JP2000291365A - Excavating bit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an excavating bit capable of surely and continuously excavating rock layers ranging from soft layer to moderately hard layer and the buried materials formed of reinforced concrete and steel materials or steel materials and plain concrete. SOLUTION: An excavating bit 1 mounted at the tip of a cutter ring rotated about an axis is so formed that a plurality of tips 9... harder than a bit main body 2 are planted in the bit main body 2 having, at its tip, a tip surface 3a formed in hill shape along the rotating direction of the cutter ring by projecting its tip end so that it forms a hill shape along the tip surface 3a of the bit main body 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drill bit which is attached to the tip of a cutter ring which is rotated around an axis and is used for drilling work. Alternatively, the present invention relates to a drill bit suitable for use when continuously excavating a buried object such as steel material and unreinforced concrete.

[0002]

2. Description of the Related Art A drill bit attached to the tip of such a cutter is disclosed, for example, in JP-A-53-82.
Japanese Patent Application Laid-Open No. 601 proposes that a bit body is formed by surrounding an alloy matrix made of a soft alloy material around a cemented carbide shaft-like chip by welding overlay, casting, powder metallurgy, or the like. According to the above publication, the drill bit is attached to the tip of a cylindrical cutter ring for rock core (core) extraction, and the cutter bit is advanced in the axial direction while rotating the cutter ring around its axis. Used by rock boring. In this excavation bit, the tip is disposed parallel to the axis of the cutter ring, and the tip of the tip and the tip face of the bit body have a cross section including the axis in the circumferential direction of the cutter ring. Over the entire surface.

[0003]

By the way, in recent years, an excavation method for directly connecting a branch hole excavated by a shield excavator to a buried object buried in the ground such as an existing sewer main shield tunnel, for example. Has been studied. In such an excavation method, after excavating a branch hole to a position close to the buried object by a shield excavator, the cutter ring with the excavation bit as described above is rotated from the tip of the shield excavator. It has been considered that the branch holes are penetrated and connected to the buried object by moving forward while moving forward.

However, in such an excavation method,
Excavation of the medium hard rock layer from the soft layer left between the branch hole and the buried object, and excavation of the wall of the buried object such as the shield tunnel made of reinforced concrete or steel, or steel and unreinforced concrete Is performed continuously,
In the above-described excavation bit, the excavation of the buried object wall is performed after the tip of the tip is worn over the entire end surface of the bit body by excavation of the rock layer. For this reason, it is unavoidable that the excavation efficiency is significantly deteriorated in excavating the buried object, and in some cases, the connection of the branch hole itself may be difficult.

The present invention has been made in view of such circumstances, and in particular, excavation of a soft rock layer to a medium hard rock layer as described above, and burial made of reinforced concrete or steel, or steel and unreinforced concrete, etc. An object of the present invention is to provide a drill bit that can reliably and continuously excavate an object.

[0006]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems and to achieve such an object, the present invention relates to a cutting bit attached to a tip of a cutter ring which is rotated around an axis. A plurality of chips harder than the bit body are provided on a bit body having a mountain-shaped tip surface that is convex toward the tip side along the rotation direction of the cutter. It is characterized by being planted so as to form a mountain shape.

Therefore, in such a drill bit, the excavation is performed exclusively from the soft layer to the medium hard rock layer by the tip implanted around the top of the tip surface of the mountain-shaped bit body projecting toward the tip side. On the other hand, when excavating a buried object such as the wall of the existing shield tunnel, the tip and the bit body tip surface around the top are worn, and the wear planted at the foot of the mountain shape is worn. Unexposed chips are sequentially involved in the excavation, and the excavation efficiency is ensured. Therefore, it is possible to reliably and continuously excavate such a buried object.

[0008] Here, it is desirable that the angle of inclination of the mountain-shaped slope formed by the tip end surface of the bit body with respect to a plane perpendicular to the axis is set in the range of 3 ° to 12 °. This is because if the inclination angle is smaller than 3 °, the mountain-shaped slope formed by the tip surface of the bit body becomes too gentle, and depending on the amount of feed to the tip side of the cutter, the soft to medium hard rock layer In the excavation, there is a possibility that the tip at the foot of the chevron may be worn due to the excavation. Conversely, if the inclination angle is larger than 12 °, the slope of the chevron will be too steep and buried. Excavation of the object wears the tip on the top side and the tip on the foot side becomes involved in excavation,
This is because the excavation efficiency during this time may be impaired.

On the other hand, in the excavation by cutting with the excavation bit attached to the extremity, the extremity surface of the excavation bit is worn by the excavation bit and the excavation bit is formed by the excavation bit. The sliding contact with the peripheral wall surface of the annular groove also wears the side surface of the bit body. Moreover, since the wear of the side surface proceeds from the tip side of the bit body, the bit body becomes tapered wedge-shaped in a cross section including the axis of the cutter ring with excavation, and the cutter ring with such a drill bit is rotated. When trying to excavate while moving forward,
Since a wedge is driven into the rock layer or the buried object, frictional resistance increases, the rotational torque of the cutter increases, and it becomes difficult to discharge chips generated during excavation.

Therefore, in order to avoid such a problem, the side surface of the bit body facing the inner peripheral side or the outer peripheral side of the cutter ring is formed into an inclined surface which gradually retreats toward the rear end side. It is desirable to form it, and this forms a gap between the peripheral wall surface of the annular groove and the side surface of the bit body, so that an increase in frictional resistance can be suppressed and chips can be easily removed through this gap. Can be discharged.

When the side surface of the bit body is retracted in this way, it is desirable that the retract angle be set in the range of 2 ° to 12 °. The gap is too small, and it may be difficult to sufficiently suppress frictional resistance and smoothly discharge chips.On the other hand, if the retreat angle is larger than 12 °, the bit body retreats. The intersection angle between the side surface and the tip surface becomes small, resulting in chipping, or the chip cannot be implanted to a sufficient depth on the side surface parallel to the axis of the cutter, even if the chip is implanted along the side surface. Even if it is provided, since the intersection angle between the tip end surface and the peripheral surface on the side surface side becomes small due to wear, there is a possibility that chipping may still occur.

Further, when the side surface of the bit main body is worn as described above, there is a problem that the tip implanted in the bit main body may fall off. Therefore, in order to solve such a problem, it is desirable to embed an auxiliary tip harder than the bit main body on the side surface of the bit main body facing the inner peripheral side or the outer peripheral side of the cutter ring. With this configuration, the side surface of the bit body is prevented from being worn in a wedge shape by the auxiliary tip, so that an increase in frictional resistance can be suppressed and good chip discharge performance can be maintained. Becomes possible.

However, in this auxiliary chip, it is desirable that the hardness is set to a range equal to or higher than the hardness of the above-mentioned chip by HRA8 lower than the above-mentioned chip. While the wear of the side surface of the bit body may not be reliably prevented, if the hardness of the auxiliary tip is higher than that of the tip, the tip surface or the tip of the bit body on the side surface in which the auxiliary tip is embedded is provided. Wear of the buried object may be suppressed, and the tip at the foot of the mountain may not be reliably involved in the excavation when excavating the buried object.

[0014]

1 to 3 show a drill bit 1 according to a first embodiment of the present invention. The drill bit 1 of the present embodiment has a bit body 2 formed of a soft alloy such as brass or mild steel, and the tip side of the bit body 2 has a top view in a plan view as viewed from the tip side. As shown in FIG. 1, a substantially rectangular blade portion 3 is formed, and the rear end side of the bit main body 2 has a rectangular width direction formed by the distal end surface 3a of the blade portion 3 in the plan view (FIG. 1). (The vertical direction in FIG. 3. The horizontal direction in FIG. 3.)
The excavating bit 1 is formed as a mounting portion 6 for mounting the excavating bit 1 to a holder 5 joined to the tip of a cutter ring 4 as shown in FIG.

Here, the mounting portion 6 has a substantially equilateral trapezoidal shape in a plan view at a portion on the side where the mounting portion 6 is shifted from the blade portion 3 in the width direction (upper side in FIG. 1). It is formed so as to form a pair of mounting portions 6a, 6a which approach each other toward the shifted side, and which penetrate the mounting portion 6 perpendicularly to the bottom surface 6b. The holes 7, 7 are formed in parallel with each other so that the blades 3 are arranged in the longitudinal direction (the left-right direction in FIGS. 1 and 2) of the rectangle formed in plan view. A pair of flanges 8 are formed on both side surfaces of the mounting portion 6 facing the longitudinal direction so as to protrude from the side surface.

On the other hand, a plurality of chips 9 having a cylindrical shaft shape are implanted in the blade portion 3 with their tips protruding from the tip surface 3 a of the blade portion 3. These chips 9 are made of a hard material such as cemented carbide or ceramics.
The hardness of the bit body 2 is set to be higher than that of the bit body 2 by about HS 50 to 80.
Are mounted perpendicular to each other, ie parallel to one another. In addition, these chips 9... Form a plurality of rows (seven rows in the present embodiment) arranged at equal intervals in the longitudinal direction on the distal end surface 3 a of the blade portion 3 in the plan view. Are arranged in a zigzag pattern so as to be equidistant in the width direction, and at least in a plurality of rows arranged at the central portion in the longitudinal direction, at least one row is arranged in the width direction. Between the adjacent chips 9, 9, the chips 9 in the row adjacent to this one row
Are arranged so as to overlap the chips 9 in the one row in the width direction.

The distal end surface 3a of the blade portion 3 is formed symmetrically in the longitudinal direction so as to form a mountain shape that gradually projects toward the distal end side from both ends to the central portion. Are slightly protruded from the front end surface by an equal amount, and are arranged so as to form a mountain shape along the mountain shape formed by the front end surface 3a. However, in the present embodiment, the tip surface 3a is formed in a portion of the row formed by the chips 9.
Is formed so as to be a flat surface parallel to the bottom surface 6b of the mounting portion 6, and the foot portion of the mountain-shaped tip surface 3a from the flat surface toward the rear end side toward the both ends in the longitudinal direction is constant. It is formed so as to be inclined at an inclination angle θ, so that the front end surface 3a has the shape of a trapezoidal mountain having the flat surface as the top. Further, in the present embodiment, the inclination angle θ is set in a range of 3 ° to 12 °. In the present embodiment, the side surface 3 b of the blade portion 3 on the side shifted from the mounting portion 6 is formed in a direction perpendicular to the bottom surface 6 b of the mounting portion 6.

The holder 5 to which the drill bit 1 is attached is formed of a thicker, substantially flat plate made of steel or the like having a higher hardness than the bit body 2 and has a tip portion of the cylindrical cutter ring 4. In the plurality of recesses 4a formed at equal intervals in the circumferential direction, the front end surface 5a is directed toward the front end side, and one of the side surfaces 5b and 5c is directed toward the inner peripheral side of the cutter ring 4 and the other is the outer peripheral side. Mounted for. Here, the holder 5 is formed with a mounting recess 10 into which the mounting portion 6 is inserted so as to open to the front end surface 5a and penetrate between the side surfaces 5b and 5c. The mounting recess 10 is formed with wall surfaces 10a, 10a approaching each other toward the side surface 5b at an included angle equal to the angle formed by the side surfaces 6a, 6a of the mounting portion 6 of the drill bit 1, and has a bottom surface 10b.
On the other hand, mounting screw holes 11, 11 are formed so as to be coaxial with the mounting holes 7, 7 with the side surfaces 6a, 6a abutting on the wall surfaces 10a, 10a. On the side, recesses 12, 12 into which the flanges 8, 8 of the mounting portion 6 of the drill bit 1 can be fitted are formed on the bottom surface 10 b side.

Thus, the holder 5 constructed as described above is used.
The mounting bit 6 is inserted into the mounting recess 10 with the side surfaces 6a and 6a facing forward from the side surface 5c of the holder 5 and the side surfaces 6a and 6a are attached to the wall surfaces 10a and 10a, the bottom surface 6b is brought into close contact with the bottom surface 10b of the mounting concave portion 10, and the flange portions 8, 8 are fitted into the concave portions 12, 12, and are inserted through the mounting holes 7, 7, not shown. By screwing a pair of mounting bolts into the mounting screw holes 11, 11, the blade 3 is mounted so as to protrude from the tip end surface 5 a of the holder 5. Therefore, this drill bit 1 has its blade 3
Are attached along the circumferential direction of the cutter ring 4 and the width direction is directed toward the radial direction of the cutter ring 4.
The flat surface on the top of the tip surface 3a is disposed in a direction perpendicular to the axis of the cutter ring 4.

Further, in the state of being fitted and inserted into the mounting recess 10 as described above, the mounting portion 6 of the drill bit 1 is mounted.
The side surface 6c located between the side surfaces 6a and 6a and the side surface 6d opposite to the side surface 6c
And the side surface 5c are flush with each other. Therefore, as described above, the mounting portion 6 and the blade portion 3 are staggered, so that the blade portion 3 of the drill bit 1 The side surface 3b is the side surface 5c of the holder 5 in the plan view.
Is provided so as to project one step in the width direction with respect to the above.
On the other hand, the holders 5 attached to the plurality of recesses 4a of the cutter ring 4 are arranged such that the holders 5, 5 adjacent in the circumferential direction of the cutter ring 4 have side surfaces 5b, 5c.
Are arranged so as to be alternately directed to the inner peripheral side and the outer peripheral side of the cutter ring 4. Therefore, the side surfaces 3 b of the cutting portion 3 of the cutting bits 1. 4 are arranged so as to protrude alternately on the inner peripheral side and the outer peripheral side. However, on the distal end surfaces 3a of the blade portions 3 of the excavating bits 1 that alternately protrude from the inner and outer circumferences, the tips 9 of each other accompanying the rotation of the cutter ring 4 are formed.
Are overlapped at the radial center of the cutter ring 4.

However, the excavation bits 1 attached to the tip of the cutter ring 4 via the holder 5 in this manner.
As the cutter ring 2 is advanced in the axial direction while being rotated in the circumferential direction around the central axis from the tip of the shield excavator as described above, the cutter portion 2 is moved from the soft layer by the blade portion 3 as described above. It is used to continuously excavate a medium hard rock layer and excavate a buried object such as an existing shield tunnel made of reinforced concrete or steel, or steel and unreinforced concrete. Accordingly, the distal end surface 3a of the blade portion 3 of the bit body 2 has a mountain shape that protrudes toward the distal end along the rotation direction of the cutter ring 4, and the tips 9 implanted in the blade portion 3 are formed. However, since the tip of the drill bit 1 is protruded in the direction of rotation along the tip surface 3a so as to form a mountain shape in the rotation direction and is rotated, the drill bit 1 having the above-described configuration has a relatively soft rock layer from a soft layer to a medium hard rock layer. When excavating the rocks, the chips 9... Planted at the top of the mountain shape projecting to the most distal end side are exclusively used for excavation, and the other chips 9 are worn by excavation of this rock layer. Can be avoided.

On the other hand, when these excavating bits 1... Reach the existing shield tunnel or the like and excavate a buried object such as reinforced concrete or steel, or steel and unreinforced concrete, the excavating bits 1 project to the most distal end side. As the chips 9 in the row implanted at the top of the chevron wear, the chips 9 in the row adjacent to the row in the longitudinal direction become the same height and the chips 9 in the top row wear out. When the chips 9 are worn out, the chips 9 in the row adjacent to the longitudinal direction are subjected to excavation. That is, according to the excavating bit 1 having the above-described configuration, the tip surface 3a of the blade portion 3 of the bit main body 2 is formed by the wear of the tips 9 with respect to the above-described buried object. The chips 9 implanted at the foot of the mountain form are sequentially involved in the excavation, so that the excavation efficiency is not impaired, but rather, the excavation efficiency can be ensured as the wear increases. Therefore, the excavation of the soft rock layer to the medium hard rock layer and the excavation of the buried object formed of reinforced concrete or steel, or steel and unreinforced concrete in the above-described excavation method can be reliably and continuously performed. Becomes

Here, in the present embodiment, the foot portion of the mountain shape formed by the tip end surface 3a of the blade portion 3 of the bit main body 2 is formed so as to be inclined at a constant inclination angle θ.
Is set to be in the range of 3 ° to 12 °. However, if the inclination angle θ is smaller than 3 °, the mountain shape formed by the front end face 3a becomes too smooth, so that the angle is formed along the front end face 3a. If the steps of the tips 9 arranged in the mountain shape are too small and the feed amount to the tip side of the cutter 4 is large, the excavation of the soft rock from the medium hard rock layer will cause The chips 9 may be worn by excavation. On the other hand, on the contrary, the inclination angle θ is 12 °
When the angle is larger than the height, the inclination of the mountain shape formed by the distal end face 3a becomes too steep, so that the step of the chips 9 arranged along the distal end face also increases, and the top of the mountain shape is increased. The interval between the tip 9 disposed on the side and the tip 9 on the foot side involved in excavation becomes too long, and it may not be possible to expect improvement in excavation efficiency during this time. Therefore, it is desirable that the inclination angle θ be set in the range of 3 ° to 12 ° as in the present embodiment.

In the present embodiment, the tip surface 3a of the blade portion 3 of the bit body 2 is formed in a mountain shape inclined at a constant inclination angle θ, as described above. The inclination angle θ may be changed by, for example, forming a cylindrical surface that is convex toward the distal end side in the rotation direction of No. 4. In this embodiment, the rows of the chips 9 are arranged on the flat surface formed on the mountain-shaped top formed by the tip surface 3a. However, the excavation efficiency from the soft layer to the medium hard rock layer is improved. For this purpose, two or more rows of chips 9 may be arranged on this flat surface. Further, in the present embodiment, the above-mentioned distal end surface 3a is
The cutter ring 4 is formed so as to form a single chevron that retreats after protruding toward the distal end side in a symmetrical shape along the rotation direction of the cutter ring 4. Alternatively, it may be located at a position deviated backward in the rotation direction, or two or more chevron shapes may be formed on the tip end surface 3a.

Furthermore, in the present embodiment, the tip 9 is harder than the bit body 2, and the wear of the tip end surface 3a of the bit body 2 is more likely to be promoted than the wear of the tip 9 due to excavation. Excavation efficiency can be reliably ensured without the tip 9 being buried in the tip surface 3a, and the chip 9 can be easily discharged because the tip 9 has a space between the tips 9 due to wear of the tip surface 3a. Can be However, if the difference in hardness between the tip 9 and the bit body 2 is too small, such an effect is not sufficient. Conversely, if the difference in hardness is too large, the abrasion of the bit body 2 becomes remarkable and the tip 9 falls off. It is not desirable because there is a possibility that it may go. For this reason, the hardness difference of the bit body 2 with respect to the chip 9 is desirably set in the range of HS50 to HS80 as in the present embodiment.

On the other hand, in the present embodiment, the cutting portion 3 and the mounting portion 6 of the bit main body 2 are formed so as to be shifted from each other. The side surfaces 3b are alternately projected to the inner peripheral side and the outer peripheral side,
Also, they are attached so that the rotation trajectories of the tips 9 on the distal end face 3a overlap. For this reason, in the cutter ring 4 equipped with the drill bit 1 of the above-described embodiment, while reducing the load acting on the individual drill bit 1 and promoting the extension of the life thereof, the thickness of the cutter ring 4 is not less than the thickness. Excavation width can be ensured, and it is possible to prevent a situation in which the inner and outer peripheral surfaces of the cutter ring 4 are in sliding contact with the annular groove formed by the excavation bits 1 and the rotational torque of the cutter ring 4 increases. In addition, the blade 3
Is projected to the inner and outer peripheral sides of the cutter ring 4, an excavation load acts on the bit body 2 on the side opposite to the side where the blade portion 3 protrudes. On the other hand, in the present embodiment,
Side surfaces 6a, 6a approaching each other toward the side on which the excavation load acts are formed in the mounting portion 6, and these side surfaces 6a, 6a are brought into contact with the wall surfaces 10a, 10a of the holder 5 so that the bit body is formed. 2 is mounted, it is possible to secure sufficient mounting rigidity even for such excavation load.

Next, FIG. 5 shows a second embodiment of the present invention, in which the same reference numerals are assigned to parts common to the first embodiment, and description thereof will be omitted. That is, in the second embodiment, the side face 3 b of the bit body 2 of the cutting bit 21 shifted from the mounting portion 6 of the blade portion 3, that is, the cutting bit 21 is attached to the cutting ring 4. A side surface 3b of the bit body 2 protruding toward the inner peripheral side or the outer peripheral side of the cutter ring 4 in a state where the cutter ring 4 is attached to the front end is gradually inclined in the width direction from the front end surface 3a toward the rear end. The receding angle α at which the side surface 3b is inclined while receding is 2 ° to 1 ° in the present embodiment.
It is set in the range of 2 °. In the present embodiment,
As the side surface 3b is inclined backward, the tip 9 implanted in the blade portion 3 also has the most side surface 3b.
The tip 9 implanted on the b side is tilted at an angle equal to the receding angle α, and the next chip 9 in the same row as the tip 9 is tilted at a tilt angle substantially half the receding angle α. I have.

However, in the drilling bit 21 configured as described above, in the cutter ring 4 on which the drilling bit 21 is mounted, the peripheral wall surface of the annular groove formed by the drilling bit 21 and the bit facing the peripheral wall surface. A gap gradually increasing toward the rear end side is defined between the side surface 3b of the main body 2 and the frictional resistance due to the side surface 3b slidingly contacting the peripheral wall surface can be reduced. Thus, the rotational torque of the cutter ring 4 can be further reduced, and chips generated during excavation can be easily discharged through the gap. Moreover, in the present embodiment, since the chips 9 on the inclined side surface 3b are implanted so as to recede in accordance with the inclination of the side surface 3b, the side surface 3b of the blade portion 3 is excavated.
Even if abrasion occurs on the side, when the side surface of the hard tip 9 is exposed, the progress of the abrasion can be suppressed and the gap can be secured, so that the frictional resistance can be reduced for a longer period of time. In addition, it is possible to achieve good chip dischargeability.

In this embodiment, the receding angle α of the side surface 3b is set in the range of 2 ° to 12 °. This is because the inclination of the side surface 3b decreases as the receding angle α falls below 2 °. If the diameter is too small, the gap between the peripheral wall surface of the annular groove formed by the blade portion 3 also becomes small, and the frictional resistance between the peripheral wall surface and the side surface 3b cannot be sufficiently suppressed, or good. This is because there is a possibility that the dischargeability of fine chips may be impaired. On the other hand, if the retreat angle α is greater than 12 °, the intersection angle between the tip surface 3a of the blade portion 3 and the side surface 3b becomes too small,
This intersection may be easily damaged, the chips 9 cannot be vertically implanted on the bottom surface 6b of the bit body 2 as in the first embodiment, or the chips 9 may not extend along the side surfaces 3b as in the present embodiment. Even if the tip 9 is tilted backward, the intersection angle between the tip end surface of the tip 9 and the peripheral surface on the side surface 3b side becomes small, so that the chip 9 may still be damaged. For this reason, the receding angle α is 2 ° to 12 ° as in the present embodiment.
It is desirable to set the angle in the range of °.

FIGS. 6 and 7 show a third embodiment of the present invention. In the third embodiment, the cutting bit 31 is attached to the cutter ring 4. The cutting portion 3 of the bit body 2 protruding toward the inner peripheral side or the outer peripheral side of the cutter ring 4
Are characterized in that auxiliary chips 32... Harder than the bit main body 2 are embedded in the side surfaces 3b of the. Here, the auxiliary chips 32 are formed in a shaft shape having a substantially equilateral trapezoidal cross section, and are spaced apart from the side surface 3b in a row of the chips 9 arranged in a staggered manner. The bottom surface 6b of the bit body 2
And the side of the isosceles trapezoid that is narrower is the side 3
It is planted so as to face the side b and at the same position as the tip 9 on the side surface 3b side in the width direction or on the side surface 3b side. Also, this auxiliary tip 3
The hardness of No. 2 is set to a range approximately equal to the hardness of the chip 9 or a hardness HRA8 lower than the hardness of the chip 9. In the third embodiment, the side surfaces 3b and the chips 9 are arranged in a direction perpendicular to the bottom surface 6b of the bit body 2 as in the first embodiment.

However, in the third embodiment configured as described above, when the side surface 3b wears due to the sliding contact with the peripheral wall surface of the annular groove formed by the blade portion 3 as described above, the side surface 3b Auxiliary tip 32 planted on the side
Are exposed and further wear of the blade portion 3 is suppressed, so that the side surface 3b is prevented from being worn in a tapered wedge shape by this wear, thereby suppressing an increase in frictional resistance and deterioration of chip dischargeability. In addition to this, it is possible to prevent a situation in which the wear is promoted and the chip 9 falls off. In addition, in the present embodiment, in particular, the auxiliary tip 32 is formed in a trapezoidal shape with an equal cross section, and is implanted with its narrow side facing the side 3b, so that the side 3b is worn to some extent. Thus, even if the auxiliary chip 32 is exposed, the auxiliary chip 32 itself does not fall off, and the progress of abrasion can be suppressed more reliably to prevent the chip 9 from falling off.

In this embodiment, the auxiliary chip 32
Is set to be approximately equal to the hardness of the chip 9 or to a range lower than about HRA8. However, if the hardness of the auxiliary tip 32 is lower than this range, the side surface 3 has a lower hardness.
On the other hand, if the hardness of the auxiliary tip 32 is higher than the hardness of the tip 9, especially when excavating the existing buried object, the auxiliary tip 32 may have a mountain shape. With respect to the wear of the tip surface 3a of the formed blade portion 3 and the tips 9 projecting in accordance with the mountain shape, the auxiliary tips 32.
The wear of the chips 9 arranged between the two is delayed, and the wear of the chips 9 may cause difficulty in increasing the number of the chips 9 involved in excavation and improving the excavation efficiency. is there. Therefore, the hardness of the auxiliary tip 32 is substantially equal to that of the tip 9 as in the present embodiment, so that
It is desirable to set the range to about A8 lower. Further, the third embodiment may be combined with the second embodiment to embed the auxiliary chip 32 in the side surface 3b inclined backward.

[0033]

As described above, according to the present invention,
When excavating from the soft layer to the medium hard rock layer, the excavation is performed by the tip on the top side of the tip surface of the bit body formed in the mountain shape of the excavation bit, so all the chips implanted in this bit body are While it is possible to prevent wear, on the other hand, when excavating an existing buried object formed of reinforced concrete or steel, or steel and unreinforced concrete, the tip surface and the tip are formed at the top of the chevron. Efficient excavation can be performed because the number of chips involved in excavation increases as the material wears from the side to the foot side, and excavation of a medium-hard rock layer from such a soft layer and reinforced concrete or steel, or steel and Excavation of a buried object formed from plain concrete can be performed reliably and continuously.

[Brief description of the drawings]

FIG. 1 is a plan view of a drill bit 1 and a holder 5 according to a first embodiment of the present invention as viewed from a distal end side.

FIG. 2 is a side view of a drill bit 1 and a holder 5 of the embodiment shown in FIG.

FIG. 3 is a sectional view taken along the line ZZ in FIG. 1;

4 is a plan view of a part of the cutter ring 4 to which the cutting bit 1 of the embodiment shown in FIG.

FIG. 5 is a cross-sectional view corresponding to a ZZ cross-sectional view in FIG. 1 showing a drill bit 21 and a holder 5 according to a second embodiment of the present invention.

FIG. 6 is a plan view of a drill bit 31 and a holder 5 according to a third embodiment of the present invention, as viewed from a distal end side.

7 is a side view of the drill bit 31 and the holder 5 of the embodiment shown in FIG.

[Explanation of symbols]

 1,21,31 Drilling bits 2 Bit body 3 Blade part 3a Tip surface of blade part 3 (tip surface of bit body 2) 3b Side surface of blade part 3 (side surface of bit body 2) 4 Cutting 5 Holder 6 Mounting part 9 Tip 10 Mounting recess 32 Auxiliary tip θ Incline angle of tip surface 3a of bit body 2 α Retraction angle of side surface 3b of bit body 2

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Takeshi Hayashi 1528 Nakashinda, Yokoi, Kobe-cho, Yasuhachi-gun, Gifu Prefecture Inside the Mitsubishi Materials Corporation Gifu Works (72) Inventor Hitoya Hisada, Yoji, Kobe-cho, Yasuhachi-gun, Gifu Prefecture 1528 Naka-Nitta, Gifu Works, Mitsubishi Materials Corporation (72) Inventor Katsunori Ueda 154-1, 4-ku, Nishinasuno-cho, Nasu-gun, Tochigi Prefecture Goyo Construction Co., Ltd. (72) Inventor Haruo Takahashi Tochigi 154-1, Yosoku-cho, Nisnasuno-cho, Nasu-gun, Goyo Construction Co., Ltd. (72) Inventor: Mikio Hirai In-house, Goyo Construction Co., Ltd. Inventor Tetsuo Furuta 2-2-8 Koraku, Bunkyo-ku, Tokyo Inside Goyo Construction Co., Ltd. (72) Inventor Toru Inada 6 Minamioi, Shinagawa-ku, Tokyo 26-3 Omori Bell Port Goyo Construction Co., Ltd. Tokyo Branch (72) Inventor Yuji Tanaka 1-7-89 Minami Kohoku, Suminoe-ku, Osaka City, Osaka Prefecture Hitachi Zosen Corporation (72) Inventor Hideyo Kitajima Osaka, Osaka 1-7-89 Minami Kohoku, Suminoe-ku, Hitachi F-term in Hitachi Zosen Corporation (reference) 2D029 FA01 FB01 FC03 FD00

Claims (6)

[Claims] An excavation bit attached to the tip of a cutter ring that is rotated around an axis, the bit body having a mountain-shaped tip surface that protrudes toward the tip side along the rotation direction of the cutter ring. A drill bit, wherein a plurality of chips harder than the bit body are implanted with their tips protruding in a mountain shape along the tip surface of the bit body. 2. A tilt angle formed by a mountain-shaped slope formed by a tip end surface of the bit body with respect to a plane orthogonal to the axis is 3 °.
The drill bit according to claim 1, wherein the drill bit is set in a range of up to 12 °. 3. The bit body according to claim 1, wherein a side surface of the bit body facing the inner peripheral side or the outer peripheral side of the cutter ring is formed as an inclined surface that gradually retreats toward a rear end side. The drill bit according to claim 2. 4. The excavation bit according to claim 3, wherein the receding angle of the side surface is set in a range of 2 ° to 12 °. 5. An auxiliary chip harder than the bit main body is embedded in a side surface of the bit main body facing the inner peripheral side or the outer peripheral side of the cutter ring. 4. A drill bit according to any one of 4 above. 6. The drill bit according to claim 5, wherein the hardness of the auxiliary tip is set to be equal to or lower than the hardness of the tip by HRA8.