JP2001128329A - Optical cable gas pressure feeding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical cable gas pressure feeding method, which utilizes gas flow to feed an optical cable through a sheath tube and can reduce cable feeding resistance produced, at a junction between the sheath tubes to enable the long distance pressure feeding installation of the optical cable. SOLUTION: Sheath tubes 6 are connected to each other with a hose 11. An inner guide 12 made of material which has a smaller friction resistance than that of the material of the hose 11 is provided in the hose, so as to eliminate steps between the sheath tubes 6 and the hose to easily feed an optical cable 3 through the junction 8 between the sheath tubes.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical cable gas pressure feeding method in which an optical cable is inserted into a sheath tube by utilizing a gas flow such as air or nitrogen gas, and more particularly, to an optical cable at a junction between the sheath tubes. The present invention relates to an optical cable gas pressure feeding method that facilitates insertion.

[0002]

2. Description of the Related Art When a communication optical cable is buried underground, it is generally laid in a sheath tube made of polyethylene or steel to protect the optical cable from external pressure, water, and the like.

[0003] The sheath tube is usually laid at a length of 250 m or less, that is, at an interval between handholes.

[0004] As one of the methods of laying in the sheath tube, there is known a gas pressure feeding method in which an optical cable is inserted into the sheath tube by using a flow of gas such as air. It is in the limelight from where excessive tension does not act.

A conventional optical cable pneumatic feeding method will be described with reference to FIG. In the pneumatic feeding method, as shown in FIG. 4, a pressure feeding head 5 is connected to a sheath pipe 6 for laying a cable, and the optical cable 3 is fed into a chamber 23 in the head from a driving wheel 21 serving as a feeding and holding means. The optical cable 3 is pressure-fed into the sheath tube 6 by sending air from the supply port 22. The pressure feed head 5 has a contact-type seal portion 24 between the head 5 and the optical cable 3.

When the installation distance of the optical cable 3 is relatively short, a driving force is applied by a driving wheel 21 which is a feeding gripping means, and the optical cable 3 advances inside the sheath tube 6 from left to right. If the laying distance is long, the frictional force between the optical cable 3 and the inner surface of the sheath tube 6 increases, and the cable cannot move forward only by the pushing force by the drive wheel 21 and stops. Therefore, when the laying distance becomes long, high-pressure air is supplied from a compressor (not shown) into the sheath tube 6 via the high-pressure air sealing pressure-feeding head 5 in the pressure-feeding device, and air from left to right in FIG. Cable 3
To reduce the frictional resistance with the sheath tube 6 and generate a propulsive force in the optical cable 3 through the frictional force between the optical cable 3 and air.

According to the optical cable pneumatic feeding method, the optical cable 3 rides on the high-pressure air flow, so that a propulsive force is generated over the entire length and the optical cable 3 can be laid in the sheath tube 6 over a long distance (500 m or more). Become.

[0008]

However, even if the installation by the above-mentioned pneumatic feeding method can be installed over a long distance of 500 m or more, there is a problem that the installation length of the sheath tube 6 is usually shorter than this. . That is, the sheath tube 6 is usually 250 m
Or, in many cases, the cable is laid at a length shorter than that, that is, at an installation interval of the handhole 9.

Therefore, when laying a long distance exceeding the installation interval of the handholes, for example, 500 m or more, it is necessary to connect the sheath tubes 6 in some handholes in accordance with the length of the laying. is there.

[0010] The relay connection of the sheath tube has a structure in which the optical cable is laid by pneumatic pressure, and it is necessary to take extra length of the cable in the handhole in preparation for a future branch connection. Must-have.

FIG. 3 shows an example of a structure of the relay connection part satisfying such requirements. That is, first, the sheath tube 6 is cut out at an appropriate position because the sheath tube 6 is usually 200 mm or more in the handhole.
Chamfering is performed with a reamer or the like to prevent the cable from being caught when passing through the laying cable tip 7. Next, the pressure-resistant rubber hose 11
Is put on each sheath tube 6 and tightened and fixed with a hose clamp 10. At this time, a hose clamp 10 that can be completely disassembled in half is used.

After pneumatic feeding of the optical cable 3, the hose clamp 10 is disassembled, the pressure-resistant rubber hose 11 is cut with a knife or the like, and the relay connection material is completely removed.

As described above, the relay connection portion of the sheath tube has a structure that can be easily attached and disassembled in order to efficiently perform the optical cable pneumatic feeding method, and is flexible even when the sheath tubes 6 to be relayed are not straight. Pressure resistant rubber hose 1
By bending 1 into an S-shape, a structure that enables the relay connection between the sheath tubes is provided.

[0014] However, the method in which the sheath connection between the sheath tubes is performed by the combination of the pressure-resistant rubber hose 11 and the hose clamp 10 as described above has an advantage that it can be easily and flexibly installed and disassembled, but has the advantage. Due to the shape, the inner diameter of the sheath tube 6 and the inner diameter of the rubber hose 11 are different, and a step occurs. Therefore, in the case of performing long-distance pressure feeding including many relay connection portions 8 when the sheath tubes to be relayed are not in a straight line as shown in FIG. 3, the laying cable tip 7 is caught by the step, and the laying cable is temporarily propelled. Will stop. Once the propulsion of the laid cable stops, the friction coefficient between the laid cable and the inner surface of the sheath tube changes from dynamic friction to static friction, and the friction force increases rapidly,
Restarting is difficult. Also, even after the end of the cable has passed through the relay connection portion, the optical cable 3 can be connected to the pressure-resistant rubber hose 1.
Since the optical cable 3 is constantly in contact with the inner surface and the optical cable 3 has a certain degree of rigidity and is hard to bend, this is one of the causes for increasing the propulsion resistance of the laid cable. As a result, in the pumping route including many connections between the sheath tubes,
Long-distance pneumatic pumping would be difficult.

[0015] The present invention solves the above-mentioned problems, and prevents the tip of the laid cable from being caught at the junction between the sheathed tubes, and greatly reduces the cable propulsion resistance even after the tip of the laid cable passes. It is another object of the present invention to realize an optical cable gas pressure feeding method that enables long-distance pressure feeding even when a large number of relay connections between sheath tubes are included.

[0016]

In order to achieve the above object, the present invention relates to an optical cable gas pressure construction method in which an optical cable is inserted into a sheath tube by using a gas flow. An inner guide made of a material having a smaller frictional resistance than that of the hose is provided in the hose so as to prevent a step from being formed between the hose and the sheath tube, thereby facilitating the insertion of the optical cable at the junction between the sheath tubes. (Claim 1).

In the optical cable gas pressure feeding method according to the present invention, it is preferable that the inner guide is formed of a polyethylene pipe having a spiral slit.

The gist of the present invention is that a hose such as a rubber hose is used for relay connection of a sheath tube, and a polyethylene tube having a spiral slit, for example, is inserted into the hose, and this is connected to a smooth inner guide. I did it.

The inner guide preferably has substantially the same size as the sheath tube, so that the step between the inner diameter of the sheath tube and the inner diameter of the rubber hose can be filled. The inner guide preferably has a length that connects the end faces of the sheath tubes to be connected and connected with some allowance.

The inner guide is provided with a spiral slit to make the inner guide easy to bend, so that the flexibility, which is an advantage of the rubber hose, is not impaired.
By providing the spiral slit, the inner guide can be easily detached from the cable in the gap between the slits when the inner guide is removed after the cable pressure-feeding is installed.

In the present invention, the step of the inner diameter of the sheath tube and the hose can be filled by the inner guide, so that it is possible to prevent the tip of the laid cable from being caught at the relay connection portion and stopping the cable propulsion. . Further, even after the tip has passed, the optical cable is in contact with the inner guide having a low frictional resistance such as a polyethylene tube, so that a much smaller frictional resistance is generated than in the case where the optical cable is in contact with the hose. Therefore, it is possible to perform long-distance press-feeding even in the press-feeding of an optical cable to a sheath tube including many relay connections.

In the present invention, the material of the inner guide may be any material having a smaller frictional resistance than the hose.
Other than a polyethylene tube may be used. The angle, width and number of the slits of the inner guide can be arbitrarily determined without any restrictions.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 1 and 2 by taking an example of an air pressure feeding method for laying cables using high-pressure air.

First, as described with reference to FIG. 4, the presumptive feeding apparatus connects the pumping head 5 to the sheath pipe 6 for laying a cable, and feeds the optical fiber cable from the feeding and holding means to the chamber 23 in the head. The optical cable 3 is fed into the sheath tube by feeding high-pressure air from the supply port 22 while feeding the optical cable 3. However, here, a pair of tracks 4 is used instead of the drive wheel 21 as the feeding gripping means. The pressure-feeding head 5 has a contact-type seal portion 24 between the pressure-feeding head 5 and the optical cable 3.

In FIG. 2, a drum 1 is supported by a jack 2 and an optical cable 3 is taken out by a caterpillar 4 and is fed out of the drum 1 and introduced into a sheath tube 6 via a pressure feed head 5. Further, when the optical cable 3 is pushed in by the caterpillar 4, since the bending rigidity of the optical cable 3 is large, the driving force is transmitted to the tip very effectively, and the optical cable 3 can be propelled far.

After pushing in an appropriate length, the pressure feed head 5
When high-pressure air is supplied from a compressor (not shown), high-pressure air is generated in the sheath tube 6. When the optical cable 3 rides on the high-pressure air flow, a propulsive force is generated over the entire length, and the optical cable 3 can be laid in the sheath tube 6 over a long distance.

Here, assuming that the long-distance laying refers to a laying length of 500 m or more, the sheath tube 6 is laid at a shorter installation interval of the handhole 9, that is, 250 m or less. ing. Therefore, the sheath tube 6 is relayed and connected in several handholes 9 in accordance with the long distance installation length. In FIG. 2, reference numeral 8 denotes this relay connection unit.

FIG. 1 shows the details of the structure of the relay connection section 8. In the same manner as described with reference to FIG. 3, the sheath tube 6 protruding into the hand hole 9 is cut, and one end and the other end of a flexible pressure-resistant rubber hose 11 are put on each of the sheath tubes, and a hose clamp is provided. Tighten and fix with 10. At this time, a hose clamp 10 that can be completely disassembled in half is used.

With this configuration, the hose clamp 10 is disassembled after the pneumatic feeding of the optical cable 3,
The pressure-resistant rubber hose 11 can be cut with a knife or the like to completely remove the relay connection material. However, simply connecting the sheath tubes with each other with a combination of a rubber hose for pressure resistance and a hose clamp can be easily and flexibly installed and disassembled, but the inner diameter of the sheath tube and the inner diameter of the rubber hose are different due to the shape, and there is a step difference. Will happen.

Therefore, in the pressure-resistant rubber hose 11 used for the relay connection of the sheath tube, a sheath tube (polyethylene tube) made of polyethylene with a slit 13 spirally provided therein is provided as the inner guide 12. As the polyethylene tube of the inner guide 12, use a tube of approximately the same size as the sheath tube 6 and a length that can connect the end surfaces of the sheath tubes 6 to be connected with a certain margin. I have.

The inner guide 12 is provided with a slit 13 in a spiral shape so that the inner guide 12 can be bent freely without substantially changing its diameter. Therefore, the flexible hose 11 can freely follow the bending of the pressure-resistant rubber hose 11 and does not impair the flexibility of the pressure-resistant rubber hose 11.

Next, when the laid cable tip 7 comes to the junction between the non-linear sheath tubes, the present invention can prevent the cable propulsion from stopping and reduce the propulsion resistance in any manner. Is explained.

In the case of FIG. 1, a flexible pressure-resistant rubber hose 1 is used.
By bending 1 into an S-shape, a relay connection between sheath tubes that are not linear can be made possible.

When the laying cable tip 7 reaches the relay connection portion 8 of the sheath tube 6 bent in an S-shape, it is rubbed against the inner guide 12 in the first bending. Next, in the second bend, the inner guide 12 is further rubbed. Then, the higher the rigidity of the optical cable 3 is, the higher the frictional resistance becomes. The rigidity of the optical cable 3 needs to be increased to some extent in order to perform the long-distance press-feeding in the optical cable pneumatic feeding method, so that the propulsive force of the installed cable may be significantly reduced in such a bent portion. .

However, the inner guide 12 in the relay connection portion 8 in FIG. 1 is different from the rubber hose 11 in FIG.
Since a polyethylene tube having a relatively small frictional resistance is used, the optical cable 3 can be propelled along the bend of the inner guide 12 without a large increase in the propulsion resistance.

The inner guide 12 and the sheath tube 6 have substantially the same size and have no gap. That is, since the inner guide 12 fills the step of the inner diameter of the sheath tube 6 and the rubber hose 11, the optical cable 3, which is a laid cable,
Is inserted into the next sheath tube 6 without the cable end 7 being hooked. Further, since the optical cable 3 is still in contact with the polyethylene tube even after the cable end has passed, the frictional resistance is much smaller than in the case where the optical cable 3 is in contact with the rubber hose 11. Also in the cable pressure feeding to the sheath tube 6, the long distance pressure feeding laying can be achieved.

After pneumatic feeding of the optical cable 3, the hose clamp 10 is disassembled, and the pressure-resistant rubber hose 11 is cut off with a knife or the like and completely removed. With respect to the inner guide 12, the gap between the slits 13 is forcibly and elastically widened, and is removed from the optical cable 3 through the gap between the slits 13. Therefore, the inner guide 12 can be used any number of times.

[0038]

As described above, according to the present invention, the following excellent effects can be obtained.

(1) According to the first aspect of the present invention, the sheath tubes are connected to each other by a hose, and the frictional resistance is smaller than that of the hose so that a step is not formed between the sheath tubes and the sheath tube. Since an inner guide made of a material is provided to facilitate the insertion of the optical cable at the junction between the sheath tubes, the optical cable is laid by a pneumatic feeding method on the sheath tube including the non-linear sheath tube relay connection. Even if
A large increase in propulsion resistance can be prevented by the inner guide of the relay connection portion, and therefore, long-distance pressure feeding of an optical cable longer than that of the conventional method can be performed.

(2) According to the second aspect of the present invention, the inner guide is formed of a polyethylene pipe having a spiral slit. Therefore, the inner guide itself is a polyethylene cable sheathing pipe. By being processed, it can be used as an inner guide, and can be easily removed from the optical cable in the gap of the slit, so that once it is manufactured, it can be used many times. As a result, there is an effect that the optical cable can be laid very inexpensively.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a state in which an optical cable passes through a relay connection portion of a sheath tube in an optical cable gas pressure method of the present invention.

FIG. 2 is a conceptual cross-sectional view showing a state in which an optical cable is pressure-fed to a sheath tube including a plurality of relay connection parts by the optical cable gas-pressure feeding method of the present invention.

FIG. 3 is a cross-sectional view showing a configuration of a relay connecting portion between sheath tubes as a premise of the present invention.

FIG. 4 is a conceptual cross-sectional view showing a configuration of a conventional pneumatic feeding device.

[Explanation of symbols]

 REFERENCE SIGNS LIST 3 optical cable 4 caterpillar 5 pressure feed head 6 sheath tube 7 tip of laid cable 8 relay connection part 9 hand hole 11 rubber hose for pressure resistance 12 inner guide 13 slit

Claims (2)

[Claims] In an optical cable gas pressure feeding method in which an optical cable is inserted into a sheath tube using a gas flow, the sheath tubes are connected to each other by a hose so that no step is formed between the sheath tube and the sheath tube. Thus, an optical cable gas pressure feeding method characterized in that an inner guide made of a material having a smaller frictional resistance than a hose is provided to facilitate insertion of an optical cable at a junction between sheath tubes. 2. The optical cable gas pressure feeding method according to claim 1, wherein said inner guide comprises a polyethylene pipe having a spiral slit.