JP2005327480A - Overhead cable - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an overhead cable that reduces a wind pressure load and can prevent a load from being increased by snow. <P>SOLUTION: The overhead cable has a cable 1A used as a transmission line and recesses 12A, 12B provided in the coating of the cable 1A. The recesses 12A, 12B increase the surface area of the cable 1A, thus reducing the wind pressure load and suppressing the development of snow accretion. The recesses 12A, 12B are regularly arranged in the circumferential and longitudinal directions of the cable 1A. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an aerial cable used as a communication transmission line.

  Conventionally, this type of aerial cable has a cross-sectional shape that is a combination of a regular shape and a circular shape. Because of this shape, the airflow around the overhead cable becomes a symmetrical flow field, the mixing of the airflow in the downstream field of the overhead cable is small, and the efficiency coefficient of the overhead cable is large. Is big. That is, a pressure difference is generated between the front portion of the overhead cable that receives the wind and the rear portion of the overhead cable, and the wind pressure load is increased. In addition, in the case of an overhead cable with a small surface area, snowfall develops during snowfall, and the load increase due to snow is large.

There is an aerial cable that reduces wind pressure load and prevents an increase in load due to snow (Patent Document 1). In this aerial cable, one groove and one ridge are provided on the outer surface along the longitudinal direction, and the groove and the ridge are repeatedly crossed.
Japanese Utility Model Publication No. 2-119606

  The conventional aerial cable described above has the following problems. An aerial cable having no unevenness on its outer jacket has a circular cross-sectional shape, so that the airflow around it is difficult to mix and the wind pressure load is large. Furthermore, it is easy to snow due to the small surface area compared to the case where the outer cover is uneven. Furthermore, when snowfall grows, the weight and wind receiving cross section increase. In particular, when the aerial cable is an optical fiber cable, there is a possibility that the distortion of the optical fiber increases or the overhead cable itself is cut.

  Further, in an aerial cable in which grooves and ridges are formed, since the grooves and ridges are provided on the outer surface of the cable, processing is not easy. In addition, since the protrusions are provided on the outer surface of the cable, the cable does not fit properly when the cable is wound and stored.

  An object of the present invention is to provide an aerial cable capable of solving the above-described problems, reducing wind pressure load, and preventing an increase in load due to snow.

In order to solve the above-mentioned problem, the invention of claim 1 includes a cable and a recess provided in an outer jacket of the cable, and the surface area of the cable is increased by the recess to reduce the wind pressure load. This is an aerial cable characterized by suppressing the development of snow accretion.
According to a second aspect of the present invention, in the overhead cable according to the first aspect, the depressions are irregularly arranged on a jacket of the cable.
According to a third aspect of the present invention, in the overhead cable according to the first aspect, the depressions are regularly arranged in a circumferential direction and a longitudinal direction of the cable.
According to a fourth aspect of the present invention, in the overhead cable according to any one of the first to third aspects, the recess has at least one of a hemispherical shape, a semi-elliptical shape, and a polygonal shape. It is characterized by.

  The overhead cable according to the present invention has the following effects. Since there is a depression in the jacket of the aerial cable, the airflow around the aerial cable is mixed on the downstream side, and the wind pressure load can be reduced. In addition, since there is a depression in the jacket of the aerial cable, it becomes difficult for snow to go around the aerial cable at the depression and easily fall before it accumulates on the aerial cable. Therefore, there is almost no increase in weight due to snowfall, and the overhead cable is less likely to break. As a result, under various circumstances, it is possible to realize further slimming of transmission line structures such as wires and utility poles that support overhead cables, and to realize economical outdoor communication facilities.

Next, the best mode for carrying out the present invention will be described with reference to the drawings.
[Embodiment 1]
The aerial cable according to the present embodiment is an optical fiber aerial cable. As shown in FIGS. 1 and 2, the aerial cable 1 according to the present embodiment is supported between utility poles by a support wire 3 via a neck 2.

The aerial cable 1 is made by providing a recess in the outer sheath of a cable 1A that is an optical fiber cable. That is, in the cable 1A, the jacket 12 is formed on the outer side of the core portion 11 made of a plurality of optical fiber core wires (not shown). On the surface of the jacket 12 of the cable 1A, hemispherical depressions 12A and 12B are regularly arranged in the outer circumferential direction and the longitudinal direction. The shapes of the recesses 12A and 12B are the same, and the diameters of the recesses 12A and 12B are d. The diameter d of the recesses 12A and 12B is determined according to the diameter of the cable 1A. Specifically, when the diameter of the cable 1A is D, the diameters of the recesses 12A and 12B are set to 0.2588D or less. That is, the diameter d of the recesses 12A and 12B is
0 <d ≦ 0.2588D
It is. In FIG. 1 and FIG. 2, only typical depressions are denoted by reference numerals in order to avoid complication of the drawings.

  In order to increase the surface area, it is conceivable that the depressions 12 </ b> A and 12 </ b> B of the outer jacket 12 are arranged as much as possible, but in order to maintain the strength of the outer jacket 12, it is desirable to arrange them at regular intervals. Therefore, in this embodiment, six hollows 12A are arranged at equal intervals in the circumferential direction of the cable 1A. Further, the center interval L1 of the recesses 12A is arranged at an interval four times the diameter D of the recesses 12A with respect to the longitudinal direction of the cable 1A. Also, an offset of 30 degrees (angle θ = 60) from the center of the recess 12A to a position (interval L2) twice the diameter D of the recess 12A from the center of the cable 1A and in the circumferential direction of the cable 1A. The six depressions 12B having the same degree are provided.

  The aerial cable 1 according to this embodiment has the above structure. In the present embodiment, recesses 31 </ b> A and 31 </ b> B similar to the overhead cable 1 are provided on the surface of the support wire 3.

  When the aerial cable 1 having the above structure is hung between utility poles, it is actually difficult to keep the aerial cable 1 in a uniform state in the circumferential direction, that is, the positions where the recesses 12A and 12B are vertically symmetrical. . For this reason, as shown in FIG. 3A, the recess 12A of the outer jacket 12 is in a vertically asymmetric position. In FIG. 3, a broken line indicates a streamline. When the recess 12A is in a vertically asymmetrical position, on the outer peripheral surface of the overhead cable 1, the recess 12A causes a difference in the separation points A1 and A2 above and below the air flow, and then the flow mixing occurs in the flow field C. It becomes easy. In addition, due to the recess 12 </ b> B arranged with an offset with respect to the longitudinal direction of the overhead cable 1, a three-dimensional difference occurs in the separation point of the flow over the entire interference radius. As a result, in the wake field C, more rapid flow mixing occurs, resulting in a decrease in drag coefficient and a decrease in wind pressure load. That is, the pressure difference between the front part of the overhead cable 1 that receives the wind and the rear part of the overhead cable 1 is reduced, and the wind pressure load can be reduced. Compared to this, as shown in FIG. 3B, the conventional aerial cable 101 has a circular cross section, so that the airflow around the aerial cable 101 becomes a symmetrical flow field, and the airflow is separated vertically. Points M1 and M2 are the same. As a result, since the mixing of the airflow in the wake field M of the aerial cable 101 is small and the effectiveness coefficient of the aerial cable 101 is large, the wind pressure load is large. In FIG. 3B, 101A is a core wire portion and 101B is a jacket.

  In addition, snowfall during snowfall is as follows. As shown in FIG. 4A, it takes time for the snow S to enter the recess 12A on the upper side of the overhead cable 1 and for the snow S to go downward. For this reason, before the snow S goes around to the lower side, it is blown away by the wind or melted due to the temperature rise. In addition, even when the snow S wraps downward, the snow S hardly adheres to the aerial cable jacket because of the depression 12A on the lower side. It becomes difficult. Compared to this, as shown in FIG. 4B, in the case of the aerial cable 101 having no recess and a small surface area, snowfall develops during snowfall, and the load increase due to the snow S increases.

  As described above, according to this embodiment, it is possible to realize an optical fiber aerial cable that has a low wind pressure and is difficult to snow, that is, a low wind pressure difficult to snow aerial cable. Similarly, the support line 3 can also be made to have a low wind pressure difficult snowfall. Furthermore, since there are no protrusions on the surface as in the prior art, the aerial cable 1 that can be stored with good fit can be realized.

[Embodiment 2]
In Embodiment 1, although the shape of the hollow provided in the jacket of the overhead cable 1 and the surface of the support wire 3 was hemispherical, in this embodiment, the hollow of various shapes is used. As these shapes, for example, a semi-elliptical depression such as a football shape or a polygonal depression such as a diamond shape is used. Moreover, you may mix and use these hollows. Even if these depressions are used, a low wind pressure difficult-to-snow aerial cable can be realized as in the first embodiment.

[Embodiment 3]
In the first and second embodiments, the pits provided in the jacket of the overhead cable 1 and the surface of the support wire 3 are regularly arranged. Even in the case of using the depressions with such an arrangement, a low wind pressure difficult-to-snow aerial cable can be realized as in the first embodiment.

  The embodiment of the present invention has been described in detail above, but the specific configuration is not limited to each embodiment, and even if there is a design change or the like without departing from the gist of the present invention, the present invention is not limited thereto. included. For example, in Embodiments 1 to 3, the example in which the aerial cable 1 is supported by the support line 3 has been described, but the aerial cable 1 that is not supported by the support line 3 may be used.

It is a front view which shows the aerial cable by Embodiment 1 of this invention. It is sectional drawing which shows the II cross section of FIG. It is explanatory drawing explaining the airflow of an aerial cable, (a) shows the aerial cable by this invention, (b) shows the conventional aerial cable. It is explanatory drawing explaining the snow accretion with respect to an aerial cable, (a) shows the case of the aerial cable by this invention, (b) shows the case of the conventional aerial cable.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Overhead cable 1A Cable 11 Core wire part 12 Outer sheath 12A, 12B hollow 2 Neck part 3 Support wire 31A, 31B hollow

Claims (4)

Cable (1A);
Dents (12A, 12B) provided in the jacket of the cable (1A);
Have
An aerial cable characterized in that the surface area of the cable (1A) is increased by the depressions (12A, 12B) to reduce wind pressure load and to suppress the development of snow accretion.   The aerial cable according to claim 1, wherein the depressions are irregularly arranged on a jacket of the cable (1 A).   The aerial cable according to claim 1, wherein the depressions are regularly arranged in a circumferential direction and a longitudinal direction of the cable (1A).   The aerial cable according to any one of claims 1 to 3, wherein the recess has at least one of a hemispherical shape, a semi-elliptical shape, and a polygonal shape.

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