Resilient tires and wheels – Tires – resilient – Pneumatic tire or inner tube
Reexamination Certificate
2000-09-20
2003-09-23
Aftergut, Jeff H. (Department: 1733)
Resilient tires and wheels
Tires, resilient
Pneumatic tire or inner tube
C152S542000, C152S546000, C152S552000, C152S555000
Reexamination Certificate
active
06622765
ABSTRACT:
BACKGROUND OF INVENTION
The present invention concerns a tire with radial carcass reinforcement, more particularly a “Heavy Duty” tire designed for mounting on vehicles such as trucks, road tractors, buses, trailers and others, and in which a new reinforcement structure of the beads is adopted with a view to improving the endurance of the said beads.
In general a tire of the type considered comprises a carcass reinforcement formed of at least one ply of metallic cables anchored in each bead to at least one bead wire with a turn-up. Radially above the carcass reinforcement is a crown reinforcement consisting of at lest two plies of metallic cables crossed from one ply to the next and forming angles between 10° and 45° relative to the circumferential direction. The turn-ups of the carcass reinforcement are generally reinforced by at least one ply of metallic cables orientated at a slight angle relative to the circumferential direction.
If only one bead reinforcement ply is present, this can be located along the carcass reinforcement turn-up with a radially upper end over or under the radially upper end of the turn-up of the carcass reinforcement. As for the radially lower end of such a ply, this is generally located either on a line parallel to the rotation axis and passing approximately through the center of gravity of the median section of the anchoring bead wire of the carcass reinforcement, in the case of a tire having beads designed to be mounted on rim seats inclined at 15°±2°, or on a line parallel to the rotation axis passing through a point located between the center of gravity of the median section of the anchoring bead wire and the point where the axial width of the carcass reinforcement is widest, in the case of a tire having beads designed to be mounted on rim seats inclined at 0° or at 5°±1°. In this second case the bead reinforcement ply is then wrapped around the bead wire so that it has an axially outer part and an axially inner part, the radially upper end of the axially inner part generally being located below the radially upper end of the axially outer part.
The aim of the known solution is to avoid de-radialization of the carcass reinforcement turn-up cables and to minimize the radial and circumferential deformations undergone by the end of the said turn-up and by the layer of rubber outside which covers the bead and ensures its contact with the rim.
In other cases the metallic reinforcing ply has been replaced by several plies, for example made of textiles, located axially either on the same side as the turn-up or on either side thereof, or again partly along the turn-up and partly along the carcass reinforcement. Another variant consists in positioning two reinforcement plies along the turn-up on either side thereof, and a third ply along the carcass reinforcement axially on the outside.
The endurance of tire beads can also be improved by arranging along the carcass reinforcement two reinforcing plies, while the turn-up of the said reinforcement is not reinforced.
Due to the progress achieved and to the fact that certain types of rolling surfaces have been made less harsh where tire tread is concerned, the life of “Heavy Duty” tires has become such that it is again necessary to improve the bead endurance, more especially in tires subjected to prolonged rolling which often results in high bead temperatures by virtue of the temperatures reached by the rims to which they are fitted.
According to French patent application FR 2 730 190 the said improvement can be achieved by the presence in the beads of at least one reinforcement ply formed of circumferential metallic elements wrapped around the bead wire outside the rolled-up part of the carcass reinforcement, such that the ends, respectively, of the axially outer and axially inner parts are radially located above a line parallel to the rotation axis and passing through the point of the bead wire furthest from the said rotation axis. As is known, the carcass reinforcement, formed of radial wires or cables is therefore at the level of its contact surface with the bead wire formed of essentially circumferential elements which are generally metallic in the form of wires, cables, ribbons or rolled-up strips inserted between the said elements with essentially circumferential orientation and the additional ply of metallic elements, they too being circumferential. This structure therefore enables the tensile forces undergone by the carcass reinforcement to be absorbed and so minimizes all the deformations at the ends of the carcass reinforcement turn-up regardless of the rolling conditions.
The same application FR 2 730 190 describes an advantageous variant for reinforcing the bead, in which the end of the axially inner part of the ply of circumferential elements is covered by a reinforcing ply
9
consisting of radial metallic cables.
To obtain more effective stiffening of the beads and the low parts of the side-walls of a tire with radial carcass reinforcement, the patent FR 1 594 780 proposes that the bead reinforcement armatures, located axially outside the main part of the carcass reinforcement and axially inside the turn-up of the said reinforcement, should consist of radial reinforcement elements.
To improve the endurance of the beads of radial tires for heavy vehicles, application EP 0 202 925 also proposes the use of two additional bead reinforcement armatures, a first consisting of metallic elements and a second armature of elements inclined relative to the median direction, such that the radial positions of the radial ends of the said armatures are specified.
SUMMARY OF THE INVENTION
This invention proposes another solution, which is technically and industrially optimum for tires with beads designed to be mounted on rims of the type called flat or whose rim seats are inclined at 5°.
To improve the endurance of a tire designed to carry heavy loads, according to the invention the said tire comprises at lest one radial carcass reinforcement formed of at least one ply of inelastic reinforcing elements anchored in each bead to a bead wire to form a turn-up whose end is located at a radial distance H
RNC
from the base of the bead, and each bead is reinforced by at least two additional reinforcement armatures, at least one first armature formed of a single ply of radial inelastic metallic reinforcing elements wrapped around the anchoring bead wire of the carcass reinforcement outside the said carcass reinforcement and forming two parts such that the radially upper end of the axially outer part is located radially a distance H
LE
from the base of the bead equal to at least 65% of the distance H
RNC
, and at least one second armature formed of elements which make an angle &agr; with the circumferential direction such that 0°≦&agr;≦45°, characterized in that when viewed in median section, the second additional bead reinforcement armature, which is not wrapped around the said anchoring bead wire, is formed of at least one ply of circumferential metallic reinforcement elements, which are sections or bundles of sections of metallic cables whose circumferential length is smaller than the circumferential length of the median axis of the bead wire.
Reinforcement elements are considered radial if the angle they make with the tire's circumferential direction is within the range 80°-100°.
The term ‘armature wrapped around the bead wire’ means an armature forming two parts, an axially inner and an axially outer part, whose respective ends are radially above a line parallel to the rotation axis and passing through the center of gravity of the cross-section of the anchoring bead wire.
Similarly, in the context of the invention, the radially upper end of the part of a bead reinforcement armature which can consist of one or more plies is understood to mean the end of the armature ply furthest from the rotation axis, and the armature plies can have upper ends within a radial distance range of at most 20 mm. Likewise, the radially lower end of a bead reinforcement armature is the lower end of the ply lea
Aftergut Jeff H.
Baker & Botts LLP
Compagnie Generale des Etablissements Michelin--Michelin & Cie
Fischer Justin
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