JP3501043B2 - Optical cable gas pressure method - Google Patents

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 for inserting an optical cable into a sheath tube by utilizing the flow of gas such as air or nitrogen gas, and particularly to a method of optical cable at a relay connection between 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 installed in a sheath pipe made of polyethylene or steel in order to protect the optical cable from external pressure and water.

The sheath tube is usually laid at a length of 250 m or less, that is, at intervals of handholes.

As one of the laying methods for the above-mentioned sheath tube, there is known a gas pressure feeding method in which an optical cable is inserted into the sheath tube by utilizing a flow of gas such as air. Recently, it is possible to lay a long-distance optical fiber cable. It is in the limelight because it is not subject to excessive tension.

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 an optical cable 3 is fed into a chamber 23 in the head from a drive wheel 21 which is a feeding and holding means, and at the same time, a high pressure is applied. By feeding air from the supply port 22, the optical cable 3 is pressure fed into the sheath tube 6. The pressure feed head 5 has a contact-type seal portion 24 between it and the optical cable 3.

When the laying distance of the optical cable 3 is relatively short, a propulsive force is given by the drive wheel 21 which is a feeding and gripping means, and the optical cable 3 advances in the sheath tube 6 from left to right. When the laying distance becomes long, the frictional force between the optical cable 3 and the inner surface of the sheath tube 6 becomes large, and the cable cannot be advanced only by the pushing force by the drive wheel 21, and the cable is stopped. Therefore, when the laying distance becomes long, high-pressure air is supplied from a compressor (not shown) into the sheath pipe 6 through the high-pressure air sealing pressure-feeding head 5 in the pressure-feeding device, and air from the left to the right in FIG. Optical cable 3 due to the high-speed flow of
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 this optical cable pneumatic feeding method, when the optical cable 3 is carried on the high-pressure air flow, a propulsive force is generated over the entire length, and it is possible to lay the optical cable 3 in the sheath tube 6 for a long distance (500 m or more). Become.

[0008]

However, there is a problem that the laying length of the sheath tube 6 is usually shorter than the laying length by the pneumatic feeding method even if the laying can be performed over a long distance of 500 m or more. . That is, the sheath tube 6 is usually 250 m
In many cases, the length is set shorter than that, that is, the handholes 9 are installed at intervals.

Therefore, when laying over a distance longer than the above handholes, for example, 500 m or more, it is necessary to connect the sheath pipes 6 to each other in several handholes according to the laying length. is there.

The relay connection of this sheath pipe has a structure that can be completely removed because it is necessary to take an extra length of the cable in the handhole in preparation for future branch connection etc. after the optical cable is laid by pneumatic feeding. Must-have.

A structure shown in FIG. 3 is conceivable as a structure of the relay connection portion which satisfies such requirements. That is, first, since the sheath tube 6 is normally projected in the handhole by 200 mm or more, the sheath tube 6 is cut at an appropriate position, and the edge inside the cut is
Chamfer with a reamer or the like in order to prevent catching when the laying cable tip 7 passes. Next, pressure-resistant rubber hose 11
Is covered on each sheath tube 6 and is fixed by tightening with a hose clamp 10. At this time, the hose clamp 10 is one that can be completely disassembled in half.

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

As described above, the relay connecting portion of the sheath tube has a structure that is easy to install and dismantle in order to efficiently perform the optical cable pneumatic feeding method, and is flexible even when the relay sheath tubes 6 are not in a straight line. Pressure resistant rubber hose 1
By bending 1 into an S-shape, the structure allows relay connection between the sheath pipes.

However, the method of performing the relay connection between the sheath pipes by the combination of the pressure-resistant rubber hose 11 and the hose clamp 10 as described above has the advantage of being easy to mount and dismantle and to be able to flexibly deal with it. 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 is generated. Therefore, when performing long-distance pressure feed including many relay connection parts 8 in the case where the relaying sheath pipes are not in a straight line as shown in FIG. 3, the laying cable tip 7 is caught in the step and the laying cable is temporarily propelled. Will stop at. Once the propulsion of the laying cable is stopped, the friction coefficient between the laying cable and the inner surface of the sheath tube until then changes from dynamic friction to static friction, and the friction force increases rapidly.
It becomes difficult to restart. Even after the cable tip has passed through the relay connection part, the optical cable 3 has the pressure-resistant rubber hose 1
Since the optical cable 3 is in constant contact with the inner surface and the optical cable 3 has a certain degree of rigidity and is difficult to bend, this is one of the causes for increasing the propulsion resistance of the laid cable. As a result, in the pumping route that contains many connections between sheath tubes,
It will be difficult to pump air over a long distance.

The present invention solves the above problems, prevents the tip of the laying cable from being caught at the relay connection between the sheath tubes, and greatly reduces the cable propulsion resistance even after the tip of the laying cable has passed. The object of the present invention is to realize an optical cable gas pressure-feeding method that enables long-distance pressure-feeding, even when a large number of relay connection portions between sheath tubes are included.

[0016]

In order to achieve the above object, the present invention is an optical cable gas pressure feeding method in which an optical cable is inserted into a sheath tube by utilizing the flow of gas, and the sheath tubes are relay-connected by a hose, set to the hose, so as not to cause a difference in level between the sleeve pipe, Ri formed material having a small frictional resistance than the hose, the spiral slit
A beam inner guide is provided to facilitate insertion of the optical cable at the relay connection between the sheath tubes (claim 1).

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

The point of the present invention is to use a hose such as a rubber hose for relay connection of the sheath pipe, and insert a polyethylene pipe having a spiral slit, for example, into the hose, and use this as a smooth inner guide. There is something I did.

As the inner guide, it is preferable to use one having substantially the same size as that of the sheath tube so that the step between the sheath tube and the inner diameter of the rubber hose can be filled. It is preferable that the inner guide has such a length that the end surfaces of the sheath pipes to be relay-connected are connected with a certain allowance.

The inner guide is provided with a spiral slit so that the inner guide can be bent easily so as not to impair the flexibility which is an advantage of the rubber hose.
By providing the spiral slit, the inner guide can be easily removed from the cable in the gap of the slit when the inner guide is removed after the cable pressure feeding.

In the present invention, since the inner guide can fill the step between the inner diameter of the sheath tube and the inner diameter of the hose, it is possible to prevent the leading end of the laying 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 small frictional resistance such as a polyethylene tube, so that the frictional resistance generated is much smaller than that in the case where the hose is in contact with the hose. Therefore, it is possible to perform long-distance pressure feeding even in pressure 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 a material having a smaller frictional resistance than the hose,
Other than polyethylene pipes may be used. Further, the angle, width, and number of slits of the inner guide are not limited and can be arbitrarily set.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to FIGS. 1 and 2 by taking a pneumatic method for cable laying using high pressure air as an example.

First, in the premised pumping device, as described with reference to FIG. 4, the pumping head 5 is connected to the sheath tube 6 for laying the cable, and the chamber 23 in the head is fed into the chamber 23 from the feeding gripping means to the optical fiber cable. The optical cable 3 is sent through the supply port 22, and the optical cable 3 is sent under pressure into the sheath tube. However, a pair of caterpillars 4 are used here as the feed gripping means instead of the drive wheel 21. The pressure feed head 5 has a contact-type seal portion 24 between it and the optical cable 3.

In FIG. 2, the drum 1 is axially supported by the jack 2, and the optical cable 3 is taken out by the caterpillar 4 and fed out from the drum 1, and introduced into the sheath tube 6 through the pressure feeding 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 propulsive force is extremely effectively transmitted to the tip, and the optical cable 3 can be propelled to a long distance.

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

Here, when the above-mentioned long distance laying refers to a laying length of 500 m or more, the sheath pipe 6 is laid with a shorter installation interval of the handholes 9, that is, a length of 250 m or less. ing. Therefore, the sheath pipe 6 is relayed and connected in some handholes 9 in accordance with the long distance laying length. In FIG. 2, reference numeral 8 indicates this relay connection unit.

FIG. 1 shows the details of the structure of the relay connection section 8. In exactly the same manner as described with reference to FIG. 3, the sheath pipes 6 projecting into the handholes 9 are cut, and the respective sheath pipes are covered with one end and the other end of a flexible pressure-resistant rubber hose 11 and a hose clamp. Tighten and fix with 10. At this time, the hose clamp 10 is one that can be completely disassembled in half.

With this structure, the hose clamp 10 is disassembled after the optical cable 3 is pneumatically fed,
The pressure-resistant rubber hose 11 can be cut with a knife or the like to completely remove the relay connection material. However, by simply connecting the sheath pipes together by using a combination of a pressure-resistant rubber hose and a hose clamp, it is easy to install and dismantle and can be handled flexibly. Will occur.

Therefore, in the pressure-resistant rubber hose 11 used for the relay connection of the sheath pipe, as the inner guide 12, a sheath pipe (polyethylene pipe) made of polyethylene having spiral slits 13 is provided. For the polyethylene pipe of the inner guide 12, use a polyethylene pipe having almost the same size as the sheath pipe 6 and a length that allows the end faces of the sheath pipe 6 for relay connection to be connected with a certain allowance. There is.

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

Next, when the laying cable tip 7 approaches the relay connection between the sheath tubes that are not in a straight line, the present invention can prevent the cable from stopping and reduce the propulsion resistance. I will explain.

In the case of FIG. 1, a flexible pressure-resistant rubber hose 1
By bending 1 into an S-shape, it is possible to make a relay connection between sheath pipes that are not in a straight line.

When the distal end 7 of the laying cable reaches the relay connecting portion 8 of the sheath pipe 6 which is bent in the S shape, it is rubbed against the inner guide 12 with the first bending. Next, in the second bending, the inner guide 12 is rubbed further. Then, the greater the rigidity of the optical cable 3, the greater the frictional resistance caused thereby. Since the rigidity of the optical cable 3 needs to be increased to a certain extent in order to perform the long-distance pressure laying in the optical cable pneumatic feeding method, there is a possibility that the propulsive force of the laying cable may be significantly reduced at such a bent portion. .

However, in comparison with the rubber hose 11 shown in FIG. 3, the inner guide 12 in the relay connection portion 8 shown in FIG.
Since the polyethylene pipe 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 propulsion resistance.

The inner guide 12 and the sheath tube 6 have almost the same size and have no gap. That is, since the inner guide 12 fills the step between the inner diameters of the sheath tube 6 and the rubber hose 11, the optical cable 3 serving as a laying cable.
Is inserted into the next sheath tube 6 without the tip 7 of the laying cable being caught. Further, since the optical cable 3 is in contact with the polyethylene pipe even after the cable tip has passed, a much smaller frictional resistance is generated as compared with the case where the optical cable 3 is in contact with the rubber hose 11, and therefore, the relay connection part 8 is included in large numbers. Even when the cable is pressure-fed to the sheath tube 6, long-distance pressure-feeding can be achieved.

After pneumatically feeding the optical cable 3, the hose clamp 10 is disassembled, and the pressure-resistant rubber hose 11 is cut with a knife or the like and completely removed. Regarding the inner guide 12, the gap of the slit 13 is forcibly and elastically widened, and the inner guide 12 is removed from the optical cable 3 through the gap of the slit 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 invention, the sheath pipes are relay-connected by a hose, and the friction resistance is smaller than that of the hose so that a step is not formed between the sheath pipes and the sheath pipe. Since an inner guide made of material was provided to facilitate the insertion of the optical cable at the relay connection between the sheath tubes, the optical cable is laid by the pneumatic method to the sheath tube including the relay connection between the sheath tubes that are not in a straight line. Even if
The inner guide of the relay connection portion can prevent a large increase in propulsion resistance, and thus enables long-distance pressure feeding of the optical cable as compared with the conventional method.

(2) Further, according to the invention of claim 2, since the inner guide is made of a polyethylene pipe having a spiral slit, the inner guide itself is a sheath pipe made of polyethylene for cable laying. It can be used as an inner guide by processing, and can be easily removed from the optical cable in the slit gap, so once manufactured it can be used many times. As a result, there is an effect that the optical cable can be installed at an extremely low cost.

[Brief description of 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 pipe in an optical cable gas pressure feeding 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 which is a premise of the present invention.

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

[Explanation of symbols]

3 optical cable 4 caterpillar 5 pumping head 6 sheath tube 7 Installation cable tip 8 Relay connection 9 Hand holes 11 Pressure-resistant rubber hose 12 Inner guide 13 slits

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Claims (2)

(57) [Claims] 1. In an optical cable gas pressure feeding method in which an optical cable is inserted into a sheath tube by utilizing a gas flow, the sheath tubes are relay-connected by a hose, and a step is not formed between the sheath tube and the sheath tube. provided way, Ri formed material having a small frictional resistance than the hose, the spiral slit
An optical cable gas pressure feeding method characterized in that an inner guide is provided to facilitate insertion of an optical cable at a relay connection between sheath tubes. 2. The optical cable gas pressure feeding method according to claim 1, wherein the inner guide is made of a polyethylene pipe having a spiral slit.