CROWN REINFORCEMENT FOR AN AIRCRAFT

Abstract

Tire for an aeroplane and, in particular, the crown thereof which comprises a tread (1), a working reinforcement (2), a carcass reinforcement (3) and a hoop reinforcement (4). The radially internal working layer (21) of the working reinforcement (2) comprises a concave portion. The hoop reinforcement (41) comprises at least one hooping layer (41) radially on the inside of the working layer (21) and made up of mutually parallel reinforcing elements, having a mean diameter D, that are inclined, with respect to the circumferential direction (XX), at an angle of between +10 and 10. The hooping layer (41) comprises at least one axial discontinuity (411) having an axial width (L411) at least equal to three times the mean diameter D of the reinforcing elements of the hooping layer (41).

Claims

1. A tire for an aeroplane, comprising: a tread; a working reinforcement radially on the inside of the tread and comprising at least one working layer; the radially internal working layer having an axial width at least equal to two-thirds of the maximum axial width of the tire and comprising a concave portion; a carcass reinforcement radially on the inside of the working reinforcement and comprising at least one carcass layer; a hoop reinforcement radially on the outside of the carcass reinforcement and comprising at least one hooping layer; the hooping layer having an axial width at most equal to 0.8 times the width of the widest working layer and comprising mutually parallel reinforcing elements that are inclined, with respect to the circumferential direction, at an angle of between +10 and 10; and the reinforcing elements of the hooping layer having a mean diameter D, wherein the hooping layer comprises at least one axial discontinuity having an axial width at least equal to three times the mean diameter D of the reinforcing elements.

2. The aeroplane tire according to claim 1, wherein the axial width of the axial discontinuity is at least equal to 10 times the mean diameter D of the reinforcing elements of the hooping layer.

3. The aeroplane tire according to claim 1, wherein the hooping layer comprises at least two axial discontinuities having axial widths at least equal to three times the mean diameter D of the reinforcing elements of the hooping layer.

4. The aeroplane tire according to claim 1, wherein one said axial discontinuity is centered on the equatorial plane of the tire.

5. The aeroplane tire according to claim 3, wherein two said axial discontinuities are positioned symmetrically with respect to the equatorial plane.

6. The aeroplane tire according to claim 1, wherein the hoop reinforcement comprises two said hooping layers.

7. The aeroplane tire according to claim 1, wherein the reinforcing elements of a said hooping layer consist of aliphatic polyamides, aromatic polyamides or a combination of aliphatic polyamides and aromatic polyamides.

8. The aeroplane tire according to claim 1, wherein a said working layer comprises mutually parallel reinforcing elements that are inclined, with respect to the circumferential direction, at an angle of between +20 and 20.

9. The aeroplane tire according to claim 1, wherein wherein the reinforcing elements of a said working layer consist of aliphatic polyamides, aromatic polyamides or a combination of aliphatic polyamides and aromatic polyamides.

10. The aeroplane tire according to claim 1, comprising at least one said carcass layer comprising mutually parallel reinforcing elements that form an angle of between 80 and 100 with the circumferential direction, wherein the reinforcing elements of a carcass layer consist of aliphatic polyamides, aromatic polyamides or a combination of aliphatic polyamides and aromatic polyamides.

11. The aeroplane tire according to claim 1, wherein a protective reinforcement comprising at least one protective layer made up of metal or textile reinforcing elements is disposed radially on the outside of the working reinforcement.

Description

[0050] The features and other advantages of the invention will be understood better with the aid of FIGS. 1 and 2, said figures not being shown to scale but in a simplified manner so as to make it easier to understand the invention.

[0051] FIG. 1: hooping layer having 1 axial discontinuity in the hoop reinforcement centered on the equatorial plane

[0052] FIG. 2: hooping layer having 2 symmetrical axial discontinuities in the hoop reinforcement with respect to the equatorial plane

[0053] FIG. 2B: detail of an axial discontinuity in the hoop reinforcement

[0054] FIG. 1 shows a meridian section, i.e. a section in a meridian plane, of the crown of a tire according to a first embodiment of the invention comprising a tread 1, a working reinforcement 2 radially on the inside of the tread 1, a radial carcass reinforcement 3 radially on the inside of the working reinforcement 2 and a hoop reinforcement 4 positioned radially between the working reinforcement 2 and the radial carcass reinforcement 3, said hoop reinforcement 4 comprising a hooping layer 41 comprising an axial discontinuity in the equatorial plane XZ.

[0055] The respective radial, axial and circumferential directions are the directions ZZ, YY and XX. The equatorial plane XZ is defined by the radial direction ZZ and the circumferential direction XX.

[0056] The working reinforcement 2 is made up of several working layers. The axial width L2 of the radially internal working layer 21, which is the axial distance between its axial ends E2 and E2, is at least equal to two-thirds of the maximum axial width L1 of the tire. The maximum axial width L1 of the tire is measured at the sidewalls, with the tire mounted on its rim and lightly inflated, i.e. inflated to a pressure equal to 10% of its recommended nominal pressure.

[0057] The radially internal working layer 21 comprises a concave portion, the axial limits M2 and M2 of which, on either side of the equatorial plane XZ, are the radially external points of said working layer, positioned at the radial distance R2. The radially internal working layer 21 further comprises two convex portions axially on the outside of said concave portion. These convex portions are respectively bounded axially on the inside by the axial limits M2 and M2 of the concave portion and axially on the outside by the ends E2 and E2 of the working layer.

[0058] The concave portion of the radially internal working layer 21 comprises a part that is concave in the mathematical sense, axially delimited by the points of inflection I2 and I2, and, on either side of said concave part, a part that is convex in the mathematical sense, axially bounded on the outside by an axial limit M2 or M2 of said concave portion. The amplitude of concavity a2 is the difference between the radial distance R2 of the axial limits M2 and M2 and the radial distance r2 of the point C2 situated in the equatorial plane XZ.

[0059] The carcass reinforcement 3 is made up of several carcass layers. In the crown region, radially on the inside of the working reinforcement 2, the radially external carcass layer 31 comprises a portion of which the axial limits M3 and M3, on either side of the equatorial plane, are radially in line with the radially external points of the radially innermost (M2, M2) working layer, in which portion the carcass layer is on either side of the equatorial plane radially on the inside of its respective ends (M3, M3) positioned at the radial distance R3, give or take manufacturing spread.

[0060] Moreover, FIG. 1 shows a hoop reinforcement 4 comprising a hooping layer 41 that is positioned radially between the radially internal working layer 21 and the radially external carcass layer 31 and having an axial discontinuity 411 centered on the equatorial plane XZ.

[0061] FIG. 2 shows a meridian section through the crown of a tire according to a second embodiment of the invention, wherein the hoop reinforcement comprises a hooping layer 41 comprising 2 axial discontinuities which are symmetrical with respect to the equatorial plane XZ and have the same axial width. The other elements of the architecture of FIG. 2 are identical to those in FIG. 1.

[0062] FIG. 2B shows the hooping layer 41 made up of reinforcing elements having a mean diameter D, said figure showing a discontinuity 411 of width L411, said width, according to the invention, being greater than 3 times the mean diameter D.

[0063] The inventors have carried out the invention according to the two embodiments, with a hoop reinforcement comprising two axial discontinuities that are symmetrical with respect to the equatorial plane, for an aeroplane tire of size 4617R20, the use of which is characterized by a nominal pressure of 15.9 bar, a nominal static load of 20473 daN and a maximum reference speed of 225 km/h.

[0064] In the tires studied, the working reinforcement is made up of 6 working layers, the reinforcing elements of which are of the hybrid type. The radially internal working layer has an axial width of 300 mm, i.e. 0.75 times the maximum axial width of the tire. The width of concavity of said radially internal working layer is 160 mm and the amplitude of concavity is 6 mm. The carcass reinforcement is made up of 3 carcass layers, the reinforcing elements of which are hybrid.

[0065] The hoop reinforcement is made up of a hooping layer, the reinforcing elements of which are of the hybrid type with a mean diameter of 1.11 mm. The axial width of the hoop reinforcement is 80 mm, i.e. 0.20 times the maximum axial width of the tire. For the working and hooping layers, the hybrid reinforcing elements used consist of two spun aramid yarns of 330 tex each and one spun nylon yarn of 188 tex. The diameter of the hybrid reinforcing element obtained is 1.11 mm, its titre is 950 tex, its twist is 230 tpm, its elongation under 50 daN of force is 5.5% and its breaking force is 110 daN.

[0066] For the carcass layers, the hybrid reinforcing elements used consist of two spun aramid yarns of 330 tex each and one spun nylon yarn of 188 tex. The diameter of the hybrid reinforcing element obtained is 1.1 mm, its titre is 980 tex, its twist is 270 tpm, its elongation under 50 daN of force is 5.5% and its breaking force is 110 daN. Further hybrid reinforcements could also be used. It is notably conceivable to use reinforcements with a different twist, or even reinforcements having a different titre or a different number of each spun yarn.

[0067] The change from a flat profile to a concave profile of the working layer as described in the patent WO2013079351A1 causes a significant increase in the tension in the reinforcing elements at the centre of the working layers of around +15%, with the same stack of reinforcing elements of the crown layers and with the same mean radius of the radially external meridian profile of the tread.

[0068] Increasing the axial width of the hooping layer by 50 mm, changing its axial width from 80 mm to 130 mm, makes it possible to reduce excess tension by around 20% at the centre of the working reinforcement layers and by around 18% at the edge of the working reinforcement, but with the cost of the hooping reinforcing elements being increased by 65%. The use of a discontinuous hooping layer with an overall axial width of 130 mm, comprising a middle portion with an axial width of 80 mm and two lateral portions that are symmetrical with respect to the equatorial plane and have respective axial widths of 10 mm, each lateral portion being separated from the middle portion by a discontinuity having an axial width of 20 mm, makes it possible to reduce excess tension at the centre of the working layers by around 6% and at the edge of the working reinforcement by around 26%, with the increase in the cost of the hooping reinforcing elements also being limited to 25%.

[0069] The more the hooping layer is widened with respect to the equatorial plane by the introduction of discontinuities, the more the effect on the tension in the reinforcing elements at the end of the working reinforcement is favourable. The optimum position of the discontinuities in the hooping layer depends on the disposition and the width of the working layers.

[0070] The use of reinforcing elements for the hooping layer of different nature, made of aramid for example, makes it possible, in the same configuration as before, to reduce the excess tension at the centre of the working layers by around 36% and at the edge of the working reinforcement by around 49%.

[0071] For a hoop reinforcement made of aramid, one of the preferred variants is realized by using strips of 5 to 10 reinforcing elements laid over an overall width of 130 mm, in 6 portions that are distributed symmetrically with respect to the equatorial plane, these 6 portions being separated by discontinuities having axial widths of between 10 and 20 mm. The use of aramid and not of hybrid for the hoop reinforcement associated with this disposition makes it possible to reduce excess tension at the centre of the working layers by around 25% and at the edge of the working reinforcement by around 15%, achieving the level of excess tension close to that of the solution having a discontinuous hybrid hooping layer as described above, and thus meeting endurance criteria while reducing the cost of the hooping layer by 30% compared with that solution.