Low-aspect tire

Details Low-aspect tire Low-aspect tire

1999-05-26

2001-07-10

Knable, Geoffrey L. (Department: 1733)

Resilient tires and wheels

Tires, resilient

Anti-skid devices

C152S523000, C152S525000, C152S543000, C152S554000

Reexamination Certificate

active

06257290

ABSTRACT:

The present invention relates to a pneumatic tire, more particularly to a low-aspect tire improved in durability.
In radial tires having a low aspect ratio of under 55% especially under 40%, edges of reinforcing cord layers such as carcass, belt and the like and edges of rubber layers such as tread rubber, sidewall rubber, bead apex rubber, clinch rubber and the like inevitably concentrate in a narrow region, and cracks and separation failure and the like are liable to occur between such layers. Thus, it is difficult to improve the durability of tire.
On the other hand, as shown in
FIG. 12
, such low aspect radial tires are often provided with a part (c) which overhangs a rim flange (JF) of a wheel rim (J) in order to decrease vertical tire deflections.
FIG. 12
shows a conventional structure in which: the above-mentioned overhanging part (c) is formed by a relatively hard clinch rubber (d) which is disposed along the axially outside of the bead portion (b) to a position (e) above the rim flange (JF); a sidewall rubber (i) is disposed along the outer surface of the tire to extends from the position (e) to an axial edge of a belt (f); a tread rubber (g) is disposed radially outside the belt (f); and a wing rubber (h) is disposed over the sidewall rubber (i) in the tire shoulder.
In a low-aspect radial tire having such overhanging part, bending deformation during running concentrates in an upper sidewall region (y). Therefore, in the conventional structure in which the boundary (k) between the tread rubber (g), wing rubber (h) and sidewall rubber (i) is located in such a region (y), separation failures are especially liable to occur along the boundary (k). Thus, the durability is greatly decreased.
It is therefore, an object of the present invention to provide a low-aspect tire in which the tire durability is improved by effectively preventing damage such as separations, cracks and the like occurred from boundaries between different rubber layers and edges of various layers.
According to one aspect of the present invention, a pneumatic tire having an aspect ratio of not more than 55% comprises
an axially protruding rib provided on each side of the tire to overhang a flange of a wheel rim,
a carcass extending between bead portions through a tread portion and sidewall portions,
a belt disposed radially outside the carcass,
a tread rubber disposed radially outside the belt to define the ground contacting surface of the tire,
a sidewall rubber disposed on each side of the tire and extending from the tread portion to the rib along the axially outside of the carcass,
a clinch rubber disposed on each side of the tire and extending from the bead portion to the rib along the outer surface of the tire, and
a wing rubber disposed axially outside the sidewall rubber and extending from the tread rubber to the rib along the outer surface of the tire, the wing rubber being softer than the tread rubber.
Therefore, due to the rib, the rib and part adjacent thereto are increased in the rigidity and the deformation thereof during running becomes decreased. The radially inner ends of the sidewall rubber and wing rubber and the radially outer end of the clinch rubber are positioned near or in the rib. Thus, the stress on the rubber ends can be minimized and separation failures and the like are effectively prevented.


REFERENCES:
patent: 2874746 (1959-02-01), Nichols
patent: 3982579 (1976-09-01), Mirtain
patent: 5746860 (1998-05-01), Moriyama
patent: 1-111502 (1989-04-01), None

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