JPH0142083Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a self-supporting overhead optical cable using a so-called non-metallic optical cable that does not use any metal as a cable component.

As is well known, since an optical fiber is made of a dielectric material, it has the characteristic that it does not receive any electromagnetic induction from a power line. For this reason, in recent years,
Non-metallic optical cables, which do not use any metal as cable components, are installed alongside power lines and are being used in considerable numbers as practical circuits.

FIG. 1 shows a conventional non-metallic optical cable. In the figure, an optical fiber core 11 is twisted together with a plastic string 12 as a cable component, for example, around a tension member 13 made of FRP (glass fiber reinforced plastic) rod or Kevlar rod (trade name). A cushioning material 14 made of, for example, plastic yarn is wrapped around the optical fiber core 11 to protect it from external pressure. Further, a plastic tape 15 is wrapped around the cushioning material 14, and a jacket 16 of polyethylene or the like is provided around the tape 15. A non-metallic optical cable having such a structure does not receive any electromagnetic induction from the metal body, unlike, for example, an optical cable that uses a metal body such as a steel wire for the tension member. Therefore, this optical cable has advantages such as high safety during maintenance and inspection, and easy installation since grounding of the induced current is not required.

Now, when using the above-mentioned non-metallic optical cable as an overhead cable, the conventional hanger hanging method can be considered, but since both the hanging wire and the hanger are metal bodies, it not only impairs the characteristics of the non-metallic optical cable, but also You will be subject to location restrictions. Therefore, like conventional self-supporting overhead cables, high tension is applied at all times, and the non-wire cables shown in Figures 2 to 4 are designed to take into consideration the fact that the tension increases due to wind, snow accumulation, and temperature. Metallic self-supporting overhead optical cables are considered. Furthermore, the second
Identical parts in the figures through FIG. 4 are given the same reference numerals.

Figure 2 shows non-metallic optical cable core 20.
By arranging suspension wires 21 made of non-metallic rods such as FRP rods or Kevlar rods having a high Young's modulus in parallel, and integrally covering their outer peripheries with a plastic jacket 23 through the neck portion 22, the suspension wires can be 21 to support the cable core 20.

In addition, FIG. 3 shows that a non-metallic optical cable core 20 and a suspension wire 21 made of a non-metallic rod are each covered with individual plastic sheaths 24 and 25, and the optical cable is placed around the coated suspension wire 27 at a predetermined pitch. It has a configuration in which 26 windings are wound.

Furthermore, FIG. 4, like FIG. 3, shows an optical cable 2 covered with separate plastic jackets 24, 25.
6 and a hanging wire 27 are arranged in parallel, and the optical cable 26 is supported on the hanging wire 27 by winding one or more bind wires 28 made of plastic-coated Kevlar rods or high-tensile fibers around the outer peripheral surface of the wire. That is.

However, the above-described overhead optical cable also has the following problems.

That is, in general, the Young's modulus of FRP rod or Kevlar rod is about 5000 Kg/mm ² and about 7000, respectively.
Kg/mm ² , which is 1/4 to 1/3 smaller than the Young's modulus of steel wire normally used for suspension wires, which is about 20,000 Kg/mm ² . Furthermore, it is well known that when an excessive tension is applied to an optical fiber for a long period of time, it causes static fatigue and eventually breaks. For this reason, the allowable tension for optical cables is stipulated so that the elongation of the optical cable is within 0.2% (a tension that guarantees the lifespan of the optical fiber for several decades or more).
Therefore, the allowable tension of an optical cable using non-metallic rods such as FRP rods or Kevlar rods is defined as 0.2% of the elongation of the optical cable, and the same installation conditions (tension,
1.7 to 1.7 compared to steel wire
It is necessary to use a non-metallic rod with an outer diameter that is more than twice that, which not only increases the cable's outer diameter, but also increases the wind pressure load, deteriorates the flexibility of the cable, and increases the cable's flexibility.
This causes various problems such as rising prices.

This idea was devised based on the above circumstances, and its purpose was to create a cable with almost the same outer diameter as conventional optical cables using metal suspended wires, yet with sufficient tolerance to withstand long-term use. The present invention aims to provide a non-metallic self-supporting overhead optical cable that has tensile strength and is easy to install.

An embodiment of this invention will be described below with reference to the drawings. In FIG. 5, the same parts as in FIGS. 2 to 4 are given the same reference numerals.

In FIG. 5, a non-metallic optical cable core 20 and a hanging wire 21 made of a non-metallic rod such as an FRP rod or a Kevlar rod are covered with individual plastic sheaths 24 and 25, respectively. As the non-metallic optical cable core 20, for example, one having the structure shown in FIG. 1 is applied. Furthermore, the optical cable 26 and the suspension line 2
7 refers to connecting members 29 provided at regular intervals P.
₁ , 29 ₂ and are spaced apart from each other by a constant distance L. The connecting members 29 ₁ and 29 ₂ are formed into a brim shape so as to surround the optical cable 26 and the hanging wire 27, for example, by a plastic in-die extension molding method. In addition, the connecting member 2
9 ₁ and 29 ₂ are made of the same material as the plastic sheaths 24 and 25 to further strengthen their connection, and can also be formed integrally with the plastic sheaths 24 and 25 of the cable core 20 and suspension wire 21 as appropriate. You may do so. Furthermore, the optical cable 26 is installed longer than the length of the hanging wire 27 between the connecting members 29 ₁ and 29 ₂ . This slack in the optical cable 26 can be removed, for example, when the connecting members 29 ₁ , _{29 2} are injected and extrusion molded.
29 The central part of ₂ , and the optical cable 26 and hanging wire 27
This can be easily set by interposing a plastic material having a thickness calculated according to the necessary slack rate of the optical cable 26 between the two.

Next, the connecting members 29 ₁ and 29 ₂ of the optical cable 26
The part located in the middle is twisted 180 degrees, and that part is integrally connected to the hanging wire 27 by the connecting member ₂₉₃ . At this time, when the optical cable 26 is fixed, the length of the optical cable 26 is compared to the length of the hanging wire.
It is set to be about 0.2% to 2.0% longer. The optical cable 26 may be twisted in the same direction, or may be twisted in the opposite direction to prevent twisting of the cable.

In the above configuration, for example, the optical cable 26
Assuming that a slack of 0.6% is set, even if the suspension wire 27 is stretched by 0.6% due to tension, the elongation rate of the optical cable 26 is "0", and the suspension wire 2
7 is elongated by 0.8%, an elongation (allowable tension) of 0.2% occurs in the optical cable 26. Therefore, compared to the conventional configuration, the tension is four times higher with an optical cable made of the same material and the same size, that is, equivalently, the Young's modulus of the high-strength body is four times higher. For this reason,
Without increasing the outer diameter of the cable, it can be installed overhead under the same conditions as conventional self-supporting cables with metal suspension wires.

Furthermore, by twisting the optical cable 26 180° between the connecting members 29 ₁ and 29 ₂ and fixing it with the connecting member 29, the equivalent height of the cable can be reduced, and the wind pressure load applied to the optical cable 26 can be reduced. This is something that can be reduced.

As detailed above, according to this invention, the outer diameter of the cable is almost the same as that of conventional optical cables using metal suspension wires, and it has an allowable tension sufficient to withstand long-term use. It is possible to provide a non-metallic self-supporting overhead optical cable that is easy to maintain.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view showing an example of a non-metallic optical cable, and Figs. 2 to 4 each show the structure of a conventional non-metallic self-supporting overhead optical cable, where a is a cross-sectional view and b is a cross-sectional view, respectively. A side view of FIG. 5 shows an embodiment of the non-metallic self-supporting overhead optical cable according to the invention, with FIG. 5a being a sectional view and FIG. 5b being a side view. 20...Non-metallic optical cable core, 2
1... Hanging wire, 24, 25... Plastic jacket,
26... Optical cable, 27... Covered suspension wire, 29 ₁
~29 ₃ ...Connection member.

Claims (1)

[Scope of utility model registration request] A suspension wire made of a non-metallic material having a high Young's modulus;
In a non-metallic self-supporting overhead optical cable that is attached to a suspension line and consists of an optical cable that does not use any metal as a cable component, the suspension line and the optical cable are integrally connected at predetermined intervals by connecting members made of non-metallic bodies. At the same time, the optical cable located in the middle of the adjacent connecting members is twisted approximately 180 degrees, and that part is integrally connected to the suspension wire by the connecting member made of a non-metallic material, and in this state, the length of the optical cable is 0.2~ compared to the length of the hanging wire
A non-metallic self-supporting overhead optical cable that is designed to be approximately 2.0% longer.