Crown Reinforcement For An Airplane Tire

Abstract

Working reinforcement (2) of airplane tire (1) is radially inside tread (3) and radially outside carcass reinforcement (4), comprising carcass layer (41). Working reinforcement (2) comprises working biply (21) of greatest axial width (L.sub.T) and two axial ends (E). Hoop reinforcement (7) comprises hooping layer (71) radially inside working biply (21), and having axial width (L.sub.F) at least equal to 0.8 times L.sub.T. Distance D between axial end (E) of greatest axial width (L.sub.T) and its orthogonal projection (I) onto the radially outermost carcass layer (41) is at least equal to 7 mm and the distance D between point (F) of working biply (21) of greatest axial width (L.sub.T), axially inside axial end (E) at a distance L equal to 25 mm, and its orthogonal projection (J) onto the radially outermost carcass layer (41) is at least equal to 4 mm and at most equal to the distance D.

Claims

1. An airplane 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 biply consisting at least in part of two radially superposed working layers; each working layer comprising reinforcers coated in an elastomeric material, positioned circumferentially along a periodic curve and forming, with the circumferential direction of the tire and in the equatorial plane of the tire (XZ), an angle at least equal to 8 and at most equal to 30; the working biply of greatest axial width (L.sub.T) comprising two axial ends (E) each one corresponding to the axially outermost and radially innermost point of the working biply; the carcass reinforcement comprising at least one carcass layer comprising reinforcers which are coated in an elastomeric material, forming, with the circumferential direction of the tire, an angle at least equal to 80 and at most equal to 100; a hoop reinforcement comprising at least one hooping layer comprising reinforcers which are coated in an elastomeric material, forming, with the circumferential direction of the tire, an angle at most equal to 5; at least one hooping layer being radially on the inside of the working biply of greatest axial width (L.sub.T), and having an axial width (L.sub.F) at least equal to 0.8 times the axial width (L.sub.T) of the working biply of greatest axial width (L.sub.T); wherein the distance D between an axial end of the working biply of greatest axial width (L.sub.T) and its orthogonal projection (I) onto the radially outermost carcass layer is at least equal to 7 mm and wherein the distance D between the point of the working biply of greatest axial width (L.sub.T), axially on the inside of the axial end at a distance L equal to 25 mm, and its orthogonal projection (J) onto the radially outermost carcass layer is at least equal to 4 mm and at most equal to the distance D.

2. The airplane tire according to claim 1, wherein the distance D between an axial end of the working biply of greatest axial width (L.sub.T) and its orthogonal projection onto the radially outermost carcass layer is at most equal to 16 mm.

3. The airplane tire according to claim 1, wherein the reinforcers of the working layers of any working biply are made of a textile material.

4. The airplane tire according to claim 1, wherein the reinforcers of the working layers of at least the working biply of greatest axial width (L.sub.T) are hybrid reinforcers made up of a combination of an aliphatic polyamide and an aromatic polyamide.

5. The airplane tire according to claim 1, wherein the reinforcers of the hooping layers are reinforcers containing an aromatic polyamide.

6. The airplane tire according to claim 1, wherein the tire comprises a protective reinforcement comprising at least one protective layer.

7. The airplane tire according to claim 6, wherein at least one protective layer comprises metal reinforcers coated in an elastomeric material.

Description

[0048] The features and other advantages of the invention will be better understood with the aid of the following FIGS. 1 to 5 which are not drawn to scale:

[0049] FIG. 1: A half-view in cross section of the crown of an airplane tire of the prior art, the section being in a radial plane (YZ) passing through the axis of rotation (YY) of the tire.

[0050] FIG. 2: A half-view in cross section of the crown of an airplane tire according to the invention, the section being in a radial plane (YZ) passing through the axis of rotation (YY) of the tire.

[0051] FIG. 3: A detailed view in cross section of the axial end of the working reinforcement of an airplane tire according to the invention, the section being in a radial plane (YZ) passing through the axis of rotation (YY) of the tire.

[0052] FIG. 4: A perspective view of a strip that makes up a working biply of an airplane tire, circumferentially wound in a zigzag along a periodic curve on a cylindrical laying surface.

[0053] FIG. 5: A developed view of a strip that makes up a working biply of an airplane tire, wound circumferentially in a zigzag along a periodic curve after one period has been laid.

[0054] FIG. 1 depicts, in a radial plane YZ passing through the axis of rotation YY of the tire, a half-view in cross section of the crown of an airplane tire 1 of the prior art, 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 given, the working reinforcement 2 comprises five working biplies 21, the radially innermost working biply having the greatest axial width L.sub.T, measured between its two axial ends. FIG. 1 shows only a half-width L.sub.T/2 between an axial end E of the radially innermost working biply 21 and the equatorial plane XZ. Each working biply 21 is made up at least in part of two radially superposed working layers (211, 212) (see FIG. 3). Each working layer (211, 212) comprises textile reinforcers of the aliphatic polyamide type, coated in an elastomeric material. The carcass reinforcement 4 comprises a radial superposition of carcass layers 41. Each carcass layer 41 comprises textile reinforcers of the aliphatic polyamide type, coated in an elastomeric material and forming, with the circumferential direction XX of the tire, an angle at least equal to 80 and at most equal to 100. Furthermore, radially on the inside of the tread 3, the tire 1 comprises a protective reinforcement 8 made up of a protective layer.

[0055] FIG. 2 shows, in a radial plane YZ passing through the axis of rotation YY of the tire, a half-view in cross section of the crown of an airplane tire 1 according to the invention, 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 given, the working reinforcement 2 comprises one single working biply 21, the working biply having, of all the crown layers, the greatest axial width L.sub.T, measured between its two axial ends E. FIG. 2 shows only a half-width L.sub.T/2 between an axial end E of the working biply 21 and the equatorial plane XZ. The working biply 21 is made up at least in part of two radially superposed working layers (211, 212) (see FIG. 3). Each working layer (211, 212) comprises reinforcers 5, generally hybrid reinforcers, made up of a combination of an aliphatic polyamide and of an aromatic polyamide, coated in an elastomeric material, positioned circumferentially along a periodic curve and forming, with the circumferential direction XX of the tire and in the equatorial plane XZ of the tire, an angle at least equal to 8 and at most equal to 30. Furthermore, radially on the inside of the working biply 21 of greatest axial width L.sub.T, the tire 1 comprises a hoop reinforcement 7, comprising 6 hooping layers 71. Each hooping layer 71 comprises reinforcers, generally made of aromatic polyamide, coated in an elastomeric material and forming, with the circumferential direction XX of the tire, an angle at most equal to 5. The axially widest hooping layer 71 is radially on the inside of and adjacent to the working biply 21, and has an axial width L.sub.F at least equal to 0.8 times the axial width L.sub.T of the said working biply 21. FIG. 2 depicts only an axial half-width L.sub.F/2 of the axially widest hooping layer. The carcass reinforcement 4 comprises a radial superposition of carcass layers 41. Each carcass layer 41 comprises reinforcers, generally hybrid reinforcers, made up of a combination of an aliphatic polyamide and of an aromatic polyamide and forming, with the circumferential direction XX of the tire, an angle at least equal to 80 and at most equal to 100. According to the invention, the geometric profile of the working biply 21 of greatest axial width L.sub.T, at its axial end, is not pressed as firmly against the carcass reinforcement as is the case in the tire of the prior art depicted in FIG. 1.

[0056] FIG. 3 is a detailed view in cross section of the axial end of the working reinforcement 2 of an airplane tire 1 according to the invention, in a radial plane YZ passing through the axis of rotation YY of the tire. In the example given, the working reinforcement 2 comprises a working biply 21, the respective axial ends of which have overthicknesses. The working biply 21 is made up of two radially superposed working layers (211, 212) in the main section and of three working layers in the axial end zone. Each working layer (211, 212) is made up of the axial juxtaposition of strips 9, each strip itself being an axial juxtaposition of textile reinforcers 5 coated in an elastomeric compound. In this instance, the textile reinforcers 5 are hybrid reinforcers made up of a combination of an aliphatic polyamide and of an aromatic polyamide. The axially widest hooping layer 71 is radially on the inside of and adjacent to the working biply 21 of greatest axial width L.sub.T, and has an axial width L.sub.F at least equal to 0.8 times the axial width L.sub.T of the working biply 21 of greatest axial width L.sub.T. The carcass reinforcement 4 comprises a radial superposition of carcass layers 41, each carcass layer 41 comprising hybrid reinforcers made up of a combination of an aliphatic polyamide and of an aromatic polyamide and forming, with the circumferential direction XX of the tire, an angle at least equal to 80 and at most equal to 100. According to the invention, the distance D between the axial end E of the working biply 21 of greatest axial width L.sub.T and its orthogonal projection I onto the radially outermost carcass layer 41 is at least equal to 7 mm and the distance D between the point F of the working biply 21 of greatest axial width L.sub.T, axially on the inside of the axial end E at a distance L equal to 25 mm, and its orthogonal projection J onto the radially outermost carcass layer 41 is at least equal to 4 mm and at most equal to the distance D.

[0057] FIG. 4 is a perspective view of a strip 9 that makes up a working biply of an airplane tire, circumferentially wound in a zigzag, along a periodic curve 6, onto a cylindrical laying surface 10 exhibiting symmetry of revolution about the axis of rotation (YY) of the tire, having a radius R.

[0058] FIG. 5 is a developed view of a strip 9 that makes up a working biply of a tire according to the invention, circumferentially wound in a zigzag, along a periodic curve 6, after one period has been laid. The strip 9 is laid on a cylindrical surface 10 of circumference 2R, depicted in developed form. The midline of the strip 9 follows a periodic curve 6, forming an angle B with the circumferential direction XX. The periodic curve 6 has a period P equal to 2R and an amplitude C which, increased by the width W of the strip 9, defines the width L.sub.T=C+W of the working biply.

[0059] The inventors carried out the invention for an airplane tire of size 46X17 R 20 comprising, radially from the outside inwards, a protective reinforcement made up of a protective layer the reinforcers of which are made of metal, a working reinforcement made up of a working biply the reinforcers of which are hybrid, and a hoop reinforcement made up of six radially superposed hooping layers the reinforcements of which are made of aramid. The inventors compared a reference tire and a tire according to the invention, differing only in terms of the geometric profile of the working biply of greatest axial width, at its axial end, the said profile being said to have been measured for the tire according to the invention.

[0060] The geometric characteristics of the tires under investigation are given in Table 1 below:

TABLE-US-00001 TABLE 1 Reference Invention Difference Distance D (mm) 3 mm 7 mm 4 mm Distance D (mm) 2.5 mm 4.5 mm 2 mm Distance L (mm) 25 mm 25 mm

[0061] The distances D, D and L are measured on a radial cross section of the tire.

[0062] The distance D is measured, at right angles to the radially outermost carcass layer, between the radially innermost point of the penultimate reinforcer of the working biply of greatest axial width and the radially outermost point of the first reinforcer encountered in the radially outermost carcass layer.

[0063] The distance D is measured, perpendicular to the radially outermost carcass layer, between the radially innermost point of the reinforcer of the working biply of greatest axial width, axially on the inside of the axially outermost reinforcer of the working biply of greatest axial width at a distance of 25 mm, and the radially outermost point of the first reinforcer encountered in the radially outermost carcass layer.

[0064] The distance L is measured as being the radius equal to 25 mm of the circle centred on the axially outermost reinforcer of the working biply of greatest axial width.

[0065] The respective performance of the tires of the prior art, considered by way of reference, and according to the invention were measured against three criteria: the temperature in the vicinity of the axial end of the working biply of greatest axial width, the maximal tensile load in the reinforcers at the axial end of the working biply of greatest axial width over one wheel revolution, and the maximum number of cycles achieved without damage during a TSO test. The first two criteria came from a finite element numerical simulation on the assumption of steady-state running of the tire at a speed of 10 km/h. The number of cycles without damage was determined by TSO tests.

[0066] The performance criteria for the tires studied are given in Table 2 below:

TABLE-US-00002 TABLE 2 Reference Invention Difference Temperature at the axial end 85 C. 78 C. 7 C. under steady-state running at 10 km/h ( C.) Maximum tensile load at the axial 16 daN 12 daN 4 daN end, over one wheel revolution, in steady-state running at 10 km/h (daN) Number of cycles in TSO test Base 100 161 61

[0067] This invention is applicable not only to an airplane tire but also to any tire comprising a crown reinforcement with at least one biply obtained by a zigzag winding of a strip such as, for example and nonexhaustively, a tire for a metro train.