Resilient tires and wheels – Tires – resilient – Cushion and pneumatic combined
Reexamination Certificate
2002-11-21
2004-02-10
Johnstone, Adrienne C. (Department: 1733)
Resilient tires and wheels
Tires, resilient
Cushion and pneumatic combined
C152S454000, C152S456000, C152S517000, C152S544000, C152S547000, C152S552000, C152SDIG006
Reexamination Certificate
active
06688354
ABSTRACT:
BACKGROUND OF THE INVENTION
1. The Field of the Invention
The present invention relates to a tire intended to be mounted on a rim having at least one first frustoconical seat, the generatrix of which has an axially outer end which is closer to the axis of rotation than the other, axially inner, end. It also relates to a mounted assembly comprising such a tire mounted on a rim.
2. The Related Art
Such a tire is described in the commonly owned U.S. Pat. No. 5,785,781. It comprises at least one first bead, which is intended to be mounted on a first rim seat which is inclined towards the outside. The first bead is of conventional axial width, ends axially to the outside in a bead toe and has a bead seat, the generatrix of which has its axially outer end closer to the axis of rotation than its axially inner end. The generatrix is extended axially to the outside by an outer face defining the bead toe, such face forming with the axis of rotation an angle &ggr;, open radially and axially towards the outside, of less than 90°. The radial carcass reinforcement of the tire is anchored within each bead to at least one inextensible annular reinforcement element and has a meridian profile, when the tire is mounted on its operating rim and inflated to its operating pressure, with a direction of curvature which is constant at least in the sidewall extending the bead which ends in the toe and which is such that, in the bead, the tangent to the point of tangency of the profile with the inextensible annular element of the bead forms with the axis of rotation an angle &phgr;, which is open towards the outside, of at least 70°.
The bead of such a tire, and more particularly the structure of the hooking of the carcass reinforcement, may be variable. In the aforementioned United States patent, the carcass reinforcement is anchored to an inextensible annular reinforcement element (generally a coated bead wire) in conventional manner, that is to say, by winding the reinforcement around the element to form an upturn starting from the base of the element and rising radially towards the outside.
In this type of tire, the bead structures may be established in order to permit modification (increase) of the clamping of the bead toe on the mounting rim according to the tension of the carcass reinforcement, which results in having initial clamping on the rim of low value, knowing that the clamping will increase when the tire is inflated to its recommended pressure. These bead structures, when the conditions of travel of the tire are such that the beads are brought to high temperature, and at the end of their life, have deficiencies in terms of endurance which result from a certain unwinding of the carcass reinforcement from around the annular reinforcement element of the bead heel, linked with a reduction in the clamping, in particular when the upturn of the carcass reinforcement is short.
In order to overcome these drawbacks, there has been proposed in commonly-owned international patent application No. PCT/EP 99/10471 a novel tire comprising at least one first bead, the seat of which has a generatrix, the axially inner end of which lies on a circle of diameter greater than the diameter of the circle on which the axially outer end is located, the bead heel being axially to the inside. The toe of the bead is axially to the outside. A radial carcass reinforcement winding within each bead extends around at least one inextensible annular heel reinforcement element which is coated with rubber mix, passing from the inside to the outside to form an upturn, extending into a profiled element of rubber mix in the form of a wedge defined by two sides coming from an apex A which is located beneath the section of the annular element. The rubber mix forming the profiled element, axially adjacent to the annular element, has a Shore A hardness greater than the Shore A hardness(es) of the rubber mixes respectively radially above the element and the axially adjacent profiled element. Furthermore, when this tire is mounted on its operating rim and inflated to the recommended pressure, the meridian profile of the carcass reinforcement has a constant direction of curvature in the first bead and the sidewall extending it radially and has a tangent TT′ to the point of tangency T, of the profile with the annular element of the first bead which forms with the axis of rotation an angle &phgr;, which is open towards the outside, and is between 45° and 70°.
In this latter tire bead structure, the inclination of thee carcass reinforcement at the connection with the inextensible annular reinforcement element results in an increase in the axial component of the force exerted by the reinforcement on the annular reinforcement element and makes it possible effectively to increase the clamping of the carcass reinforcement under the annular reinforcement element. However, the fact of using an angle of opening of the carcass reinforcement of between 45° and 70° to the point of tangency with the annular element may result, in use, in problems of attack at the level of the outer surface of the tire in the region of the sidewalls thereof. In particular, and compared with the tire structure described in U.S. Pat. No. 5,785,781, for which the angle formed by the carcass reinforcement at the point of tangency with the inextensible annular element of the beads is greater than 70°, the structure described in the aforementioned international application No. PCT/EP 99/10471 results in having sidewalls which are more exposed to various scratching and friction phenomena which adversely affect the aesthetic appearance thereof and may also adversely affect the integrity of the tire. To these attacks of the scratching type there have to be added the impacts to which the sidewalls in accordance with this last described structure are subjected and which may adversely affect the integrity of said sidewalls, including that of the carcass reinforcement.
SUMMARY OF THE INVENTION
The tire, according to the invention and viewed in meridian section, comprises at least a first bead, the seat of which has a generatrix, whose axially inner end lies on a circle of diameter greater than the diameter of the circle on which the axially outer end is located, the bead heel being axially to the inside, whereas the bead toe is axially to the outside, and a radial carcass reinforcement winding within each bead around at least one inextensible, annular heel reinforcement element. The carcass reinforcement winding is coated with rubber mix, and passes from the inside to the outside to form an upturn, extending into a profiled element of rubber mix in the form of a wedge having a Shore A hardness greater than the Shore A hardness(es) of the rubber mixes respectively radially above said element and the axially adjacent profiled element. The meridian profile of the carcass reinforcement, when the tire is mounted on its operating rim and inflated to the recommended pressure, has a direction of curvature which is constant in the first bead and the sidewall extending it radially, and has a tangent TT′ to the point of tangency T of the profile with the annular heel-reinforcement element of the first bead which forms with the axis of rotation an angle &phgr; which is open towards the outside of between 45° and 70°, such tire being characterized in that, viewed in meridian section:
at least the sidewall extending the first bead comprises a profiled element having, viewed in section, substantially the form of a crescent defined by an inner face and an outer face, the profiled element extending between a point P
1
and a point P
2
, the point P
1
being located at a distance R
1
greater than the external radius Rte of the annular bead element and less than the radius R
0
of the circle on which are located the points of the carcass reinforcement axially most to the outside of the tire mounted on its rim and inflated to its use pressure, the point P
2
being located at a distance R
2
greater than the radius R
0
, the distances R
1
and R
2
being measured perpendicular to the ax
Drieux Jean-Jacques
Faure Jean-Claude
Pompier Jean-Pierre
Baker & Botts L.L.P.
Johnstone Adrienne C.
Michelin & Recherche et Technique S.A.
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