a circumferential spacing P, wherein the cavities of each shoulder rib are positioned circumferentially along a periodic curve having a period T and an amplitude A, wherein the circumferential spacing P between two consecutive cavities is at most equal to 0.2 times the period T of the periodic curve, wherein the period T of the periodic curve is at most equal to the circumferential length L.sub.C of the contact patch and wherein the amplitude A of the periodic curve is at most equal to 0.5 times the axial width L.sub.S of the shoulder rib.

2. The aeroplane tire according to claim 1, wherein the circumferential spacing P between two consecutive cavities is at least equal to twice the diameter D of the opening surface of a cavity.

3. The aeroplane tire according to claim 1, wherein the diameter D of the opening surface of a cavity is at least equal to 2 mm.

4. The aeroplane tire according to claim 1, wherein each cavity is a cylinder having a radial height H.sub.C.

5. The aeroplane tire according to claim 4, wherein the radial height H.sub.C of each cavity is at most equal to the radial height H of the tread.

6. The aeroplane tire according to claim 1, wherein the periodic curve is a broken line.

7. The aeroplane tire according to claim 1, the tread comprising at least one axially internal circumferential rib extending axially from a first circumferential groove to a second circumferential groove, wherein each shoulder rib comprises groove-edge cavities that open onto the tread surface and onto the circumferential groove adjacent to the shoulder rib, wherein the at least one axially internal circumferential rib comprises groove-edge cavities that open onto the tread surface and onto each of the circumferential grooves adjacent to the axially internal rib, wherein the groove-edge cavities formed in the shoulder ribs and in the at least one axially internal circumferential rib form mutually parallel rows of cavities that are inclined at an angle at least equal to 45° with respect to the circumferential direction (XX′) of the tire, and wherein the rows of cavities are distributed circumferentially around at least a part of the periphery of the tire at a circumferential spacing P1 at least equal to 0.02 times and at most equal to 0.12 times the circumferential length of the periphery of the tire.

8. The aeroplane tire according to claim 7, wherein the rows of cavities are inclined at an angle at least equal to 80° with respect to the circumferential direction.

9. The aeroplane tire according to claim 1, wherein the diameter D of the opening surface of a cavity is at least equal to 5 mm.

Description

[0057] In order to make the invention easier to understand, FIGS. 1 to 4 have not been drawn to scale but in a simplified manner

[0058] FIG. 1 shows a meridian section through the crown of an aeroplane tire 1 according to the invention, i.e. a section in a meridian plane (YY′, ZZ′), in which the directions YY′ and ZZ′ are the axial and radial directions, respectively, of the tire. The tread 2, which is intended to come into contact with the ground via the tread surface 3, extends radially from the bottom surface 4 to the tread surface 3 over a radial height H, axially from a first tread edge to a second tread edge 5, and circumferentially around the entire periphery of the tire (not shown). In the example shown, the tread 2 comprises five circumferential ribs, including two axially external circumferential ribs referred to as shoulder ribs 6, each extending axially from a tread edge 5 to a circumferential groove 7 over an axial width L.sub.S. Shown in section in each shoulder rib 6 is a cavity 8 of cylindrical shape that opens onto the tread surface 3 over a circular opening surface 81 of diameter D. Also shown are the crown reinforcement of the tire, made up of crown layers radially inside the bottom surface 4, and the carcass reinforcement radially inside the crown reinforcement.

[0059] FIG. 2 presents a perspective view of a shoulder rib 6 according to the invention. More specifically, it presents a shoulder portion of the tread 2, comprising a shoulder rib 6, a circumferential groove 7 and an intermediate circumferential rib. The shoulder rib 6 extends axially from a tread edge 5 to the circumferential groove 7 over an axial width L.sub.S. The shoulder rib 6 comprises cavities 8 that open onto the tread surface 3, forming an opening surface 81 inscribed in a circle of diameter D. The cavities 8 are distributed circumferentially at a circumferential spacing P and positioned circumferentially along a periodic curve 9 having a period T and an amplitude A.

[0060] FIG. 3 shows a contact patch 31 of a tread of an aeroplane tire according to the invention when the tire in the new state, inflated to its recommended nominal pressure pursuant to the TRA standard, is squashed under a load corresponding to a radial deflection of 32%. The contact patch, inscribed in a rectangle, is defined by its circumferential length L.sub.C and its axial width L.sub.A. In the example shown, the shoulder rib 6, extending axially between the edge 5 of the tread and the circumferential groove 7 over an axial width L.sub.S, comprises a distribution of cavities 8 that open onto the tread surface 3 over opening surfaces 81 of circular section of diameter D that are distributed at a spacing P approximately equal to 0.1 times the period T of the periodic curve. The curve 9, which bears the cavities 8, has a period T less than the circumferential length L.sub.S and an amplitude A approximately equal to 0.5 times the axial width L.sub.S of the shoulder rib 6.

[0061] FIG. 4 shows a contact patch 31 of a tread of an aeroplane tire according to a preferred embodiment when the tire in the new state, inflated to its recommended nominal pressure pursuant to the TRA standard, is squashed under a load corresponding to a radial deflection of 32%. The contact patch, inscribed in a rectangle, is defined by its circumferential length L.sub.C and its axial width L.sub.A. In the example shown, each shoulder rib 6, extending axially between the edge 5 of the tread and the circumferential groove 7 over an axial width L.sub.S, comprises a distribution of cavities 8 that open onto the tread surface 3 over opening surfaces 81 of circular section of diameter D that are distributed at a spacing P approximately equal to 0.1 times the period T of the periodic curve. The curve 9, which bears the cavities 8, has a period T less than the circumferential length L.sub.S and an amplitude A approximately equal to 0.5 times the axial width L.sub.S of the shoulder rib 6. Moreover, the tread comprises three axially internal circumferential ribs 10 that extend axially from a first circumferential groove 7 to a second circumferential groove 7, two intermediate ribs situated on either side of the equatorial plane XZ of the tire, and a central rib centred on the equatorial plane XZ of the tire. Each of the two shoulder ribs 6 comprises groove-edge cavities 11 that open onto the tread surface 3 and onto the circumferential groove 7 adjacent to the shoulder rib. Each of the three axially internal circumferential ribs 10 comprises groove-edge cavities 11 that open onto the tread surface 3 and onto each of the circumferential grooves 7 adjacent to the axially internal circumferential rib. The groove-edge cavities 11 formed in the two shoulder ribs 6 and in the three axially internal circumferential ribs form mutually parallel rows 12 of cavities that are inclined at an angle I equal to 90° with respect to the circumferential direction XX′ of the tire. In the present case, the rows 12 of cavities are distributed circumferentially around the entire periphery of the tire, at a constant circumferential spacing P1 equal to 0.5 times the circumferential length L.sub.C of the contact patch of the tire.

[0062] The inventors carried out the invention for an aeroplane tire of size 46×17R20, the use of which is characterized by a nominal pressure equal to 15.3 bar, a nominal static load equal to 20 473 daN, and a maximum reference speed of 360 km/h.

[0063] In the tire studied, the tread comprises five circumferential ribs: 2 shoulder ribs, 2 intermediate ribs and a central rib with respective axial widths of 50 mm, 33.5 mm and 82 mm. Each of the two shoulder ribs comprises cylindrical cavities that open onto the tread surface, forming a circular opening surface having a diameter D equal to 5 mm. The cavities are distributed circumferentially at a circumferential spacing P equal to 25 mm and are positioned circumferentially along a periodic curve, of the broken-line type, having a period T equal to 145 mm and an amplitude A equal to 30 mm.

[0064] Compared with a reference tire having the same tread but without cavities in the shoulder ribs, the inventors have demonstrated, in tread separation tests following damage to the shoulder, that the mean length of the pieces of shoulder rib is divided by 3 compared with the reference tire and that the mean mass thereof is divided by 2.