JPH0735961A - Optical fiber cable for pneumatic feeding method - Google Patents

Abstract

PURPOSE:To improve press feeding characteristics by specifying the bending rigidity of the cable to a specific value, thereby making it possible to well continue press feeding even in the bent part of a pipe in an initial period of press feeding. CONSTITUTION:This optical fiber cable 8 is formed by assembling coated optical fibers 4 coated with UV curing resins and an intervening cord 3 and is coated and formed with a jacket layer 2 consisting of a silicone resin on the outer peripheral side thereof. Further, the surface of the jacket layer 2 is coated and formed with the outermost layer 1 consisting of low-density polyethylene. The bending rigidity thereof is specified to >=300 to <=400N.mm<2>. As a result, the optical fiber cable is well press fed in the pipe without being pushed back to an inlet side in spite of the inlet pressure in the pipe. The friction force from the inside surface of the pipe is minimized against the press feeding force by the air flow and the optical cable is well press fed even at a curved route.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber cable laid in a pipe by a pneumatic feeding method.

[0002]

2. Description of the Related Art The pneumatic feeding method is a method of passing an optical fiber cable through a pipe by the force of air (hereinafter referred to as "pressure feeding").
It is a construction method. That is, as shown in FIG. 4, compressed air is sent from the one end side into the already installed pipe 6 by the pressure feeding device 7, and the optical fiber cable 8 is pressure fed along with the air flow generated in the pipe 6.

Usually, the optical fiber cable 8 used in the pneumatic feeding method has a small cable mass so that the optical fiber cable 8 can be smoothly fed under pressure in the pipe 6, and has a large surface area so as to receive a large amount of air feeding force. It is necessary. Conventionally, as a typical configuration of the optical fiber cable 8 for pneumatic feeding method, six optical fiber core wires coated with an ultraviolet curable resin having an outer diameter of 0.25 mm and one intervening cord are gathered, and the outer peripheral side thereof is provided. In some cases, after coating nylon, it is further coated with foamed polyethylene to increase the surface area.

[0004]

As described above, for the optical fiber cable 8 for the pneumatic feeding method, it has been attempted to make the cable 8 itself light and thick in order to improve the pressure feeding characteristics, but it is still a cable. The rigidity of No. 8 was not taken into consideration, and there was a case where the pipe 6 could not be pumped. That is, when the optical fiber cable 8 having low rigidity is pressure-fed, the tip end surface of the optical fiber cable 8 is pushed back by the air pressure (inlet pressure) at the inlet of the pipe 6 near the pressure-feeding device 7, and the cable 8 is bent. Cannot be pumped. On the contrary, when the optical fiber cable 8 having high rigidity is pressure-fed, the straight line portion of the pipe 6 can be pressure-fed, but at the curved portion, the cable 8 is strongly pressed against the inner surface of the pipe 6 and cannot be pressure-fed.

An object of the present invention is to solve the above-mentioned drawbacks of the prior art and to provide an optical fiber cable for a pneumatic feeding method capable of significantly improving the pressure feeding characteristics.

[0006]

In order to achieve the above object, the present invention is an optical fiber cable laid in a pipe by a pneumatic feeding method, the cable bending rigidity of which is 300 N · mm ² or more and 400 N or more.・ It is less than mm ² .

Here, the above-mentioned optical fiber cable for pneumatic feeding method may be any one in which at least one optical fiber core wire is assembled and the outer peripheral side thereof is covered.

[0008]

According to the present invention, when the bending rigidity of the optical fiber cable for the pneumatic feeding method is examined, the value is 300 to 4
It was made with the finding that the pressure-feeding property can be greatly improved by keeping the pressure within the range of 00 N · mm ² . In other words, it was confirmed that if the bending rigidity of the optical fiber cable laid by the pneumatic feeding method is 300 N · mm ² or more and 400 N · mm ² or less, good pressure feeding can be continued at the initial stage of pressure feeding and at the bent portion of the pipe. .

In this case, when the bending rigidity of the optical fiber cable is less than 300 N · mm ² , the tip end surface of the optical fiber cable is pushed back toward the entrance by the air pressure (inlet pressure) near the entrance in the pipe. Deflection occurs and it becomes impossible to pump. If the bending rigidity is 300 N · mm ² or more, the rigidity of the optical fiber cable is superior to the inlet pressure, and therefore the optical fiber cable can be pumped without being pushed back.

In addition, the bending rigidity of the optical fiber cable is 4
If it exceeds 00 N · mm ² , the optical fiber cable is pressed against the inner surface of the pipe by the curved portion of the pipe and receives a large frictional force, making it impossible to pump. When the bending rigidity is 400 N · mm ² or less, the pressure-feeding force acting on the optical fiber cable is superior to the frictional force received from the inner surface of the pipe in the curved portion of the pipe, and the pressure-feeding is possible.

[0011]

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

First, six types of optical fiber cables A to F having the same outer diameter and mass but different bending rigidity were manufactured as the optical fiber cables for the pneumatic feeding method.

The upper column of Table 1 below shows the configuration of these optical fiber cables A to F.

[0014]

[Table 1]

As shown in FIG. 1, the optical fiber cable A includes six optical fiber core wires 4 coated with an ultraviolet curable resin having an outer diameter of 0.25 mm and one interposing cord 3 (diameter 0.25 mm). After assembling, a jacket layer 2 made of silicone resin was formed on the outer peripheral side to form a diameter of 1.0 mm, and 40% foamed low density polyethylene (hereinafter referred to as “LDPE”) was formed on the jacket layer 2. The outermost layer 1 is formed by coating. Young's modulus of silicone resin (jacket layer) 2 is 10 N / mm ² , LDPE (outermost layer)
The Young's modulus of No. 1 was fully 200 N / mm ² , and the bending rigidity of the entire optical fiber cable A was 200 N · mm ² .

In the optical fiber cable B, the material of the outermost layer 1 in the above-mentioned optical fiber cable A is the high density polyethylene having a sufficient Young's modulus and 700 N / mm ² (hereinafter referred to as "HDP
"E"), and the cable bending rigidity is 300 N · mm ² .

The optical fiber cable C is obtained by changing the material of the jacket layer 2 in the optical fiber cable B to an ultraviolet curable resin (hereinafter referred to as "UV") having a Young's modulus of 50 N / mm ^2. For the optical fiber cable D, the material of the jacket layer 2 has a Young's modulus of 120 N / mm ²
It is a new nylon resin (hereinafter referred to as "NY"). The bending stiffness of the optical fiber cables C and D is
^They are 320 N · mm ² and 350 N · mm ² , respectively.

As shown in FIG. 2, the optical fiber cable E comprises three optical fiber cores 4 and an FRP having a diameter of 0.25 mm.
4 of 5 are gathered, and the material of the jacket layer 2 (1.0 mm in diameter) is NY, and the material of the outermost layer 1 is 40% foamed HD.
PE is adopted, and the bending rigidity of the cable E is 400 N · mm ² . And the optical fiber cable F
As shown in Fig. 3, one optical fiber core wire 4 and its diameter
6 pieces of 0.25mm FRP5 are gathered together, and jacket layer 2
NY for the (1.0 mm diameter) material and 40 for the outermost layer 1 material
% Foamed HDPE is adopted, and the flexural rigidity is 420 N · mm ² .

The outer diameters of the optical fiber cables A to F were both 2.0 mm and the mass was 2.0 g / m.

Next, the above six types of optical fiber cables A
A pressure-feeding experiment was performed using ~ F.

The pressure feeding route is a straight route in which a 1500 m long pipe is laid in a straight line and a 500 m long pipe in diameter.
We adopted two routes, a curved route laid in a loop at 800 mm. The pumping conditions are an inlet pressure of 9 Kgf / cm ² and a pumping speed of 30 m / min.

The experimental results are shown in the lower column of Table 1. As shown in the table, in the straight route, only the optical fiber cable A could not be pumped, and the other optical fiber cables B to F could be pumped smoothly. In the curved route,
The optical fiber cables A to E could be pumped smoothly, but the optical fiber cable F could not be pumped.

From these results, the bending rigidity of the optical fiber cable for the pneumatic feeding method was determined to be 300 N of that of the optical fiber cable B.
・ It can be seen that if the pressure is set to mm ² or more, the optical fiber cable can be satisfactorily pumped without being pushed back to the inlet side even by the inlet pressure in the pipe. Further, it is understood that if the cable bending rigidity is 400 N · mm ² or less of the optical fiber cable E, the frictional force from the inner surface of the pipe with respect to the pressure-feeding force due to the air flow can be suppressed to be small and the pressure-feeding can be performed well even in the curved route.

[0024]

In summary, according to the present invention, the bending rigidity of the optical fiber cable for the pneumatic feeding method is 300 to 400 N.multidot.
By setting the thickness in the range of mm ² , it is possible to realize the optical fiber cable for the pneumatic feeding method having good pressure feeding characteristics.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an example of an optical fiber cable for a pneumatic feeding method.

FIG. 2 is a cross-sectional view showing another example of an optical fiber cable for a pneumatic feeding method.

FIG. 3 is a cross-sectional view showing still another example of the optical fiber cable for pneumatic feeding method.

FIG. 4 is a diagram for explaining a pneumatic feeding method.

[Explanation of reference numerals] 1 outermost layer 2 jacket layer 3 intervening cord 5 FRP 6 pipe 7 pressure feeding device 8 optical fiber cable for pneumatic feeding method

Claims (2)

[Claims] 1. An optical fiber cable laid in a pipe by a pneumatic feeding method, wherein the cable bending rigidity is 300 N · mm ² or more and 400 N · mm ² or less. Fiber optic cable. 2. The optical fiber cable for a pneumatic feeding method according to claim 1, wherein at least one optical fiber core wire is assembled, and the outer peripheral side thereof is covered.