JP2001095122A - Method for sending optical cable with air-pressure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for sending an optical cable with air-pressure for surely laying an optical cable even in the long-distance sheath-pipe route including many curving areas of small radius of curvature. SOLUTION: At the end of a light-weight optical cable 3 having a small bending rigidity of optical cable, a pressure receiving head 7 which generates a propulsive force when it receives an air pressure is attached. Thereafter, the optical cable 3 is inserted to a sheath pipe 6 and is then laid by supplying the high-pressure air into the sheath pipe 6. As a result, the long-distance cable laying can be realized because a propulsive resistance is very small even when the sheath pipe 6 includes the curving area of small curvature of radius.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical cable pneumatic feeding method.

[0002]

2. Description of the Related Art When an information communication optical cable is buried underground, it is necessary to protect the optical cable from external pressure and groundwater.
It is common to lay it inside a sheath tube made of polyethylene or steel. As the laying method. Recently, the pneumatic feeding method, which can be laid for a long distance and does not exert excessive tension on the optical cable, has been spotlighted.

In the conventional pneumatic feeding method, a pressure receiving head that generates a propulsive force when receiving air pressure is attached to the end of an optical cable, and then inserted into a sheath tube using a caterpillar to supply high-pressure air into the sheath tube. Thus, optical cables have been laid.

[0004] The optical cable used for laying in the conventional construction method has a large bending rigidity, so that the propulsive force of the caterpillar is transmitted to the tip very effectively, and the optical cable can be propelled far.

[0005] That is, in the conventional method, long-distance laying in the sheath tube is possible only by using both the pushing force by the caterpillar and the pushing force generated by the high-pressure air flow. For this reason, in the conventional method, use of an optical cable having high bending rigidity has been one of the essential conditions.

[0006]

By the way, in the conventional method, the bending rigidity of the optical cable is an indispensable factor for feeding the optical cable to a distant place. It was a big bottleneck in laying distance.

[0007] In order to solve such problems, studies have been made on lubricants for reducing frictional resistance and on low-friction sheaths. Although some results have been obtained, they have not yet been drastically solved. The fundamental problem is that the bending rigidity of the optical cable is large, and the problem cannot be solved unless the bending rigidity is reduced.

Accordingly, an object of the present invention is to solve the above-mentioned problems and to provide an optical cable pneumatic feeding method capable of securely laying an optical cable even in a long-haul tube route having a small curvature and many curves. It is in.

[0009]

In order to achieve the above-mentioned object, an optical cable pneumatic feeding method according to the present invention is characterized in that a pressure receiving head that generates a propulsive force when receiving air pressure is attached to the tip of an optical cable, and then the optical cable is vertically moved. In a pneumatic pumping method in which an optical cable is laid by inserting it into a sheath tube by the driving force of a caterpillar and supplying high-pressure air into the sheath tube, the bending rigidity is small, and a lightweight optical cable is pneumatically sent. It is.

In the optical cable pneumatic feeding method of the present invention, in addition to the above structure, it is desirable that the tension member of the optical cable is an FRP fiber bundle, whereby the bending rigidity of the optical cable can be reduced and the weight can be reduced.

In the pneumatic optical cable feeding method according to the present invention, in addition to the above-described structure, it is desirable that the inner layer of the slot rod of the optical cable is made of foamed polyethylene.

In addition to the above configuration, in the optical cable pneumatic feeding method of the present invention, a cut may be made in the slot wall of the slot rod of the optical cable, whereby the rigidity of the optical cable can be reduced.

In addition to the above configuration, in the optical cable pneumatic feeding method of the present invention, the PE sheath of the optical cable may be subjected to corrugation, whereby the bending rigidity of the optical cable can be reduced.

According to the present invention, a pressure receiving head that generates a propulsive force when it receives air pressure is attached to the tip of an optical cable having a small bending rigidity and a light weight, and then inserted into a sheath tube by a caterpillar. The optical cable is pneumatically fed by supplying high pressure air. As a result, even when the sheath tube has a curved portion having a small curvature, the bending rigidity of the optical cable is small, so that the propulsion resistance is extremely small and a long distance can be laid.

Here, since the optical cable used in the present invention has a particularly small bending stiffness, it is difficult to transmit the pushing force from the rear by the caterpillar to the distal end by simply inserting the optical cable into the sheath tube, and May meander.

Therefore, in the present invention, in the initial state of the installation, as a substitute for the pushing force from the rear of the caterpillar, a pressure-receiving head that generates a propulsive force when receiving high-pressure air is attached to the tip of the optical cable. By maximally utilizing the propulsion force, the optical cable is drawn into the sheath tube.

Although the pressure receiving head itself has been used depending on the situation even in the conventional method, the concept of its use is that when the inner diameter of the sheath tube is 2.5 times or more the outer diameter of the optical cable, and when the length is longer. It is considered to be effective as an auxiliary propulsion force when the distance is laid, and the effect in the early stage of laying was not considered at all. This is because the bending rigidity of the optical cable is large in the conventional method, so in the early stage of laying, the propulsion force from the back by the caterpillar can be effectively transmitted to the tip of the optical cable sufficiently and can be propelled far, so the assistance of other propulsion force is not It was not needed at all.
Actually, there was no example of stopping due to insufficient propulsion at the early stage of installation.

Another important point is that when the flow of air is in a steady state, the pressure becomes high near the inlet of the sheath tube due to the compressibility of the air, but the flow is almost nil or extremely slow. This is the fact that almost no propulsion is generated in the pressure receiving head and the optical cable in this portion.

Therefore, in the conventional method, the vicinity of the inlet of the sheath tube is recognized as a blank portion of the propulsive force due to the air flow. In order to cover this blank portion, it is necessary to increase the bending rigidity of the optical cable and push it in from behind. It has been thought of as a condition. As a result, the propulsion resistance of the curved portion is increased due to the magnitude of the bending rigidity, and the actual situation has been to sacrifice that it is difficult to lay the curved long distance.

This is one of the blind spots. The phenomenon described above occurs when the air flow is in a steady state. However, considering the transient state immediately after the air supply, the air is clearly flowing, and the pressure When the head is placed, a propulsive force is naturally generated by the air flow. In addition, since the state at this time is an early stage of the installation, the optical cable is still short, and the propulsive force required to pull in the optical cable is small.

In the present invention, since the optical cable is made lighter, it can be pulled into the sheath tube over a long distance sufficiently and reliably by the driving force of the pressure receiving head.

[0022]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is a conceptual diagram showing an embodiment of an apparatus to which the optical cable pneumatic feeding method of the present invention is applied.

The difference between the present invention and the conventional method is that the bending rigidity of the optical cable to be laid is particularly small and light.

As a specific example of the structure of the optical cable for realizing the small bending rigidity and the light weight, it has already been proposed for an underground cable pulling method, and the following four proposals can be applied as they are.

(1) By replacing the tension member built in the center of the conventional optical cable with a single steel wire or a steel stranded wire with an FRP fiber bundle, the bending rigidity can be reduced and the weight can be reduced.

(2) By foaming the inner layer of the slot rod of the conventional optical cable from solid polyethylene, the bending rigidity can be reduced and the weight can be reduced.

(3) The bending rigidity can be reduced by making a cut in the slot wall of the conventional optical cable slot rod (Japanese Patent Application No. 10-230710).

(4) The bending rigidity can be reduced by corrugating the PE sheath of a conventional optical cable (Japanese Patent Application No. 10-230711).

A method of laying a curved long distance using an optical cable having a structure shown in (1) to (4) and having a small bending rigidity and a light weight will be described with reference to FIG.

The drum 1 is supported by a jack 2.
The optical cable 3 is taken out by the caterpillar 4, fed out of the drum 1, and introduced into the pressure feed head 5. A pressure receiving head 7 that generates a propulsive force when receiving air pressure is attached to the tip of the optical cable 3. The optical cable 3 is pneumatically fed into the sheath tube 6 by supplying high-pressure air into the pumping head 5.

Here, in the present invention, since the optical cable 3 is made lighter, it can be pulled in sufficiently with the propulsive force of the pressure receiving head 7. Optical cable 3
When the cable length is increased to some extent and the propulsive force generated in the pressure receiving head 7 alone is not sufficient, the optical cable 3 reaches the portion where the air flow gradually increases. In addition, since the weight of the optical cable 3 is reduced, the optical cable 3 can be easily mounted on the airflow. As a result, the optical cable 3 itself generates a propulsive force.

The optical cable 3 always has a sufficient thrust as the sum of the thrust generated in the pressure receiving head and the thrust generated in the optical cable itself regardless of whether the length of the optical cable inserted into the sheath tube 6 is short or long. And long-distance laying is possible. Moreover, even if there is a curved portion having a small curvature in the middle, unlike the conventional method, the bending rigidity of the optical cable 3 is made particularly small, so that the optical cable 3 can pass through with a small propulsion resistance, and as a result, the curved long distance can be laid. Can be realized.

As described above, in the conventional method, the caterpillar 4
And the propulsion force generated by the high-pressure air flow is used to lay the optical cable 3 and the sheath tube 6 together. On the other hand, the present invention differs greatly in that the optical cable 3 is laid in the sheath tube 6 only by the action of the high-pressure air flow. For this reason, as the pumping device, the conventional method and the method of the present invention are the same, but the caterpillar 4
The functions of are very different.

That is, in the conventional method, the function of the caterpillar 4 is to push the optical cable 3 from the rear, whereas in the method of the present invention, the function of the caterpillar 4 is rather to decelerate by applying a brake to the optical cable 3. The main function is to control the optical cable 3 drawn into the sheath tube 6 uncontrolled by the action of the high-pressure air flow at a constant speed.

In the above, in the conventional method, it is an essential condition that the bending rigidity of the optical cable 3 to be laid is large, whereas in the present invention, the optical cable 3 can be laid even if the bending rigidity of the optical cable 3 is small. As a result, an effect is obtained in which the propulsion resistance in a curved portion having a small curvature is significantly reduced.

Since an optical cable having a low bending rigidity and a light weight is used as the optical cable to be laid in the sheath tube, an air-pressure feeding method capable of laying a long curve with a smaller curvature than the conventional method can be realized.

[0038]

In summary, according to the present invention, the following excellent effects are exhibited.

It is possible to realize an optical cable pneumatic feeding method capable of securely laying an optical cable even in a long distance sheath tube route having many curves including a small curvature.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram showing an embodiment of an apparatus to which the optical cable pneumatic feeding method of the present invention is applied.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Drum 2 Jack 3 Optical cable 4 Caterpillar 5 Pumping head 6 Sheath tube 7 Pressure receiving head

Claims (5)

[Claims] 1. A pressure receiving head that generates a propulsive force when receiving air pressure is attached to a tip of an optical cable, and the optical cable is sandwiched between upper and lower caterpillars and inserted into a sheath tube by a driving force of the caterpillar. An optical cable pneumatic method for laying an optical cable by supplying high-pressure air into a pipe, wherein an optical cable having low bending rigidity and light weight is air-pneumatically fed. 2. The optical cable according to claim 1, wherein the tension member is F.
The optical cable pneumatic feeding method according to claim 1, which is an RP fiber bundle. 3. The optical cable pneumatic method according to claim 1, wherein the inner layer of the slot rod of the optical cable is made of polyethylene foam. 4. The optical cable pneumatic feeding method according to claim 1, wherein a cut is made in a slot wall of the slot rod of the optical cable. 5. The optical cable pneumatic feeding method according to claim 1, wherein the PE sheath of the optical cable is corrugated.