Aircraft tire with specified zigzag working reinforcement

Abstract

The working reinforcement (2) of an aircraft tire is made by the zigzag winding of a strip (5) having width W, with a periodic curve (7), corresponding to the mid-line of the strip, forming, with the circumferential direction (XX), a non-zero angle A. The circumferential distance (c) between the extrema (S.sub.51, S.sub.52, S.sub.53) of the respective mid-lines of two consecutive strip portions (51, 52, 53) is equal to the ratio W/sin A. For any set of three consecutive strip portions (51, 52, 53), made up of a first, a second and a third portion, the respective mid-lines of the first and third strip portions (51, 53) intersect at an intersection point (I), axially aligned with the extremum (S.sub.52) of the mid-line of the second strip portion (52) and axially on the inside of said extremum (S.sub.52) at an axial distance (a) at least equal to the width W.

Claims

1. An aircraft tire comprising: a working reinforcement radially on the inside of a tread and radially on the outside of a carcass reinforcement; the working reinforcement comprising at least one working bi-ply made at least in part of two radially superposed working layers; each working layer being made up of a juxtaposition of portions of a strip of width W; the strip being wound in a zigzag, in the circumferential direction of the tire, onto a cylindrical laying surface of radius R, having as its axis of revolution the axis of rotation of the tire, and with a periodic curve; the periodic curve corresponding to the mid-line of the strip and forming, with the circumferential direction of the tire and in the equatorial plane of the tire, a non-zero angle A; and two consecutive strip portions, each having respective mid-lines comprising extrema, wherein the circumferential distance (c) between the extrema of the respective mid-lines of the two consecutive strip portions is equal to the ratio W/sin A between the width W of the strip and the sine of the angle A, and wherein, for any set of three consecutive strip portions, made up of a first, a second and a third portion having respective mid-lines comprising extrema, the respective mid-lines of the first and third strip portions intersect at an intersection point, axially aligned with the extremum of the mid-line of the second strip portion and axially on the inside of said extremum at an axial distance (a) at least equal to the width W of the strip, and wherein any portion of the periodic curve, extending axially inwards from one extremum of the periodic curve to a point on the equatorial plane of the tire, comprises a first, concave circular portion of radius R.sub.1, extending axially inwards from the extremum to a second, convex circular portion of radius R.sub.2, the second, convex circular portion of radius R.sub.2 extending axially inwards to a third, rectilinear portion forming an angle A with the circumferential direction, the third, rectilinear portion extending axially inwards to the point on the equatorial plane of the tire.

2. The aircraft tire according to claim 1, wherein the intersection point between the respective mid-lines of the first and third strip portions is positioned axially on the inside of the extremum of the mid-line of the second strip portion at an axial distance (a) at most equal to twice the width W of the strip.

3. The aircraft tire according to claim 1, wherein the intersection point between the respective mid-lines of the first and third strip portions is positioned axially on the inside of the extremum of the mid-line of the second strip portion at an axial distance (a) equal to R.sub.1*(1cos B) with B=a sin((W/sin A)/R.sub.1).

4. The aircraft tire according to claim 3, wherein the ratio R.sub.1/W between the radius R.sub.1 of the concave circular portion of the periodic curve and the width W of the strip is at least equal to 10.

5. The aircraft tire according to claim 1, wherein the radius R.sub.2 of the second, convex circular portion of the periodic curve is equal to the radius R.sub.1 of the first, concave circular portion of the periodic curve.

6. A method for manufacturing an aircraft tire according to claim 1, comprising a step of manufacturing the at least one working bi-ply and a step of manufacturing the aircraft tire such that the working reinforcement comprises the manufactured at least one working bi-ply.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The features and other advantages of the invention will be better understood with the aid of the following FIGS. 1 to 5, which have not been drawn to scale:

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

(3) FIG. 2: a perspective view of a strip that makes up a working bi-ply of a prior art tire, wound circumferentially in a zigzag, with a periodic curve, onto a cylindrical laying surface.

(4) FIG. 3: a developed view of a strip that makes up a working bi-ply of a prior art tire, wound circumferentially in a zigzag, with a periodic curve, after the laying of one period.

(5) FIG. 4: a developed view of a strip that makes up a working bi-ply of a tire according to the invention, wound circumferentially in a zigzag, with a periodic curve, after the laying of one period.

(6) FIG. 5: a detail view of an axial end section of a tire according to an embodiment of the invention, having a set of three consecutive strip portions.

DETAILED DESCRIPTION OF THE DRAWINGS

(7) FIG. 1 shows a half-view in section, in a radial plane (YZ), of a prior art 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. In the example shown, the working reinforcement 2 comprises a working bi-ply 21 made up of two radially superposed working layers (211, 212) and obtained by circumferential zigzag winding (see FIG. 2) of a strip of width W onto a cylindrical laying surface 6 of radius R, having as its axis of revolution the axis of rotation (YY) of the tire. The axial end overthicknesses of the working bi-ply 21 are not shown for the sake of simplicity. In a radial plane, each working layer (211, 212) is made up of an axial juxtaposition of strip portions 5 of width W/cos A, where W is the width of the strip 5, measured perpendicularly to its mid-line, and A is the angle (see FIG. 3) formed by the mid-line of the strip 5 with the circumferential direction (XX) in the equatorial plane (XZ). Since the width of the working bi-ply is equal to L, its half-width L/2 is shown in FIG. 1.

(8) FIG. 2 is a perspective view of a strip 5 that makes up a working bi-ply of a prior art tire, wound circumferentially in a zigzag, with a periodic curve 7, onto a cylindrical laying surface 6, which is rotationally symmetrical about an axis of rotation (YY) of the tire, having a radius R. Only three winding turns of the strip 5 are shown in FIG. 2, that is to say one working layer in the course of being produced.

(9) FIG. 3 is a developed view of a strip 5 wound circumferentially in a zigzag, with a periodic curve 7, after the laying of one period, in the case of a prior art tire. The strip 5 is laid on a cylindrical surface 6 of circumference 2R, shown in a developed form in FIG. 3. The mid-line of the strip 5 follows a periodic curve 7, forming an angle A with the circumferential direction XX. The strip 5 has a width W measured perpendicularly to the mid-line of the strip that is borne by the periodic curve 7. It also comprises extrema S characterized by a radius of curvature R.sub.1. At S, the curvature is referred to as concave, since the centre of curvature O.sub.1 is axially on the inside of the extremum S. The periodic curve 7 has a period P equal to the circumference 2R plus or minus W/sin A, where W/sin A is the width of the strip 5 projected in the circumferential direction XX. Moreover, the periodic curve 7 has an amplitude C which, increased by the width W of the strip, defines the width L=C+W of the working bi-ply.

(10) FIG. 4 is a developed view of a strip 5 wound circumferentially in a zigzag, with a periodic curve 7, after the laying of one period, in the case of a tire according to the invention. The strip 5 is laid on a cylindrical surface 6 of circumference 28, shown in a developed form in FIG. 3. The mid-line of the strip 5 follows a periodic curve 7, forming an angle A with the circumferential direction XX. The strip 5 has a width W measured perpendicularly to the mid-line of the strip that is borne by the periodic curve 7. The strip is such that any portion of the periodic curve 7, extending axially inwards from one extremum S of the periodic curve 7 to a point E on the equatorial plane XZ of the tire, comprises a first, concave circular portion 8 of radius R.sub.1, extending axially inwards from the extremum S to a second, convex circular portion 9 of radius R.sub.2, the second, convex circular portion 9 of radius R.sub.2 extending axially inwards to a third, rectilinear portion 10 forming an angle A with the circumferential direction XX, the third, rectilinear portion 10 extending axially inwards to the point E on the equatorial plane XZ of the tire. The first circular portion 8 of radius R.sub.1 is concave since the centre O.sub.1 (see FIG. 5) is axially on the inside of the periodic curve 7. The second circular portion 9 of radius R.sub.2 is convex since the centre O.sub.2 (see FIG. 5) is axially on the outside of the periodic curve 7.

(11) FIG. 5 shows an axial end section of a tire according to the invention. It has more particularly a set of three consecutive strip portions (51, 52, 53) made up of a first, a second and a third portion having respective mid-lines comprising extrema (S.sub.51, S.sub.52, S.sub.53). The respective mid-lines of each of the strip portions comprises a first, concave circular portion 8 of radius R.sub.1 and centre O.sub.1, a second, convex circular portion 9 of radius R.sub.2 and centre O.sub.2, and a third, rectilinear portion 10 forming an angle A with the circumferential direction XX. The circumferential distance c between the extrema (S.sub.51, S.sub.52, S.sub.53) of the respective mid-lines of two consecutive strip portions (51, 52, 53) is equal to the ratio W/sin A between the width W of the strip 5 and the sine of the angle A. The respective mid-lines of the first and third strip portions (51, 53) intersect at an intersection point (I), axially aligned with the extremum S.sub.52 of the mid-line of the second strip portion 52 and axially on the inside of said extremum S.sub.52 at an axial distance a at least equal to the width W of the strip 5. In the preferred embodiment shown in FIG. 5, the periodic curve 7 comprising, at its extrema (S.sub.51, S.sub.52, S.sub.53), a circular portion 8 of radius R.sub.1, the intersection point I between the respective mid-lines of the first and third strip portions (51, 53) is positioned axially on the inside of the extremum S.sub.52 of the mid-line of the second strip portion 52 at an axial distance a equal to R.sub.1*(1cos B) with B=a sin((W/sin A)/R.sub.1). FIG. 5 is not drawn to scale: the three consecutive strip portions are contiguous in the main section and their respective axial ends comprise smaller gaps between one another than those shown in FIG. 5.

(12) The inventors have produced the invention for an aircraft tire of size 1400530 R 23, of which the working reinforcement comprises three superposed bi-plies, respectively radially from the inside to the outside, BF1, BF2 and BF3, the geometrical features and laying characteristics of which are presented in the following Table 1:

(13) TABLE-US-00001 TABLE 1 Working bi-ply BF1 BF2 BF3 Axial width L (mm) 390 mm 370 mm 350 mm Strip width W (mm) 11.3 mm 11.3 mm 11.3 mm Angle A () 9.1 9.05 9.0 Radius R.sub.1 of the first, concave 220 mm 220 mm 220 mm circular portion (mm) Radius R.sub.2 of the second, convex 220 mm 220 mm 220 mm circular portion (mm) Laying circumference 2R (mm) 4076 mm 4096 mm 4115 mm Laying radius R (mm) 649 mm 652 mm 655 mm Laying circumference 2R (mm) 4076 mm 4095 mm 4113 mm Number of periods N 1 1 1 Number of winding turns T 58 58 58

(14) Compared with that of a reference prior art tire, the crown reinforcement for an aircraft tire according to the invention suffers damage later and less seriously when the tire runs under harsh test conditions, such as those of the TSO (Technical Standard Order) test imposed by an FAA (Federal Aviation Administration) Standard.

(15) The objective of the TSO test is to realize damage-free use cycle phases for the tire, tread separation of the tire, that is to say the loss of the tread, being allowed, however, during the final cycle, but not a loss of pressure.

(16) The TSO test is a test, carried out on a rolling road, which is broken down into four phases:

(17) 50 aircraft takeoff cycles, in which the tire is subjected to the nominal pressure P.sub.v and to a load that varies between the nominal load Z.sub.n, and 0.

(18) 8 aircraft taxiing cycles, in which the tire is subjected to the nominal pressure P.sub.v, to the nominal load Z.sub.n and to a speed of around 65 km/h for about 10 700 m.

(19) 2 aircraft taxiing cycles, in which the tire is subjected to the nominal pressure P.sub.v, to 1.2 times the nominal load Z.sub.n and to a speed of around 65 km/h for about 10 700 m.

(20) 1 overloaded aircraft takeoff cycle, in which the tire is subjected to the nominal pressure P.sub.v and to a load that varies between 1.5 times the nominal load Z.sub.n and 0.

(21) This invention is applicable not only to any working bi-ply of the crown reinforcement of an aircraft tire, but also, more generally, to any bi-ply of the crown reinforcement, such as, for example, a protective bi-ply of the protective reinforcement.

(22) It is also applicable to any tire comprising a crown reinforcement with at least one bi-ply obtained by zigzag winding of a strip, such as, for example and non-exhaustively, a tire for a metro train.