JPH0350484Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a metal tube for an optical fiber cable suitable for being incorporated into an overhead ground wire to construct an optical fiber composite cable.

Optical fiber cables can transmit large amounts of information, and because they are low loss, non-inductive, and insulating, optical fibers are incorporated into overhead ground wires to transmit information between substations. It is considered to be used for purposes such as transmission of information, transmission of information on power transmission lines, and countermeasures against television interference, and is now entering the stage of practical use. A typical structure of such an optical fiber composite overhead ground wire is as shown in FIG. 1A or 1B. That is, in the case shown in Fig. 1A, an aluminum pipe 2 containing an optical fiber cable 1 is arranged at the center, and around it is an aluminum-covered steel wire (circular wire) 3 with a circular cross section and a diameter of the circular wire. This is a composite overhead ground wire in which aluminum wires (segment wires) 4 having a similar size and thickness and a similar rectangular cross section are combined and twisted into a circular shape so as to interlock with each other.

The one shown in Fig. 1B is a composite overhead ground wire in which an aluminum pipe 2 containing an optical fiber cable 1 is arranged at the center, and aluminum covered steel wires (circular stranded wires) 3 with a circular cross section are twisted together. be.

Such an optical fiber cable 1 is used by being drawn into an aluminum pipe 2 with a certain margin, but an example of its structure is centered around one tension member (tension line) 5a as shown in Fig. 2. , around which the optical fiber 6 and other tension lines 5b
The optical fiber cable 1 is made into a circular shape by applying, for example, a silicone resin sheath 7 on the outside thereof, and is drawn into an aluminum pipe by the action of a tension wire.

The aluminum tube used above is made by rolling aluminum tape into a tube shape and welding the vertical edges to reduce the diameter to an appropriate degree. If necessary, the optical fiber cable can be newly installed using a towing wire, or the existing optical fiber cable can be connected to another optical fiber cable, and then pulled out and installed. It is used as

By the way, these methods have already been developed by the present inventors and have achieved some results, but considering that these works are performed after a long period of time, it is possible that rust will form on the inner surface of the metal pipe. There is also a concern that the frictional force will increase when moving the traction wire or optical fiber cable, and if this work is not smooth over a long tower span of several hundred meters, it will become a difficult work. Therefore, it is necessary to prevent the occurrence of this rust as much as possible.

However, conventional metal tubes for optical fiber cables are
In order to facilitate the work of rolling up the metal tape and welding the vertical ends, degreasing and washing were done as much as possible, and no consideration was given to this aspect at all.

In light of these circumstances, the present invention was developed after various studies and found that if a lubricant is applied to the inner surface of such metal tubes, no rust will occur even over a long period of several years, and new installations and replacements of optical fiber cables will be made smoother. I found out what I could do.

In addition, the optical composite overhead ground wire is 40 to 50 degrees Celsius in summer and -30 degrees Celsius in winter.
In addition, during a lightning surge, the temperature could rise to an abnormally high temperature of around 400℃, albeit momentarily, so silicone grease is a lubricant that does not deteriorate even at such abnormally high temperatures. Most preferred.

Next, the present invention will be explained with reference to the drawings. As shown in FIG. 3, an optical fiber cable or its traction wire 1 is housed in a metal tube 2 with a large degree of freedom. A lubricant 2b is applied to the inner surface of the metal tape 2a of the metal tube 2. 8
shows a weld on the longitudinal edge of a rolled metal tape into a tubular shape.

Since the present invention has the above-mentioned structure, the lubricant film suppresses the formation of rust on the inner surface of the metal tube, which would otherwise occur over a long period of time. This has the effect of allowing smooth towing and easy replacement work.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view showing an example of the structure of an optical composite overhead ground wire, Fig. 2 is a cross-sectional view showing an example of an optical fiber cable, and Fig. 3 is a cross-sectional view showing an example of the metal tube for optical fiber cable of the present invention. It is. 1... Optical fiber cable or its traction wire, 2... Metal tube, 2a... Metal tape, 2
b...Lubricant, 8...Welding part

Claims (1)

[Scope of utility model registration request] Fiber optic composite overhead ground wires, the longitudinal edges of which are rolled into a tubular shape, are welded, the inner surface of which is coated with lubricating oil, and the fiber optic cable or its traction wire is built into the tube with a margin. Metal tube for optical fiber cable to be incorporated.