JPS6040247B2 - POF cable line - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a POF cable line that easily absorbs thermal expansion and contraction of a cable core in a steel pipe, and in particular prevents the occurrence of snake strain near the cable connection due to thermal expansion and contraction of the cable core. cable away from the cable connection.
This makes it easy for snakes to occur in the cable core within a certain extent of the bull core.

Usually, a POF cable line includes a cable core 31 and a cable connection part 32 in a steel pipe 30, as shown in FIG.
The cable core 31 is placed in a straight line except for places where obstacles must be avoided, places with height differences, and bends in the route, and the thermal expansion and contraction of the cable core 31 is controlled by the steel pipe 30. Snake 3 of the cable core 31 that occurs in a relatively wide space between the cable core 31 and the cable core 31
It is absorbed by 6.

However, since the cable core 31 is normally fixed to the steel pipe 30 in such a way as to allow slight movement in the length direction only when the cable connection part 32 is attached, the snakes 36 are concentrated near the cable connection part 32. The radius of curvature of the snake becomes smaller by 4 mm, which tends to cause wrinkles and soft spots in the insulating paper, and there is a risk of dielectric breakdown. This invention solves the above-mentioned drawbacks by providing a curved steel pipe offset part in the vicinity of the cable connection part in the length direction, separating the straight part of the steel pipe from the position of the connection part, so that the cable can be connected at that part. The cable core is made to easily generate snakes to absorb thermal expansion and contraction of the cable core, and the snakes are prevented from reaching the cable connection section.

That is, in FIG. 1, 1 is a steel pipe, 11 is a cable core drawn into it, 12 is a cable connection part thereof, 13 is a straight steel pipe section extending from the position of the cable connection part 12 to the vicinity thereof, and 14 is a steel pipe. This is a curved steel pipe offset section provided at a position separated from the cable connection section 12 by a straight section 13.

Although the offset section 14 is shown as a horizontal offset, it may be a vertical offset or a combination thereof, and may also be half a cycle, one cycle, or more in a wavy manner. Further, when the distance between adjacent cable connection parts is long, it is more effective to provide one or more steel pipe offset parts 15 in the middle to absorb thermal expansion and contraction of the cable. The state in which snakes occur due to thermal expansion and contraction of the cable core 11 according to the present invention configured as described above will be explained with reference to FIG. 2.

In the figure, 24 is the steel pipe offset part, 23 is the steel pipe straight part on the side near the cable connection part, 23' is the steel pipe straight part on the opposite side, 21 is the cable core when there is no load, and 21' is the snake that is caused by thermal expansion. The generated cable core, 27, is the first
Snake 28 indicates a second snake. When the cable is under no load, the steel pipe offset portion 24 is shown as 21.
The cable core is slightly bent in contact with the inner lower wall surface. When the cable core expands due to temperature rise, since the cable core is slightly bent from the beginning, the cable core extending from the steel pipe straight section 23' side increases the above bending, thereby reducing the cable core's elongation. It is absorbed here. When the elongation becomes even larger and comes into contact with the inner upper wall surface of the steel pipe offset portion 24, a second snake 28 is generated adjacent to the first snake 27. The position where this second snake 28 occurs is approximately near the boundary between the steel pipe offset section 24 and the steel pipe straight section 23'. The distance between the cable connection part and the steel pipe offset part 24 is short, so the extension of the cable core due to thermal expansion in this part is small, and the extension of the cable core on the opposite side is due to the cable on the inner upper wall surface of the steel pipe offset part 24. By being pressed against the core, it resists movement toward the cable connection side, and there is also a steel pipe straight section 23 on the cable connection side.
exists, so the second snake rarely occurs in this part. Even if it occurs, it can be stopped by a very small snake. The steel pipe straight section 2 prevents this influence from reaching the cable connection section.
This is due to the existence of 3, and its length of about 4 m is sufficient. As mentioned above, the steel pipe offset part makes it easy for snakes to occur in the cable core, so this part absorbs the thermal expansion of the cable core, and the straight part of the steel pipe prevents the influence of snakes on the cable connection side. be able to.

Also, if the radius of curvature of the steel pipe offset section is made large enough,
The radius of curvature of the generated snake can also be made sufficiently large. In this way, it is completely possible to completely prevent snakes with a small radius of curvature from being concentrated near the cable connection part as in the conventional case, and there is no fear of paper breakage, soft spots, or cable insulation breakdown caused by them.

[Brief explanation of the drawing]

The drawings are all explanatory diagrams of the POF cable line viewed from the vertical direction, and FIG. 1 is an explanatory diagram showing an embodiment of the POF cable line of the present invention, and FIG. 2 is an explanatory diagram showing an embodiment of the POF cable line of the present invention. An explanatory diagram showing the occurrence state and FIG. 3 are explanatory diagrams of a conventional POF cable line. 10: steel pipe, 11: cable core, 12: cable connection part, 13: steel pipe straight part, 14: steel pipe offset part. Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] 1. A POF cable line characterized in that a curved steel pipe offset section is provided in the vicinity of a cable connection part in the steel pipe in the length direction, with a straight steel pipe section separated from the position of the connection part.