JP2002271931A - Inner duct for additional installation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate additional installation of a cable. SOLUTION: An inner duct containing a plurality of conduits in it is laid in an existing conduit. As one cable is installed in one conduit in the inner duct, entangling of cables can be avoided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inner duct for additional laying, which is suitable for additionally laying a cable in an existing pipeline in which a cable has already been laid.

[0002]

2. Description of the Related Art Conventionally, there have been the following methods for laying a cable in a conduit arranged so as to connect two manholes. First, a rod made of, for example, carbon is passed through the pipe from the manhole on one end to the manhole on the other end. And in the other end side manhole,
The rod and the string are connected to each other. Then, by pulling the rod back to the manhole on one end,
A cable is laid in the pipeline from the other end to the manhole on one end. Finally, in the manhole on the one end side, the cable and the cable are connected, and the cable is pulled from the manhole on the other end side by using a towing means such as a winch along this pipeline. Thereby, the cable is pulled and laid from the manhole on the one end side to the manhole on the other end side.

[0003]

By the way, with the recent increase in the amount of communication, it is expected that a plurality of cables will need to be laid in one pipeline in the future. in this case,
A so-called additional laying in which a new cable is added and laid in a pipeline in which a cable is already laid is performed.

However, when such an additional cable is laid, the conventional cable laying method described above requires
When the rod is inserted into the pipe, the presence of the already laid cable causes the rod to become entangled with the cable, so that there is a disadvantage that the rod cannot be inserted reliably and easily. Further, even if the rod can be inserted while the rod is entangled with the cable, there is a problem that the cables are entangled with each other when the cable is laid, and the cable cannot be laid.

Therefore, conventionally, for example, Japanese Patent Application No.
A method has been adopted in which a cable is laid using a special jig for additional laying as shown in -31937 so that the rod does not become entangled with the cable when the rod is first passed.

As shown in FIG. 6, an additional laying jig 7 described in Japanese Patent Application No. 11-311937 includes a main body 78 provided to extend forward from the tip of the rod 6 and an existing pipe line. First rolling wheels 74, 74 for rolling the outer peripheral surface of the existing cable 3 laid along the cable 4 along the existing cable 3;
And a second rolling wheel 75, 75 abutting against the inner peripheral surface of the main body and rolling on the inner peripheral surface along the tube axis.
The first and rear members 72 are attached to the connecting member 73 so as to be rotatable around swing axes Y1 and Y2 perpendicular to the longitudinal direction of the rod, respectively, and provided with bent portions 7a and 7b in the body.

However, when a plurality of additional cables are to be laid, it is necessary to attach the above-mentioned jig to the rod when laying the respective cables. There is a problem that a plurality of special jigs must be prepared.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and when a plurality of cables are additionally laid in an existing pipeline in which cables are already laid, the additional laying is easier than in the past. It is an object of the present invention to provide an inner duct for additional laying that can be performed.

[0009]

SUMMARY OF THE INVENTION The present invention is directed to an inner duct for additionally laying a cable in an existing pipeline in which a cable is already laid, wherein a plurality of pipelines for laying a cable are provided inside. Have.

Further, in the present invention, the sectional shape of the inner duct has a sectional area occupying 60% to 80% of the gap of the existing pipeline.

Further, in the present invention, the cross-sectional shape of the inner duct has a shape of a crescent moon to a crescent moon.

[0012]

The inner duct for additional installation according to the present invention has the following features.
Since there are multiple conduits for laying cables inside one inner duct, once laid, only one cable is laid in one conduit. In addition, the cables do not become entangled with each other, so that the cables can be reliably and easily inserted.

Further, the inner duct for additional installation according to the present invention has a shape occupying 60% to 80% of the gap of the existing pipeline, so that there is no useless space in the existing pipeline. The space in the existing pipeline can be used effectively.

Further, since the inner duct for additional installation according to the present invention has a cross-sectional shape of a crescent moon to a six-moon moon, it has a shape that can be smoothly installed in the existing pipeline. .

[0015]

FIG. 1 is a cross-sectional view of an inner duct for additional installation according to the present invention, wherein 1 is an inner duct for additional installation, 2... A pipe for installing additional cables provided inside the inner duct. Road.

FIG. 2 is a sectional view showing a case where the inner duct 1 for additional installation according to the present invention is installed in an existing pipeline, 3 is an existing cable, and 4 is an existing pipeline.

The inner duct 1 for additional laying in FIGS. 1 and 2 has a portion A having substantially the same shape as the inner peripheral surface of the conduit and a portion B having a substantially concave shape so as to sandwich the existing cable at the center. When compared to the shape of a moon, it has a shape of a crescent moon to a crescent moon which is larger than a crescent moon and smaller than a half moon. By having this shape, it is a shape that is laid smoothly in the existing pipeline, and also a shape that can effectively utilize the space of the existing pipeline.

In FIG. 2, the inner diameter of the existing pipeline is 75 mm.
A cable having an outer diameter of 30 mm has already been laid. The additional installation inner duct 1 is provided with one pipe having an inner diameter of 23 mm and two pipes having an inner diameter of 20 mm.

The inner duct 1 for additional laying was manufactured by extrusion using high-density polyethylene as a material. Generally, as the material, a polyolefin-based or polyvinyl chloride-based plastic material can be used.

The inner duct may have a structure in which a tension member is provided in order to have a tensile strength.

The inner duct 1 for additional installation in FIGS. 1 and 2 has a configuration having three pipes 2..., But is not limited to this. It is possible to appropriately design according to the outer diameter and the number, and it is only necessary to have a plurality of pipes 2.

Next, a method of additionally laying a cable will be described with reference to FIGS. As shown in FIG. 4, the existing pipeline 4 is disposed underground so as to connect the two manholes H1 and H2 formed at a predetermined distance from each other with one of them as a starting point and the other as an end point. ing. An existing cable 3 is laid between the manholes H1 and H2 in the existing pipeline 4.
Additional cables will be laid inside.

At the position of the manhole H1 at one longitudinal end of the existing pipeline 4, a drum 9 around which a rod 6 is wound is provided.
Are arranged. A cable laying jig 7 as disclosed, for example, in Japanese Patent Application No. 12-311937 is attached to the tip of the rod 6 pulled out of the drum 9 so that the rod does not become entangled with the cable. .

Then, the rod 6 is pushed toward the manhole H2 at the one end side of the manhole H1 and inserted into the existing pipeline 4 (see the arrow in the figure).

When the rod 6 is inserted into the manhole H2 on the other end, the cable laying jig 7 is
5, at the position of the manhole H2 on the other end, as shown in FIG. 5, the leading end of the rod 6 and the wire string 8 wound around the drum 10 disposed at the position of the manhole H2 on the other end. Concatenate. And the rod 6
Is pulled back from the manhole H1 at one end (see the arrow in the figure). By doing so, the above-mentioned wire string 8
From the manhole H2 on the other end to the manhole H1 on the one end
Until then, it is laid in the existing pipeline 4.

Then, at the position of the manhole H1 on the one end side, the wire string 8 and the inner duct 1 for additional installation are connected, and the wire string 8 is separated from the manhole H2 on the other end side by, for example, a winch or the like. The additional installation inner duct 1 is laid from the manhole H1 on one end side to the manhole H2 on the other end side by towing using. In this way, the additional installation inner duct 1 is installed.

In the case of a conventional cable laying method that does not use the inner laying duct for additional laying, one additional cable is laid by the above-described laying method. It was necessary to repeat the above operation a plurality of times.

On the other hand, in the present invention, after the above-described inner duct is laid, only one cable is passed through the pipe 2 inside the additional inner duct 1, so that the above-mentioned jig needs to be used. In addition, the cables can be securely and easily laid without the cables being entangled.

If a cable for laying a cable is previously inserted into each of the pipes 2 inside the inner duct 1 for additional laying, the cable is first pulled back through the rod as described above. Since the labor is reduced, the speed of the installation work can be increased.

The above-mentioned cable can be applied to any of a metal communication cable, an optical fiber cable and a power cable.

FIG. 3 shows another embodiment of the inner duct according to the present invention, in which flexible corrugated tubes 5 are partially fused or adhered in some places, and three tubes are integrally joined. ing. The number of flexible corrugated pipes in the inner duct does not need to be three, and can be appropriately designed according to the free space of the existing pipeline and the outer diameter and number of cables to be laid. A plurality of corrugated tubes 5 may be joined and integrated.

The material is a polyolefin-based material,
Alternatively, a polyvinyl chloride plastic material can be used.

[0033]

As described above, the inner duct for additional laying according to the present invention has a plurality of conduits for laying inside one inner duct, so that the inner duct is laid once. After that, when laying additional cable, only one cable is laid in one pipeline, so that the cables do not become entangled with each other and the cable can be inserted reliably and easily. When a plurality of cables are additionally laid in a road, a great effect is achieved.

The inner duct for additional installation according to the present invention has a shape occupying 60% to 80% of the gap of the existing pipeline, so that the space of the existing pipeline can be effectively utilized. In addition, since the cross section has a shape of a crescent to a crescent, it can be laid smoothly in the existing pipeline.

[Brief description of the drawings]

FIG. 1 is a sectional view of an inner duct according to the present invention.

FIG. 2 is a cross-sectional view of a state where an inner duct according to the present invention is laid in an existing pipeline.

FIG. 3 is a sectional view showing a state in which an inner duct according to another embodiment of the present invention is laid in an existing pipeline.

FIG. 4 is a schematic explanatory view showing a rod insertion operation.

FIG. 5 is a view corresponding to FIG. 4, illustrating a work of laying a line string;

FIG. 6 shows a jig for additional laying.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Inner duct for additional installation 2 Pipe line 3 Existing cable 4 Existing pipe line 5 Flexible pipe H1 Manhole H2 Manhole

Claims (3)

[Claims] An inner duct for additionally laying a cable in an existing pipeline in which a cable is already laid, wherein the inner duct has a plurality of pipelines for laying a cable therein. For inner duct. 2. The inner duct for additional installation according to claim 1, wherein the cross-sectional shape of the inner duct has a cross-sectional area occupying 60% to 80% of the gap of the existing pipeline. 3. The additional duct according to claim 1, wherein the cross-sectional shape of the inner duct has a shape of a crescent to a crescent.