Resilient tires and wheels – Tires – resilient – Pneumatic tire or inner tube
Reexamination Certificate
2002-05-03
2004-07-27
Johnstone, Adrienne C. (Department: 1733)
Resilient tires and wheels
Tires, resilient
Pneumatic tire or inner tube
C152S531000, C152S532000, C152S533000, C152S537000
Reexamination Certificate
active
06766840
ABSTRACT:
BACKGROUND OF INVENTION
The invention concerns a vehicle tire and, notably, a tire whose architecture is optimized in order to reinforce its endurance and speed resistance.
It is now common for tires of passenger cars designed to run at high speeds to embody an additional ply of circumferentially oriented cords. That ply can be placed above the crown reinforcement plies at angles also commonly used.
In such a configuration, that ply of circumferentially oriented cords is the radially outermost ply of the tire crown.
A break of one or more of those circumferential cords on rolling can shorten the lifetime of the tire. In fact, such breaks reduce the binding of the crown, but can also lead to seepage of water along the circumferential cords, which can entail wire corrosion phenomena.
A zone sensitive to circumferential cord ply damage is the lateral end of the working ply closest to the circumferential cords, owing to the short distance between those circumferential cords and the ends of the wire cords of the working ply. The damage to the circumferential cords can be due, notably, to abrasive contacts with the ends of the cords of the ply at the outermost angle.
Tire designers have proposed various arrangements for keeping the circumferential cords away from the ends of the reinforcing plies at angles from the crown, notably, through the addition of rubber flanging layers.
These arrangements make the tire more difficult to manufacture and increase its cost. Furthermore, the shaping operations make industrial control of these complementary operations subject to time variations.
SUMMARY OF THE INVENTION
The object of the present invention is to present an economical arrangement for solving that technical question.
In what follows, “cord” is understood to mean monofilaments as well as multifilaments, or assemblages like cables, yarns or even any type of equivalent assemblage, whatever the material and treatment of those cords, like, for example, surface treatment or coating or pre-sizing to promote adherence to the rubber.
“Rubber bonding layer” for a given reinforcing ply is understood to mean the rubbery compound in contact with the ply reinforcing cords, adhering to the latter and filling the interstices between adjacent cords.
“Contact” between a cord and a rubber bonding layer is understood to mean the fact that at least one part of the outer circumference of the cord is in close contact with the rubber compound constituting the rubber bonding.
“Titer” is understood to mean the weight in grams of one thousand meters of a cord. The titer is expressed in tex. The stress undergone by a cord or the modulus of that cord is expressed in “cN/tex”, cN meaning centinewton.
“Laying pitch p” of a generally circumferentially oriented and spiral-wound cord is understood to mean the distance transversely separating the axes of two adjacent cord turns. The laying pitch is the inverse of “laying density d,” which corresponds to the number of cord turns contained in a given axial width: p=1/d. Usually, d is expressed in number of cords per decimeter (f/dm) and p by millimeters; thus, p=100/d.
The “high-temperature contraction potential” of a textile cord called “CS” is understood to mean the relative variation of length of a textile cord positioned, under a prestress equal to the half-sum of the titers of each of the elementary fibers, between the platforms of a furnace (TESTRITE type apparatus) regulated at a constant temperature of 185 ±0.5° C. The CS is expressed in % by the following formula:
CS
(%)=100×|
L
1
−L
0
|/L
0
where L
0
is the initial length of the adhered cord at room temperature under a prestress equal to the half-sum of the titers of each of the elementary fibers and L
1
is the length of that same cord at 185° C. The length L
1
is measured at the end of a cord stabilization time at temperature of 185° C., equal to 120 s±2%. The standard deviation on the measurement of CS is ±0.15%.
That potential is a direct consequence of the set of operations that the cord has undergone on its elaboration or on its use.
The invention concerns a tire containing a crown extended by two sidewalls and two beads, a carcass anchored in the two beads, in which the crown radially comprises from inside:
at least one reinforcing ply of axial width L, formed by parallel cords oriented at an angle &agr; relative to the circumferential direction of between 10 and 75 degrees, and
at least one ply of cords obtained by spiral winding of the cords in a generally circumferential direction, arranged radially outside relative to the reinforcing ply and extending axially beyond the reinforcing ply.
This tire is characterized in that, in the zones axially placed relative to the equatorial plane P of the tire at a distance ranging between L/2−h and L/2+H, the laying pitch of the cords is greater than or equal to the axial distance H+h, in that the values of H and h are equal or over 2 mm and in that said ply of cords arranged in a generally circumferential direction has an axial width strictly over L+2 H.
The fact that in this zone the laying pitch of the circumferentially oriented and spiral-wound cords is greater than or equal to the axial distance H+h means that, from one side of that zone to the other, only one circumferential cord turn has been arranged at most. This embodiment therefore appreciably diminishes the likelihood of an accidental break of that cord due to an abrasive contact between that cord and a cord of the adjacent ply and thus reinforces the resistance of the tire as a whole.
The invention also concerns a similar tire in which the ply of circumferential cords comprises, at least on one side of the equatorial plane P of the tire, a first spiral winding extending from the equatorial plane P to an axial distance of L/2−h and at least a second spiral winding axially extending outward beyond an axial distance L/2+H from the equatorial plane of the tire.
That embodiment has the advantage of not entailing any risk of contact between the cords of the circumferential ply and the axial end of the cords of the reinforcing ply formed by cords oriented at angle &agr;. Industrial production is, however, somewhat longer by reason of the interruption and resumption of laying of the circumferential cords.
The laying pitch of the ply of generally circumferentially oriented spiral-wound cords is advantageously less in the zone axially placed outside beyond the axial distance L/2+H than the laying pitch of the cords in the center zone of the tire crown.
That makes it possible to compensate for the absence of binding opposite the axial end of the crown reinforcing ply of width L in order to obtain a uniform binding. Binding can also be increased in the shoulder zone in order to improve resistance to high speeds of the tire.
For a similar purpose, the laying pitch of the circumferential cords can also be reduced in the zone placed axially placed in proximity to the axial distance L/2−h.
When the tire crown includes a second reinforcing ply of axial width L′, radially inward from the first, formed by parallel cords oriented at an angle &bgr; of between 10 and 75 degrees, the ply of circumferential cords can extend axially within or beyond distance L′/2 from the equatorial plane of the tire, depending on the level of high-speed resistance sought.
According to one particular embodiment, the tire tread is, on at least a given axial zone of the crown, in direct contact with the circumferentially oriented cords. That facilitates manufacture of the tire by reducing the number of products to be laid. When the tread contains a first compound intended to come in contact with the road, as well as an underlayer radially placed under the first compound, it is the underlayer which is advantageously in direct contact with the circumferentially oriented cords.
The so-called underlayer compounds are intended to improve different performances like the consumption or drift rigidity of the tires.
The p
Costa Pereira Pedro
Jardine David
Csontos Alan A.
Farrell Martin
Johnstone Adrienne C.
Michelin & Recherche et Technique S.A.
Remick E. Martin
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