GB1598298A - Radial pneumatic tyres - Google Patents

Description

(54) RADIAL PNEUMATIC TIRES (71) We, THE GENERAL TIRE & RUBBER COMPANY, a corporation organized and existing under the laws of the State of Ohio, of One General Street, Akron, Ohio, United States of America do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed to be particularly described in and by the following statement: This invention relates to radial pneumatic tires The rolling resistance of one-ply tires is believed to be superior to that of multiple 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 being manufactured today are radial tires. When certain materials which have high modulus but poor resistance to compression fatigue, such as fiberglass, spun steel wire and aramid, are used in the ply or body reinforcement portion of a radial tire, there is a tendency for the ply to break in the crown 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. Because of this tendency to break, radial tires are generally of at least two-ply construction.

By high modulus is meant an initial modulus of from 200 to 600 GPD/100% or higher. GPD/100% means grams force per denier at 100% elongation as determined by ASTM Procedure D885-76.

Radials are now predominantly two-ply construction but there is a trend toward one-ply for reasons of economy and also lower rolling resistance. The one-ply radial can be made with nylon or polyester body cords because 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 accompanies the high modulus properties.

The trend is toward these high modulus materials and the invention is a way of getting around the problems which will probably be encountered in one-ply high modulus plies. This problem exists with Kevlar (Registered Trade Mark) (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 equipment, however.

The problem of ply cord breakage in the crown of the tire probably would not occur in some prior art configurations. Examples of prior art where ply cord breakage would not occur in the crown area are those described by Burdon in U.S. Patents 2,493,614 (1950) and 3,192,984 (1965).

What Burdon does is to eliminate the center cord plies and replace them with a high modulus rubber. According to Burdon this provides a softer ride and prevents, to some degree, noise transmission that would normally occur throughout the tire cords. A variation of the Burdon theme is found in U.S. Patent 3,058,509 Maiocchi (1962).

The Maiocchi patent is directed to a tire having two carcass plies except in the crown area. In the crown area Maiocchi eliminates one of the carcass plies. Looking at Figure 2 of Maiocchi, it is seen that the cords of the carcass plies do not appear to be straight. In the text Maiocchi refers to tires in which the "cords form a crossed structure".

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 would be easier for a tire builder to apply a single radial cord ply to the drum and center 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 variations might exist around the circumference of a tire during use if the partial plies were not aligned properly.

Another problem which would occur is: during tire building, the tire carcass, as it is made on a flat drum, is expanded to a toroidal shape. If there was no carcass ply in the center of the tire and the tire were expanded with an inflatable rubber bladder, it would seem that the center of the carcass would expand unevenly as the only component in the center of the tire at this stage of construction would be an inner liner. The prior art tires discussed here are the Burdon tires. The pertinency of the Maiocchi references, if it is pertinent, is not understood.

Another problem with the Burdon tires which eliminates carcass ply from the center of the tire is that of crack propagation.

Burdon replaces the strength of tire cords with high modulus rubber. High modulus rubber is relatively inextensive rubber.

When a crack forms in such a material, continued flexing of the tire will cause the crack to propagate through the rubber.

According to the present invention there is provided a radial pneumatic tire comprising spaced apart beads, a ply of radial reinforcing cords having an initial modulus greater than 200 GPD/100% embedded in an elastomeric matrix and extending continuously from one bead to the other bead, an inner liner, a cincture belt reinforcing the tread portion of the tire, and a circumferential insert sheet positioned between the inner liner and the ply and 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 material comprising reinforcing cords oriented in the same direction as the radial reinforcing cords of the ply embedded in an elastomeric matrix, the insert having an axial width equal to or less than the axial width of the cincture belt.

Thus a one ply radial tire made from standard high modulus ply materials may be obtained which can have an improved resistance to cord friction and can perform as well as regular two ply tires, which can have a lower rolling resistance and which can have cost and manufacturing advantages.

The break strength reduction of the cords of the insert sheet may be determined by a Goodrich fatigue tester of 10.8 megacycles, the tester running at a compression of 6.3% and an elongation of 12.6 o whilst the cords are embedded in rubber.

In the practice of the present invention, some or all of the difficulties encountered in the practice of the Burdon inventions outlined above can be eliminated. In building 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 configuration to a toroidal shape because the carcass is reinforced across its entire width with reinforcing cord. Also, 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 high modulus rubber.

An embodiment of the invention will now be described by way of example with reference to the accompanying drawing, in which; 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 1.

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 portions 3 and 4, a circumferential belt or cincture assembly 5, a butyl rubber inner liner 6, and a single ply 7 of parallel radial cords extending from one bead of the tire to the other bead (not shown).

The single ply 7 is located next to the inner liner 6, ply portion 7 extending from one tire bead and the sidewall 3 up into the tread section and then extends to the sidewall 4 and the other tire bead. The radial ply 7 extends around the shoulder 13 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 radial body plies. The insert underlies the ply. The insert is made of convention polyester tire cord fabric with superior compression and fatigue resistance and has a multiplicity of mutually parallel, continuous cords 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 modulus material commonly used in tire cords, such as steel wire or aramid fibers can be used.

These high modulus materials generally have poor compression fatigue resistance, particularly glass.

The cords of the insert sheet 9 are made of common tire cord materials which have good compression fatigue resistance, such as nylon, rayon, polyester, PVA and other materials well known in the art for use in tire cords. The term "polyester" as applied to tire cord materials includes polyethylene terephthalate fiber. The term "PVA" means a polyvinyl alcohol fiber.

A tire with one glass fiber radial ply a polyester insert and a steel cincture belt was run against a glass fiber two-ply radial tire with a steel belt and performed well.

The cords of the insert 9 are parallel or very nearly parallel to the cords of the radial ply in order to obtain low rolling resistance.

The mutually parallel cords of the radial ply are embedded in an elastomeric matrix when applied in the tire building operation and the cords of the insert sheet should likewise be embedded in a plastic matrix when applied as in conventional tire cord fabric as cornmonly used. These procedures are well known to those skilled in the art.

While the advantages of the invention may principally arise when the insert is employed in a one-ply radial tire, it is apparent that some benefits can be obtained with two-ply radial tires.

WHAT WE CLAIM IS: 1. A radial pneumatic tire comprising spaced apart beads, a ply of radial reinforcing cords having an initial modulus greater than 200 GPD/100% embedded in an elastomeric matrix and extending continuously from one bead to the other bead, an inner liner, a cincture belt reinforcing the tread portion of the tire, and a circumferential insert sheet positioned between the inner liner and the ply and 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 material comprising reinforcing cords oriented in the same direction as the radial reinforcing cords of the ply embedded in an elastomeric matrix, the insert having an axial width equal to or less than the axial width of the cincture belt.

2. A tire according to claim 1 wherein the ply is of fiberglass.

3. A tire according to claim 1 wherein the ply is of aramid.

4. A tire according to any one of the preceding claims wherein the cords of the insert are made of fibers of one or more of nylon, rayon, polyester or polyvinyl alcohol.

5. A radial pneumatic tire according to claim 1 substantially as herein described with reference to and as illustrated in the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (5)

**WARNING** start of CLMS field may overlap end of DESC **. as steel wire or aramid fibers can be used. These high modulus materials generally have poor compression fatigue resistance, particularly glass. The cords of the insert sheet 9 are made of common tire cord materials which have good compression fatigue resistance, such as nylon, rayon, polyester, PVA and other materials well known in the art for use in tire cords. The term "polyester" as applied to tire cord materials includes polyethylene terephthalate fiber. The term "PVA" means a polyvinyl alcohol fiber. A tire with one glass fiber radial ply a polyester insert and a steel cincture belt was run against a glass fiber two-ply radial tire with a steel belt and performed well. The cords of the insert 9 are parallel or very nearly parallel to the cords of the radial ply in order to obtain low rolling resistance. The mutually parallel cords of the radial ply are embedded in an elastomeric matrix when applied in the tire building operation and the cords of the insert sheet should likewise be embedded in a plastic matrix when applied as in conventional tire cord fabric as cornmonly used. These procedures are well known to those skilled in the art. While the advantages of the invention may principally arise when the insert is employed in a one-ply radial tire, it is apparent that some benefits can be obtained with two-ply radial tires. WHAT WE CLAIM IS:

1. A radial pneumatic tire comprising spaced apart beads, a ply of radial reinforcing cords having an initial modulus greater than 200 GPD/100% embedded in an elastomeric matrix and extending continuously from one bead to the other bead, an inner liner, a cincture belt reinforcing the tread portion of the tire, and a circumferential insert sheet positioned between the inner liner and the ply and 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 material comprising reinforcing cords oriented in the same direction as the radial reinforcing cords of the ply embedded in an elastomeric matrix, the insert having an axial width equal to or less than the axial width of the cincture belt.

2. A tire according to claim 1 wherein the ply is of fiberglass.

3. A tire according to claim 1 wherein the ply is of aramid.

4. A tire according to any one of the preceding claims wherein the cords of the insert are made of fibers of one or more of nylon, rayon, polyester or polyvinyl alcohol.

5. A radial pneumatic tire according to claim 1 substantially as herein described with reference to and as illustrated in the accompanying drawings.