CA1060732A

CA1060732A - Tire cord with a synthetic fiber core

Info

Publication number: CA1060732A
Application number: CA267,927A
Authority: CA
Inventors: C. Paul Russell; Oswald A. Drica-Minieris; Joseph M. Gingo
Original assignee: Goodyear Tire and Rubber Co
Current assignee: Goodyear Tire and Rubber Co
Priority date: 1976-01-16
Filing date: 1976-12-15
Publication date: 1979-08-21
Also published as: MX145482A; DE2701025A1; IT1076523B; JPS5811325B2; JPS5288902A; FR2338152A1; NL7700064A; LU76543A1; DE2701025C2; FR2338152B1; IE44049L; GB1535105A; ZA767438B; IE44049B1; NL179224B; NL179224C

Abstract

A TIRE CORD WITH A SYNTHETIC FIBER CORE
Abstract of the Disclosure A composite tire cord composed of a plurality of twisted steel strands which are cabled around a multi-filament core of aramid.

Description

Back~round of the Invention The invention is especially suitable in the wire reinforcement of the carcass plies and annular belt reinforcement of tires used on large trucks and earthmover-type vehicles. Such wire reinforcements or cords are normally composed of a number of steel strands which are cabled together to form the desired cord construction~ each of the steel strands~ in turn~
being composed of a plurality of individual steel filaments or wires which are twisted together. me steel strands are designed to carry an equal share of a load imparted to the cord during the operation of the tire. Voids are inescapably formed within the cabled cord. It has been found that moisture~ trapped within the tire during the building and operation of the tire, finds its way into these voids and eventually causes the corrosion of the individual steel wires. Corrosion can be prevented or greatly reduced by filling the voids or interstices of a metal cord with corrosion resistant material~ such as any suitable rubber cement or adhesive~ or an appropriate hydrophobic material~
e.g. polyolefins~ such as polyethylene~ polypropylene, polybutene and copolymers of such olefins. A centrally disposed core of synthetic polyester fibers around } 25 which the steel strands are wrapped, was found highly effective in decreasing the corrosion of the steel wires.
Unfortunately~ such cores reduce the strength of the cord reinforcement~ since the cores are simply not .
capable of carrying the loads th~t the steel strands are able to carryl ~ typical example oP such a cord is found in U. S, Patent No. 3,756,883 which describes a core which is purposely designed to break to allow the uncoiling of the strands that are cabled around the core~ The invention is designed to provide a steel cord reinforcement with a load carrying core - which does not detract appreciably from the overall strength of the reinforcement, The invention accordingly comprises a composite cord for a tire having a body of corrosion-resistant material, comprising a plurality of metal strands' having equal diameters and tensile strengths and-a central disposed, non-metallic core having a generally . 15 ' circular cross section around which the strands: are ' cabled~ The core has a diameter to spread the metal ~ - ' strands for penetration of the corrosion-resistant : 'material between the strands so that the corrosion- .
resistant material may cover and adhere to the strands to prevent exposure of the metal strands to moisture.
The core has-a-tensile strength and load-carrying - - ' - ' capability to maintain the strands in the spread ~ ' -condition under tension and carry a proportional . amount of the load on the cord, Det'ail'ed Description -of'th'e I-nvention - With reference-to the drawing, which is a cross-section of a steel tire cord reinforcement 5 used in -the carcass plies or annular reinforcement belts of large earthmover tires, there is shown a centrally ~.
.~

disposed, non--metallic core 6 composed D~ inorganic, aramid filaments. An appropriate num~er of steel strands 7-12 are cabled or spirally wrapped around the .
multi~ilament core 6 of aramid. The steel strands 7-12 are each composed of a desired number of steel filaments or ~ires 13-16 which are twisted together. The individual steel wires 13-16, in this instance, have a - diameter of .1-75-millLmeters, and the steel strands -7-12-- ' '' - ' .
.

. .

.

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~ a--~06073Z
each have a lay o~ 10 millimeters (mm) in an S
direction. m e steel strands 7-12~ in turn~ have a lay around the aramid core 6 of 19 mm in a Z direction.
me aramid core 6 has a high tensile strength which is substantially equal to~ or closely approximates that of any one of the individual steel strands 7-12. A multi-filament yarn or strand of aramid~ having a 1500 denier~
of minimal twist~ and treated with an agent for increas-ing the adhesion between the multifilament and rubber material in which the steel cord 5 is embedded~ was successfully used as a core 6. Two slightly cabled aramid yarns of 1000 denier each~ similarly treated~
were also successfully used as a core 6.
It is important that the aramid core 6 completely fill the centrally disposed void created by the cabled or spirally wrapped steel strands 7-12. To accomplish -this~ the diameter of the aramid core 6 should be at least equal to the diameter of each of the steel strands 7-12 which are equally si~ed. In some instances, it is beneficial to use an aramid core 6 which is slightly larger than the steel strands 7-12 to spread the strands 7-12 slightly to increase the penetration of the rubber --material of the tire into the interstices of the steel cord 5 to more nearly surround the individual steel filaments 13-16 of each of the steel strands 7-12~
thereby reducing the voids in which moisture can become trapped and corrode adjacent wires. me aramid core 6 '~

~ -3-:~ .

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~060732 should not be too large to severely distort the con-figuration or geometry of the steel cord 5 so as to adversely affect the load-carrying characteristics or capacity of the steel cord 5 Thus~ the aramid core 6 not only acts as a load-carrying member of the composite steel and inorganic cord 5~ but fills the center void created by the coiled steel strands 7-12 to impede the flow of any moisture through the cord~ thereby preventing or greatly reducing corrosion of the individual steel filaments or wires 13-16 of each of the steel strands 7-12~
As previously mentioned~ attempts to use cores of other synthetic fibers~ such as polyester~ have proven unsuccessful. me polyester core reduced corrosion of the steel w~res, but was not sufficiently strong to carry its share of the load or tensile stress imparted to the cord reinforcement during the operation of a tire utilizing such cord reinforcements.
mus, there has been provided a composite cord reinforcement which utilizes a core that not only helps prevent corrosion of the steel strands of the reinforce-ment but acts~ in unison~ with the steel strands to shoulder a share of a load imparted to the composite cord reinforcements. Such a composite cord is different from prior art composite cords which utilize a low tensile strength breakable core~ or a dissolvable core~
or an elastic core for holding spirally wrapped cords - -- ~ :

in coiled relation until such time as the cords are tensioned to uncoil the cords and allow limited expansion of the tire in the area of the tire in which the cords are embedded. me composite cord reinforcement of the invention is useful in passenger tires as well as larger truck and earthmover tires.
While certain representative embodiments and details have been shown for the purpose of illustrating the invention~ it will be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the spirit or scope of the invention.

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Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A composite cord for a tire having a body of corrosion-resistant material, comprising a plurality of metal strands having equal diameters and tensile strengths and a centrally disposed, non-metallic core having a generally circular cross section around which said strands are cabled, said core having a diameter to spread said metal strands for penetration of said corrosion-resistant material between said strands so that said corrosion-resistant material may cover and adhere to said strands to prevent exposure of said metal strands to moisture, and said core having a tensile strength and load-carrying capability to maintain said strands in said spread condition under tension and carry a proportional amount of the load on said cord.

2. The reinforcement of claim 1 wherein the core is composed of aramid.

3. The reinforcement of claim 2 wherein the metal strands are steel, and each of the strands comprise a plurality of individual wires which are cabled together.

4. The reinforcement of claim 3, wherein the individual wires of each of the strands are twisted together in one direction and the strands are cabled around the core in a direction which is opposite the direction in which the wires are twisted.

5. The reinforcement of claim 1, wherein the core is not too large as to distort the geometry of the cord reinforcement to adversely affect the load-carrying characteristics of the reinforcement.

6. A tire having a body of corrosion-resistant material comprising at least one layer of cords reinforcing the tire, each of said cords of said layer consisting of a plurality of metal strands having equal diameters and tensile strengths and a centrally disposed non-metallic core having a generally circular cross section around which the strands are cabled, said core having a diameter to spread said metal strands for penetration of said corrosion-resistant material between said strands so that said corrosion-resistant material may cover and adhere to said strands to prevent exposure of said metal strands to mositure, and said core having a tensile strength and load-carrying capability to maintain said strands in said spread condition under tension and carry a proportional amount of the load on said cord.

7. The tire of claim 6 wherein the core is composed of aramid.

8. The tire of claim 6 wherein the layer of said cords reinforces at least one carcass ply of the tire.

9. The tire of claim 6 wherein the layer of said cords reinforces at least one annular belt ply of the tire.