JP2018167291A - Method of manufacturing metallic pipe, die, and metallic pipe - Google Patents

Abstract

To provide a method of manufacturing a metallic pipe for groundwater drainage work, which can be easily coupled and which can discharge groundwater, a die for use in the same, and the metallic pipe for the groundwater drainage work, which is manufactured by them.SOLUTION: A metallic pipe 1 for groundwater drainage work comprises a body part 6, one pipe end 7, and a tapered part 8 for connecting the body part 6 and the pipe end 7 together. An outer peripheral surface 4 of a convex part 11 of the pipe end 7 is positioned on the inside with respect to an inner peripheral surface 5 of a convex part 10 of the body part 6, in a view in a direction of the central axis C. An outer peripheral surface 4 of a concave part 14 of the pipe end 7 is positioned on the inside with respect to an inner peripheral surface 5 of a concave part 13 of the body part 6, in the view in the direction of the central axis C.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method of manufacturing a metal tube, a die used for the method, and a metal tube manufactured by them.

  A landslide is a phenomenon in which the ground (landslide block) above the slip surface moves downward along the slip surface generated in the ground. Landslide occurs when the groundwater level rises due to rain, snow, etc., and the landslide block cannot stay on the slope due to the buoyancy of the groundwater.

  There are a deterrent work and a restraint work as measures to suppress such a landslide. The deterrent is a measure to stop the landslide using the resistance of the structure, and a typical example is a pit. On the other hand, suppression works are measures to change natural conditions such as topography and groundwater conditions, and representative examples include groundwater drainage works.

  Currently, horizontal hole boring drainage is adopted as groundwater drainage. Such drainage works to eliminate underground groundwater and reduce the moisture content of the landslide mass. In the drainage work, excavation is performed with an elevation angle of 5 to 10 degrees, and the hole retaining pipe is inserted after the excavation. As the hole holding tube, a metal tube having a plurality of through holes formed on the surface is usually used.

  However, the production of the hole-holding tube is complicated and the productivity is low. When manufacturing a hole holding tube from a metal tube, it is necessary to make a hole in the curved surface with a drill or gas cut. There is also a method of making a metal tube by making a hole in a metal plate before forming the metal tube by drilling or gas cutting, and then bending the metal plate. However, any of the methods is complicated in perforating work and is low in productivity.

  Therefore, it has been studied to use a metal tube having an uneven outer peripheral surface in place of the hole-holding tube. When using a metal pipe having an uneven outer peripheral surface for groundwater drainage work, it is necessary to connect a plurality of the metal pipes. In general, the metal pipes are connected by screw joints or welding.

  However, it is difficult to cut a screw at the end of a metal tube having an uneven outer peripheral surface. In addition, it takes a lot of time to weld the pipe ends of the metal pipe having an uneven outer peripheral surface, and the working efficiency is low.

  The connection of metal pipes is disclosed in, for example, Japanese Patent Application Laid-Open No. 2014-181733 (Patent Document 1) and Japanese Patent Application Laid-Open No. 2011-111769 (Patent Document 2).

  In Patent Document 1, the tube end portion of the inner tube is reduced in diameter, and the reduced tube end portion of the inner tube is inserted into the tube end portion of the outer tube. After insertion, a rolling process is performed from the surface of the outer tube, and the inner tube and the outer tube are crimped. Thereby, it is described in Patent Document 1 that the construction time and construction cost when connecting the metal pipes can be reduced.

  In Patent Document 2, the diameter of the tube end of the metal tube is reduced, and a tapered portion is provided between the tube end and the main body. This tube end is inserted into another metal tube. The end of the other metal tube is in contact with the tapered portion. Accordingly, Patent Document 2 describes that when a compressive load is applied to the metal tube, the compressive load is received in the entire taper portion, so that an excessive load is hardly applied to the fixing bolts and the like.

JP 2014-181733 A JP 2011-111769 A

  However, in Patent Document 1 and Patent Document 2, the cross-sectional shape of the metal tube is a circle. For this reason, it is difficult to employ the metal tube connection methods of Patent Document 1 and Patent Document 2 for connection of metal pipes having uneven outer peripheral surfaces.

  An object of the present invention is to provide a method of manufacturing a metal pipe for groundwater drainage that can be easily connected and can drain groundwater, a die used for the method, and a metal pipe for groundwater drainage manufactured by them. is there.

  The manufacturing method of the metal pipe for groundwater drainage by this embodiment is provided with a preparatory process and a diameter reducing process. In the preparation step, a metal tube having an outer peripheral surface and an inner peripheral surface is prepared. The outer peripheral surface includes a plurality of convex portions disposed around the central axis and a plurality of concave portions disposed between the plurality of convex portions. The plurality of convex portions and the plurality of concave portions extend in the central axis direction. In the diameter reducing process, the plurality of recesses are reduced at one end of the metal tube. In the diameter reduction processing step, the outer peripheral surfaces of the plurality of convex portions after the reduction are positioned inside the inner peripheral surfaces of the plurality of convex portions before the reduction, and the plurality of concave portions after the reduction, as viewed in the central axis direction. The tube end portion of the metal tube is reduced in diameter so that the outer peripheral surface is located inside the inner peripheral surfaces of the plurality of recesses before the reduction.

  In the die according to the present embodiment, the diameter of the end of the metal tube is reduced. Here, the “tube end portion” does not mean a region of the end face of the metal tube, but means a region at a certain distance from the end face. The die includes a plurality of protrusions arranged around the die center axis. The protrusion includes a bearing portion and an approach portion. The bearing portion extends in the direction of the die center axis. The approach portion is connected to the bearing portion, and has a tapered shape in which the distance from the die central axis increases in the opposite direction to the bearing portion.

  The metal pipe for groundwater drainage of this embodiment is manufactured by said manufacturing method and die | dye. The metal tube includes a plurality of convex portions disposed around the central axis and a plurality of concave portions disposed between the plurality of convex portions. The plurality of convex portions and the plurality of concave portions have an outer peripheral surface and an inner peripheral surface extending in the central axis direction. The metal tube includes a main body portion, one tube end portion, and a tapered portion. The main body has a constant cross-sectional shape along the central axis. One tube end has a constant cross-sectional shape along the central axis. The meaning of the “constant” does not include a difference in shape due to a dimensional error that occurs due to the influence of processing accuracy in the manufacturing process. The taper portion has a cross-sectional shape that changes along the central axis, and connects the main body portion and one pipe end portion. When viewed from the central axis direction, the outer peripheral surface of the convex portion at the end of the tube is located inside the inner peripheral surface of the convex portion of the main body portion. When viewed from the central axis direction, the outer peripheral surface of the concave portion at the end of the tube is located inside the inner peripheral surface of the concave portion of the main body portion.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the metal pipe for groundwater drainage which can be connected easily and can drain groundwater, the die used for it, and the metal pipe for groundwater drainage manufactured by them can be provided.

FIG. 1 is a perspective view of a metal pipe for groundwater drainage according to the present embodiment. FIG. 2 is a schematic view showing connected metal tubes. 3 is a cross-sectional view taken along line III-III in FIG. FIG. 4 is a schematic diagram of a landslide countermeasure for explaining a general groundwater drainer. FIG. 5 is a perspective view of a metal tube prepared in the preparation process. FIG. 6 is a cross-sectional view showing a diameter reducing process as seen from the side surface of the die. FIG. 7 is a cross-sectional view showing a diameter reducing process as seen from the front of the die. FIG. 8 is a cross-sectional view of the protruding portion of the die as viewed from the side surface of the die.

  The manufacturing method of the metal pipe for groundwater drainage by this embodiment is provided with a preparatory process and a diameter reducing process. In the preparation step, a metal tube having an outer peripheral surface and an inner peripheral surface is prepared. The outer peripheral surface includes a plurality of convex portions disposed around the central axis and a plurality of concave portions disposed between the plurality of convex portions. The plurality of convex portions and the plurality of concave portions extend in the central axis direction. In the diameter reducing process, the plurality of recesses are reduced at one end of the metal tube. In the diameter reduction processing step, the outer peripheral surfaces of the plurality of convex portions after the reduction are positioned inside the inner peripheral surfaces of the plurality of convex portions before the reduction, and the plurality of concave portions after the reduction, as viewed in the central axis direction. The tube end portion of the metal tube is reduced in diameter so that the outer peripheral surface is located inside the inner peripheral surfaces of the plurality of recesses before the reduction.

  The pipe end of the metal pipe for groundwater drainage according to the present embodiment is reduced in diameter. Therefore, the pipe end portion subjected to the diameter reduction processing can be inserted into the pipe end portion not subjected to the diameter reduction processing of another metal pipe for groundwater drainage work. Thereby, metal pipes can be connected easily. Moreover, in the cross section seen from the central axis direction of the metal tube of the connecting portion, the outer peripheral surface of the concave portion of the pipe end portion subjected to diameter reduction processing and the inner peripheral surface of the concave portion of the pipe end portion (main body portion) not subjected to diameter reduction processing A gap is provided between the two. When this metal pipe is buried in the ground, groundwater flows along the outer peripheral surface of the recess of the main body. Since the metal pipe is installed at an angle, groundwater flows from the main body toward the pipe end. The groundwater that has reached the end of the pipe is divided into one that flows along the outer peripheral surface of the concave portion of the connected metal pipe and one that enters the other metal pipe through the gap. That is, the groundwater is transported using not only the outer peripheral surface of the metal pipe but also the inside of a plurality of connected metal pipes. Therefore, groundwater can be stored and transported without using a hole-holding tube.

  The manufacturing method may further include a connecting step. In the connecting step, the pipe end portion subjected to diameter reduction processing is inserted into the pipe end portion of another metal pipe not subjected to diameter reduction processing, and a plurality of metal tubes are connected to each other.

  In the die according to the present embodiment, the diameter of the end of the metal tube is reduced. The die includes a plurality of protrusions arranged around the die center axis. The protrusion includes a bearing portion and an approach portion. The bearing portion extends in the direction of the die center axis. The approach portion is connected to the bearing portion, and has a tapered shape in which the distance from the die central axis increases in the opposite direction to the bearing portion.

  The die of the present embodiment has a plurality of protrusions. The metal tube is pushed into the die. The plurality of protrusions reduce the recesses of the metal tube having an uneven outer peripheral surface. Thereby, the diameter reduction process of the pipe end part of the metal pipe which has an uneven | corrugated outer peripheral surface is possible.

  When said die is used for said manufacturing method, it is preferable that several protrusion part is arrange | positioned corresponding to the position of several recessed part of a metal tube.

  The metal pipe for groundwater drainage of this embodiment is manufactured by said manufacturing method and die | dye. The metal tube includes a plurality of convex portions disposed around the central axis and a plurality of concave portions disposed between the plurality of convex portions. The plurality of convex portions and the plurality of concave portions have an outer peripheral surface and an inner peripheral surface extending in the central axis direction. The metal tube includes a main body portion, one tube end portion, and a tapered portion. The main body has a constant cross-sectional shape along the central axis. One tube end has a constant cross-sectional shape along the central axis. The taper portion has a cross-sectional shape that changes along the central axis, and connects the main body portion and one pipe end portion. When viewed from the central axis direction, the outer peripheral surface of the convex portion at the end of the tube is located inside the inner peripheral surface of the convex portion of the main body portion. When viewed from the central axis direction, the outer peripheral surface of the concave portion at the end of the tube is located inside the inner peripheral surface of the concave portion of the main body portion.

  In the metal tube, the length of the tube end portion in the central axis direction is preferably 0.5 times or more and 10 times or less the outer diameter of the metal tube (main body portion). In this case, the length of the connecting portion between the metal tubes does not become excessively long. Therefore, groundwater can be conveyed with a small number of metal pipes.

  Hereinafter, this embodiment will be described in detail. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and the description thereof is incorporated.

  First, the metal pipe for groundwater drainage of this embodiment is demonstrated. The material of the metal tube is, for example, steel, aluminum, copper, or an alloy thereof.

[Metal pipe for groundwater drainage]
FIG. 1 is a perspective view of a metal pipe for groundwater drainage according to the present embodiment. Referring to FIG. 1, a metal pipe 1 for groundwater drainage (hereinafter referred to as a metal pipe) includes a main body portion 6, one pipe end portion 7, and a taper portion 8. The cross-sectional shape of the main body 6 is constant along the central axis C. A cross section means a cross section in which the perpendicular is parallel to the direction of the central axis C of the metal tube. The cross-sectional shape of one tube end 7 is constant along the central axis C. That is, the cross-sectional shape of the main body 6 and one tube end 7 does not change along the central axis C. The tapered portion 8 is disposed between the main body portion 6 and the tube end portion 7. The taper part 8 connects the main body part 6 and the pipe end part 7. The cross-sectional shape of the taper portion 8 changes along the central axis C. More specifically, in the cross section of the tapered portion 8, the outer peripheral surface 4 of the tapered portion 8 approaches the central axis C as it approaches one pipe end portion 7. That is, one tube end portion of the metal tube 1 is reduced in diameter.

  The metal tube 1 includes a plurality of convex portions 2 and a plurality of concave portions 3. Hereinafter, the convex part 2 arrange | positioned on the outer peripheral surface 4 of the main-body part 6 is called "the convex part of a main-body part", and the code | symbol is set to "10." The concave portion 3 disposed on the outer peripheral surface 4 of the main body 6 is referred to as “a concave portion of the main body”, and the reference numeral is “13”. The convex part 2 arrange | positioned at the outer peripheral surface 4 of the pipe end part 7 is called "the convex part of a pipe end part", and the code | symbol is set to "11." The concave portion 3 arranged on the outer peripheral surface 4 of the pipe end portion 7 is referred to as a “concave portion of the pipe end portion”, and its symbol is “14”. The convex part 2 arrange | positioned on the outer peripheral surface 4 of the taper part 8 is called "the convex part of a taper part", and the code | symbol is set to "12." The concave portion 3 disposed on the outer peripheral surface 4 of the tapered portion 8 is referred to as a “concave portion of the tapered portion”, and the symbol thereof is “15”. When simply indicated as “convex part 2”, the convex part 2 means a general term for the convex part 10 of the main body part 6, the convex part 11 of the pipe end part 7, and the convex part 12 of the taper part 8. In the case of “recess 3”, the recess 3 is a general term for the recess 13 of the main body 6, the recess 14 of the tube end 7, and the recess 15 of the taper 8.

  The plurality of convex portions 2 are arranged around the central axis C. The plurality of concave portions 3 are disposed between the plurality of convex portions 2. The metal tube 1 has an outer peripheral surface 4 and an inner peripheral surface 5. On the outer peripheral surface 4, the plurality of convex portions 2 and the plurality of concave portions 3 extend in the direction of the central axis C. That is, the metal tube 1 has an uneven outer peripheral surface.

  As seen from the central axis C direction, the plurality of convex portions 2 protrude outside the metal tube 1 from the plurality of concave portions 3. The maximum radial distance between the plurality of convex portions 2 and the central axis C is longer than the maximum radial distance between the plurality of concave portions 3 and the central axis C. The plurality of convex portions 2 and the plurality of concave portions 3 are curved in an arc shape.

  Since the diameter of the tube end portion 7 is reduced, the cross-sectional shape of the main body portion 6, the cross-sectional shape of the tube end portion 7, and the cross-sectional shape of the tapered portion 8 are different. However, on the outer peripheral surface 4 of the metal tube 1, the convex portion 2 extends continuously from the main body portion 6 to the tube end portion 7. The same applies to the recess 3.

  The convex portion 2 and the concave portion 3 are preferably arranged at equal intervals around the central axis C. Moreover, it is preferable that the shape of the some convex part 2 is respectively the same. In this case, the diameter reduction process of a metal pipe becomes easy. However, the shape of the plurality of convex portions 2 may be different. The same applies to the plurality of recesses 3.

  Then, the situation when the metal pipes 1 mentioned above are connected is demonstrated. According to the metal pipe 1 described above, the metal pipes 1 can be easily connected to each other, and groundwater can be drained without making a hole in the metal pipe.

[Connectivity]
FIG. 2 is a schematic view showing connected metal tubes. Referring to FIG. 2, as described above, one pipe end portion 7 of the metal pipe 1 is reduced in diameter. The other tube end portion of the metal tube 1 is not reduced in diameter. The reduced tube end portion 7 of the metal tube 1 is inserted into the non-reduced tube end portion (main body portion 6) of the other metal tube 1.

  3 is a cross-sectional view taken along line III-III in FIG. Referring to FIG. 3, when the metal tubes 1 are connected to each other, the position of the convex portion 11 of the tube end portion 7 corresponds to the convex portion 10 of the main body portion 6 of another metal tube. That is, the convex part 11 of the pipe end part 7 is inserted along the convex part 10 of the main body part 6 of another metal pipe. Therefore, the outer peripheral surface 4 of the convex portion 11 of the tube end portion 7 is positioned on the inner side of the inner peripheral surface 5 of the convex portion 10 of the main body portion 6. Here, the inside means a direction approaching the central axis C of the metal tube 1. Therefore, the convex part 11 of the pipe end part 7 is inserted without interfering with the convex part 10 of the main body part 6 of another metal pipe.

  Similarly, the outer peripheral surface 4 of the recessed part 14 of the pipe | tube end part 7 is located inside the inner peripheral surface 5 of the recessed part 13 of the main-body part 6 of another metal tube. Therefore, the recess 14 of the tube end 7 is inserted without interfering with the recess 13 of the main body 6 of another metal tube. Thereby, metal pipes 1 are connected. Therefore, it is not necessary to connect the metal pipes 1 by welding or the like.

[Drainage]
FIG. 4 is a schematic diagram of a landslide countermeasure for explaining a general groundwater drainer. Referring to FIG. 4, the landslide is a phenomenon in which a landslide lump 202, which is a ground above the slip surface 201, moves downward along a slip surface 201 generated in the underground 200. As measures to prevent this landslide, there are a deterrent (301, 302, 306) and a depressor (300, 303, 304, 305).

  The deterrent is a measure to physically stop the landslide by the resistance of the structure. The anchor work 301, the earth retaining work 302, and the pile driving work 306 in FIG. 4 correspond to this. On the other hand, suppression work is a measure to suppress the occurrence of landslides by changing natural conditions such as groundwater conditions in the mass. The horizontal hole boring drainage 300, the water collecting well 303, the water collecting boring 304, and the draining boring 305 in FIG. 4 correspond to this. The groundwater draining work is a kind of restraining work, and includes a horizontal hole boring drainage 300, a water collection boring 304, and a draining boring 305. As described above, metal pipes for storing and transporting groundwater to the outside are used for these groundwater drainers.

  However, a hole retaining pipe has been used for groundwater drainage. Production of the hole-holding tube requires a hole work on the surface of the metal tube, and the productivity is low. The metal tube of this embodiment replaces a hole-holding tube. That is, it is possible to drain the groundwater without performing a drilling operation.

  With reference to FIG. 3, the outer peripheral surface 4 of the recessed part 14 of the pipe | tube edge part 7 is located inside the inner peripheral surface 5 of the recessed part 13 of the main-body part 6 of another metal tube. Therefore, the clearance gap 9 is provided between the outer peripheral surface 4 of the recessed part 14 of the pipe end part 7, and the inner peripheral surface 5 of the recessed part 13 of the main-body part 6 of another metal tube. Through this gap 9, groundwater is transported to the inside of another connected metal pipe.

  Referring to FIG. 2, outer peripheral surface 4 of metal pipe 1 installed in the ground is in contact with groundwater 40. The outer peripheral surface 4 includes a recess 3 (see FIG. 1). The metal pipe 1 is installed with the pipe end 7 facing downward at an inclination of an elevation angle of 5 to 10 degrees. Therefore, the groundwater 40 in contact with the outer peripheral surface 4 flows toward the pipe end portion 7 along the recess 3. The groundwater 40 that has reached the pipe end 7 passes through the outer peripheral surface 4 as it is (see reference numeral 40A in FIG. 2) and the gap 9 (see FIG. 3) to the inside 41 of another metal pipe 1. It divides into what enters (refer the code | symbol 40B in FIG. 2). That is, the groundwater is transported using not only the outer peripheral surface 4 of the metal tube 1 but also the insides 41 of the plurality of connected metal tubes 1.

  Although not shown, the tube end portion 7 of the other metal tube 1 is similarly reduced in diameter and connected to the tube end portion (main body portion 6) of another metal tube 1. Therefore, the groundwater 40 once entering the inside 41 of the metal pipe 1 does not leak to the outside of the metal pipe 1.

  Thus, according to the metal pipe 1 of this embodiment, groundwater can be drained without using a hole-holding pipe. Therefore, it is not necessary to make a hole in the metal tube.

  In the above description, it is assumed that metal tubes 1 having the same shape are connected to each other. Therefore, when the shapes of the tube end portion 7 and the main body portion 6 are projected in the direction of the central axis C in the metal tube 1 alone, it matches the cross-sectional shape of the connecting portion shown in FIG.

  With reference to FIG. 1, the length of the tube end portion 7 in the direction of the central axis C is preferably 0.5 times or more and 10 times or less the outer diameter of the metal tube 1 (main body portion 6). In this case, the length of the connecting portion between the metal tubes does not become excessively long. Therefore, groundwater can be conveyed with a small number of metal pipes.

  Next, the manufacturing method of the metal pipe 1 mentioned above is demonstrated.

[Production method]
The manufacturing method of this embodiment includes a preparation process and a diameter reducing process. In the preparation step, a metal tube having an uneven outer peripheral surface and a constant cross-sectional shape is prepared. In the diameter reducing process, the pipe end portion of the prepared metal pipe is diameter reduced. Thereby, the metal pipe 1 mentioned above is obtained. Hereinafter, each process is explained in full detail.

[Preparation process]
FIG. 5 is a perspective view of a metal tube prepared in the preparation process. Referring to FIG. 5, in the preparation step, a metal tube 30 (hereinafter referred to as a pre-processing metal tube) having an uneven outer peripheral surface and having a constant cross-sectional shape along the central axis C is prepared. The cross-sectional shape of the metal tube 30 before processing is the same as the cross-sectional shape of the main body portion 6 of the metal tube 1 in which the diameter of the tube end portion 7 is reduced (see FIG. 3). Therefore, detailed description of the cross-sectional shape of the pre-processing metal tube 30 is omitted.

  The unprocessed metal tube 30 is manufactured by processing a circular element tube. Examples of the processing method include drawing, extrusion, and drawing with a roll.

[Diametering process]
FIG. 6 is a cross-sectional view showing a diameter reducing process as seen from the side surface of the die. FIG. 7 is a cross-sectional view showing a diameter reducing process as seen from the front of the die. The broken line in FIG. 7 shows the cross-sectional shape of the inner peripheral surface of the metal tube 30 before processing. With reference to FIG.6 and FIG.7, in the diameter reduction process, the several recessed part 31 of the metal tube 30 before a process is rolled down by the die | dye 20 mentioned later in one pipe | tube edge part of the metal tube 30 before a process.

  Specifically, the center axis C of the unprocessed metal tube 30 is aligned with the die center axis C 1 of the die 20. The unprocessed metal tube 30 is arranged so that the recess 31 of the unprocessed metal tube 30 corresponds to the protruding portion 21 of the die 20. One tube end portion 32 of the pre-processing metal tube 30 is pushed into the die 20. The unprocessed metal tube 30 is pushed in, for example, by gripping a tube end portion not subjected to diameter reduction processing with a chuck. When the pre-processing metal tube 30 is pushed into the die 20, the protruding portion 21 presses down the concave portion 31 of the tube end portion 32. Thereby, the outer peripheral surface of the some recessed part 31 after reduction comes to be located inside the inner peripheral surface of the some recessed part 31 before reduction. That is, the outer peripheral surfaces 4 of the plurality of recesses 3 in the tube end portion 7 of the metal tube 1 are positioned inside the inner peripheral surfaces 5 of the plurality of recesses 3 in the main body portion 6 of the metal tube 1 (FIG. 3). reference). As a result, gaps 9 are formed between the outer peripheral surfaces 4 of the plurality of recesses 14 in the tube end portion 7 and the inner peripheral surfaces 5 of the plurality of recesses 13 in the main body 6 (see FIG. 3). Is manufactured.

  Referring to FIG. 7, when the concave portion 31 of the pre-processing metal tube 30 is pressed down by the die 20, the concave portion 31 is deformed in a direction approaching the central axis C. Accordingly, the convex portion 33 adjacent to the concave portion 31 is also deformed in a direction approaching the central axis C. As a result, when the main body portion and the tube end portion are projected in the direction of the central axis C, the outer peripheral surfaces of the plurality of convex portions after the reduction are positioned inside the inner peripheral surfaces of the plurality of convex portions before the reduction. . That is, the outer peripheral surfaces 4 of the plurality of convex portions 2 of the tube end portion 7 of the metal tube 1 are positioned inside the inner peripheral surfaces 5 of the plurality of convex portions 2 of the main body portion 6 of the metal tube 1. As a result, gaps 9 are formed between the outer peripheral surfaces 4 of the plurality of convex portions 11 of the pipe end portion 7 and the inner peripheral surfaces 5 of the plurality of convex portions 10 of the main body portion 6 (see FIG. 3), and the metal described above Tube 1 is manufactured.

[Connection process]
The manufacturing method of this embodiment may include a connecting step. In the connecting step, the pipe end portion 7 subjected to the diameter reduction processing is inserted into the pipe end portion of the other metal pipe not subjected to the diameter reduction processing. Thereby, several metal pipes 1 are connected.

  Finally, the dies used in the manufacturing method described above will be described.

[dice]
With reference to FIG. 7, the die 20 reduces the diameter of the tube end portion of the pre-processing metal tube 30. The die 20 includes a plurality of protrusions 21 arranged around the die center axis C1.

  FIG. 8 is a cross-sectional view of the protruding portion of the die as viewed from the side surface of the die. In FIG. 8, one of the plurality of protrusions 21 is depicted. Referring to FIG. 8, the protruding portion 21 includes a bearing portion 22 and an approach portion 23.

  The bearing portion 22 extends in the direction of the die center axis C1. The bearing portion 22 includes a pressure surface 24. The pressure lower surface 24 of the bearing portion 22 forms the concave portion 14 of the tube end portion 7 of the metal tube 1.

  The approach portion 23 is connected to the bearing portion 22. The approach portion 23 is disposed in front of the bearing portion 22 in the pushing direction of the metal tube 1 (the arrow direction in FIG. 8). The approach portion 23 has a tapered shape. The approach portion 23 includes a pressure surface 25. The distance between the pressing surface 25 of the approach portion 23 and the die center axis C1 increases as it goes in the direction opposite to the bearing portion 22 (the direction opposite to the pushing direction). The pressing surface 25 of the approach portion 23 forms the concave portion 15 of the tapered portion 8 of the metal tube 1.

  In short, the concave portion 31 of the tube end portion 32 of the pre-processing metal tube 30 is pressed down by the protruding portion 21 of the die 20 (see FIG. 5). Thereby, the pipe end part 32 of the metal pipe 30 before a process is reduced in diameter, and the metal pipe 1 is manufactured. Therefore, the number of protrusions 21 of the die 20 is equal to the number of recesses 31 of the pre-processing metal tube 30. In addition, the plurality of protrusions 21 of the die 20 are preferably arranged corresponding to the positions of the plurality of recesses 31 of the pre-processing metal tube 30.

  In the above-described embodiment, the case where the metal tube 1 has the six convex portions 2 and the six concave portions 3 has been described. However, the number of convex portions and concave portions of the metal tube is not limited to six. The number of convex portions and concave portions of the metal tube may be three or more.

  In the above-described embodiment, the case where the diameter of the pre-processing metal tube is reduced in one diameter reduction process has been described. However, the diameter reducing process is not limited to this case. The diameter reducing process may be performed a plurality of times. In this case, since the amount of reduction of the pre-processing metal tube is reduced in each diameter-reducing processing step, even a pre-processing metal tube made of a material with high yield strength can be reduced.

  The embodiment of the present invention has been described above. However, the above-described embodiment is merely an example for carrying out the present invention. Therefore, the present invention is not limited to the above-described embodiment, and can be implemented by appropriately changing the above-described embodiment without departing from the spirit thereof.

1: Metal tube 2: Convex part 3: Concave part 4: Outer peripheral surface 5: Inner peripheral surface 6: Main body part 7: Pipe end part 8: Taper part 9: Gap 10: Convex part of main part 11: Convex part of pipe end part Part 12: Convex part of taper part 13: Concave part of main body part 14: Concave part of pipe end part 15: Concave part of taper part 20: Die 21: Protruding part 22: Bearing part 23: Approach part 24: Pressure lower surface (bearing part)
25: Pressed surface (approach part)
40: Groundwater C: Center axis of metal pipe C1: Center axis of dice

Claims (6)

A plurality of convex portions disposed around a central axis and a plurality of concave portions disposed between the plurality of convex portions, wherein the plurality of convex portions and the plurality of concave portions extend in the direction of the central axis and an inner surface Preparing a metal tube having a peripheral surface;
By rolling down the plurality of recesses at one tube end of the metal tube, the outer peripheral surfaces of the plurality of projections after the rolling down of the plurality of projections before the rolling down are viewed in the central axis direction. The metal tube is located on the inner side of the inner peripheral surface, and the outer peripheral surfaces of the plurality of concave portions after the reduction are positioned on the inner side of the inner peripheral surfaces of the plurality of concave portions before the reduction. A method for producing a metal pipe for groundwater drainage, comprising the step of reducing the diameter of the pipe end. The method for producing a metal pipe for groundwater drainage according to claim 1, further comprising:
Inserting the reduced-diametered pipe end into the non-reduced pipe end of the other metal pipe and connecting the plurality of metal pipes together for groundwater drainage work. Metal tube manufacturing method. A die for reducing the diameter of a pipe end of a metal pipe,
A bearing portion extending in the direction of the die center axis, and an approach portion having a taper shape connected to the bearing portion and increasing in distance from the die center axis in the direction opposite to the bearing portion, and the die center axis A die comprising a plurality of protrusions arranged around. A die according to claim 3,
The metal tube includes a plurality of convex portions arranged around a central axis and a plurality of concave portions arranged between the plurality of convex portions, and the plurality of convex portions and the plurality of concave portions are arranged in the central axis direction. An outer peripheral surface extending,
The plurality of protrusions are dies arranged in correspondence with the positions of the plurality of recesses of the metal tube. A plurality of convex portions disposed around a central axis and a plurality of concave portions disposed between the plurality of convex portions, wherein the plurality of convex portions and the plurality of concave portions extend in the direction of the central axis and an inner surface A metal pipe for groundwater drainage having a peripheral surface,
A body portion having a constant cross-sectional shape along the central axis;
One tube end whose cross-sectional shape is constant along the central axis;
A cross-sectional shape changes along the central axis, and includes a tapered portion that connects the main body portion and one pipe end portion;
In the central axis direction view, the outer peripheral surface of the convex portion of the tube end portion is located inside the inner peripheral surface of the convex portion of the main body portion,
The metal pipe for groundwater drainage work in which the outer peripheral surface of the concave portion at the end of the pipe is located on the inner side of the inner peripheral surface of the concave portion of the main body when viewed in the central axis direction. A metal pipe for groundwater drainage according to claim 5,
The length of the said pipe end part in the said central-axis direction is a metal pipe for groundwater drainage works which is 0.5 to 10 times the outer diameter of the said metal pipe.

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