JP6636549B2 - Drilling head - Google Patents

Description

  The present invention relates to a drilling head having a drilling bit provided on a drilling wing.

  2. Description of the Related Art Conventionally, an excavator for excavating a ground is provided with an excavation head for excavating the ground at a lower end of a rotating shaft. In this excavating head, a horizontal wing-shaped or spiral wing-shaped excavating wing is provided at a lower end of a rotating shaft, and an excavating bit is provided on the excavating wing (for example, see Patent Document 1).

  In a conventional excavating head, in the case of a configuration in which horizontal wings are provided at the lower end of a plurality of spiral wings of the same diameter, a plurality of excavating bits are arranged and mounted on the horizontal wing at the lower end, and upward from the lower end. In the case of a configuration in which spiral wings whose diameters are enlarged toward the wings are provided, a plurality of drill bits are mounted side by side along the outer circumference of the spiral wings.

JP 2004-9200 A

  However, in the above-described conventional excavating head, when a plurality of excavating bits are arranged side by side on the horizontal wing at the lower end, there is a possibility that the excavation resistance during excavation increases.

  In particular, in soil improvement work in which the ground is excavated and the solidified material is mixed with the excavated earth and sand and agitated, the excavation diameter becomes very large compared to the excavation work, so the excavation resistance during construction is extremely large. There is a risk of becoming.

  Further, in the above conventional drilling head, in the case of a configuration in which a plurality of drill bits are mounted side by side along the outer periphery of the spiral wing whose diameter is increased upward from the lower end, a conical portion which is drilled by the enlarged spiral wing. (Conical column body) may be long.

  In particular, in soil improvement work, the columnar column formed above the conical column is a product that exhibits effective strength, and the conical column is invalid because it is invalid. There is a risk that the long conical column body will become long.

Therefore, in the present invention according to claim 1, in a drilling head having a spiral drilling wing whose diameter is increased upward from a lower end, and a drilling bit is provided on the drilling wing, the drilling wing is provided stepwise in the middle of the drilling wing. While forming a plurality of stepped parts having an enlarged diameter, a plurality of drilling bits are arranged in each step, and another drilling bit is provided on the lower surface of the drilling wing behind the plurality of drilling bits arranged in each step. was Rukoto provided so as to be positioned between the drill bit aligned.

Further, in the present invention according to claim 2 , in the present invention according to claim 1 , a plurality of excavating bits provided side by side on each of the step portions are shifted forward and backward on an inner peripheral side and an outer peripheral side of the excavation wing, respectively. I decided to arrange.

  The present invention has the following effects.

  That is, in the present invention, in a drilling head having a spiral drilling wing whose diameter is increased upward from the lower end, and a drilling bit provided on the drilling wing, a step in which the diameter is gradually increased in the middle of the drilling wing. Since the portion is formed and the excavation bit is provided in the step portion, the length of the conical column body can be shortened while reducing excavation resistance during excavation.

  In addition, when a plurality of excavation bits are provided on the excavation wing, and excavation bits are also provided between the plurality of excavation bits and at a rear position, excavation of the ground can be favorably performed.

  Furthermore, when a plurality of excavation bits are provided on the excavation wing, and the plurality of excavation bits are arranged to be shifted back and forth on the inner peripheral side and the outer peripheral side of the excavation wing, depending on the condition of the ground to be excavated. Excavation of the ground can be performed well.

  The plurality of excavation bits may be provided on a step portion of the excavation wing.

The side view which shows a ground improvement apparatus. The side view which shows a drilling head. FIG. The same part enlarged bottom view. Explanatory drawing (a front view (a), a side surface partial sectional view (b)) showing a conical bit. Explanatory drawing (a front view (a), a side surface partial sectional view (b)) showing a conical bit. Explanatory drawing (a front view (a), a side surface partial sectional view (b)) showing a conical bit. Explanatory drawing (a front view (a), a side surface partial sectional view (b)) showing a conical bit. Explanatory drawing (a front view (a), a side surface partial sectional view (b)) showing a conical bit. Explanatory drawing (a front view (a), a side surface partial sectional view (b)) showing a conical bit. Explanatory drawing (a front view (a), a side surface partial sectional view (b)) showing a conical bit. Explanatory drawing (a front view (a), a side surface partial sectional view (b)) showing a conical bit. Explanatory drawing (a front view (a), a side surface partial sectional view (b)) showing a conical bit.

  Hereinafter, a specific configuration of the present invention will be described with reference to the drawings. In the following description, a case will be described in which the present invention is applied to a ground improvement device that improves the ground excavated together with the excavation of the ground. However, the present invention is not limited to this, and the present invention is applicable to various devices that excavate the ground. Can be applied.

  As shown in FIGS. 1 to 3, the ground improvement apparatus 1 excavates the ground 2 and improves the strength and properties of the ground 2 by stirring and mixing the excavated soil and the ground improvement material (solidified material). It is a device that can do. In the ground improvement device 1, a column 4 is erected at a front end of a heavy machine 3 and a drilling device 5 is attached to the column 4 so as to be able to move up and down. A ground improvement material supply mechanism 6 is connected to the excavator 5 via a swivel joint 7. The ground improvement material supply mechanism 6 connects the ground improvement material storage tank 8 and the water tank 9 to the ground improvement material mixing plant 10, and connects the ground improvement material mixing pump 10 to the ground improvement material discharge pump 11 to improve the ground. The material is supplied to the excavator 5.

  The excavator 5 has a lifting support 12 mounted on the front side of the support column 4 so as to be able to move up and down, a driving body 13 is mounted on the lifting support 12, and a base end portion of an excavation shaft 14 extended vertically to the driving body 13. (Upper end), and the rotary excavator 15 is attached to the tip (lower end) of the excavation shaft 14. A ground improvement material supply mechanism 6 is connected to the rotary excavation unit 15 so that the supplied ground improvement material can be discharged. Here, the rotary excavation unit 15 performs excavation by rotation, and the ground improvement device 1 also has a function of stirring and mixing the excavated ground with the ground improvement material in addition to the excavation of the ground 2. ing.

  The driving body 13 has a driving motor 18 connected to an inner shaft 16 and an outer shaft 17 constituting the excavating shaft 14 via a reverse transmission 19.

  The excavating shaft 14 is formed in a double tubular shape with a hollow cylindrical inner shaft 16 and an outer shaft 17 having a rotation center axis arranged coaxially. The excavating shaft 14 projects the tip of the inner shaft 16 downward from the tip of the outer shaft 17. By driving the drive motor 18, the inner shaft 16 or the outer shaft 17 rotates relatively in the opposite direction by the action of the reversing transmission 19.

  The rotary excavator 15 has an excavating head 20 and a stirring blade 21 attached to the extremity (lower end) of the excavating shaft 14 in order from the extremity.

  The digging head 20 has a digging wing 22 attached to the outer peripheral surface of the tip portion of the inner shaft 16 and a plurality of digging bits 23 attached to the digging wing 22. The digging head 20 digs the ground 2 with the digging bit 23 by rotating the digging wing 22 with the rotation of the inner shaft 16. The detailed configuration of the excavation head 20 will be described later.

  The stirring blade 21 includes an innermost stirring blade 24, an inner stirring blade 25 disposed on the outer peripheral side, and an outer stirring blade 26 disposed on the outer peripheral side.

  The innermost stirring blades 24 are radially attached to the outer peripheral surface of the outer shaft 17 at the outer peripheral surface of the outer shaft 17 with two flat innermost stirring blades 27 spaced 180 degrees apart in the circumferential direction. ing.

  The inner stirring blade 25 has two inner stirring blades 28 radially attached to the distal end portion of the inner shaft 16 at a 180-degree interval in the circumferential direction. Each inner stirring blade body 28 includes an inner stirring blade upper piece 29 that extends obliquely toward the outer lower part, an inner stirring blade middle piece 30 that vertically extends downward, and an outer upper part. The lower part 31 of the inner stirring blade extending in a slanted shape has a substantially U-shape in a side view in which the middle part is bulged outward. Each inner stirring blade body 28 attaches the inner stirring blade lower piece 31 to the tip side of the inner shaft 16, attaches the inner stirring blade upper piece 29 to the annular body 32, and attaches the annular body 32 to the outer peripheral surface of the outer shaft 17. It is freely rotatably fitted. In addition, each inner stirring blade body 28 has a stirring piece 33 attached to the outer portion of the inner stirring blade halfway piece 30, and a connecting piece 34 is mounted between the inner stirring blade halfway piece 30 and the inner shaft 16. .

  The outer stirring blades 26 have three outer stirring blades 35 radially attached to the distal end of the outer shaft 17 at intervals of 120 degrees in the circumferential direction. Each outer stirring blade body 35 includes an outer stirring blade upper piece 36 extending obliquely toward the outer lower part, an outer stirring blade middle piece 37 extending vertically downward, and an outer upper part. The outer stirring blade lower piece 38 extending in a slanted shape forms a substantially U-shape in a side view in which the middle part is bulged outward. In each outer stirring blade body 35, the outer stirring blade upper piece 36 is attached to the tip end side of the outer shaft 17, the outer stirring blade lower piece 38 is attached to the annular body 39, and the annular body 39 is attached to the outer peripheral surface of the inner shaft 16. It is freely rotatably fitted. In addition, each outer stirring blade body 35 has a stirring piece 40 attached to the inside of the middle piece 37 of the outer stirring blade.

  The ground improvement device 1 is configured as described above. The details of the excavation head 20 of the excavator 5 which is a main part of the present invention are configured as described below.

  The excavating head 20 has an excavating wing 22 composed of two generally spiral plate-shaped spiral blades 41 and two generally horizontal plate-shaped horizontal blades 42 attached to the tip (lower end) of the inner shaft 16.

  The spiral wing 41 has a spiral portion 43 that continuously increases in diameter upward from the tip (lower end) of the inner shaft 16, and a helical portion 43 that gradually expands in the middle (from the center of the inner shaft 16 in the radial direction). (Extend) step portions 44 are formed in plurality. A plurality of conical bits 45 are attached to each step portion 44 as the drill bits 23 in the radial direction. The conical bit 45 is also attached to the tip (lower end) of the inner shaft 16, the lower surface of the spiral portion 43 of the spiral blade 41, and the outer peripheral portion of the horizontal blade 42.

  In a conventional excavating head, in the case of a configuration in which a plurality of excavating bits are mounted side by side on a horizontal wing, there is a possibility that excavation resistance during excavation increases. In particular, in soil improvement work in which the ground is excavated and the solidified material is mixed with the excavated earth and sand and agitated, the excavation diameter becomes very large compared to the excavation work, so the excavation resistance during construction is extremely large. There is a risk of becoming. Further, in the conventional drilling head, in the case of a configuration in which a plurality of drill bits are mounted side by side along the outer periphery of the spiral blade that has been enlarged upward from the lower end, a conical portion excavated with the enlarged spiral blade ( (Conical column body) may be lengthened. In particular, in soil improvement work, the columnar column formed above the conical column is a product that exhibits effective strength, and the conical column is invalid because it is invalid. There is a risk that the long conical column body will become long.

  However, in the above-mentioned excavating head 20, a stepped portion 44 whose diameter is increased stepwise is formed in the middle of the excavating wing 22 (spiral wing 41), and an excavating bit (conical bit 45) is provided in the stepped portion 44. Therefore, the length of the conical column body can be shortened while reducing the excavation resistance during excavation.

  The conical bits 45 mounted side by side on the steps 44 may be arranged side by side as shown in FIG. 4 (a), and as shown in FIGS. 4 (b) and 4 (c), The peripheral side and the outer peripheral side may be arranged so as to be shifted back and forth. As shown in FIG. 4 (a), when arranged side by side (without shifting back and forth), the ground can be excavated evenly, and the standard ground such as sand or clay ground is targeted. Suitable for. In addition, as shown in FIG. 4 (b), when the conical bit 45 on the inner peripheral side of the excavation wing 22 precedes the conical bit 45 on the outer peripheral side, the inner peripheral part (center part) is excavated earlier. It is suitable for hard ground such as hard ground and bedrock layer. Further, as shown in FIG. 4C, when the conical bit 45 on the outer peripheral side of the excavation wing 22 precedes the conical bit 45 on the inner peripheral side, the conical bit 45 on the outer peripheral side bites into the ground first. By doing so, excavation can be performed while preventing misalignment, which is suitable for the case where the ground such as an inclined support layer is targeted.

  As described above, in the excavating head 20, the plurality of excavating bits (conical bits 45) are arranged to be shifted back and forth between the inner peripheral side and the outer peripheral side of the excavation wing 22 according to the condition of the ground to be excavated. Excavation can be performed well.

  Further, behind the conical bit 45 arranged and mounted on the step portion 44, the conical bit 45 is mounted on the lower surface of the spiral portion 43 of the spiral blade 41 so as to be located between the conical bits 45 in which another conical bit 45 is arranged.

  As described above, in the excavation head 20, by providing the excavation bit (conical bit 45) between the plurality of excavation bits (conical bit 45) and also at the rear position, the excavation of the ground can be performed well. I can do it. Further, ordinary drill bits may be partially interwoven and arranged.

  In the above-described excavating head 20, a plurality of excavating bits (conical bits 45) are arranged side by side on the step portion 44, but the present invention is not limited to this, and a plurality of excavating bits (conical bits 45) are arranged side by side on the spiral portion 43 and the like. You may.

  The conical bit 45 is detachably and rotatably attached to a holder 46 attached to the excavation wing 22 of the excavation head 20.

  As shown in FIG. 5, the conical bit 45 has a bit main body 47 formed on the distal end side, a mounting shaft 48 formed on the base end side, and constricted between the bit main body 47 and the mounting shaft 48. A part 49 and a flange part 50 are formed.

  The bit body 47 has a conical (pointed) superhard (harder than other parts) drilling tip 51 attached to the tip (front end), and linearly expands rearward from the base end of the drilling tip 51. By forming a conical surface with a diameter, a cylindrical surface with the same diameter, a circumferential surface curved in a curved shape toward the rear, and a cylindrical surface with the same diameter, the outer peripheral surface is a discontinuous surface having a corner portion. , At the base end (rear end).

  The mounting shaft portion 48 forms a small-diameter cylindrical base end on the base end side (rear side) of the large-diameter cylindrical front end (front end). Correspondingly, the holder 46 has a large-diameter circular end into which the distal end of the mounting shaft 48 is inserted and a small-diameter circular end into which the base end of the mounting shaft 48 is inserted. A mounting hole 52 having a through hole shape is formed. The conical bit 45 is attached to and detached from the holder 46 by inserting the mounting shaft portion 48 into the mounting hole 52 of the holder 46 via a connector 53 (such as a spring pin made of an elastic material having a C-shaped cross section). It can be freely and rotatably mounted. The connecting tool 53 is housed in a housing recess 54 formed by reducing the diameter of the distal end of the mounting shaft 48.

  The constricted portion 49 is smaller in diameter than the base end (rear end) of the bit main body 47 and the front end (front end) of the flange portion 50, so that the conical bit 45 can be gripped by a tool when attaching and detaching the conical bit 45. .

  The diameter of the flange portion 50 is larger than the opening diameter of the distal end of the mounting hole 52 of the holder 46, and the flange portion 50 comes into contact with the distal end of the holder 46 with the conical bit 45 attached to the holder 46. The diameter of the conical bit 45 is smaller than that of the holder 46 as a whole, so that the conical bit 45 does not come out of the holder 46 when the excavation head 20 rotates in the ground in the reverse direction of the excavation.

  In a conventional conical bit, there is a possibility that the mounting shaft may adhere to the holder due to, for example, earth and sand entering the mounting hole (between the holder and the mounting shaft) during excavation. In particular, in the ground improvement work in which the ground is excavated and the solidified material is mixed with the excavated soil to stir, the solidified material as well as the earth and sand enters the mounting hole, and the intruded solidified material is solidified. As a result, the mounting shaft may be fixed to the holder. In addition, in the ground improvement work, the ground is not self-supporting and is tightened by earth pressure because the sand, gravel, and clay ground layers are excavated rather than the hard rock layers and are stirred with a solidifying agent and the like in the ground. Therefore, there is a possibility that the wear of the drilling tip becomes severe. When the mounting shaft of the conical bit is fixed to the holder, the conical bit cannot rotate with respect to the holder, and the drilling tip at the tip of the conical bit is suddenly biased and worn (one-sided). Therefore, it is necessary to replace the conical bit, which may lead to an increase in cost and an increase in working time. In addition, if the mounting shaft of the conical bit adheres to the holder, it will be difficult to remove the conical bit from the holder, and in some cases it will be necessary to replace the entire holder, which will further increase costs and increase work. There was a risk of inviting.

  Therefore, the conical bit 45 is provided with a fixing preventing means for preventing the mounting shaft portion 48 from being fixed to the holder 46 so as to be unable to rotate. Thereby, in the conical bit 45, the excavation tip 51 at the tip of the conical bit 45 can be prevented from being sharply biased and worn (one-sided) by the sticking prevention means. It is not necessary to replace the conical bit 45 and the holder 46, and the frequency of replacing the conical bit 45 and the holder 46 can be suppressed. Therefore, the cost and work time required for replacing the conical bit 45 and the holder 46 can be reduced.

  In the conical bit 45 shown in FIG. 5, a seal member 55 made of an O-ring or the like is provided as a means for preventing sticking at a position closer to the distal end than the connecting tool 53 interposed between the holder 46 and the mounting shaft portion 48. The seal member 55 is accommodated in a concave portion 56 formed by reducing the diameter at the distal end portion on the distal end side of the accommodating concave portion 54 of the mounting shaft portion 48. Thereby, the conical bit 45 can prevent the earth and sand excavated in the bit main body portion 47 from entering the connecting tool 53 between the holder 46 and the mounting shaft portion 48. Can be prevented from rotating and becoming unable to rotate.

  Further, in the conical bit 45 shown in FIG. 5, a seal member 57 made of an O-ring or the like is provided not only on the distal end side but also on the proximal end side of the connecting tool 53 as an adhesion preventing means. The seal member 57 is housed in a recess 58 formed with a diameter reduced at a base end portion closer to the base end than the housing recess 54 of the mounting shaft portion 48. Thus, intrusion of earth and sand from the rear side of the mounting hole 52 can be prevented. In the conical bit 45, the sealing members 55 and 57 are provided at the large-diameter distal end portion and the small-diameter proximal end portion, thereby preventing the conical bit 45 from wobbling with respect to the holder 46.

  The fixing prevention means may be any configuration that can prevent the mounting shaft portion 48 from being fixed to the holder 46 and becoming unrotatable, and is not limited to the configuration in which the seal members 55 and 57 are provided. Alternatively, other configurations may be used.

  For example, in the conical bit 59 shown in FIG. 6, as a sticking prevention means, the base end side (rear side) of the drilling tip 51 of the bit main body 60 is formed in a truncated polygonal pyramid shape (here, a hexagonal pyramid shape). The outer peripheral surface of the main body 60 has a polygonal pyramid shape (here, a hexagonal pyramid shape), and a cross section orthogonal to the rotation center axis (center line) of the bit main body 60 has a polygonal shape (here, a hexagon). A plurality of (here, six) surface portions of the bit main body 60 are each provided with a plate-shaped carbide tip 61 (having the same hardness as the excavation tip 51) from the distal end to the proximal end. It is extended linearly toward.

  Further, in the conical bit 62 shown in FIG. 7, as a fixing prevention means, the base end side (rear side) of the drilling tip 51 of the bit main body 63 is formed in a truncated polygonal pyramid shape (here, a pentagonal pyramid shape). The outer peripheral surface of the main body 63 has a polygonal pyramid shape (here, a hexagonal pyramid shape), and a cross section orthogonal to the rotation center axis (center line) of the bit main body 63 has a polygonal shape (here, a pentagon). A plurality of (here, five) corner portions of the bit main body 63 are each provided with a plate-shaped carbide tip 64 (having the same hardness as the excavation tip 51) from the distal end to the proximal end. It is extended linearly toward.

  As described above, in the conical bits 59 and 62 shown in FIGS. 6 and 7, since the outer peripheral surfaces of the bit bodies 60 and 63 have a polygonal pyramid shape as the sticking preventing means, the earth pressure received by the bit bodies 60 and 63 is reduced. As a result, a rotational force can be generated in the mounting shaft portion 48, so that the conical bits 59 and 62 are forcibly rotated with respect to the holder 46, and the mounting shaft portion 48 is fixed to the holder 46 and cannot be rotated. Can be prevented. In particular, when the cemented carbide tips 61, 64 harder than the other parts are provided at the corner portions or the surface portions of the polygonal pyramid-shaped bit body portions 60, 63, the outer peripheral surfaces of the bit body portions 60, 63 are worn. Can be prevented.

  Furthermore, in the conventional conical bit, there is a possibility that the holder may be worn and damaged due to, for example, earth and sand contacting the holder during excavation. In particular, in soil improvement works where soil is excavated and solidified material is mixed with the excavated earth and sand and then agitated, the sand, gravel and clay ground layers are excavated rather than hard rock layers and agitated with a solidifying agent and the like in the ground. As a result, the ground is not self-supporting and is tightened by the earth pressure, and the wear of the holder may be increased. If the holder for removably attaching the conical bit is worn and damaged, it becomes necessary to remove the damaged holder from the excavation wing and attach a new holder to the excavation wing. There was a possibility that the time would be increased. Also, if the holder is worn and damaged, it will be difficult to remove the conical bit from the holder, and in some cases, it will be necessary to replace the conical bit together with the holder, further increasing costs and increasing work. Was likely to be caused.

  Therefore, the conical bit 45 shown in FIG. 5 may be provided with a wear suppressing means for suppressing the wear of the holder 46 during excavation. As a result, damage due to wear of the holder 46 can be prevented, and the frequency of replacement of the holder 46, the holder 46, and the conical bit 45 can be suppressed, so that the cost and work time required for replacing the conical bit 45 and the holder 46 are reduced. Can be reduced.

  In the conical bit 65 shown in FIG. 8, as a wear suppressing means, the diameter of the flange portion 66 is made larger than the base end of the bit main body portion 47 (the front end or the base end of the constricted portion 48) so as to cover the front surface of the holder 46. I have to. Thus, in the conical bit 65, the impact of the earth and sand on the holder 46 can be suppressed by the flange portion 66 having the increased diameter, and thus the wear of the holder 46 during excavation can be suppressed. In the conical bit 65 shown in FIG. 8, a columnar carbide tip 67 (having the same hardness as the excavation tip 51), which is harder than the other part of the flange portion 66, is equally spaced in the circumferential direction on the same circle. It is buried obliquely from the outer peripheral side of the distal end toward the inner peripheral side of the proximal end, thereby preventing the flange portion 66 from being worn.

  The wear suppressing means may be any structure as long as it can suppress wear of the holder 46 during excavation, and is not limited to the structure in which the diameter of the flange portion 66 is expanded. Apart from this, or together with this, Can be used.

  For example, in the conical bit 68 shown in FIG. 9, as a wear suppressing means, the base end side (rear side) of the drilling tip 51 of the bit main body 69 is formed into a truncated cone, and the outer peripheral surface of the bit main body 69 is formed into a conical shape. By making the cross section orthogonal to the rotation center axis (center line) of the bit main body 69 a circular shape whose diameter gradually increases along the rotation center axis, the outer peripheral surface of the bit main body 69 is formed as a continuous surface having no corners. I have.

  Further, in the conical bit 70 shown in FIG. 10, the outer peripheral surface of the bit main body 71 has a conical shape, and a part of the outer peripheral surface is harder than the other part (having the same hardness as the excavation tip 52). A plurality of carbide tips 72 are linearly extended from the distal end to the proximal end, and are attached at equal intervals in the circumferential direction.

  In the conical bit 73 shown in FIG. 11, the outer peripheral surface of the bit main body 74 has a conical shape, and a part of the outer peripheral surface is harder than the other part (having the same hardness as the excavation tip 52). A plurality of carbide tips 75 are attached at equal intervals in the circumferential direction on the same straight line from the distal end to the proximal end.

  Further, in the conical bit 76 shown in FIG. 12, the outer peripheral surface of the bit main body 77 has a plurality of steps (here, three steps) in a conical shape, and is harder than the other parts in the intervening portion (the same as the excavation tip 51). An annular carbide tip 78 (of hardness) is attached at an interval back and forth.

  Further, in the conical bit 79 shown in FIG. 13, the entire part of the outer peripheral surface of the bit main body 80 having a conical shape is formed of a carbide tip that is harder than other parts (having the same hardness as the excavation tip 51). The whole is a drilling tip 81. Note that the drilling tip 51 may be provided on the tip side, and the entire conical outer peripheral surface of the bit body 80 may be covered with a carbide tip different from the drilling tip 51.

  As described above, in the conical bits 68, 70, 73, 76, and 79 shown in FIGS. 9 to 13, the outer peripheral surfaces of the bit main bodies 69, 71, 74, 77, and 80 have a conical shape as wear suppression means. Since the collision of the earth and sand with the holder 46 can be suppressed by the conical bit body portions 69, 71, 74, 77, and 80, the wear of the holder 46 during excavation can be suppressed.

  In particular, in the conical bits 70, 73, 76, 79 shown in FIGS. 10 to 13, the carbide tips 72, 75, which are harder than the other parts on the conical outer peripheral surface of the bit main body 71, 74, 77, 80. Since the portions 78 and 81 are provided entirely or partially, the outer peripheral surfaces of the bit body portions 71, 74, 77 and 80 can be prevented from being worn.

DESCRIPTION OF SYMBOLS 1 Ground improvement apparatus 2 Ground 3 Heavy equipment 4 Prop 5 Excavation equipment 6 Ground improvement material supply mechanism 7 Swivel joint 8 Ground improvement material storage tank 9 Water tank 10 Ground improvement material mixing plant
11 Ground improvement material discharge pump 12 Elevating support
13 Driver 14 Drilling axis
15 Rotary digging section 16 Inner shaft
17 Outer shaft 18 Drive motor
19 reversing transmission 20 drilling head
21 Stirrer blade 22 Drilling blade
23 Drill bit 24 Innermost stirring blade
25 Inside stirring blade 26 Outside stirring blade
27 Inner stirring blade 28 Inner stirring blade
29 Upper part of inner stirring blade 30 Middle part of inner stirring blade
31 Inner stirring blade lower piece 32 Annular body
33 Stirring piece 34 Connecting piece
35 Outer stirring blade body 36 Outer stirring blade upper piece
37 Middle piece of outer stirring blade 38 Lower piece of outer stirring blade
39 Annular body 40 Stirrer
41 Spiral wing 42 Horizontal wing
43 Spiral 44 Step
45 Conical Bit 46 Holder
47 Bit body 48 Mounting shaft
49 Neck 50 Flange
51 Drilling tip 52 Mounting hole
53 Connector 54 Housing recess
55,57 Seal member 56,58 Recess
59,62 Conical bit 60,63 bit body
61,64 Carbide tip 65,68,70,73,76,79 Conical bit
66 Flange 67,72,75,78 Carbide tip
69,71,74,77,80 Bit body 81 Drilling tip

Claims (2)

In a drilling head having a spiral drilling wing whose diameter is expanded upward from the lower end, and a drilling bit is provided on the drilling wing,
In the middle of the excavation wing, a plurality of stepped portions with a stepwise enlarged diameter are formed, and a plurality of excavation bits are arranged in each step, and a plurality of excavation bits are arranged in each step. A drilling head provided on the lower surface of a wing so as to be located between drilling bits in which another drilling bit is arranged . 2. The excavating head according to claim 1 , wherein a plurality of excavating bits provided side by side on the respective step portions are arranged so as to be shifted back and forth on an inner peripheral side and an outer peripheral side of the excavation wing.

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