Resilient tires and wheels – Tires – resilient – Pneumatic tire or inner tube
Reexamination Certificate
1998-06-19
2001-07-31
Johnstone, Adrienne C. (Department: 1733)
Resilient tires and wheels
Tires, resilient
Pneumatic tire or inner tube
C152S526000, C152S527000, C152S528000, C152S538000
Reexamination Certificate
active
06267165
ABSTRACT:
TECHNICAL FIELD
The present invention relates to pneumatic automobile tires, for use on paved surfaces, comprising a radial ply carcass, a tread disposed radially outwardly of the crown region of the carcass, and a belt assembly interposed between the tread portion and the crown region of the carcass in circumferential surrounding relation to the carcass. The invention relates more specifically to low aspect ratio tires.
BACKGROUND ART
Belt assemblies including a folded ply are well known in the art. In one prior art embodiment the folded ply is reinforced with cords of high modulus material and has an overall width at least equal to that of the tread. Each of its lateral sides is folded back in a radially outward direction, around two unfolded so-called single cut plies. The reinforcing cords of the folded ply form an angle of 20 to 60 degrees, and those of the two single cut plies form opposed angles, respectively of 15 to 28 and minus 15 to 28 degrees, all with respect to the equatorial plane of the tire. Tires comprising folded plies in their crown region have been found to be particularly durable when subjected to high revolution speeds. They have also improved resistance to separations at the axial edges of a belt assembly.
Because of material limitations, early prior art tire constructions tended to be robust, i.e. the tires were heavy and many components were used to provide reinforcement in specific locations in the tire. Such constructions tend to have a high rolling resistance, which lowers fuel economy, and the bulk of the construction had a tendency to limit handling response, and the materials cost was high because of the quantities of materials used.
It is a continuing goal in the art, to find new, lightweight and high strength materials, and to find suitable uses for such materials in tires, such that the weight of tires can be reduced while other properties are maintained
In the development of the present invention, the inventors noticed that experimental reinforcement material they evaluated had an excellent fatigue resistance. This property made the material suitable for application of a relatively low twist to the cord, which made it possible to maintain durability and elongation characteristics in a lower density material. These properties are necessary for reinforcement used in the belt of a tire. Having noticed that handling properties of a tire improved when reinforcement cords in a belt were reduced from 1670 dTex to 1100 dTex, the inventors speculated that further reduction of the linear density of the reinforcement cords would further improve handling. In the tires constructed, the weight of the tire was reduced, and handling and high-speed properties (as illustrated by lap speeds) were improved.
Other objects of the invention will be apparent from the following description and claims.
PRIOR ART
EP 237,599 teaches polyaromatic amide fiber cords reinforcing a belt, which is folded over a cut, carbon fiber cord reinforced belt.
U.S. Pat. No. 4,644,988 teaches a folded glass belt structure in a tire.
Oare et al, in U.S. Pat. No. 5,115,853, and references cited therein, teach the use of overlays in tires. The references teach various materials that can be used, and various gauges of such materials that are used in building tires, as well as various tire constructions.
Breny, in U.S. Pat. No. 5,437,321 teaches a high performance tire where an overlay is used in place of a cut belt, and a folded belt is folded over edges of the overlay.
Roesgen et al. in U.S. Pat. No. 5,332,018 teach a tire construction using a folded belt structure which comprises a folded belt, a cut belt, and an overlay, having some embodiments wherein the overlay is located between the folded edges of a folded belt.
Hubbell et al, in U.S. Pat. No. 5,323,829 teach a high performance tire having a folded belt structure wherein one embodiment comprises a folded belt folded over the edges of a cut belt, and an overlay covering the full width of a folded belt, including the folded over edges.
EP-A-92 498 discloses a first tread reinforcing ply folded around a second tread reinforcing ply, such that the first ply envelops the second ply. The reinforcing cords of the first ply form an angle of 20 to 60 degrees and those of the second ply form an angle of 0 to 10 degrees with respect to the equatorial plane of the tire. EP-A-412 928 discloses a textile overlay structure which is reinforced with cords made of aramid; the cords have a twist multiplier (as defined here below) between 6 and 14 and at least one of the yarns included in the cords has a twist of at least 14 turns per inch (TPI) (551 turns per meter (TPM)).
LU 85 964 describes a tire having an overlay structure disposed radially outwardly of the belt assembly. Helical convolutions of a ribbon are wound axially across two single cut plies such that the convolutions are in abutting contact with each other. The ribbon is reinforced with cords of textile material. An overlay structure wherein the helical convolutions overlap is for instance disclosed in EP 333 628.
DISCLOSURE OF INVENTION
The present invention provides a pneumatic automobile tire having an aspect ratio below 65, comprising at least one radial ply carcass, a tread disposed radially outward of the crown region of the carcass, and a belt assembly having an overall width substantially equal to the tread width (TW) interposed between the tread and the crown region in circumferential surrounding relation to the carcass. The belts are reinforced with 420 to 1100 dTex aramid cords, wherein the cords have a toughness as measured in MPa of 30 to 50, an initial modulus as measured in MPa of 15,000 to 40,000, a tenacity as measured in cN/Tex of 140 to 200 and a dynamic flex fatigue (ASTM, Scott's flex tester) retained break strength of 50 to 100%. The belts used in the belt assembly are reinforced with reinforcement cords extending parallel to one another and making an angle of 10° to 40° with respect to the equatorial plane (EP) of the tire. In an illustrated embodiment, the belt assembly comprises a folded belt having folded portions on each lateral side folded radially over a cut belt. The axially outer portions of the folded belt are folded in a radially outward direction, and are disposed radially outward of the cut belt.
In alternative embodiments, an overlay or a spirally wound overlay may be used in the tire construction. The overlay may be made from elastomeric material reinforced by textile cords and may form at least one annular layer; the cords making an angle of 0° to 5° with respect to the equatorial plane (EP) of the tire.
Also provided is a treated aramid cord, which is prepared to be used as a tire reinforcement.
DEFINITIONS
“Belt” refers to plies of parallel cords, woven or unwoven, underlying the tread, unanchored to the bead, and having cord angles of from 17 to 27 degrees with respect to the equatorial plane of the tire.
“Cut belt ply” refers to a belt having a width less than the tread width, which lies flat over the carcass plies in the crown area of the tire.
“Crown” refers to that portion of the tire within the width limits of the tire tread, in the area of the tire tread.
“Carcass ply” refers to plies of parallel cords anchored to both beads of the tire.
“Overlay” refers to fabric or fiber reinforced rubber having a width substantially equivalent to the tread width which is placed over the belt structure in a tire to minimize delamination at the belt edges and to provide a smoother ride.
“High Performance Automobile” refers to stockcars that are designed for high speed such as Corvettes, Lamborghini, Ferrari, Porsche, etc.
REFERENCES:
patent: 5355922 (1994-10-01), Kogure et al.
Boehlefeld Robert John
Hamiel Charles Elmer
Westgate Walter Kevin
Johnstone Adrienne C.
The Goodyear Tire & Rubber Company
Wheeler David E
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