Resilient tires and wheels – Tires – resilient – Pneumatic tire or inner tube
Reexamination Certificate
1999-06-23
2001-10-23
Johnstone, Adrienne C. (Department: 1733)
Resilient tires and wheels
Tires, resilient
Pneumatic tire or inner tube
C152S526000, C152S527000, C152S532000, C152S548000, C152S556000
Reexamination Certificate
active
06305451
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a radial tire for heavy duty vehicles, and more particularly to an improved reinforcing structure including a carcass and belt capable of reducing tire weight without deteriorating other tire performance characteristics, such as tire strength, durability and the like.
In general, radial tires for heavy-duty vehicles such as trucks, buses and the like are provided on the radially outside of a carcass with a steel breaker (A) composed of four plies A
1
-A
4
of steel cords as shown in FIG.
6
. As to the cord angles of the four plies, the plies are arranged so that the cords form a stiff triangular construction. Thus, the breaker is very rigid and the tire is provided with a required strength.
On the other hand, nowadays, in connection with environmental issues, especially air pollution control, resource saving, waste disposal and the like, automobiles tire manufacturers are required to reduce tire weight, materials and the like.
If the number of breaker plies is merely decreased, naturally, the rigidity and strength become insufficient, and the steering stability decreases. For example, if the breaker ply number is decreased to two, in order to obtain the above-mentioned required strength, it is necessary to increase the cord thickness and cord count in each ply, and the resultant breaker renders the tire weight heavier than ever against expectation. Furthermore, in such a breaker, as the rigidity difference between the breaker ply and the adjoining carcass ply becomes too large, separation failure is liable to occur and the high-speed durability decreases.
It is therefore, an object of the present invention to provide a heavy duty radial tire, in which the tire weight is reduced without causing a deterioration in the strength (plunger strength), steering stability, high-speed durability and the like.
SUMMARY OF THE INVENTION
According to the present invention, a heavy duty radial tire is provided which comprises a tread portion, a pair of sidewall portions, a pair of bead portions, a carcass composed of a single ply of steel cords arranged radially at an angle of from 70 to 90 degrees with respect to the tire equator and extending between the bead portions, and a belt disposed radially outside the carcass in the tread portion and composed of two cross plies of steel cords laid parallel with each other at an angle of from 0 to 45 degrees with respect to the tire equator, wherein in at least a central part of the tread portion having 50% of the axial width of the belt, the total amount of steel of the belt plies is in the range of from 6 to 10 times the amount of steel of the carcass ply, and the thickness of the rubber between the radially adjacent belt cords and carcass cords is in the range of from 0.7 to 3.0 mm.
Preferably, the two belt plies are of substantially the same steel amount.
REFERENCES:
patent: H1333 (1994-07-01), Helfer et al.
Johnstone Adrienne C.
Sumitomo Rubber Industries Ltd.
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