Resilient tires and wheels – Tires – resilient – Pneumatic tire or inner tube
Reexamination Certificate
2001-11-21
2003-07-29
Johnstone, Adrienne C. (Department: 1733)
Resilient tires and wheels
Tires, resilient
Pneumatic tire or inner tube
C152S539000, C152S550000
Reexamination Certificate
active
06598643
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a tire comprising at least one tread joined to two beads by means of two sidewalls and a carcass reinforcement, said tire being able to be used with or without an independent inner tube and being intended, after mounting on a standardized rim and after inflation, to be fitted on any vehicle capable of rolling.
Application FR A 2 771 150, filed Nov. 14, 1997, describes a tire which is intended to be mounted on a rim of axial width L, with rim seats forming an angle &ggr; with the axis of rotation such that 0°≦&ggr;≦16°, and rim flanges with rounded hooks. Said tire comprises a tread joined to two beads by two sidewalls and at least one carcass reinforcement formed of at least one ply of reinforcement elements, each bead being devoid of a bead wire, and said carcass reinforcement having in each bead a meridian profile which is curved axially and radially from the outside to the inside to form an axially inner edge located in an angle &agr; open axially and radially towards the inside, one of the sides of which is parallel to the axis of rotation, and of a value of at most 25°. Said carcass reinforcement is reinforced in each bead, at least radially to the outside and axially to the inside, by at least one first continuous additional layer of meridian profile substantially parallel to the meridian profile of said carcass reinforcement in the bead and comprising at least one first section composed of at least one ply formed of inextensible reinforcement elements forming an angle of between −2.5° and +2.5° with the circumferential direction, the radially upper end of said additional ply being distant from the axis of rotation by an amount at least equal to 0.96 times the distance between said axis and that point of the corresponding flange of the mounting rim which is farthest from said axis of rotation, and the axially inner end being distant from the equatorial plane by an amount at most 0.43 times the width L of the mounting rim.
It is then possible better to control the distribution of the contact pressures between the rim and the tire at the level of the respective rim and bead seats while permitting an improvement in the resistance to unwinding of the carcass reinforcement in the event of a high degree of heating of the beads without using anchoring bead wires for the carcass reinforcement.
In the case of tires having a high recommended inflation pressure, the document cited mentions that the first additional layer may be formed of two sections of several additional plies of inextensible reinforcement elements, superposed on one another, the lengths of which may or may not be the same. The presence of another continuous additional reinforcement layer arranged radially to the inside and axially to the outside has proved very advantageous. Said layers are for the most part formed of inextensible cables, preferably metal ones, forming an angle of between −2.5° and +2.5° with the circumferential direction.
Although such structures make it possible to solve the problems posed, they do not have sufficient endurance, owing to the appearance and propagation of breaks in the carcass reinforcement due to the variation of curvature of the meridian profile of said reinforcement during travel, which variation is between the curvature when the meridian in question passes into the contact ellipse and when it is opposite to said ellipse.
SUMMARY OF THE INVENTION
In order to overcome said problems of endurance, the tire according to the invention, which is intended to be mounted on a rim, the seats of which form an angle &ggr; with the axis of rotation such that 0°≦&ggr;≦16°, and the rim flanges of which have rounded hooks, comprising a tread joined to two beads devoid of bead wires by two sidewalls and at least one carcass reinforcement formed of at least one ply of reinforcement elements, and having in each bead a meridian profile which is curved axially and radially from the outside to the inside to form an axially inner edge located in an angle open axially and radially towards the inside, one of the sides of which is parallel to the axis of rotation, and of a value of at most 25°, said carcass reinforcement being reinforced in each bead at least radially to the outside and axially to the inside by at least one first continuous additional layer, composed of at least one ply formed of inextensible reinforcement elements forming an angle of between −2.5° and +2.5° with the circumferential direction, is characterized in that said carcass reinforcement is also, radially to the outside and axially to the inside, reinforced by a second continuous additional layer, composed of at least one ply formed of inextensible radial reinforcement elements, the two additional layers having meridian profiles substantially parallel to the meridian profile of the carcass reinforcement in the bead and the radially upper ends of said first and second additional layers being distant from the axis of rotation by amounts at least equal respectively to 0.96 times and 1.20 times the distance between said axis and that point of the corresponding flange of the mounting rim which is farthest from said axis of rotation.
“Rim flange, viewed in meridian section” is to be understood to mean the assembly formed by the section substantially perpendicular to the axis of rotation extended, firstly, radially to the outside, by a circular section, forming what is sometimes referred to as the rim hook, and secondly, radially to the inside, by the arc of a circle connecting the axially outer end of the rim seat to said assembly.
“Meridian profile of a carcass reinforcement in a bead” is to be understood to mean the meridian profile of the geometric center line of said reinforcement, viewed in meridian section, said profile being considered radially to the inside of a straight line parallel to the axis of rotation of the mounting rim and of the tire passing through the point of the rim hook, corresponding to the bead in question, farthest from the axis of rotation.
“Inextensible reinforcement element” is to be understood to mean a cable or a monofilament having a relative elongation of at most 1.5% under a force of 20% of the breaking load. The first and second additional layers will preferably be formed of metal cables or monofilaments, preferably of steel, in the case of tires of the “heavy vehicle” or “construction” type, but may advantageously be formed of textile elements, preferably of aromatic polyamide, in the case of tires for aeroplanes, agricultural tractors or passenger cars, for example.
The endurance of the tire will be improved further if the thickness of rubber existing between the center line of the meridian profile of the carcass reinforcement and the outer wall of the bead, over the length of contact between the bead and the rim, is reduced by the length of contact between the bead and rim seats respectively, which is at least equal to 0.02% of the maximum axial width of the carcass reinforcement.
A large number of rims and tires may be covered by the invention; the meridian profile of the assembly formed by the carcass reinforcement and the additional layers, which profile is very closely linked to the profile of the carcass reinforcement, will, within a bead, be advantageously adapted to the meridian profile of the rim on which said bead will be mounted. The meridian profile of the additional plies in effect does not differ from the meridian profile of the carcass reinforcement, except by the possible variation of the rubber decoupling layer(s), whether or not reinforced, existing between the two reinforcements, which explains why said profiles are said to be substantially parallel. The meridian profile of the second additional layer may be strictly parallel to the profile of the carcass reinforcement, with a single layer of rubber of constant thickness separating the two profiles. The meridian profile of the second layer may be substantially parallel to the profile of the carcass reinforcement, with one or more p
Baker & Botts LLP
Johnstone Adrienne C.
Michelin & Recherche et Technique S.A.
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