KR20060023988A - Steel cord for rubber track main cord - Google Patents

Abstract

A steel cord for a rubber track main cord, where core filaments of a core strand is restricted from coming out of a rubber member. This is achieved by causing rubber to penetrate to core filament surfaces of the core strand without reducing a cord breaking load. A core strand (22) of a steel cord (10) is constituted of one core filament (22C) and five sheath filaments (22S) twisted around the core filament (22). Six sheath strands (26) are twisted around the core strand (22). A rubber member is highly penetratable into the core filament (22C) because sufficiently wide gaps are held between the sheath filaments (22S). The structure above realizes the steel cord (10) where the core filament (22C) is restricted from coming out.

Description

Steel cord for main cord of rubber crawler {STEEL CORD FOR RUBBER TRACK MAIN CORD}

The present invention relates to a steel cord for a main cord embedded in a rubber crawler.

Steel cords are often used as reinforcements for endless rubber crawlers. And, in order to increase the load resistance of the steel cord, the steel cord has a structure of 7 × 7 in which the cord cutting load is increased.

As a 7x7 structure, it is a structure which arrange | positioned six sheath strands 86 around one core strand 82 like the steel cord 80 shown in FIG. 5 disclosed by patent document 1, The diameters of the core filament 82C and the sheath filament 82S constituting the core strand 82 and the diameters of the core filament 86C and the sheath filament 86S constituting the sheath strand 86 are all the same. .

However, in the structure shown in FIG. 5, since the clearance gap between the sheath filaments 82S which comprises the core strand 82 is narrow, rubber penetration into the core filament 82C which comprises the core strand 82 is low. For this reason, when a rubber crawler having this steel cord 80 is used for use, the load is repeatedly input. As a result, the core filament 82C constituting the core strand 82 is formed from the end of the steel cord 80 by the rubber crawler. There is a difficulty in protruding to the surface side. Water was infiltrated and propagated from the outside, starting from the filament exposed on the surface, and corrosion fatigue occurred, causing the steel cord to break.

Moreover, the same problem arises also with the steel cord of the structure disclosed by patent documents 2-5.

As a countermeasure, as shown in FIG. 6, the diameter of the core filament 92C of the core strand 92 is made larger than the diameter of the sheath filament 92S of the core strand 92 to suppress the protrusion of the core filament 92C. One steel cord 90 is disclosed in Patent Document 6. In addition, in FIG. 6, the diameter of the core filament 96C of the sheath strand 96 is also larger than the diameter of the sheath filament 96S of the sheath strand 96.

However, with the structure as shown in Fig. 6 disclosed in Patent Document 6, the diameter of the core filament 92C or the core filament 96C becomes thick. For this reason, there exists a problem that the weight of the steel cord 90 itself increases. In addition, since the rigidity of the steel cord 90 is increased, when manufacturing a rubber product using the rubber crawler having the steel cord 90, it is difficult to bend and it is necessary to manufacture the joint so as not to peel off. There was a problem. In addition, the filament wound on the same shape bobbin is used as core filament or sheath filament, and the length wound around the filament diameter is different. There was a problem that the unnecessary cost increases.

Patent Document 1: Japanese Patent Application Laid-Open No. 11-093087

Patent Document 2: Japanese Patent Application Laid-Open No. 06-240590

Patent Document 3: Japanese Patent Application Laid-Open No. 08-027685

Patent Document 4: Japanese Patent Application Laid-Open No. 01-104888

Patent Document 5: Japanese Patent Application Laid-Open No. 09-111679

Patent Document 6: Japanese Patent Application Laid-Open No. 2001-20188

In view of the above, the present invention provides a steel cord in which a plurality of sheath strands are twisted around a core strand, whereby the core strand can be introduced into the core filament surface of the core strand without lowering the cord cutting load. The object of this invention is to provide the steel cord used for the main cord of the rubber crawler which suppressed the core filament from protruding from a rubber member.

The invention according to claim 1 is a steel cord obtained by twisting a plurality of sheath strands around a core strand twisted into two layers composed of a plurality of filaments, wherein the core strands include one or a plurality of core filaments and one or a plurality of core filaments. It consists of five sheath filaments twisted around the core filament, said sheath strand being comprised of one core filament and six sheath filaments twisted around this core filament.

In the case where the number of core filaments constituting the core strands is plural, it is preferable that the core filaments are twisted together from the viewpoint of ease of manufacture and from the viewpoint of strength. In this case, the steel cord may be manufactured by simultaneously supplying the filament constituting the core strand and the sheath filament constituting the sheath strand, or the filament serving as the sheath strand by supplying the core strand prepared in advance. You may manufacture. In the case where the number of core filaments constituting the core strands is plural to be combined, it is preferable that the number of core filaments be one from the viewpoint of productivity since the twisting and kneading step increases by one.

When the number of the sheath filaments constituting the core strand is four or less, bias tends to occur when twisted, and strong decrease tends to occur when a load is applied.

It is also possible to omit the wrap filament.

As described above, in the invention according to claim 1, the number of sheath filaments constituting the core strand is reduced by one compared to the prior art, so that the rubber is allowed to penetrate the core filament surface of the core strand without reducing the cord cutting load. It is possible to realize a steel cord. Thus, a steel cord for reinforcing rubber products in which protrusion of the core filament is suppressed is realized.

Invention of Claim 2 has the diameter (dk) of the core part which comprises the said core strand, and the diameter (ds) of the sheath filament which comprises the said core strand satisfy | fills the relationship of 1.1xds≥dk> ds. do.

The core portion is composed of one or a plurality of core filaments. When the core portion is composed of a plurality of core filaments, the diameter dk of the core portion is equal to the diameter of the projection trajectory in the cord longitudinal direction.

By satisfying the relationship of dk? ds, the rubber easily penetrates into the gap between the sheath filaments constituting the core strands, and thus the rubber can be sufficiently reached to the core portion. In addition, by satisfying the relationship of 1.1 x ds ≥ dk, it is possible to prevent the occurrence of bias when the core strand is twisted or a strong decrease when the load is applied.

Invention of Claim 3 made the twisting direction of the sheath filament which comprises the said core strand and the twisting direction of the sheath filament which comprises the said sheath strand reverse each other, It is characterized by the above-mentioned.

Thereby, since the contact area of a core strand and a sheath strand can be reduced, rubber permeability to the core strand surface can be improved.

BRIEF DESCRIPTION OF THE DRAWINGS The side view at the time of manufacturing the rubber crawler which used the steel cord of a 1st form as a main cord.

FIG. 2 is a side sectional view of the rubber crawler obtained in the process of FIG.

3 is a cross-sectional view showing the configuration of a steel cord of the first aspect.

4 is a cross-sectional view showing the configuration of a steel cord of the second aspect.

Fig. 5 is a sectional view showing the structure of a conventional steel cord.

Fig. 6 is a sectional view showing the structure of a conventional steel cord.

EMBODIMENT OF THE INVENTION Hereinafter, embodiment is described and embodiment of this invention is described.

[First form]

First, the first aspect will be described. As shown in Figs. 1 to 3, the steel cord 10 according to the first aspect is embedded in the longitudinal direction of the rubber crawler 16 (see Figs. 1 and 2) and used as a reinforcing member (main cord). Steel cord. The steel cord 10 is composed of one core strand 22 and six sheath strands 26 twisted around the core strand 22. The rubber crawler 16 is initially formed in a stepped belt shape protruding both ends of the steel cord 10, and filled with a new rubber material 16a in a state in which both ends of the steel cord 10 are overlapped to form an endless shape. By vulcanization. In addition, the code | symbol 16b is a core embed | buried in rubber | gum simultaneously, and 16c is a lug formed in the outer peripheral side.

As shown in Fig. 3, the core strand 22 is composed of one core filament 22C and five sheath filaments 22S twisted around the core filament 22C. The sheath strand 26 is composed of one core filament 26C and six sheath filaments 26S twisted around the core filament 26C.

As described above, in this embodiment, the sheath filaments 22S constituting the core strands 22 are five, one smaller than the conventional six, so that the sheath filaments 22S constituting the core strands 22 are separated from each other. The gap is sufficiently secured. Therefore, when the rubber member is intruded from the surroundings into the steel cord 10 in manufacturing the rubber crawler 16, the rubber member sufficiently invades between the sheath filaments 22S constituting the core strand 22. The amount that the rubber member reaches to the surface of the core filament 22C constituting the core strand 22 can be a sufficient amount. Therefore, even if the rubber crawler 16 which embeds this steel cord 10 as a main cord is used, the protrusion of the core filament 22C can be suppressed.

[Second form]

Next, a second aspect will be described. In 2nd aspect, the same code | symbol is attached | subjected to the same component as 1st aspect, and the description is abbreviate | omitted.

As shown in Fig. 4, the steel cord 30 according to the second aspect is composed of one core strand 32 and six sheath strands 26 twisted around the core strand 32 and joined together.

The core portion 32C of the core strand 32 is composed of three core filaments 32C1 to C3 twisted together. As a result, the surface area of the core portion 32C can be increased, and the rubber penetration into the core portion 32C can be further improved. In this case, the diameter dk (see FIG. 4) of the core portion 32C is the same as the diameter of the projection trajectory in the cord length direction of the core portion 32.

As mentioned above, although embodiment of this invention was described using embodiment as an example, these embodiment is an example and can be variously changed and implemented within the range which does not deviate from the summary. It goes without saying that the scope of the present invention is not limited to the above embodiment.

Experimental Example

Steel cord 10 (first embodiment) described in the first aspect, steel cord 30 (second embodiment) described in the second aspect, a steel cord composed of one core strand and four sheath strands (Comparative Example) A rubber crawler using a conventional steel cord (conventional example) as a steel cord for reinforcement was produced and subjected to a durability test. As test conditions, it ran for 200 hours in the rubber crawler. Core strand structure, filament diameter (core filament diameter (dc) of the core strand, sheath filament (ds) of the core strand, core diameter of the core portion of the core strand) of the first, second, comparative and conventional examples ] And test results are shown in Table 1.

TABLE 1

First embodiment Second embodiment Comparative example Conventional example Core strand structure 1 + 5 3 + 5 1 + 4 1 + 6 Core Filament Diameter (dc) of Core Strand (mm) 0.34 0.16 0.34 0.34 Sheath filament diameter (ds) of core strand (mm) 0.34 0.34 0.34 0.34 Core Diameter of Core Strand (dk) (mm) 0.34 0.34 0.34 0.34 Number of protrusions of cores in core strands 0 0 0 7 Strong utilization rate (%) 90 88 72 90

The evaluation of the durability test was made by the number of protrusions of the core filament from the surface or the back of the rubber crawler and the strong utilization rate.

Here, the strong utilization rate U can be calculated | required by the following formula, and it shows that it is so good that a numerical value is large.

U = (break strength of steel cord) / (total breaking strength of filaments used)

As is apparent from Table 1, in the first and second embodiments, the number of protrusions of the core filament can be reduced without lowering the strong utilization rate, that is, without lowering the cutting load.

In the case of the comparative example, it was good in terms of the number of protrusions of the core filament, but the strong utilization rate was lowered. It is considered that the number of the sheath filaments constituting the core strand is excessively reduced.

In the case of the above conventional example, the number of protrusions of the core filament was large, which resulted in poor evaluation. This is considered to be because the gap between the sheath filaments constituting the core strand is too narrow and the rubber has not sufficiently reached the core filament constituting the core strand.

Since the present invention has the above configuration, in a steel cord obtained by twisting a plurality of sheath strands around a core strand, the core strand can be made to intrude into the core filament surface of the core strand without lowering the cord cutting load. The steel cord for the main cord of the rubber crawler which suppressed the core filament from protruding from the rubber member can be realized.

Claims (3)

It is a steel cord which twisted several sheath strands together around the core strand twisted by two layers which consist of several filaments, The core strand is one or a plurality of core filaments, Composed of five sheath filaments twisted around one or more core filaments, And said sheath strand is composed of one core filament and six sheath filaments twisted around said core filament. The diameter (dk) of the core portion constituting the core strand, and the diameter (ds) of the sheath filament constituting the core strand, 1.1 × ds ≥ dk ≥ ds Steel cord for the main cord of the rubber crawler, characterized in that to satisfy the relationship. The main cord steel of a rubber crawler according to claim 1 or 2, wherein the twisting direction of the sheath filaments constituting the core strand and the twisting direction of the sheath filaments constituting the sheath strand are reversed to each other. code.

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