Crown reinforcement for an aircraft tire
Crown reinforcement of an aircraft tire comprises a working reinforcement ( 2 ) radially inside of tread ( 3 ) and radially outside of carcass reinforcement ( 4 ). Working reinforcement ( 2 ) comprises two working bi-plies ( 21, 22 ) radially superposed with respective axial widths (L 1 , L 2 ), from first axial end (I 1 , I 2 ) to second axial end (I′ 1 , I′ 2 ). Each working bi-ply ( 21, 22 ) comprises two working layers ( 211, 212; 221, 222 ) radially superposed and respectively made up of axially juxtaposed portions of strip ( 5 ) of axial width W extending circumferentially in periodic curve ( 6 ) that forms, in the equatorial plane (XZ) of the tire and with the circumferential direction (XX′) of the tire, a non-zero angle A and has a radius of curvature R at its extrema ( 7 ). The difference DL between the respective axial widths (L 1 , L 2 ) of the radially superposed working bi-plies ( 21, 22 ) is at least equal to 2×(W+(R−W/2)−(1−cos A)).
1. An aircraft tire comprising:
a working reinforcement radially on an inside of a tread and radially on an outside of a carcass reinforcement;
the working reinforcement comprising at least two working bi-plies which are radially superposed and respectively have an axial width, from a first axial end to a second axial end;
each said working bi-ply having a main section comprising at least in part two working layers that are radially superposed, a first, radially outer, one of the at least two working bi-plies comprising, at an axial end thereof, a first axial-end additional thickness, extending axially to an outside of the main section of the first bi-ply, the first axial-end additional thickness comprising a first set of two additional working layers sandwiched between the two working layers of the first bi-ply such that the first axial-end additional thickness is four superposed working layers, each working layer being respectively made up of an axial juxtaposition of portions of a strip, and a second, radially inner, one of the two working bi-plies comprising, at an axial end thereof, a second axial-end additional thickness, extending axially to an outside of the main section of the second bi-ply, the second axial-end additional thickness comprising a second set of two additional working layers sandwiched between the two working layers of the second bi-ply,
wherein the working reinforcement comprises six working layers only in a region of axial overlap between the first axial-end additional thickness and the main section of the second, radially inner, bi-ply;
the strip, of axial width W, extending circumferentially in a periodic curve that forms, in the equatorial plane of the tire and with the circumferential direction of the tire, a non-zero angle A and has a radius of curvature R at its extrema;
the strip being made up of reinforcers coated in an elastomeric compound;
wherein a difference DL between the respective axial widths of the at least two radially superposed working bi-plies is at least equal to 2×(W+(R−W/2)×(1−cos A)),
wherein the first, radially outer, one of the at least two working bi-plies contacts the second, radially inner, one of the at least two working bi-plies, over their respective axial widths axially inwardly of the first axial-end additional thickness, and the first and second axial-end additional thicknesses are axially offset by a distance of DL/2.
2. The aircraft tire according to claim 1 , wherein the axial width W of the strip is at least equal to 2 mm.
3. The aircraft tire according to claim 1 , wherein the axial width W of the strip is at most equal to 20 mm.
4. The aircraft tire according to claim 1 , wherein a ratio R/W between the radius of curvature R, at the extrema of the periodic curve of the strip, and the width W of the strip is at least equal to 13.
5. The aircraft tire according to claim 1 , wherein the non-zero angle A formed by the periodic curve of the strip in the equatorial plane and with the circumferential direction is at least equal to 3°.
6. The aircraft tire according to claim 1 , wherein the non-zero angle A, formed by the periodic curve of the strip in the equatorial plane and with the circumferential direction is at most equal to 35°.
7. The aircraft tire according to claim 1 , wherein the reinforcers of the strip are made of a textile material.
8. The aircraft tire according to claim 1 , wherein the reinforcers of the strip are made of an aliphatic polyamide.
9. The aircraft tire according to claim 1 , wherein the reinforcers of the strip are made of an aromatic polyamide.
10. The aircraft tire according to claim 1 , wherein the reinforcers of the strip are made of a combination of an aliphatic polyamide and of an aromatic polyamide.
11. Method of manufacturing an aircraft tire according to claim 1 , comprising a step of manufacturing the working reinforcement, wherein the at least two working bi-plies that are radially superposed and respectively have an axial width, from a first axial end to a second axial end, are obtained by circumferential zigzag winding of the strip, of axial width W, on the lateral surface of a tire building drum of radius R f and having as its axis the axis of rotation of the tire, with the periodic curve forming, in the equatorial plane and with the circumferential direction, the non-zero angle A and having the radius of curvature R at its said extrema such that the difference DL between the respective axial widths of the at least two radially superposed working bi-plies is at least equal, in terms of absolute value, to 2×(W+(R−W/2)×(1−cos A)).
12. The aircraft tire according to claim 1 , wherein the axial width W of the strip is at least equal to 6 mm.
13. The aircraft tire according to claim 1 , wherein the axial width W of the strip is at most equal to 14 mm.
14. The aircraft tire according to claim 1 , wherein the non-zero angle A formed by the periodic curve of the strip in the equatorial plane and with the circumferential direction is at least equal to 5°.
15. The aircraft tire according to claim 1 , wherein the non-zero angle A, formed by the periodic curve of the strip in the equatorial plane and with the circumferential direction is at most equal to 25°.