Resilient tires and wheels – Tires – resilient – Pneumatic tire or inner tube
Reexamination Certificate
1999-08-24
2001-08-21
Johnstone, Adrienne C. (Department: 1733)
Resilient tires and wheels
Tires, resilient
Pneumatic tire or inner tube
C152S544000
Reexamination Certificate
active
06276417
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a pneumatic tire and more particularly to a heavy duty pneumatic radial tire for use in, for example, construction vehicles comprising a pair of bead portions each including a bead core embedded therein, a radial carcass of a rubberized cord ply extending between the pair of the bead portions and wound around each bead core from the inside of the tire toward the outside thereof, a belt superimposed about a crown portion of the carcass and comprised of at least one belt layer, and a tread disposed on an outside of the belt in the radial direction.
2. Description of Related Art
In the conventional heavy duty pneumatic radial tire, the bead core is at a horizontal state in an axial direction of the tire or a tapering angle &thgr;
C
of an inner side of the bead core in the radial direction is zero. A bead base of the bead portion is tapered so that an inner diameter of a bead base face is gradually decreased from a bead heel part toward a bead toe part. In this case, a tapering angle &thgr;
B
of the bead base in the tire is somewhat larger than a tapering angle &thgr;
R
of a bead seat in a rim and is set to a degree of (&thgr;
R
+&agr;), whereby a tightening margin is held between the tire and the rim.
In such a conventional tire, when a large torque is applied to the tire, slippage is caused between the bead base portion of the tire and the bead seat of the rim and hence there is a tendency that rubber beneath the bead core, particularly rubber in a bead heel part is worn to easily cause a trouble of air leakage.
This is due to the fact that since the inner side of the bead core in the radial direction is parallel or substantially parallel to the axial direction of the tire and the bead base of the bead portion is tapered, the pressure to the bead heel part becomes high and the pressure to the bead toe part becomes small and hence rubber is worn at the side of the bead heel part subjected to a high pressure.
SUMMARY OF THE INVENTION
It is, therefore, an object of the invention to solve the aforementioned problem of the conventional technique and to provide a heavy duty pneumatic radial tire hardly causing the rim slippage.
According to the invention, there is the provision of a heavy duty pneumatic radial tire comprising a pair of bead portions each including a bead core embedded therein, a radial carcass of a rubberized cord ply extending between the pair of the bead portions and wound around each bead core from the inside of the tire toward the outside thereof, a belt superimposed about a crown portion of the carcass and comprised of at least one belt layer, and a tread disposed on an outside of the belt in the radial direction, in which (1) a tapering angle &thgr;
C
of an inner side of the bead core in the radial direction is within ±2° of a tapering angle &thgr;
R
of a bead seat part in an approved rim, and (2) as a tightening margin between the inner side of the bead core in the radial direction and the bead seat part of the approved rim when the tire is mounted onto the approved rim and inflated under a standard internal pressure, a compression ratio Ca at a widthwise inner end of the inner side of the bead core is within a range of 102-115% of a compression ratio Cb at a widthwise outer end thereof when a value obtained by dividing a thickness from the inner side of the bead core in the radial direction to a bottom face of the bead seat part excluding a thickness of a metal cord member by a thickness prior to the mounting onto the approved rim is a compression ratio C.
In preferable embodiments of the invention, a tapering angle &thgr;
B
of a bead base in the bead portion is made larger by 0.5-3° than the tapering angle &thgr;
C
of the inner side of the bead core in the radial direction, and a compression ratio Cc at a widthwise center c of the inner side of the bead core in the radial direction is within ±10% of an average value (Ca+Cb)/2 of the compression ratio Ca at the widthwise inner end of the inner side of the bead core and the compression ratio Cb at the widthwise outer end thereof.
REFERENCES:
patent: 4998575 (1991-03-01), Kanamaru
patent: 5464051 (1995-11-01), Beard et al.
patent: 5772811 (1998-06-01), Ueyoko et al.
patent: 39 36 231 A1 (1990-05-01), None
patent: 0 129 675 A1 (1985-01-01), None
patent: 0 652 120 A1 (1995-05-01), None
patent: 0 749 855 A1 (1996-12-01), None
patent: 9-39519 A (1997-02-01), None
Ando Shuji
Honbo Yoichi
Bridgestone Corporation
Johnstone Adrienne C.
Sughrue Mion Zinn Macpeak & Seas, PLLC
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