JP2506097B2 - Cable laying method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION "Industrial field of use" The present invention relates to a laying method suitably applied when additionally laying a cable in an underground pipe or the like.

"Prior Art" Fig. 3 shows a conventional example of a cable laying state in an underground pipe.

That is, a plurality of cables 2 are provided in a stacked state in a pipe line 1 formed of a fume pipe or the like buried in the ground. When an additional cable 2'is to be provided in addition to the existing cable 2 as shown by a chain line in FIG. 3, a work of pulling the cable 2'from one end side to the other end side of the conduit 1 Is required.

However, there are many irregularities on the surface of the cable 2, there is a cable coating made of a material having a high friction coefficient such as rubber, and the twist generated in the cable 2 during installation or the cable 2 It is necessary to apply a large tension to the cable 2'when pulling in the additional cable 2'because of unevenness on the surface on which the newly laid cable 2'should be slid due to entanglement or the like. become. The cable 2 or 2'may be damaged by such tension.

Therefore, as shown in FIG. 4, it is conceivable that a grid-like frame plate 3 is provided in advance in the conduit 1 and the cables 2 are arranged one by one in the space surrounded by the frame plate 3. However, this method has a problem that the facility cost is high and the volume utilization efficiency in the pipeline 1 is poor.

The present invention has been proposed in view of the above circumstances, and it is an object of the present invention to reduce frictional resistance generated in a cable when additional cables are laid.

[Means for Solving the Problems] In order to achieve the above-mentioned object, the present invention inserts a tube, which is lighter than a cable to be additionally installed, into a conduit in which a cable is already installed, and then installs the tube. A cable laying method in which a cable to be additionally laid inside is inserted, and the inner surface and the outer surface of the tube are surface-treated to reduce frictional resistance with the already laid cable and the cable to be additionally laid. It is characterized by

"Function" Since the tube is lightweight and the inner and outer surfaces are surface treated to reduce frictional resistance with existing cables or new cables, it is better than inserting a heavy cable directly into the pipeline. Has low friction resistance and good workability.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings.

1 and 2 show the state of a laying pipeline to which the present invention is applied in the order of steps.

In the figure, reference numeral 4 is a tube, and this tube 4 is
It is made of plastic such as polyethylene and polyvinyl chloride, has an inner diameter larger than the outer diameter of the cable to be laid, and its wall thickness is smaller than that of the cable so that the weight per unit length is smaller. It is set. The inner peripheral surface and the outer peripheral surface of the tube 4 are finished to be smooth in order to reduce the frictional resistance between the existing cable and a new cable, and are surface-treated to reduce the frictional resistance. .
That is, a surface treatment such as coating with a tetrafluoroethylene resin or application of a lubricant such as silicon oil is performed. In addition, in the tube 4,
It is desirable to apply a material that is soft relative to the cable's dressing (e.g. rubber) so as not to damage the cable when contacting it.

The additional laying of a cable using the tube 4 thus constructed is first inserted into the pipe line 1 and then the new cable 2 ′ is inserted into the tube 4 as shown in FIG.
Is done by inserting. After the cable 2'is inserted, the tube 4 remains as it is.
By leaving the tube 4 in this way, the cable 2 ′ in the tube 4 can be easily pulled out to facilitate subsequent maintenance and inspection work or cable exchange work.

When a plurality of additional cables 2'is laid, a plurality of tubes 4 may be prepared and the work may be performed in the same procedure.

The inner diameter of the tube 4 is preferably small from the viewpoint of reducing the weight in order to increase the flexibility of the tube 4 itself or to increase the volumetric efficiency in the conduit 1, but Considering workability when inserting the new cable 2 ', it is necessary to have a certain margin with respect to the outer diameter of the cable 2'.

Further, the tube may be provided in the pipeline in advance at the time of construction, not only when the cable is additionally laid.

Furthermore, the tube does not necessarily have to be flexible, and can be regarded as a substantially rigid body like a so-called PVC pipe, for example, when the pipe line is linear or bent with a very large curvature. It may be something like this.

"Effect of the invention" As is clear from the above description, according to the present invention, when an additional cable is laid in a pipeline in which the cable is already laid, first, a tube lighter than the cable is inserted, and then Since the cable is inserted into the tube, the cable between the existing cable and the tube or between the tube and the new cable is compared with the case where the existing cable and the new cable directly contact each other. The frictional resistance between them is reduced, and therefore, the tension at the time of laying the cable can be minimized to improve workability and prevent damage to the cable.

[Brief description of drawings]

FIG. 1 and FIG. 2 show an example of a conduit in which a cable is laid by applying the present invention. FIG. 1 is a perspective view when a tube is inserted, and FIG. 2 is a perspective view when a cable is inserted. FIG. 3 is a cross sectional view showing an example of a conventional laying pipeline, and FIG. 4 is a cross sectional view showing another example of a conventional laying pipeline. 1 ... pipe, 2 ... (existing) cable, 2 '... (new) cable, 4 ... tube.

Claims (1)

(57) [Claims] 1. A tube (4) which is lighter than a cable (2 ') to be additionally installed is inserted into a conduit (1) in which a cable (2) has already been installed, and then added to the installed tube. A method of laying a cable for inserting a cable to be laid, wherein the inner surface and the outer surface of the tube (4) have a small frictional resistance between the cable (2) already laid and the cable (2 ') to be additionally laid. A cable laying method characterized by being surface-treated in order to do so.