JP2004036260A - Excavating tool - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prolong the life of a tool by reducing damage to side surfaces 4C and 4D, which abut on each other, of a bit 4 and suppressing a decrease in the positioning accuracy and rigidity of the bit 4 even if the damage is made greater. <P>SOLUTION: In this excavating tool, the bits 4 are attached to a tip part 1A of a device 1 for being rotated around the axis O, so as to be rotatable around the central axis X eccentric with respect to the axis O; and the mutual side surfaces 4C and 4D abut each other by having the bits 4 rotated around the respective central axes X along with the rotation of the device 1 in excavation, so that positioning can be performed in a state wherein an outside diameter from the axis O is enlarged. A recess 3, which is recessed to the side of a back end, is formed at the tip part 1A; a protrusion 6 for being housed in the recess 3, which is protruded to the side of the back end, is formed on a back end surface 4B of the bit 4; and the protrusion 6 can abut on or get close to a wall surface 3A, which is directed in a rotational direction T in the excavation, of the recess 3 in a state wherein the diameter of the bit 4 is expanded. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention is mainly used by being inserted into a cylindrical casing, and when drilling, the drill is rotated in a state where the bit protrudes from the end of the casing, so that the outer diameter of the bit is enlarged and the drilling hole into which the casing is built. The present invention relates to an excavation tool which excavates a hole and rotates in a direction opposite to the direction of the excavation so that the bit outer diameter is reduced and the casing can be pulled out while leaving the casing in the hole.
[0002]
[Prior art]
As this type of excavating tool, a device that is rotated around an axis, and a plurality of bits that are rotatably attached to a tip portion thereof around a central axis eccentric from the axis by, for example, fitting a shaft with a hole are provided. With the device being rotated in one direction around the axis during excavation, the bits rotate around their respective central axes due to excavation resistance and their side surfaces come into contact with each other, so that the outer diameter from the axis is increased. When the device is rotated in the opposite direction to the one direction, the bit also rotates in the opposite direction, so that the side surfaces also come into contact with each other so that There is known one that is positioned in a state where the diameter is reduced. Such an excavating tool is inserted into a cylindrical casing with the bit reduced in diameter, protrudes the bit from the tip of the casing, is rotatable, and is capable of moving forward with the casing on the tip side. During excavation, the device receives the rotational force in one direction and the striking force toward the tip, so that the outer diameter of the bit is larger than the outer diameter of the casing, and the bit is advanced with the casing while rotating. Then, the casing is erected inside the piercing hole while forming the piercing hole, and when the piercing hole is formed to a predetermined depth and the casing is erected, the bit is reduced by rotating the device in the opposite direction. Therefore, the casing can be retracted from the hole and pulled out while the casing remains in the hole.
[0003]
[Problems to be solved by the invention]
By the way, while the above-described drilling is repeatedly performed for a long time by such a drilling tool, the side portions of the bit that receives the rotational force around the center line while abutting each other may be damaged by wear or the like. Is inevitable. However, if such damage progresses, the positioning accuracy and rigidity in a state where the bit is expanded and contracted is impaired, and rattling is caused. As a result, the support of the bit becomes unstable, and the amount of expansion is increased. When the bit is made rotatable by fitting the shaft hole as described above, the load may be concentrated on the rotating shaft and the shaft may be broken.
[0004]
The present invention has been made under such a background, and in a drilling tool having the above-described configuration, it is possible to reduce damage to side portions of a bit abutting on each other, and to perform positioning of a bit even if damage progresses. It is an object of the present invention to provide an excavating tool capable of suppressing deterioration of rigidity and rigidity, thereby extending tool life.
[0005]
[Means for Solving the Problems]
In order to solve the above problems and achieve such an object, according to the present invention, a plurality of bits are rotatably mounted around a central axis eccentric from the axis at the tip of a device rotated around the axis. An excavating tool that is positioned in a state where the outer diameter from the axis is enlarged by rotating the bits around their respective central axes as the device is rotated during excavation and abutting each other on the sides. In the device described above, a recess is formed at the front end of the device, the recess is recessed toward the rear end, and at the rear end surface of the bit, a protrusion is formed that projects toward the rear end accommodated in the recess. It is characterized in that it can be brought into contact with or close to a wall surface of the concave portion which faces in the direction of rotation during excavation in a state where the diameter is increased. Therefore, according to such an excavating tool, if the convex portion formed on the rear end surface of the bit can be abutted on the wall surface of the concave portion of the device in a state where the bit is expanded in diameter, the bit is In addition to the abutment between the side surfaces, the positioning is performed by the abutment of the convex portion on the concave wall surface, so that the rotational force during excavation is prevented from being concentrated on the side surface portion and the damage is reduced. In the case where the convex portion is allowed to approach the concave wall surface in the expanded state, if the side surface portion is damaged, the convex portion comes into contact with the concave wall surface, and the rotational force is reduced. Since the positioning accuracy and rigidity of the bit are ensured, in any case, the backlash of the bit can be prevented and stable support can be achieved.
[0006]
Here, in the case where the convex portion on the rear end surface and the wall surface of the concave portion facing the rotation direction at the time of excavation can be made close to each other in a state where the bit is enlarged in this way, when the convex portion and the concave portion wall surface If the distance between the bits is too large, even if the side portion of the bit is damaged, the convex portion may not hit the wall surface, and the above-described effect may not be sufficiently obtained. It is desirable that it be 6 mm or less. In the case where the convex portion can be brought into contact with the wall surface of the concave portion in the bit expanded state, this interval is 0 mm. Further, in the case where a discharge groove for excavation chips generated during excavation, that is, a so-called cutting powder is formed to extend toward the rear end side on the outer periphery of the front end portion of the device, the concave portion is formed at the front end of the discharge groove. It is desirable that the device be formed so as to communicate with the side, so that it is possible to prevent the formation of the above-mentioned concave portion from causing a large thickness of the device to be cut and the rigidity thereof to be impaired.
[0007]
BEST MODE FOR CARRYING OUT THE INVENTION
1 to 4 show an embodiment of the present invention. In the present embodiment, as shown in FIGS. 1 to 3, the device 1 has a substantially multi-stage cylindrical shape in which the front end 1A is one step larger in diameter than the rear end 1B. By attaching a hammer (not shown), during excavation, a rotating force is applied around the axis O in the direction indicated by the symbol T in the figure, and a striking force is applied to the tip side in the direction of the axis O (left side in FIG. 1).
[0008]
Further, the front end portion 1A has a multi-stage shape in which the rear end portion is slightly larger in diameter than the front end side, so that the outer periphery thereof has a step protruding toward the rear end side. The outer diameter of the step 1C, that is, the maximum diameter of the device 1 is set to a size that can be inserted into the inner periphery of a cylindrical casing (not shown), while being larger than the step 1C. The outer diameter of the distal end portion of the distal end portion 1A on the distal end side is set to a size that can be inserted into the inner periphery of the cylindrical casing top, which is one step smaller in inner diameter, which is attached to the forefront of the casing. By contacting the rear end of the casing top, only the impact force is transmitted to the casing, so that the casing moves forward and can be embedded in the drilled hole. In this state, in a state where the step portion 1C is in contact with the rear end of the casing top, the distal end face 1D of the device 1 is slightly projected from the front end of the casing top.
[0009]
On the outer periphery of the distal end portion 1A of the device 1, a discharge groove 2A for cutting powder having a large width in the circumferential direction and a discharge groove 2B having a small width adjacent to the rotation direction T side thereof are respectively parallel to the axis O. A plurality of pairs (three pairs in the present embodiment) of such pairs of discharge grooves 2A and 2B are located at equal intervals in the circumferential direction so as to extend from the distal end surface 1D to the rear end of the distal end portion 1A. It is formed so that. Further, of the pair of scouring powder discharge grooves 2A, 2B,..., The tip end side of the discharge groove 2A located on the rear side in the rotation direction T (clockwise direction in FIGS. 2 and 3). A recess 3 is formed so as to be recessed one step from the front end face 1D to the rear end side so as to communicate with the discharge groove 2A. The concave portion 3 has a smaller length than the discharge groove 2A so that a portion of a fixed length on the distal end side of the discharge groove 2A has a substantially isosceles trapezoidal shape as shown in FIG. Is formed so as to be deeply cut in the inner peripheral side and largely cut off in the rotation direction T side, and the wall surface 3A facing the rotation direction T side is flush with the wall surface facing the rotation direction of the discharge groove 2A. The wall surface 3B facing the rear side in the opposite rotation direction T does not reach the discharge groove 2B adjacent to the discharge groove 2A, and the circumferential distance between the wall surfaces 3A and 3B is The bottom surface 3 </ b> C facing the tip side of the concave portion 3 is formed in a planar shape perpendicular to the axis O, and is gradually reduced toward the inner peripheral side of the device 1. Note that the device 1 is formed with a compressed air exhaust hole 1E from the rear end 1B along the axis O, and the distal end side of the exhaust hole 1E penetrates the device 1 along the axis O. As shown in FIG. 3, it is opened at the center of the front end face 1D, and is branched off in the middle to be opened at the bottom face 3C of each recess 3 respectively.
[0010]
Further, a plurality of (three in this embodiment) bits 4 are also attached to the distal end face 1D of the device 1 at equal intervals in the circumferential direction. These bits 4 have the same shape and size as each other, and have a thick flat plate-like end surface 4A having a substantially sector shape as shown in FIGS. A large number of button-side chips 5 made of a hard material such as a hard alloy are implanted, and the rear end face 4B of the bit 4 is mostly formed in a plane shape perpendicular to the axis O so that it can be in close contact with the front end face 1D. Have been. However, in the present embodiment, the fan shape formed by the distal end face 4A has a biased shape, that is, one of two sides intersecting the center (a main part of the fan) is a long side, and the other is a longer side. The short side is also a short side, and the arc-shaped side connecting the ends of these two sides has a long-side portion having an arc shape whose radius from the center is larger than the casing or the casing top. In addition, the portion on the shorter side than this is an arc having a radius substantially equal to the outer diameter (radius) of the portion on the tip side of the step portion 1C of the tip portion 1A in order toward the shorter side. It is formed by a straight line so that the distance to the center becomes gradually smaller toward the shorter side. In addition, the sector angle of the sector formed by the tip end surface 4A, that is, the intersection angle of the long and short sides is a value obtained by dividing 360 ° by the number of bits 4, and is 120 ° in the present embodiment.
[0011]
The bit 4 formed in this way has the side surface 4C connected to the long side portion of the tip end surface 4A of the respective side surfaces substantially oriented in the rotation direction T, and the side surface 4D connected to the short side portion has substantially the rotation direction. For example, a columnar shape extending parallel to an axis O protruding substantially at the center of the rear end face 4B of the bit 4 with the side surface 4E connected to the arc-shaped side portion directed substantially toward the outer periphery toward the rear side of T. The shaft is rotatable and is prevented from falling on the distal end side in a hole parallel to the axis O formed at equal intervals in the circumferential direction on the circumference of one circle centered on the axis O on the distal end surface 1D of the device 1. The hole is eccentric from the axis O to be rotatable about the central axis X of the hole, and is attached to the distal end portion 1A of the device 1. Note that these side surfaces 4C to 4E are flat surfaces parallel to the axis O.
[0012]
Thus, the plurality of bits 4... Rotatably mounted around the central axis X as shown in FIG. 2 when viewed from the tip due to the excavation resistance when the device 1 receives a rotational force in the rotational direction T during excavation. The bit 4 is rotated clockwise around the central axis X, and the side face 4D of the bit 4 located on the rotation direction T side between the circumferentially adjacent bits 4, 4 is located on the rear side in the rotation direction T. Abuts against the center portion of the side surface 4C of the bit 4, the center of the tip end surface 4A of each bit 4 is located on the axis O, and the portion of the side surface 4E closer to the side surface 4C is more peripheral than the casing or the casing top. And is positioned in a state where the diameter is enlarged. At this time, the discharge grooves 2A and 2B of the device 1 and the concave portion 3 communicating with the discharge groove 2A are opened on the rotation direction T side of the side surface 4C of each bit 4 when viewed from the front end. The wall surface 3A of the concave portion 3 is retracted one step backward from the side surface 4C in the rotation direction T so as to be parallel to the side surface 4C.
[0013]
On the other hand, when the device 1 is rotated backward in the rotation direction T after excavation, the bits 4... Rotate counterclockwise around the central axis X as shown in FIG. The side surface 4D of the bit 4 is abutted against the portion of the side surface 4C of the bit 4 located on the rear side in the rotation direction T on the side surface 4E side, so that all the bits 4. Is positioned with the diameter reduced. At this time, the side surface 4C of each bit 4 is located behind the wall surface 3B of the concave portion 3 opened on the rotation direction T side of the side surface 4C in the diameter-expanded state in the rotation direction T when viewed from the front. Has been.
[0014]
On the rear end face 4B of these bits 4, a convex portion 6 is formed on the side 4E side of the ridge line crossing the side face 4C so as to protrude from the rear end face 4B toward the rear end side in the axis O direction. Have been. The protruding portion 6 has a ridge shape extending along the intersecting ridge portion with the side surface 4C of the rear end surface 4B, and is integrated with the bit 4 so that a cross section orthogonal to the intersecting ridge portion has a rectangular shape. The side surface facing the rotation direction T side and the end surface of the bit 4 on the side surface 4E side are flush with the side surface 4C and the side surface 4E, respectively, and the side surface facing the rotation direction T rear side. Is parallel to the side surface 4C. The amount of protrusion of the convex portion 6 from the rear end surface 4B and the length in the direction along the crossed ridge line portion are the amount of depression of the concave portion 3 from the distal end surface 1D of the device 1 and the amount of depression from the outer periphery of the distal end portion 1A. The thickness of the convex portion 6 between the side surfaces is substantially the same as the retreat amount in which the wall surface 3A of the concave portion 3 retreats from the side surface 4C of the bit 4 in the expanded state. Or it is slightly smaller. That is, the projection 6 is always accommodated in the recess 3 regardless of the rotational position of the bit 4 about the central axis X.
[0015]
As a result, the convex portion 6 is housed in the concave portion 3 with the rear end face 4B of the bit 4 being in close contact with the front end face 1D of the device 1 as described above, and as shown in FIG. It is integrally rotatable around the central axis X without interfering with the operation, and can contact the wall surface 3A facing the rotation direction T side of the concave portion 3 in the enlarged diameter state. It can be approached with an interval of the difference. In the case where the convex portion 6 can be approached to the wall surface 3A in the expanded state, the distance between the convex portion 6 and the wall surface 3A, that is, the amount of retreat from the side surface 4C of the bit 4 to the wall surface 3A in the expanded state. And the thickness of the convex portion 6 is set to 6 mm or less (for example, in the range of 1 to 6 mm). Further, even when the bit 4 is reduced in diameter, the side surface 4C of the bit 4 in the rotation direction T is located behind the wall surface 3B of the recess 3 in the rotation direction T as described above. Therefore, the convex portion 6 whose side surface 4C and the side surface facing the rotation direction T are flush with each other does not interfere with the wall surface 3B.
[0016]
Therefore, in the excavating tool configured as described above, at the time of excavation, the device 1 is rotated by receiving the rotational force in the rotational direction T, and accordingly, the bits 4 are rotated around the central axis X as described above. And the side faces 4C and 4D abut on each other so that the protrusions 6 are positioned in an enlarged state, and at the same time, the protrusions 6 are disposed on or close to the wall surface 3A of the recess 3 facing the rotation direction T. It becomes. For this reason, when the convex portion 6 is in contact with the wall surface 3A of the concave portion 3 in the enlarged diameter state, the bit 4 is positioned by the contact between the side surfaces 4C and 4D, and the bit 6 is positioned on the wall surface. 3A, it is possible to prevent the rotational force transmitted from the device 1 to the bit 4... From being concentrated only on the contact portions of the side surfaces 4C, 4D. 4D can be prevented, thereby avoiding a change in the diameter expansion amount due to deterioration of the positioning accuracy of the bits 4 and breakage due to the concentration of the load on the shaft, thereby promoting stable excavation for a long period of time. It becomes possible.
[0017]
On the other hand, when there is an interval between the convex portion 6 and the wall surface 3A in this expanded state and the convex portion 6 can be approached to the wall surface 3A, the positioning of the bits 4. This is mainly due to the contact between the side surfaces 4C and 4D. However, if the side surfaces 4C and 4D are damaged during the long-term use such as wear and the positioning accuracy is deteriorated, the convex portion 6 and the wall surface 3A may be damaged. Becomes small, and the convex portion 6 comes into contact with the wall surface 3A. Thereafter, as in the above-described case, the contact between the convex portion and the wall surface 3A and the contact between the side surfaces 4C and 4D cause the bit 4. It will be positioned. Therefore, even in this case, stable excavation can be performed, and at the beginning of excavation, the load of excavation can be prevented from acting on the protruding portion 6. Therefore, the excavation is smaller than the contact area of the side surfaces 4C and 4D. Even when it is difficult to secure the contact area of the portion 6 with the wall surface 3A, it is possible to prevent a situation in which the convex portion 6 is damaged before the side surfaces 4C, 4D are damaged.
[0018]
However, even when the convex portion 6 is allowed to approach the wall surface 3A of the concave portion 3 in such an enlarged state, if the distance between the convex portion 6 and the wall surface 3A is too large, damage to the side surfaces 4C and 4D may occur. The projection 6 does not come into contact with the wall surface 3A unless it progresses greatly, and the diameter expansion amount may change significantly during that time, or the shaft may be broken due to concentration of load. For this reason, even when the convex portion 6 is close to the wall surface 3A facing the rotation direction T of the concave portion 3 in the expanded state and there is an interval between them, this interval is 6 mm or less as in the present embodiment. It is desirable to be set to. When the interval is 0 mm, the convex portion 6 comes into contact with the wall surface 3A in the expanded state as described above.
[0019]
On the other hand, in the present embodiment, the concave portion 3 in which the convex portion 6 is accommodated is formed so as to communicate with the distal end side of the cutting dust discharge groove 2A formed on the outer periphery of the device 1 to form the concave portion 3. Therefore, the thickness of the device 1 can be prevented from being largely scraped off, and the rigidity of the device 1 can be ensured. In addition, a compressed air exhaust hole 1E formed along the axis O of the device 1 is branched and opened on the bottom surface 3C of the concave portion 3 so that the compressed air ejected from the exhaust hole 1E during excavation. The cutting dust is sent out toward the rear end side in the discharge grooves 2A and 2B, and the cutting air can be removed by the compressed air even if the cutting dust or earth and sand enters between the projection 6 and the wall surface 3A. Therefore, there is also a situation where the bit 4 is not reliably expanded because the side surfaces 4C and 4D do not come into contact with each other due to the bitten dust and earth and sand being caught between the convex portion 6 and the wall surface 3A. It can be prevented before it happens.
[0020]
【The invention's effect】
As described above, according to the present invention, the convex portion formed on the rear end surface of the bit is housed in the concave portion formed in the device, and can be brought into contact with the wall surface of the concave portion facing the rotation direction in the expanded state. Or, because they are close to each other, it is possible to prevent damage to the side surfaces of the bits that abut each other, or to prevent such damage from progressing greatly, and to maintain the positioning accuracy of the bits. Thus, it is possible to prevent a change in the diameter expansion amount, breakage of the shaft, etc., and to promote stable excavation for a long period of time.
[Brief description of the drawings]
FIG. 1 is a side view showing an embodiment of the present invention.
FIG. 2 is a front view of the embodiment shown in FIG.
FIG. 3 is a front view of the embodiment shown in FIG.
FIG. 4 is a perspective view showing a periphery of a concave portion 3 of the embodiment shown in FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Device 1A Tip part 2A, 2B of device 1 Discharge groove 3 Recess 3A Wall 4 bit 4B facing the rotation direction T of recess 3 Rear end surface 4C-4E of bit 4 Side surface 6 of bit 4 Convex part O Axis X bit of device 1 4 center axis T Rotation direction of device 1 during excavation

Claims (3)

A plurality of bits are rotatably mounted around a central axis eccentric from the axis at the tip of the device that is rotated around the axis, and the bits are rotated around the respective central axes as the device is rotated during excavation. In the excavation tool which is positioned in a state where the outer diameter from the axis is enlarged by rotating and the side surfaces abut against each other, a concave portion is formed at the front end portion of the device, the concave portion being recessed toward the rear end side, On the rear end surface of the bit, a convex portion protruding toward the rear end housed in the concave portion is formed, and the convex portion is a wall surface that faces the rotation direction at the time of excavation of the concave portion in a state where the bit is expanded in diameter. An excavating tool characterized in that it can be brought into contact with or approachable to a digging tool. The excavating tool according to claim 1, wherein a distance between the convex portion and a wall surface of the concave portion facing in a rotating direction at the time of excavation is 6 mm or less in a state where the bit is expanded. The device according to claim 1, wherein a discharge groove for cutting dust is formed on an outer periphery of a front end portion of the device so as to extend toward a rear end side, and the concave portion is communicated with a front end side of the discharge groove. The drilling tool according to claim 2.

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