Resilient tires and wheels – Tires – resilient – Pneumatic tire or inner tube
Reexamination Certificate
1997-12-23
2001-08-07
Ball, Michael W. (Department: 1733)
Resilient tires and wheels
Tires, resilient
Pneumatic tire or inner tube
C152S539000
Reexamination Certificate
active
06269856
ABSTRACT:
The present invention relates to a pneumatic tire, more particularly to an improved bead and lower sidewall structure which is capable of improving the bead durability, tire weight, crack resistance and the like and thus can be suitably employed in heavy-duty radial tires.
In heavy duty radial tires for trucks, buses and the like, in order to increase the durability of the bead portions, conventionally, reinforcing cord layers and a great volume of hard rubber are disposed in the bead portions as shown in FIG.
7
. However, in very severe service conditions under which such tires are often used, the increased rubber volume increases heat generation, and the bead durability is quickly lost. Further, the tire weight is inevitably increased, and the fuel consumption of the vehicles is also increased over time.
In Japanese Patent Publication No. JP-A-55-19685, a radial tire is disclosed, wherein a lower sidewall region is profiled so as to increase the flexibility of the sidewall portions. If the teachings thereof are applied to a heavy duty tire, as shown in
FIG. 12
, the rubber thickness t
1
is almost constant in a region y
1
which region extends from the tire maximum cross sectional width point P
1
to a relatively lower point P
2
, and from the point P
2
the thickness t
2
abruptly increases. As a result, the rubber volume can be decreased. However, as the tire surface changes from convex to concave at the point P
2
, and the concave part y
2
is positioned on the axially outside of the convex surface line e
1
, the bending deformation during running concentrates on the pint P
2
, and the bead durability is not good.
On the other hand, if the rubber volume is decreased, it is probable that such a tire is increased in the bending deformation in the lower sidewall region and upper bead region. As a result, the outer surface of the tire is liable to crack in that region, which sometimes induces bead damages such as loose end carcass ply. Further, it is impossible to retread the tires with cracked outer surfaces.
It is therefore, an object of the present invention to provide a pneumatic tire with improved durability and tire weight.
According to one aspect of the present invention, a pneumatic tire comprises
a tread portion,
a pair of sidewall portions,
a pair of bead portions with a bead core therein,
a carcass extending between the bead portions and turned up around the bead cores from the inside to the outside of the tire to form a pair of turnup portions and a main portion therebetween,
the outer surface of the tire provided with a mid-lower sidewall contour S
1
and a lower sidewall contour S
2
,
the mid-lower sidewall contour S
1
extending radially inwardly from the maximum cross sectional width point P
1
of the tire to a point P
2
along a circular arc line E
1
having the center on an axial line passing the maximum cross sectional width point P
1
,
the lower sidewall contour S
2
extending on the axially inside of the circular arc line E
1
from the point P
2
to a radially inner point P
3
, and
the thickness T measured from the outer surface of the tire to the main portion of the carcass is gradually increased from the point P
1
to the point P
2
.
Preferably, the bead portions are provided between the carcass main portion and each turnup portion with a bead apex made of hard rubber tapering radially outwardly to the radially outer end thereof, and the turnup portion extends radially outwardly beyond the radially outer end of the bead apex to form a parallel part, the parallel part extending radially outwardly from the radially outer end of the bead apex in substantially parallel with the carcass main portion, and the length L of the parallel part is in the range of from 0.5 to 5.0 times the maximum-section-width CW of the bead core.
REFERENCES:
patent: 4086948 (1978-05-01), Suzuki et al.
patent: 5392830 (1995-02-01), Janello et al.
patent: 5479977 (1996-01-01), Tamano et al.
patent: 5526863 (1996-06-01), Hodges
patent: 5622576 (1997-04-01), Lobb et al.
patent: 5885388 (1999-03-01), Ueyoko et al.
Ball Michael W.
Birch & Stewart Kolasch & Birch, LLP
Musser Barbara J.
Sumitomo Rubber Industries Ltd.
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