Note: Descriptions are shown in the official language in which they were submitted.
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The rolling resistance of one-ply tires is believed to be
superior to that of mLltiple ply tires. Because tires with low rolling
resistance conserve energy, a one-ply tire is a desired form of tire.
An increasing proportion of the tires which are bPing manufactured
today are one ply radial tires. ~hen certain ma~rials which have high
modulus but poor resistance to ccmpression fatigue, such as fiberglass, spun
steel wi~e and aramid, are used in the ply or bod~ reinforcement portion
of a radial tire, there is a tendency for the ply to break in the crawn
area. These breaks can lead to breaks in the inner liner and tire failure.
This is believed to be caused by the pantographing action of the cincture ~ -
belt of the tire.
By high modulus is meant an initial modulus of from 200 to 600
GæD/100% or higher. GæD/100% means grams force per denier at 100% elongatian
as determined by ASTM Procedure ~885-76.
Radials are naw predomlnantly tw~-ply construction but there is
a trend toward one-ply for reasons of economy and also lawer rolling
resistance. The one-ply radial can be made with n~lon or polyester body
cords beaause of the good resistance to compression fatigue but there are
advantages in using high modulus cords. The high modulus materials generally
have low thermal shrinkage which contributes to good dimensional stability
and also uniformity. Unfortunately, poor resistance to compression fatigue
acconpan~es the high m~dulus properties.
The trend is toward these high modulus materials and the invention
is a way of getting around the prablems which will probably be encountered
in one-ply high modulus plies. ~his problem exists with Kevlar* (aramid~,
fiberglass and fine filament steel cords, the biggest problem being with
glass.
Radial tires are ordinarily made on special equipment but can be
and are made on conventional equipment. We prefer to use radial tire
eguipment, however.
The problem of ply cord breakage in the crown of the tire probably
would not occur in some prior art aonfigurations. Examples of prior art where
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ply cord breakage w~uld not occur in the crown area are those described by
Burdon m Uhited States Patents 2,493,614 (1950) and 3,192,984 (1965).
~hat Burdon does is to elimunate the center cord plies and replace then with
a high modulus rubber. According to Burdon this provides a softer ride and
prevents, to some degree, noise transmission that wDuld normally occur
throughout the tire cords. A variation of the Burdon theme is found in
Australian Patent 27,833/71 Guyot.
The Guyot patent is directed to a tire having two carcass plies
ex$ept in the crown area. In the crown area Guyot eliminates one of the
carcass plies.
Some of the problems encountered with the prior art tires are as
follows. The carcass of a radial tire is normally manufactured on a flat
drum. It would appear that it w~uld be easier ~or a tire builder to apply a
single radial cord ply to the drum and aenter it rather than apply two
relatively narrow partial plies, one on each side of the tire, and get them
absolutely parallel. It would seem that force variatiQns might exist around
the circumference of a tire during use if the partial plies were not aligned
properly.
Anokher problem which would occur during tire building, the tire
carcass, as it is made on a 1at drum, is expanded to a t~roidal shape. I
there was no carcass ply in the center of the tire but only an insert under
the ply and the tire were expanded with an in1at~b1e rubber bladder, the
center of the carcass wDuld exFand as the aord ply would be pulled fnom the
center due to cords sliding in the rubber. This is particularly true of the
newer glass cords which have low cohesiveness to unaured rubber compound.
The prior art tires discussed here are the Burdon and Guyot tires.
Another problem with the Burdon tires ~hich elimlnates carcass
ply from the center of th~ tire is that of crack propagation. Burdon
replaaes the strength o tire cords with high modulus rubber. ~hen a crack
forms in such a material, continued flexing of the tire will cause the crack
to propagate through the rubber.
The object of the invention is to provide a cQntinuous one-ply
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radial tire made from standard high modulus ply matcrials which
has improved resistance to cord failure and performs as well as
regular two-ply radial tires.
In accordance with the present invention, there is
provided a radial ply pneumatic tire of the type comprising a
continuous ply from bead to bead of radial cord reinforcement
having an initial modulus greater than 200 GPD/100~ embedded in
an elastomeric matrix, an inner liner contiguous to the ply,
and a cincture belt reinforcing the tread portion of the tire,
which additionally includes an insert sheet positioned under
the radial center line of the tire, circumferentially disposed
around the tire and embedded in an elastomeric matrix between
the inner liner and the ply; the insert being formed of a
material having a break strength reduction of not more than
35% after 10.8 megacycles using Goodrich Disk fatigue test
method; the insert having an axial width less than the axial
width of the cincture belt; and the material including rein-
forcing cords oriented in the same direction as the reinforcing
cords of the plyO
Suitable materials for the insert are those with
; good compression fatigue resistance, such as rayon, polyester
or nylon tire cord materialO As indicated, such materials can
be characteri7ed by a Goodrich Disk fatigue as determined in a
Goodrich fatigue tester of 10.8 megacycles. The cori would not
be expected to lose more than 35% of its breaking strength at
10.8 megacyclesO The conditions the machine would be running
at are a compression of 6.3% and an elongation of 12.6% while
the cord is embedded in rubber. In this way, it is possible
to build a one-ply radial tire which performs substantially as
well as a two-ply tire, has lower rolling resistance, and has
cost and manufacturing advantages.
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In the practice of the present invention, all of the
difficulties encountered in the practice of the Burdon and
Guyot inventions outlined above have been eliminated. In build-
ing the tire, according to the present invention, a single sheet
made of glass cords and a center insert made of polyester cords
can be used by the tire builder in constructing the tire. There
is no problem expanding the carcass from a flat drum configura-
tion to a toroidal shape because the carcass is reinforced
across its entire width with reinforcing cord. Alss, when a
circumferential crack starts in the continuous ply of the tire
of the present invention, it can only propagate through the
rubber and will not propagate through the cord reinforcement
and the inner liner whereas it could propagate through an insert
of high modulus rubber.
Figure 1 is a partial perspective view, with portions
broken away, of a one-ply radial tire assembly according to the
present invention.
Figure 2 is a plan view, with portions broken away,
of the crown or top of the tire of Figure lo
One form of the invention is shown in Figures 1 and
2 which depict a one-ply tubeless radial tire 1 of generally
toroidal shape with a tread or crown portion 2, sidewall por-
tions 3 and 4, a circumferential belt or cincture assembly 5,
a butyl rubber inner liner 6, and a single ply 7 of
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continuous parallel radial cords comprising a single CQntinuOuS ply portion 7.
me single ply 7 is located next to the inner liner 6, ply portion
7 extending from one tire bead through the tread section to the other tire
bead. The radial ply portions extend around the shouldPr of the tire, which
is the junction of the tread and sidewall, and well inside the cincture
belt 5. If the width of the tread on the road is five inches, for example,
the width of the cincture belt is preferably about 5-3/4 inches.
In accordance with the invention, an insert sheet 9 is placed
between the inner liner and the continuous radial body ply. The insert
underlies the ply. m e insert is made of conventional polyester tire cord
fabric with superior compression and fatigue resistance and preferably has a
multiplicity o mutually parallel, continuous co~ds which are parallel to the
radial ply cords and extends in width substantially from one shoulder of the
tire to the other. It may be of the same width as the cincture belt 5 or
somewhat smaller in width.
The cords of the radial plies are preferably made of fiberglass,
other high mcdulus material ccmmonly used in tire cords, such as steel wire
or aramid fibers can be used. These high modulus materials generally have
poor ccmçression fatigue resistance.
The cords of the insert sheet 9 are made of common tire cord
; materials which hav~ ~od compression fatigue ~esistance, such as nylon, rayDn,
polyester, PU~ and other materials well kn~wn in the art for use in tire cords.
The term "polyester" as applied to tire cord materials includes polyethvlene
terephthalate fiber. The term "PU~" means a polyvinyl alcchol fiber~
A tire with one continuous glass fiber radial ply having a
polyester insert and a steel c mcture belt was compared against a glass fiber
two-ply radial tire with a steel belt in dynamlc tire tests and pPrfo~med well.
CbrresFonding tires were built having a center gap in the radial
ply and were d inferior quality to the continuous ply tire. When glass cords
made by current manufacturing methods were used to build tires having a center
gap in th.e ply, they were too deformed to be used for test purposes. It is
believed that the glass ply tires of the present invention are far superior
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to those of Guyot, because the Gu~ot tire cannot be made in conventional
radial tire building e~uipment using glass cord currently available. Ihis
cord has insufficient cohesiveness to uncured rubber compound to prevent
deformation in the building prwess.
~ he cords of the insert 9 are preferably parallel or very nearly
parallel to the cords of the radial ply in order to obtain low rolling
resistance, I believe, however, that the insert could also be a non-woven
tire fabric sheet.
The mutually parallel cords of the radial ply and the msert are
embedded in an elastomeric matrix-as in conventioNal tire cord fabric as
commonly used. These procedures æe well kncwn to those s~illed in the art.
While the advan$ages of the invention principally accrue when
the insert is employed in a continuous one-ply radial tire, it should be
apparent that some benefits can be obtained with two-ply radial tires.
Obvious mDdifications which can be made relative to the foregoing
description are intended to fall within the scope of the invention.
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