Void forming device and void forming method

Abstract

A void forming device 1 for forming voids in a conduit for an optical cable includes: a hollow part 11 having an expandable bag-like sealing structure; a foam part 12 for generating gas inside the hollow part; and a control part 13 for controlling, from the outside of the hollow part, the generation of the gas.

Description

Void forming apparatus and void forming method

[0001] The present disclosure relates to a void forming apparatus and a void forming method.

[0002] When an optical cable is laid in a pipe line in a freezing section, the optical cable may fail due to the influence of freezing pressure accompanying volume expansion caused by freezing of retained water in the pipe line. Accordingly, there is a technique in which a PE (polyethylene) pipe is laid together with an optical cable, and the PE pipe absorbs the freezing pressure applied to the optical cable instead.

[0003] Takeaki Kato, 4 other authors, "Study on Freezing Failure Countermeasures to Realize Expansion of Application of Intermittent Non-slot Structure Cables", IEICE, 2017 Communications Society Conference, B-10-12, August 29, 2017

[0004] In order to prevent failure of an optical cable, the void fraction in the pipe line must be kept at or above a certain level. When the diameter of the pipe line is 75 mm, as many as six PE pipes with a diameter of 19 mm must be laid. Further, in the case of a pipe line having a bent shape such as a rising pipe line, the PE pipe must be bent. For this reason, a large burden has been placed on optical cable installers.

[0005] The present disclosure has been made in view of the above circumstances, and an object of the present disclosure is to provide a technique capable of improving the construction cost of an optical cable for preventing failure of the optical cable.

[0006] A void forming apparatus according to one aspect of the present disclosure is a void forming apparatus that forms a void in an optical cable pipe line, comprising: a hollow portion having an inflatable bag-shaped sealed structure; a foaming portion that generates gas inside the hollow portion; and a control unit that controls generation of the gas from outside the hollow portion.

[0007] A void forming method according to one aspect of the present disclosure is a void forming method for forming a void in an optical cable pipe line, wherein a hollow portion having an inflatable bag-shaped sealed structure and a foaming portion that generates gas inside the hollow portion are placed into the optical cable pipe line, and the gas is generated by a control unit that controls generation of the gas from outside the hollow portion.

[0008] According to this disclosure, the installation costs of optical cables related to preventing failures in optical cables can be reduced.

[0009] Figure 1 is a side view of the void-forming device. Figure 2 is a cross-sectional view of the void-forming device. Figure 3 is a cross-sectional view of the void-forming device. Figure 4 is a diagram showing the installation image of the void-forming device. Figure 5 is a diagram showing the expansion image of the void-forming device. Figure 6 is a diagram showing an example configuration of the void-forming device according to Example 1. Figure 7 is a diagram showing the control image of the void-forming device according to Example 1. Figure 8 is a diagram showing the expansion image of the void-forming device according to Example 1. Figure 9 is a diagram showing an example configuration of the void-forming device according to Example 2. Figure 10 is a diagram showing an example of the installation of the void-forming device. Figure 11 is a diagram showing an example of the installation of the void-forming device.

[0010] Embodiments of this disclosure will be described below with reference to the drawings. In the drawings, the same parts are denoted by the same reference numerals and their descriptions are omitted.

[0011] Figures 1 to 3 show examples of the configuration of a void-forming apparatus according to this embodiment. Figure 1 is a side view of the void-forming apparatus 1. Figure 2 is a cross-sectional view of the void-forming apparatus 1 shown in Figure 1 in the x-y plane. Figure 3 is a cross-sectional view of the void-forming apparatus 1 shown in Figure 1 in the y-z plane.

[0012] The void-forming device 1 is a device that forms voids or spaces within a conduit into which optical cables are inserted and laid. The void-forming device 1 comprises a hollow section 11, a foamed section 12, and a control section 13.

[0013] The hollow section 11 is composed of a flexible and elastic outer covering 11a, and has an expandable, bag-like sealed structure due to the flexibility and elasticity of the outer covering 11a. The hollow section 11 also has an elongated cylindrical shape so that it can be easily inserted into an elongated conduit. However, since it only needs to be able to be inserted into the conduit, the hollow section 11 does not need to have a predetermined shape and can be any shape, such as a rubber tube.

[0014] The foamed section 12 is located inside the hollow section 11 and is a part that generates gas. For example, the foamed section 12 consists of water 12a and a foaming material 12b that generates gas when it comes into contact with the water 12a, which are spaced apart from each other.

[0015] Water 12a is placed in a first inner bag 12c that is flexible, elastic, expandable, and meltable. Foam material 12b is placed in a second inner bag 12d that is flexible, elastic, and meltable, and is located inside the first inner bag 12c.

[0016] However, since it is sufficient for the water 12a and the foam material 12b to be in contact with each other, the first inner bag 12c is not necessarily required, and the water 12a only needs to be inside the hollow section 11. However, since the water 12a will shift position due to gravity, it is preferable to put the water 12a in the first inner bag 12c so that the water 12a and the foam material 12b can be in reliable contact with each other.

[0017] The control unit 13 has a configuration, function, and mechanism for controlling the generation of gas in the foamed section 12 from outside the hollow section 11. For example, the control unit 13 includes a heating wire 13a positioned close to the first inner bag 12c and the second inner bag 12d, two power supply wires 13b1 and 13b2 connected to the heating wire 13a, and a power supply 13c connected to the two power supply wires 13b1 and 13b2.

[0018] Next, we will explain the method for forming voids.

[0019] First, lay the optical cable and the gap-forming device 1 inside the desired conduit (Procedure 1).

[0020] Figure 4 shows the normal state when the void-forming device 1 and optical cable 2 are laid inside the conduit 100. The first inner bag 12c is omitted. In the normal state, the void-forming device 1 is contracted into the space inside the conduit 100, and the void-forming device 1 can be smoothly inserted into the conduit 100.

[0021] Next, turn on power 13c (step 2).

[0022] A small amount of water 12a and foaming material 12b are placed inside the void-forming device 1. The power supply 13c is turned on to allow current to flow, and a voltage is applied between the two power lines 13b1 and 13b2. As a result, the heating element 13a is heated, the second inner bag 12d melts, and the foaming material 12b falls out. Subsequently, the water 12a and foaming material 12b mix with each other, generating gas, and the hollow section 11 expands.

[0023] As a result, as shown in Figure 5, the void ratio of the void-forming device 1 increases, ensuring a certain level of void ratio within the conduit 100. Since it is not necessary to lay multiple PE cables, working time and workload can be reduced, and construction costs can be lowered. In other words, it is possible to create the necessary voids within the conduit to prevent cable freezing failures with less burdensome construction work than before.

[0024] (Example 1) Figure 6 shows an example of the configuration of the void forming apparatus according to Example 1.

[0025] The void-forming apparatus 1 according to Embodiment 1 divides one hollow section 11 into three hollow sections 11' to 11''' with two sealing sections 14, and each of the three hollow sections 11' to 11''' is provided with a separate foamed section 12.

[0026] In other words, the void-forming apparatus 1 according to Embodiment 1 has a configuration in which multiple hollow sections 11, including the foamed section 12 shown in Figures 1 to 3, are created, and the multiple created hollow sections 11 are connected in series with a sealing material which is a sealing section 14. Note that the number of hollow sections may be four or more.

[0027] Each of the three hollow sections 11' to 11'' has a separate heating element 13a, and two common power lines 13b1 and 13b2 are connected to all the heating elements 13a, and a power supply 13c is connected to these two power lines 13b1 and 13b2. Each foamed section 12 is filled with water 12a and foaming material 12b (not shown in Figure 6).

[0028] When the power supply 13c is turned on, as shown in Figure 7, current flows through the two power lines 13b1 and 13b2, causing the heating element 13a to heat up in all the hollow sections 11' to 11'', the second inner bag 12d to begin to melt, the foam material 12b to fall out, and the foam material 12b and water 12a mix together and undergo a chemical reaction to produce gas. As a result, as shown in Figure 8, the three hollow sections 11' to 11''' each expand, creating voids in each of the hollow sections 11' to 11'''.

[0029] Furthermore, it is desirable that the generated gas is a non-flammable gas. For example, the foaming agent 12b is baking soda and citric acid, which react with water 12a to produce carbon dioxide. Also, it is desirable that the voltage required to dissolve the second inner bag 12d be a voltage commonly used in generators, such as AC 100V or DC 12V. In addition, it is desirable that the outer covering 11a of the hollow section 11 be made of a soft and elastic material such as polyurethane or latex.

[0030] Based on the above, according to Example 1, since it has three hollow sections 11' to 11''' connected in series, it can be used even in long pipelines. In other words, since there is a limit to the amount (volume) of gas generated, a single hollow section can only be used at one location in a long pipeline, but multiple hollow sections connected in series can create voids at multiple locations in a long pipeline.

[0031] (Example 2) Figure 9 shows an example of the configuration of the void forming apparatus according to Example 2.

[0032] In the void-forming apparatus 1 according to Embodiment 2, the two power lines 13b1 and 13b2 extend to the other end (left end) in the longitudinal direction of the void-forming apparatus 1, as shown in Figure 6 of Embodiment 1. Furthermore, at this other end, a power supply 13c', separate from the power supply 13c shown in Figure 6, is connected to the two power lines 13b1 and 13b2.

[0033] In other words, the void formation device 1 according to Embodiment 2 allows the formation of voids within the pipeline to be controlled from both ends of the void formation device 1. That is, it is a backup configuration in which one power supply 13c is the main power supply and the other power supply 13c' is the backup power supply.

[0034] For example, in the configuration shown in Figure 9, when the power supply line 13b1 between the hollow section 11' and the hollow section 11'' is broken, the hollow section 11' will not expand even if voltage is applied from the power supply 13c on the right side. On the other hand, in Embodiment 2, voltage can also be applied from the power supply 13c' on the left side, and by applying voltage from this power supply 13c', the hollow section 11' can also be expanded.

[0035] Based on the above, according to Embodiment 2, since a power supply 13c is provided at one end of the void forming device 1 and a power supply 13c' is also provided at the other end of the void forming device 1, the void forming device 1 can be reliably expanded. Similarly, the same effect can be obtained by providing multiple power supplies to a void forming device 1 with a single hollow section.

[0036] (Example 3) Figures 10 and 11 show examples of the installation of the void-forming device. Figure 10 shows an example of the installation of the void-forming device 1 on a straight pipeline 100. Figure 11 shows an example of the installation of the void-forming device 1 on a curved pipeline 100, such as a pull-up pipeline.

[0037] As described in Examples 1 and 2, the void-forming device 1 is flexible and can be inserted into and laid in pipes of various shapes and diameters. For example, it can be inserted into and laid in curved pipes with angles of 45, 90, and 120 degrees, and in pipes with diameters of 25 mm, 50 mm, and 75 mm.

[0038] Furthermore, in order to prevent optical cable failure due to the effects of freezing pressure, a void ratio of approximately 40% is required within the conduit. Therefore, it is desirable that the void ratio of the voids formed within the conduit by the void-forming device 1 (= β ÷ (γ - α), where β is the volume of the void-forming device, γ is the volume inside the conduit, and α is the volume of the optical cable) is also approximately 40%.

[0039] 1. Void forming device 11. Hollow section 11a. Outer cover 12. Foamed section 12a. Water 12b. Foaming material 12c. First inner bag 12d. Second inner bag 13. Control unit 13a. Heating wire 13b1. Power supply wire 13b2. Power supply wire 13c. Power supply 14. Sealing section 2. Optical cable 100. Conduit

Claims

1. A void-forming device for forming a void in a conduit for optical cables, comprising: a hollow section having an expandable bag-like sealed structure; a foaming section that generates gas inside the hollow section; and a control unit that controls the generation of the gas from outside the hollow section.

2. The void-forming apparatus according to claim 1, wherein the hollow portion is a plurality of hollow portions connected in series by a sealing material, and the foamed portion is contained inside each of the plurality of hollow portions.

3. The void-forming apparatus according to claim 1 or 2, wherein the foamed portion comprises water arranged spaced apart from each other and a foaming material that generates gas when it comes into contact with the water.

4. The void forming apparatus according to claim 3, comprising: a control unit, a heating wire positioned in close proximity to a meltable bag containing the foam material; a power supply wire connected to the heating wire; and a power supply wire connected to the power supply wire.

5. The air gap forming apparatus according to claim 4, wherein the power supply is a plurality of power supplies provided at both ends in the longitudinal direction of the hollow portion.

6. The void-forming apparatus according to claim 3, wherein the foaming material is baking soda and citric acid.

7. The void-forming apparatus according to claim 1, wherein the hollow portion expands until its volume accounts for 40% of the volume of the conduit excluding the volume of the optical cable.

8. A method for forming a void in a conduit for optical cables, comprising: placing a hollow section having an expandable bag-like sealed structure and a foaming section that generates gas inside the hollow section into the conduit for the optical cable; and generating the gas from outside the hollow section using a control unit that controls the generation of the gas.

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