JPH03203512A - Laying method of cable - Google Patents

Abstract

PURPOSE:To relax tension of cable remarkably and to enable laying of a long cable by laying the cable in a conduit while supplying a plenty of liquid into a conduit section in the cable laying direction. CONSTITUTION:A tank truck 2A is arranged at a manhole A and a hose 9A is extended to the inlet 6A of a conduit 6 in order to supply a plenty of water 7 toward a manhole B. On the other hand, a tank truck 2B is arranged at the manhole B and the hose 9A is extended in order to suck the water at the outlet 6B of the manhole B, thus forming a water flow in the conduit 6 between the manholes A and B. Under this state, one end 4 of an optical cable 1 is jointed to a pull wire 3 previously passed through the conduit 6, and then the pull wire 3 is pulled by means of a winch 5 thus laying the optical cable 1 in the conduit 6 between the manholes A and B.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for laying cables, and particularly to a method for laying cables with low specific gravity such as optical cables.

[Prior art] In conventional optical cable conduit installation, a rope is first drawn into the conduit, the tip of the optical cable is fixed to the rope,
A method similar to the conventional method has been adopted, in which the rope is pulled into the pipeline.

[Problems to be Solved by the Invention] Nowadays, the reduction in transmission loss of optical fibers has reached almost the limit, and the longer the length of the optical cable, the more convenient it is.

The longer the cable length, the fewer the number of connection points, the less connection loss and connection work at the connection points, which is advantageous in terms of transmission characteristics and economy.

SUMMARY OF THE INVENTION An object of the present invention is to provide a cable installation method that can significantly extend the length of conventional cable installation.

[Findings] The present invention was made based on the fact that since optical cables are extremely light, if the cable is laid while flowing liquid inside the conduit, the resistance to the cable's movement can be significantly reduced.

[Means for Solving the Problems] A first method according to the present invention is characterized in that the cable is drawn into the pipeline and extended while flowing a sufficient amount of liquid in the pipeline in the installation section in the installation direction. There is.

A second method according to the present invention is characterized in that, after filling the conduit, manhole, and handhole in the installation section with liquid, the cable is drawn into the conduit and extended.

[Operation] The present invention will be described below using an example in which the liquid is water.

In method (2) of the cable installation method configured as described above, when installing a light optical cable, the pressure between the cable and the conduit is reduced by flowing a sufficient amount of water in the direction of installation. Since almost no friction occurs, the frictional resistance between the cable and the conduit becomes negligible. Also,
The buoyancy of the water substantially reduces the weight of the cable.

Furthermore, since the water flow is in the direction of cable installation, the frictional force of water on the cable acts to continuously pull the cable at all points. For these reasons, the cable installation tension is greatly reduced, making it possible to install long cables.

On the other hand, in the second method, although there is no traction effect, the cable installation tension is reduced due to a drastic reduction in the coefficient of friction between the cable and the conduit and a substantial reduction in the weight of the cable due to buoyancy. It becomes possible to install cables of 300 cm in length.

[Example] The present invention will be described in detail below with reference to the drawings.

An embodiment of the first method is shown in FIG.

In the figure, symbols A and B indicate manholes or handholes, and an optical cable 1 is connected from manhole A to manhole B.
The mode of laying the is shown.

Note that illustration of other manholes or handholes between manholes AXB is omitted. However, by connecting the conduits on both sides through which the cable 1 passes within these manholes and handholes with separate pipes, water will not overflow into these manholes and handholes.

A tank truck 2A is disposed in the manhole A, a hose 9A is extended to the entrance 6A of the pipe line 6, a sufficient amount of water 7 is discharged, and the water is directed toward the manhole B. On the other hand, a tank truck 2B is arranged in the manhole B, and a hose 9A is extended to draw up water flowing out from the outlet 6B of the manhole B, thereby forming a water flow from the manhole A to the manhole B in the pipe line 6.

In this state, the tip end 4 of the optical cable 1 let out from the drum 8 is connected to the tow rope 3 that has been passed through the conduit 6 in advance, and the tow rope 3 is pulled by the winch 5 to connect the optical cable l to the pipe between the manholes A and B. The cable will be laid within Route 6.

At this time, water has the following effects.

(1) Acts as a lubricant between the conduit 6 and the cable 1,
Reduce the coefficient of friction.

(2) The buoyancy of water substantially reduces cable weight.

(3) The water flow continuously pulls the cable 1 at all locations within the conduit 6 due to the frictional resistance between the water and the cable.

Due to these three effects, the laying tension is significantly reduced, and the cable laying length can be extended accordingly. Furthermore, if the equivalent specific gravity of the entire cable is about the specific gravity of water,
The effects of (1), (2), and (3) above occur so that, theoretically, it is possible to lay a cable of almost infinite length.

FIG. 2 shows another aspect of water delivery, in which a guide pipe 11 is provided in the population 6A of the pipe line 6 of the manhole A, and this guide pipe 1
1 from the hose 9A, and the guide pipe 11
This is an example in which the optical cable 1 is passed through. Thereby, the water and cable 1 are combined before entering the conduit 6, so that the aforementioned effect is further enhanced. Furthermore, there is no need to guide the optical cable 1 at the entrance 6A so as not to damage it.

An embodiment of the second method is shown in FIG.

The pipe entrance outside the installation section of manhole ASB of pipe line 6 is closed with water stop valves IQA and IOB to prevent water from flowing in and out, and manholes A and B and pipe line 6 are filled with water 7. This is an example in which the optical cable 1 is laid in the same procedure as in FIG. 1. In this example, the effect (3) above disappears, but the effect (2),
(3) greatly reduces the laying tension.

[Effects of the Invention] Since the present invention is configured as described above, it is possible to reduce the laying tension per length of the cable and to lay a long cable. According to experiments, it was possible to install the cable with a cable tension that is one order of magnitude smaller than that of conventional cables, so it is expected that the cable length can be increased by one order of magnitude if the cable is installed with the cable tension that is conventional. As a result, the number of connection points of the optical cable is greatly reduced, which is advantageous in terms of transmission loss, and has a great economical effect in that connection construction costs can be greatly reduced.

Further, as a secondary effect, the cable can be laid with low tension without resistance, so damage to the cable during laying is minimized, and furthermore, the water stream has the effect of cleaning the pipeline.

Since the present invention is largely dependent on the buoyancy of water, it is desirable that the equivalent specific gravity of the cable be close to that of water.For non-metallic optical cables that do not contain any metal, the equivalent specific gravity should be 1 or less than 1. Since the present invention has also been realized, great effects can be expected from the present invention.

Furthermore, even for general cables with a high specific gravity, the present invention reduces the installation tension and improves installation workability by reducing the coefficient of friction with the pipeline and substantially reducing the weight of the cable due to the buoyancy of water. It has the same effect. In addition,
A similar effect can be produced using a liquid other than mercury, such as soapy water or oil.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view illustrating an embodiment of the first method of the present invention, FIG. 2 is a longitudinal sectional view illustrating another embodiment of water delivery in FIG. 1, and FIG. FIG. 2 is a longitudinal cross-sectional view illustrating an embodiment of method 2; A, B... Manhole or handhole 1... Optical cable 2A, 2B... Tank truck 3...
Pull line 5...Winch 6...Pipe line 7...Water 11...Guide pipe No. 1 @ Figure 3 Part 2

Claims (2)

[Claims] (1) A method for installing a cable, which comprises drawing the cable into the conduit and extending the cable while flowing a sufficient amount of liquid in the conduit in the installation direction. (2) A method for installing a cable, which comprises filling a conduit, manhole, or handhole in the installation section with liquid, and then drawing the cable into the conduit and extending the cable.