Resilient tires and wheels – Tires – resilient – Pneumatic tire or inner tube
Reexamination Certificate
2001-11-27
2004-08-24
Aftergut, Jeff H. (Department: 1733)
Resilient tires and wheels
Tires, resilient
Pneumatic tire or inner tube
C152S547000, C152S552000, C152S554000
Reexamination Certificate
active
06779574
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a tire mountable on a rim having at least one frustoconical seat, the surface of which is defined by a generatrix having an axially outer end closer to the axis of rotation than the axially inner end.
Such a tire has been described in Publication WO 94/13498. It comprises at least a first bead mountable on a first rim seat which faces the axial outside of the rim. The first bead has a seat with a generatrix inclined to have the axially outer end closer to the axis of rotation than the axially inner end. The bead seat generatrix extends axially towards the outside surface of the tire to meet an outer face delimiting the bead toe, the outer face forming with the axis of rotation an angle &ggr;, open radially and axially towards the outside and having a value of less than 90°. The radial carcass reinforcement of this tire, anchored in each bead to at least one inextensible annular bead ring, has, in meridian profile, when the tire is mounted on its service rim and inflated to its service pressure, a constant direction of curvature in the sidewall and bead terminated by the toe. The curvature of the meridian profile of the reinforcement is such that, in the bead, the tangent to the bead ring extending in the direction of the sidewall portion of the profile forms with the axis of rotation of the tire an angle &phgr; open axially outward of at least 70°.
The bead of such a tire and more particularly the structure for anchoring the carcass reinforcement in the bead may take different forms. In PCT Publication WO 95/23073 (U.S. Pat. No. 5,971,047), the radial carcass reinforcement is anchored to the inextensible bead wire by passing around the wire from the heel to the toe of the bead to form an upturn extending in a rubber section. The rubber section is made of rubber mix in the form of a wedge defined by two sides extending from an apex A located beneath the meridian section of the coated bead wire. The radially outer side forms with a line parallel to the axis of rotation passing through the apex A an acute angle &phgr;
1
, open radially towards the outside and between 20° and 70°, and the radially inner side forms with the same parallel line an acute angle &phgr;
2
, open radially towards the inside. The rubber mix forming the rubber section axially adjacent to the bead wire has a Shore A hardness greater than the Shore A hardness(es) of the rubber mixes located axially and radially above the wire and the rubber section.
The tire described in Publication WO 95/23073 has a carcass reinforcement upturn having a length such that the upturn is in contact with the total perimeter of the rubber section or wedge, that is, is wrapped around the wedge. The upturn thus contacts the two radially outer and inner sides of the rubber section and the side opposite the apex of the rubber section. The free end of the upturn is spaced axially from the apex of the wedge, that is, away from the point of intersection of the radially outer and inner sides of the wedge. The part of the upturn extending axially outward from the bead wire may, optionally, first form the radially outer edge of the rubber section or wedge and then the radially inner side of said rubber section, finally extending beyond the wedge apex around the bead wire. Alternatively, the part of the upturn extending axially outward from the bead wire may form firstly the radially inner side of the rubber section or wedge, then the side opposite the apex of said wedge, and then finally the radially outer side of said rubber section, ending in the same manner as previously described.
The combination of the carcass reinforcement meridian profile such as described in Publication WO 94/13498 with a carcass structure hooking around a wedge as described in Publication WO 95/23073 makes it possible to obtain a very good compromise between the handling properties of the tire inflated to its recommended pressure and the those properties when the tire is at a pressure below the intended operating pressure, or even zero pressure. Whether the initial clamping on the rim is zero or some greater value, the axial displacement of the anchoring bead wire of the carcass reinforcement in combination with the axial disposition of the rubber section reinforced by the upturn obtains clamping of the toe of the bead on the rim seat. The axial displacement of the anchoring bead may result from the tension of carcass reinforcement, generated, for instance, by the inflation pressure of the tire. The value of this clamping increases as a function of the tension force to which the carcass reinforcement is subjected, and may become great in the case of high tension, for instance when one of the side walls of the tire is placed under great tension by a transverse force.
U.S. Pat. No. 6,179,028 describes an alternative solution of a tire with a radial carcass reinforcement wound, at least in the first bead, around the bead ring passing from the inside to the outside to form an upturn extending along the radially inner side of the rubber section in form of a wedge, then along the side opposite the apex A, and then axially and radially on the outside, at least in part, of the rubber section radially above the rubber section or wedge. The upturn has an end located radially above the reinforcement annular ring of bead and axially between the straight line, extending the radially outer side of the wedge, and the straight line perpendicular to the axis of rotation and tangent at N to the annular ring.
SUMMARY OF THE INVENTION
The tires described above include additional rubber sections radially outside and axially outside the wedge section and bead wire which have a hardness significantly less than the hardness of the wedge section. Accordingly, upon an increase of tension of the carcass reinforcement, the bead wire displaces towards the outside of the bead but creates compression of the wedge section, which produces a self-clamping of the toe of the bead on the mounting rim. This effect has been demonstrated with respect to passenger car tires.
In tires requiring relatively high sidewall tension, for example, light truck tires with relatively high aspect ratios, the single ply construction disclosed in the above publications may not provide sufficient sidewall tensile strength. Tires made by conventional tire building processes will typically require a multiple ply construction to obtain sufficient carcass burst strength while retaining an acceptable carcass reinforcement cord spacing. A difficulty with adding a carcass reinforcement ply to tires of the type described above is that the added layer thickness on the axial inside of the bead wire positions the bead wire closer to the axially outer edge of the tire bead, which reduces the mechanical advantage of the self-clamping force of the tire bead on the rim bead seat.
The inventors have discovered relationships between the positions of the ends of the carcass plies that can minimize the effect of the added thickness and retain the necessary overall bead self-clamping force.
According to the invention, a tire with radial carcass reinforcement having beads with a heel portion on an axially inner side and a toe portion on an axially outer side comprises at least one bead wire coated with a rubber mix and a wedge formed of a rubber mix disposed axially outward of the at least one bead wire. The wedge is defined by two sides extending from an apex A located radially inward of the at least one bead wire, a radially outer side of the wedge defining, with a reference line parallel to the axis of rotation of the tire and passing through the apex A, a first acute angle &phgr;
1
open radially outside, and a radially inner side forming with the reference line a second acute angle &phgr;
2
, open radially toward the inside. A bead filler formed of a rubber mix is located axially and radially outside the coated bead wire and the wedge. The rubber mix forming the wedge has a Shore A hardness of at least 65 and which is greater than a Shore A hardness of the bead filler. The tire also
Bouvier Jean-Luc
Endicott James
Faure Jean-Claude
Fraisse Pierre
Teeple Robert Vanstory
Aftergut Jeff H.
Farley Felipe
Ferrell Martin
Fischer Justin
Michelin & Recherche et Technique S.A.
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