Crown reinforcement for an aircraft tire

Abstract

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.sub.1, L.sub.2), from first axial end (I.sub.1, I.sub.2) to second axial end (I.sub.1, I.sub.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.sub.1, L.sub.2) of the radially superposed working bi-plies (21, 22) is at least equal to 2(W+(RW/2)(1cos A)).

Claims

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+(RW/2)(1cos 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.sub.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+(RW/2)(1cos 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.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The features and other advantages of the invention will be better understood with the aid of FIGS. 1 to 4, which have not been drawn to scale:

(2) FIG. 1: a half-view in section of a tire according to the invention, in a meridian or radial plane (YZ) passing through the axis of rotation (YY) of the tire.

(3) FIG. 2: a general arrangement of a strip that makes up a working layer of a tire according to the invention.

(4) FIGS. 3A and 3B: views in section, on a meridian plane (YZ), of the axial end zones of two consecutive working bi-plies of a reference tire (FIG. 3A) and of a tire according to the invention (FIG. 3B), respectively.

(5) FIG. 4: a perspective view of a strip circumferentially wound in a zigzag, with a periodic curve on the surface of a building drum.

DETAILED DESCRIPTION OF THE DRAWINGS

(6) FIG. 1 depicts a half-view in section, in a radial or meridian plane (YZ) passing through the axis of rotation (YY) of the tire 1, of an aircraft tire 1 comprising a working reinforcement 2 radially on the inside of a tread 3 and radially on the outside of a carcass reinforcement 4. The working reinforcement 2 comprises two working bi-plies (21, 22) that are radially superposed and respectively have an axial width (L.sub.1, L.sub.2) from a first axial end (I.sub.1, I.sub.2) to a second axial end (I.sub.1, I.sub.2) (not depicted). Each working bi-ply (21, 22) comprises, at least in part, two working layers (211, 212; 221, 222) which are radially superposed and respectively made up of an axial juxtaposition of strips 5 of width W.

(7) FIG. 2 depicts a general arrangement of a strip 5 that makes up a working bi-ply of axial width L. In FIG. 2, a zigzag winding over two turns is depicted. The strip 5 of width W has a mid-line, running circumferentially, namely in the direction (XX) along a periodic curve 6 comprising extrema 7. In other words, the periodic curve 6 is the curve supporting the mid-line of the strip 5. The periodic curve 6 forms, in the equatorial plane (XZ) and with the circumferential direction (XX), a non-zero angle A. The periodic curve 6 has a mean radius of curvature R at its extrema 7. With each turn of zigzag winding the strip 5 is offset axially so as to obtain an axial juxtaposition of strip portions of width W.

(8) FIG. 3A is a view in section, in a radial plane (YZ), from an axial end zone of two working bi-plies (21, 22) of a working reinforcement 2 of a reference tire. Each working bi-ply (21, 22), respectively of axial width L.sub.1 and L.sub.2, is made up of 2 radially superposed working layers (211, 212; 221, 222) in the main section and 4 partially superposed working layers at the axial end additional thickness. Each working layer (211, 212; 221, 222) is made up of an axial juxtaposition of portions of strip 5 of width W. Each portion of strip 5 comprises textile reinforcers 8 coated in an elastomeric compound 9. In the case of the reference tire, the respective axial end additional thicknesses of the two working bi-plies (21, 22) are at least partially radially superposed.

(9) FIG. 3B is a view in section, in a radial plane (YZ), of an axial end zone of two working bi-plies (21, 22) of a working reinforcement 2 of a tire according to the invention. In this case, the respective axial end additional thicknesses of the two working bi-plies (21, 22) are axially offset by an axial distance DL/2 at each of the two axial end zones.

(10) FIG. 4 is a perspective view of a strip 5 wound circumferentially in a zigzag, with a periodic curve 7, on the lateral surface 10 of a tire building drum 11 of radius R.sub.f and having as its axis the axis of rotation (YY) of the tire.

(11) The inventors carried out the invention for an aircraft tire of size 1400530 R 23.

(12) In the tire investigated, the working reinforcement comprises two radially superposed working bi-plies, the radially innermost working bi-ply having an axial width L.sub.1 equal to 379 mm and the radially outermost working bi-ply having an axial width L.sub.2 equal to 349 mm. The difference DL between the respective axial widths (L.sub.1, L.sub.2) of the two radially superposed working bi-plies is, in this instance, equal to 30 mm. Since the strip that makes up a working bi-ply of width W equal to 11 mm wound in a zigzag in a periodic curve forming, in the equatorial plane of the tire and with the circumferential direction of the tire, an angle A of the order of 10 and having a radius of curvature R of the order of 200 mm at its extrema, the difference DL, equal to 30 mm, is therefore greater than 2(W+(RW/2)(1cos A) which equals 28 mm. Furthermore, the ratio R/W is equal to 18, and therefore higher than 13. Furthermore, the textile reinforcers of the strip are hybrid reinforcers made up of a combination of an aliphatic polyamide and of an aromatic polyamide. The gain in endurance of a tire comprising two working bi-plies according to the invention, by comparison with the reference tire, is estimated to be equal to at least 10%. This endurance is measured in terms of the amount of damage found on a tire subjected to a regulation TSO test as defined by the European Aviation European Safety Agency (EASA).

(13) The scope of protection of the invention is not limited to the examples given hereinabove. The invention is embodied in each novel characteristic and each combination of characteristics, which includes every combination of any features which are stated in the claims, even if this feature or combination of features is not explicitly stated in the examples.