Resilient tires and wheels – Tires – resilient – Anti-skid devices
Reexamination Certificate
1999-01-14
2001-04-24
Maki, Steven D. (Department: 1733)
Resilient tires and wheels
Tires, resilient
Anti-skid devices
C152S209220, C152S209250, C152S209270, C152SDIG003
Reexamination Certificate
active
06220321
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a pneumatic tire, more particularly to an tread portion of a heavy duty tire being capable of improving wear resistance and wet performance.
Recently, circumferentially extending wide main grooves in heavy duty tires for a truck, bus and the like have been increasingly used for wet performance. In North America, for example, there is a tendency to use tires having deep main grooves on drive wheels in order to prevent accidents due to slipping. In the case of deep main grooves, however, tread rubber on both sides of the deep main grooves is liable to move during running, and as a result, uneven wear is liable to occur. This is especially remarkable when the hardness of tread rubber is decreased for wet grip and the like. To put it more concretely, as shown in
FIG. 5
for example, in case the of a tread pattern in which a circumferential main groove (e) is disposed on each side of the tire equator C, and a plurality of blocks b
1
, b
2
are disposed on each side of the main groove (e), the following uneven wear occurs: so called “block edge wear” in which the blocks b
1
and b
2
wear partially on the axially outer edge more than the inner edge (indicated by right side upward hatching); and so called “step down wear” in which the full surface of the blocks b
2
located on the inside of the vehicle wears faster than others (indicated by left side upward hatching).
SUMMARY OF THE INVENTION
It is therefore, an object of the present invention to provide a heavy duty tire, in which uneven wear is effectively prevented without decreasing the depth of circumferential main grooves to maintain wet performance.
According to one aspect of the present invention, a heavy duty tire comprises a tread portion with tread edges, the tread portion provided with
a circumferentially extending wide main groove on each side of the tire equator C,
a circumferentially extending outer narrow groove on the axially outside of the main groove,
a circumferentially extending inner narrow groove on the axially inside of the main groove, and
lug grooves extending axially inwardly from the tread edges to the inner narrow grooves
so that the tread portion is divided into
a rib-like portion between the two inner narrow grooves,
first blocks between the inner narrow groove and the main groove,
second blocks between the main groove and the outer narrow groove, and
third blocks between the outer narrow groove and the adjacent tread edge,
the above-mentioned main groove spaced apart from the tire equator by an axial distance of from 15 to 25% of the tread width,
the main groove having a groove depth of from 10 to 12% of the tread width,
the inner and outer narrow grooves having a depth less than that of the main groove,
the above-mentioned rib-like portion provided with slits extending from one of the inner narrow grooves to the other, and
the slits having a depth of from 0.2 to 0.3 time the depth of the main groove.
Here, the tread width is the axial distance between the tread edges or the maximum ground contacting width between the axial outermost edges of the ground contacting region under such a condition that the tire is mounted on its standard rim and inflated to its standard pressure, and then loaded with a standard load. The standard rim is the “standard rim” specified in JATMA, the “Measuring Rim” in ETRTO, the “Design Rim” in TRA or the like. The standard pressure is the “maximum air pressure” in JATMA, the “Inflation Pressure” in ETRTO, the maximum pressure given in the “Tire Load Limits at Various Cold Inflation Pressures” table in TRA or the like. The standard load is the “maximum load capacity” in JATMA, the “Load Capacity” in ETRTO, the maximum value given in the above-mentioned table in TRA or the like.
The widths and depths of various grooves, slits and the like are measured under the standard unloaded condition in which the tire is mounted on the standard rim and inflated to the standard pressure, but loaded with no tire load.
REFERENCES:
patent: 2186180 (1940-01-01), Sloman et al.
patent: 2926715 (1960-03-01), Constantakis
patent: 5804000 (1998-09-01), Shirai et al.
patent: 5909756 (1999-06-01), Miyazaki
patent: 6003575 (1999-12-01), Koyama et al.
patent: 370747 (1990-05-01), None
patent: 586124 (1994-03-01), None
patent: 773117 (1997-05-01), None
patent: 59-209903 (1984-11-01), None
patent: 7-172112 (1995-07-01), None
Nakatsuji Hidekatsu
Takada Yoshiyuki
Yoshioka Shigeki
Birch Stewart Kolach & Birch LLP
Maki Steven D.
Sumitomo Rubber Industries Ltd.
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