JPS644879Y2 - - Google Patents

Description

[Detailed explanation of the idea]

INDUSTRIAL APPLICATION FIELD The present invention relates to a steel cord used as a reinforcing material for tires, belts, etc. In particular, it is a steel cord with an improved welded part of a loosely twisted steel cord. BACKGROUND ART Generally, this type of steel cord is constructed by twisting a plurality of strands together. A plurality of these steel cords are lined up in parallel and covered with a rubber material, and are used as reinforcing materials for tires, belts, etc. The steel cord used in this manner is usually wound around 5,000 m to 10,000 m on a reel. For this reason, if a wire breaks during manufacturing or if the length of the wire is less than the length of the product, the ends are welded and used to match the length of the product. For loosely twisted steel cords, as shown in Figure 2, both steel cords are butted against each other and welded under pressure while maintaining the loosely twisted shape. Problems that the invention aims to solve: In the conventional welding described above, it is difficult to weld multiple wires at the same time and evenly, and there are many welding failures such as not being able to join only one wire or one or two wires. Even if welding is successful, the quality of the steel cord after welding is poor, so the number of welds over the entire length and the number of reels including welds are limited for each lot so that they do not become too large. The present invention eliminates the above-mentioned drawbacks and provides a steel cord having a welded structure that can be easily welded and prevents deterioration of the quality of the steel cord due to welding. Means for solving the problem In order to achieve the above purpose, the ends of the loosely twisted steel cord are not twisted loosely,
It is designed to be welded in a tight state.
In a steel cord that is constructed by loosely twisting multiple strands of wire and has at least one welded part in the longitudinal direction, a twisted structure part with a tightness of at least 3 mm is provided before and after each of the welded parts. It is characterized by steel cord. Effect Since the present invention has the above configuration, the strand 1 of the welded part
Since multiple books are joined together, rather than individual books being welded separately, failures in welding operations are almost eliminated. In addition, if welding is performed with loosely twisted wires, the lengths tend to vary between each strand near the weld, but by providing a tightly twisted part before and after the weld, the length between each strand near the weld can be increased. The variation in length is completely eliminated. Therefore, the mechanical quality of the weld is significantly improved compared to the quality of conventional welds. In addition, in the annealing performed after pressure welding, the heat treatment is performed more appropriately than in the conventional case, and the subsequent metal structure of the welded part becomes uniform and normal, making it possible to eliminate stress and strain uniformly. can. In addition, the diameter of the weld is usually larger than the diameter of the cord due to burrs in the weld, but in the weld of this invention, the loose twist is made into a tight twist only at the weld, so the weld is slightly twisted. Even if the diameter created by the burrs becomes larger, it is smaller than the diameter of the original loosely twisted steel cord, so there is no need to perform the deburring process very precisely. In addition, the area occupied by the tight twisted structure in this welded part requires a distance of at least 3 mm before and after the welded part.If the distance is less than 3 mm, untwisting will occur after welding, the twist will become loose, and the distance from the welded part will be It is easy for wire breakage to occur, and its mechanical strength is also poor. Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a front view of the main part of a welded part in a steel cord showing an embodiment of the present invention, in which one end of each steel cord 1 having a loosely twisted structure (1×5×0.25 open structure) is twisted and cured. The strands are tightened using a tool to form a tight twisted structure 2, and then welded by butt welding to construct the steel cord of the present invention. 3 is a burr caused by welding. Here, the length of the tightly twisted part after welding before and after the weld is T ₁ ≒ T ₂ ≒ 15 mm, the cord diameter of the loosely twisted part 1 is 0.83 mm, and the cord diameter of the tightly twisted part 2 is It is 0.69mm〓. A steel cord with the welded part of the present invention and a steel cord with the conventional welded part shown in Fig. 2 are used.
We made 100 samples and conducted tensile tests and fatigue tests for comparison. The results are shown below.

[Table] Here, welding defects refer to
If all five strands were welded, it was judged as a pass, and if even one of the strands was not welded or the strands were broken, it was judged as a welding failure. The fatigue test was conducted using a Hay-Robertson type fatigue testing machine.
Sample length = 140mm, distance between chucks 100mm,
Chuck angle θ = 85°, arc R = 40mm, rotation speed
The condition is 1800rpm. Note that the lengths of the tightly twisted portions T ₁ and T ₂ are approximately
Although the thickness was set at 15 mm, at least 3 mm or more is required, and a range of 7 mm to 20 mm is practically preferable. Further, the twist pitch of this tightly twisted portion may be the same as that of other portions, or may be smaller than that of other portions. Considering workability, it is easier to tighten the cord if the pitch is short. As mentioned above, in this example, the steel cord can be completely welded, and the tensile strength of the welded part is approximately 30% higher than that of the conventional welded part.
60% of the tensile strength of the steel cord section without welding
, and fatigue was about 55% higher than before. Although this invention has been described for steel cords with a 1×5 structure, other steel cords such as 1×4, 2+7, 3+6,
The structure of the present invention is also effective for steel cords having a structure such as 4×4. Further, the present invention can also be applied to a loosely twisted steel cord in which tightened portions are provided at regular intervals in the longitudinal direction. Effects of the invention As described above, according to the invention, in the welded part of loosely twisted steel cords, by creating a tightly twisted structure at the front and back of the welded part, the welding work is made easier and more reliable. It is a device that has practical effects, such as being able to weld, greatly improving mechanical strength such as tensile strength and fatigue resistance, and simplifying the treatment of burrs and the like that occur during welding.

[Brief explanation of drawings]

FIG. 1 is a front view of the main part of a steel cord showing an embodiment of the present invention, and FIG. 2 is a front view of the main part of a conventional steel cord. 1...Lightly twisted structure part, 2...Tightly twisted structure part, 3...Flash.

Claims (1)

[Scope of utility model registration request] It is constructed by loosely twisting multiple strands of wire,
Further, a steel cord having at least one welded portion in the longitudinal direction, wherein a tightly twisted structure portion of at least 3 mm or more is provided at the front and rear of the welded portion.