JP2007070918A - Excavating head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an excavating head which is free from an influence of excavation chips, dispenses with a complicated structure of a hydraulic mechanism etc. , positively expands/contracts diameter expandable bits to a predetermined value, and protects the diameter expandable bits, a rotating shaft, and a rotary body from being damaged during excavation. <P>SOLUTION: The excavating head is mounted on a front end of the rotary body 1 which is rotated about an axis O during excavation, and formed of excavation bits 4 and the diameter expandable bits 6. The excavation bits 4 are arranged on an external peripheral side of the front end of the rotary body 1. The diameter expandable bits 6 are located at an almost equal location to that of the excavation bits 4 in an axial O direction, and between the excavation bits 4 circumferentially adjacent to each other in a circumferential direction about the axis O. The diameter expandable bits 6 are each rotatable about a rotation axis C that is spaced away from the axis O toward an outer periphery so as to expand/contract an external diameter thereof from the axis O. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an excavation head for excavating the ground provided at the tip of a rotating body that is rotated about an axis in an excavation method that uses rotational force and thrust as main excavation forces.

In such excavation method, an auger shaft (spiral rod) having a spiral screw provided on the outer periphery is used as the rotating body, and the ground is excavated by an excavation head disposed at the tip, that is, an earth auger head. An auger drilling method is known. Here, in excavation by this type of earth auger, a casing pipe (steel pipe) is arranged on the outer periphery of the auger shaft and driven along with the earth auger while being driven into the ground. In some cases, a method of pulling out only is employed (for example, see Patent Document 1). In an earth auger head used in such a construction method, an excavation diameter larger than the outer diameter of the casing pipe is required during excavation, but after the excavation is finished, the outer diameter must be smaller than the inner diameter of the casing pipe. Therefore, for example, as described in Patent Documents 2 to 4, there is proposed an earth auger head that includes a diameter-expanding bit that can be rotated around a rotation axis and whose outer diameter can be expanded / reduced. ing.
JP 2004-11102 A Japanese Utility Model Publication No. 63-71285 Japanese Utility Model Publication No. 1-75194 Japanese Utility Model Publication No. 62-94187

  However, first of all, in the earth auger head described in Patent Document 2, the diameter-expanding bit is pivotally supported on a spiral screw of the earth auger and is rotatably attached. However, since excavation waste generated during excavation in such excavation by the earth auger is discharged through the spiral screw, the earth auger head described in Patent Document 2 uses the excavation waste to reduce the diameter of the expanded bit. When the diameter expansion operation is obstructed, the outer diameter of the casing pipe cannot be made larger than the outer diameter of the casing pipe, or conversely, excavation debris is caught between the diameter expansion bit and the spiral screw. There is a possibility that the diameter-enlarged bit cannot be reduced to a diameter smaller than the inner diameter of the casing pipe.

  Further, in the earth auger head in which the diameter-enlarged bit is supported so as to be rotatable about the rotation axis in this way, if there is no mechanism for forcibly expanding / reducing the diameter-enlarged bit, some reaction force is increased. If it is not applied to the diameter bit, the outer diameter cannot be expanded and contracted reliably and smoothly. However, in the earth auger head described in Patent Document 3, the diameter-expanding bit is provided on the rear end side with respect to the excavation bit provided at the tip of the spiral screw, and the hole drilled by the excavation bit is provided. Since it does not contact the bottom of the hole, it is necessary to rely on contact with the inner wall surface of the excavation hole or inertia accompanying rotation of the earth auger to obtain the reaction force as described above. For this reason, it is difficult to reliably make the outer diameter smaller than the inner diameter of the casing pipe, which is smaller than the inner diameter of the excavation hole, particularly when reducing the diameter of the expanded bit. In addition, for example, it is conceivable that the diameter expansion bit is forcibly expanded / reduced as described above by a mechanism such as hydraulic pressure. In this case, however, such a hydraulic mechanism must be provided in the earth auger, which is economical. is not.

  On the other hand, in the earth auger head described in Patent Document 4, the rotating shaft is disposed close to the outer periphery of the auger shaft so as to be orthogonal to the axis of the auger shaft, and the radius of the drilling hole is around the rotating shaft. The diameter-expanding bit having a length substantially equal to the diameter of the rotation rotates to expand the diameter, and excavation is performed. However, in such a case, there is a possibility that the excavation range by the enlarged-diameter bit pivotally supported on the auger shaft may become too large. In particular, if the inner diameter of the excavation hole is large, the enlarged-diameter bit itself and the above-described rotating shaft that supports this Alternatively, the load on the auger shaft may increase and cause damage.

  The present invention was made under such a background, and as described above, in a drilling method using a rotational force and a thrust as the main drilling force, that is, a drilling method used for a drilling method in which no striking force is given, It is possible to reliably expand and reduce the diameter expansion bit to a predetermined diameter without being affected by drilling waste generated during excavation and without requiring a complicated mechanism such as a hydraulic mechanism. An object of the present invention is to provide an excavation head that is capable of reducing the load on a rotating body such as a diameter expansion bit, a rotating shaft, or an auger shaft during excavation and preventing the damage.

  In order to solve the above-described problems and achieve such an object, the present invention provides a drilling head provided at a distal end portion of a rotating body that is rotated around an axis during excavation, the outer periphery of the distal end portion of the rotating body. The excavation bit arranged on the side of the excavation bit and the excavation bit are arranged at substantially the same position in the axial direction, and in the circumferential direction around the axial line, between the excavation bits adjacent in the circumferential direction. And a diameter-expanding bit that is rotatable about a rotation axis that is distant from the axis toward the outer periphery, and whose outer diameter from the axis can be increased or decreased.

  In the drilling head having such a configuration, a drilling bit is first provided on the outer peripheral side of the distal end portion of the rotating body, and a diameter expanding bit is disposed at a position substantially equal to the drilling bit in the axial direction of the rotating body. Therefore, in the state where the diameter-enlarged bit is rotated to the outer peripheral side around the rotation axis and the diameter is expanded, the load is distributed by the excavation bit on the inner peripheral side of the excavation hole and the diameter expansion bit on the outer peripheral side. Excavation can be performed, and damage to a rotating body such as a diameter expanding bit, a rotating shaft, or an auger shaft can be prevented. In particular, since this diameter-expanding bit is rotated around the rotation axis away from the axis of the rotating body and expanded and contracted, the moment acting on this rotation axis during excavation is reduced to ensure its breakage. Can be prevented. Further, in this way, the diameter expansion bit is disposed at substantially the same position as the drill bit in the axial direction, so that the diameter expansion bit can be brought into contact with the bottom of the drill hole and a reaction force can be applied from the hole bottom. Further, it is possible to reliably expand and contract the diameter by rotating the diameter expanding bit around the rotation axis without requiring a hydraulic mechanism or the like.

  Further, the diameter-expanding bit is provided in the circumferential direction around the axis of the rotating body so as to be positioned between the excavation bits adjacent to the circumferential direction, that is, on the outer peripheral side of the tip end portion of the rotating body. It is arranged so as to be out of phase in the circumferential direction with respect to the excavation bit, so that the excavation waste generated and discharged by the excavation bit at the time of excavation may hinder the expansion / reduction operation of the expansion bit. There is nothing. For this reason, according to the excavation head having the above configuration, the casing pipe is driven into the excavation hole in combination with the fact that the diameter expansion bit can be surely expanded and contracted by the reaction force from the hole bottom as described above. Even when drilling, it is possible to drill a drilling hole with an inner diameter larger than the outer diameter of the casing pipe during drilling and smoothly insert the casing pipe. The diameter can be reduced so as to be smaller than the inner diameter of the casing pipe and can be pulled out.

  Here, as the rotating body, an auger shaft of an earth auger provided with a spiral screw on its outer periphery can be applied, and the excavation bit is provided at the tip of the spiral screw. Even when the drilling waste is discharged through the spiral screw, the diameter-expanding bit can be reliably expanded and contracted as described above. Even if the excavation bit and the diameter expansion bit are arranged at substantially the same position in the axial direction of the rotating body as described above, the cutting edge of the diameter expansion bit in the state where the outer diameter is expanded is excavated. It is desirable to be positioned on the rear end side in the axial direction from the cutting edge of the bit. By adopting such a configuration, the drilling bit is excavated on the inner peripheral side of the drilling hole by the drilling bit first, and then the outer peripheral side of the drilling hole is drilled on the outer peripheral side after the enlarged diameter expanding bit is drilled. Therefore, it is possible to further reduce the load on the diameter-enlarged bit to prevent the damage and to perform more efficient excavation.

  Further, in the excavation head having the above-described configuration, the diameter-enlarged bit can be expanded / reduced by the reaction force from the hole bottom as described above, and therefore the rotation axis of the diameter-enlarged bit is parallel to the axis. That is, the diameter-enlarged bit may be rotated and expanded / reduced on a plane orthogonal to the axis, but the axis of rotation is the axis line relative to the plane including the axis. When the drilling hole is drilled downward in the ground or the like by inclining toward the rotation direction side during excavation of the rotating body as it goes toward the rear end side of the direction, Even if the drilling head is not rotated in the reverse direction, if the drilling head is retracted and pulled up to the rear end side in the axial direction, the diameter-enlarged bit is rotated to the inner peripheral side around the rotation axis by its own weight. Diameter reduction bit and case It is possible to achieve a pull-out from the Ngupaipu.

  However, when the rotation axis is inclined in this way, it is desirable that the inclination angle of the rotation axis with respect to the plane including the axis is in the range of 15 ° to 60 °, and if the inclination angle is smaller than this, Also, after the excavation is completed, it is difficult to reduce the diameter of the diameter-enlarged bit unless the rotating body is reversely rotated to give a reaction force from the hole bottom. On the other hand, if the inclination angle is larger than this, it becomes easy to adopt a state where the diameter expansion bit is reduced in diameter, and when the drilling hole is drilled downward as described above, the diameter expansion bit can be formed only by turning the drilling head downward. In order to increase the outer diameter at the start of excavation, it is necessary to apply a reaction force by pressing the diameter-expanding bit against the bottom of the hole at the start of excavation. In addition to this, the load due to the pressing force may also act on the diameter-expanding bit and the rotating shaft, which may cause damage.

  In particular, when the rotating shaft is inclined to the rotation direction side during excavation of the rotating body with respect to the plane including the axis, as described above, Even when the cutting edge of the expanded bit in the state where the diameter is expanded is positioned on the rear end side in the axial direction from the cutting edge of the drilling bit, the cutting edge of the expanded bit in the state where the outer diameter is reduced Can be positioned closer to the tip end side in the axial direction than the cutting edge of the excavation bit. Then, at the start of excavation, the cutting edge of the diameter-expanding bit is brought into contact with the ground before the excavating bit, and the diameter-expanding bit is further reliably expanded by the reaction force accompanying the rotation of the excavating head. Is possible.

  1 to 5 show an embodiment of the present invention. In these drawings, reference numeral 1 denotes an auger shaft 1 as a rotating body in the present embodiment, which has a long outer cylindrical axis shape centered on an axis O, and a tip portion thereof (FIGS. 1 and 3). , The lower part in FIG. 4 and the front part of the drawing in FIG. 2 are vertically downward, and the rear end part (the upper part in FIGS. 1, 3, and 4 and the rear part of the drawing in FIG. 2) It is supported by an unillustrated excavator, and is sent to the front end side in the axis O direction while being rotated around the axis O in the rotation direction indicated by a symbol T in the drawings. The excavation head of this embodiment is disposed at the tip of the auger shaft 1 and excavates the ground using the rotational force and thrust applied to the auger shaft 1 as main excavation forces. Further, on the outer periphery of the auger shaft 1, a spiral plate-like spiral screw 2 that is twisted to the rear side in the rotation direction T around the axis O from the front end toward the rear end side is provided integrally with the auger shaft 1. On the further outer periphery of the spiral screw 2, a cylindrical casing pipe 3 is disposed coaxially with the axis O with a slight space between the spiral screw 2 as shown in FIGS. .

  Here, in this embodiment, as shown in FIG. 2, a pair of spiral screws 2 are provided symmetrically with respect to the axis O, and the leading edges thereof extend in a substantially radial direction with respect to the axis O, respectively. Thus, the phase difference in the circumferential direction is 180 °. Further, a plurality of excavation bits 4 each having a tip made of a hard material such as cemented carbide attached to the tip are provided at the tip end of each spiral screw 2 in the radial direction. The chip is mounted so as to protrude from the front end side and the rotation direction T side with an interval. Further, as shown in FIG. 1, a pair of center bits 5 each having a tip at the tip are similarly attached to the tip of the auger shaft 1 so that each tip protrudes toward the tip side and the rotation direction T side. The tip ends of these center bits 5 are positioned slightly closer to the tip end side in the axis O direction than the tip ends of the excavation bits 4.

  Further, at the tip of the auger shaft 1, the excavation bit 4 is located at an approximately equal position in the direction of the axis O with respect to the excavation bit 4, and between the excavation bits 4 adjacent in the circumferential direction in the circumferential direction around the axis O. At this position, a diameter-expanding bit 6 that is rotatable about a rotation axis C that is distant from the axis O toward the outer peripheral side so that the outer diameter from the axis O can be increased or decreased is disposed. That is, the diameter expansion bit 6 is disposed so as to be shifted in the circumferential direction with respect to the excavation bit 4. In this embodiment, the pair of diameter expansion bits 6 are symmetrical with respect to the axis O. Provided, and the phase difference in the circumferential direction with respect to the excavation bit 4 is approximately 90 °, that is, the excavation bit 4 and the diameter-expanding bit 6 are disposed at the tip of the auger shaft 1 at substantially equal intervals in the circumferential direction. ing.

  More specifically, the outer periphery of the tip of the auger shaft 1 has a pair of thick plate-like shapes symmetrical to each other with respect to the axis O so that the circumferential phase difference from the tip edge of the spiral screw 2 is approximately 90 °. The shanks 7 are welded so as to extend in a substantially radial direction with respect to the axis O, and a holder 8 is also attached to the tips (outer peripheral ends) of these shanks 7 by welding. Rotated about the rotation axis C extending in the direction of the axis O at a position away from the axis O toward the outer circumference side. It is supported freely. The distance from the axis O to the outer peripheral surface of the holder 8 is substantially equal to the outer diameter (radius) of the spiral screw 2 and is smaller than the inner diameter of the casing pipe 3. Also, hatched portions in the drawing are the welded portions of the auger shaft 1 and the shank 7 and the shank 7 and the holder 8.

  Here, the bottom surface 9A facing the front end side of the recess 9 is perpendicular to the rotation axis C, and the wall surface 9B facing the rotation direction T side of the recess 9 and the wall surface 9C facing the outer peripheral side intersect at the bottom surface 9A. In the corner portion, a circular blind hole-shaped mounting hole 10 centering on the rotation axis C is formed so as to extend to the rear end side. Further, a cross section of the mounting hole 10 is formed from the outer peripheral surface of the holder 8. A small-diameter pin hole 10A is formed in the mounting hole 10 so as to open in a semicircular cross section along the tangent line of the circle. The wall surfaces 9B and 9C of the recess 9 are both perpendicular to the bottom surface 9A and extend toward the rotational direction T toward the outer peripheral side and extend in a direction intersecting at an acute angle. The cross ridge line portion, that is, the portion extending from the corner portion of the bottom surface 9A has a concave cylindrical surface centered on the rotation axis C that smoothly contacts both the wall surfaces 9B and 9C.

  On the other hand, as shown in FIG. 5, the diameter expanding bit 6 can be fitted into the mounting hole 10 on one end side (left side in FIGS. 5A and 5B) of the flat upper surface 6A. An outer cylindrical mounting shaft 11 having an outer diameter is formed perpendicularly to the upper surface 6A, and the side surface 6B on one end side can be slidably contacted with the concave cylindrical surface formed by the intersecting ridge line portions of the wall surfaces 9B and 9C. A convex semi-cylindrical surface having a radius and coaxial with the mounting shaft 11, and a pair of side surfaces 6C and 6D connected to the side surface 6B are made parallel to each other and smoothly connected to the convex semi-cylindrical surface. Has been. A concave groove 11A having a substantially semicircular cross section having the same diameter as the pin hole 10A is formed in a substantially L shape in the circumferential direction on the outer periphery of the mounting shaft 11 as shown in FIG. Then, after inserting the mounting shaft 11 into the mounting hole 10 and inserting and fixing the pin 12 in the pin hole 10A and locking it in the concave groove 11A, the enlarged diameter bit 6 is as shown in FIG. The center axis of the mounting shaft 11 is coaxial with the rotation axis C of the mounting hole 10, the mounting shaft 11 is prevented from coming off while the top surface 6 A is in contact with the bottom surface 9 A of the recess 9, and the side surface 6 B is the crossed ridge line As long as the side surfaces 6C and 6D are in contact with the wall surfaces 9B and 9C, respectively, while being slidably contacted with each other, they are supported and attached to the holder 8 so as to be rotatable about the rotation axis C.

  Further, the side surface 6E on the other end side (the right side in FIGS. 5A and 5B) of the diameter-expanding bit 6 extends from the side surface 6C located on the rear side in the rotational direction T to the rotational direction T side in the attached state described above. The lower surface 6F is formed so as to bend in a multi-step shape toward the side surface 6D and to protrude even from the upper surface 6A toward the lower surface 6F. The tip 13 of the diameter-enlarged bit 6 is planted at the corner where the side surface 6E and the side surface 6F intersect the side surface 6D. The tip 13 is formed of a hard material such as cemented carbide like the tip of the excavation bit 4 or the center bit 5, and is joined to the recess having a V-shaped cross section formed in the corner by brazing or the like. When viewed from the other end side, as shown in FIG. 5 (c), it protrudes from the side surface 6D with a one-step convex V shape, and also viewed from the side surface 6D side and the lower surface 6F side. In some cases, as shown in FIGS. 5 (a) and 5 (b), two convex V-shapes are formed toward the other end side so as to protrude from the lower surface 6F and the side surface 6D, respectively, and the other end. The side portion is convex toward the other end side in accordance with the convex curve and inclination of the side surface 6E.

  Furthermore, the rotation axis C is inclined with respect to the plane including the axis O so as to go toward the rotation direction T as it goes to the rear end side in the axis O direction as shown in FIGS. The inclination angle θ with respect to the direction of the axis O is in the range of 15 ° to 60 °. In this embodiment, the rotation axis C is inclined on the tangential plane to the cylindrical surface with the axis O as the center, and therefore the inclination angle θ is in the tangential plane and the tangential plane. This is an intersection angle formed by the line of intersection with the plane including the orthogonal axis O and the rotation axis C. Further, the thick shank 7 is attached to the outer periphery of the auger shaft 1 so that the thickness direction of the shank 7 is inclined at an angle larger than the inclination angle θ with respect to the plane including the axis O. .

  The diameter expanding bit 6 attached to the outer periphery of the tip end portion of the auger shaft 1 through the shank 7 and the holder 8 in this manner is in a state where the side surface 6D is in contact with the wall surface 9C in the recess 9 as shown in FIGS. 2, the outer diameter (radius) from the axis O is reduced, and this outer diameter is smaller than the inner diameter (radius) of the casing pipe 3, so that the outer diameter of the spiral screw 2 is increased. It is made substantially equal to the diameter (radius). On the other hand, in the state where the diameter-expanding bit 6 is rotated around the rotation axis C and the side surface 6C is brought into contact with the wall surface 9B, the diameter-expanding bit 6 shown on the right side of FIGS. Thus, the outer diameter (radius) from the axis O of the outer peripheral end of the tip 13 is expanded, and this outer diameter is larger than the outer diameter (radius) of the spiral screw 2 and the inner diameter (radius) of the casing pipe 3. In addition, it is positioned slightly larger than the outer diameter (radius) of the casing pipe.

  Further, in the present embodiment, as described above, the rotation axis C is inclined with respect to the plane including the axis O, so that the diameter expansion bit 6 is expanded in diameter as shown in the right side of FIG. 1 and FIG. The position of the cutting edge of the tip 13 of the diameter-expanding bit 6 is rearward in the direction of the axis O than the position of the cutting edge of the tip 13 when the diameter-expanding bit 6 is reduced in diameter as shown in the left side of FIG. It will be located on the end side. As shown in FIG. 1, the blade tip position of the diameter-expanding bit 6 in this diameter-expanded state is positioned slightly on the rear end side in the axis O direction with respect to the tip position of the excavation bit 4 at the tip of the spiral screw 2. The position of the cutting edge of the diameter-expanding bit 6 in the reduced diameter state is positioned slightly on the front end side in the direction of the axis O with respect to the cutting edge position of the excavation bit 4, and in the present embodiment, it is projected most distally. The center bit 5 is designed to be substantially equal to the cutting edge position.

  When the auger shaft 1 provided with such an earth auger head at the tip is supported with the tip facing downward as described above, the diameter-expanding bit 6 is inserted around the rotation axis C by its own weight. 1 and 2, the side surface 6D is brought into contact with the wall surface 9C of the recess 9 as shown in FIG. 1 and FIG. The diameter is reduced, and the cutting edge position of the tip 13 is positioned slightly on the tip side in the axis O direction with respect to the cutting edge position of the excavation bit 4. Accordingly, when the earth auger head is grounded to the ground or the like in this state, the cutting edge of the tip 13 of the diameter-expanding bit 6 and the cutting edge of the center bit 5 provided at the tip of the auger shaft 1 in the present embodiment are the ground first. To eat.

  Further, when the auger shaft 1 is rotated in the rotational direction T around the axis O in this state and advanced toward the tip end side in the axis O direction, the diameter expansion bit 6 with the cutting edge of the tip 13 biting on the ground receives a reaction force. The side surface 6D is rotated around the rotation axis C so as to be separated from the wall surface 9C, and the outer diameter from the axis O is increased, and the cutting edge position of the tip 13 is retracted toward the rear end side in the axis O direction. It is done. Then, the auger shaft 1 is further rotated and advanced as it is, so that the cutting edge of the excavation bit 4 bites into the ground, and the side surface 6C of the enlarged diameter bit 6 is recessed as shown in the right side of FIG. 1 and FIG. 9, the outer diameter of the casing pipe 3 is slightly larger than the outer diameter of the casing pipe 3. In the embodiment, the center bit 5 can form an excavation hole having a diameter slightly larger than that of the casing pipe 3, and the casing pipe 3 is inserted into the excavation hole after the earth auger head and is placed in the ground. can do. The excavation waste generated by the excavation bit 4, the center bit 5, and the diameter-expanding bit 6 travels on the spiral spiral screw 2 that rotates integrally with the auger shaft 1 along the torsion in the axis O direction. It is pushed out to the side, that is upwards, and discharged.

  Further, after the excavation hole is formed to a predetermined depth and the casing pipe 3 is inserted, in this embodiment, when the auger shaft 1 is pulled up to the rear end side in the axis O direction, the diameter expansion bit 6 has the cutting edge of the tip 13 at the tip. In the same manner as described above, the other end of the excavation hole is rotated so that the other end faces downward, and the outer diameter thereof is reduced to be smaller than the inner diameter of the casing pipe 3. Therefore, by retracting the auger shaft 1 as it is, the casing pipe 3 remains in the excavation hole, and the auger shaft 1 can be pulled out through the casing pipe 3 together with the earth auger head.

  In the excavation head (earth auger head) configured as described above, at the time of excavation, the cutting edge of the excavation bit 4 that is disposed at the distal end portion of the spiral screw 2 and is located on the outer peripheral side of the distal end portion of the auger shaft 1 as a rotating body. On the other hand, in this embodiment, although it is slightly on the rear end side, the cutting edge of the tip 13 of the diameter-expanded bit 6 whose diameter has been expanded is disposed at a substantially equal position in the axis O direction. The excavation can be performed with the load distributed on the inner peripheral side by the excavation bit 4, the outer peripheral side by the diameter-expanding bit 6, and the central part by the center bit 5. For this reason, an excessive load does not act on the diameter-expanding bit 6, its rotating shaft (mounting shaft 11), or the auger shaft 1 itself, and it is possible to prevent damage or the like.

  In particular, the rotation axis C of the diameter-expanding bit 6 in the present embodiment is fitted into the mounting hole 10 of the holder 8 that is separated from the axis O of the auger shaft 1 to the outer peripheral side via the shank 7 and the mounting hole 10. Even when a drilling hole having the same inner diameter is formed, for example, the rotation shaft is provided directly on the outer periphery of the auger shaft so as to be orthogonal to the axis of the auger shaft. Compared to the earth auger head described in Patent Document 4, the rotating diameter of the diameter-expanding bit 6 can be reduced, so that the moment around the rotating shaft C is reduced and the mounting shaft 11 and the holder 8 are damaged. It can be surely prevented. In addition, in the present embodiment, the rotational axis C is disposed so as to extend in the direction of the axis O although it is inclined at an inclination angle θ with respect to the plane including the axis O, as described above. Compared with the case where the rotation axis is provided so as to be orthogonal to the axis, the moment acting in the direction of bending the rotation axis C itself can also be reduced.

  Further, the diameter expansion bit 6 is supported so as to be rotatable about the rotation axis C, and the diameter expansion bit 6 has its cutting edge disposed at a position substantially equal to the cutting edge of the excavation bit 4 in the axis O direction. Thus, the blade tip of the diameter expanding bit 6 is brought into contact with the bottom of the excavation hole, and the diameter expanding bit 6 can be surely expanded by the reaction force. For this reason, it is possible to form a drilling hole having a predetermined inner diameter at the time of excavation without taking a high-cost and complicated configuration that requires a hydraulic mechanism or the like. By rotating in the direction opposite to the rotation direction T, the diameter-expanding bit 6 is reduced to a diameter smaller than the inner diameter of the casing pipe 3 and the auger shaft 1 can be pulled out together with the earth auger head through the casing pipe 2. .

  Then, when the diameter-enlarged bit 6 that is rotatable in this way is expanded / reduced, in the earth auger head configured as described above, the expanded-diameter bit 6 is further adjacent in the circumferential direction around the axis O. It is disposed with a phase shift so as to be positioned between the excavation bits 4 at the tip, and therefore, the diameter of the diameter expansion bit 6 is increased or decreased by the excavation debris discharged on the spiral screw 2 as described above. It is possible to prevent the operation from being hindered. That is, the space between the drill bit 4 and the drill bit 4 is ensured by the gap between the drill bit 4 and the drill bit 4 in the circumferential direction. Therefore, for example, the diameter-reducing operation of the diameter-expanding bit 6 in which the drilling scrap has been expanded is caught between the side surface 6D or the side surface 6B and the wall surface 9C of the recess 9 to prevent or reduce the diameter-reducing operation. It is possible to prevent the diameter expansion operation from being disturbed by entering between the side surface 6C of the diameter expansion bit 6 and the wall surface 9B of the recess 9.

  Therefore, according to the earth auger head having the above-described configuration, even when the diameter-expanding bit 6 that is rotatable about the rotation axis C is expanded without using a hydraulic mechanism or the like as described above, it is generated during excavation. While the drilling waste is smoothly discharged along the spiral screw 2, it is possible to prevent the drilling waste from affecting the expansion / reduction operation of the diameter expanding bit 6. Such an effect is combined with the above-described diameter-expanding bit 6, its rotating shaft (mounting shaft 11), or the auger shaft 1 to prevent damage, so that a drill hole having a predetermined diameter can be surely formed during excavation. This enables the casing pipe 3 to be driven, and after the excavation is finished, the auger shaft 1 can be pulled out together with the earth auger head while leaving the casing pipe 3 alone on the ground. Can be planned.

  Further, in the earth auger head of the present embodiment, the rotation axis C, which is the center of rotation of the diameter-expanding bit 6, rotates in the excavation direction toward the rear end side with respect to the plane including the axis O of the auger shaft 1. Even if the position of the cutting edge of the diameter-expanding bit 6 is substantially equal to the position of the cutting edge of the excavation bit 4 in the axis O direction, it is respectively in the expanded / reduced diameter state. It is arranged at a position slightly retracted and advanced toward the rear end side and the front end side in the axis O direction. Accordingly, in the state where the diameter expansion bit 6 is expanded at the time of excavation, after the inner peripheral side of the excavation hole is excavated by the excavation bit 4 or the center bit 5, the diameter expansion bit 6 is formed on the outer peripheral side which is easily collapsed. It will be excavated, and it is possible to further reduce the load on the diameter-expanding bit 6, the rotating shaft (mounting shaft 11), and the auger shaft 1 to prevent the damage more reliably, and to promote more efficient excavation. Become.

  On the other hand, when the auger shaft 1 is retracted together with the earth auger head and pulled out from the casing pipe 3 after excavation is completed, the rotating shaft C is inclined as described above, so that the diameter-expanding bit 6 has its cutting edge by its own weight. Is rotated toward the inner peripheral side, and the outer diameter from the axis O is reduced. For this reason, according to the present embodiment, after the excavation is finished, the auger shaft 1 is reliably contracted without rotating the auger shaft 1 in the direction opposite to that during excavation and applying a reaction force from the bottom of the excavation hole. It is possible to pull out the earth auger head from the casing pipe 3 and to further increase the efficiency of excavation work.

  Further, in this embodiment, the position of the cutting edge of the diameter-expanding bit 6 is slightly positioned on the tip side in the direction of the axis O with respect to the cutting edge position of the excavation bit 4 in this embodiment, and the excavation starts. When the earth auger head is initially grounded downward on the ground or the like, the cutting edge of the enlarged diameter bit 6 and the cutting edge of the center bit 5 in the present embodiment first bite into the ground or the like. Therefore, by rotating the auger shaft 1 in the rotational direction T from this state, even if the diameter-expanding bit 6 is located within the excavation radius of the excavation bit 4 as shown on the left side in FIG. It is possible to reliably apply a reaction force from the ground or the like to the diameter expansion bit 6 to expand the outer diameter from the axis O and to form a drilling hole having a predetermined inner diameter.

  In the present embodiment, the rotational axis C of the diameter expanding bit 6 is inclined with respect to the plane including the axis O of the auger shaft 1 as described above. However, the blade edge position of the diameter expanding bit 6 is as described above. For example, the rotation axis C extends in parallel with the axis O if it is located at a position substantially equal to the excavation bit 4 at the tip of the spiral screw 2 in the axis O direction and between the adjacent excavation bits 4 in the circumferential direction. The diameter-expanding bit 6 may be made to expand and contract by rotating in a horizontal plane by a reaction force from the excavation hole. However, in this case, particularly when the diameter-expanding bit 6 is reduced after completion of excavation, the auger shaft 1 must be rotated in the direction opposite to the rotation direction T during excavation to apply a reaction force as described above. Therefore, as in the present embodiment, it is desirable that the rotating shaft C is disposed to be inclined with respect to the axis O, and the diameter-expanding bit 6 is reduced in diameter by its own weight.

  In this embodiment, even if the rotation axis C is inclined with respect to the axis O in this way, the rotation axis C is inclined with respect to the plane including the axis O. The rotation axis C is inclined so as to be along the plane. For example, the rotation axis C is inclined along the plane including the axis O so that the rotation axis C is directed toward the inner peripheral side toward the rear end side in the axis O direction. Even if it is, it is possible to reduce the diameter of the diameter-expanding bit 6 by its own weight. However, in this case, although depending on the inclination angle, there is a possibility that a moment that acts to bend the rotation axis C may be large when the diameter-expanding bit 6 that has been expanded during excavation is advanced while rotating. Therefore, it is desirable that the rotation axis C be inclined to the rotation direction T side toward the rear end side in the axis O direction with respect to the plane including the axis O of the auger shaft 1 as in the present embodiment.

  Even if the rotation axis C is inclined with respect to the plane including the axis O in this way, if the inclination angle θ is too small, the rotation axis C becomes close to a state parallel to the axis O, particularly after the end of excavation. It is difficult to smoothly reduce the diameter of the diameter-expanding bit 6 due to its own weight, and the auger shaft 1 may have to be rotated in a direction opposite to the rotation direction T. On the other hand, when the inclination angle θ is too large, for example, when the rotation axis C is close to a state orthogonal to the plane including the axis O, the diameter-expanding bit 6 is easily reduced in diameter by its own weight, Since it may be difficult to maintain the outer diameter of the diameter-expanding bit 6 at the time of excavation at a predetermined diameter, the inclination angle θ is determined so that the rotation axis C is along the tangential plane as in the present embodiment. When it is inclined, it is desirable that the angle is in the range of 15 ° to 60 °.

  Moreover, although this embodiment demonstrated the case where this invention was applied to the excavation head (earth auger head) of the earth auger which uses the auger shaft 1 with which the spiral screw 2 was provided in the outer periphery as a rotary body as mentioned above, The present invention can also be applied to an excavation head of an excavation tool that discharges excavation waste by, for example, an air lift without providing such a spiral screw. In such a case, the excavation bit 4 may be provided by providing a shank extending from the tip of the rotating body to the outer peripheral side separately from the shank 7 to which the diameter expansion bit 6 is attached.

It is a side view which shows one Embodiment of this invention. It is the bottom view which looked at the embodiment shown in Drawing 1 from the direction of an axis O direction (however, illustration of center bit 5 is omitted). 1 is a side view in the direction of arrow X in FIG. 1 showing a state in which the diameter-expanding bit 6 is reduced in the embodiment shown in FIG. 1 (however, the casing pipe 3, the excavation bit 4, and the center bit 5 are not shown) Abbreviated). FIG. 2 is a side view as viewed in the direction of arrow Y in FIG. 1 showing a state in which the diameter expansion bit 6 has expanded in the embodiment shown in FIG. 1 (however, the spiral screw 2, casing pipe 3, excavation bit 4, and center bit) 5 is not shown.) FIG. 1A shows a diameter-expanding bit 6 of the embodiment shown in FIG. 1. FIG. It is.

Explanation of symbols

1 Auger shaft (rotating body)
2 Spiral screw 3 Casing pipe 4 Drilling bit 4
6 Expanding bit 7 Shank 8 Holder 9 Recess 10 Mounting hole 11 Mounting shaft 13 Tip of the expanding bit 6 A axis of the auger shaft C Rotating axis of the expanding bit 6 T Rotating direction of the auger shaft 1 during excavation θ Rotating shaft C The angle of inclination with respect to the plane containing the axis O

Claims (6)

  A drilling head provided at a distal end portion of a rotating body that is rotated around an axis during excavation, the drilling bit disposed on the outer peripheral side of the distal end portion of the rotating body, and the axial direction with respect to the drilling bit in the axial direction In the circumferential direction around the axis at substantially the same position, it is arranged at a position between the excavation bits adjacent in the circumferential direction, and is rotatable around a rotation axis away from the axis to the outer peripheral side. An excavation head comprising: an expansion bit whose outer diameter from an axis can be increased or decreased.   The excavation head according to claim 1, wherein a spiral screw is provided on an outer periphery of the rotating body.   The blade tip of the diameter-expanding bit in a state where the outer diameter is expanded is positioned closer to the rear end side in the axial direction than the blade tip of the excavation bit. The excavation head according to 2.   The rotating shaft is inclined so as to be directed toward the rotational direction when excavating the rotating body as it goes toward the rear end side in the axial direction with respect to a plane including the axis. The excavation head according to claim 3.   The excavation head according to claim 4, wherein an inclination angle of the rotation shaft with respect to a plane including the axis is in a range of 15 ° to 60 °. The blade tip of the diameter-expanding bit in a state where the outer diameter is reduced is positioned closer to the tip end side in the axial direction than the blade tip of the excavation bit. The drilling head according to any one of the above.

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