JPH0441891A - Retract bit - Google Patents

Abstract

PURPOSE:To improve the efficiency of drilling work by constituting a double- pipe drilling device from a case having a plurality of circular holes and mounted to a drill rod in such a manner as to be attachable and removable and a bit rotatably fitted to the circular holes and having chips planted thereon. CONSTITUTION:A double-pipe drilling device 10 is installed to a rotary percussion drill, a drill rod 11 is positively rotated to extend the diameter of a bit 1, and excavation is performed until an overburden 20 is passed through. When the bit 1 reaches a base rock 21, the drill rod 11 is reversely rotated to contract the bit 1 diameter, and the drill rod 11 and the bit 1 are pulled up. The bit 1 is exchanged with a base rock excavating bit 22, and the drill rod 11 is again inserted to excavate the base rock to a determined depth. Thereafter, the pipe is pulled, and the excavation is completed. As the bit 1 is formed in such a manner as to be capable of extending and contracting, the bit 1 can be exchanged without pulling up an outer pipe 13.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a retract pit installed in a percussion drill or a down-the-hole drill.

E. Prior Art] Conventionally, when drilling using this type of ground excavation drill, especially in collapsible ground, the soil on the inner wall of the drill hole collapses and clogs the drill rod or bit, causing so-called jamming. Ta.

Therefore, we installed an outer tube with approximately the same diameter as the bit as a drill rod (inner tube).
A double-pipe excavation device was developed in which the outer pipe prevents soil from collapsing and entering.

[Problems to be Solved by the Invention] However, in conventional double-pipe drilling equipment, the bit and the outer pipe have approximately the same diameter, so when the bit needs to be replaced due to wear during drilling, the drill rod cannot be replaced. As well,
Work efficiency was poor because the outer tube had to be pulled up as well.

The present invention has been made in view of the above circumstances, and an object of the present invention is to make the bit expandable and retractable so that the bit can be replaced by pulling up only the drill rod, and to provide a tract pit.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a bit that is removably attached to the tip of a drill rod, the bit comprising a case and a bit body, The case is removably attached to the drill rod and has a plurality of circular holes drilled axially symmetrically, and the bit body is divided axially symmetrically into a plurality of divided bodies with tips implanted on the front surface. and a pivot that projects at an eccentric position on the back surface of the divided body and is rotatably fitted into the circular hole.

[Function] When the bit rotates in a predetermined direction, each divided body rotates in a certain direction around the pivot due to frictional resistance with the ground, and the bit as a whole assumes a shape with its maximum diameter expanded. When the bit rotates in the opposite direction, each segment rotates in the opposite direction due to frictional resistance with the soil, and the bit as a whole assumes a shape with its maximum diameter reduced.

[Embodiment] FIGS. 1 to 4 show an embodiment of the glue tract bit (hereinafter abbreviated as bit) of the present invention, and as shown in FIG. (Inner pipe) 11
A case 12 is screwed onto the tip.

The bit 1 is axially symmetrically divided into three divided bodies 2, and a pivot 3 having a circular cross section is integrally formed at an eccentric position on the base end side (back surface) of each divided body 2. Each of the pivots 3 is rotatably fitted into three circular holes 4 provided in the case 12. In addition, a ring-shaped groove 5 having a semicircular cross section is formed on the rear circumferential surface of each pivot shaft 3, and a pair of lock pins 6 attached to three locations on the case 12 are engaged with the groove 5, respectively. It matches.

Each of the divided bodies 2 is formed into the same substantially fan-shaped shape, and when the bit l rotates in the direction B (counterclockwise) as shown in FIG. However, when rotating in the opposite direction (clockwise) as shown in Fig. 1, each divided body 2 rotates counterclockwise around the pivot 3 due to the frictional resistance between the excavated ground and the tip 7. , the bit 1 as a whole maintains a shape with its maximum diameter expanded.

In addition, in FIG. 5, 13 is an outer pipe, 14 is a cleaning swivel which is a joint between the drill rod 11 and the outer pipe 13, and 15 is a water supply port that supplies water to the excavation part through the drill rod 11 and the inner hole of the case 12. , 16 is a discharge port for slime rising between the drill rod 11 and the outer tube 13.

Therefore, the case where the double pipe drilling device 10 is attached to a rotary percussion drill for drilling will be explained with reference to FIGS. 6a to 6g. First, the drill rod 11, that is, the bit 1, is rotated in the direction shown in FIG. The drill rod 11 is rotated in the opposite direction and the drill rod 11 is rotated in the opposite direction to drill the drill rod 11 until it penetrates the overburden (earth layer that is prone to collapse) 20 (Figures 6a and 6b).
Reduce the bit diameter as shown in the figure and pull up the drill rod 11 and bit 1 (Figure 6C).

Figure 6d).

Next, the bit 1 is replaced with the bit 22 for rock excavation, the drill rod 11 is inserted again, and the rock 21 is excavated to a predetermined depth (Figures 6e and 6f). Extubate the tube and complete the excavation.

In the above embodiments, the bit of the present invention is applied to a percussion drill, but it is of course also possible to apply it to a down-the-hole drill.

[Effects of the Invention] As explained above, according to the present invention, it is possible to drill a large diameter hole by enlarging the diameter of the bit during excavation, and by reducing the diameter of the bit when replacing the bit. Since it is only necessary to pull up the drill rod without pulling up the outer tube, Figure 1 is an enlarged front view showing one embodiment of the impact retract bit of the present invention, and Figure 2 is an enlarged front view of the same.
Front view of the II small time, Figure 3 is the same, longitudinal sectional view of the main part, Figure 4
The figure is a cross-sectional view taken along the rV-TV line in Figure 3, Figure 5 is a longitudinal cross-sectional view of the double pipe excavation sub-equipment, and Figures 6a to 6g are procedural explanatory diagrams showing an example of the excavation method using the same equipment. It is.

1... Retract pit, 2... Divided body, 3...
Axis, 11...Drill rod, 12...Case, 1
3...Outer tube, 30...Bit body.

Patent applicant: Koken Kogyo Co., Ltd. Figure 4

Claims (1)

[Claims] (1) A bit that is removably attached to the tip of a drill rod, and the bit includes a case and a bit body, and the case is removably attached to the drill rod and is used for drilling axially symmetrically. The bit body has a plurality of circular holes that are axially symmetrically divided and have a plurality of divided bodies in which chips are implanted on the front surface, and a plurality of divided bodies that protrude at an eccentric position on the back surface of the divided body, and have a plurality of divided bodies that are arranged in the circular holes. A retract bit characterized by comprising a pivot shaft that is rotatably inserted.