Resilient tires and wheels – Tires – resilient – Pneumatic tire or inner tube
Reexamination Certificate
2000-02-23
2003-11-25
Morano, S. Joseph (Department: 3617)
Resilient tires and wheels
Tires, resilient
Pneumatic tire or inner tube
Reexamination Certificate
active
06651716
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The invention relates to correcting uniformity characteristics of a cured pneumatic tire.
BACKGROUND OF THE INVENTION
Pneumatic TIRES
FIGS. 1A and 1B
illustrate an exemplary pneumatic tire
100
of the prior art. The tire
100
includes a pair of annular, substantially inextensible beads
102
and
104
, each of which is disposed within a respective bead portion
106
and
108
of the tire
100
, a generally cylindrical tread portion
110
, a relatively inextensible belt structure (“belts”)
112
disposed within the tread portion
110
, and sidewall portions
114
and
116
extending between opposite sides
110
a
and
110
b
of the tread portion
110
and respective ones of the bead portions
106
and
108
. The tire
100
has a section height SH measured from an edge of the bead portion
106
(or a nominal rim diameter) to an outer diameter of the tread portion
110
. The tire
100
has an inner surface
118
and an outer surface
119
. An inner liner (not shown) is typically disposed on the inner surface
118
of the tire
100
.
At least one carcass reinforcing member
120
(also referred to as a “ply”) extends between the two beads
102
and
104
, within the carcass of the tire
100
. The ply
120
has a central (middle) portion
120
a
which is disposed between the two beads
102
and
104
, and has two opposite end portions (“turn-up” ends)
120
b
and
120
c
, each of which wrap around a respective one of the beads
102
and
104
and extend radially back toward the tread portion
110
of the tire
100
. The tire
100
further typically includes bead filler apexes
122
and
124
disposed atop respective ones of the beads
102
and
104
and extending radially outwardly therefrom.
The tire
100
has an axis of rotation (not shown), an outer diameter which is twice (2×) a radius dimension between the axis of rotation and the tread surface, and an inner diameter which is (2×) the radius dimension between the axis of rotation and an inner edge of the bead portion. An equatorial plane “EP” for the tire
100
, is defined as a plane which is perpendicular to the tire's axis of rotation and passing through the center of the tread portion
110
, or midway between the tire's beads
102
and
104
. A radial direction (orientation) is indicated by the arrow
130
, and a lateral (or axial) direction (orientation) is indicated by arrows
132
.
The at least one ply
120
of the tire is at least one layer of rubber-coated ply cords. Ply cords are typically formed of cotton, rayon, nylon, polyester or other man-made synthetic or textile cord which are capable of exhibiting permanent changes in physical properties upon application of load or heat, or of fiber glass, metal wire or the like, the physical properties of which are relatively non-changeable upon application of load or heat. Commonly-owned U.S. Pat. No. 4,654,253 (Brown, et al.; 1987) and U.S. Pat. No. 4,763,468 (Brown, et al.; 1988) disclose high strength greige woven fabrics particularly suitable for use as a tire reinforcement component, wherein a cord may comprise at least two optimally drawn polymeric yarns.
Generally, there are three basic types of pneumatic tires—“bias”, “bias/belted” and “radial”—each type essentially being defined by the orientation of the cords within the at least one ply (
120
).
In the bias (or “cross-ply”) tire, the cords of the reinforcing ply extend diagonally across the tire from bead-to-bead, typically at an angle of between 25 and 40 degrees with respect to a centerline of the tire. The cords run in opposite directions in each successive reinforcing ply layer, resulting in a crisscross pattern of cords.
In the bias/belted tire, as in the bias tire, the cords extend diagonally across the tire, from bead-to-bead, typically at an angle of between 25 and 45 degrees with respect to the centerline of the tire, and the cords run in opposite directions in each successive ply. A cord-reinforced “belt” structure is disposed in the tread portion of the tire, and the belt cords typically have an angle of between 20 and 35 degrees with respect to the equatorial plane of the tire.
In the radial tire, the plies of reinforcing cords are parallel and extend transversely from bead-to-bead. That is, the parallel cords are substantially perpendicular to the direction of tire travel.
A cord-reinforced belt structure is disposed in the tread portion of the tire, and is composed of several layers of cords disposed nearly parallel (10 to 30 degrees) to the circumference of the tire. The belt structure acts to restrict the reinforcing plies. Increased sidewall bulging is characteristic of radial tires.
TIRE MANUFACTURING PROCESS
As is disclosed in commonly-owned European Patent Application Publication No. 0 522 468 A1 (published 13.02.93), in a typical tire manufacturing process, an inner liner is disposed on a generally cylindrical tire building drum (or mandrel). At least one carcass reinforcing member (“ply”, compare
120
) is disposed over the inner liner. Next, bead rings (compare
102
,
104
) are disposed over the reinforcing ply, and apex rubber (compare
122
,
124
) is applied over the beads. Next, a turn-up bladder or the like, such as is disclosed in U.S. Pat. No. 5,407,521 (Falvard; 1995), is activated to turn-up the two opposite end portions (compare
120
b
,
120
c
) of the ply (and, optionally, the inner liner) around the bead rings. Next, sidewall rubber is added, and the resulting tire “carcass” is shaped into what is generally its ultimate toroidal form. Tread rubber and, optionally, belts or breakers and chafers, may then be added to the construction, and the resulting “green” tire can be inserted into a mold wherein it is heated for a period of time (e.g., approximately 10-30 minutes) at an elevated temperature (e.g., at least approximately 120 degrees Celsius, such as approximately 150 degrees Celsius) to “cure” or “vulcanize” the rubber components of the green tire. During the molding process, tread patterns are typically impressed into the tread rubber, and designs, lettering and the like may be formed in the sidewall rubber of the tire. In some cases, tires are retained in the mold until they have become substantially cooled down. More often, tires are removed from the mold without a cooling period, and are allowed to cool down (e.g., to ambient temperature) outside of the mold. Rubber is a poor conductor of heat and the thick tread portion of the tires continue to vulcanize for a period after removal from the molds.
UNIFORMITY CHARACTERISTICS
After a tire is assembled and at least partially cured, the tire is typically tested for one or more uniformity characteristics. “Uniformity” is defined herein as what a “perfect” or “ideal” tire would yield for a certain measured characteristic when tested during rotation. “Uniformity characteristic” is defined herein as a deviation in those certain characteristics from what the perfect tire would yield during testing.
As is evident, the pneumatic tire is a somewhat complicated construction of various materials which is difficult to manufacture with perfect consistency, from tire-to-tire inconsistencies in materials, in the placement of the materials on the building drum, and other process variables will contribute to both dimensional and dynamic variations, from tire-to-tire.
Generally, a dimensional non-uniformity is a deviation from perfect roundness of the outer circumference of the tire (alternatively, the outer circumference of the tire being round, but off-center with respect to the tire's axis of rotation), and a dynamic non-uniformity is a condition which manifests itself in the tire's ability to react forces at different orientations of the tire.
Sources of such tire non-uniformities may include one or more of the following:
a. The tread, sidewall and innerliner are stored on long rolls in the “green” state and are assembled into a tire in the green state. While in the green state, during storage and tire building, rubber can deform. Therefore, the green rubber tire component
Brown Robert Walter
Sandstrom Paul Harry
Cohn Howard M.
Nguyen Long Bao
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