Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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PNEU~ATIC TIRE
BACKGROUND OF THE INVENTION_
This invention relates to pneumatic tires
and particularly to radial type pneumatic tires~
Radial type pneumatic tires typically
include a crown area with an annular belt, a pair of
sidewall areas~ a pair of bead portions, and a
carcass or body which includes one or more carcass
plies of rubberized cords oriented substantially at a
90 angle (radially) to the circumferential center
plane of the tire. The cords of these carcass plies
can be made of such material as metal, glass, natural
textile or synthetic textile such as rayon, nylon,
polyester, aromatic polyamide or other similar
materials.
The carcass of a radial tire provides
structural stability to the tire, reduces
susceptibility of the tire to bruising, and reduces
the possibility of separation of tire components
occurring within the tire. In the crown area of the
tire, an annular belt also aids in reducing
susceptibility of the tire to bruising.
The number of carcass plies incorporated
into a radial tire carcass is usually dependent on
the intended service or use of the tire. Radial
tires having at least two continuous carcass plies
include such tires serving as large passenger tires
and light truck radial tires. In such tires, the
plies generally extend continuously from one bead
portion of the tire adjacent to the shoulder and
crown areas to the other bead portion and in most
tires each ply is wrapped around a wire bead in each
bead portion.
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It has been found in a radial tire carcass
with two continuous inner (first) and outer (second)
plies that the second ply provides limited structural
stability in the crown ar~ea of the tire and the bead
portions of the tire. The second ply also provides
limited resistance to bruising in the crown area of
the tire because the belt provides much of the
resistance to bruising.
Tire manufacturers are continuously
searchin~ for ways to reduce the overall weight of
radial tires and the costs to manufacture them.
Relatively unsuccessful attempts have been made to
design a single ply radial tire for service which
traditionally requires two or more carcass plies.
Other attempts have focused on reducing the amount of
carcass material in one of the plies of a multi ply
tire, as illustrated in tires containing
discontinuous radial outer or second plies as
described, for example, in U.S. Patents 3,058,509;
3,481,386; 3,509,93~; 4,096,899; and 4,185~675. In
'509, a tire is disclosed having an outer carcass ply
which is discontinuous or interrupted in the crown
area of the tire. The outer plies disclosed in '386;
'930 and '899 are also discontinuous in the crown
area of tires as well as at locations adjacent to the
bead wire. Often the cords and/or rubber in such a
discontinuous outer ply are of special materials
other than the materials that make up the continuous
radial inner or first ply. In '675, for example, a
second discontinuous ply is di~ferent from the first
ply in that the rubber of the second ply has a shore
A hardness after vulcanization of ~0 to 50.
Advantages of incorporating a discontinuous ply are
often negated when the materials in the second
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discontinuous ply are different from the ma~erials in
the first continuous ply.
Also, it has been found that significant
forces can act between the rim of the wheel upon
which the tire is mounted and the lower sidewall
portions of the tire. In the sidewall portion,
significant forces act on the tire in the region
where the wheel rim flange physically contacts the
sidewall of the tire. In this rim flange contact
region, the sidewall flexes over the rim flange. The
rim flange contact reyion of the tire must be made
strong enough to endure such flexing and forces
resulting therefrom.
Furthermore~ it has been found that a
predetermined thickness in each bead portion between
the radial inner part of the bead wire and the
surface of the bead portion must be maintained to
allow for suitable mounting of the tire on the rim.
Thus, when designing tires with
discontinuous carcass plies, unsatisfactory tires can
result by ignoring particular areas of the tire where
special forces occur and specific requirements in the
bead area are desired.
SUMMARY OF THE_INVENTION
It is an object of the invention to provide
an improved pneumatic radial type tir~.
Another object of this invention is to
provide a radial tire which performs comparably to a
typical radial tire with two or more continuous
carcass plies but which is characterized by reduced
manufacturing costs and weight when compared with
such a typical tire.
These and other objects, which will become
evident Erom the following description, are attained
in accordance with this invention by having a radial
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type pneumatic tire which includes a circumferen~
-tial center plane, a pair of bead portions con-
taining bead wire, a crown area or portion which
includes a belt assembly, a pair of sidewall areas
and a carcass comprising: a radial inner ply
which contains rubberized cords oriented radially
to the circumferential center plane of a tire/
which radial inner ply extends continuously from
one beacl portion to the other bead portion; and
a radial outer ply, which has two sections, such
that such radial outer ply is discontinuous in
the crown area of the tire and the bead portion
of the tire. Each section of the radial outer
ply extends from outward of the bead portion to
axial inward of the edges of the belt assembly.
In a particular embodimen-t the radial inner
ply is anchored in such bead portion by being
wrapped around the bead wire.
sRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a cross-sectional view of a radial
tire containing one embodiment of this invention.
Fig. 2 is a fragmentary view of a crown area
of the tire of Fig. 1.
DETAILED DESCRIPTION
This invention can be described in further
detail in terms of the presentl~ preferred embodi-
ments and with reference to the two figures of
the drawings wherein like reference characters
refer to like fea-tures or components.
The invention is described embodied as a
large passenger radial tire. Although this inven-
tion is very well suited to passenger tires, it
is also adaptable to other types and sizes of
tires such as light truck, radial tires and other
larger multiple ply radial tires.
In Figs. 1 and 2 a shaped and vulcanized
radial pneumatic tire 6 is shown mounted on a rim 7
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of a wheel 8. The tire 6 includes a crown area or
portion 9, a pair of sidewall areas 10 ana a pair of
bead portions 11 shaped for engagement with the rim 7
on which the tire 6 is to be mounted. Include~ in
S each bead portion 11 is a wire bead 22.
The crown portion 9 generally includes a
layer of tread rubber 28 which has a suitable pattern
29 of alternate grooves and ribs to provide traction
and resistance to skid. Ra~ally inward of the layer
of tread rubber 28 is a belt assembly 12. The belt
assembly 12 contains two belts 13 and 14 composed of
rubberized cords of low extensible materials such as
nylon, rayon, fiberglass, steel or aromatic
polyamide. The cords in the belts 13 and 14 are
disposed at an acute angle at between about 10 to
about 30 relative to the circumferential center
plane P of the tire 6. It is preferred that such
cords are oriented at equal but opposite angles in
adjacent belts 13 and 14.
Each of the pair of sidewall areas 10 are
generally composed of a suitable thickness of
sidewall rubber 26 which extends from the margins of
the tread rubber 28 to each bead portion 11. Each
sidewall area 10 presents a region 60 adjacent to t~e
rim 7 where flexing of the sidewall area 10 against
the rim 7 occurs. Such regions 60 in the sidewall
area are referred to as a rim flange contact region.
The tire 6 has a carcass 15 having two plies
of rubberized cords, a radial inner or first ply 17
and a radial outer or second ply 18. The second ply
18 has two sections 18a and 18b. The cords in the
two carcass plies 17 and 18 may be of suitable
material used as carcass reinforcing coras and are
oriented such that the individual rubberized cords
lie radially (i.e~ at substantially a 90 angle~
relative to the circumferential center plane P of
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the tire. Preferably the first ana second ply are
made of the same cord and rubber materialO The edges
27 of the first ply 17 arè wrapped around the wire
beads 22 in bead portions 11.
In Figs. 1 and 2, each of the two sections
18a and 18b of the second ply 18 extend from radia~y
inward of the belt 13 to a point between the rim
flange contact region 60 and the bead portion 11.
Each section 18a and 18b extends axially inwardly to
overlap each belt edge 63 by preferably at least
about 12 percent of the width of the belt 13 to
reduce possible occurrence of separations. In Figs~
1 and 2, the width of belt 13 is about 6 inches
(21.24 cm) whereby each section 18a and 18b extend
axially inwardly of each belt edge 63 by at least
about three-fourths of one inch (1.86 cm).
To reduce possible separation of the first
ply 17 and the second ply 18 in the sidewall area 10
of tire adjacent the bead portion 11, the second ply
18 extends radial inwardly of edge 73 of the first
ply 17 by at least one~and one-half inches (3.72
cm). Also, to reduce possible occurrence of
separations of the second ply 18 from the sidewall 26
in the rim flange contact region 60, the second ply
18 preferably extends about three-eights of an inch
(0.93 cm) radially inward of the rim flange contact
region 60 but terminates radially outwardly of beads 22.
The tire 6 includes an inner liner 25 which
is composed of rubber material such as butyl rubber
which is suitable to resist diffusion of air from the
tire 6. As shown in Fig. 1, the inner liner 25
extends from one bead portion 11, through each
sidewall area 10 and the crown area 9 to the other
bead portion 11. In this embodiment; inner liner 25
serves to provide additional or "filler" material in
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each bead portion ll to allow for suitable mounting
of the tire 6 on the rim 7 of the wheel 8. The
thickness oE the inner liner 25 is preferably about
the same as the thickness of the second ply 18 to
provide substantially the same material thickness
between the bead wire 22 and the rim 7 as found in
tires containing a second ply which is wrapped aroun~
the wire beads.
Each bead portion ll includes a "toe" 50 and
a finishing strip l9 which ~enerally comprlses
rubber-coated square woven fabric. As shown in Fig.
l, each finishing strip l9 extends from axial outward
of the second ply 18 and the inner liner 25, to a
position about 3/8 inch (0.92 cm) radial outwar~ of
the toe 50. The finishing strip l9 generally extends
radial outward of the edge of the second ply 18 by
ahout 3/4 inch (1.86 cm). In this embodiment,
finishing strip 19 serves to resist chafing between
the bead portion 11 and the rim 7.
It is understood that certain departures
from and modifications to the preferred embodiment
described are possible within the scope of the
invention which is to be measured by the following
claims.
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