Note: Descriptions are shown in the official language in which they were submitted.
CA 02428290 2003-05-27
A Radial Ply Pneumatic Tire
Background of the Invention
This invention relates to a tire; more
particularly ~to a pneumatic tire capable of beingwsed
in the uninflated condition.
Various tire constructions have been suggested
for pneumatic nan-flat tires, that is, tires capable
of being used irt the uninflated condition: One
approach taken has been to simply strengthen the
sidewalls by increasing the cross-sectional thickness
thereof. Due to the large amounts of. rubber required
to stiffen the sidewall members, heat build-up is a
major factor in tire failure. This is especially true
when the tire is operated for prolonged periods at
high speeds in the uninflated cond.itioai.
An equally important design consideration in the
development of a. run-flat tire is insuring that the
uninflated tire remains seated on the rim. Solutions
have been developed employing bead restraining devices
as well as special rims to accomplish this
requirement.
Applicants have discovered a new invention which
permits a tire construction to be built which can be
operated in the uninflated condition for extended
distances at relatively high speeds after which the
tire can be repaired and returned to normal use, while
at the same time maintaining the desired performance
of the tire in the inflated state.
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Summary of the Invention
A radial pl,~ pneumatic tire is described: The
tire has an axis of rotation, a tread having a pair of
lateral edges, a pair of reinforcing belts located
radially inward of the tread, a pair of sidewalls
extending radially inwardly from each lateral edge, a
maximum section width defined as the maximum axial
distance as measured from the outer surfaces of the
sidewalls, and a tire carcass structure.
The tire carcass structure comprises a pair of
bead portions,, a carcass reinforcing structure and two
bead fillers. TI~e bead portion extends radially
inwardly from each sidewall. Each bead portion
includes a substantially inextensible bead core having
a flat base surf'~ce. The flat baser surface has a pair
of edges and a width "4~" between the edges . The bead
core further has an axially inner first surface and an
axially outer second surface extending radially
outwardly from an edge of the flat base surface: Each
first and second surface is tangent to the bead core.
The first surface and the flat bases surface form an
acute included angle a. The second surface and the
flat base surface form an acute incrluded angle ~. The
angle cx is greater than or equal to the angle Vii.
The carcass reinforcing structure is radially
inward of the, reinforcing belts and extends
circumferentially about the tire from one bead portion
to the other bead portion, the care~ass reinforcing
structure has,a :first ply and a seerond ply. Each ply
has a pair of turnup ends, one turnup end of each ply
is wrapped about each. bead core anei extends axially
and radially outwardly. The turnup end of the first
ply terminates in proximity to the radial location of
the maximum section width of the tire.
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Each bead filler is adjacent to and extends radially
outward from a bead core.
One embodiment of the invention includes an aramid
overlay disposed :radially outward of the belt reinforcing
structure.
Another embodiment of the invention includes a pair of
first fillers located between an innerliner and the first
ply. One first filler extends from each bead portion
radially to beneath the reinforcing belt.
Another embodiment includes, in addition to the first
filler described above, a second filler. The second filler_
is disposed between the first and the second ply. The.
second filler extends from each bead portion radially
outward to beneath the reinforcing belt.
Another embodiment includes a cord reinforcement
member located between the bead filler anct the second ply
turnup. The cord reinforcement member has a first and.
second end. The first end is axially and radially inward of
the second end. The cord reinforcing member increases in
radial distance from the axis of rotation of the tire as a
function of distance from its first e:nd.
Another embodiment includes a pair of fabric
reinforcing members, one member integral of each of the bead
portions. The fabric reinfarcing member has a first and
second end, the reinforcing member is wrapped about the
first end second plies and the bead core. Both the first
and second ends extend radially above the bead core.
In accordance with another aspect of the present
invention, there is provided a radial ply pneumatic tire
having an axis of rotation, a tread having a pair of lateral
edges, a pair of reinforcing belts located radially inward of
the tread, a pair of sidewalls, one sidewall extending
radially inwardly from each lateral edge, a maximum section
width, and a tire carcass structure, the tire carcass
structure comprising:
CA 02428290 2004-04-16
3a
a) a pair of bead portions, one bead portion
extending axially inwardly from each sidewall, each
portion including a substantially inextensible core;
b) a carcass reinforcing structure radially inward
of the reinforcing belts extending circumferentially
about the tire from one bead portion to the other bead
portion, the carcass reinforcing structure having a first
ply and a second ply, each ply having a pair of turnup
ends, one turnup end of each ply being wrapped about each
l0 bead core and extending axially and radially outwardly,
the turnup end of at least one ply terminating radially
in proximity to the radial location of the maximum
section width of the tire;
c) an innerliner radially inward of the first ply;
d) an aramid overlay being radially outward of the
reinforcing belt; and
e) a pair of first fillers and a pair of bead
fillers, the first fillers being located between the
innerliner and the first ply, one first filler extending
2o from each bead portion radially to beneath the
reinforcing belt, one of the bead fillers being located
above each bead core and between the second ply and the
turnup ends of the first and second plies.
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Description of the Drawings
Figure 1 is a cross-sectional view of a tire made
in accordance with the present invention
Figure 2 is a plan view of a footprint of. the
tread portion of the tire of Figures l;
Figure 3 is an enlarged fragmentary view of the
shoulder portion of the tire of Figure 1~ and
Figure 4 is an enlarged fragmentary view of the
bead portion of the tire of Figure 1.
Definitions
"Aspect Rat:LO'° means the ratio of a tire~ s
section height to its section width.
"Axial" and "axially" means the lines or
directions that are parallel to the axis of rotation
of the tire.
"Bead" means that part of the tire comprising an
annular tensile member wrapped by ply cords and
shaped, with or without other reinforcement elements
such as flippers, chippers, apexes, toe guards and
chafers, to fit ~:he design rim.
"Belt Struct:ure°' or '°Reinforci.ng Belts" means at
least two annular. layers or plies of parallel cords,
woven or unwoven, underlying the tread, unanchored to
the bead, and having both left and right cord angles
in the range from 17° to 27° with respect to the
equatorial plane of the tire.
°'Circumfereratial" means lines or directions
extending along the perimeter of the surface of the
annular tread perpendicular to the axia:L direction.
"Carcass°' means the tire structure apart from the
belt structure, tread, undertread, and sidewall rubber
over the plies, but including the beads..
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°'Chafers'° refers to narrow strips of material
placed around the outside of the bead to protect cord
plies from the rim, distribute flexing above the rim,
and to seal the tire.
5 '°Cord" means one of the reinforcement strands of
which the plies in the tire are comprised.
"Equatorial Plane (EP)" means the plane
perpendicular to the tire's axis of rotation and
passing through the center of its tread.
"Footprint" means the contact patch or area of
contact of the tire tread with a flat surface at zero
speed and under normal load and pressure.
"Innerliner" means the layer or layers of
elastomer or other material that form the inside
surface of a tubeless tire and that contain the
inflating fluid within the tire.
"Normal Inflation Pressure°° means the specific
design inflation pressure and load assigned by the
appropriate standards orgar~ization for the service
condition for the tire.
"Normal Load" means the specific load assigned by
the appropriate standards organization for the service "
condition for the tire.
'°Ply" means a continuous layer of -rubber-coated
parallel cords.
°'Radial" and "radially" mean directions radially
toward or away from the axis of rotation of theltixe.
"Radial.Ply Tire°' means a belted or
circumferentially-restricted pneumatic tire in which
the ply cords which extend from bead to bead are laid
at cord angles between 65° and 90° with. respect to the
equatorial plane of the tire.
"Section Height" means the radial distance from
the nominal rim diameter to the outer diameter of the
tire at its equatorial plane.
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"Section Width" means the maximum linear distance
parallel to the axis of the tire and between the
exterior of its >~idewalls when and after it has been
inflated at normal pressure for 24 hours, but
unloaded, excluding elevations of the sidewalls due to
labeling, decoration or protective bands.
"Shoulder°' means the upper portion of sidewall
just below the tread edge.
'°Sidewall°' means that portion of a tire between
the tread and the bead.
"Tread Width" means the arc length of the tread
surface in the axial direction, that is, in a plans
parallel to the axis of rotation of the tire.
Detailed Description of the Preferred Embodiment
Referring to Figs. 1 and 2, there :Ls illustrated
a tire 10 made irl accordance with the present
invention. In the particular embodiment illustrated,
the tire 10 is a passenger tire; th.e tire 10 is
provided with'a ground-engaging triad portion 12 which
terminates in the shoulder portions 14,:16 at the
lateral edges of the tread respectively. Sidewall
portion 18,20 extends from shoulder portion 14,16
respectively and terminates in a pair of bead portions
22,22' each having an annular inextensible bead core
26,26' respectively. The tire 10 is further provided
with a carcass reinforcing structure 30 which extends
from bead portion 22 through sidewall portion 1~,
tread portion 12, sidewall portion 20 to bead portion
22'. The turnup ends 32,34,32',34' of carcass
reinforcing structure 30 are wrapped about bead cores
26,26' respectively. The tire 10 may include a
conventional~.inner liner 35 forming the inner
peripheral surface of the tire 10 it the tire is to be
CA 02428290 2003-05-27
of the tubeless type. Placed circumferentially about
the radially outer surface of carcass reinforcing
structure 30 beneath tread portion 12 is a tread
reinforcing belt structure 36. In the particular
embodiment illustrated, belt structure 36 comprises
two cut belt plies 50,51 and the cords of belt plies
50,51 are oriented at an angle of about 23 degrees
with respect to the mid-circumferential centerplane of
the tire. The cords of belt ply 50 are disposed in an
opposite direction to the mid-circiamferential
centerplane and from that of the cords of belt ply 51.
However, the bel~r structure 36 may comprise any number,
of belt plies of any desired configuration and the
cords may be disposed at any desired angle. Belt
structure 36 has a lateral stiffness across the belt
width so as to minizni~e lifting of the tread from the
road surface during operation of the tire in the
uninflated state. In the embodiment illustrated, this
is accomplished by making the cord.e of belt plies
51,52 of steel and preferably of a steel cable
construction.
The carcass reinforcing structure comprises at
least two reinforcing ply structures. In the
particular embodiment illustrated, there is provided a
radially inner first reinforcing ply structure 38 and
a radially outer second reinforcing ply structure ~0,
each ply structure 38,40 comprising one layer of
parallel cords. The cords 41 of reinforcing ply
structure 38,40 are oriented at an angle of at least
75 degrees with respect to the mid-circumferential
centerplane CP of the tire 10. In the particular
embodiment illustrated, the cords 43. are oriented at
an angle of about 90 degrees with r~especa to the mid-
circumferential centerplane CP. The cords 41 may be
made of any ~iater,ial normally used for cord
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reinforcement of rubber articles, for example, and not
by way of limitation, rayon, nylon and polyester.
Preferably, the cords are made of material having a:
high adhesion property with rubber and haglh heat
resistance. In the particular embodiment illustrated,
the cords 41 are made from rayon. The first and
second reinforcing ply structure 38,40 each preferably
comprise a single ply layer, however, any number of
carcass plies may be used.
As further illustrated in Fig. 1, the first and
second reinforcing ply structure 38,40 raave turnup
ends 32,34 and 32',34' respectively which wrap about
the bead core 26 and 26' respectively. The turnup
ends 34,34' of the second ply 40 are adjacent to the
bead core 26,26' and terminates radially above the
bead core 26,26'. The turnup ends 32,32° of the first
ply 38 wrap about the second ply turnup ends 34,34'
and the bead core 26,26'. The turnup ends 34,34' of
the first ply terminates radially a distance E above
the nominal rim diameter of the tire in proximity to
the radial location of the maximum section width of
the tire. In the preferred embodiment, the turnup
ends 34,34' are located within 20% of the section
height of the tire from the radial locat3.on of the
maximum section width, most preferably terminating at
the radial location of the maximum section width.
Alternatively, turnup ends 32,32' can te~ninatelas:
described above in proximity of the -radial location of
the maximum section width. In such a case the turnup
end 34,34' of the first ply 38 can be radially above
or below the second ply turnup end 32,32'.
1~s further illustrated in Fig. 4, the bead
portions 22,22' of the tire 10 each have an annular
substantially inextensible bead care 26;26'
respectively. The bead core 26,26' h.as a flat base
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surface 27,27' defined by an imaginary surface tangent. to
the radially innermost surfaces of th.e bead wires. Th.e flat
base surface 27,21' has a pair of edges 28,29 and a width
"W" between the edges. The bead core has an axially inner
first surface 23 extending radially from edge 28 and an
axially outer second surface 25 extending radially from edge
29. The first surface 23 and the flat base surface 2'7,27'
form an acute included angle a. The second surface 25 and
the flat base surface 27,27' form an .acute included angle (3.
l0 The angle a is greater than or equal 'to the angle [3. In the
preferred embodiment, cz approximately equals (3.
The bead core 26,26° may further include a radially
outer surface 31 extending between the first and.second
surfaces 23,25 respectively. The radial outer surface 31 has
a maximum height H. The height H is less than the width of
the base '°W." The cross-section defined by surfaces
23,25,27, and 31 preferably are in the form of the base
portion of an isosceles triangle. The upper portion of the
triangular shape cross-section is generally not required
because the strength of the core 26,2E~' as illustrated is
sufficient to restrain the beads of arl uninflated tire on
the rim.
The bead core is preferably constructed of a single or
monofilament steel wire continuously wrapped. The bead
construction is as described in co-owned United States
Patent No. 5,263,526, issued November 23, 1993.
The flat base surfaces of the bead cores 26,26' are
preferably about parallel relative to the axis of rotation,
while the bottom of the molded portion of the bead is
inclined; the preferred inclination being approximately 5°
to 10.5° relative to the axis of
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rotation. The inclination of the bead portion assists
sealing the tire and is complimentary to the
inclination of the bead seat flange of a conventional
rim and is believed to assist retaining the beads
seated to the r~.m.
Located within the bead portions 22,22'and the
radially inner portions of the sidewall portions 16,18
are high modulus elastomeric fillers 48 disposed
between carcass reinforcing structure 30 and the
turnup ends 32,34 and 32',34° ~eespectively. The
elastomeric fillers 48 extend from the radially outer
portion of bead cores 26,26° respectively, up into the
sidewall portion, gradually decreasing in cross
sectional width. The elastomeric inserts 48 terminate
a distance G from the nominal rim diameter NRD of at
least 25 percent (25%) of the section height SH of the
tire. In the particular embodiment il7.ustrated, the
elastomeric fillers 48 each extend rad;.ally outward
from the nominal rim diameter NRD a distance of
approximately forty percent (40%) of the maximum
section height SH. For the purposes of: this
invention, the maximum section height SH of the tire
shall be considered the radial distance measured from
the nominal rim diameter NRD of the tire to the
radially outermost part of the tread portion of the
tire. Also, for the purposes of this invention, the
nominal rim diameter shall be the diameter of the tire
as designated by its size.
In a preferred embodiment of the invention the
bead portions 22,22' further includes at least one
cord reinforced member 52,53 locatEed between the. bead
filler 48 and the second ply turnup end 32. The cord
reinforced member or members 52,53 have a first end 54
and a second end 55. The first end 54 is axially and
radially inward of the second end 55. The cord
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reinforced member or members 52,53 increase in radial
distance from the axis of rotation, of the tire 10 as a
function of distance from its first end 54. In the
illustrated figure 4, the cord reinforced member
comprises two components 52,53 having a width of about
4 cm. The axially outer component 52 has a radially
inner end 54 that is radially above with the outer
edge 29 of the bead core 26,26'. The axially inner
component 53 has a radially inner end that is radially
outward of the outer edge 29 of the bead core 26,26°
by about 1 cm. The axially inner and axially outer
components 52,53, preferably have steel. cord
reinforcement. The second end 55 of the cord
reinforced member is located radia.lly outward of the
second ply turnup end 32 and radially inward of the
termination of the turnup end 34 o:f the first ply 38.
The cords of members 52;53 are preferably
inclined forming an included angle relative to the
radial direction in a range from 2!5° to 75°,
preferably 30°. If two members are employed, the lord
angles are preferably equal but oppositely disposed.
The cord reinforcement member 52,53 dramatically
improves the handling characteristics of a car having
an uninflated tire of the present invention. The
members 52,53 greatly reduce the tendency for the car
to oversteer, a significant problem encountered in
conventional tires that are driven while uninflated or
underinflated.
A fabric re~_nforced member 61 may ~e added to the
bead portion of the tire 10. The fabric reinforced
member has first and second ends 62,63. The member is
wrapped about. the first and the second plies 38,40 and
the bead core 26,26'. Both the fir~;t and the second
ends 62,63 extend radially above and outward of the
bead core 26,26'.
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The sidewall portions 18,20 may be provided with
elastomeric fillers 42. The first i=fillers 42 may be
employed between the innerliner and the first
reinforcement ply 38. The first fillers 42 extend from
each bead portion 22,22' radially iro beneath the
reinforcing belt structure 36. Alternatively, as
illustrated in t:he preferred embodiment of the
invention as shown in figures 1,3,<~nd 4, the sidewall
portions 18,20 may each include a first filler 42 and
a second filler 46. The first fillers 42 are
positioned as described above. The second fillers 46
are located between the first and 'the second plies
38,40 respectively. The second filler 46 extends from
each bead portion 22,22' radially ~~utward to beneath
the reinforcing belt structure 36.
The elastomeric first fillers 42 have a thickness
B at the location of the maximum section width of the
tire 10 of at least three percent (3%) of the maximum
section height (SH), preferably of at least six
percent (6%) and not greater than twelve percent (12~)
of the maximum section height of the t~.re.
For purposes of this invention, the maximum
section width (SW) of the tire is measured parallel to
the rotational axis of the tire from the axially outer
surfaces of the tire , exclusive of indicia, adornment
and the like. Also, for the purposes of this invention
the tread width is the axial distance across the tire
perpendicular to the equatorial plane(EP) of the tire
as measured from the footprint of the tire inflated to
design inflation. pressure,at rated. load and mounted on
a wheel for which it was designed. In the particular
embodiment illustrated, the elastc~meric first fillers
42 each have a thickness E~ of approximately seven
percent (°7%) of the maximum sectioni height (SH) at the
maximum section width of the tire.
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The elastomeric second filler:a 46 :have a
thickness C of at least one and one:-half percent(1.5%)
of the maximum section height of the tire l0 at the
location of the maximum section width of the tire. In
the preferred embodiment the elastomeric second
fillers 46 each have a thickness C of approximately
three and one-half percent (3.5%) of the maximum
section height (;~H) of the tire.
The overall cross-sectional thickness of the
elastomeric fillers 42,46,and 48 preceding from the
bead portion 22,22~ to the shoulder portion 14,1.6 is
preferably of constant thickness.
The overall sidewall thicknes:> F in the region
where it merges into the shoulder portions 14,16 is at
least one hundred percent (100%) of the overall
sidewall thickness as measured at the maximum section
width SW of the 'tire. Preferably, i~he overall
thickness F of the sidewall in the shoulder regson of
the tire is approximately one hundred twenty five
percent (125%) of the overall side~Nall thickness at
the maximum section width SW.
applicants :have found that by placing a
reinforcing elastomeric filler between adjacent
reinforcing ply structures in the manner previously
described, high levels of run flat performance can be
obtained. During normal operation of th.e tire, the
inflated medium :provides the neces~aary support to
carry the load: :However, when the 'tire is operated in
the uninflated state the sidewall portions must
support the entire load. The tire construction of the
present invention permits efficiewt use of the carcass
structure in the uninflated condition while also
providing the desired operating performance
characteristics ~of the tire when operated in the
inflated state. 'When the tire is operated in the
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14
uninflated state, deflection of the tare is only slightly
greater than when operated in the inf:Lated state: The
internal surfaces of the tire do not come into contact with
each other during operation in the un:inflated state.
Pneumatic passenger tires made in accordance with the
present invention have been found to be capable of operation
in the uninflated state for distances of aloout 100 miles
(160 km) at speeds of up to 55 miles per hour (88 km/h) at
80% of the 26 psi :normal rated load pE,r Tire and Rim
Association and then be returned to normal operation in the
inflated state. The drivable range in the uninflated
condition can be i:n excess of 1000 mi:Les (:1600 km) .
Performance of the tire when operated in the
underinflated or u:ninflated condition may be enhanced by
selecting a tread design which provides high lateral
stability at the lateral end portions of the tread.
Preferably, the tread design is as taught .in co-owned United
States Patent No. 5,360,043, issued N<>vember 1, 1994.
Run flat performance of the tire may be further
enhanced by providing the ply coat of each layer of the
reinforcing ply structures 38,40 with an elastomeric
material having substantially the same. physical properties
as that of the elastomeric fillers 42,,46. As is well known
to those skilled in the tire art, the ply coat of a fabric
layer is the layer of unvulcanized elastomeric material
which is applied to fabric prior to its being cut to its
desired shape and applied to 'the tire on the tire building
drum. Preferably, the elastomeric mate?rial used as a ply
coat for the ply layers is similar to the elastomeric
material used in tlae reinforcing fillers 42,46.
In practice, the rubber cornposit.ions for the first
fillers 42, second fillers 46 and the plycoats
CA 02428290 2003-05-27
for one or more ply structures 38 and 40 utilized in
this invention for the aforesaid pneumatic tire
construction are preferably characterized by physical
properties which enhance their utilization in the
5 invention which are, collectively, believed to be a
departure from properties of rubber compositions
normally used in pneumatic tire sidewalls,
particularly the combination of first a.nd second
fillers 42 and 46 with plies 38 and/or 40 having
10 similar high stiffness/low hysteres is properties as
hereinafter described.
Preferably, while the discussion herein refers to
the plycoat(s) being for one or more of ply structures
38 and 40, in the practice of this invention,- the
15 plycoats referenced herein refers to plycoats for both
plies 38 and 40 unless only one of such plies is used.
In particular, for the purposes of: this
invention, both of the aforesaid fillers 42 and 46 are
characterized by having a high degree of stiffness yet
by also having a relatively low hysteresis for such a
degree of stiffness.
The stiffness of the rubber composition for
fillers 42 and 46 is desirable for stiffness and
dimensional stability of the tire sidevaall.
The stiffness of the rubber composition for the
ply coat for one or more of plies 38 and 40 is
desirable for overall dimensional staba.lity of the
tire carcass, including its sidewalls, since it
extends through both sidewalk and acrass the crown
portion of the tire.
As a result, it is considered that the stiffness
properties of the aforesaid rubber compositions of the
first and second fillers 42 and 46 and of the ply
structures 38 and/or 40 cooperate with the plies 38
and/or 40 to reinforce each other and to enhance the
CA 02428290 2003-05-27
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aforesaid dimensional stability of the tire sidewalls
to a greater degree than if either of the aforesaid
fillers or plycoats were alone provided with a high
stiffness rubber composition.
However, it is to be appreciated that rubbers
with a high degree of stiffness in pneumatic tires
normally be expected to generate e:~cessive internal
heat during service conditions (opE~rating as tires on
a vehicle running under load and/or without internal
inflation pressure), particularly when the rubber~s
stiffness is achieved by a rather conventional method
of simply increasing its carbon black content. Such
internal heat generation within the rubber comp~sition
typically results in a temperature increase of the
stiff rubber and associated tire structures which can
potentially be detrimental to the useful life of the
tire.
The hysteresis of the rubbercomposition is a
measure of its tendency to generate internal heat
under service conditions. Relatively speaking, a
rubber with a lower hysteresis property generates less
internal heat under service conditions than an
otherwise comparable rubber composition with a
substantially higher hysteresis~ 'Thus, in one aspect,
a relatively low hysteresis is desired for the rubber
composition for the fillers 42 and 46 and the
plycoat(s) for one or more of the plies 38 and 40.
Hysteresis is a term for heat energy expended. in
a material (eg: cured rubber composition) by applied
work and low hysteresis of a rubber composition is
indicated by:a relatively high rebound,, a relatively
low internal friction and relatively low loss modu.lus
property values.
Accordingly, it is important that the rubber
compositions for the fillers 42 and 46 and plycoats
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for one or more of plies 3S and 40 have the properties
of both relatively high stiffness and low hysteresis.
The following selected desirable properties of .
the rubber compositions for the fi:Llers 42 and 46 as
well as for the ?~lycoats for one oar more of the plies
38 and 40 are summarized in the fo:Llowing Table 1.
Ta.~ 1 a 1
Properties Filler Ply Coat
Hardness (Shore A)2 60. - '~0 60 -'70
Modulus (100%) MPa3 5 - 7 4 - 6
Static Compression) 0.1- 0.15 0.15- 0.10
Heat Buildup (C)1 <30 <30
Cold Rebound 55 - '70 55 - d0
(about 23C)4
E' at 100C (MPa) 10 - 15 10 -15
E' at 1~~C (MPa) 0.5- 1.5 1 - 1.5
1. Goodrich Flexometer Test-ASTM Test No. D623
2. Shore Hardness Test-ASTM Test No. D2240
3. Tension Modulus Test-I~STM Test No. D412
4. Zwick Rebound Test-DINT 53512
The indicated hardness property is considered to
be a moderate rubber hardness.
The indicated modulus property at 100% modulus is
utilized instead of a 300% modulus because the cured
rubber has a relatively low ultimate e~_ongation at its
breaking point. Such a cured rubber is considered
very stiff.
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1~
The indicated static compression property,
measured on a flexometer, is another indication of the
relatively high stiffness of the cured rubber.
The indicated E' property is a coefficient of the
storage or elastic moduli component of the
viscoelastic property which is an i:ndica.tion of the
material (eg: cured rubber composition) stiffness.
The indicated E" property is a coefficient of the
loss or viscous moduli component of the viscoela~tic
property which is an indication of the hysteretic
nature of the material (eg: cured rubber composition).
The utilization of both the E' and E" properties
to characterize stiffness and hysteresis of rubber
compositions is well known to those having skill in
such characterizations of rubber.
The indicated heat buildup value is measured by a
Goodrich flexomet.er (STN! D523) test and is indicative
of the internal heat generation of the material (eg:
cured rubber composition).
The indicat~:d cold rebound test property at about
23°C (room temperature) is measured. by uwick Rebound
Test (DIN 53512) test and is indicative of the
material's (eg: cured rubber composition) resilience.
Thus, the properties illustrated in Table 1
indicate a cured rubber composition. with a relatively
high stiffness, moderate hardness a.nd a relatively low
hysteresis for a rubber with such a. high stiffness.
The low hyst.eresis is demonstrated by the
relatively low heat buildup, low E~° and high rebound
properties and is. considered raeces~~ary for a rubber
composition desired to have a relatively low internal
heat buildup in service.
In the compounding of the varioustire
components, various rubbers may be used which are,
preferably, relatively high unsaturation dime-based
CA 02428290 2003-05-27
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rubbers. Representative examples of such rubbers are,
although they may not be so limited, aree styrene-
butadiene rubber, natural rubber, cis 1,4 and 3,4-
polyisoprene rubbers, cis 1,4 and ~srinyl 1,2-
polybutadiene rubbers, acrylonitri:le-butadiene rubber,
styrene-isoprene-butadiene rubber and styrene-isoprene
rubber.
Various of the preferred rubbers for the rubber
compositions for the fillers 42 and 46 and for the
plycoat(s) for one or more of the ;plies 38 and 40 are
natural cis 1,4-polyisoprene rubber,
isoprene/butadiene rubber, and cis 1,4~polybutadiene
rubber.
Preferred combinations, or blends, of rubbers are
natural cis 1,4-polyisoprene rubber and cis 1,4-
polybutadiene rubber for the fillers and. natural cis
1,4-polybutadiene rubber and isoprene/butadiene
copolymer rubber for the plycoat(s).
In a preferred practice, based on 100 parts by
weight rubber, (A) the fillers are comprised of about
60 to 100, preferably about 60 to 80, parts natural
rubber and, correspondingly, up to about 40,
preferably about 40 to about 10, parts of at least one
of cis 1,4 polybutadiene rubber and isoprene/butadiene
rubber preferably cis 1,4-polybutadiene rubber, where
said isoprene/butadiene rubber, if used, is present in
a maximum of 20 parts, and (B) the said plycoat(s) are
comprised of up to 100, preferably about 80 to about
100 and more preferably about 80 to about 95, parts
natural rubber and, correspondingly, up to about 100,
preferably up to about 20 and more preferably about 20
to about 5, parts of at least one of
isoprene/butadiene copolymer rubber and cis 1,4
polybutadiene rubber, preferably a.n isoprene/butadiene
rubber; wherein the ratio of isoprene s~o butadiene in
CA 02428290 2003-05-27
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said isoprene/butadiene copolymer :rubber is in a range
of about 40/60 to about 60/40.
It is further contemplated, arr~d is considered to
be within the intent and scope of 'this invention that
a small amount, such as about 5 to about 15 parts, of
one or more organic solution polymerization prepared
rubbers may be included with the aforesaid natural
rubber, and cis 1,4 polybutadiene rubber and/or
isoprene/butadiene rubber compositions) for the said
fillers and/or plycoat(s), of which the option and
selection of such additional rubbers) can be made by
one having skill in the rubber compounding art without
undue experimentation.
Thus, in such circumstance, the description of
the filler and plycoat rubbers is set forth in a
"comprising°' manner with the intent that small amounts
of such solution. polymerization prepared elastomers
can be added so long as the aforesaid physical
property parameters of the cured rubber compositions
are met. It is considered that such rubber
compounding is within the skill of those with
experience in tY~.e rubber compounding art without undue
experimentation.
While not necessarily limited. thereto, such other
contemplated solution prepared rubbers are
styrene/butadiene, and polymers of oneor more of
isoprene and butadiene such as 3,4-polyisoprene,
styrene/isoprene/butadiene terpolyers and medium
vinyl polybutadiene.
It should readily be understood. by one havingw
skill in the art. that rubber compositions for
components of the pneumatic tire, including the first
and second fillers 42 and 46 as well as ply coat (s)
for one or more or plies 3~ and 4Ci, can be compounded
by methods generally known in the rubber compounding
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art, such as mixing the various sulfur-vulcanizable
constituent rubbers with various commonly used
additive materials such as, for example, curing aids,
such as sulfur, activators, retarders and
accelerators, processing additives, such as rubber
processing oils, resins including tackifying resins,
silicas, and plasticizers, fillers, pigments, steario
acid or other materials such as tall oil resins, zinc
oxide, waxes, antioxidants and antiozonants, peptizing
agents and reinforcing materials such as, for example,
carbon black. As known to those skilled in the art,
depending on the intended use of the sulfur
vulcanizable and sulfur vulcanized materials
(rubbers), the certain additives mentioned above are
selected and conunonly used in conventional amounts.
Typical additions of carbon black comprise about
30 to about 100 parts by weight, of diene rubber
(phr), although about 40 to about a maximum of about
70 phr of carbon black is desirable for the high
stiffness rubbers desired for the :indicated fillers
and plycoaa(s) used in this invention. Typical
amounts of resins, if used, including tackifier resins
and stiffness resins, if used, inc:iuding unreactive
phenol formaldehyde tackifying resins and, also
stiffener resins of reactive phenol formaldehyde
resins and resorcinol or resorcinol and hexamethylene
tetramine may collectively comprise about 1 to l0 phr,
with a minimum tackifier resin, if used, being 1 phr
and a minimum stiffener resin, if used, being 3 phr.
Such resins may sometimes be referred to as phenol
formaldehyde type resins. Typical amounts of
processing aids comprise about 4 to about 100 phr.
Typical amounts of silica, if used, comprise about 5
to about 10 or 15 phr and amounts of silica coupling
agent, if used, comprise about 0.05 to about 0.25
CA 02428290 2003-05-27
- 2 2
parts per part of silica, by weight.. Representative
silicas may be, :Eor example, hydrated amorphous
silicas. A representative couplinc; agent may be, for
example, a bifunctional sulfur coniraining organo
silane such as, .for example, bis-(:3-triethoxy-
silylpropyl) tetrasulfide, bis-(3-t~rimethoxy-
silylpropyl) tet:rasulfide and bis-(3-trimethoxy-
silylpropyl) tet:rasulfide grafted ;silica from DeGussa,
AG. Typical amownts of antioxidanirs comprise 1 to
about 5 phr. Representative antio:~idants may be, for
example, Biphenyl-p-phenylenediamine and others, such
as those disclosed in the Vanderbi:lt Rubber Handbook
(1978), pages 344-346. Suitable a:r~tiOZOnant(s) and
waxes, particularly microcrystalli:ne waxes, may be of
the type shown in the Vanderbilt Rwbber Handbook
(1978), pages 346-347. Typical amounts of
antiozonants comprise 1 to about 5 phr. Typical
amounts of stearic acid and/or tall oil. fatty acid may
comprise about 1 to about 3 phr. ical amounts of
zinc oxide comprise about 2 up to about: 8 or l0 phr.
Typical amounts of waxes comprise l to about 5 phr.
Typical amounts of peptizers comprise 0.1 to about 3
phr. The presence and relative amounts of the above
additives are not an aspect of the present invention
which is primarily directed to the utilization of
specified blends of resins in tire treads as sulfur
vulcanizable compositions.
The vulcanization is conducted in the presence of
a sulfur vulcanizing agent~ Examples of suitable
sulfur vulcanizing agents include elemental sulfur
(free sulfur) or sulfur donating vulcanizing agents,
for example, an amine disulfide, polymeric polysulfide
or sulfur olefin adducts. Preferably, the sulfur
vulcanizing agent is elemental sulfur. As known to
those skilled in the art, sulfur vulcanizing agents
CA 02428290 2003-05-27
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are used in an amount ranging from about 0.5' to about
8 phr with a range of from 3 to about 5 being
preferred for the stiff rubbers de.~i.red for use in
this invention.
Accelerators are used to control t:he time and/or
temperature required for vlalcanizat:ion .and to improve
the properties of the vulcanizate. In one embodiment,
a single accelerator system may be used, i.e.., primary
accelerator. Conventionally, a primary accelerator is
used in amounts ranging from about 0.5 to about 3 phr.
In another embodiment, combinations of two or more
accelerators in which a primary accelerator is
generally used in the larger amount (0.5 to about 2
phr), and a secondary accelerator which is generally
used in smaller amounts ~0.. 05- .50 ~ahr) in order to
activate and to improve the properties of the
vulcanizate. Combinations of such accelerators have
historically been known to produce a synergistic
effect of the final properties of sulfur cured rubbers
and are often somewhat better than those produced by
use of either accelerator alone. rn addition, delayed
action accelerators may be used which are less
affected by noranal processing temperatures but produce
satisfactory cures at ordinary vulcanization
temperatures. Representative examples of accelerators
include amines, disulfides, guanidines, thioureas,
thiazoles, thiurams, sulfonamides, dithiocarbamates
and xanthates. Preferably, the primary accelerator is
a sulfonamide. If a second accelerator is used, the
secondary accelerator is preferably a guanidine,
dithiocarbamate or thiuram compound, although a second
sulfonamide accelerator may be used. In the practice
of this invention, one and sometimes two, or more
accelerators are preferred for the high stiffness
rubbers.
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The tire can be built, shaped, molded and cured
by various methods which will be readily apparent to
those having skill in the art.
EXAMPLE 1
The following rubber compositions are provided
which are intended to exemplary of rubber compositions
with properties which can fall within those
exemplified in Table 1.
Rubber compositions are prepared and mixed by
conventional rubber mixing processes and comprised of
the materials shown in Table 2 which represent rubber
compositions which may be contemplated for use as
fillers 42 and 46 and ply coats) for one or more of
plies 38 and 40. The indicated amounts of materials
have been rounded for the illustration of this
Example.
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Table 2
(Parts by Weight)
Material P~coat Filler
Natural Rubbers 90 80
Isoprene/Butadiene Rubber2 10 0
Polybutadiene (cis 1,4-) Rubber3 0 20
Carbon black 55 55
Zinc Oxide 5 8
Accelerators (Sulfenamide type) 4 2
Sulfur (insol w/2%. oil) 2 4
Conventional amounts of rubber processing oil and
tall oil fatty arid, collectively about 5 parts with a
Z5 minimum of 1 part each; antidegradants; tackifying and
stiffening resinv, primarily of thf~ phenolformaldehyde
type in an amount of about 6 phr; and silica and
coupling agent therefor; are used with two
accelerators for the plycoat sample and one
accelerator for the filler rubber composition sample.
1. Cis 1,4-polyisoprene type
2. Copolymer with ratio of isoprene to
butadiene of about 1:1
3. A high cis 1,4 polybutadiene rubber
The rubber compositions are molded and cured at
about 150°C for about 20 minutes.
In the practice of this invention, it is
considered important that the rubber compositions for
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- 26 -
both the fillers 42 and 46 and the ply coatis) for one
or more of plies 38 and 40 are relatively very stiff,
moderately hard, and have a low hysteresis.
Further, it is normally desired that the rubber
composition for fillers 42 and 45, relative to the
rubber compos~itzon for plycoats for plies 38 and/or 40
is slightly stiffer, slightly harder and that both of
the rubber compositions have a relatively low
hysteresis.
It is important to appreciate that the indicated
physical properties of the rubber compositions in
Table 1 are for samples thereof and that the
dimensions, including thickness, of the resulting tire
components (fillers and plies) need be taken into
I5 account as factors contributing to the overall
stiffness and dimensional stability of the tire
sidewall and carcass.
It is considered important that the stiffness of
the rubber composition for fillers 42 and 46 is
somewhat greater than that of the aforesaid ply coat
rubber composition because they are not a part of a
fabric reinforced ply and further, because it is
desired to somewhat maximize their stiffness property:
The hysteresis, or E", and heat buildup values
for the rubber composition for the aforesaid fillers
is desirably somewhat lower than that for the rubber
composition for the aforesaid ply coats) because of
the bulk of the fillers versus the thin dimensions of
the fabric reinforced plies.
Chaffing of the tire in the lower bead region
radially outward of the carcass structure 30 adjacent
the rim flange may be minimized,e~~pecially during use
of the tire in the uninflated condition, by providing
hard rubber chaffer portion 60,60'.
CA 02428290 2003-05-27
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High speed performance of the tire may be
enhanced by the application of a fabric overlay layer
59 disposed about the tread reinforcing belt structure
36. For example, two ply layers having nylon or aramid
cords may be disposed about reinforcing belt structure
36, the lateral ends of extending past the lateral
ends of the belt structure 36. Alternatively, a single
layer of spirally wound aramid reinforced fabric can
be employed as an overlay. The ara.mid material has a
substantially higher modulus of elasticity than nylon
and accordingly results in a stronger tire
reinforcement than two layers of nylon. Applicants
have found that a greater than 10% increase in high
speed capability can be achieved in a tire with the
single layer of apirally wound arar~id overlay.
Generally the use of aramid material in passenger tire
applications is avoided due in part to the fact that
the material exhibits poor noise properties that
resonate sounds through the relatively thin sidewalls
of the passenger tire. Applicants' tire of the present
invention employs thick sidewalls which, noticeably
dampen tire generated noises. The noise dampening
sidewalls permit the use of an aramid overlay without
experiencing unacceptable noise le~~els.
In the illustrated preferred embodiment, the
aramid reinforced fabric is wound circumferentially
about the reinforcing belt layers overlapping the belt
edges. The overlay fabric 59 is wrapped in
approximately 2.5 cm (1.0 inch) wide strips which are
abutted. Alternatively, each strip may overlap the
adjacent wound strips. Preferably the strips overlap
in the range of 25% to 100% of the strip width. At
the axial extremes of the overlay, the strips may
include multiple winding for added strength at these
highly stressed areas.
CA 02428290 2003-05-27
28
L~Thile certain representative embodiments and
details have been shown for the purpose of
illustrating the invention, it will be apparent to .
those skilled in this art that various changes and
modifications may be made therein without departing
from the spirit or scope of the invention.
