Pipe inner surface cutting device and pipe cut-off method

Abstract

To provide an inner surface cutting device and a pipe cut-off method which can prevent cutting chips from remaining within a pipe.SOLUTION: A pipe inner surface cutting device 1 for cutting an inner peripheral surface 92 of a pipe (for example, branch pipe 9) composed of thermoplastic resin, includes a cutting head 2 which performs cutting while progressing in an axial direction of the pipe (branch pipe 9). The cutting head 2 includes a cutting chip recovery part 5 for recovering cutting chips generated due to cutting, in an opposite side to a direction of the progressing.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a pipe inner surface cutting device for cutting the inner surface of a pipe made of thermoplastic resin, and a pipe cutting method for cutting a pipe in order to remove an existing pipe made of thermoplastic resin extending from a main pipe. [Background technology]

[0002] Gas, water, and other supplies to consumers are provided by branch pipes that extend from a main pipe buried underground under roads or land managed by a city, prefecture, or country to the consumer's private property. Taking gas supply as an example, the main pipe for gas supply is buried underground under a public road. A branch pipe then extends from the main pipe toward the private property. The branch pipe is connected to the consumer's building, allowing the consumer to receive gas. Note that branch pipes are generally made of thermoplastic resins such as polyethylene.

[0003] When demolishing a building constructed on private property, branch pipes are removed before the demolition to prevent accidents such as gas leaks. When removing these branch pipes, it is desirable to cut the branch pipes as close as possible to the boundary between the public road and the private property (site boundary line) and to keep the length of the branch pipe remaining on the private property as short as possible. This is because if the length of the branch pipe remaining on the private property is long, the branch pipes are more likely to be damaged during the demolition of the building. In such cases, a pipe inner surface cutting device and a pipe cutting method disclosed in Patent Document 1, for example, are used for branch pipe removal work.

[0004] The removal of a branch pipe using the pipe inner surface cutting device and pipe cutting method disclosed in Patent Document 1 is carried out as follows.

[0005] First, a hole is drilled at the location where the branch pipe is buried to expose the branch pipe, and the exposed branch pipe is blocked with a squeeze tool. Then, the branch pipe is cut (first cut) downstream of the squeeze tool, and the downstream branch pipe is removed from the cut opening formed by the first cut.

[0006] Next, after removing the squeeze tool from the branch pipe, the elastic seal member is inserted into the branch pipe up to the vicinity of the property boundary line to temporarily close the branch pipe.

[0007] A pipe inner surface cutting device is then inserted through the cutting opening, and the pipe inner surface cutting device is used to cut the inner circumferential surface of the branch pipe downstream of the elastic seal member. This cutting is performed by inserting the cutting head of the pipe inner surface cutting device to a position adjacent to the elastic seal member, and then rotating the cutting head with an electric screwdriver while moving the cutting head toward the cutting opening. A plug member made of thermoplastic resin is then inserted through the cutting opening to a position adjacent to the elastic seal member, and the plug member is fused to the inner circumferential surface of the branch pipe. By fusing the plug member, the branch pipe is closed and gas is blocked. Furthermore, by cutting the inner circumferential surface of the branch pipe with the pipe inner surface cutting device, impurities such as oxide coatings are removed, which is expected to ensure reliable fusion.

[0008] Furthermore, an internal cutter is inserted into the branch pipe from the cutting opening, and the internal cutter is used to further cut (second cut) the branch pipe near the position where the plug member was fused, and the branch pipe downstream of the point where the second cut was made is removed.

[0009] According to the pipe inner surface cutting device and pipe cutting method described above, even if the excavation hole must be located away from the property line, the branch pipe can be cut as close to the property line as possible, and the length of the branch pipe remaining on private property can be made as short as possible. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Japanese Patent Application Publication No. 2023-121384 Summary of the Invention [Problem to be solved by the invention]

[0011] In the above-described pipe inner surface cutting device and pipe cutting method, the cutting head is moved toward the cutting opening while cutting the inner surface of the branch pipe, and therefore chips (swarf) generated by the cutting process remain inside the branch pipe. If chips remain inside the branch pipe, they may hinder the fusion of the plug member and result in insufficient closure of the branch pipe. Insufficient closure of the branch pipe may result in gas leakage, so it is desirable to prevent chips from remaining inside the branch pipe in order to ensure reliable fusion of the plug member.

[0012] SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has as its object to provide an internal cutting device and a pipe cutting method that can prevent chips from remaining inside the pipe. [Means for solving the problem]

[0013] In order to solve the above problems, the internal cutting device of the present invention has the following configuration.

[0014] (1) A pipe inner surface cutting device for cutting the inner surface of a pipe made of thermoplastic resin, characterized in that it is provided with a cutting head that performs the cutting while progressing along the axial direction of the pipe, and the cutting head is provided with a chip collection section on the opposite side of the direction of progression for collecting chips generated by the cutting.

[0015] When the cutting head performs cutting while moving along the axial direction of the pipe, chips are generated on the opposite side of the cutting head's direction of movement (hereinafter, the opposite side of the direction of movement is referred to as the "rear side"). However, according to the pipe inner surface cutting device described in (1) above, the cutting head is provided with a chip collection section for collecting chips on the opposite side of the direction of movement, so that chips can be collected while cutting. This prevents chips from remaining inside the pipe. Note that chips refer to all shavings generated by cutting the inner surface of the pipe.

[0016] (2) In the pipe inner surface cutting device described in (1), it is preferable that the chip collection section comprises a flexible shaft extending from the cutting head in the opposite direction to the direction of advancement, and a disk-shaped stopper provided at the tip of the flexible shaft for blocking chips generated by the cutting.

[0017] According to the pipe inner surface cutting device described in (2) above, the tip of the flexible shaft extending rearward from the cutting head is provided with a disk-shaped stopper for blocking chips generated by cutting. Therefore, chips generated behind the cutting head are blocked by the stopper and caught by the flexible shaft. This prevents chips from remaining behind the chip collection section. This prevents chips from remaining inside the pipe.

[0018] (3) In the pipe inner surface cutting device described in (2), it is preferable that the stopper has a diameter that is 93% or more and 97% or less of the inner diameter of the pipe.

[0019] If the diameter of the stopper is less than 93% of the inner diameter of the pipe, chips are more likely to slip through the gap between the stopper and the inner surface of the pipe and remain behind the stopper. Furthermore, if the diameter of the stopper exceeds 97% of the inner diameter of the pipe, the stopper and the inner surface of the pipe may interfere with each other, hindering the progress of the cutting head (i.e., reducing the efficiency of the cutting process). According to the pipe inner surface cutting device described in (3) above, the stopper is formed in a disk shape with a diameter of 93% to 97% of the inner diameter of the pipe, preventing chips from remaining behind the stopper and reducing the efficiency of the cutting process.

[0020] (4) In the tube inner surface cutting device described in (2) or (3), it is preferable that the device is provided with a rotation device that performs the cutting by rotating the cutting head and the flexible shaft around the axis of the flexible shaft, and that the stopper is arranged coaxially with the flexible shaft and is held rotatably relative to the flexible shaft.

[0021] When the cutting head is rotated by the rotating device to cut the inner surface of the pipe, if the stopper rotates with the cutting head, interference between the stopper and the inner surface of the pipe may hinder the rotation of the cutting head and reduce the efficiency of the cutting work. According to the pipe inner surface cutting device described in (4) above, the stopper is provided coaxially with the flexible shaft and is held rotatably relative to the flexible shaft, preventing the stopper from rotating with the flexible shaft. Therefore, even if the stopper interferes with the inner surface of the pipe, the rotation of the cutting head is not hindered, and reduction in the efficiency of the cutting work can be prevented.

[0022] (5) In the pipe inner surface cutting device described in any one of (2) to (4), it is preferable that the stopper is detachably held on the flexible shaft.

[0023] When a tube made of thermoplastic resin is cut, frizzy, thread-like chips are generated. These frizzy, thread-like chips become entangled with each other and cover the outer periphery of the flexible shaft. It is difficult to remove these tangled chips from the flexible shaft, for example, by pulling them radially outward from the flexible shaft. However, with the tube inner surface cutting device described in (5) above, the stopper is detachably held on the flexible shaft, so that by removing the stopper from the flexible shaft, the tangled chips can be easily pulled out from the tip of the flexible shaft.

[0024] (6) In the pipe inner surface cutting device described in any one of (2) to (5), the stopper is preferably made of a rubber composition having a hardness of 50° or more and 90° or less.

[0025] If the hardness of the stopper is less than 50°, the stopper may be bent as it is dragged along the inner circumferential surface of the pipe as it moves in the direction of travel of the cutting head. If the stopper is bent, chips are more likely to slip through the curved portion to the rear of the stopper and remain inside the pipe. However, according to the pipe inner surface cutting device described in (5) above, the stopper is made of a rubber composition with a hardness of 50° or more and 90° or less, so it is possible to prevent the stopper from being dragged along the inner circumferential surface of the pipe and bending, and thus prevent chips from remaining inside the pipe.

[0026] (7) In the pipe inner surface cutting device described in any one of (2) to (6), it is preferable that the flexible shaft is covered with a flexible hose. Note that the hose referred to here may be any flexible cylindrical pipe, and does not exclude a tube.

[0027] When cutting a tube made of thermoplastic resin, frizzy, thread-like chips are generated. These chips may become tangled on the surface of the flexible shaft, and once tangled, they are difficult to remove. However, with the tube inner surface cutting device described in (7) above, the flexible shaft is covered with a flexible hose, so chips can be prevented from becoming tangled on the flexible shaft.

[0028] Furthermore, in order to solve the above problems, the pipe cutting method of the present invention has the following configuration.

[0029] 8. A pipe cutting method for removing an existing pipe made of thermoplastic resin extending from a main pipe, comprising the steps of: excavating a hole at a position where the pipe is buried to expose the pipe; sealing the exposed pipe with a squeeze tool; making a first cut in the pipe downstream of the squeeze tool; removing the squeeze tool from the pipe; inserting an elastic seal member from a cut opening formed by the first cut in the pipe to a predetermined position in the pipe to temporarily seal the pipe; and removing an elastic seal member from the cut opening. the pipe inner surface cutting device described in (1) is inserted into the pipe, and the pipe inner surface is cut while the pipe inner surface cutting device is advanced toward the cutting opening, and chips generated by the cutting are collected; a plug member made of a thermoplastic resin is inserted into the pipe from the cutting opening, and the pipe is closed by fusing the plug member to the cut portion of the inner surface; an internal cutter is inserted into the pipe from the cutting opening, and a second cut of the pipe is made by the internal cutter downstream of the position where the plug member is fused.

[0030] According to the above-described pipe cutting method, by using a pipe inner surface cutting device, the inner surface of the pipe is cut and the chips generated by the cutting are collected, thereby preventing chips from remaining inside the pipe. [Effects of the Invention]

[0031] According to the pipe inner surface cutting device or pipe cutting method of the present invention, it is possible to prevent chips from remaining inside the pipe. [Brief explanation of the drawings]

[0032] [Figure 1] FIG. 2 is a diagram showing the configuration of a pipe inner surface cutting device. [Figure 2] FIG. [Figure 3]FIG. 2 is a plan view of the cutting head, with a portion shown in partial cross section. [Figure 4] FIG. 4 is a cross-sectional view taken along the line AA in FIG. 3, illustrating the cutting blade and the biasing means. [Figure 5] FIG. 10 is a diagram showing the state in which the cutting head and the chip collection unit are inserted into the branch pipe. [Figure 6] FIG. 1 is a diagram showing the buried state of a main pipe and branch pipes for gas supply. [Figure 7] 10A to 10C are diagrams showing a process of removing a branch pipe by the pipe cutting method according to the present embodiment. [Figure 8] 10A to 10C are diagrams showing a process of removing a branch pipe by the pipe cutting method according to the present embodiment. [Figure 9] 10A to 10C are diagrams showing a process of removing a branch pipe by the pipe cutting method according to the present embodiment. [Figure 10] 10A to 10C are diagrams showing a process of removing a branch pipe by the pipe cutting method according to the present embodiment. [Figure 11] 10A to 10C are diagrams showing a process of removing a branch pipe by the pipe cutting method according to the present embodiment. [Figure 12] 10A to 10C are diagrams showing a process of removing a branch pipe by the pipe cutting method according to the present embodiment. [Figure 13] 10A to 10C are diagrams showing a process of removing a branch pipe by the pipe cutting method according to the present embodiment. [Figure 14] FIG. 2 is a diagram illustrating a delivery device. [Figure 15] FIG. 10 is a diagram showing a state in which chips are collected by a chip collecting unit. [Figure 16] FIG. 10 is a diagram showing how chips are removed from a chip collection section. DETAILED DESCRIPTION OF THE INVENTION

[0033] (About the tube inner surface cutting device) First, an embodiment of a pipe inner surface cutting device 1 according to the present invention will be described with reference to FIGS. 1 to 6 and 15-16. FIG. 1 is a diagram showing the configuration of the pipe inner surface cutting device 1. FIG. 2 is a front view of the cutting head 2. FIG. 3 is a plan view of the cutting head 2, with a portion shown in partial cross section. FIG. 4 is a cross-sectional view taken along line AA in FIG. 3, and is a diagram for explaining the cutting blades 22, 23 and the biasing means 26. FIG. 5 is a diagram showing the cutting head 2 and the chip collection unit 5 inserted into a branch pipe 9 (an example of a pipe). FIG. 15 is a diagram showing the state in which chips have been collected by the chip collection unit 5. FIG. 16 is a diagram showing how chips are removed from the chip collection unit 5.

[0034] As shown in Figure 1, the main components of the pipe inner surface cutting device 1 are a cutting head 2, an electric screwdriver 3 (an example of a rotating device), a flexible shaft 4 connecting the cutting head 2 and the electric screwdriver 3, and a chip collection unit 5.

[0035] (About electric screwdrivers) The electric screwdriver 3 is a typical electric screwdriver, and a motor (not shown) built into the electric screwdriver 3 is driven by a battery 31 as a power source, and the rotational force of the motor is output by an output mechanism 32.

[0036] (About the flexible shaft) The flexible shaft 4 includes a hose-shaped outer tube 41 and a flexible rotating shaft (not shown) (hereinafter referred to as the flexible rotating shaft) inserted into the outer tube 41. The flexible rotating shaft has two axial ends, a driving-side shaft end 42 at the end of the electric screwdriver 3 and a driven-side shaft end 43 at the other end. The driving-side shaft end 42 and the driven-side shaft end 43 protrude from the outer tube 41, the driving-side shaft end 42 being connected to the output mechanism 32 of the electric screwdriver 3, and the driven-side shaft end 43 being connected to the cutting head 2. When a rotational force is output from the output mechanism 32 of the electric screwdriver 3, the flexible rotating shaft rotates inside the outer tube 41.

[0037] (About the cutting head) 2 and 3, the cutting head 2 mainly comprises a cutting head body 21, a pair of cutting blades 22 and 23, and a positioning roller 24. In the following description, the left side in the drawings (the flexible shaft 4 side of the cutting head 2) is referred to as the traveling direction side, and the opposite side is referred to as the rear side.

[0038] The cutting head body 21 is formed into a substantially cylindrical shape from, for example, stainless steel, and its central axis is the rotation axis A11. When the rotational force generated by the electric screwdriver 3 is transmitted to the cutting head body 21 by the flexible shaft 4, the cutting head body 21 rotates around the rotation axis A11.

[0039] The cutting head body 21 has a maximum outer diameter portion 216 in the axial center. A cylindrical hollow portion 211 is also provided in the cutting head body 21 coaxially with the maximum outer diameter portion 216. The hollow portion 211 opens at the end of the cutting head body 21 on the traveling direction side, thereby providing an opening portion 212 in the cutting head body 21. A connecting member 25 for connecting the driven-side shaft end portion 43 of the flexible shaft 4 is fixed to the opening portion 212.

[0040] The connecting member 25 is formed in a substantially cylindrical shape and is fixed to the opening 212 of the cutting head body 21 while being positioned coaxially with the cutting head body 21. A hexagonal hole 251, positioned coaxially with the connecting member 25, is drilled rearward in an end face 25a of the connecting member 25 opposite the cutting head body 21. Furthermore, a threaded through hole 252 communicating with the hexagonal hole 251 is provided in the outer circumferential surface of the connecting member 25. The driven-side shaft end 43 of the flexible shaft 4 can be inserted into the hexagonal hole 251, and the driven-side shaft end 43 inserted into the hexagonal hole 251 is fixed to the hexagonal hole 251 by a screw (not shown) that threads into the threaded through hole 252. Because the driven-side shaft end 43 is fixed to the hexagonal hole 251, when the flexible shaft 4 is rotated by the electric screwdriver 3, the cutting head body 21 rotates about the rotation axis A11.

[0041] The hollow portion 211 of the cutting head body 21 houses a biasing means 26. The biasing means 26 includes a compression coil spring 261 for generating a biasing force, and a pressing member 262 for transmitting the biasing force of the compression coil spring 261 to the cutting blades 22 and 23.

[0042] The pressing member 262 is formed in a substantially cylindrical shape so as to fit within the hollow portion 211. Its diameter is smaller than the diameter of the hollow portion 211, and it is slidable within the hollow portion 211 in the direction of the rotation axis A11 of the cutting head body 21. The inner peripheral surface of the hollow portion 211 serves as a guide for the pressing member 262 to slide.

[0043] An insertion hole 264 into which the compression coil spring 261 can be inserted is drilled toward the rear in an end face 262a on the moving direction side of the pressing member 262. A bottom face 265 of the insertion hole 264 abuts against an end portion on the axial tip side of the compression coil spring 261 inserted into the insertion hole 264.

[0044] The compression coil spring 261 is disposed coaxially with the hollow portion 211. Of both ends in the rotation axis direction, the end on the traveling direction side abuts against an end face 253 on the tip side of the connecting member 25, and the compression coil spring 261 is in a compressed state by a bottom face 265 of the pressing member 262 and the end face 253 of the connecting member 25. Because the connecting member 25 is in a fixed state, the compression coil spring 261 biases the connecting member 25 rearward.

[0045] An inclined surface that intersects obliquely with the direction of the rotation axis A11 and the direction of the rotation radius is provided at the rear end of the pressing member 262, and this inclined surface is a deflection portion 263 that deflects the direction of the biasing force of the compression coil spring 261 to the direction of the rotation radius. Angle X (see FIG. 4) of the deflection portion 263 (inclined surface) is not particularly limited, but in this embodiment it is 45 degrees with respect to the rotation axis A11.

[0046] A substantially rectangular parallelepiped cutting blade holder 213 is erected on the rear end surface 216a of the maximum outer diameter portion 216 of the cutting head body 21. The center of the substantially rectangular parallelepiped cutting blade holder 213 is located on the rotation axis A11. The cutting blade holder 213 is divided into a first holder portion 2131 and a second holder portion 2132, which face each other around the rotation axis A11, by a slit 214 provided in the center of the cutting blade holder 213. A pair of cutting blades 22, 23 are housed in the slit 214 so as to be slidable in the rotation radius direction (the up-and-down direction in FIG. 2 or FIG. 4). Four screws 281 are inserted into the rear end of the cutting blade holder 213, aligned perpendicular to the rotation axis A11, as shown in FIG. 2. Four miniature bearings 28 (see FIG. 4) are fixed in the slit 214 by the four screws 281, respectively. Furthermore, two screws 271 are inserted into the cutting blade holding part 213 on the moving direction side of the part where the screw 281 is inserted, and are aligned perpendicular to the rotation axis A11, similar to the screw 281. Two miniature bearings 27 (see FIG. 4) are fixed in the slit 214 by the two screws 271, respectively.

[0047] 3, connecting portions 217, 217 for connecting the chip collection unit 5 are provided on the rear end surface 213a of the cutting blade holding portion 213, and protrude rearward. The connecting portions 217, 217 are formed so that one protruding from the first holding portion 2131 and the other protruding from the second holding portion 2132 form a single column positioned coaxially with the rotation axis A11. The outer peripheral surfaces of the connecting portions 217, 217 are male threaded portions 217a provided with threads.

[0048] As shown in Figure 2, the cutting blades 22, 23 have their outer ends in the direction of the rotation radius protruding from the cutting blade holding portion 213, and the protruding ends are equipped with blade portions 221, 231 for cutting the inner surface 92 of the branch pipe 9 (see Figure 5).

[0049] As shown in Fig. 4, the cutting blades 22, 23 are provided with oblong holes 222, 232 that have a longitudinal direction parallel to the direction of the radius of rotation of the cutting head 2 and that penetrate the cutting blades 22, 23 in the thickness direction. Miniature bearings 27 fixed in slits 214 are located inside the oblong holes 222, 232. Furthermore, two miniature bearings 28 fixed in slits 214 contact the rear end faces 23a of the cutting blades 22, 23. Guided by these miniature bearings 27, 28, the cutting blades 22, 23 are slidable within the range of the longitudinal length of the oblong holes 222, 232 in the direction of the radius of rotation of the cutting head 2 (the up-and-down direction in Fig. 2 or 4).

[0050] An inclined surface that intersects obliquely with the direction of the rotation axis A11 and the direction of the rotation radius is provided on the traveling direction side of the end portions where the pair of cutting blades 22, 23 face each other, and this inclined surface is a deflector 223, 233 for deflecting the direction of the biasing force of the compression coil spring 261. The angle X of the deflector 223, 233 (inclined surface) is 45 degrees with respect to the rotation axis A11, similar to the deflector 263. The deflector 263 of the pressing member 262, which is biased rearward by the biasing force of the compression coil spring 261, abuts against the deflector 223, 233. The biasing force of the compression coil spring 261 is deflected into a force in the direction of the rotation radius by the deflector 223, 233, 263, so that each of the pair of cutting blades 22, 23 is biased outward in the direction of the rotation radius (the up-and-down direction in FIG. 4 ). In this embodiment, both the cutting blades 22, 23 and the pressing member 262 of the urging means 26 are provided with the deflection portions 223, 233, 263, but it is also possible to provide a deflection portion (i.e., an inclined surface) on either the cutting blades 22, 23 or the pressing member 262.

[0051] The positioning roller 24 is cylindrical and coaxially positioned with the rotation axis A11, covering an outer peripheral surface 215 (see FIG. 3) of the cutting head body 21 on the traveling direction side of the maximum outer diameter portion 216. A needle bearing 29 is disposed between the outer peripheral surface 215 of the cutting head body 21 and an inner peripheral surface 242 of the positioning roller 24, so that the positioning roller 24 is rotatable relative to the cutting head body 21. The rotation axis of the positioning roller 24 is coaxial with the rotation axis A11. The diameter of the positioning roller 24 is larger than the diameter of the maximum outer diameter portion 216 and slightly smaller than the inner diameter of the branch pipe 9 (e.g., 32.85 to 34.35 mm). This positions the cutting head 2 so that the rotation axis A11 of the cutting head 2 is substantially aligned with the pipe axis of the branch pipe 9.

[0052] (About the chip collection section) The chip collection unit 5 includes a shaft 6 and a stopper 7. The shaft 6 and the stopper 7 will be described below. Note that here too, the left side in the drawing (the cutting head 2 side of the chip collection unit 5) is referred to as the traveling direction side, and the opposite side is referred to as the rear side.

[0053] (About the shaft) The shaft portion 6 mainly comprises a wire rope 61 (an example of a flexible shaft) and a vinyl hose 62 (an example of a hose).

[0054] The vinyl hose 62 is a typical vinyl hose and is flexible. The wire rope 61 is inserted through the vinyl hose 62, and therefore the outer circumferential surface of the wire rope 61 is covered by the vinyl hose 62. The wire rope 61 is also flexible, and the vinyl hose 62 and the wire rope 61 can bend together. Note that in this embodiment, the vinyl hose 62 is given as an example of a hose, but any flexible cylindrical tube may be used, such as a resin tube.

[0055] The wire rope 61 is, for example, a general wire rope with a plated surface. The diameter of the wire rope 61 is not particularly limited, but in this embodiment it is approximately 4 mm. The length of the wire rope 61 is not particularly limited, but in this embodiment it is approximately 110 mm.

[0056] Of the two axial ends of the wire rope 61, a first joint fitting 63 is connected to the end on the traveling direction side, and a second joint fitting 64 is connected to the end on the rear side.

[0057] The first joint fitting 63 is formed in a substantially cylindrical shape and is positioned coaxially with the wire rope 61. An insertion hole 631 is drilled in the rear end face of the first joint fitting 63, facing the direction of travel. The end of the wire rope 61 facing the direction of travel is inserted into the insertion hole 631, and the wire rope 61 and the first joint fitting 63 are joined by brazing. Approximately half of the first joint fitting 63 from the center in the axial direction toward the direction of travel is an externally threaded portion 632 with a thread provided on its outer peripheral surface. The externally threaded portion 632 protrudes from the vinyl hose 62 and is threadedly engaged with a mounting bracket 65 that connects the wire rope 61 to the cutting head 2.

[0058] Mounting bracket 65 is formed in a cylindrical shape, with its central axis positioned on rotation axis A11. A recess 651 is drilled rearward as a cylindrical space on the end face of mounting bracket 65 on the traveling direction side. The inner circumferential surface of recess 651 is an internally threaded portion 651a with a screw thread. Furthermore, a screw hole 652 is provided at the bottom of recess 651, coaxially with recess 651, and passes through the rear end face of mounting bracket 65.

[0059] The male threaded portion 632 of the first joint fitting 63 connected to the wire rope 61 is threadedly engaged with the screw hole 652. In addition, the male threaded portions 217a provided on the connecting portions 217, 217 of the cutting head body 21 are threadedly engaged with the female threaded portion 651a. In this way, the wire rope 61 and the cutting head body 21 (i.e., the shaft portion 6 and the cutting head 2) are connected via the mounting fitting 65.

[0060] Since the wire rope 61 and the cutting head body 21 are connected, when the cutting head body 21 is rotated by the electric screwdriver 3, the wire rope 61 also rotates in the same direction. At this time, the rotation axes of the cutting head body 21 and the wire rope 61 are aligned.

[0061] The second joint fitting 64 is formed in a substantially cylindrical shape and is positioned coaxially with the wire rope 61. An insertion hole 641 is drilled toward the rear in the end face of the second joint fitting 64 on the traveling direction side. The rear end of the wire rope 61 is inserted into the insertion hole 641, and the wire rope 61 and the second joint fitting 64 are joined by brazing. A female thread portion 642 is drilled toward the traveling direction in the rear end face of the second joint fitting 64. Approximately half of the second joint fitting 64 from the center in the axial direction to the rear protrudes from the vinyl hose 62, and the female thread portion 642 is used to connect the wire rope 61 to a stopper portion 7, which will be described later.

[0062] (Regarding the stopper) The stopper portion 7 has a stopper 71, a mounting bracket 72, and a bearing 73 as main components.

[0063] The material of the stopper 71 is preferably a rubber composition having a hardness of 50° or more and 90° or less, and in this embodiment, nitrile rubber having a hardness of 70° is used. The stopper 71 is formed in a disk shape and is positioned coaxially with the wire rope 61. The diameter of the stopper 71 is preferably 93% or more and 97% or less of the inner diameter of the branch pipe 9, and is approximately 32 mm in this embodiment. The thickness of the stopper 71 is not particularly limited, but is, for example, approximately 5 mm. The corners of the outer periphery of the stopper 71 are chamfered to form C-chamfers 711. The corners of the outer periphery of the stopper 71 may also be R-chamfered. The stopper 71 is also provided with a mounting hole 712 that passes through the stopper 71 along its axis.

[0064] Mounting bracket 72 is formed in a roughly cylindrical shape, and holds stopper 71 by being inserted into mounting hole 712 of stopper 71. Stopper 71 is sandwiched between flat washers 74 on both sides in the axial direction, and is prevented from coming off on the rear side by a C-shaped retaining ring 75, and on the traveling direction side by a flange portion 721 provided on the end of mounting bracket 72 on the traveling direction side so as to protrude radially.

[0065] A cylindrical recess 722 is drilled toward the direction of travel in the rear end face of mounting bracket 72. In addition, an insertion hole 723 is provided at the bottom of recess 722, coaxially with recess 722, and penetrates through the end face of mounting bracket 72 in the direction of travel.

[0066] The bearing 73 is press-fit into the recess 722 with its rotation axis positioned coaxially with the shaft portion 6 (wire rope 61). This makes the outer ring of the bearing 73 integral with the mounting bracket 72. A screw 76 is inserted into the center of the bearing 73 from the rear side, and this screw 76 passes through the insertion hole 723 and threads into the female thread portion 642 of the second joint fitting 64. This connects the inner ring of the bearing 73 to the shaft portion 6. With the outer and inner rings of the bearing 73 fixed in this way, the stopper 71 and mounting bracket 72 are integral and can rotate around the axial center of the shaft portion 6 (wire rope 61).

[0067] Furthermore, since the stopper portion 7 and the shaft portion 6 (wire rope 61) are connected by a screw 76, the stopper portion 7 can be removed from the shaft portion 6 by removing the screw 76.

[0068] In the pipe inner surface cutting device 1 having the above-described configuration, as shown in FIG. 5 , when the cutting head 2 is inserted into the branch pipe 9 through an opening (e.g., cutting opening 91) of the branch pipe 9, the cutting blades 22, 23, which are biased outward in the radial direction by the biasing means 26, are pressed against the inner circumferential surface 92 of the branch pipe 9 from a direction perpendicular to the pipe axis of the branch pipe 9. When the cutting head 2 is rotated by the rotational force of the electric screwdriver 3, the cutting blades 22, 23 cut the inner circumferential surface 92 of the branch pipe 9. This cutting is performed while the cutting head 2 moves along the pipe axis of the branch pipe 9 from the inserted position within the branch pipe 9 toward the opening (cutting opening 91) as indicated by arrow Y11. The movement of the cutting head 2 in the direction of arrow Y11 may be performed by an operator located on the opening (cutting opening 91) side pulling the flexible shaft 4, or by feeding out the flexible shaft 4 using a feeding device 18 (see FIG. 14 ), which will be described later.

[0069] As the cutting head 2 cuts while moving in the direction of arrow Y11, chips are generated behind the cutting head 2. However, because the chip collection unit 5 is located behind the cutting head 2, the chips are blocked by the stopper 71 of the stopper unit 7 and entangled in the shaft 6. Therefore, when the cutting head 2 is removed from the opening (cutting opening 91) of the branch pipe 9, the chips are scraped out by the stopper unit 7, making it easy to collect them. This prevents chips from remaining inside the branch pipe 9. Note that chips generally refer to all chips generated by cutting the inner surface 92 of the branch pipe 9.

[0070] Furthermore, because the stopper 71 is rotatable around the axis of the shaft portion 6 (wire rope 61), the stopper 71 does not rotate together with the rotation of the cutting head 2. Therefore, even if the rotation axis A11 is shaken during rotation of the cutting head 2, causing interference between the stopper 71 and the inner peripheral surface 92 of the branch pipe 9, the rotation of the cutting head 2 is not impeded, and a decrease in cutting workability can be prevented.

[0071] Furthermore, the diameter of the stopper 71 is set to 93% or more and 97% or less of the inner diameter of the branch pipe 9 (approximately 32 mm in this embodiment), so that interference between the stopper 71 and the inner surface 92 of the branch pipe 9 can be prevented as much as possible from hindering the progress of the cutting head 2 in the direction of arrow Y11, while also preventing chips from slipping past the rear side of the stopper 71.

[0072] Furthermore, since the stopper 71 is made of a rubber composition having a hardness of 50° or more and 90° or less (nitrile rubber having a hardness of 70° in this embodiment), the stopper 71 can be prevented from being dragged by the inner peripheral surface 92 of the branch pipe 9 and being bent when the cutting head 2 advances in the direction of the arrow Y11. This prevents chips from slipping past the stopper 71 and remaining in the branch pipe 9.

[0073] Furthermore, when a branch pipe 9 made of thermoplastic resin is cut, frizzy, thread-like chips are generated. These frizzy, thread-like chips become entangled with one another, covering the outer periphery of the shank 6, as shown in chips S in FIG. 15 . It is difficult to remove these tangled chips S from the shank 6, for example, by pulling them radially outward. However, since the stopper 7 can be removed from the shank 6, the tangled chips S can be easily pulled out from the tip of the shank 6 by unscrewing the screws 76 and removing the stopper 7 from the shank 6, as shown in FIG. 16 . In addition, the shank 6 has a vinyl hose 62 that covers the wire rope 61, preventing the chips S from becoming entangled on the outer periphery of the wire rope 61. This makes it easy to remove the chips S from the shank 6.

[0074] (Pipe cutting method) Next, an embodiment of the pipe cutting method according to the present invention will be described with reference to Figures 6 to 14. Figure 6 is a diagram showing the buried state of a main pipe 8 and a branch pipe 9 for gas supply. Figures 7 to 13 are diagrams showing the process of removing the branch pipe 9 using the pipe cutting method according to this embodiment. Figure 14 is a diagram explaining a delivery device 18.

[0075] Gas is supplied to consumers through a branch pipe extending from a main pipe buried underground under roads or land managed by a city, prefecture, or country to the consumer's private property. For example, as shown in FIG. 6 , a main pipe 8 for gas supply is buried underground under a public road R. A branch pipe 9 extends from the main pipe 8 toward private property P. The branch pipe 9 is connected to the consumer's building 10, thereby supplying gas to the consumer. Note that a pipe made of a thermoplastic resin such as polyethylene is generally used for the branch pipe 9. A pipe cutting method according to this embodiment will be described using as an example a process for removing a branch pipe 9 buried in private property P.

[0076] First, as shown in FIG. 7 , a drilling hole 13 is drilled on private property P, and a branch pipe 9 is exposed. The drilling hole 13 is drilled to avoid buildings 10, plants 11, parking lots 12 made of asphalt or concrete, and the like on private property P. In this example, the drilling hole 13 is drilled between the building 10 and the parking lot 12. The size of the drilling hole 13 is appropriately set to a size that allows a worker to work inside the drilling hole 13.

[0077] Next, as shown in Fig. 8, the exposed branch pipe 9 is blocked with a squeeze tool 14, and then the branch pipe 9 is cut downstream of the squeeze tool 14 (first cut). The squeeze tool 14 used is a general squeeze tool that compresses and deforms the branch pipe 9 from the outside, thereby blocking the gas. The portion of the branch pipe 9 downstream from the cut point will be removed during the demolition work of the building 10, but is not shown in Figs. 8 to 14.

[0078] Next, as shown in Fig. 9, elastic seal member 15 is attached to cut opening 91 formed by the first cut. This is to prevent gas from leaking from cut opening 91 when squeezing tool 14 is removed. In order to attach elastic seal member 15 to cut opening 91, it is necessary to ensure a sufficient distance (for example, several tens of centimeters) between cut opening 91 and squeezing tool 14. Elastic seal member 15 is, for example, a rubber stopper made of polyethylene.

[0079] Next, squeeze tool 14 is removed from branch pipe 9, and as shown in Figure 10, elastic seal member 15 is inserted, for example, up to the vicinity of property boundary line B11 on the private property P side. The diameter of elastic seal member 15 is slightly larger than the inner diameter of branch pipe 9, and it is press-fitted into branch pipe 9. This press-fitting blocks the gas flowing through branch pipe 9. Note that elastic seal member 15 is removable from branch pipe 9, and does not completely block branch pipe 9. Therefore, here, the blocking of gas by elastic seal member 15 is referred to as temporary blockage of branch pipe 9.

[0080] 11, the cutting head 2 is inserted into the branch pipe 9 from the cutting opening 91, with the stopper portion 7 at the front, and positioned adjacent to the elastic sealing member 15. Then, the electric screwdriver 3 is operated to rotate the cutting head 2 inside the branch pipe 9, and the cutting head 2 cuts the inner circumferential surface 92 of the branch pipe 9 downstream of the elastic sealing member 15.

[0081] Cutting by the cutting head 2 is performed while the cutting head 2 moves along the pipe axis of the branch pipe 9 toward the cutting opening 91 (i.e., in the direction of arrow Y11). The movement of the cutting head 2 may be performed by an operator standing on the cutting opening 91 side pulling the flexible shaft 4, or may be performed by feeding out the flexible shaft 4 using a feeding device 18 shown in FIG.

[0082] The delivery device 18 comprises a pedestal 181 erected in the drilled hole 13 and a holding jig 182 that holds the flexible shaft 4. The pedestal 181 has a fixing portion 183 for fixing the pedestal 181 to the bottom of the drilled hole 13. The pedestal 181 also has a gripping portion 184 that grips the branch pipe 9 to prevent misalignment with the branch pipe 9. The pedestal 181 also has a drive mechanism that allows the holding jig 182 to move at a constant speed on the pedestal 181 along the axial direction of the flexible shaft 4 (the direction indicated by arrow Y12 in FIG. 14 ). Therefore, by moving the holding jig 182 holding the flexible shaft 4 toward the upper end side of the pedestal 181, opposite the bottom side of the drilled hole 13, the flexible shaft 4 is delivered in the axial direction of the flexible shaft 4, and the cutting head 2 is moved at a constant speed along the pipe axis of the branch pipe 9 toward the cutting opening 91. The moving speed of the holding jig 182 on the pedestal 181 is set appropriately based on the rotation speed of the cutting head 2 to a speed that allows for uniform cutting of the inner peripheral surface 92 of the branch pipe 9. The pedestal 181 is erected at an inclined angle relative to the bottom surface of the drilling hole 13 in order to make the bending radius of the flexible shaft 4 gentle. However, this does not exclude erecting the pedestal 181 at a right angle relative to the bottom surface of the drilling hole 13.

[0083] As the cutting head 2 cuts while progressing in the direction of arrow Y11, chips are generated behind the cutting head 2. As the stopper portion 7 is located behind the cutting head 2, the stopper 71 of the stopper portion 7 blocks the chips. Therefore, when the cutting head 2 is removed from the opening (cutting opening 91) of the branch pipe 9, the stopper portion 7 scrapes out the chips, preventing them from remaining inside the branch pipe 9.

[0084] After the cutting by the cutting head 2 is completed, as shown in FIG. 12 , a plug member 16 made of thermoplastic resin is inserted into the branch pipe 9 through the cutting opening 91. At this time, the plug member 16 is inserted to a position adjacent to the downstream side of the elastic seal member 15. The plug member 16 is, for example, an electrofusion plug as disclosed in JP 2021-1618 A, and is fused to the portion of the inner circumferential surface 92 of the branch pipe 9 that was cut by the pipe inner surface cutting device 1. Cutting the inner circumferential surface 92 of the branch pipe 9 removes impurities such as an oxide film, and the stopper portion 7 prevents chips from remaining in the branch pipe 9. This ensures that the plug member 16 can be fused without being hindered by impurities or chips. The fusion of the plug member 16 can be reliably performed. The fusion of the plug member 16 closes the branch pipe 9, shutting off the gas.

[0085] After the fusion of the plug member 16 is completed, as shown in Fig. 13, the inner surface cutter 17 is inserted into the branch pipe 9 from the cutting opening 91, and the branch pipe 9 is cut with the inner surface cutter 17 downstream of the position where the plug member 16 was fused (second cut). The cutting position is near the downstream end of the plug member 16. Then, the portion of the branch pipe 9 downstream of the cut portion is removed.

[0086] As described above, elastic seal member 15 is positioned near property boundary line B11, and the second cut is made near the downstream end of plug member 16 positioned adjacent to elastic seal member 15, so that the length L11 of the remaining branch pipe 9 (the length from property boundary line B11 to cut opening 91) is approximately the sum (about 20 to 30 cm) of the lengths of elastic seal member 15 and plug member 16. In this way, by being able to cut branch pipe 9 at a position closer to property boundary line B11, the risk of damaging the remaining branch pipe 9 during demolition work of building 10, for example, is reduced.

[0087] The remaining length L11 of the branch pipe 9 can be further shortened by positioning the elastic sealing member 15 and the plug member 16 further back in the branch pipe 9. In other words, the positions of the elastic sealing member 15 and the plug member 16 within the branch pipe 9 are appropriately set according to the target length L11. Leaving the branch pipe 9 protruding by length L11 toward the private property P is done when there is a possibility that the branch pipe 9 will be reused due to reconstruction of the building 10, for example. Therefore, if there are no plans to reuse the branch pipe 9, the elastic sealing member 15 and the plug member 16 may be inserted into the branch pipe 9 to a position on the road R side of the property line B11, where the second cut can be made.

[0088] (About the effects) As described above, according to the pipe inner surface cutting device 1 according to this embodiment, (1) A pipe inner surface cutting device 1 for cutting the inner surface 92 of a pipe (e.g., a branch pipe 9) made of thermoplastic resin is characterized in that it is provided with a cutting head 2 that performs cutting while progressing along the axial direction of the pipe (branch pipe 9), and the cutting head 2 is provided with a chip collection section 5 on the opposite side of the direction of progression for collecting chips generated by cutting.

[0089] When the cutting head 2 performs cutting while moving along the axial direction of the pipe (branch pipe 9), chips are generated on the opposite side of the moving direction of the cutting head 2 (i.e., the rear side). However, according to the pipe inner surface cutting device 1 described in (1) above, the cutting head 2 is provided with a chip collection unit 5 for collecting chips on the opposite side of the moving direction, so that chips can be collected while cutting. This makes it possible to prevent chips from remaining inside the pipe (branch pipe 9).

[0090] (2) In the pipe inner surface cutting device 1 described in (1), it is preferable that the chip collection section 5 includes a flexible shaft (e.g., a wire rope 61) extending from the cutting head 2 in the opposite direction (rearward) to the direction of travel, and a disk-shaped stopper 71 provided at the tip of the flexible shaft (wire rope 61) for blocking chips generated by cutting.

[0091] According to the pipe inner surface cutting device 1 described in (2) above, the tip of the flexible shaft (wire rope 61) extending to the rear side of the cutting head 2 is provided with a disk-shaped stopper 71 for blocking chips generated by cutting, so that chips generated on the rear side of the cutting head 2 are blocked by the stopper 71 and entangled by the flexible shaft (wire rope 61). As a result, chips do not remain on the rear side of the chip collection unit 5. This makes it possible to prevent chips from remaining inside the pipe (branch pipe 9).

[0092] (3) In the pipe inner surface cutting device 1 described in (2), it is preferable that the stopper 71 has a diameter that is 93% or more and 97% or less of the inner diameter of the pipe (branch pipe 9).

[0093] If the diameter of the stopper 71 is less than 93% of the inner diameter of the pipe (branch pipe 9), chips are more likely to slip through the gap between the stopper 71 and the inner peripheral surface 92 of the pipe (branch pipe 9) and remain behind the stopper 71. Furthermore, if the diameter of the stopper 71 exceeds 97% of the inner diameter of the pipe, the stopper 71 and the inner peripheral surface 92 of the pipe (branch pipe 9) may interfere with each other, hindering the progress of the cutting head 2 (i.e., reducing the efficiency of the cutting process). According to the pipe inner surface cutting device 1 described in (3) above, the stopper 71 is formed in a disk shape with a diameter that is 93% to 97% of the inner diameter of the pipe (branch pipe 9). This prevents chips from remaining behind the stopper 71 and prevents a reduction in the efficiency of the cutting process.

[0094] (4) In the pipe inner surface cutting device 1 described in (2) or (3), it is preferable that the device is provided with a rotating device (e.g., an electric screwdriver 3) that performs cutting by rotating the cutting head 2 and the flexible shaft (wire rope 61) around the axis of the flexible shaft (wire rope 61), and that the stopper 71 is arranged coaxially with the flexible shaft (wire rope 61) and is held rotatably relative to the flexible shaft (wire rope 61).

[0095] When the cutting head 2 is rotated by a rotating device to cut the inner peripheral surface 92 of the pipe (branch pipe 9), if the stopper 71 rotates with the cutter head 2, interference between the stopper 71 and the inner peripheral surface 92 of the pipe (branch pipe 9) may hinder the rotation of the cutter head 2 and reduce the efficiency of the cutting work. According to the pipe inner surface cutting device 1 described in (4) above, the stopper 71 is provided coaxially with the flexible shaft (wire rope 61) and is held rotatably relative to the flexible shaft (wire rope 61), preventing the stopper 71 from rotating with the flexible shaft. Therefore, even if the stopper 71 interferes with the inner peripheral surface 92 of the pipe (branch pipe 9), the rotation of the cutter head 2 is not hindered, and reduction in the efficiency of the cutting work can be prevented.

[0096] (5) In the pipe inner surface cutting device 1 described in any one of (2) to (4), it is preferable that the stopper 71 is detachably held on the flexible shaft (wire rope 61).

[0097] When a pipe (branch pipe 9) made of thermoplastic resin is cut, frizzy, thread-like chips are generated. These frizzy, thread-like chips become entangled with each other and cover the outer periphery of the flexible shaft (wire rope 61). It is difficult to remove these entangled chips S from the flexible shaft (wire rope 61), for example, by pulling them radially outward from the flexible shaft (wire rope 61). However, according to the pipe inner surface cutting device 1 described in (5) above, the stopper 71 is detachably held to the flexible shaft (wire rope 61). Therefore, by removing the stopper 71 from the flexible shaft (wire rope 61), the entangled chips S can be easily pulled out from the tip of the flexible shaft (wire rope 61).

[0098] (6) In the pipe inner surface cutting device 1 described in any one of (2) to (5), the stopper 71 is preferably made of a rubber composition having a hardness of 50° or more and 90° or less.

[0099] If the hardness of the stopper 71 is less than 50°, there is a risk that the stopper 71 will be bent due to being dragged by the inner peripheral surface 92 of the pipe (branch pipe 9) as the stopper 71 moves in the direction of travel of the cutting head 2. If the stopper 71 is bent, there is a high possibility that chips will slip through the curved portion to the rear side of the stopper 71 and remain in the pipe (branch pipe 9). However, according to the pipe inner surface cutting device 1 described in (5) above, the stopper 71 is made of a rubber composition having a hardness of 50° or more and 90° or less, and therefore it is possible to prevent the stopper 71 from being dragged by the inner peripheral surface 92 of the pipe (branch pipe 9) and bending, and thus prevent chips from remaining in the pipe (branch pipe 9).

[0100] (7) In the pipe inner surface cutting device 1 described in any one of (2) to (6), it is preferable that the flexible shaft is covered with a flexible hose (for example, a vinyl hose 62).

[0101] When a pipe (branch pipe 9) made of thermoplastic resin is cut, frizzy, thread-like chips are generated. These chips may become tangled on the surface of the flexible shaft (wire rope 61), and once tangled on the surface of the flexible shaft, they are difficult to remove. However, with the pipe inner surface cutting device 1 described in (7) above, the flexible shaft (wire rope 61) is covered with a flexible hose (vinyl hose 62), so that chips can be prevented from becoming tangled on the flexible shaft (wire rope 61).

[0102] Furthermore, according to the pipe cutting method of this embodiment, in order to remove an existing pipe (branch pipe 9) made of thermoplastic resin extending from a main pipe 8, the pipe (branch pipe 9) is cut by providing an excavation hole 13 at a position where the pipe (branch pipe 9) is buried, the pipe (branch pipe 9) is exposed, the exposed pipe (branch pipe 9) is blocked with a squeeze tool 14, a first cut is made on the pipe (branch pipe 9) downstream of the squeeze tool 14, the squeeze tool 14 is removed from the pipe (branch pipe 9), and an elastic seal member 15 is inserted from a cut opening 91 formed by the first cut on the pipe (branch pipe 9) to a predetermined position on the pipe (branch pipe 9) (for example, near the property boundary line B11 on the private land P side). the pipe (branch pipe 9) is temporarily blocked by the cutting opening 91, the pipe inner surface cutting device 1 described in any one of (1) to (7) above is inserted from the cutting opening 91, the pipe inner surface cutting device 1 is advanced toward the cutting opening 91 to cut the inner circumferential surface 92 of the pipe (branch pipe 9) and chips generated by the cutting are collected, a plug member 16 made of thermoplastic resin is inserted into the pipe (branch pipe 9) from the cutting opening 91, and the pipe (branch pipe 9) is blocked by fusing the plug member 16 to the cut portion of the inner circumferential surface 92, an inner surface cutter 17 is inserted into the pipe (branch pipe 9) from the cutting opening 91, and a second cut of the pipe (branch pipe 9) is made by the inner surface cutter 17 downstream of the position where the plug member 16 was fused.

[0103] According to the above-described pipe cutting method, by using the pipe inner surface cutting device 1, the inner surface 92 of the pipe (branch pipe 9) is cut and the chips generated by the cutting are collected, thereby preventing chips from remaining inside the pipe (branch pipe 9).

[0104] The above-described embodiments are merely examples and do not limit the present invention in any way. Therefore, various improvements and modifications of the present invention are possible without departing from the spirit and scope of the present invention. For example, the pipe cutting method and pipe inner surface cutting device in the above-described embodiments are described using a pipe for supplying gas as an example, but are not limited thereto and can also be applied to a pipe for supplying drinking water. [Explanation of symbols]

[0105] 1 Tube inner surface cutting device 2 cutting heads 5 Chip collection section 9 Branch pipe (example of pipe) 61 Wire rope (an example of a flexible shaft) 71 Stopper 92 Inner peripheral surface

Claims

1. A pipe inner surface cutting device for cutting the inner surface of a pipe made of thermoplastic resin, a cutting head that performs the cutting while progressing along the axial direction of the pipe; the cutting head is provided with a chip collecting section on the opposite side of the direction of travel for collecting chips generated by the cutting; A pipe inner surface cutting device characterized by the above.

2. 2. The pipe inner surface cutting device according to claim 1, The chip collection unit is a flexible shaft extending from the cutting head in a direction opposite to the direction of travel; a disk-shaped stopper provided at the tip of the flexible shaft for blocking chips generated by the cutting; To have A pipe inner surface cutting device characterized by the above.

3. 3. The pipe inner surface cutting device according to claim 2, the stopper has a diameter that is 93% or more and 97% or less of the inner diameter of the tube; A pipe inner surface cutting device characterized by the above.

4. 3. The pipe inner surface cutting device according to claim 2, a rotation device that rotates the cutting head and the flexible shaft around the axis of the flexible shaft to perform the cutting; the stopper is provided coaxially with the flexible shaft and is held rotatably relative to the flexible shaft; A pipe inner surface cutting device characterized by the above.

5. 3. The pipe inner surface cutting device according to claim 2, the stopper is detachably held on the flexible shaft; A pipe inner surface cutting device characterized by the above.

6. 3. The pipe inner surface cutting device according to claim 2, the stopper is a rubber composition having a hardness of 50° or more and 90° or less; A pipe inner surface cutting device characterized by the above.

7. 3. The pipe inner surface cutting device according to claim 2, the flexible shaft is covered with a flexible hose; A pipe inner surface cutting device characterized by the above.

8. 1. A pipe cutting method for cutting an existing pipe made of thermoplastic resin extending from a main pipe in order to remove the pipe, comprising: exposing the pipe by drilling a hole at the location where the pipe is buried; closing the exposed tube with a squeeze tool and making a first cut in the tube downstream of the squeeze tool; removing the squeeze tool from the tube; an elastic sealing member is inserted from the cut opening formed by the first cut of the tube to a predetermined position of the tube to temporarily close the tube; a pipe inner surface cutting device according to any one of claims 1 to 7 being inserted into the cutting opening, and the pipe inner surface is cut while the pipe inner surface cutting device is advanced toward the cutting opening, and chips generated by the cutting are collected; a plug member made of a thermoplastic resin is inserted into the pipe from the cut end, and the plug member is fused to the cut portion of the inner circumferential surface to close the pipe; inserting an internal cutter into the pipe from the cutting opening, and performing a second cut of the pipe with the internal cutter downstream of the position where the plug member is fused; A pipe cutting method comprising:

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