JP2828122B2 - Optical fiber composite overhead ground wire - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber composite overhead ground wire, and more particularly to an optical fiber composite overhead ground wire in which a compressive residual stress is applied to an aluminum pipe constituting an OP unit to improve bending fatigue strength.

[0002]

2. Description of the Related Art Optical fiber composite overhead ground wire (OPGW)
The optical cable is built into the overhead ground wire, and the function as the overhead ground wire and the communication function are combined, for example,
OP consisting of multiple optical cables stored in an aluminum pipe
The unit is arranged at the center of a stranded wire such as an Al wire or an Al-St clad wire. The aluminum pipe located at the center mechanically protects the optical cable and plays a role in maintaining the transmission characteristics of the optical cable normally.

The aluminum pipe disposed at the center of the stranded wire has a diameter of about 5 to 6 mm, which is larger than the diameter of the stranded wire, so that the optical fiber composite overhead ground wire receives bending stress due to vibration or the like. Sometimes bending distortion occurs in the aluminum pipe. 4 (a) and 4 (b) show the strain distribution of the optical fiber composite overhead ground wire by an arrow. For example, the optical fiber composite overhead ground wire has a rigid body with no slippage between the stranded wire and the aluminum pipe. 4A, the distortion of the aluminum pipe 2 with respect to the bending stress M is small as shown in FIG. 4 (a), but in the case of the optical fiber composite overhead ground wire in which the stranded wire is arranged on the outer periphery of the aluminum pipe. Since the stranded wire can be moved in the longitudinal direction, the distortion is matched to the diameter of the stranded wire as shown in FIG. At this time, assuming that the wire diameter of the stranded wire is 3 mm and the diameter of the aluminum pipe is 6 mm, the aluminum pipe undergoes twice the distortion. For this reason, it is an important subject to manufacture a high-strength aluminum pipe.

[0004] Usually, an aluminum pipe is manufactured by welding, and as shown in the manufacturing flow of FIG.
For example, a 0.5 mm rolled aluminum tape 5 is formed into a cylindrical shape, and the optical cable 3 is accommodated therein. Thereafter, both ends of the aluminum tape are butt-welded and then drawn by a roller die or a drawing die to obtain an aluminum pipe 6 having a predetermined size. Further, in the process from the forming to the elongation, a processing method may be employed in which a floating plug is arranged inside the pipe 6 so as to smooth the inner surface and improve the strength by plastic working of the aluminum pipe.

[0005]

However, according to the conventional optical fiber composite overhead ground wire, at present, tensile residual stress is generated on the surface of the aluminum pipe due to plastic working such as rolling and pipe making. is there. Since the tensile residual stress lowers the strength of the aluminum pipe, if the electric wire is subjected to bending stress due to vibration or the like in the actual overhead wire state, there is a disadvantage that the internal aluminum pipe is broken and the optical cable is damaged.

In order to overcome such weaknesses of the aluminum pipe, it is conceivable to use a material having high strength, for example, an iron tape or a stainless steel tape. It cannot be applied as a material.

Accordingly, it is an object of the present invention to provide an optical fiber composite overhead ground wire capable of improving the bending fatigue strength of an aluminum pipe.

[0008]

SUMMARY OF THE INVENTION In view of the above problems, the present invention provides an optical fiber in which the outer surface of an aluminum pipe is subjected to surface processing such as sandblasting or shot peening in order to improve the bending fatigue strength of the aluminum pipe. A composite overhead ground wire is provided.

[0009]

According to the present invention, the outer surface of the aluminum pipe is subjected to surface processing to have a compressive residual stress, whereby the bending fatigue strength of the aluminum pipe can be greatly improved.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an optical fiber composite overhead ground wire according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows an embodiment of the present invention.
Alternatively, an aluminum pipe 2 is disposed at the center of a stranded wire 1 such as an Al-St clad wire, and an optical cable 3 is housed inside the aluminum pipe 2. The outer surface of the aluminum pipe 2 is subjected to surface processing such as sandblasting or shot peening.

By subjecting the outer surface of the aluminum pipe 2 to surface treatment such as sand blasting or shot peening, a compressive residence stress is applied to the aluminum pipe 2 and thereby the bending fatigue strength can be improved.

Next, the bending fatigue strength of the untreated aluminum pipe and the surface-treated aluminum pipe was measured, and the rate of increase in the bending fatigue strength of the surface-treated aluminum pipe was examined.

First, the bending fatigue strength of an untreated aluminum pipe was measured. FIG. 2 shows the measurement results.
Next, N = 10 ⁷ bending fatigue limits σ in this curve
Bending fatigue limit σwa when shot peening is repeated 5 times after aluminum pipe drawing based on w = 5.5 kgf / mm ^2, and when shot peening is repeated 5 times on aluminum tape and then welded and drawn The ratios σwa / σw and σwb / σw of the sample to the bending fatigue limit σwb were measured. FIG. 3 shows the measurement results. As can be seen from the figure, the bending fatigue strength of the shot-peened aluminum pipe after the aluminum pipe drawing in (a) is about 30% higher than that of the non-surface-processed aluminum pipe. The bending fatigue strength of an aluminum pipe that has been shot peened and then welded and drawn is increased by about 15% as compared with the case where the surface is not processed. Furthermore, (c) shot blasting after aluminum pipe drawing, and (d) shot blasting on aluminum tape.In each case, the fatigue strength is higher than that of aluminum pipe without surface processing. You can see that it is higher.

[0015]

As described above, according to the optical fiber composite overhead ground wire of the present invention, since the outer surface of the aluminum pipe is subjected to surface processing such as sandblasting or shot peening, the bending fatigue strength of the aluminum pipe is greatly increased. Can be improved. Therefore, even if bending stress is applied to the electric wire, the aluminum pipe is not broken, the internal optical cable can be reliably protected, and the optical transmission characteristics can be maintained normally.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing one embodiment of the present invention.

FIG. 2 is a graph showing the bending fatigue strength of an untreated aluminum pipe.

FIG. 3 is a graph showing an increase in fatigue strength of a surface-treated aluminum pipe.

FIG. 4 is an explanatory diagram showing a distribution of strain with respect to bending stress applied to an optical fiber composite overhead ground wire.

FIG. 5 is an explanatory view showing a manufacturing flow of a conventional aluminum pipe.

[Description of Signs] 1 Steel stranded wire 2 Aluminum pipe 3 Optical cable 5 Aluminum tape 6 Aluminum pipe

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H01B 11/22 G02B 6/44

Claims (1)

(57) [Claims] 1. An optical fiber composite overhead ground wire comprising a plurality of aluminum pipes accommodating a plurality of optical fibers in an aluminum stranded wire or an aluminum stranded steel wire, wherein the aluminum pipe is sandblasted on an outer surface thereof. An optical fiber composite overhead ground wire that has been subjected to surface processing such as shot peening.