Resilient tires and wheels – Tires – resilient – Pneumatic tire or inner tube
Reexamination Certificate
1997-07-11
2001-12-18
Johnstone, Adrienne C. (Department: 1733)
Resilient tires and wheels
Tires, resilient
Pneumatic tire or inner tube
C152S526000, C152S532000, C152S538000
Reexamination Certificate
active
06330896
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
The present invention relates to a radial-ply tire having a belt consisting of 4 or more plies and disposed on a carcass with interposed rubber pads, and more particularly to a radial-ply tire improved in camber thrust characteristic.
2. Background Art
FIG. 3
is a schematic partial section view showing a conventional radial-ply truck/bus tire which is generally used at an inflation pressure not less than 4 kg/cm
2
.
The circumferential surface of a carcass
10
is braced by a belt
20
. This belt
20
consists of four plies
21
,
22
,
23
and
24
. These belt plies may for example be rubber pads steel cords, with pad rubber
30
being interposed between the ends of these plies and the carcass
10
. Of the four plies, the second ply
22
has the maximum width NBW, with the third and fourth plies
23
,
24
having progressively diminishing widths. Furthermore, tread rubber
40
is laid on the belt
20
. The width of this tread rubber
40
, which means the tread width TW, is larger than the maximum belt width MBW.
In the conventional radial-ply tire described above, in which the widths of all the belt plies
21
,
22
,
23
,
24
are smaller than the tread width TW, the tread stiffness shows a sudden decrease at the side edges of the tread rubber
40
so that when the tire has been caught in a rut, a negative camber thrust is generated, provided that the camber in the upward direction along the slope of the rut is taken as being the positive camber. Therefore, the problem arises that unless the steering wheel is turned much, the vehicle cannot be successfully dislodged from the rut.
With the foregoing in view, it is an object of the present invention to achieve a positive camber thrust with a radial-ply tire having a belt of 4 or more plies on a carcass through an interposed rubber pads.
SUMMARY OF THE INVENTION
The radial-ply tire of the present invention has a belt consisting of 4 or more plies between a carcass and a tread, the respective ends of the plies being kept isolated from the carcass by respective rubber pads interposed therebetween, the width TBW of the outermost belt ply being larger than the width NBW of the adjacent ply and the value of K given by the following equation being not less than 0.1 and not more than 0.4.
K
=
MBW
-
TW
OW
-
TW
where MBW is the maximum belt ply width, OW is the maximum tire width and TW is the tread width.
In this radial-ply tire, the tread portions disposed externally of the conventional belt region, that is to say, the side edges of the tread, have an increased stiffness to generate a positive camber thrust. Therefore, with this radial-ply tire, a vehicle can be easily dislodged from the rut with a large slope without turning the steering wheel through a large angle. If the value of K is less than 0.1, inclusive of the negative range, the value of camber thrust will be negative. If the value of K exceeds 0.4, difficulties will be encountered in the manufacture of the tire.
Furthermore, as the outermost belt ply width TBW is increased over the tread width TW, the ends of this outermost belt ply are disposed closer to side walls of tire shoulders so that not only strain of the belt ends due to loading is decreased but also the irregular wear of the tread ends is suppressed to thereby contribute to an increased tire durability.
Furthermore, as the side wall of the tire shoulder is elevated at an imaginary extension of the belt, the ends of all the belt plies adjoin a comparatively thick body of rubber so that the concentration of stresses at the ply ends is relieved by deformation of the rubber.
REFERENCES:
patent: Re. 30549 (1981-03-01), Mirtain et al.
patent: 3205931 (1965-09-01), Keefe, Jr.
patent: 3244213 (1966-04-01), McMannis
patent: 3982579 (1976-09-01), Mirtain
patent: 3990493 (1976-11-01), Caretta
patent: 4262726 (1981-04-01), Welter
patent: 4282918 (1981-08-01), Tomoda et al.
patent: 4446905 (1984-05-01), Tamura et al.
patent: 4633926 (1987-01-01), Tamura
patent: 4702293 (1987-10-01), Iwata et al.
patent: 4716951 (1988-01-01), Suzuki et al.
patent: 0072500 (1983-02-01), None
patent: 0973944 (1964-11-01), None
patent: 2096073 (1982-10-01), None
patent: 58126204 (1983-07-01), None
Nakasai Takashi
Ohashi Junichi
Johnstone Adrienne C.
Jordan and Hamburg LLP
Toyo Tire & Rubber Co., Ltd.
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