JP2019039219A - Drilling blade body - Google Patents

Abstract

To provide a drilling bit which can be easily attachable to and detachable from the drilling blade body.SOLUTION: In a drilling blade body in which a drilling bit 23a is mounted attachable and detachable in a holder 45 of a drilling blade, encapsulation members 54-59 are installed between the drilling blade and the drilling bit 23a, and an encapsulation member 60 is installed on a head portion of a fastener 44 to couple the drilling blade and the drilling bit 23a. The fastener 44 is a bolt with a hexagon socket, and its head portion is at the same position as an upper surface of the drilling bit 23a or at a position lower than the upper surface of the drilling bit 23a, and is fastened to a screw portion formed on the drilling blade. Also in the drilling bit 23a, the upper end portion of the blade portion 47 is formed into a convex shape, and the blade portion 47 is formed by arranging two sharp edges 62, 63, and a groove 64 is formed between both upper surfaces of the two sharp edges 62, 63. Further, the drilling bit 23a has a shape in which the tip end of the sharp edge 63 located at the outermost side of the drilling blade is biased outwardly.SELECTED DRAWING: Figure 5

Description

  The present invention relates to an excavation blade body in which an excavation bit is detachably provided on an excavation blade body.

  In construction such as excavation and improvement of the ground, excavation equipment is used to excavate the ground. In this excavation apparatus, an excavation blade body is provided at the tip of a rotary shaft connected to a drive source such as a motor. The excavation blade body is provided with an excavation bit for excavating the ground on an excavation blade body attached to a rotating shaft. Then, in the excavator, the excavation blade body is rotated along with the rotation of the rotation shaft, and the ground is excavated with an excavation bit (see, for example, Patent Document 1).

  The drilling blade provided in this drilling device is generally a welded drilling bit to the drilling blade (welded drilling blade), and the drilling bit can be attached to and detached from the drilling blade using bolts and nuts. (A detachable excavating blade). Although welded drilling blades are less expensive, the detachable drilling blade can be easily replaced when the drilling bit needs to be replaced due to breakage or wear of the drilling bit. The detachable excavation blade has a cost merit than the body.

JP 2002-339680 A

  However, in the conventional detachable excavation blade body, the bolts and nuts that fix the excavation bit to the excavation blade body protrude from the head and the bottom, and therefore, friction such as earth and sand passing through excavation, The bolts and nuts were worn or damaged by the impact, and the drill bit could not be removed from the drill blade.

  Also, in ground improvement work using solidified material, solidified material etc. may enter and solidify between the drilling wing body and the drill bit, bolts and nuts, and can be removed even if hit with a hammer etc. As a result, the excavation bit may not be removed from the excavation blade body.

  Accordingly, in the present invention according to claim 1, in the excavation blade body in which the excavation bit is detachably provided on the excavation blade body, the sealing material is provided between the excavation blade body and the excavation bit.

  Further, in the present invention according to claim 2, in the excavation blade body in which the excavation bit is detachably provided on the excavation blade body, a sealing material is provided on the head of the fastener that fastens the excavation blade body and the excavation bit. I made it.

  Further, in the present invention according to claim 3, in the present invention according to claim 2, the fastener is a hexagon socket head bolt, and the head is at the same position as the upper surface of the excavation bit or at a position lower than the upper surface, It was decided to be fastened to the screw part formed in the excavation blade body.

  Moreover, in this invention which concerns on Claim 4, in the said invention which concerns on any one of the said Claims 1-3, the said excavation bit decided to form the upper end part of a blade part in convex shape.

  Moreover, in this invention which concerns on Claim 5, in this invention which concerns on any one of the said Claims 1-4, the said excavation bit forms a blade part side by side with two sharpened blades, and two pieces It was decided to form a groove above the sharp edge.

  Further, in the present invention according to claim 6, in the present invention according to claim 5, the excavation bit has a shape in which the sharp end of the sharp blade located on the outermost side of the excavation blade body is biased outward. It was to be.

  And in this invention, there exists an effect described below.

  That is, in the present invention, in the excavation blade body in which the excavation blade is detachably provided on the excavation blade body, since the sealing material is provided between the excavation blade body and the excavation bit, Therefore, it is possible to prevent the excavation bit from being easily removed from the excavation blade body, and the excavation bit can be easily replaced.

Further, in the present invention, in the excavation blade body in which the excavation bit body is detachably provided on the excavation blade body, since the sealing material is provided on the head of the fastener that fastens the excavation blade body and the excavation bit, It is possible to prevent earth and sand or a solidified material from entering the gap between the fasteners, and the fasteners can be easily removed.
Accordingly, the excavation bit can be easily detached from the excavation blade body, and therefore exchanging work of the excavation bit can be facilitated.

  In particular, the fastener is a hexagon socket head cap screw, and the head is positioned at the same position as the upper surface of the excavation bit or at a position lower than the upper surface, so that the head of the fastener is worn by dirt, stones, etc. that are moved by excavation. It is possible to prevent wear. Further, since the fastener is directly fastened to the screw portion formed on the excavation blade body, it is possible to prevent the bottom portion of the fastener from being worn or worn. Furthermore, as an additional effect of the screw part formed on the excavation blade body, even if the solidified material or the like enters due to deterioration of the sealing material or the like and the fastener is fixed, along with the forced rotation operation by screw removal, The edge of the fixed portion is cut off, and the fastener can be easily removed with certainty.

  Further, when the upper end portion of the blade portion of the excavation bit is formed in a convex shape, the convex portion becomes a resistance, and earth and sand moved by excavation directly contact the fastener to wear and wear the head. Can be prevented. Further, when removing the excavation bit, the excavation bit can be easily detached from the excavation blade body by hitting the convex portion with a hammer or the like.

  In addition, when the blade portion of the excavation bit is formed by arranging two sharp blades side by side and a groove is formed between the two sharp blades, the earth and sand excavated by the sharp blade are Therefore, it is possible to smoothly pass between the two sharp blades in the upper direction and to discharge well, so that it is possible to prevent a decrease in excavation performance due to adhesion of earth and sand between the sharp blades.

  Furthermore, the two sharp edges of the excavation bit located inside the excavation blade body of the excavation bit are formed in a double-edged shape, but the sharp end of the sharpening blade located on the outermost side of the excavation blade body is a single edge. By using the shape that is biased to the outside, the outermost part can be reliably excavated with the sharp edge of the blade, and the side surface wear caused by the earth and sand of the outermost part coming into contact with the side of the excavation bit. And the like can be prevented.

The side view which shows a ground improvement apparatus. The side view which shows a digging apparatus. FIG. The top view which shows a digging blade body. The top view (a), the right side view (b), the left side view (c), and the sectional view (d) showing the excavation bit.

  Hereinafter, a specific configuration of the excavation blade according to the present invention will be described with reference to the drawings. In the following description, the case where the excavation blade according to the present invention is applied to the excavation apparatus of the ground improvement device will be described, but the present invention is not limited to this, and the excavation blade according to the present invention is applied to other excavation apparatuses. can do.

  As shown in FIGS. 1 to 3, the ground improvement device 1 excavates the ground 2 and stirs and mixes the excavated soil and the ground improvement material (solidification material), thereby improving the strength and properties of the ground 2. To do. In this ground improvement device 1, a support column 4 is erected at the front end of a heavy machine 3, and an excavation device 5 is attached to the support column 4 so as to be movable 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 discharge pump 11 to the ground improvement material mixing plant 10 to improve the ground. The material is configured to be supplied to the excavator 5.

  The excavator 5 has a lifting support 12 attached to the front side of the support column 4 so as to be movable up and down, a driving body 13 is attached to the lifting support 12, and a base end portion of the excavation shaft 14 is vertically extended on the driving body 13. (Upper end part) is attached, and the rotary excavation part 15 is attached to the tip part (lower end part) of the excavation shaft 14. Here, the rotary excavation unit 15 excavates by rotation, and the ground improvement device 1 has a function of stirring and mixing the ground and the ground improvement material in addition to 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 excavation shaft 14 is formed in a double tubular shape by a hollow cylindrical inner shaft 16 and an outer shaft 17 which are coaxially arranged with a rotation center shaft. The excavation shaft 14 protrudes the tip portion of the inner shaft 16 downward from the tip portion of the outer shaft 17. The inner shaft 16 or the outer shaft 17 rotates in a relatively opposite direction by the action of the reverse transmission 19 by driving the drive motor 18.

  The rotary excavation unit 15 has an excavation blade body 20 and a stirring blade 21 attached to the distal end portion (lower end portion) of the excavation shaft 14 in order from the distal end side.

  The excavating blade body 20 has two flat excavating blade bodies 22 attached to the outer peripheral surface of the tip end portion of the inner shaft 16 in a radial direction with an interval of 180 degrees in the circumferential direction, A plurality of excavation bits 23 are detachably attached to the lower part of the wing body 22 at intervals. In the excavation blade body 20, the excavation blade bodies 22 and 22 rotate with the rotation of the inner shaft 16, and excavate the ground 2 with the excavation bit 23. The detailed configuration of the excavation blade 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 thereof, and an outer stirring blade 26 disposed on the outer peripheral side thereof.

  The innermost agitating blade 24 is radially attached to the outer peripheral surface of the outer shaft 17 with two flat innermost agitating blade bodies 27 facing the circumferential direction and spaced outward by 180 degrees. ing.

  The inner stirring blade 25 has two inner stirring blade bodies 28 radially attached to the tip of the inner shaft 16 at an interval of 180 degrees in the circumferential direction. Each inner stirring blade body 28 has an inner stirring blade upper piece 29 extending in an inclined manner toward the outer lower part, an inner stirring blade intermediate piece 30 extending vertically downward, and an outer upper part. The inner stirring blade lower piece 31 extending in an inclined shape is formed in a substantially U shape in a side view in which a midway portion is bulged outward. Each inner stirring blade body 28 has the inner stirring blade lower piece 31 attached to the tip end side of the inner shaft 16, the inner stirring blade upper piece 29 attached to the annular body 32, and the annular body 32 on the outer peripheral surface of the outer shaft 17. It is loosely fitted freely. In addition, each inner stirring blade body 28 has stirring pieces 33, 34, 35 attached to the upper part of the inner stirring blade upper part 29 and the inner part and outer part of the inner stirring blade middle part 30, and the inner stirring blade middle part piece. A connecting piece 36 is attached between 30 and the inner shaft 16.

  The outer stirring blade 26 has three outer stirring blade bodies 37 radially attached to the front end portion of the outer shaft 17 at intervals of 120 degrees in the circumferential direction. Each outer stirring blade body 37 has an outer stirring blade upper piece 38 extending in an inclined manner toward the outer lower portion, an outer stirring blade middle piece 39 extending vertically downward, and an outer upper portion. The outer stirring blade lower piece 40 extending in an inclined shape is formed in a substantially U shape in a side view in which a midway portion is bulged outward. Each outer stirring blade body 37 has an outer stirring blade upper piece 38 attached to the tip end side of the outer shaft 17, an outer stirring blade lower piece 40 attached to the annular body 41, and the annular body 41 on the outer peripheral surface of the inner shaft 16. It is loosely fitted freely. Each outer stirring blade body 37 has stirring pieces 42 and 43 attached to the lower portion of the outer stirring blade upper piece 38 and the inner portion of the outer stirring blade middle piece 39.

  The ground improvement device 1 is configured as described above. The details of the excavating blade body 20 of the excavator 5 that is the main part of the present invention are configured as described below.

  As shown in FIG. 4, the excavation blade body 20 is provided with four excavation bits 23 (23 a to 23 d) detachably on the excavation blade body 22 with fasteners 44. As a result, the excavation blade body 20 can easily replace the excavation bit 23 when the excavation bit 23 is damaged or worn. The excavation bit 23 may be provided directly on the excavation blade body 22, or may be provided via a holder 45 attached to the excavation blade body 22, as shown in FIG. Here, the holder 45 forms an overhanging portion 45b for abutting the side surface of the excavation bit 23 on the side portion of the holding portion 45a for holding the excavation bit 23, and excavates at the rear portion of the holding portion 45a. A step 45c for contacting the rear surface of the bit 23 is formed.

  The excavation bits 23a to 23d all have the same configuration. However, as will be described later, only the excavation bit 23d located on the outermost side of the excavation blade body 22 has a cutting edge shape compared to the other inner excavation bits 23a to 23c. Is different.

  As shown in FIG. 5, the excavation bit 23 includes a connecting portion 46 straddling the front end portion (holding portion 45a of the holder 45) of the excavating blade body 22 from the front side, and a blade formed on the front side of the connecting portion 46 Part 47 is formed.

  The connecting portion 46 is provided with an upper piece 48 and a lower piece 49 that sandwich the front end portion (holding portion 45a of the holder 45) of the excavating blade body 22, and the side cross section is formed in a substantially U shape. Steps 50 are formed in the upper piece 48 and the lower piece 49, respectively. The upper piece 48 is formed with a stepped cylindrical hole 51 for receiving a head of a hexagon socket head bolt as the fastener 44. On the other hand, the lower piece 49 is formed with a threaded portion 52 in which a female screw to be screwed onto a male screw of a hexagon socket head bolt as the fastener 44 is formed. The through hole 51 of the upper piece 48 is such that the head of the fastener 44 is at the same position as the upper surface of the excavation bit 23 (upper piece 48) or at a position lower than the upper surface. The screw portion 52 may be a through hole or a closed hole. The excavation blade body 22 (holder 45) is formed with a through-hole 53 through which the fastener 44 is inserted.

  The excavation bit 23 is inserted into the front end portion (holding portion 45a of the holder 45) formed at a predetermined position of the excavation blade body 22 from the front side to insert the front end portion (holding portion 45a of the holder 45) into the upper piece 48. And the lower piece 49, and in that state, the fastener 44 is inserted into the through holes 51, 52, 53 from the upper side of the upper piece 48, and the fastener 44 is screwed to the lower piece 49, thereby excavating blades. Can be attached to the body 22. In addition, by performing the reverse operation, even if the solidifying material or the like enters due to deterioration of the sealing material or the like and the fastener 44 is fixed, a forced rotation operation accompanying the screw part removal occurs and is fixed. The cutting edge is cut off, the fastener 44 can be easily removed, and the excavation bit 23 can be removed from the excavation blade body 22.

  Here, the excavation bit 23 is substantially connected to the left side surface of the connecting portion 46 (the inner side surface (the contact surface with the overhanging portion 45b of the holder 45) when the excavation bit 23 is attached to the excavation blade body 22). A letter-shaped sealing material 54 is attached in a replaceable manner, and the right side surface of the connecting portion (the outer side surface in the state where the excavation bit 23 is attached to the excavation blade body 22 (the contact surface of the holder 45 with the holding portion 45a)) ), And a rear end surface of the connecting portion 46 (rear end surfaces of the upper piece 48 and the lower piece 49 (contact surface with the step 45c of the holder 45)). In addition, the rectangular flat plate-shaped sealing materials 56 to 59 are attached in a replaceable manner. The left side sealing material 54 is provided at the upper end (outer end) of the upper piece 48 and the lower end (outer end) of the lower piece 49 so as to come into contact with the overhanging portion 45b of the holder 45. The sealing material 55 is provided at the lower end portion (inner end portion) of the upper piece 48 and the upper end portion (inner end portion) of the lower piece 49 so as to contact the holding portion 45a of the holder 45. As the sealing materials 54 to 59, a resin or the like molded into a predetermined shape may be used, or the resin or the like may be applied or filled when the excavation bit 23 is attached.

  As a result, the excavation bit 23 is provided with the sealing materials 54 to 59 in the portions that are in contact with the excavation blade body 22 in a state of being mounted on the excavation blade body 22. As described above, by providing the sealing materials 54 to 59 between the excavation blade body 22 and the excavation bit 23, it is possible to prevent intrusion of earth and sand during ground excavation and improvement material during ground improvement.

  When the excavation bit 23 is attached to the excavation blade body 22, the gap between the through hole 51 of the upper piece 48 and the head of the fastener 44, the through hole 53 of the lower piece 49, and the lower end of the fastener 44 Sealing materials 60 and 61 are provided in the gap. The sealing materials 60 and 61 may be combined with an O-ring or the like, or a resin or the like molded into a predetermined shape, and the resin or the like may be applied or filled after the drill bit 23 is attached. Alternatively, the front surface of the outer periphery of the fastener 44 may be coated with resin or the like. The sealing material 61 is necessary when the screw portion 52 provided on the lower piece 49 is a through hole, and is not necessary when the screw portion 52 is a blocking hole.

  As a result, the excavation bit 23 is provided with the sealing materials 60 and 61 in the portion where the fastener 44 is exposed when the excavation bit 23 is attached to the excavation blade body 22 with the fastener 44. In this way, by providing the sealing materials 60 and 61 in the portion where the fastener 44 is exposed, it is possible to prevent intrusion of earth and sand during ground excavation and improvement material during ground improvement. Removal is easy.

  The blade portion 47 of the excavation bit 23 is formed with two sharp blades 62, 63 arranged side by side at the tip, forming a groove 64 above the two sharp blades 62, 63, and upper at the upper end. A convex convex portion 65 that protrudes upward from the upper surface of the piece 48 is formed.

  Here, as shown in FIG. 4, the inner excavation bits 23a to 23c form two sharp blades 62 and 63 having the same shape (the same blade edge angle), whereas the excavation blade body 22 is formed. In the excavation bit 23d located on the outermost side, the sharpened end of the sharpened blade 63 on the outer side is biased outward from the center.

  As described above, the excavation blade body 20 provided in the excavation apparatus 1 has a configuration in which the sealing materials 54 to 59 are provided between the excavation blade body 22 and the excavation bit 23.

  Therefore, in the excavating blade body 20 having the above-described configuration, it is possible to prevent intrusion of earth and sand or solidified material between the excavating blade body 22 and the excavating bit 23. The excavation bit 23 can be easily replaced.

  Further, the excavation blade body 20 has a configuration in which a sealing material 60 is provided on the head of a fastener 44 that fastens the excavation blade body 22 and the excavation bit 23.

  Therefore, in the excavating blade body 20 having the above-described configuration, it is possible to prevent earth and sand, a solidified material, and the like from entering the fastener 44, so that the excavating bit 23 can be easily removed from the excavating blade body 22 as well. Therefore, excavation bit replacement work can be facilitated.

  Further, in the excavation blade body 20, a hexagon socket head cap screw is used as the fastener 44, and the head thereof is located at the same position as the upper surface of the excavation bit 23 or lower than the upper surface, and is formed on the excavation blade body 22 (holder 45). It is set as the structure fastened by the screw part which carried out.

  Therefore, in the excavating blade body 20 having the above-described configuration, it is possible to prevent the head and bottom of the fastener 44 from being worn or worn by earth, sand, stone, or the like that is moved by excavation. In addition, since the fastener 44 is directly fastened to the screw portion formed on the excavation blade body 22, even if a solidifying material or the like enters due to deterioration of the sealing material or the like and the fastener is fixed, the forced removal by screw removal is forced. With the rotation operation, the fixed portion is cut off, and the fastener 44 can be easily removed with certainty.

  Further, the excavation blade body 20 has a configuration in which the upper end portion of the blade portion 47 of the excavation bit 23 is formed in a convex shape.

  Therefore, in the excavating blade body 20 having the above-described configuration, it is possible to prevent the sand 65 or the like that moves due to excavation directly coming into contact with the fastener 44 due to the convex portion 65 being a resistance, so that the head is worn or worn. Further, when the excavation bit 23 is removed, the excavation bit 23 can be easily detached from the excavation blade body 22 by hitting the convex portion 65 with a hammer or the like.

  Further, the excavation blade body 20 has a configuration in which a blade portion 47 of the excavation bit 23 is formed by arranging two sharp blades 62 and 63 side by side and a groove 64 is formed between the two sharp blades 62 and 63. It has become.

  Therefore, in the excavating blade body 20 having the above-described configuration, the earth and sand excavated by the sharp blades 62 and 63 smoothly pass between the two sharp blades 62 and 63 through the groove 64 and are discharged well. Therefore, it is possible to prevent a decrease in excavation performance due to adhesion of earth and sand between the sharp edges 62 and 63.

  Further, the excavating blade body 20 has a shape in which the sharp end of the sharpening blade 63 outside the excavating bit 23d located on the outermost side of the excavating blade body 22 among the excavating bits 23a to 23d is biased outward. It is composed.

  Therefore, in the excavation blade body 20 having the above-described configuration, the outermost portion can be reliably excavated with the sharp edge portion of the blade, and the side surface wear caused by the earth and sand of the outermost portion coming into contact with the side surface of the excavation bit, etc. Prevention is also possible.

DESCRIPTION OF SYMBOLS 1 Ground improvement device 2 Ground 3 Heavy machine 4 Prop 5 Excavation device 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 Lifting support
13 Drive 14 Drilling shaft
15 Rotary excavation 16 Inner shaft
17 Outer shaft 18 Drive motor
19 Reverse transmission 20 Drilling blade
21 Stirring blade 22 Drilling blade
23 Drilling bit 24 Innermost stirring blade
25 Inner stirring blade 26 Outer stirring blade
27 Inner stirring blade 28 Inner stirring blade
29 Inner stirring blade upper piece 30 Inner stirring blade middle piece
31 Inner stirring blade lower piece 32 Annulus
33,34,35 Stirring piece 36 Connecting piece
37 Outer stirring blade body 38 Outer stirring blade upper piece
39 Middle part of outer stirring blade 40 Lower part of outer stirring blade
41 Toroid 42,43 Stirring piece
44 Fastener 45 Holder
45a Holding part 45b Overhang part
45c Step 46 Connection
47 Blade 48 Upper piece
49 Lower piece 50 steps
51,53 Through hole 52 Threaded part
54 to 61 Sealing material 62,63 Sharp edge
64 groove 65 convex

Accordingly, in the present invention according to claim 1, in the excavation blade body in which the excavation bit is detachably provided on the excavation blade body, the excavation bit is formed on the connection portion connected to the excavation blade body and on the front side of the connection portion. A projecting convex portion that is provided with a sealing material between the excavating blade body and the connecting portion of the excavating bit and protrudes above the upper surface of the connecting portion above the upper surface of the connecting portion. It was Rukoto to form.

According to a second aspect of the present invention, in the excavation blade body in which the excavation bit is detachably provided on the excavation blade body, the excavation bit is formed on the connection portion connected to the excavation blade body and on the front side of the connection portion. Provided with a sealing material on the head of a fastener that fastens the excavating blade body and the connecting portion of the excavating bit , and protrudes above the upper surface of the connecting portion above the upper surface of the connecting portion. convex convex portions was Rukoto form a.

Moreover, in this invention which concerns on Claim 3, in this invention which concerns on the said Claim 2, the said fastener is a hex socket head cap screw, and a head is the same position as the upper surface of the connection part of an excavation bit , or is lower than an upper surface It was decided to be fastened to the screw part formed on the excavation blade body.

Moreover, in this invention which concerns on Claim 4 , in this invention which concerns on any one of the said Claims 1-3 , the said excavation bit forms a blade part side by side with two sharpened blades, and two pieces It was decided to form a groove above the sharp edge.

Further, in the present invention according to claim 5 , in the present invention according to claim 4 , the excavation bit has a shape in which the sharp end of the sharp blade located on the outermost side of the excavation blade body is biased outward. It was to be.

Claims (6)

In the excavation blade body in which the excavation bit is detachably provided on the excavation blade body,
A drilling blade body comprising a sealing material provided between a drilling blade body and a drilling bit. In the excavation blade body in which the excavation bit is detachably provided on the excavation blade body,
A drilling blade body comprising a sealing member provided at a head portion of a fastener for fastening a drilling blade body and a drilling bit.   3. The fastener according to claim 2, wherein the fastener is a hexagon socket head bolt, and the head is positioned at the same position as or lower than the upper surface of the excavation bit, and is fastened to a screw portion formed on the excavation blade body. The drilling blade described.   The excavation blade body according to any one of claims 1 to 3, wherein the excavation bit has an upper end portion formed in a convex shape.   The said excavation bit formed the blade part along with two sharp edges, and formed the groove | channel between the two sharp edges, The claim 1 characterized by the above-mentioned. Drilling blade body.   The excavation blade body according to claim 5, wherein the excavation bit has a shape in which a sharp end of the sharp edge blade located on the outermost side of the excavation blade body is biased outward.

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