Resilient tires and wheels – Tires – resilient – Pneumatic tire or inner tube
Reexamination Certificate
1999-09-08
2001-03-06
Johnstone, Adrienne C. (Department: 1733)
Resilient tires and wheels
Tires, resilient
Pneumatic tire or inner tube
C152S554000
Reexamination Certificate
active
06196289
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a pneumatic tire, more particularly to a run-flat tire having an improved sidewall reinforcing structure.
BACKGROUND OF THE INVENTION
In order to improve run-flat performance such as runable distance of a pneumatic tire, as shown in
FIG. 4
, a tire which has a sidewall portion (s) reinforced with a relatively thick rubber layer (g) has been proposed, wherein this thick rubber layer (g) is disposed on the axially inside of the carcass to extend along the inside of the tire.
In this reinforcing structure, however, under run-flat conditions, damage starting from a carcass ply turnup edge (f
1
) is liable to occur when the edge (f
1
) is positioned in the sidewall portion, especially it is positioned around the maximum tire section width point. Further, the rubber layer (g) has a maximum thickness at the maximum tire section width point. Under flat conditions, however, bending deformation becomes larger in the tire shoulder portion than the maximum tire section width portion. In other words, the bending deformation concentrates on the shoulder portion. Thus, in this structure, the tire has a tendency to have a week point in the shoulder portion.
Such drawbacks may be eliminated by for example covering the edge (f
1
) with an additional carcass ply and increasing the thickness of the rubber layer (g). However, other problems such as an increase in the tire weight and deterioration of ride comfort and dynamic performance under normal conditions, arise.
SUMMARY OF THE INVENTION
It is therefore, an object of the present invention to provide a run-flat tire improved in run-flat performance, e.g. runable distance, durability and the like without increasing the tire weight and deteriorating running performance under normal conditions.
According to one aspect of the present invention a run-flat tire comprises
a tread portion,
a pair of sidewall portions,
a pair of bead portions with a bead core therein,
a carcass comprising an inner ply and an outer ply each made of organic fiber cords,
a belt disposed radially outside the carcass in the tread portion,
sidewall reinforcing rubber layers disposed in each said sidewall portion,
each of the inner ply and outer ply extending between the bead portions through the tread portion and sidewall portions and turned up around the bead core in each bead portion from the inside to the outside of the tire to form a pair of turnup portion and a main portion therebetween,
the turnup portions of the inner ply extended into between the belt and the carcass and each having a radially outer end secured therebetween,
the sidewall reinforcing rubber layers including:
an inside layer disposed axially inside the main portion of the inner ply;
a middle layer disposed between the main portion of the inner ply and the main portion of the outer ply; and
an outside layer disposed axially outside the main portion of the outer ply,
at least one of the sidewall reinforce rubber layers having a radially outer end located beneath the belt,
at least one of the sidewall reinforce rubber layers having a radially inner end located radially outward of the bead core but radially inward of a maximum tire section width point,
at the maximum tire section width point, the total of the thicknesses of the inside layer, middle layer and outside layer being not less than 50% of the thickness of the sidewall portion.
Preferably, the thickness of the sidewall portion at a point at 75% of the tire section height is 1.0 to 1.2 times the thickness of the sidewall potion at the maximum tire section width point. The total of the thicknesses of the inside layer, middle layer and outside layer is not less than 40% of the thickness of the sidewall portion at a point at 75% of the tire section height.
Further, it is preferable that the outer end(s) of at least one, preferably two, more preferably three of the reinforcing rubber layers is(are) disposed in a region beneath a breaker belt. It is preferable that the inner end(s) of at least one, preferably two, more preferably three of the reinforcing rubber layers is(are) disposed in a region radially inward of the maximum tire section width point but radially outward of the radially outside of the bead core. And it is more preferable that both the outer and inner ends of at least one of the reinforcing rubber layers are disposed in the above-mentioned two regions.
REFERENCES:
patent: 5871602 (1999-02-01), Paonessa et al.
Birch & Stewart Kolasch & Birch, LLP
Johnstone Adrienne C.
Sumitomo Rubber Industries Ltd.
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