JP4353523B2 - Steel cord for rubber reinforcement - Google Patents

Description

  The present invention relates to a steel cord for reinforcing rubber, and more particularly to a steel cord for reinforcing rubber capable of improving rubber permeability.

  In general, measures are taken on steel cords for reinforcing rubber products to prevent corrosion due to moisture in the rubber. In order to protect the steel cord from corrosion, the steel wire is plated with zinc or the like, and the structure of the cord is made easy for rubber to penetrate between the strands, and many proposals regarding the cord structure have been made.

  Among these, a multi-strand structure comprising a core strand and a plurality of side strands surrounding the core strand is adopted as a reinforcing cord for a conveyor belt used particularly under high tension, and each strand is composed of one or more central elements. There is a proposal to improve the penetration of rubber and increase the fatigue resistance of a cord by forming the wire and two or more layers of wires surrounding the wire (for example, see Patent Document 1).

However, in these proposals, since the core strand has a single twist structure, the rubber penetration effect cannot be obtained sufficiently, and in addition, the number of wire diameters constituting the cord increases, resulting in a decrease in steel cord productivity. There was a problem to do.
JP-A-6-240590

  An object of the present invention is to solve the above-described problems, and to provide a steel cord for rubber reinforcement capable of improving rubber permeability.

To achieve the above object, a steel cord for reinforcing rubber according to the present invention is used for reinforcing a rubber product having a multi-strand structure in which a plurality of side strands are twisted around a core strand. In the above, the core strand has a double twist structure having an N × (1 + 6) structure (where N = 2 to 4) , the side strand has a three-layer twist (1 + 6 + 12) structure, While having a M × (1 + 6 + 12) structure twisted around the periphery (where M = 5 to 7), the ratio D0 / D1 between the diameter D0 of the core strand and the diameter D1 of the side strand is 1.05-1. This is summarized in 35.

As described above, the steel cord for reinforcing rubber according to the present invention is a steel cord comprising a core strand and a side strand, and the core strand is a double twist structure having an N × (1 + 6) structure (where N = 2 to 4). And the side strand has a three-layer twisted (1 + 6 + 12) structure, and the M strand is twisted around the core strand to form an M × (1 + 6 + 12) structure (where M = 5 to 7), and the diameter of the core strand. Since the ratio D0 / D1 between D0 and the side strand diameter D1 is set to 1.05 to 1.35, sufficient penetration of rubber into the steel cord can be obtained.

  Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a cross-sectional view showing an example of a steel cord for reinforcing rubber according to the present invention.

In FIG. 1, a steel cord for rubber reinforcement (hereinafter referred to as a steel cord) 1 is composed of a core strand 2 located on the center side and M side strands 3 (six in the figure) twisted around its outer periphery. The entire structure is a so-called multi-strand structure. The core strand 2 on the center side has a double twisted structure in which N (three in the figure) center strands 2a (1 + 6 structure) are twisted together. The side strand 3 on the outer peripheral side has a plurality of strands twisted in layers. 3-layer-twisted structure (1 + 6 + 12 structure) Tona is, the M present (six in the drawing) is that have been twisted around the core strand 2. The ratio D0 / D1 between the diameter D0 of the central core strand 2 and the diameter D1 of the outer side strand 3 is adjusted to 1.05 to 1.35.

  Thus, while making the core strand 2 into a double twisted structure, the ratio D0 / D1 between the diameter D0 of the core strand 2 and the diameter D1 of the outer side strand 3 is set to 1.05 to 1.35. The penetration of rubber into the cord 1 can be improved. If D0 / D1 is less than 1.05, the penetration of rubber into the cord becomes insufficient, and if it exceeds 1.35, the strength of the cord cannot be obtained sufficiently.

  Moreover, the number of the strand diameters of the steel monofilament which comprises the whole code | cord | chord can be decreased by making the core strand 2 into a double twist structure. That is, among the strands A, B of the central strand 2a and the strands C, D, E of the side strand 3, the strands D, E on the outer layer side of the strands C, D, E of the side strand 3 This is because strands having the same diameter as the strands A and B of 2a can be used. Therefore, at least three types of wire of the steel cord 1 are sufficient.

On the other hand, in the conventional steel cord 51 having substantially the same strength as the steel cord 1 of FIG. 1, the core strand 52 and the side strand 53 are each composed of 7 × (1 + 6 + 12) as shown in FIG. Since it has a three-layer twisted structure, the outer layers of the strands S, T, U of the side strand 53 out of the strands P, Q, R of the core strand 52 and the strands S, T, U of the side strand 53 Only the strands having the same diameter as the strands Q and R of the core strand 52 can be used for the strands T and U on the side. Therefore, at least five types of strands of the steel cord 1 are required. Note that the tensile strength of the steel cord 1 in FIG. 1 and the steel cord 51 in FIG. 2 is the same when the cord diameter (7 mm) and the core strand diameter / side strand diameter (1.2) are the same. 1 is 100, whereas the steel cord 51 of FIG.

The steel cord 1 of the present invention is used for reinforcing a rubber product used under high tension, and a product to which the steel cord 1 is applied is not particularly limited, but is preferably applied for reinforcing a conveyor belt used under high tension. Is done. When used as reinforcement for conveyor belts, as shown in FIG. 1, the structure of the steel cord 1 3 × (1 + 6) + 6 better to × (1 + 6 + 12) .

As described above, in the steel cord 1 of the present invention, the core strand 2 is formed into a double twist structure having an N × (1 + 6) structure (where N = 2 to 4) , and the side strand 3 is twisted in three layers (1 + 6 + 12). The structure is M × (1 + 6 + 12) structure in which M pieces are twisted around the core strand (where M = 5 to 7), and the ratio D0 between the diameter D0 of the core strand and the diameter D1 of the side strand / D1 is set to 1.05 to 1.35, whereby rubber permeation into the steel cord 1 can be improved. Furthermore, since the number of wire diameters constituting the cord can be reduced, it is advantageous from the viewpoint of the productivity of the cord.

  The cord diameter and the core strand diameter / side strand diameter of the steel cord are different as shown in Table 1, and the cord structure is as shown in FIG. 2, and the cord structure is as shown in FIG. The inventive cords (corresponding to Examples 1 to 4) and comparative cords (corresponding to Comparative Examples 1 and 2) were produced. Each of these cords is embedded in rubber, vulcanized in a mold under the same conditions, and the upper, lower, left and right sides of the cord are covered with 2 mm thick rubber, and a conventional test piece having a square cross section and a length of 460 mm (conventional) Examples 1 and 2), inventive test pieces (Examples 1 to 4) and comparative test pieces (Comparative Examples 1 and 2).

  With respect to the above eight types of test pieces, rubber permeability was measured by the following method, and the results are shown in Table 1. Table 1 also shows the types of strands of steel monofilament (number of strand diameters) constituting the steel cord in each test piece and the cord strength based on the index of Example 2 being 100.

[Rubber permeability]
In accordance with the “air permeability test method” according to the Australian standard (AS-1333), 100 kPa of air pressure is press-fitted from one end in the longitudinal direction of the test piece, and the air pressure transmitted to the other end is 5 kPa. The time (seconds) to become was measured. The longer this time, the better the air permeability and the better the rubber permeability for the steel cord.

  From Table 1, it can be seen that the cord of the present invention is superior in rubber permeability without lowering the cord strength as compared with the conventional cord and the comparative cord. It can also be seen that the number of wire diameters constituting the cord is smaller in the cord of the present invention than in the cord of the related art.

It is sectional drawing which shows an example of the steel cord for rubber reinforcement of this invention. It is sectional drawing which shows the conventional steel cord for rubber reinforcement.

Explanation of symbols

1, 51 Steel cord 2, 52 Core strand 2a Central strand 3, 53 Side strand

Claims (3)

In the steel cord for reinforcing rubber used for reinforcing a rubber product having a multi-strand structure in which a plurality of side strands are twisted around the core strand,
The core strand has a double twist structure having an N × (1 + 6) structure (where N = 2 to 4) , the side strand has a three-layer twist (1 + 6 + 12) structure, and the M strands are arranged around the core strand. The twisted M × (1 + 6 + 12) structure (where M = 5 to 7) and the ratio D0 / D1 of the core strand diameter D0 and the side strand diameter D1 to 1.05 to 1.35 Steel cord for reinforcing rubber. The steel cord for reinforcing rubber according to claim 1, wherein the strands constituting the core strand and the side strand are made of steel monofilaments having three kinds of diameters. The steel cord for reinforcing rubber according to claim 1 or 2, which is used for reinforcing a conveyor belt.

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