JPS6010154B2 - Cable with protective layer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a cable with a protective layer used in structures such as cable-stayed bridges.

Focusing on cable-stayed bridges as structures using cables made of steel wires, galvanized steel wires, PC steel wires, steel stranded wires, and the like are used as the cables.

When such a structure is required to have long-term durability of, for example, 100 years, corrosion protection of the cable becomes an important issue. Conventional corrosion prevention methods generally include applying an anticorrosive paint around the cable 1 and coating it with weather-resistant plastic as a protective layer 2, or coating the cable with a seamless polyethylene pipe, as shown in Figure 1. A method of preventing corrosion is to fill the space between the cable and the polyethylene pipe with resin or cement mortar to insulate the cable from rainwater and harmful substances.

The protective layer of this cable is made of plastic, specifically polyethylene (usually carbon black is added to improve weather resistance), FRP, or the like.

However, the anti-corrosion life of cables that have been provided with a protective layer using the conventional method is short, and after 10 to 30 steps, the cable must be re-corrosion-protected, which increases the cost and risk of the work. Obstacles to traffic were a serious problem.

It has been reported that polyethylene as a material has practically sufficient film resistance even after being exposed outdoors for a long time, and is generally one of the materials with excellent weather resistance.

However, if the surface deteriorates and becomes brittle, microscopic cracks will occur due to tension or impact, and the cracks will propagate throughout the structure due to external forces, allowing rainwater to enter the interior through these cracks. In addition, there are 5 facts regarding the weather resistance of polyethylene.
There were no achievements above 0 King. In view of the above points, the present invention
With the aim of significantly extending the anti-corrosion lifespan of cables with a protective layer, as a result of extensive research, we have created a multi-layered structure in which a protective layer made of seamless rubber or plastic pipes is placed around the cable without adhering to each other. As a result, even if the outermost layer deteriorates and minute cracks occur on the surface, the cracks will remain in the outermost layer and will not propagate to the layers below.
The present invention was achieved by discovering that it maintains excellent weather resistance over a long period of time.

The material for the protective layer may be polyethylene, vinyl chloride, plastic such as nylon, or chloroprene,
Rubbers such as ethylene propylene rubber and butyl rubber may also be used. Hereinafter, an embodiment of the present invention will be described with reference to FIG.

In FIG. 2, 11 is a cable made of steel wire, and 12 is a protective layer.

The protective layer has a multilayer laminated structure of two or more layers that are not adhered to each other, and in the illustrated embodiment, there are two inner and outer layers 12a and 12b.
Each layer 12a, 12b is formed of a polyethylene pipe. This protective layer 12 is used for the cable 11
The filler layer 14 is provided around the filler layer 14 directly or via a filler layer 14. Each layer 12a, 12 of the polyethylene pipe protective layer 12
Shape so that the space between b is not bonded by heat fusion during extrusion processing.

The specific method is not particularly specified, but for example, a separator such as a releasable table is wrapped between the layers, or a releasable paint such as silicone oil resin is applied, and each layer 12a, 12b is made of polyethylene. They can be formed in such a way that they are difficult to adhere to each other. In particular, if a reinforcing separator layer 13 made of a table made of cotton cloth, synthetic fiber cloth, stainless steel, etc. is provided between each layer 12b, the filler material can be injected between the cable 11 and the protective layer 12. At this time, the separator layer 13 cooperates with the layers 12a and 12b of the protective layer 12 to resist internal pressure, thereby providing a pressure-resistant reinforcing effect. In the above embodiment, the protective layer 12 has two layers 12a and 12b, but it may have three or more layers, and even in this case, it is preferable to interpose a separator between each layer.

By creating a multilayered structure in which the rubber or plastic protective layers provided on the outside of the cable are not bonded to each other, the service life can be extended.

For example, in the case of two layers, the life of the inner layer continues after the life of the outer layer due to exposure has ended, so the weather resistance life can be maintained approximately twice as long as that of a single layer. The effect of extending the life when the protective layer has a multilayered structure was confirmed through the following experiment. In this experiment, two sheets of high-density polyethylene (added with 1% carbon black) with a 4-side thickness (sample The remaining percentage of tensile elongation of each sample sheet was measured after exposing the two-layer sheet (sample ■) in an accelerated exposure tester using a carbon arc, and the results are shown in FIG.

Here, the carbon arc accelerated exposure test is intended to artificially examine the effects of ultraviolet rays in sunlight in a short period of time. In other words, it is said that the deterioration of polyethylene in nature is mainly caused by polymer destruction due to ultraviolet rays, and by accelerating the deterioration using carbon arc as an artificial light source, it is possible to investigate the final state of deterioration of polyethylene. can. Twenty feeding hours of carbon arc exposure is considered equivalent to approximately one year of solar exposure. Also,
The residual elongation rate is given by the following formula. {
Remaining elongation rate (%) = 1 (initial elongation) - (elongation after exposure for a certain period of time)}XI.

〇 (Initial elongation) In the graph in Figure 3, the machine axis represents the irradiation time using the accelerated exposure tester (weather meter), the vertical axis represents the elongation remaining rate, curve A represents the test results for the sample ■, and curve B , is the test result for a sheet with a thickness of 2 sails on the side facing the carbon arc, curve B.
2 shows the test results for a sheet of 2 skin thickness on the side opposite to the carbon arc of sample (2).

As is clear from this graph, according to sample ■, it takes approximately 300 calm hours for the remaining elongation to reach 50%.
In the case of sample (2) shown by curve &, the time required for the remaining elongation to reach 50% is approximately 620 hours, which is approximately twice the life. As is clear from the above experiments, the present invention has a multilayer laminated structure in which the protective layers are not bonded to each other.
The weather resistance life is approximately several times longer than that of a single layer, and it maintains excellent weather resistance for many years, so its practical value is extremely large.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of a conventional cable with a single protective layer provided on the cable, Figure 2 is a cross-sectional view of an embodiment of the cable with multiple protective layers of the present invention, and Figure 3 is a cross-sectional view of a cable with a single layer and two layers. 1 is a graph showing the test results of an accelerated exposure test of a layered polyethylene sheet. 11... Cable, 12... Protective layer, 12a, 12
b...Inner and outer layers. Figure 1 Figure 2 Figure 3

Claims (1)

[Scope of Claims] 1. A cable with a protective layer in which a protective layer made of rubber or plastic is provided on a cable made of steel wire either directly or through a filler layer, and two cables in which this protective layer is not bonded to each other. A cable with a protective layer characterized by having the multilayer laminated structure as described above. 2. The cable with a protective layer according to claim 1, characterized in that a reinforcing separator layer is interposed between the protective layers.