IE44049B1

IE44049B1 - A tire cord with a synthetic fiber core

Info

Publication number: IE44049B1
Application number: IE2822/76A
Authority: IE
Original assignee: Goodyear Tire & Rubber
Priority date: 1976-01-16
Filing date: 1976-12-23
Publication date: 1981-07-29
Also published as: DE2701025C2; JPS5288902A; GB1535105A; FR2338152B1; NL7700064A; IE44049L; NL179224B; LU76543A1; JPS5811325B2; DE2701025A1; FR2338152A1; IT1076523B; MX145482A; CA1060732A; NL179224C; ZA767438B

Abstract

1535105 Tyre cord; non-metallic core wound with metal strands GOODYEAR TIRE & RUBBER CO 15 Dec 1976 [16 Jan 1976] 52284/76 Heading D1T A cord for tyre reinforcement comprises metal strands helically wound about a central, non-metallic core whose tensile strength, i.e. stress at rupture, is substantially equal to that of each strand. The core may be of aromatic polyamide, e.g. a multifilament yarn or strand, and the metal strands may each comprise steel wires twisted together in a direction opposite to the direction of twist of the strands about the core.

Description

The invention is especially suitable in the wire reinforcement of the carcass plies and annular belt reinforcement of tires used on large trucks and earthmovertype vehicles. Such wire reinforcements or cords are normally composed of a number of steel strands which are spirally wrapped 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. The 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 spirally wrapped 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 corosion resistant material, such as any suitable rubber cement or adhesive, or an appropriate 2q hydrophobic material, e.g. polyolefins, such as polyethylene, polypropylene, polybutene and copolymers of such olefins.

A centrally disposed core of synthetic polyester fibers around 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 4 0 49 carrying the loads that the steel strands are able to carry. A typical example of 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 spirally wrapped around the core.

The invention i s 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 provides a composite cord reinforcement for 10 a tire comprising a plurality of metal strands spirally wound around a centrally disposed, non-metallic core which has a tensile strength that is substantially equal to the tensile strength of each of the metal strands.

The invention also extends to a tire comprising such a 15 reinforcement.

An embodiment of the invention will now be described 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 of organic, Aramid filaments. An appropriate number of steel strands 7-12 are spirally wrapped around -24 4 Ο 4 S the mu 1tifi1 ament core 6 of Aramid. The steel strands 7-12 are each composed of a desired number of steel filaments or wires 13-16 which are twisted together. The individual steel wires 13-16, in this instance have a diameter of .175 millimeters, and the steel strands 7-12 each have a lay of 10 millimeters (mm) in an S direction.

The steel strands 7-12, in turn, have a lay around the Aramid core 6 of 19 mm. in a Z direction. The Aramid core 6 has a high tensile strength which is substantially equal to that of any one of the individual steel strands 7-12. A multifilament yarn or strand of Aramid, having a 1500 denier, of minimal twist, and treated with an agent for increasing the adhesion between the mu 11ifi1 ament and rubber material in which the steel cord 5 is embedded, was successfully used as a core 6. Two wound^siightly spiralled 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 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 sized. In some instances, it is beneficial to use an Aramid core 6 which is slightly larger than the steel strands 7-12 -34 4 0 4 9 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. The Aramid core 6 should not be too large to severely distort the configuration 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 organic 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 proved unsuccessful The polyester core reduced corrosion of the steel wires, 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 rei nforcements . -44 4 0 4 9 Thus, there has been provided a composite cord reinforcement which utilizes a core that not only helps prevent corrosion of the steel strands of the reinforcement 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 cods 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. The composite cord reinforcement of the invention is useful in passenger tires as well as larger truck and earthmover tires.

As used herein, the term tensile strength is a measure of the cord stress at the time of rupture and is expressed as a force per unit area.

The term Aramid is a trade mark and as used herein indicates a fiber in which the fiber-forming substance is a long chain synthetic aromatic polyamide in which at least percent of the amide linkages are attached directly to two aromatic rings.

Claims

1. A composite cord reinforcement for a tire, comprising a plurality of metal strands spirally wound around a centrally disposed, non-metallic core which has 5 a tensile strength that is substantially equal to the tensile strength of each of the metal strands.

2. The reinforcement of Claim 1, wherein the core is composed of fiber in which the fiber-forming substance is a long chain synthetic aromatic polyamide in which at least 10 85 percent of the amide linkages are attached directly to two aromatic rings.

3. The reinforcement of Claim 1 or 2, wherein the core has a diameter which is equal or greater than the diameter of each of the metal strands. 15

4. The reinforcement of any preceding Claim, wherein the metal strands are of steel, and each strand comprises a plurality of individual steel wires which are spirally wound together.

5. The reinforcement of Claim 4, wherein the individual 20 wires of each strand are twisted together in one direction and the strands are spirally wound around the core in a direction which is opposite to the direction in which the wires are twisted. -64 4 0 4 9

6. · The reinforcement of Claim 5, wherein the core fills the center void created by the spirally wound steel strands.

7. The reinforcement of Claim 6, wherein the core is not so large as to distort the geometry of the cord reinforcement 5 sufficiently to adversely affect the 1oad-carrying characteristics of the reinforcement. θ· A tire having a reinforcement of any preceding claim in combination with other like reinforcements to form at least one layer of reinforcement cords in the tire.

8. 10

9. A composite cord reinforcement for a tire substantially as described with reference to the accompanying drawing and as shown therein.