Construction machine

Abstract

To provide a construction machine having a casing which can satisfactorily maintain length thereof at the time of excavation while being expandable / contractible.SOLUTION: A casing includes: an axial direction guide passage 54 which is partitioned on the inner surface of a first casing body 34 and extends in an axial direction; a projection piece which is installed on the outer surface of a second casing body, enters the axial direction guide passage 54, and guides an axial direction relative displacement of the second casing body to the first casing body 34; a first circumferential direction guide passage 56 which is continuous from the upper end of the axial direction guide passage 54, extends in a circumferential direction in a direction opposite to a rotation direction DR at the time of excavation, receives entry of the projection piece, and regulates the axial direction relative displacement of the second casing body to the first casing body 34; and a second circumferential guide passage 57 which is continuous from the lower end of the axial direction guide passage 54, extends in the circumferential direction in the direction opposite to the rotation direction DR at the time of excavation, receives entry of the projection piece, and regulates the axial direction relative displacement of the second casing body to the first casing body 34.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a construction machine including a cylindrical first casing body driven around an axis, and a cylindrical second casing body coaxially accommodated inside the first casing body and having a drilling bit at its lower end, the drilling bit being located below the first casing body.

Background Art

[0002] Patent Document 1 discloses a casing that is used for ground cutting in pile pulling and expands and contracts in the axial direction. The casing includes a first cylindrical body driven by a hydraulic pump around a vertical axis, a second cylindrical body coaxially accommodated inside the first cylindrical body and displaced axially with respect to the first cylindrical body, and a third cylindrical body coaxially accommodated inside the second cylindrical body and displaced axially with respect to the second cylindrical body. The casing excavates the ground while rotating around a vertical axis. A pile is accommodated inside the casing. Friction is cut around the pile. The casing expands in accordance with the length of the pile prior to excavation. Since replacement and addition of the casing are omitted, the work efficiency of pile pulling can be increased.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] When excavating, a reaction force acts on the casing from the ground. The casing must maintain its length against the reaction force from the ground. In Patent Document 1, it is difficult to maintain the length. Further, in Patent Document 1, although water is jetted from the lower end of the casing during excavation, a second cylindrical body and a sheave are essential for arranging the water hose. The complication of the structure is inevitable, and moreover, the sheave and the rope are not suitable for operation in the ground.

[0005] An object of the present invention is to provide a construction machine including a casing that can maintain a good length during excavation while being stretchable.

Means for Solving the Problems

[0006] According to one aspect of the present invention, there is provided a cylindrical first casing body driven around an axis, a cylindrical second casing body coaxially accommodated inside the first casing body and having an excavation bit at a lower end, the excavation bit being located below the first casing body, an axial guide path defined on an inner surface of the first casing body and extending in an axial direction, a projecting piece installed on an outer surface of the second casing body, entering the axial guide path, and guiding an axial relative displacement of the second casing body with respect to the first casing body, a first circumferential guide path continuous from an upper end of the axial guide path, extending circumferentially in a direction opposite to a rotation direction during excavation, receiving the entry of the projecting piece, and restricting the axial relative displacement of the second casing body with respect to the first casing body, and a second circumferential guide path continuous from a lower end of the axial guide path, extending circumferentially in a direction opposite to a rotation direction during excavation, receiving the entry of the projecting piece, and restricting the axial relative displacement of the second casing body with respect to the first casing body.

[0007] The first casing body and the second casing body form one casing. The casing expands and contracts by the relative displacement of the second casing body in the axial direction with respect to the first casing body. In the expansion and contraction, the projecting piece of the second casing body is guided by the axial guide path inside the first casing body.

[0008] When the lug enters the first circumferential guide path, the casing is shortened to the maximum extent. The second casing body is accommodated in the first casing body to the maximum extent. When the first casing body is driven around the axis, the drilling bit drills into the ground. At this time, since the first circumferential guide path extends in the direction opposite to the rotational direction during drilling, the lug is held in the first circumferential guide path. The expansion and contraction of the casing are regulated.

[0009] When the lug enters the second circumferential guide path, the casing expands to the maximum extent. The second casing body is pulled out from the first casing body to the maximum extent. When the first casing body is driven around the axis, the drilling bit drills into the ground. At this time, since the second circumferential guide path extends in the direction opposite to the rotational direction of the drilling machine, the lug is held in the second circumferential guide path. The shortening of the casing is regulated. Even when a reaction force acts from the ground, the length of the casing is maintained. In this way, the casing can maintain a good length during drilling while being expandable and contractible.

[0010] When the casing expands, the casing is erected on the ground. When the first casing body is driven in the direction opposite to that during drilling around the axis, the lug of the second casing body enters from the first circumferential guide path into the axial guide path. When the first casing body is pulled upward, the second casing body stays on the ground by its own weight, so the casing can expand. When the first casing body is driven around the axis in the same way as during drilling when the lug reaches the lower end of the axial guide path, the lug enters the second circumferential guide path. In this way, the expanded state of the casing can be fixed.

[0011] When shortening the casing, the casing can likewise be stood on the ground. When the first casing body is driven in the direction opposite to that during excavation around the axis, the protruding piece of the second casing body enters from the second circumferential guide path into the axial guide path. When the first casing body descends, since the second casing body stands up on the ground, the casing can be shortened. When the first casing body is driven around the axis in the same manner as during excavation when the protruding piece reaches the upper end of the axial guide path, the protruding piece enters the first circumferential guide path. Thus, the shortened state of the casing can be fixed. In this way, modification of the construction machine can be avoided when the casing expands and contracts. There is no need to add a drive source specific to expansion and contraction.

[0012] The construction machine may include a first water pipe attached to the outer surface of the first casing body and extending downward axially from the upper end of the first casing body, a second water pipe attached to the outer surface of the second casing body and extending downward axially with a jet outlet disposed at the lower end of the second casing body, a connecting pipe connected to the upper end of the second water pipe and protruding through the first casing body to the outer surface of the first casing body, and a water hose disposed along the outer surface of the first casing body and connecting the connecting pipe to the lower end of the first water pipe. Water is introduced into the first water pipe at the upper end of the first casing body. The water flows from the first water pipe, through the water hose and the connecting pipe, into the second water pipe. The water jets out from the jet outlet disposed at the lower end of the second casing body. Thus, water is supplied into the ground during excavation. Since the soil in the ground softens, the resistance to excavation decreases. Efficient excavation can be realized.

[0013] In the first casing body, there may be formed an axially extending long hole that receives the connecting pipe when the protruding piece is located within the axial guide path, a first circumferentially extending long hole that is continuous from the upper end of the axially extending long hole and extends circumferentially in a direction opposite to the rotational direction during excavation and receives the connecting pipe when the protruding piece is located within the first circumferential guide path, and a second circumferentially extending long hole that is continuous from the lower end of the axially extending long hole and extends circumferentially in a direction opposite to the rotational direction during excavation and receives the connecting pipe when the protruding piece is located within the second circumferential guide path. When the casing expands and contracts, when the protruding piece of the second casing body is located within the axial guide path, the connecting pipe is located within the axially extending long hole. When the protruding piece is located within the first circumferential guide path, the connecting pipe is located within the first circumferentially extending long hole. When the protruding piece is located within the second circumferential guide path, the connecting pipe is located within the second circumferentially extending long hole. Since the connecting pipe appears on the outer surface of the first casing body and is visible to the operator, by confirming the positional relationship of the connecting pipe with respect to the axially extending long hole, the first circumferentially extending long hole, and the second circumferentially extending long hole, the position of the protruding piece with respect to the axial guide path, the first circumferential guide path, and the second circumferential guide path can be determined. The expansion and contraction work can be efficiently performed.

Advantages of the Invention

[0014] According to the construction machine disclosed as above, a casing that can be expanded and contracted and can maintain a good length during excavation can be provided.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Modes for Carrying Out the Invention

[0016] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

[0017] FIG. 1 schematically shows a construction machine according to an embodiment of the present invention. The construction machine 11 includes a driving body 13 that supports left and right crawlers 12, and a revolving body 15 that is connected to the driving body 13 so as to be rotatable about a vertical axis and supports an operator's cab 14. An operator rides on the operator's cab 14. The crawlers 12 operate according to the operation of the operator. Based on the operation of the crawlers 12, the construction machine 11 travels.

[0018] A boom 16 is supported by the revolving body 15 so as to be able to rise and fall about a horizontal axis. The boom 16 includes a first body 16a connected to the revolving body 15, a second body 16b that is movably housed in the inner space of the first body 16a in the advancing and retreating directions, and a third body 16c that is movably housed in the inner space of the second body 16b in the advancing and retreating directions. A hydraulic cylinder is connected between the boom 16 and the revolving body 15. The raising and lowering of the boom 16 is realized according to the expansion and contraction of the hydraulic cylinder. A hydraulic cylinder is connected between the first body 16a and the second body 16b. A hydraulic cylinder is connected between the second body 16b and the third body 16c. The boom 16 can expand and contract in a telescopic manner according to the expansion and contraction of the hydraulic cylinder. Each hydraulic cylinder is connected to a hydraulic circuit. The hydraulic pressure of a hydraulic source can be supplied to each hydraulic cylinder by the action of the hydraulic circuit.

[0019] A leader 21 is connected to the tip of the boom 16 so as to be swingable about a horizontal axis. Depending on the angle and length of the boom 16, the leader 21 can stand upright on the ground GD. An auger unit 22 is connected to the leader 21. The auger unit 22 includes a slider 23 guided by the leader 21 and moving up and down along the leader 21, a hydraulic motor 25 coupled to the slider 23 and generating a driving force about a vertical axis 24 based on the hydraulic pressure supplied from a hydraulic circuit, and a casing 26 connected to the hydraulic motor 25 and rotating about the vertical axis 24. A sheave 27 is rotatably coupled to the slider 23 about a horizontal axis. A wire 29 wound up by a winch 28 is wound around the sheave 27. The winch 28 operates according to the hydraulic pressure supplied from the hydraulic circuit. The up and down movement of the slider 23 is caused according to the operation of the winch 28. As shown in FIG. 2, a water passage 32 through which water flows from a water supply system 31 along the boom 16, for example, is partitioned in the hydraulic motor 25.

[0020] As shown in FIG. 2, the casing 26 includes a cylindrical first casing body 34 connected to the hydraulic motor 25 and driven about an axis (here, the vertical axis 24), and a cylindrical second casing body 36 coaxially housed inside the first casing body 34 and having a boring bit 35 at the lower end. The second casing body 36 can be axially displaced between a first position where it is maximally housed in the first casing body 34 to establish a shortened state of the casing 26 and a second position where it is maximally pulled downward from the first casing body 34 as shown in FIG. 3 to establish an extended state of the casing 26. The second casing body 36 includes a main body 36a having an outer diameter to be housed in the first casing body 34, and a diameter-expanded body 36b coupled to the lower end of the main body 36a and having an outer diameter larger than that of the main body 36a. The diameter-expanded body 36b is maintained below the first casing body 34 even in the shortened state of the casing 26. As a result, the boring bit 35 is positioned below the first casing body 34 even in the shortened state or the extended state of the casing 26.

[0021] On the outer surface of the first casing body 34, a first water pipe 37 extending downward in the axial direction from the upper end of the first casing body 34 is attached. The upper end of the first water pipe 37 is connected to the water channel 32 at the upper end of the first casing body 34. Even when the first casing body 34 rotates around the vertical axis 24 by the action of the hydraulic motor 25, water can be supplied from the water channel 32 to the first water pipe 37.

[0022] On the outer surface of the second casing body 36, a second water pipe 39 extending downward in the axial direction from the upper end of the second casing body 36 and having a jet outlet 38 disposed at the lower end of the second casing body 36 is attached. At the upper end of the second water pipe 39, a connecting pipe 42 passing through the first casing body 34 and protruding to the outer surface of the first casing body 34 is connected. As shown in FIG. 4, the connecting pipe 42 includes an upright pipe 43 standing upright from the outer surface of the second casing body 36 along a radial line orthogonal to the vertical axis 24 in the second casing body 36, and a circumferential pipe 44 extending circumferentially along the outer surface of the second casing body 36 from the inner end of the upright pipe 43 and connecting the upper end of the second water pipe 39 to the inner end of the upright pipe 43. The water flowing into the upright pipe 43 is distributed from the circumferential pipe 44 to the individual second water pipes 39.

[0023] The upright pipe 43 penetrates the wall of the first casing body 34. A swivel joint 45 is coupled to the outer end of the upright pipe 43. A water hose 46 is connected to the swivel joint 45 outside the outer surface of the first casing body 34. The swivel joint 45 allows the rotation of the water hose 46 around the axis of the upright pipe 43.

[0024] The water hose 46 connects the lower end of the first water pipe 37 to the outer end of the upright pipe 43 as shown in FIG. 2. The water hose 46 is disposed along the outer surface of the first casing body 34. Four hose covers 47 for securing the movement path of the water hose 46 between the outer surface of the first casing body 34 are attached to the outer surface of the first casing body 34. The hose cover 47 can cover the water hose 46 even when the water hose 46 is deformed during the expansion and contraction of the casing 26. Water is supplied to the jet outlet 38 through the water supply system 31, the water channel 32, the first water pipe 37, the water hose 46, and the second water pipe 39. The water jets out from the jet outlet 38.

[0025] In the first casing body 34, there are formed an axially extending axial guide path 51 into which the vertical pipe 43 is received when the casing 26 expands and contracts, a first circumferential guide path 52 that is continuous from the upper end of the axial guide path 51 and extends circumferentially in a direction opposite to the rotational direction DR during excavation, and a second circumferential guide path 53 that is continuous from the lower end of the axial guide path 51 and extends circumferentially in a direction opposite to the rotational direction DR during excavation. The axial guide path 51 is set to a length that allows displacement of the vertical pipe 43 when the casing 26 expands and contracts between the shortened state and the extended state. The first circumferential guide path 52 is set to a length that allows displacement of the vertical pipe 43 when the second casing body 36 rotates relative to the first casing body 34 about the vertical axis 24 in the shortened state of the casing 26. The second circumferential guide path 53 is set to a length that allows displacement of the vertical pipe 43 when the second casing body 36 rotates relative to the first casing body 34 about the vertical axis 24 in the extended state of the casing 26. When the first casing body 34 is driven in the rotational direction DR during excavation about the vertical axis 24 in the shortened state of the casing 26, the vertical pipe 43 enters the first circumferential guide path 52. When the first casing body 34 is driven in the rotational direction DR during excavation about the vertical axis 24 in the extended state of the casing 26, the vertical pipe 43 enters the second circumferential guide path 53.

[0026] As shown in FIG. 4, an axially extending axial guide path 54 is defined on the inner surface of the first casing body 34. Here, three axial guide paths 54 are provided at equal angular intervals. Rails 54a and 54b are fixed to the inner surface of the first casing body 34 for forming each axial guide path 54.

[0027] On the outer surface of the second casing body 36, there is provided a protruding piece 55 that enters the axial guide path 54 and guides the axial displacement of the second casing body 36 with respect to the first casing body 34. The protruding piece 55 is disposed at the upper end on the outer peripheral surface of the second casing body 36. The axial guide path 54 is set to a length that allows displacement of the protruding piece 55 when the casing 26 expands and contracts between the shortened state and the extended state. The upper end of the axial guide path 54 defines the shortened state of the casing 26. The lower end of the axial guide path 54 defines the extended state of the casing 26.

[0028] As shown in FIG. 5, at the upper end of the axial guide path 54, a first circumferential guide path 56 extending in the circumferential direction opposite to the rotational direction DR during excavation is connected. The first circumferential guide path 56 is defined by a plate material connected to the upper ends of the rails 54a and 54b. The first circumferential guide path 56 receives the entry of the protruding piece 55 when the first casing body 34 is driven in the rotational direction DR during excavation around the vertical axis 24 in the shortened state of the casing 26. The first circumferential guide path 56 is interrupted at a length that restricts the relative displacement of the second casing body 36 with respect to the first casing body 34 when the protruding piece 55 enters.

[0029] At the lower end of the axial guide path 54, a second circumferential guide path 57 extending in the circumferential direction opposite to the rotational direction DR during excavation is connected. The second circumferential guide path 57 is defined by a plate material connected to the lower ends of the rails 54a and 54b. The second circumferential guide path 57 receives the entry of the protruding piece 55 when the first casing body 34 is driven in the rotational direction DR during excavation around the vertical axis 24 in the extended state of the casing 26. The second circumferential guide path 57 is interrupted at a length that restricts the relative displacement of the second casing body 36 with respect to the first casing body 34 when the protruding piece 55 enters.

[0030] An introduction path 58 is continuous with the lower end of the axial guide path 54. The introduction path 58 is open downward at the lower end of the second casing body 36. When the second casing body 36 is accommodated with respect to the first casing body 34, the protruding piece 55 can enter the axial guide path 54 from the open end of the introduction path 58.

[0031] A stopper pin 61 is disposed in the introduction path 58. The stopper pin 61 defines the lower end of the axial guide path 54. The stopper pin 61 is inserted from the outer surface of the first casing body 34 and protrudes from the inner surface of the first casing body 34 in the introduction path 58. The entry of the protruding piece 55 from the axial guide path 54 into the introduction path 58 is blocked by the action of the stopper pin 61. The stopper pin 61 may be detachably fixed to the first casing body 34. Here, an excavation bit 62 is installed at the lower end of the first casing body 34.

[0032] As shown in FIG. 2, a first hose guard 63a, a second hose guard 63b, and a third hose guard 63c are attached to the outer surface of the first casing body 34. The first, second, and third hose guards 63a, 63b, 63c are formed of plate materials that stand up at a height determined from the outer surface of the first casing body 34. The first hose guard 63a is disposed upstream of the first water pipe 37 and the water hose 46 in the rotational direction DR during excavation. The first hose guard 63a protects the joint that connects the water hose 46 to the first water pipe 37 during excavation. The second hose guard 63b is disposed so as to surround the first circumferential long hole 52 in the upper side and the circumferential direction. The second hose guard 63b protects the swivel joint 45 that connects the water hose 46 to the connecting pipe 42 during excavation in the shortened state. The third hose guard 63c is disposed so as to surround the second circumferential long hole 53 in the lower side and the circumferential direction. The third hose guard 63c protects the swivel joint 45 that connects the water hose 46 to the connecting pipe 42 during excavation in the extended state.

[0033] Next, the operation of the construction machine 11 will be described. When performing ground cutting for pile extraction, the casing 26 is attached to the construction machine 11. The first casing body 34 and the second casing body 36 form one casing 26. Here, the shortened state of the casing 26 is established. The second casing body 36 is positioned at an angular position that holds the protruding piece 55 in the first circumferential guide path 56 with respect to the first casing body 34. The protruding piece 55 fits, for example, at the downstream end of the first circumferential guide path 56 in the rotational direction DR during excavation. The upright pipe 43 of the connecting pipe 42 is located at the downstream end of the first circumferential long hole 52 in the rotational direction DR during excavation. The second casing body 36 is accommodated in the first casing body 34 to the maximum extent.

[0034] As shown in FIG. 1, the leader 21 is erected on the ground GD. The leader 21 is orthogonal to the ground GD. The raising and lowering angle and the length of the boom 16 are adjusted according to the length of the leader 21. Hydraulic pressure is supplied from the hydraulic circuit to the corresponding hydraulic cylinders for adjusting the raising and lowering angle and the length.

[0035] The casing 26 is erected on the ground GD. When the casing 26 touches down, the winch 28 operates. Reflecting the posture of the leader 21, the casing 26 is orthogonal to the ground GD. Here, water can be supplied to the casing 26 from the water supply system 31. Water jets out from the lower end of the second casing body 36 in response to the supply of water.

[0036] The casing 26 is driven around the vertical axis 24. The boring bit 35 of the second casing body 36 bores into the ground GD. When the casing 26 descends, the winch 28 operates. Piles are accommodated inside the second casing body 36. The friction between the pile and the ground is cut off by the function of the casing 26. When the cutting of the friction is completed, the casing 26 is pulled up. Thereafter, the pile is pulled out.

[0037] When the length of the pile is longer than the casing 26 in the shortened state, the casing 26 is switched from the shortened state to the extended state. When switching, the casing 26 is erected on the ground GD. The casing 26 is driven around the vertical axis 24 in the direction opposite to the rotation direction DR during boring. At this time, the driving force of the hydraulic motor 25 acts on the first casing body 34, while the rotation of the second casing body 36 is blocked according to the friction between the lower end of the second casing body 36 and the ground GD. Thus, the protruding piece 55 enters from the first circumferential guide path 56 into the axial guide path 54. The protruding piece 55 is located at the upper end of the axial guide path 54. The upright pipe 43 of the connecting pipe 42 is located at the upper end of the axial long hole 51. Here, in response to the relative displacement in the circumferential direction, the first casing body 34 may be pulled up slightly so that the friction between the first circumferential guide path 56 and the protruding piece 55 is reduced.

[0038] When the tab 55 enters the axial guide path 54, the drive of the casing 26 is stopped. The second casing body 36 is positioned relative to the first casing body 34 at an angular position that allows displacement of the tab 55 within the axial guide path 54. Subsequently, the first casing body 34 is pulled upward. The tab 55 is displaced axially along the axial guide path 54. At this time, since the regulation of the axial relative displacement is released, only the first casing body 34 is pulled up and the second casing body 36 remains on the ground GD under its own weight. Thus, the casing 26 can be extended. As the first casing body 34 is pulled up, the vertical pipe 43 of the connecting pipe 42 rises axially along the axial elongated hole 51.

[0039] When the extended state of the casing 26 is established, the pulling up of the first casing body 34 is stopped. The tab 55 reaches the lower end of the axial guide path 54. The vertical pipe 43 of the connecting pipe 42 reaches the lower end of the axial elongated hole 51. Subsequently, the casing 26 is driven to rotate about the vertical axis 24 in the drilling rotation direction DR. The tab 55 enters from the lower end of the axial guide path 54 into the second circumferential guide path 57. The extended state of the casing 26 can be fixed. The second casing body 36 is positioned relative to the first casing body 34 at an angular position that holds the tab 55 in the second circumferential guide path 57. The tab 55, for example, fits into the downstream end of the second circumferential guide path 57 in the drilling rotation direction DR. The function of the tab 55 and the second circumferential guide path 57 restricts the axial displacement of the second casing body 36 relative to the first casing body 34. The vertical pipe 43 of the connecting pipe 42 is located at the downstream end of the second circumferential elongated hole 53 in the drilling rotation direction DR.

[0040] The extended casing 26 is driven to rotate about the vertical axis 24. The drilling bit 35 of the second casing body 36 drills into the ground GD. When the casing 26 descends, the winch 28 operates. The piles are accommodated inside the second casing body 36. The function of the casing 26 cuts off the friction between the piles and the ground. When the cutting of the friction is completed, the casing 26 is pulled up. Thereafter, the piles are pulled out.

[0041] When shortening the casing 26, the casing 26 is erected on the ground GD. The casing 26 is driven to rotate around the vertical axis 24 in the direction opposite to the rotation direction DR during excavation. At this time, the driving force of the hydraulic motor 25 acts on the first casing body 34, while the rotation of the second casing body 36 is blocked according to the friction between the lower end of the second casing body 36 and the ground GD. The protruding piece 55 enters from the second circumferential guide path 57 into the axial guide path 54. The protruding piece 55 is located at the lower end of the axial guide path 54. The upright pipe 43 of the connecting pipe 42 is located at the lower end of the axial long hole 51. Here, in the case of circumferential relative displacement, the first casing body 34 may be lifted slightly, and the friction between the second circumferential guide path 57 and the protruding piece 55 may be reduced.

[0042] When the protruding piece 55 enters the axial guide path 54, the driving of the casing 26 is stopped. The second casing body 36 is positioned relative to the first casing body 34 at an angular position that allows the displacement of the protruding piece 55 within the axial guide path 54. Subsequently, the first casing body 34 descends. At this time, since the second casing body 36 stands upright on the ground, the casing 26 can be shortened. The protruding piece 55 is displaced axially along the axial guide path 54. Since the regulation of the axial relative displacement is released, the first casing body 34 moves downward to accommodate the second casing body 36. As the first casing body 34 descends, the upright pipe 43 of the connecting pipe 42 descends axially along the axial long hole 51.

[0043] When the shortened state of the casing 26 is established, the downward movement of the first casing body 34 is stopped. The protruding piece 55 reaches the upper end of the axial guide path 54. The upright pipe 43 of the connecting pipe 42 reaches the upper end of the axial long hole 51. Subsequently, the casing 26 is driven around the vertical axis 24 in the rotational direction DR during excavation. The protruding piece 55 enters the first circumferential guide path 56 from the upper end of the axial guide path 54. In this way, the shortened state of the casing 26 can be fixed. The second casing body 36 is positioned with respect to the first casing body 34 at an angular position that holds the protruding piece 55 in the first circumferential guide path 56. The protruding piece 55, for example, fits into the downstream end of the first circumferential guide path 56 in the rotational direction DR during excavation. The function of the protruding piece 55 and the first circumferential guide path 56 restricts the axial displacement of the second casing body 36 with respect to the first casing body 34. The upright pipe 43 of the connecting pipe 42 is located at the downstream end of the first circumferential long hole 52 in the rotational direction DR during excavation.

[0044] As described above, when the protruding piece 55 enters the first circumferential guide path 56, the casing 26 is shortened to the maximum extent. The second casing body 36 is accommodated in the first casing body 34 to the maximum extent. When the first casing body 34 is driven around the vertical axis 24, the excavation bit 35 excavates the ground GD. At this time, since the first circumferential guide path 56 extends in the direction opposite to the rotational direction DR during excavation, the protruding piece 55 is held in the first circumferential guide path 56. The expansion and contraction of the casing 26 are restricted.

[0045] On the other hand, when the protruding piece 55 enters the second circumferential guide path 57, the casing 26 extends to the maximum extent. The second casing body 36 is pulled out from the first casing body 34 to the maximum extent. When the first casing body 34 is driven around the vertical axis 24, the excavation bit 35 excavates the ground GD. At this time, since the second circumferential guide path 57 extends in the direction opposite to the rotational direction DR during excavation, the protruding piece 55 is held in the second circumferential guide path 57. The shortening of the casing 26 is restricted. Even if a reaction force acts from the ground GD, the length of the casing 26 is maintained. In this way, the casing can maintain a good length during excavation while being expandable and contractible.

[0046] When the casing 26 is extended, the casing 26 is erected on the ground GD. When the first casing body 34 is driven in a direction opposite to that during excavation around the vertical axis 24, the projection 55 of the second casing body 36 enters from the first circumferential guide path 56 into the axial guide path 54. When the first casing body 34 is pulled upward, since the second casing body 36 stays on the ground under its own weight, the casing 26 can be extended. When the projection 55 reaches the lower end of the axial guide path 54 and the first casing body 34 is driven in the same direction as during excavation around the vertical axis 24, the projection 55 enters the second circumferential guide path 57. In this way, the extended state of the casing 26 can be fixed.

[0047] When the casing 26 is shortened, the casing 26 is similarly erected on the ground GD. When the first casing body 34 is driven in a direction opposite to that during excavation around the vertical axis 24, the projection 55 of the second casing body 36 enters from the second circumferential guide path 57 into the axial guide path 54. When the first casing body 34 descends, since the second casing body 36 stands up on the ground, the casing 26 can be shortened. When the projection 55 reaches the upper end of the axial guide path 54 and the first casing body 34 is driven in the same direction as during excavation around the vertical axis 24, the projection 55 enters the first circumferential guide path 56. In this way, the shortened state of the casing 26 can be fixed. In this manner, modifications to the construction machine 11 can be avoided when the casing 26 expands and contracts. A drive source specific to expansion and contraction does not need to be added.

[0048] In this embodiment, water is introduced into the first water pipe 37 at the upper end of the first casing body 34. The water flows from the first water pipe 37 into the second water pipe 39 through the water hose 46 and the connecting pipe 42. The water jets out from the jet outlet 38 disposed at the lower end of the second casing body 36. In this way, water is supplied into the ground during excavation. Since the soil in the ground softens, the resistance to excavation decreases. Efficient excavation can be realized.

[0049] In the construction machine 11 according to the present embodiment, when the projecting piece 55 of the second casing body 36 is located in the axial guide path 54 during the expansion and contraction of the casing 26, the upright pipe 43 of the connecting pipe 42 is located in the axial long hole 51. When the projecting piece 55 is located in the first circumferential guide path 56, the upright pipe 43 of the connecting pipe 42 is located in the first circumferential long hole 52. When the projecting piece 55 is located in the second circumferential guide path 57, the upright pipe 43 of the connecting pipe 42 is located in the second circumferential long hole 53. Since the connecting pipe 42 appears on the outer appearance of the first casing body 34 and is visible to the operator, by checking the positional relationship of the connecting pipe 42 with respect to the axial long hole 51, the first circumferential long hole 52, and the second circumferential long hole 53, the position of the projecting piece 55 with respect to the axial guide path 54, the first circumferential guide path 56, and the second circumferential guide path 57 can be determined. The expansion and contraction work can be efficiently performed.

Explanation of Reference Numerals

[0050] 11... Construction machine, 34... First casing body, 35... Excavation bit, 36... Second casing body, 37... First water pipe, 38... Jet outlet, 39... Second water pipe, 42... Connecting pipe, 46... Water hose, 51... Axial long hole, 52... First circumferential long hole, 53... Second circumferential long hole, 54... Axial guide path, 55... Projecting piece, 56... First circumferential guide path, 57... Second circumferential guide path, DR... Rotation direction during excavation.

Claims

1. a cylindrical first casing body driven about an axis; a cylindrical second casing body coaxially accommodated inside the first casing body and having, at its lower end, a drilling bit positioned below the first casing body; an axial guide path defined on the inner surface of the first casing body and extending in the axial direction; a projection provided on the outer surface of the second casing body, entering the axial guide path, and guiding the axial relative displacement of the second casing body with respect to the first casing body; a first circumferential guide path continuous from the upper end of the axial guide path, extending circumferentially in a direction opposite to the rotational direction during drilling, receiving the entry of the projection, and restricting the axial relative displacement of the second casing body with respect to the first casing body; a second circumferential guide path continuous from the lower end of the axial guide path, extending circumferentially in a direction opposite to the rotational direction during drilling, receiving the entry of the projection, and restricting the axial relative displacement of the second casing body with respect to the first casing body; a construction machine, characterized by comprising the above.

2. The construction machine according to claim 1, wherein a first water pipe attached to the outer surface of the first casing body and extending axially downward from the upper end of the first casing body; a second water pipe attached to the outer surface of the second casing body, extending axially downward, and having a jet outlet disposed at the lower end of the second casing body; a connecting pipe connected to the upper end of the second water pipe, passing through the first casing body, and protruding to the outer surface of the first casing body; a water hose disposed along the outer surface of the first casing body and connecting the connecting pipe to the lower end of the first water pipe a construction machine, characterized by comprising the above.

3. The construction machine according to claim 2, wherein the first casing body is formed with an axial elongated hole extending in the axial direction and receiving the connecting pipe when the projection is positioned within the axial guide path, a first circumferential elongated hole continuous from the upper end of the axial elongated hole, extending circumferentially in a direction opposite to the rotational direction during drilling, and receiving the connecting pipe when the projection is positioned within the first circumferential guide path, and a second circumferential elongated hole continuous from the lower end of the axial elongated hole, extending circumferentially in a direction opposite to the rotational direction during drilling, and receiving the connecting pipe when the projection is positioned within the second circumferential guide path.

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