Resilient tires and wheels – Tires – resilient – Pneumatic tire or inner tube
Reexamination Certificate
1999-11-24
2001-10-02
Johnstone, Adrienne C. (Department: 1733)
Resilient tires and wheels
Tires, resilient
Pneumatic tire or inner tube
C152S554000
Reexamination Certificate
active
06296031
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a pneumatic radial tire in which a carcass ply (carcass layer) is constructed by a semiradial structure, and, more particularly, to a pneumatic radial tire promoting driving stability without being accompanied by an increase in mass or a reduction in productivity of the tire.
In pneumatic radial tires, a tire in which a carcass cord of a carcass ply is arranged at an angle less than 90 degrees relative to a tire equator is particularly referred to as a semi-radial tire. Generally, according to a conventional semi-radial tire for a passenger vehicle, as shown by
FIG. 3A
, two carcass plies
21
and
22
in which the carcass cords intersect with each other between the plies, are arranged to reach the bead portions
25
of the tire from a tread portion
23
via left and right side portions
24
. Both end portions are folded back to wrap the bead fillers
27
from the inner side to the outer side of the tire respectively around left and right bead cores
26
. Further, the tread portion
23
is arranged with two belt layers
28
over the entire periphery of the tire along the peripheral direction of the tire on the outer side of the outer side carcass ply
21
.
In the carcass plies
21
and
22
, a fold back portion
21
b
of the carcass ply
21
constituting the outermost side on an inner side of the bead core
26
in the bead portion
25
, is extended to the side of the tread portion
23
along an unfolded portion
21
a
of the carcass ply
21
(that is, main body portion). Further, a fold back portion
22
b
of the carcass ply
22
rides over a distal end
21
e
of the fold back portion
21
b
to cover the entire fold back portion
21
b
and is successively extended to the side of the tread portion
23
along the main body portion
21
a
. Therefore, a distal end
22
e
of the fold back portion
22
b
is disposed further radially toward the tread portion
23
relative to the distal end
21
e
of the fold back portion
21
b.
According to the above-described conventional semi-radial tire, when it is intended to improve the driving stability, as a general conventional method, a reinforcement layer comprising steel cords or fiber cords is arranged on the outer side of the bead filler
27
. However, such an additional arrangement of the reinforcement layer gives rise to an increase in a mass of the tire by that amount. This increases also the number of tire fabrication steps and thus results in a disadvantage resulting in a reduction in the productivity of the tire.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a pneumatic radial tire which has improved driving stability while keeping mass and productivity thereof at the same levels as those of a conventional pneumatic radial tire.
In order to achieve the above-described object according to an aspect of the invention, there is provided a pneumatic radial tire comprising a plurality of carcass plies in which carcass cords of the carcass plies are inclined to a tire equator by an angle equal to or more than 65 degrees and less than 90 degrees and intersect with each other, both end portions of the carcass plies being mounted to fold back from an inner side to an outer side of the tire respectively around left and right bead cores and wherein a fold back portion of the carcass ply constituting an outermost side on an inner side of the bead core is laminated on an unfolded portion of the carcass ply, the carcass cords of the carcass plies intersect with each other between laminated layers thereof and a length of the fold back portion is longer than any of the fold back portions of the remaining carcass plies.
According to the invention, the length of the fold back portion of the carcass ply constituting the outermost side on the inner side of the bead core and extended from the main body portion (that is, the unfolded portion of the carcass ply), is longer than any of fold back portions of the remaining carcass plies. Therefore, a laminated layer region in which carcass cords intersect with each other between laminated layers of the main body portion and the fold back portion can be wider than that of the conventional tire of FIG.
3
A and FIG.
3
B. The laminated layer region in which the carcass cords intersect with each other in this way is provided with the flexural rigidity larger than that of the laminated layer region in which the carcass cords are parallel with each other between the layers. Therefore, according to the invention, compared with the conventional tire of FIG.
3
A and
FIG. 3B
, the lateral rigidity of the side of the tire can be increased and the driving stability can be promoted.
Further, the number of the carcass plies and the number of tire fabrication steps remain the same as those in the conventional tire. Therefore, the tire mass is not increased and the productivity of the tire is not deteriorated.
REFERENCES:
patent: 4854362 (1989-08-01), Carolla et al.
Arent Fox Kintner & Plotkin & Kahn, PLLC
Johnstone Adrienne C.
The Yokohama Rubber Co. Ltd.
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