How to collect the sheath

Abstract

To provide a cable removal method capable of reliably pulling out and removing remaining cables.SOLUTION: A cable removal method is a cable removal method for removing cable 5 laid in pipeline 2. The cable removal method includes: a preparation step of preparing multiple cylindrical sheath tubes 30 with openings at both ends; a head sheath pipe entry step (B) of inserting the sheath tube 30 between the pipeline 2 and the cable 5; a subsequent sheath tube entry step (C) of inserting the subsequent sheath tube 30 so that the opening at the side opposite to the advancing direction of the sheath tube 30 that has been advanced immediately before and the opening at the advancing direction side are in contact with each other; and an extraction step (D) of extracting the cable 5 from the pipeline 2 by applying a tensile force to the cable 5.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a cable removal method for removing a cable that has been left behind in an underground conduit and cannot be removed, and a sheath tube recovery method that is carried out to recover the sheath tube used in removing the cable after the cable removal method has been carried out. [Background technology]

[0002] Power cables used for electricity transmission are sometimes buried underground under public roads without the use of utility poles. There are cases where such cables need to be removed from the conduits through which they run.

[0003] The process for removing such cables includes a method of cutting the cable at a manhole or the like, applying a tensile force to one end of the cable with a winch prepared above the manhole to pull it out in one direction, and then winding it up on the drum of the winch to remove the cable, or a method of removing the cable by cutting the cable pulled out by a tensile force at appropriate intervals.

[0004] However, even after carrying out such a removal process, there are some cables that cannot be removed and are left behind in the conduit. The reasons why the cable cannot be removed include that the exterior of the cable has become stuck to the conduit, or that soil or sand has entered the conduit and accumulated around the cable, or that the accumulated soil or sand has hardened over time, causing the cable to stick to the conduit.

[0005] For the remaining cables that cannot be removed by the above-mentioned pulling force, it is possible to remove them by open-cut construction. However, performing open-cut construction to remove the cables requires a lot of cost and a long work period.

[0006] Therefore, as a method for removing remaining cables without performing excavation work, for example, Patent Document 1 (JP 2012-80693 A) proposes a cable pulling and removal method that includes the steps of passing a wire through the gap between the conduit and the cable, connecting the passed wire to a cutting tool, peeling off the adhesion between the conduit and the cable using the cutting tool, and pulling out and removing the cable. [Patent Document 1] JP 2012-80693 A Summary of the Invention [Problem to be solved by the invention]

[0007] In the conventional technology described in Patent Document 1, it is necessary to carry out a process of passing a wire through the gap between the conduit and the cable. However, in the case of a remaining cable where the cable exterior is adhered to the conduit, or where soil or sand has accumulated between the cable and the conduit, or where the accumulated soil or sand has solidified and caused the cable to adhere to the conduit, it is difficult to carry out the process of passing a wire through in the first place. Therefore, even if the conventional technology is used, there is a problem that it is not necessarily possible to actually pull out and remove the remaining cable. [Means for solving the problem]

[0008] In order to solve such problems, the sheath tube recovery method according to the present invention includes the following steps: A cable removal method for removing a cable laid in a conduit, comprising: a preparation step of preparing a plurality of cylindrical sheath tubes having openings at both ends; a leading sheath tube insertion step of inserting a sheath tube between the conduit and the cable; a succeeding sheath tube insertion step of inserting a subsequent sheath tube such that the opening on the side opposite to the insertion direction of the sheath tube inserted immediately before abuts against the opening on the insertion direction side; and a withdrawal step of applying a tensile force to the cable to pull the cable out of the conduit. This sheath tube retrieval method is carried out after the cable removal method has been carried out, and is characterized by comprising a wiring step of passing a wire from one end of the pipeline to the other end thereof, a tying step of tying the wire to a retrieval member having an outer diameter larger than that of the sheath tube at the other end of the pipeline, and a removal step of applying a tensile force to the wire at the one end of the pipeline to remove the sheath tube from the one end of the pipeline. Effect of the Invention

[0016] The cable removal method of the present invention involves inserting a sheath tube between the fixed conduit and cable, peeling the cable from the conduit, and pulling out the cable. This cable removal method of the present invention eliminates the need for excavation work, which requires great costs and a long work period, and does not require the difficult process of threading wire as in the conventional technology, making it possible to reliably pull out and remove the remaining cable.

[0017] Furthermore, according to the method for recovering the sheath tube of the present invention, it is possible to easily recover the sheath tube used to remove the remaining cable. [Brief description of the drawings]

[0018] [Figure 1] FIG. 2 is a diagram illustrating a sheath tube press-fitting device 50 used in the cable removal method according to the embodiment of the present invention. [Diagram 2] FIG. 2 is a diagram illustrating a sheath tube press-fitting device 50 used in the cable removal method according to the embodiment of the present invention. [Diagram 3] FIG. 2 is a diagram illustrating a sheath tube 30 used in the cable removal method according to the embodiment of the present invention. [Figure 4] FIG. 2 is a diagram illustrating a sheath tube 30 used in the cable removal method according to the embodiment of the present invention. [Diagram 5] 1A to 1C are diagrams for explaining each step in a cable removal method according to an embodiment of the present invention. [Figure 6] 1A to 1C are diagrams illustrating each step in a sheath tube recovery method according to an embodiment of the present invention. [Figure 7] 1 is a diagram illustrating a recovery member 90 used in a sheath recovery method according to an embodiment of the present invention. FIG. [Figure 8] 13A and 13B are diagrams showing another embodiment of the recovery member 90. [Figure 9] FIG. 2 is a diagram showing another embodiment of the sheath 30. [Figure 10] FIG. 2 is a diagram showing another embodiment of the sheath 30. [Figure 11] FIG. 2 is a diagram showing another embodiment of the sheath 30. [Figure 12] FIG. 2 is a diagram showing another embodiment of the sheath 30. [Figure 13] FIG. 2 is a diagram showing another embodiment of the sheath 30. [Figure 14] FIG. 11 is a diagram illustrating a leading sheath tube 30 used in a cable removal method according to another embodiment of the present invention. [Figure 15] 13 is a diagram showing another aspect of the leading sheath tube 30 used in the cable removal method according to another embodiment of the present invention. FIG. [Figure 16] 5A to 5C are diagrams for explaining each step in a cable removal method according to another embodiment of the present invention. [Figure 17] 11A to 11C are diagrams illustrating a sheath tube recovery method according to another embodiment of the present invention. [Figure 18] 10A to 10C are diagrams illustrating another aspect of the sheath tube press-fitting device 50 used in the cable removal method according to an embodiment of the present invention. [Figure 19] 10A to 10C are diagrams illustrating another aspect of the sheath tube press-fitting device 50 used in the cable removal method according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Figures 1 and 2 are diagrams illustrating a sheath pipe press-in device 50 used in a cable removal method according to an embodiment of the present invention. The cable removal method according to the present invention relates to a method for removing cables left underground that could not be removed by conventional methods. Furthermore, the cable removal method according to the present invention can be applied to any cable that is placed inside an underground conduit, and it does not matter whether the cable is for supplying power to a train or for supplying power to a normal consumer.

[0020] The cable removal method according to the present invention is characterized by using a plurality of cylindrical sheath tubes 30 having openings at both ends. The sheath tubes 30 are made of a material having rigidity such as steel. In Figs. 1 and 2, the cable 5 indicates a cable left in the conduit 2. In the cable removal method according to the present invention, first, a step of inserting the first sheath tube 30 between the conduit 2 and the cable 5 is performed, and then the following sheath tubes 30 are inserted in sequence so that the opening on the opposite side to the insertion direction of the sheath tube 30 inserted immediately before abuts against the opening on the insertion direction side of the sheath tube 30, and the sheath tubes 30 tear off the adhesion between the conduit 2 and the cable 5. Here, in Figs. 1 and 2, the right direction is the insertion direction, and the left direction is the retreat direction. In Figs. 1 and 2, the sheath tubes 30 are inserted in sequence to the right.

[0021] The manhole 3 is provided with an entrance 4 for workers, and a sheath pipe press-fitting device 50 is carried in through the entrance 4. The sheath pipe press-fitting device 50 is a device that presses the sheath pipes 30 into the pipeline 2 in sequence.

[0022] The sheath tube press-fitting device 50 is composed of a main body 51 and a drive unit 54 provided above the main body 51. A control circuit (not shown) for the sheath tube press-fitting device 50 is provided within the main body 51, and the drive unit 54 is provided with a cylinder (not shown) that drives a rod unit 55. The rod unit 55 is driven by the cylinder (not shown) in both the advancement direction and the retreat direction. A pressing unit 56 is provided on one end of the rod unit 55, which directly contacts the sheath tube 30 to press the sheath tube 30 into the pipeline 2.

[0023] The height of the sheath pipe press-fitting device 50 is adjusted by the jack 61. This allows the pressing part 56 to be adjusted to an appropriate position relative to the height of the pipeline 2 from the bottom of the manhole 3.

[0024] In addition, a front arm 52 is provided on the approach direction side of the main body 51, and a rear arm 53 is provided on the retreat direction side. A jack 62 is provided between the front arm 52 and the wall surface of the manhole 3, and a jack 63 is provided between the rear arm 53 and the wall surface of the manhole 3. By adjusting these jacks 62 and 63, the position of the sheath tube press-in device 50 in the forward and backward directions can be adjusted. In addition, since the sheath tube press-in device 50 is attached so as to be fixed to the wall surface of the manhole 3 via the front arm 52, the rear arm 53, and the jack, it is possible to prevent the sheath tube press-in device 50 from moving due to the reaction force generated when the rod portion 55 is driven to press the sheath tube 30 into the pipeline 2.

[0025] The sheath tube press-fitting device 50 is adapted to operate based on control commands from an operation switch 58 via a signal cable 57. The operation switch 58 is adapted to issue at least a control command to operate the rod portion 55 in the advancement direction, a control command to operate the rod portion 55 in the retreat direction, and a control command to make an emergency stop of the rod portion 55. In addition to these control commands, the control command from the operation switch 58 can also be set to operate the rod portion 55 with a smaller stroke (to make the rod portion 55 move finely). By providing such a control command to make a fine movement, the operation when setting the following sheath tube 30 becomes easier.

[0026] FIG. 1 shows a state where an operator sets the third sheath pipe 30 counting from the first sheath pipe 30 before pushing it into the pipeline 2. FIG. 2 shows a state where the rod portion 55 is operated in the direction of entry based on a control command from the operation switch 58, and the sheath pipe 30 is pushed into the pipeline 2. When the sheath pipe 30 is pushed into the pipeline 2 by the sheath pipe press-in device 50, it is preferable for the operator to evacuate from the manhole 3 to the ground in order to prevent accidents. For this reason, it is preferable that the length of the signal cable 57 is at least the length from the sheath pipe press-in device 50 main body installed in the manhole 3 to the hand of the operator who has evacuated to the ground.

[0027] 3 and 4 are diagrams for explaining a sheath tube 30 used in a cable removal method according to an embodiment of the present invention. Fig. 3 is suitable for use as a leading sheath tube 30, and Fig. 4 is used as a trailing sheath tube 30 that is not the leading one. In both figures, (A) is a perspective view, and (B) is a schematic cross-sectional view.

[0028] The dimensions of the sheath tube 30 are set so that the outer diameter is shorter than the inner diameter of the conduit 2 and the inner diameter is longer than the outer diameter of the cable 5. This allows the sheath tube 30 to be inserted between the conduit 2 and the cable 5.

[0029] The longer the length of the sheath tube 30 (the length from the left end to the right end in each figure (B)), the fewer the number of sheath tubes 30 required to peel off the cable 5 from the conduit 2. However, since the sheath tube 30 is pressed into the manhole 3 by the sheath tube pressing device 50, the length of the sheath tube 30 cannot be made very long. Furthermore, since not only straight conduits 2 but also those having curvatures are included, the length of the sheath tube 30 must also be adapted to conduits 2 having such curvatures. It is preferable that the length of the sheath tube 30 be appropriately set according to the curvature (bending radius) of the conduit 2.

[0030] 3 shows a suitable sheath tube 30 for the leading end, characterized in that a taper 33 is provided at the opening 31 on the entry direction side. This taper 33 is such that the inner diameter of the sheath tube 30 increases the closer it is to the opening 31. The leading sheath tube 30 is provided with a blade-shaped taper 33 to facilitate press-fitting the sheath tube 30 and prevent damage to the cable 5. When the cable 5 is an OF cable filled with insulating oil, oil leakage occurs when the cable is damaged, so it is particularly preferable to use a sheath tube 30 provided with such a taper 33 as the leading one.

[0031] On the other hand, the sheath tube 30 that is not the leading one and is used following the leading one may have an outer diameter and an inner diameter that do not change over its length (the length from the left end to the right end in FIG. 4(B)), as shown in FIG. 4. Such a sheath tube 30 can be fabricated more inexpensively than one with a taper 33.

[0032] Next, a process for removing the cable 5 using the above-described sheath tube 30 and sheath tube press-fitting device 50 will be described. Fig. 5 is a diagram for explaining each step in the cable removal method according to an embodiment of the present invention. In Fig. 5, the sheath tube press-fitting device 50 is omitted from the illustration.

[0033] Figure 5(A) shows a cable 5 left in a conduit 2 between two manholes 3. In the figure, X indicates the location where the exterior of the cable 5 is fixed to the conduit 2, and Y indicates the location where the accumulated soil and sand in the conduit 2 has solidified, causing the cable 5 to adhere to the conduit 2.

[0034] 5(B), the leading sheath tube 30 is inserted between the conduit 2 and the cable 5. The sheath tube 30 used at this time is preferably the one shown in FIG.

[0035] 5(C), the succeeding sheath tubes 30 are sequentially advanced. In this step, the succeeding sheath tubes 30 are advanced so that the opening on the opposite side to the direction of advancement of the sheath tube 30 previously advanced comes into contact with the opening on the direction of advancement of the sheath tube 30. In this manner, the succeeding sheath tubes 30 are advanced sequentially into the conduit 2, and when the sheath tubes 30 are continuous over the length of the conduit 2, the fixed state between the conduit 2 and the cable 5, as indicated by X and Y, is completely severed.

[0036] In the next process shown in Figure 5 (D), the cable 5 is no longer attached to the pipeline 2, so a tensile force is applied to the cable 5 by the winch 80 to pull the cable 5 out of the pipeline 2, and the cable 5 is then wound onto the drum 83.

[0037] The cable removal method of the present invention as described above involves inserting a sheath tube 30 between the fixed conduit 2 and cable 5, thereby peeling the cable 5 from the conduit 2 and pulling out the cable 5. This cable removal method of the present invention does not require excavation work, which requires great costs and a long work period, and does not require the difficult process of threading wire as in the conventional technology, making it possible to reliably pull out and remove the remaining cable.

[0038] Now, when the above-mentioned cable removal method is carried out, the sheath tube 30 will remain in the pipeline 2. If the sheath tube 30 is left in the pipeline 2, it will cause problems such as reusing the pipeline 2. Furthermore, the sheath tube 30 cannot be reused, which will increase costs. Therefore, next, a method for recovering the sheath tube 30 left in the pipeline 2 will be described.

[0039] 6A and 6B are diagrams for explaining each step in the sheath tube recovery method according to the embodiment of the present invention. In the steps shown in Fig. 6A, a winch 105 is installed in the manhole 3 on the left side, and the wire 100 is pulled out from its drum 108, passed through the sheath tube 30 that is continuous in the pipeline 2, and then pulled out from the manhole 3 on the right side. It has been sent out to manhole 3.

[0040] In the next step shown in FIG. 6(B), the wire 100 is tied to the recovery member 90, and the right side A winch 115 is also installed in the manhole 3, and the wire 102 wound around the drum 118 is also tied to the recovery member 90. Next, the recovery member 90 will be described.

[0041] 7 is a diagram illustrating a recovery member 90 used in a sheath tube recovery method according to an embodiment of the present invention. The recovery member 90 has a shape roughly like a lid of a cylindrical closed container. The inner diameter of the recovery member 90 is larger than the outer diameter of the sheath tube 30, and the outer diameter of the recovery member 90 is smaller than the inner diameter of the pipeline 2. The recovery member 90 is made of a material having rigidity, such as steel.

[0042] The recovery member 90 has a cylindrical portion 91, an opening 92 at one end side of the cylindrical portion 91, and a lid portion 93 at the other end side of the cylindrical portion 91. An annular portion 95 is provided inside the cylindrical portion 91 in the lid portion 93, and an annular portion 96 is provided outside the cylindrical portion 91 in the lid portion 93. A wire 100 is tied to the annular portion 95, and a wire 102 is tied to the annular portion 96.

[0043] In the process of Fig. 6(C), the wire 100 is wound up by the winch 105, while the wire 102 is sent out by the winch 115. As a result, the recovery member 90 as described above sequentially pushes out the sheath pipe 30 from inside the pipeline 2 to the left side of the manhole 3. Although the wire 102 can be omitted, it is preferable to provide it as a backup in case of trouble such as the wire 100 being cut.

[0044] According to the sheath tube recovery method of the present invention as described above, it is possible to recover the sheath tube 30 used to remove the remaining cable.

[0045] The recovery member 90 is not limited to the shape described above, and other shapes may be used. Fig. 8 is a diagram showing another embodiment of the recovery member 90. The previous recovery member 90 was in such a form that the outer periphery of the leading sheath tube 30 was fitted into the inner periphery of the cylindrical portion 91, thereby recovering the sheath tube 30. On the other hand, the recovery member 90 shown in Fig. 8 has a cylindrical portion 97 provided on the lid portion 93, and the inner periphery of the leading sheath tube 30 is fitted into the outer periphery of the cylindrical portion 97, and the lid portion 93 pushes the sheath tube 30 in the backward direction, thereby recovering the sheath tube 30.

[0046] Next, another embodiment of the present invention will be described. In the other embodiment, the sheath tube 30 used is different from that of the previous embodiment, and the rest is similar, so the description will be omitted. Figure 9 is a diagram showing the sheath tube 30 used in the other embodiment. This sheath tube 30 is provided with a hollow portion 40, and the weight of the sheath tube 30 is reduced. In the sheath tube 30 shown in Figure 9, the rectangular hollow portion 40 is provided in two places in the sheath tube 30, but the shape and number of the hollow portion 40 are not limited to this, and any hollow portion 40 may be provided as long as the rigidity of the sheath tube 30 is maintained. According to such an embodiment, the sheath tube 30 is reduced in weight, and the handleability is improved. In addition, the hollow portion 40 is provided in the sheath tube 30, which makes it easier to discharge and process the solidified material including soil and sand peeled off from between the pipeline 2 and the cable 5. The solidified material peeled off from between the pipeline 2 and the cable 5 may hinder the entry of the following sheath tube 30. When the stuck material enters the sheath tube 30 from the hollowed-out portion 40, it is expected that the resistance to the entry of the sheath tube 30 will be reduced. This will facilitate the entry of the succeeding sheath tube 30. In addition, by recovering the sheath tube 30 after removing the cable, the stuck material in the sheath tube 30 can also be recovered at the same time.

[0047] Fig. 10 shows a sheath tube 30 following the leading one, which is provided with a guide piece 41 made of steel or the like. Fig. 10(A) is a perspective view of the sheath tube 30, and Fig. 10(B) is a diagram showing a state where the sheath tube 30 is used as the sheath tube 30 following the leading sheath tube 30. By using a sheath tube 30 provided with such a guide piece 41 as the following sheath tube 30, it becomes possible to push the sheath tubes 30 continuously into the pipeline 2 more reliably. Also, by providing such a guide piece 41 on the sheath tube 30, it becomes possible to prevent the front and rear sheath tubes from being misaligned with each other.

[0048] Also, Fig. 11 shows a sheath tube 30 other than the leading one, which is provided with an expanded diameter portion 42 having a diameter larger than that of the main cylindrical portion at one end of the opening. Fig. 11(A) is a perspective view of the sheath tube 30, and Fig. 11(B) is a diagram showing a state where the sheath tube 30 is used as the sheath tube 30 following the leading sheath tube 30. By using the sheath tube 30 provided with such an expanded diameter portion 42 as the following sheath tube 30, it becomes possible to push the sheath tubes 30 continuously into the pipeline 2 more reliably. Also, by providing such an expanded diameter portion 42 on the sheath tube 30, it becomes possible to prevent the front and rear sheath tubes from being misaligned with each other.

[0049] Also, FIG. 12 shows a sheath tube 30 following the leading one, in which a reduced diameter portion 43 having a diameter smaller than that of the main cylindrical portion is provided at one end of the opening. FIG. 12(A) is a perspective view of the sheath tube 30, and FIG. 12(B) is a diagram showing a state in which the sheath tube 30 is used as a sheath tube 30 following the leading sheath tube 30. When the sheath tube 30 provided with the enlarged diameter portion 42 shown in FIG. 11 is used, the enlarged diameter portion 42 is used on the side of the entry direction of the sheath tube 30. On the other hand, when the sheath tube 30 provided with the reduced diameter portion 43 shown in FIG. 12 is used, the reduced diameter portion 43 is used on the side opposite to the entry direction of the sheath tube 30. This is because if the reduced diameter portion 43 is used on the entry direction side of the sheath tube 30, the cable 5 may be damaged. By using a sheath tube 30 provided with such a reduced diameter portion 43 as the succeeding sheath tube 30, it becomes possible to more reliably push the sheath tubes 30 continuously into the pipeline 2. Furthermore, by providing the sheath tube 30 with such a reduced diameter portion 43, it becomes possible to prevent the front and rear sheath tubes from being misaligned with each other.

[0050] Next, another embodiment of the sheath tube 30 will be described with reference to FIG. 13. In the figure, the sheath tube 30 on the far right side is the leading one, and the other sheath tubes 30 are the trailing ones. In this embodiment, the leading sheath tube 30 has a taper 33 at both the entry end and the retreat end. On the other hand, the trailing sheath tube 30 has an outer circumferential taper 38 at the entry end and a taper 33 at the retreat end. By using these sheath tubes 30, the outer circumferential taper 38 can be fitted into the taper 33 at the location where the sheath tubes 30 abut against each other as shown in the figure, and the sheath tubes 30 can be advanced into the pipeline 2, thereby preventing the sheath tubes from being misaligned with each other.

[0051] Next, another embodiment of the present invention will be described. Figure 14 is a diagram for explaining the leading sheath tube 30 used in the cable removal method according to another embodiment of the present invention. The leading sheath tube 30 used in this embodiment is provided with four through holes 34, 34', 35, 35'. More specifically, the through holes 34, 35 are provided on one side of the sheath tube 30, and the through holes 34', 35' are provided on the other side opposite to the one side. A wire 36 is attached to the through holes 34, 35 on the one side. Also, a wire 36' is attached to the through holes 34', 35' on the other side. These two wires 36, 36' are sent out from the drums 48, 48' of the winches 45, 45' installed in the manhole 3, respectively.

[0052] The number of wires attached to the leading sheath tube 30 is not limited to two, and may be any number. In this embodiment, the wires are attached using the through holes, but the method of attaching the wires is not limited to this. In short, when the sheath tube 30 is advanced following the leading sheath tube 30, the wire is attached to the leading sheath tube 30 so that the wire is not caught between the leading sheath tube 30 and the trailing sheath tube 30.

[0053] In addition, in Fig. 14, through holes 34, 35 are provided on one side of the sheath tube 30, and through holes 34', 35' are provided on the other side opposite the one side, and two wires 36, 36' are attached using these through holes, but the method of attaching the wires is not limited to this. For example, as shown in Fig. 15, a loop portion 37 may be provided on one side of the sheath tube 30, and a loop portion 37' may be provided on the other side opposite the one side, and two wires 36, 36' may be attached using these loop portions.

[0054] A cable removal method according to another embodiment using such a leading sheath tube 30 will now be described. Fig. 16 is a diagram for explaining each step in the cable removal method according to another embodiment of the present invention. In the figure, X indicates the location where the sheath of the cable 5 is fixed to the pipeline 2. Also, in Fig. 16, the sheath tube press-fitting device 50 is omitted from the illustration.

[0055] A cable removal method according to another embodiment is characterized in that a tensile force is applied to the cable 5 before the sheath pipes 30 are sequentially pressed in. For this purpose, in the step of Fig. 16(A), an intermediate wire 85 is attached to one end of the cable 5 in the conduit 2, and a tensile force is applied to the cable 5 by the winch 80 via this intermediate wire 85.

[0056] 16(B), the leading sheath tube 30 described above is pressed in. At this time, the winches 45, 45' are in a neutral state, and the wires 36, 36' are fed out as the sheath tube 30 advances.

[0057] In the next step shown in Fig. 16(C), the second sheath tube 30 is pressed in. The second and subsequent sheath tubes 30 may be the same as the sheath tubes 30 described above. Now, if the fixed portion between the cable 5 and the pipeline 2 is only at X, the cable 5 is wound around the drum 83 of the winch 80 by the tensile force applied via the intermediate wire 85 at the stage of Fig. 16(C), as shown in Fig. 16(D). In this manner, in this embodiment, since the tensile force is applied to the cable 5 in advance, there is a possibility that the cable 5 may be pulled out by pressing in a small number of sheath tubes 30.

[0058] Next, a sheath tube recovery method according to another embodiment will be described. FIG. 17 is a diagram for explaining a sheath tube recovery method according to another embodiment of the present invention. As described above, wires 36, 36' are attached to the leading sheath tube 30. In the sheath tube recovery method according to the other embodiment, the winches 45, 45' are driven to wind up these wires 36, 36' onto the drums 48, 48'. As a result, it becomes possible to sequentially remove the sheath tube 30 from the left side to the outside of the pipeline 2. According to the sheath tube recovery method according to the other embodiment as described above, it becomes possible to recover the sheath tube 30 more easily.

[0059] As described above, the cable removal method of the present invention involves inserting a sheath tube between the fixed conduit and cable, peeling the cable from the conduit, and pulling out the cable. This cable removal method of the present invention eliminates the need for excavation work, which requires great costs and a long work period, and does not require the difficult process of threading wire as in the conventional technology, making it possible to reliably pull out and remove the remaining cable.

[0060] Furthermore, according to the method for recovering the sheath tube of the present invention, it is possible to easily recover the sheath tube used to remove the remaining cable.

[0061] Next, another embodiment of the sheath tube press-fitting device 50 used in the cable removal method according to the embodiment of the present invention will be described. Fig. 18 shows the sheath tube press-fitting device 50 according to the other embodiment. Note that in Fig. 18, components such as the signal cable 57 and the operation switch 58 are omitted.

[0062] In the sheath tube press-fitting device 50 shown in Fig. 1, when the pressing portion 56 of the rod portion 55 presses the sheath tube 30 into the pipeline 2, the sheath tube press-fitting device 50 receives a reaction force in a downward left direction, which may cause the device to lose stability. Therefore, in the sheath tube press-fitting device 50 shown in Fig. 18, the body portion 51 of the sheath tube press-fitting device 50 is installed so as to abut against the wall surface of the manhole 3. The wall surface that the body portion 51 abuts against is a wall surface that exists in the retreating direction, which is the opposite direction to the direction in which the rod portion 55 advances.

[0063] In the sheath tube press-in device 50 shown in Fig. 18, the rear arm 53 and the jack 63 supporting it are omitted. As a result, the reaction force generated when the sheath tube press-in device 50 presses the sheath tube 30 into the pipeline 2 can be received by the wall surface of the manhole 3 via the main body 51, stabilizing the sheath tube press-in device 50. When the sheath tube press-in device 50 is installed as shown in Fig. 18, a situation may arise in which the sheath tube press-in device 50 moves away from the opening of the pipeline 2 through which the sheath tube 30 is being pushed in, and the sheath tube 30 cannot be pushed into the pipeline 2 by the stroke of the rod portion 55 alone.

[0064] Therefore, it is preferable to use an intermediate guide device 70 to supplement the action of the pressing part 56 of the rod part 55 in pushing the sheath pipe 30 into the pipeline 2. This intermediate guide device 70 is a device that acts to extend the stroke of the rod part 55. A main body part 71 of the intermediate guide device 70 is fixed to the ground or wall surface of the manhole 3 by a fixing member (not shown) and is immovable.

[0065] On the other hand, the main body 71 holds a relay rod 75 which is displaceable in the left-right direction relative to the main body 71. The relay rod 75 is biased in the backward direction by a biasing member (not shown). A pressing portion 76 is provided at the end of the relay rod 75 on the insertion direction side.

[0066] With the above-mentioned configuration, when the pressing part 56 of the sheath tube press-fitting device 50 presses the end part of the relay rod part 75 on the backward direction side to the right on the page, the relay rod part 75 is displaced to the right, and the pressing part 76 comes into direct contact with the sheath tube 30, enabling the sheath tube 30 to be pressed into the pipeline 2. Furthermore, when the pressing part 76 completes the pressing of the sheath tube 30 and the rod part 55 is displaced to the left (backward direction), the relay rod part 75 is also displaced to the left (backward direction) due to the previous biasing force.

[0067] By using a group of devices for pushing the sheath tube 30 into the pipeline 2, which consists of a sheath tube pressing device 50 omitting the rear arm portion 53 and a relay guide device 70 as shown in Figure 18, the cable removal method of the present invention can be applied even in, for example, overflowing manholes 3 or handholes.

[0068] Figure 19 is also a diagram showing another embodiment of the sheath tube press-fitting device 50. The basic configuration of the sheath tube press-fitting device 50 is similar to that shown in Figure 1, but the one shown in Figure 19 is characterized in that it is provided with a magazine member 120 that sequentially sets the sheath tubes 30 to the pushing-in position.

[0069] This magazine member 120 is disposed between the pipeline 2 and the sheath tube press-fitting device 50. A loading port 125 of the magazine member 120 is an opening for supplying the sheath tubes 30, and it is preferable that the loading port 125 is laid out so as to be disposed at a position above the worker entrance 4 on the ground. It is assumed that the worker will sequentially supply the sheath tubes 30 from this loading port 125.

[0070] The sheath tube 30 supplied from the loading port 125 is loaded in the magazine member 120 as shown in Fig. 19. An insertion opening 126 is provided on the side of the sheath tube press-fitting device 50 below the magazine member 120, and an extrusion opening 127 is provided on the side of the pipeline 2. The pressing part 56 of the sheath tube press-fitting device 50 enters from the insertion opening 126 and presses the sheath tube 30 to the right. Meanwhile, with the movement of the pressing part 56 in the entering direction, the sheath tube 30 is pressed into the pipeline 2 from the extrusion opening 127. When the pressing part 56 of the sheath tube press-fitting device 50 retreats from the insertion opening 126, the new sheath tube 30 that has been loaded is brought to a position to be pressed by the pressing part 56 by the next stroke of the rod part 55.

[0071] According to the cable removal method using the device configuration shown in FIG. 19, it is possible to push the succeeding sheath tube 30 into the pipeline 2 at a fast pace, thereby making it possible to improve work efficiency. [Explanation of symbols]

[0072] 2...Pipeline 3. Manhole 4. Entrance and exit for workers 5. Cable 30....Sheath tube 31...Aperture 32...Aperture 33...Taper 34, 34'...Through hole 35, 35' through hole 36, 36' wire 37, 37' Loop section 38...Outer circumference taper 40 Hollow section 41 Guide piece 42... Expanded diameter part 43...Reduced diameter part 45, 45'···winch 48, 48' drums 50....Sheath tube press-fitting device 51 Main body 52...front arm 53... Posterior arm 54 Drive unit 55 Rod section 56 Pressing part 57 Signal cable 58 Operation switch 61 Jack (for height adjustment) 62 Jack (for front and rear positioning) 63 Jack (for adjusting front and rear positioning) 70 Relay guide device 71 Main body 75···Relay rod section 76 Pressing part 80···Winch (for cable) 83...Drums 85...Intermediate wire 90...Recovery materials 91...Cylindrical section 92 Opening 93...Lid part 95... Annular section 96... Annular part 97...Cylindrical section 100...Wire rod 102...Wire rod 105···Winch 108...Drums 115···Winch 118···Drums 120 Magazine parts 125...loading port 126... Closet opening 127... Extrusion opening X: The part where the cable sheath is stuck to the pipe Y: The point where the soil and sand accumulated in the pipe 2 has solidified, causing the cable 5 to come into close contact with the pipe 2.

Claims

[Claim 1] A cable removal method for removing a cable laid in a conduit, comprising: A preparation step of preparing a plurality of cylindrical sheath tubes having openings at both ends; a leading sheath tube insertion step of inserting a sheath tube between the conduit and the cable; a subsequent sheath tube insertion step of inserting a subsequent sheath tube such that an opening on the opposite side to the insertion direction of the sheath tube inserted immediately before is brought into contact with an opening on the insertion direction side of the subsequent sheath tube; A sheath tube recovery method that is carried out after a cable removal method is carried out, the method comprising: a pulling step of pulling the cable out of the pipeline by applying a pulling force to the cable; a wire passing step of passing a wire from one end of the pipeline to the other end of the pipeline; a tying step of tying the wire to a recovery member having an outer diameter larger than an outer diameter of the sheath tube at the other end side of the pipeline; a removal step of applying a tensile force to the wire at one end of the pipeline to remove the sheath tube from the one end of the pipeline.

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