JP3075108B2 - Expanding bit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention is applicable to foundation works in civil engineering construction, pillar construction work, or drilling work.
It relates to an enlarged bit used for underground excavation.

[0002]

2. Description of the Related Art A conventional example of the above-mentioned enlarged bit is disclosed in Japanese Patent Publication No. 51-25401. As shown in FIG. 11, the diameter-enlarged bit includes two drilled portions, that is, a bit 2 of a concentric portion connected to a drill rod 1 and a bit of an eccentric portion rotatable between a projecting and retracting position. 3 shows an enlarged diameter bit in which 3 is engaged with the shaft 4 of the bit 2 of the concentric portion.

[0003] This enlarged diameter bit has an advantage that the rotatable eccentric bit is fitted to the shaft portion of the concentric tip bit, so that the components are small and the structure is simple.

[0004]

However, in this enlarged diameter bit, since the rotatable eccentric bit 3 has a protruding portion and a gap for the rotatable movement between the eccentric bit 3 and the tip bit 2, the portion has a large amount of earth and sand. Eccentric bit 3
May not be able to be recovered due to inability to rotate, or the eccentric bit 3 is fitted to the shaft 4 of the tip bit 2 concentric with the drill rod 1, so that the thickness cannot be increased and the wall becomes thin. There was a problem that an accident such as cracking due to the impact during excavation, breakage and falling off occurred.

[0005] The present invention has been made in view of the above circumstances,
It is an object of the present invention to provide a simple and highly rigid diameter-enlarged bit by directly inserting an eccentric bit into a tip concave portion of a drilling tool body.

[0006]

In order to achieve the above object, according to the first aspect of the present invention, there is provided a coaxial shaft having a diameter larger than the shaft diameter at the base of a shaft provided at the lower portion of a bit head provided with a cutting blade. And a small-width convex portion protruding from the step portion toward the shaft side is provided. On the other hand, a bit shaft fitting hole provided in the large-diameter bit support is provided with a shaft center of the large-diameter bit support. Eccentrically provided, and at the upper end of the shaft fitting hole, a counterbore portion is provided to engage with the step portion, and at the lower portion of the counterbore portion, a relief portion is provided so that the projection can rotate. When the bit is rotated, the projecting portion is formed so as to be positioned at the wall of the sloping portion and excavated with a required bit diameter. The invention according to claim 2 is characterized in that when the eccentric bit is rotated in the reverse direction, the excavating blade is reduced in diameter and the wall is formed at a position opposite to the squeezed portion so that the convex portion is positioned at a position where the diameter becomes the minimum. It is characterized by having been provided.

[0007]

As described above, since the rotating portion of the diameter-enlarging bit is stored in the inside of the excavating tool body, the excavating blade can be expanded without being bothered by excavated earth and sand or gravels despite the simple configuration. The operation of diameter and diameter reduction can be performed smoothly.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The enlarged bit according to the present invention will be described in detail with reference to FIGS. 1 to 10 which show an embodiment. The enlarged bit 5 is composed of a bit head 6 having an excavation blade 8 and a shaft 7. The center of the head 6 is set at the same position as the center of the diameter-enlarged bit support, but the axis of the shaft 7 is offset from the center of the head 6 by A dimension. It is rotatably fixed to the shaft fitting hole 10 provided in the diameter-enlarged bit support 9 by a well-known retaining means 21 so as not to come out. At the base of the shaft 7, there is provided a cylindrical step 11 having a coaxial diameter larger than the diameter of the shaft, and a small-width projection 12 projecting from the step 11 toward the shaft. The shaft fitting hole 10 is provided so as to be eccentric from the shaft center of the support 9 by a required size A according to the diameter expansion of the excavating blade 8, and a counterbore into which the step portion 11 is fitted at the upper end of the hole 10. A part 13 is provided.
At the lower part of the counterbore 13, a recess 14 having the same diameter as that of the counterbore 13 is provided within a range of 120 ° to 270 °, and the projection 12 is turned within the range of the counterbore 14. In addition, walls 15 and 16 serving as stoppers for stopping the rotation of the convex portion 12 are provided at both ends of the slack portion 14. The diameter of the digging blade 8 of the diameter-enlarged bit 5 is set to be maximum when the projection is rotated at the position of the wall 15 by rotating in the squeezed portion 14. When the convex portion 12 is reversely rotated and positioned at the position of the wall 16 provided at the opposite end, the tip of the excavating blade 8 of the enlarged bit 5 has a smaller diameter than the outer diameter of the enlarged bit support 9. It is formed so that there is no problem when the diameter-enlarged bit support 9 is pulled up inside the pipe 17.

In order to discharge the excavated earth and sand, holes 19 provided in the shaft 7 of the enlarged diameter bit 5 are communicated with a plurality of water holes 20 provided so as to jet toward the head 6. Further, it is configured to communicate with a water hole 18 provided near the center of the diameter-enlarged bit support 9 so that pressure is applied to the excavated portion.
The excavated earth and sand is discharged from a gap provided between the outer peripheral surface of the diameter-enlarged bit support 9 and the inner peripheral surface of the pipe 17 by the pressure ejected from the water hole 20.

[0010]

As described above, according to the present invention, the shaft 7 provided below the bit head 6 provided with the excavating blade 8 is provided.
At the base of the shaft, there is provided a coaxial column-shaped step portion 11 formed to have a diameter larger than the shaft diameter, and a shaft 6 from the step portion 11.
A small-width convex portion 12 protruding to the side is provided, while a bit shaft fitting hole 10 provided in the enlarged-diameter bit support 9 is provided eccentrically by A dimension from the axis of the enlarged-diameter bit support 9. A counterbore 13 for engaging with the step 11 is provided at an upper end of the fitting hole 10, and a recess 14 is provided at a lower portion of the counterbore 13 so that the protrusion can be rotated. Is rotated, the convex portion 12 is positioned by the wall 15 provided on the sloping portion 14, so that it can be excavated with a required bit diameter during the rotational driving, and the excavation is completed and the enlarged bit support 9 is removed. When rotated in reverse, the enlarged bit 5
Of the excavating blade 8 is positioned so as to be accommodated inside the outer diameter of the enlarged-diameter bit support 9 by being moved by the wall 16 provided on the opposite side of the recessed portion. It has excellent advantages such as a small-sized component and a simple structure.

[Brief description of the drawings]

FIG. 1 is a side sectional view showing one embodiment of the present invention.

FIG. 2 is a front view of FIG. 1, showing a state in which the diameter of a diameter-enlarging bit is maximum.

FIG. 3 is a front view of FIG. 1 showing a state where the diameter of the diameter-enlarging bit is minimum.

FIG. 4 is a side view of the single diameter expanding bit shown in FIG. 1;

FIG. 5 is a rear view of the diameter expanding bit shown in FIG. 4;

FIG. 6 is a perspective view of a shaft part of FIG. 4;

FIG. 7 is a top sectional view of the enlarged bit support shown in FIG. 1;

FIG. 8 is a front view of FIG. 7;

FIG. 9 is a perspective view of FIG. 7;

FIG. 10 is a sectional view taken along line CC of FIG. 8;

FIG. 11 is a sectional view showing a conventional example.

[Explanation of symbols]

 A Eccentric dimension 1 Drill rod 2 bits 3 bits 4 Bit 2 shaft 5 Expanded bit 6 Bit head 7 Shaft 8 Drilling blade 9 Expanded bit support 10 Shaft fitting hole 11 Stepped portion 12 Convex portion 13 Counterbore DESCRIPTION OF REFERENCE NUMERALS 14 Slack portion 15 Wall 16 Wall 17 Pipe 18 Water hole 19 Water hole 20 Water hole 21 Retaining means

Continuation of the front page (56) References JP-A 4-77688 (JP, U) JP-A 5-3392 (JP, U) (58) Fields surveyed (Int. Cl. ⁷ , DB name) E21B 10 / 32

Claims (2)

(57) [Claims] An eccentric diameter-expanding bit in which a shaft portion of a bit is rotatably fitted in a bit shaft fitting hole of a diameter-enlarged bit support, wherein a shaft provided at a lower portion of a bit head provided with an excavation blade is provided. At the base, a coaxial cylindrical step formed with a diameter larger than the shaft diameter is provided, and a small-width protrusion protruding from the step to the shaft side is provided. A joint hole is provided eccentrically from the axis of the diameter-enlarged bit support, and an upper end of the shaft fitting hole is provided with a counterbore for engaging with the step portion, and a lower portion of the counterbore is provided with the convex. A slack portion is provided so that the portion can rotate, and when the bit is rotated, the convex portion is formed so as to be positioned on the wall of the slack portion and excavated with a required bit diameter. Expanding bit. 2. A wall is provided at a position opposite to the squeezed portion so that when the eccentric bit is rotated in the reverse direction, the excavating blade is reduced in diameter and the convex portion is positioned at a position where the diameter becomes the minimum. The diameter expanding bit according to claim 1, wherein: