JP2543575Y2 - Lock bit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a lock bit having a number of button-shaped cutting blades provided on a bit head.

"Conventional technology" Rock bits were originally used to drill holes for blasting in rock, but large bits exceeding 200 mm in diameter are often used for drilling foundation piles in buildings. It has become so. Therefore, the target stratum is not only the bedrock, but also the stratum near weathered rocks or partly gravel.

As shown in FIGS. 3 and 4, the lock bit used for this purpose includes a number of button-shaped cutting blades (mainly made of cemented carbide) 2 on the tip end surface 1a of the bit head 1.
There is known a so-called button bit in which is embedded (see Japanese Patent Publication No. 45-10401).

[Problem to be Solved by the Invention] However, when the soft ground is perforated by the above-mentioned conventional lock bit, the steel body holding the cemented carbide tip, which is a blade body, rather than the wear thereof, especially the head, is used. The outer peripheral portion 1b is significantly worn (indicated by reference numeral 3 in FIG. 4), and the button-shaped blade 2 comes off due to the wear of the base metal, making it almost unusable.

Various methods have been proposed to improve the wear resistance of the outer peripheral portion of the bit head.
Debris that enters into the slight gap between the hole wall 4 and the bit head outer peripheral portion 1b causes the steel body having poor wear resistance to wear preferentially over the button-shaped cutting blade, and the above-mentioned unusable state is caused. turn into. In order to discharge the perforated debris backward, a bit groove extending in the axial direction is provided on the outer peripheral portion of the bit head, but this groove alone is not sufficient.

For this reason, conventionally, the outer peripheral surface of the head is subjected to surface quenching or hard metal is buried, while a pressurized air outlet is provided in this portion to prevent intrusion of debris as a high pressure part. However, in any case, it is impossible to prevent mixing of debris into the small gap between the hole wall 4 and the bit head 1, and it is impossible to prevent a high grinding force due to the debris entering the gap.

In order to solve the above problem, it is only necessary to eliminate the gap at all. However, in practice, the bit rotates, and it is not possible to make the rotation accuracy as high as that of the axis of the machine tool. It is possible.

The present invention has been made in view of the above circumstances, and its purpose is to provide a large gap between the hole wall and the outer peripheral portion of the bit head in advance so that, for example, debris may enter during this time. However, it is still another object of the present invention to provide a lock bit that can flow smoothly, can prevent generation of a large grinding force due to debris, and can reliably prevent wear of the bit head.

"Means for Solving the Problems" In order to achieve the above object, the present invention provides a lock bit provided with a number of button-shaped cutting blades at the tip end surface of the bit head, the outer peripheral surface of the bit head. A large number of substantially hemispherical projections are provided so as to protrude outward from the implanting blade.

[Operation] In the lock bit of the present invention, a projection is provided on the outer peripheral surface of the bit head so as to protrude more outwardly than the cutting blade on the tip surface, so that the hole wall drilled by the cutting blade on the tip surface. Is further expanded, thereby securing a large clearance between the hole wall and the outer peripheral surface of the bit head. Furthermore, since the projections are substantially hemispherical, debris that enters between the rock wall to be drilled and the outer peripheral surface of the head will flow smoothly without delay by the substantially hemispherical projections, There is no danger of wearing the head.

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

In these figures, reference numeral 10 denotes a bit main body, and the bit main body 10 is made of substantially columnar steel, and includes a head 10a for drilling a rock or the like, and a mounting portion 10b having a smaller diameter than the head 10a. ing. The head 10a is formed to have a larger diameter toward the distal end. Also,
Eight cutting grooves 11 are formed at equal intervals on the outer peripheral portion of the head 10a. Of these, every other four cutting grooves 11 have a total of four cutting grooves 11 at the tip end surface of the head 10a. Groove 1 extending to the center
2 are formed. A jet hole is provided between the groove 12 and the center hole 13 formed inside the bit body 10.
14 and 15 are formed two by two in a point symmetry with respect to the axis of the bit body 10. The opening positions of the ejection holes 14 and 15 to the tip end face of the head 10a are set such that the ejection hole 14 has a longer distance from the tip end surface center than the ejection hole 15 and
The straight line connecting the fourteen openings and the straight line connecting the openings of the ejection holes 15 are set to intersect at right angles. Further, a large number of hemispherical implants (button tips) 16 are dispersedly embedded in the distal end surface of the head 10a. Further, a large number of hemispherical projections (button chips) 17 are provided on the outer peripheral surface 10c of the head 10a so as to protrude more toward the outer peripheral side of the bit body 10 than the implanting blade 16 as shown in FIG.
Is embedded. And these button chips 1
6, 17 are the same shape and are made of cemented carbide.

The protrusions 17 are formed of a cemented carbide in consideration of wear resistance. Regarding the protrusion amount, if the protrusion amount is too large, the strength is insufficient, and it is easy to break, and if the protrusion amount is small, the hole wall and the outer peripheral surface are small. The gap between them becomes narrower, and a larger grinding force is generated on the invading debris, which is less effective. Therefore, specifically, about 3 to 15 mm is a range in which good results can be obtained.

According to the lock bit configured as described above, at the time of drilling, the hole wall of the rock to be drilled and the head 10a of the bit body 10
Sufficient clearance is secured by the projection 17 between the outer peripheral surface 10c and the outer peripheral surface 10c. Therefore, the hole wall and the head 10a of the bit body 10
Even if debris intrudes in between, the fluid flows smoothly, no large grinding force is generated, and wear of the head 10a is reliably prevented.

"Effects of the Invention" As described above, the present invention is provided with a large number of substantially hemispherical projections on the outer peripheral surface of the bit head so as to protrude to the outer peripheral side from the implanted blade provided on the tip end surface. Therefore, these projections expand the diameter of the hole wall drilled by the cutting blade, thereby securing a large clearance between the hole wall and the outer peripheral surface of the bit head. Even so, it can flow smoothly and can prevent the generation of large grinding force due to rock debris, and can surely prevent wear of the bit head, without causing the blade to fall off, Therefore, it is possible to stably pierce for a long time.

[Brief description of the drawings]

1 and 2 show one embodiment of the present invention.
Fig. 2 is a front view, Fig. 2 is a side view, Figs. 3 and 4 show a conventional lock bit, Fig. 3 is an explanatory view showing a perforated state, and Fig. 4 is an explanation of a bit body head. FIG. 10 ... bit body, 10a ... head, 10c ... outer peripheral surface, 16 ...
… Planting blades, 17 …… projections.

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-B-54-35561 (JP, B2)

Claims (1)

(57) [Scope of request for utility model registration] 1. A lock bit having a plurality of button-shaped cutting blades provided on a tip end surface of a bit head, wherein a substantially hemispherical shape is formed on an outer peripheral surface of the bit head so as to protrude outward from the cutting blade. A lock bit having a large number of projections.