JPS6080910A - Steel cord for tire - Google Patents

Abstract

PURPOSE:To improve the adhesion performance with rubber by forming a side strand so as not to have the joint part constituted of broken edges, in a steel cored in a multilayer structure which is formed by covering the periphery of a core strand by the side strand. CONSTITUTION:A steel cord 1 is constituted of, for example, a core strand 3 constituted of three filaments 2 and a side strand 4 constituted of three filaments twisted around the core strand 3, and the broken filaments 2 are used as the core strand 3, and the broken edge parts of the filaments 2 are twisted each other to form a joint part J. In this case, the side strand 4 which has not joint part is arranged around the joint part J of the core strand 3 so as to cover the whole, and the point part J is prevented from being exposed to the outside of the side strand 4. Thus, the adhesion performance with rubber in the case when the joint part J is buried into rubber can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a steel cord for a tire, which has improved adhesive strength to rubber at a broken end of the steel cord, not including a welded portion.

Generally, during the manufacturing process of steel cords, accidents often occur in which the filaments constituting the steel cords are broken. In this case, the entire steel cord including the broken end is cut at a position corresponding to the broken end, and the cut ends are brought into contact with each other and welded (1). Each filament that makes up the steel cord is usually plated with brass to improve adhesion to the rubber, but approximately 10 m of the welded joint area
In the range of m, the composition of brass plating changes due to heat,
Adhesion to rubber is reduced. When such a steel cord is used as a reinforcing material for a tire, the fatigue resistance decreases to about 1/100, resulting in case rupture. The present invention solves this problem by configuring the outer strands of the steel cord, that is, the side strands, to have no joints at the broken ends, thereby improving the adhesion to rubber. The present invention will be explained in detail below based on examples.

1 to 4 are schematic diagrams of a 7×3 twisted structure steel cord of the present invention. In Figure 1, the steel cord (1) is composed of a core strand (3) consisting of three filaments (2) and six side strands (4) consisting of three filaments twisted around it. has been done. The filaments or strands broken here are used as (2) core strands, and the broken ends of the filaments are twisted together to form a joint (J). A side strand (4) without a joint is arranged around the joint (J) of the core strand (3) so as to cover the whole, and the joint (J) is exposed to the outside of the side strand. I try not to. The joint part (J
) is exposed on the outside of the side strand, and when it is buried in rubber, the joint (J) becomes the starting point of stress concentration, which is combined with poor adhesion to the rubber at the broken end. , peeling from the rubber occurs.

FIG. 2 shows another embodiment of the invention, in which the core strand (
The three broken ends of the filament 5) are connected to other filaments at mutually shifted positions to form three joints (Jl, J2, J3). By shifting the positions of the joints in this way, it is possible to reduce the increase in the strand diameter due to the joining of filaments and improve the uniformity of the rigidity of the cord.

FIG. 3 shows another embodiment of the invention, in which the core strand (3) (5) has a welded joint (JM).

FIG. 4 shows yet another embodiment in which the core strands (5) are joined by twisting the filaments to each other with the filaments having different breaking positions. Both of these methods have the advantage that the diameter of the core strand increases little at the joint.

As an application example of the present invention, when a filament of a side strand breaks during the steel cord manufacturing process, the broken end of the filament is placed inside the cord, that is, on the core strand side, and the broken end is joined. It is also possible to twist back to the side strands.

Although the present invention has been described as a steel cord with a two-layer structure consisting of a core strand and side strands, it can be similarly applied to a steel cord with a three-layer structure, for example, a 3+9+15 twist structure.

Example 7 The steel cord shown in Figure 5 (Comparative Example 1) with a twisted structure of 7x4x0.175 and welded at the cut end of the cord was connected to the four filaments of the core strand at the joining position as shown in Figure 2 (4). Steel cords (Example 1) bonded so as to be offset from each other were embedded in rubber and vulcanized and bonded. Then, peel the steel cord from the rubber,
The surface condition of the rubber after peeling is shown in a photograph in FIG. From the figure, it can be seen that the rubber surface corresponding to the joint is smooth and the adhesion is poor.

On the other hand, it was observed that the surface condition of the rubber after peeling in the example was rough, similar to the non-joint portion in FIG. 6, and the adhesion condition was good.

[Brief explanation of drawings]

1 to 4 are schematic diagrams of the steel cord of the present invention, FIG. 5 is a photograph of the external appearance of a steel cord of a comparative example, and FIG. 6 is a photograph of the rubber surface state after the steel cord has been peeled off. 1... Steel cord 2...
・・・・・・・・・Filament 3, Core strand 4・・・・・・・・・Side strand (5) Fig. 1 Fig. 2 Fig. 3 Fig. 4 Figure 5 Figure 6 Kazuo Wakasugi, Commissioner of the Japan Patent Office, Patent Application No. 190549, filed in 1982, 2, Name of the invention Steel cord for tires 3, Relationship to the person making the amendment Case Patent applicant address Tsutsui-cho, Chuo-ku, Kobe City 1-1-1 1981
January 11, 1980 (January 31, 1980) 6, Subject of amendment 7, Contents of amendment (1) Page 4 of the specification, line 19, ``Welded steel cord shown in Figure 5'' was replaced with ``Welded steel cord shown in Figure 5.'' Corrected to "Steel Code". (2) Page 5, lines 4 to 7 of the specification: “The rubber surface condition after peeling is shown as a photograph in Fig. 6. The figure shows that the rubber surface corresponding to the joint is smooth and the joint condition is poor. The statement "Approved" has been corrected to "When the surface condition of the rubber was observed after peeling, it was found that the surface of the rubber corresponding to the joint was smooth and the joint condition was poor." (3) In the specification, page 5, lines 8 to 9, "The surface condition of the rubber is in the areas that are not the joints in Figure 6" is corrected to ``The surface condition of the rubber is in the areas that are not the joints'' (4) Lines 12 to 15 of page 5 of the specification are deleted and the following items are added. "Figures 1 to 4 show schematic diagrams of the steel cord of the present invention." (5) Figures 5 and 6 are deleted from the drawings.

Claims (1)

[Claims] (1) A steel cord with a multilayer structure consisting of a core strand made of one or more filaments twisted together, and a side strand made of one or more filaments twisted together surrounding the core strand, the side strands comprising: The steel cord for a tire as described above, characterized in that it does not have a joint at a broken end.