Crushed stone pile forming attachment and crushed stone pile forming device equipped with the same

Abstract

To prevent a driving device and a cylindrical portion from separating when a connection portion between an output shaft of a driving device and a shaft breaks inside a crushed stone pile forming attachment.SOLUTION: A crushed stone pile forming attachment 10 comprises a cylindrical portion 12, a shaft 22, and a hollow joint rod 26. The cylindrical portion 12 has a crushed stone input hole 15 formed on its side surface. The shaft 22 is rotatably disposed within the cylindrical portion 12 and rotates by a driving force from a driving device 11. The joint rod 26 has a first end 26a side connected to an output shaft 27 of the driving device 11, and a second end 26b side connected to the shaft 22. The attachment 10 further comprises a core material 71. The core material 71 is disposed within the joint rod 26, its upper end is engaged with a first end side of the joint rod, and its lower end is engaged with a second end side of the joint rod.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The technology disclosed in this specification relates to an attachment for forming a crushed stone pile and a crushed stone pile forming device equipped with the attachment. [Background technology]

[0002] A method for forming crushed stone piles underground is used for ground improvement, such as countermeasures against liquefaction. One method for forming crushed stone piles underground involves using an attachment that is inserted into the ground to form a space. This type of attachment includes a cylindrical portion with a crushed stone insertion hole formed on its side and a shaft rotatably disposed within the cylindrical portion. The upper end of the shaft is connected to the output shaft of a drive unit by a hollow joint rod. Therefore, when the drive unit is driven, its rotational force is transmitted to the shaft via the joint rod, causing the shaft to rotate. The shaft is then rotated in the forward direction to insert the attachment and form a space underground. Once the attachment is inserted into the ground, crushed stone is introduced into the internal space of the cylindrical portion, and the attachment is removed by rotating the shaft in the reverse direction to form the crushed stone pile. For example, Patent Document 1 discloses an example of an attachment for forming crushed stone piles. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-248885 Summary of the Invention [Problem to be solved by the invention]

[0004] This type of attachment is equipped with a one-way clutch mechanism at the upper end of the cylindrical portion. The one-way clutch mechanism rotates the cylindrical portion following the rotation of the shaft in the forward direction, and stops the cylindrical portion without following the rotation of the shaft when the shaft is rotated in the reverse direction. A bearing portion is provided immediately above the one-way clutch mechanism, and the joint rod is rotatably supported by the bearing portion at a position midway between the upper and lower ends. During underground excavation or the formation of a crushed stone pillar, large forces act on the shaft, and the forces acting on the shaft are transmitted to the joint rod. Because the joint rod is restricted in its movement perpendicular to the axis by the bearing portion, stress is likely to concentrate at the point where the joint rod is supported by the bearing portion, potentially causing the joint rod to break near that point. If the joint rod were to break, the connected drive unit and cylindrical portion would separate, potentially causing the cylindrical portion to fall off the drive unit.

[0005] This specification discloses a technology that can prevent the cylindrical portion from falling off from the drive device even if the connection portion between the output shaft of the drive device and the shaft inside the crushed stone pile forming attachment breaks. [Means for solving the problem]

[0006] The attachment disclosed in this specification is an attachment for forming a crushed stone pile that is attached to a crushed stone pile forming device that forms a crushed stone pile in a space formed underground, is inserted into the ground to form a space, and forms a crushed stone pile in the space by rising from the ground. This attachment includes a cylindrical portion with a crushed stone injection hole formed on its side, a shaft that is rotatably arranged within the cylindrical portion and rotates by driving force from a drive device, a hollow joint rod having a first end and a second end, the first end connected to an output shaft of the drive device and the second end connected to the shaft, and a core member that is arranged within the joint rod and has an upper end engaged with the first end side of the joint rod and a lower end engaged with the second end side of the joint rod.

[0007] In the above attachment, even if the joint rod connecting the output shaft of the drive unit and the shaft were to break, the core material housed inside it would lock onto the first end and the second end, respectively, making it easier to maintain the connection between the output shaft and the shaft, and preventing the cylindrical portion from falling off the drive unit.

[0008] This specification also discloses a crushed stone pile forming device equipped with the above-mentioned attachment. That is, the crushed stone pile forming device disclosed in this specification includes the above-mentioned attachment and a drive unit that generates rotational driving forces in forward and reverse directions to drive the attachment. With this crushed stone pile forming device, even if the connecting portion (joint shaft) between the output shaft of the drive unit and the shaft inside the attachment breaks, it is possible to prevent the cylindrical portion from falling off the drive unit. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a diagram showing a schematic configuration of a crushed stone pile forming device according to a first embodiment. [Figure 2] A view of only the attachment shown in Figure 1 from a different angle. [Figure 3] FIG. 4 is a vertical cross-sectional view showing a connecting portion between the drive device and the cylindrical portion. [Figure 4] 1(a) is a longitudinal cross-sectional view showing a joint rod, and FIG. 1(b) is a side view of a core material that constitutes the joint rod. [Figure 5] FIG. 10 is a partial vertical cross-sectional view showing a main part of a joint rod according to another embodiment. [Figure 6] FIG. 10 is a partial vertical cross-sectional view showing a main part of a joint rod according to another embodiment. [Figure 7] FIG. 10 is a side view of the crushed stone pile forming device when transporting the soil improvement machine with the attachment attached. DETAILED DESCRIPTION OF THE INVENTION

[0010] (Feature 1) In the attachment disclosed in this specification, the joint rod may include a cylindrical main body having a first opening on the first end side and a second opening on the second end side, a first end member joined to the first opening of the cylindrical main body, and a second end member joined to the second opening of the cylindrical main body. With this configuration, the upper end of the core material housed inside the cylindrical main body can be joined to the first end member on the first opening side, and the lower end can be joined to the second end member on the second opening side. This allows the first end member and the second end member to be maintained in a connected state by the core material.

[0011] (Feature 2) In the attachment disclosed in this specification, the upper end of the core may be inserted into a first central hole of the first end member and welded to the first end member. With this configuration, the upper end of the core can be firmly fixed to the first end member.

[0012] (Feature 3) In the attachment disclosed in this specification, the lower end of the core member may be fitted into a second central hole of the second end member. The second end member side of the joint rod is disposed inside the cylindrical portion. With this configuration, the lower end of the core member is fixed to the second end member without welding. Furthermore, even if the lower end of the core member is located in a location where welding is difficult, the lower end of the core member can be fixed to the second end member relatively easily.

[0013] (Feature 4) In the attachment disclosed in this specification, a support recess may be formed at the upper end opening of a first center hole in the first end member, and a first enlarged diameter portion having a diameter larger than the first center hole may be formed at the upper end of the core member, with the first enlarged diameter portion being supported by the support recess. With this configuration, even if a force is applied to the core member toward the second end member, the first enlarged diameter portion does not pass through the first center hole but is supported by abutting against the support recess. Therefore, even if the upper end of the core member is not fixed to the first end member by welding or the like, the upper end of the core member is held without slipping out of the first end member.

[0014] (Feature 5) In the attachment disclosed in this specification, an expanded diameter space may be formed at the lower end opening of the second center hole of the second end member, and a second expanded diameter section having a diameter larger than that of the second center hole may be formed at the lower end of the core member, with the second expanded diameter section being disposed within the expanded diameter space. With this configuration, even if a force is applied to the core member toward the first end member, the second expanded diameter section will not pass through the second center hole but will remain and be supported within the expanded diameter space. Therefore, even if the lower end of the core member is not fixed to the second end member by welding or the like, the lower end of the core member will be held without slipping out of the second end member.

[0015] (Feature 6) The attachment disclosed in this specification may further include a bearing portion provided at one end of the cylindrical portion, and the bearing portion may rotatably support the joint rod at a position intermediate between the first end and the second end. [Example]

[0016] Hereinafter, a crushed stone pile forming device 100 according to this embodiment will be described. As shown in Fig. 1, the crushed stone pile forming device 100 includes a soil improvement machine 40 as a construction machine, and an attachment 10 attached to the soil improvement machine 40. As shown in Fig. 1, the soil improvement machine 40 includes a soil improvement machine main body structure 1, a cabin 7 as a driver's seat, crawlers 6 which are endless tracks that can move on uneven ground with low ground pressure, and outriggers 5 that suppress shaking of the soil improvement machine 40 during construction.

[0017] The ground improvement machine 40 further includes, as components for operating the attachment 10, a drive unit 11 that supplies rotational driving force to the attachment 10 via an output shaft 27, a leader 4 having a lifting guide rail 9, a lifting platform 17 that raises and lowers the drive unit 11 and attachment 10 along the lifting guide rail 9, a leader mounting base 2 for supporting the leader 4, a hydraulic cylinder 3 that controls the inclination of the leader 4, and an extension column 8 that is formed integrally with the leader 4 at the lower end of the leader 4.

[0018] As shown in Figures 1 and 2, the attachment 10 comprises a cylindrical portion 12 provided with fins 13, a shaft 22 (shown in Figure 3), a joint rod 26, a spiral portion 14, an enclosing frame 30 for preventing the cylindrical portion 12 from vibrating, a hanger stay 18 attached to the lifting platform 17, a top cover case 16, a crushed stone feeding device 32, a support plate 37 supporting the enclosing frame 30, a support arm 39 supporting the crushed stone feeding device 32, and a construction management device 41 for managing the construction status using the attachment 10.

[0019] The cylindrical portion 12 has a crushed stone injection hole 15 formed in the axial direction on its side surface. The crushed stone injection hole 15 extends in the axial direction of the cylindrical portion 12 and is closed by an opening / closing door 20 made of elastically deformable rubber or resin.

[0020] The crushed stone feeding device 32 includes a hopper section 33 and a chute section 34 disposed below the hopper section 33. The crushed stone feeding hole 15 is closed by an opening / closing door 20 when the attachment 10 is excavating the ground. This prevents soil and sand from entering the cylindrical section 12 through the crushed stone feeding hole 15. Furthermore, when crushed stone is to be fed into the cylindrical section 12, the opening / closing door 20 is opened. This allows the crushed stone fed into the crushed stone feeding device 32 to be fed into the cylindrical section 12 through the crushed stone feeding hole 15. Furthermore, because the crushed stone feeding hole 15 is provided as an elongated hole along the axial direction, the crushed stone can be fed into the cylindrical section 12 without changing the crushed stone feeding position even when the cylindrical section 12 is raised.

[0021] As shown in Figures 1 and 2, the helical portion 14 is located at the tip of the cylindrical portion 12 and is connected to the tip side of the shaft 22 (shown in Figure 3) so as to be rotatable together. An excavation blade is provided at the tip of the helical portion 14. The excavation blade is formed in a spiral shape with a diameter that increases toward the tip of the helical portion 14. Almost the entire excavation blade is disposed within the cylindrical portion 12, and only a portion of the tip of the excavation blade protrudes from the tip of the cylindrical portion 12. A helical fin 13 is provided on the outer periphery of the cylindrical portion 12. The fin 13 has a helical shape that rotates in the same direction as the helix of the helical portion 14 (i.e., the excavation blade). In other words, during excavation, the cylindrical portion 12 and the helical portion 14 rotate in the same direction. As a result, the excavated soil produced by the excavation of the helical portion 14 is transported to the ground surface by the fin 13.

[0022] As shown in Figure 3, shaft 22 is a member rotatably arranged along its central axis within cylindrical portion 12, and is made of a steel pipe with a fixed diameter (approximately 8 cm). Radial stays 24 are provided at multiple locations within cylindrical portion 12, and bearing pipes 23 are fixed via these radial stays 24. Shaft 22 is supported by being inserted into these bearing pipes 23.

[0023] The base end side of the shaft 22 is connected to a joint rod 26. The joint rod 26 is disposed with a portion thereof protruding from the upper end of the cylindrical portion 12, and is connected to an output shaft 27 of the drive unit 11. The joint rod 26 rotates in response to the rotational driving force of the output shaft 27, and transmits the rotational driving force to the helical portion 14 via the shaft 22, which is integrally connected to the joint rod 26. The detailed configuration of the joint rod 26 will be described later.

[0024] The top cover case 16 is attached to the rear end (base end) of the cylindrical portion 12 and is integrated with the cylindrical portion 12. The joint rod 26 penetrates the upper surface of the top cover case 16 and is rotatably supported by the top cover case 16. Therefore, even when the joint rod 26 (shaft 22) is rotationally driven, the cylindrical portion 12 does not rotate together with the joint rod 26 (shaft 22) and remains free to move.

[0025] The attachment 10 further includes a rotational drive force transmission unit and a reverse prevention unit within the top cover case 16. The rotational drive force transmission unit is a one-way clutch mechanism C1, which automatically rotates the helical portion 14 (joint rod 26 and shaft 22) and the cylindrical portion 12 as a unit when driving the helical portion 14 in the rotational direction during excavation. This allows the fins 13 of the cylindrical portion 12 to discharge the soil excavated by the helical portion 14 to the ground, as described above. On the other hand, when driving the helical portion 14 in the direction opposite to the rotational direction during excavation, the rotational drive force transmission unit rotates the helical portion 14 in the reverse direction to apply pressure to the crushed stone and also interrupts the transmission of power from the helical portion 14 (joint rod 26 and shaft 22) to the cylindrical portion 12, stopping the rotation of the cylindrical portion 12. When driving the helical part 14 in the direction opposite to the rotation direction during excavation, the anti-reverse part restricts the rotation of the cylindrical part 12 so that the stopped cylindrical part 12 does not rotate in either the excavation rotation direction or the reverse direction. Hereinafter, the direction in which the cylindrical part 12 and the helical part 14 rotate in the same direction, i.e., the rotation direction during excavation, will be referred to as the "forward direction," and the direction in which they rotate in the opposite direction to the rotation direction during excavation, i.e., the rotation direction in which pressure is applied to the crushed stone by the helical part 14, will be referred to as the "reverse direction." In addition, the forward direction of rotation will be described as right rotation (clockwise), and the reverse direction of rotation will be described as left rotation (counterclockwise).

[0026] The attachment 10 further includes a bearing 57 provided at one end of the cylindrical portion 12. This bearing 57 is specifically provided at the center of the upper end surface of the top cover case 16, and the joint rod 26 is inserted through its center hole.

[0027] 4(a) and 4(b), the cylindrical portion separation prevention mechanism in the attachment 10 of this embodiment will be described in detail. Since the cylindrical portion separation prevention mechanism is provided in the joint rod 26, the configuration of the joint rod 26 will be described first.

[0028] As shown in FIG. 4(a), the joint rod 26 of this embodiment is hollow and has a first end 26a and a second end 26b. The first end 26a is located at the upper side in FIG. 4(a) and is connected to the output shaft 27 of the drive unit 11. The second end 26b is located at the lower side in FIG. 4(a) and is connected to the upper end of the shaft 22. The joint rod 26 includes a cylindrical main body 61 and a first end member 62 and a second end member 63 attached to the cylindrical main body 61. The cylindrical main body 61 is a cylindrical steel pipe having a first opening 26c on the first end 26a side and a second opening 26d on the second end 26b side. The cylindrical main body 61 has a rod accommodating space 66 therein. The first end member 62 is a columnar member having a first center hole 64 and a first fitting portion 62c on the lower end side. The first fitting portion 62c is joined to the cylindrical main body 61 by being fitted into the first opening 26c of the cylindrical main body 61. The joint portion between the cylindrical main body 61 and the first end member 62 is fixed by welding. The second end member 63 is a cylindrical member having a second center hole 65 and an expanded diameter space 63b communicating therewith, and has a second fitting portion 63c on its upper end side. The second fitting portion 63c is joined to the cylindrical main body 61 by being fitted into the second opening 26d of the cylindrical main body 61. The joint portion between the cylindrical main body 61 and the second end member 63 is fixed by welding. The cylindrical main body 61, which is located midway between the first end 26a and the second end 26b of the joint rod 26, is rotatably supported by the bearing portion 57 on its outer circumferential surface side.

[0029] As shown in FIG. 4(b), a core member 71 is disposed inside the joint rod 26 of this embodiment to maintain the first end 26a and the second end 26b of the joint rod 26 in a connected state even if the joint rod 26 breaks. The core member 71 is a component constituting the main part of the mechanism that maintains the connected state of the cylindrical portions and is made of a metal rod with a circular cross section. Most of the core member 71 is located within the rod accommodating space 66 of the cylindrical main body 61. The upper end 71a of the core member 71 is inserted through the first center hole 64 of the first end member 62 and reaches the upper end opening 62a of the first center hole 64. In this state, the upper end 71a of the core member 71 is welded and fixed to the first end member 62. Meanwhile, the lower end 71b of the core member 71 is fitted into the second center hole 65 of the second end member 63 and is thereby fixed to the second end member 63. As a result, the upper end 71a of the core material 71 is welded to the first end member 62 on the first opening 26c side, and the lower end 71b is fitted into the second end member 63 on the second opening 26d side. This ensures that the first end member 62 and the second end member 63 remain connected to each other even if the joint rod 26 breaks.

[0030] Next, the operation of the crushed stone pile forming device 100 when the crushed stone pile forming device 100 forms a crushed stone pile will be described.

[0031] First, the attachment 10 is aligned. The alignment of the attachment 10 is performed by adjusting the position and direction of the soil improvement machine 40 by driving the crawler 6. After adjusting the position and direction of the soil improvement machine 40, the soil improvement machine 40 may be fixed to the ground by the outriggers 5. This makes it possible to suppress shaking and displacement of the soil improvement machine 40 during construction.

[0032] Next, the attachment 10 is inserted into the ground to excavate the ground. Specifically, after the soil improvement machine 40 is fixed to the ground, the attachment 10 is lowered while driving the drive unit 11. At this time, the drive unit 11 is driven to generate a rotational drive force in the forward direction. As described above, when the drive unit 11 generates a rotational drive force in the forward direction, the rotational drive force transmission unit rotates the spiral portion 14 and the cylindrical portion 12 in the forward direction. This allows the attachment 10 to be inserted into the ground and excavate. The soil and sand discharged by excavation in the ground is carried to the outer periphery of the cylindrical portion 12 and discharged to the surface by the fins 13. When the attachment 10 reaches a predetermined depth, the forward rotation of the drive unit 11 is stopped, and excavation ends.

[0033] Next, the attachment 10 is raised, and a crushed stone pile is formed in the ground. The crushed stone pile is formed in the following manner. First, with the opening / closing door 20 open, crushed stone is loaded into the crushed stone loading device 32. The crushed stone loaded into the crushed stone loading device 32 is then loaded into the cylindrical portion 12 through the crushed stone loading hole 15. Next, the drive device 11 is driven to generate a rotational driving force in the reverse direction. The spiral portion 14 then rotates in the reverse direction, and the crushed stone loaded into the cylindrical portion 12 is discharged out of the cylindrical portion 12 while being pressed by the spiral portion 14. This pushes the attachment 10 out of the ground, and a crushed stone pile is formed in the space formed by the cylindrical portion 12. As described above, when the drive device 11 generates a rotational driving force in the reverse direction, only the spiral portion 14 rotates in the reverse direction due to the rotational driving force transmission unit, and the cylindrical portion 12 does not rotate in either the forward or reverse direction. This prevents the position of the crushed stone injection hole 15 provided in the cylindrical portion 12 from changing in the circumferential direction, and allows crushed stone to be injected into the cylindrical portion 12 without adjusting the position of the crushed stone injection device 32. Then, when the attachment 10 is pushed out to the ground surface, the driving of the driving device 11 in the reverse direction is stopped, and the formation of the crushed stone pile is completed.

[0034] In this type of attachment 10, the joint rod 26 is rotatably supported at a position midway between the upper end 26a and the lower end 26b by the bearing 57. Therefore, a large stress tends to concentrate at the point of the joint rod 26 supported by the bearing 57, and there is a possibility that the joint rod 26 will break (fracture) near that point (for example, position P1 shown in FIG. 3).

[0035] Therefore, in the attachment 10 of this embodiment, a core material 71 is disposed within the hollow joint rod 26 that connects the output shaft 27 and the shaft 22. The core material 71 connects the first end 26a and the second end 26b of the joint rod 26 so that they remain connected to each other even if the joint rod 26 breaks. Therefore, in the attachment 10 described above, even if the joint rod 26 breaks midway, the upper end 71a of the core material 71 housed therein engages with the first end 26a, and the lower end 71b of the core material 71 engages with the second end 26b, so that the first end 26a and the second end 26b remain connected to each other (i.e., the connection between the output shaft 27 side and the shaft 22 side is maintained). This prevents the cylindrical portion 12 from unintentionally falling off the drive device 11. This prevents the cylindrical portion 12 from unintentionally separating from the drive device 11 and tipping over or rolling. Furthermore, when transporting the soil improvement machine 40, as shown in FIG. 7, it may be transported with the attachment 10 attached to the soil improvement machine 40. That is, the soil improvement machine 40 may be transported with the leader 4 horizontal, thereby horizontally positioning the attachment 10. In this case, if the core material 71 is not provided, if the joint rod 26 breaks, there is a possibility that the attachment 10 will fall off the drive unit 11 and onto the ground. However, in the soil improvement machine 40 of this embodiment, the core material 71 is disposed within the joint rod 26, and the core material 71 maintains the connection between the drive unit 11 and the attachment 10. This prevents the attachment 10 from unintentionally falling off when transporting the soil improvement machine 40.

[0036] In the joint rod 26 of this embodiment, the upper end 71a of the core material 71 is inserted into the first center hole 64 of the first end member 62 and is fixed by welding to the first end member 62. This allows the upper end 71a of the core material 71 to be firmly fixed to the first end member 62 (an example of locking).

[0037] Furthermore, in the joint rod 26 of this embodiment, the lower end 71b of the core material 71 is fitted (an example of locking) into the second center hole 65 of the second end member 63, and the second end member 63 side of the joint rod 26 is disposed inside the cylindrical portion 12. Therefore, the movement of the second end member 63 in the direction perpendicular to the axis is restricted by the core material 71, and as a result, the movement of the second end member 63 (and the shaft 22) in the direction perpendicular to the axis is restricted by the cylindrical portion 12. Therefore, even if the lower end 71b of the core material 71 is not welded to the second end member 63, it is possible to prevent the lower end 71b of the core material 71 from coming off the second center hole 65 of the second end member 63. Therefore, even if the lower end 71b of the core material 71 is located in a position where welding is difficult, it is possible to fix the lower end 71b of the core material 71 to the second end member 63 relatively easily.

[0038] In the joint rod 26 of this embodiment described above, the upper end 71a of the core material 71 is inserted through the first center hole 64 of the first end member 62 and welded to the upper end opening 62a of the first end member 62. However, this is not limited to this, and the upper end of the core material can be engaged with the first end member in various ways. For example, in a joint rod 26A of another embodiment shown in FIG. 5, a support recess 62b is formed in the upper end opening 62a of the first center hole 64 of the first end member 62. Furthermore, a first enlarged diameter portion 72 having a diameter larger than the first center hole 64 is formed in the upper end 71a of the core material 71. The first enlarged diameter portion 72 may be supported by the support recess 62b. When assembling the joint rod 26A, the lower end 71b of the core material 71 is inserted through the upper end opening 62a of the first center hole 64. With this configuration, even if a force is applied to the core material 71 in a direction that separates the first end member 62 and the upper end 71a of the core material 71 (i.e., a force that pulls the core material 71 downward in the figure), the first expanded diameter portion 72 does not pass through the first center hole 64 but abuts against the support recess 62b and is supported. Therefore, even if the upper end 71a of the core material 71 is not fixed to the first end member 62 by welding or the like, the upper end 71a of the core material 71 is held (locked) without slipping out of the first end member 62. Note that, although the first expanded diameter portion 72 is cylindrical in another embodiment shown in FIG. 5, the shape is not limited to this and may be, for example, rectangular, spherical, conical, or the like.

[0039] Furthermore, in the joint rod 26 of this embodiment, the lower end 71b of the core 71 is fitted into the second center hole 65 of the second end member 63. However, this is not limited to this, and the lower end of the core can be engaged with the second end member in various ways. For example, in a joint rod 26B of another embodiment shown in FIG. 6, an expanded diameter space 63b is formed in the lower end opening 63a of the second center hole 65 of the second end member 63. A second expanded diameter portion 73 having a diameter larger than that of the second center hole 65 is formed in the lower end 71b of the core 71. This second expanded diameter portion 73 may be disposed within the expanded diameter space 63b. When assembling the joint rod 26B, the upper end 71a of the core 71 is inserted through the lower end opening 63a of the second center hole 65. With this configuration, even if a force is applied to the core 71 in a direction that separates the second end member 63 and the lower end 71b of the core 71 (i.e., a force that pulls the core 71 upward in the figure), the second expanded diameter portion 73 does not pass through the second center hole 65, but remains and is supported within the expanded diameter space 63b. Therefore, even if the lower end 71b of the core 71 is not fixed to the second end member 63 by welding or the like, the lower end 71b of the core 71 is held (locked) without slipping out of the second end member 63. Note that, although the second expanded diameter portion 73 has a spherical shape in another embodiment shown in FIG. 6, the shape is not limited to this and may be, for example, a rectangular parallelepiped, a cylindrical, a conical, or the like.

[0040] Furthermore, in this embodiment, a metal rod is used as the core material 71, but this is not limiting. For example, in another embodiment shown in Figures 5 and 6, a metal wire may be used as the core material 71. That is, the configuration of Figure 5 may be adopted for the upper end of the core material 71, and the configuration of Figure 6 may be adopted for the lower end of the core material 71. With this configuration, or when a metal wire is used for the core material 71, the cylindrical portion 12 and the drive device 11 (output shaft 27) can be maintained in a connected state.

[0041] In addition, in this embodiment, compaction by reverse rotation of the screw of the attachment 10 is performed as a method of pouring crushed stone into a space formed underground to form a crushed stone pile, but the present invention is not limited to this example. The technology disclosed in this specification can also be used in crushed stone pile formation methods that do not rely on compaction by reverse rotation of the screw of the attachment 10.

[0042] In addition, although the present embodiment has been described as an attachment 10 of a type that discharges excavated earth and sand to the ground surface (a so-called earth discharge type), the present invention is not limited to such an example. The technology disclosed in this specification can also be employed in, for example, an attachment of a non-earth discharge type.

[0043] While specific examples of the technology disclosed in this specification have been described in detail above, these are merely examples and do not limit the scope of the claims. The claimed technology includes various modifications and variations of the specific examples described above. For example, in the above embodiment, earth and sand are excavated when the cylindrical portion rotates clockwise. However, the present invention is not limited to such examples. The scope of the present invention also includes configurations in which earth and sand are excavated when the cylindrical portion rotates in the opposite direction to the above embodiment, and configurations in which the fixed positions of the opening and closing doors are reversed from the above embodiment. Furthermore, the technical elements described in this specification or drawings may exhibit technical utility alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. [Explanation of symbols]

[0044] 10 Attachments 11 Drive unit 12 Cylindrical part 15 Crushed stone injection hole 22 shaft 26, 26A, 26B joint rod 26a First end 26b Second end 26c 1st opening 26d 2nd opening 27 Output shaft 57 Bearing 61 Cylindrical body 62 First end member 62a Top opening 62b Support recess 63 Second end member 63a Bottom opening 63b Expanded diameter space 64 1st center hole 65 2nd center hole 71 Core material 72 1st enlarged diameter section 73 Second enlarged diameter section 100 Crushed stone pile forming device

Claims

1. An attachment for forming a crushed stone pile is attached to a crushed stone pile forming device that forms a crushed stone pile in a space formed in the ground, is inserted into the ground to form the space, and forms a crushed stone pile in the space while rising from the ground, a cylindrical portion having a crushed stone injection hole formed on its side; a shaft rotatably disposed within the cylindrical portion and rotated by a driving force from a driving device; a hollow joint rod having a first end and a second end, the first end being connected to an output shaft of the drive device and the second end being connected to the shaft; a core member disposed within the joint rod, the upper end of which is engaged with the first end of the joint rod and the lower end of which is engaged with the second end of the joint rod; An attachment for forming crushed stone piles.

2. 2. An attachment for forming crushed stone piles as described in claim 1, wherein the joint rod comprises a cylindrical main body having a first opening on the first end side and a second opening on the second end side, a first end member joined to the first opening of the cylindrical main body, and a second end member joined to the second opening of the cylindrical main body.

3. 3. The attachment for forming a crushed stone pile according to claim 2, wherein the upper end of the core material is inserted into a first central hole of the first end member and is welded and fixed to the first end member.

4. 3. The attachment for forming a crushed stone pile according to claim 2, wherein a lower end of the core material is fitted into a second center hole of the second end member.

5. a support recess is formed at an upper end opening of a first center hole of the first end member; a first enlarged diameter portion having a diameter larger than that of the first central hole is formed at an upper end of the core material; The crushed stone pile forming attachment according to claim 2 , wherein the first enlarged diameter portion is supported by the support recess.

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