JP2001020651A - Drill bit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the diameter of a bit body without reducing drilling capacity in a stepped drill bit to be installed at the tip of a rock drill and a self- drilling rock bolt or the like and having a leading bit section having a small diameter at the front end section of the bit body. SOLUTION: In the two stage drill bit, in which a plurality of blade bodies 2c are implanted radially to the front end face side and which is composed of bit bodies 2 having large diameters, in which an internal hollow section 2e functions as a connecting section with a rotary rod for a rock drill or the like, and a leading bit section 3 having a small diameter projected from the central section of the front end face of the bit bodies 2, through-holes 2d communicated with the front end face sides of the bit bodies 2 from the internal hollow section 2e, and cutting dust is discharged efficiently to the rear by ejecting a pressure fluid such as air, waster or the like from the through-holes 2d in the case of drilling. Since an ejection hole is not required in the leading bit section 3, the bit body 2 can be miniaturized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drill bit used by being attached to the tip of a rock drill or a self-drilling rock bolt, for example, and more particularly to a stepped drill having a small diameter leading portion provided at the front end of a bit body. Perforated bits.

[0002]

2. Description of the Related Art Conventionally, as such a stepped piercing bit represented by a parent-child bit, Japanese Utility Model Publication No. 2-42792,
No. 59-98983, No. 47-4883,
Those described in Japanese Utility Model Publication No. 46-13522 and Japanese Utility Model Publication No. 40-9681 are known. The configuration is such that a tapered hole, screw part, etc. are formed at the rear end side as a connecting means with a rotating rod such as a rock drill, etc., and a mountain shape, button shape, etc. made of cemented carbide at the front end surface. Large-diameter bit body (parent bit) in which a plurality of blades are implanted at a predetermined interval from each other
And a small-diameter leading bit portion (child bit) coaxially formed with the central portion of the front end surface and integrally formed or separately protruded by connection, and the leading bit portion further includes a bit body at its tip. And a through hole communicating with the hollow portion of the bit body is provided on the peripheral surface or near the blade body. At the time of drilling, a pressurized fluid such as air or water supplied from a percussion rotary drive device such as a rock drilling machine through the hollow portion of the bit body is ejected from the through-hole, thereby accommodating the drilling. In this case, the dust generated by the drilling is discharged to the rear, and has the advantage that positioning is easy and the straightness is excellent as compared with a drill bit having another shape.

[0003]

By the way, in these prior arts, since the jetting hole of the pressurized fluid is provided in the leading bit portion, it is inevitable to secure the flow path of the leading bit portion. The outer diameter increases, and accordingly, the outer diameter of the bit body on the rear end side also increases. For this reason, there is a limit in reducing the diameter as compared with a single-stage single bit, and there is a problem that it cannot be applied to a small-diameter hole. Therefore,
Even if it is only necessary to drill the minimum size hole required for insertion of the lock bolt body, such as a self-drilling lock bolt, it is more than necessary because the outer diameter of the bit attached to the tip is large. Holes of a large size had to be drilled, which increased the amount of work and hindered improvement in workability.

The present invention has been made in view of these problems of the prior art, and retains the advantages of a stepped drill bit which is accurate and easy to position at the time of drilling and is excellent in straightness during drilling. The diameter of the entire bit can be reduced,
In addition, it is an object of the present invention to provide a drill bit that discharges fine powder and has excellent drilling ability.

[0005]

According to a first aspect of the present invention, there is provided a drill bit having a large diameter having a hollow shape and a plurality of blades provided at predetermined intervals on a front end face. A bit main body and a small-diameter leading bit part protruding coaxially at the center of the front end face of the bit main body, wherein a through hole is provided between the blade bodies at the front end face of the bit main body. It is.

According to this structure, the leading bit portion is projected from the central portion and a through hole communicating with the inner space is formed in the front end face of the large-diameter bit body on which a plurality of blades are implanted. Since the powder is discharged by a pressurized fluid such as water or air ejected from the through hole, a flow path for the pressurized fluid is not required in the leading bit portion, and its outer diameter is small. Good. For this reason, the outer diameter of the bit main body can be correspondingly reduced while maintaining good dischargeability of the dust.

Further, the invention according to claim 2 is characterized in that an axial groove is provided on the outer peripheral surface of the bit body, and the through hole is opened near the groove. In this case, the powder generated due to the drilling is discharged to the rear of the bit by the injection pressure of the pressurized fluid ejected from the through hole of the bit body. Since the outer peripheral surface has a groove along the axial direction, the injection pressure effectively acts, and the bit is smoothly discharged to the rear of the bit body. In addition,
The groove portion of the bit body may be provided in another portion in addition to the vicinity of the through hole, and the number and shape thereof are not particularly limited.

In the invention according to a third aspect of the present invention, the leading bit portion has a substantially cylindrical shape, and a distal end portion including the blade body is formed in a wedge-shaped tapered surface, and is connected to each of the tapered surfaces. A notch is provided on the peripheral surface to be formed, and the through hole is opened near the notch. In this configuration, a gap is always formed between the outer peripheral surface of the leading bit portion and the inner peripheral surface of the drilled hole due to the presence of the notch provided on the peripheral surface of the leading bit portion. Since the tapered surface having the blade body as the apex exists in front of the blade, the supply of the pressurized fluid to the blade body provided at the tip is reliably performed, which effectively contributes to the discharge of the dust. The cutout may be flat or grooved, for example.

According to a fourth aspect of the present invention, the through hole is opened obliquely outward with respect to the axis of the bit body. The pressurized fluid ejected in the direction draws powder generated on the front surface of the bit main body toward the peripheral surface side of the drill hole, and effectively acts to discharge backward from between the peripheral surface of the bit main body.

[0010]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. 1 to 3 show a first embodiment of a drill bit according to the present invention, and are a front view, a plan view and a sectional view, respectively.
The illustrated drill bit 1 is a two-stage so-called parent-child bit composed of a large-diameter bit main body 2 and a small-diameter leading bit portion 3 protruding coaxially at the center of the front end face side thereof. The bit main body 2 and the leading bit portion 3 can be integrally formed by, for example, casting.

The bit main body 2 has a generally cylindrical shape having a bottom surface portion on one side as a whole, and the outer diameter of an end portion 2a on the bottom surface side is formed somewhat larger than that on the other end side. Then, on the outside of the bottom surface, that is, on the front end side, FIG.
As shown in FIG. 4, four kerfs 2b are formed radially at intervals of 90 degrees so as to surround the leading bit portion 3 described in detail later, and a mountain-shaped cemented carbide is formed inside each kerf 2b. The blade body 2c made of is implanted by brazing. Also, the leading bit portion 3 among the four blade bodies 2c is provided.
At two positions opposite to each other, a through hole 2d is opened at an intermediate position between the blade bodies 2c, that is, at a position 45 degrees away from the blade body 2c, and the through holes 2d are formed as shown in FIG. The body 2 communicates with the inner space 2 e in an inclined state with respect to the axis of the body 2. In the embodiment, the inner peripheral surface of the inner space 2e is formed in a rope screw shape, and is used for connection with a lock bolt main body or the like. Furthermore, the bottom end 2 of the bit body 2
In the outer peripheral surface of a, four grooves 2f are provided along the axial direction at an intermediate position between the blade bodies 2c as in the case of the through-hole 2d, and the through-hole 2d is formed at the front end side of the groove 2f. At the opening.

On the other hand, the leading bit portion 3 is solid and substantially columnar as a whole, and has a mountain-shaped blade 3a made of the same material as the blade 2c of the bit body 2 at the tip thereof. The blade is implanted so as to have a length substantially the same as the diameter of the blade and orthogonal to a line connecting the centers of the two through holes 2d, and is substantially the same as the blade following the blade surface so as to sandwich the blade body 3a. An angled tapered surface 3b is formed, and the leading end of the leading bit portion 3 is formed in a shape close to a wedge. further,
On the outer peripheral surface of the leading bit portion 3, one flat notch 3c is provided in parallel with each other so as to be connected to each of the tapered surfaces 3b, and as shown in FIG. The end side is close to the through hole 2d of the bit body 2, and the groove portion 2f and the through hole 2d are respectively arranged on both sides of the blade body 3a.
The center of the notch 3c is substantially aligned with the center. In addition, it is preferable that the amount of protrusion of the leading bit portion 3 is not too long from the viewpoint of supplying the pressurized fluid to the blade body 3a located at the tip thereof.

As described above, in the drill bit 1 according to the present invention, the pressurized fluid jetting port is provided on the front end face of the bit main body 2, so that the flow path of the pressurized fluid is not required inside the leading bit portion 3. As a result, the outer diameter of the leading bit portion can be reduced as compared with the conventional parent-child bit, and as a result, the outer diameter of the bit body can be correspondingly reduced. Therefore, for example, when the drill bit 1 is applied to a self-drilling lock bolt, it is only necessary to form a hole having a minimum size necessary for insertion of the lock bolt main body, which is close to the outer diameter of the lock bolt main body. By selecting the drill bit 1 having a small outer diameter, the efficiency of the drilling operation is improved while maintaining the characteristics of the parent and child bits. in this case,
If the supply amount of the pressurized fluid is the same, the dischargeability of the milling powder is increased by the smaller the hole diameter. Furthermore, since the through-hole 2d is provided in the front end face of the large-diameter bit main body 2, compared with the conventional example in which the through-hole is formed in the small-diameter leading bit portion, the through-hole which affects the dischargeability of the dust is reduced. The degree of freedom in selecting the opening area and its position is increased. Incidentally, the bit diameter of about 60 mm is the minimum in the conventional parent-child bit, but by providing the through hole 2 d in the end face of the bit body 2 as in the present invention,
The bit diameter, which was difficult with conventional parent-child bits, is 40-5
It is possible to manufacture a material having a hole diameter of about 5 mm and having the same drilling ability.

Next, the use state of the drill bit 1 of the above embodiment will be described. For example, this drill bit 1 can be made into a self-drilling lock bolt by being mounted on a hollow full-thread lock bolt body in which a rope screw is formed over the entire outer peripheral surface. In this case, the bit body 2
Is fitted to a lock bolt main body (not shown) via the inner space portion 2e. At the time of use, the rear end side of the lock bolt body is attached to a shank adapter or the like of a rock drill, and the rock is drilled by the rotation and impact force. In addition, a compressor is connected to the rock drilling machine so that pressurized air or water can be supplied to the lock bolt main body through the hollow portion of the shank adapter. Then, these pressurized fluids reach the inside of the drill bit 1 through the hollow portion of the lock bolt main body, and are further jetted forward from the through hole 2d. The pressurized fluid jetted to the front surface of the bit main body 2 reaches the blade 3a at the tip from two notches 3c existing on the outer peripheral surface of the leading bit portion 3 via the tapered surface 3b, and the generated fluid is generated there. The powder can be efficiently discharged to the rear and perforated in a highly accurate straight state while effectively preventing the runout of the perforated bit 1. Further, the powder dust shaved by the blade body 2c of the bit body 2 is brought close to the inner circumferential surface of the drilled hole by the pressurized fluid, and then passes through the groove 2f provided on the outer circumferential surface of the bit body 2 to the rear. Is discharged. In this case, since the groove 2f exists near the through hole 2d, the injection pressure effectively acts, and the discharge property is good. When the drilling is completed, the inside of the hole is washed, and then the grout material is appropriately injected using the same channel to fill the hole.

In the above-mentioned embodiment, as the connecting means for the rotating rod of a rock drill or the like in the bit main body 2, the inner space 2e is formed as a tapered hole instead of a rope screw, or the outer peripheral surface of the bit main body 2 is provided. It is of course possible to appropriately change such as forming an external thread according to the use conditions and the like.

FIG. 4 is a plan view showing another embodiment of the drill bit according to the present invention. In this drill bit 10, the individual shapes of the bit body 11 and the leading bit portion 12 are the same as those in the above-described embodiment, except that the relative positions of the two are shifted by 45 degrees. The blades of the leading bit portion 12 are arranged in a cross shape. In this case, since the through hole 11a of the bit main body 11 and the tapered surface 12a of the leading bit portion 12 are farther than that of the above-described embodiment, the discharge of the dust is somewhat reduced. On the other hand, when the bit main body and the leading bit portion are integrally formed by casting, there is an advantage that this shape is easier to manufacture.

In each of the above embodiments, two through holes have been described. Of course, one or three or more holes may be provided, and the opening position on the front end face of the bit body may be different from the shape, size, It can be appropriately selected according to the number and the like. Further, the shape of the blade body may be a button shape other than the mountain shape, and there is no problem even if the shape of the blade body of the leading bit portion and that of the bit body are different. Further, various modifications within the technical concept of the present invention are possible, such as one in which the bit body and the leading bit part are separate, two or more bits in the bit body, and application to a bit of a drilling machine. .

[0018]

As described above, in the drill bit according to the first aspect of the present invention, a through hole is opened only at the front end face of the bit body instead of the conventional leading bit portion, and the through hole is ejected from the through hole. Since the powder is discharged by the pressurized fluid, the drilling ability is greatly affected while maintaining good positioning accuracy and straightness, which are the characteristics of the stepped bit called the conventional parent-child bit. It is possible to reduce the diameter of the entire bit without reducing the dischargeability of the dust.
For this reason, for example, in a drilling operation such as a self-drilling lock bolt for the purpose of merely inserting, a hole having a minimum diameter may be formed without performing extra drilling, leading to an improvement in working efficiency.

Further, in the above structure, a groove in the axial direction is provided on the outer peripheral surface of the bit body, and a through hole is opened near the groove,
The leading bit portion is formed in a substantially cylindrical shape, and the tip end portion including the blade body is formed in a wedge-shaped tapered surface, and a notch is provided in a peripheral surface connected to each tapered surface, and a through hole is formed near the notch. In both cases, such as when the opening is formed or the through-hole is formed obliquely outward with respect to the axis of the bit body, there is a great effect in improving the dischargeability of the dust generated during drilling.

[Brief description of the drawings]

FIG. 1 is a front view showing an example of a drill bit according to the present invention.

FIG. 2 is a plan view of the drill bit.

FIG. 3 is a sectional view taken along line AA in FIG. 2;

FIG. 4 is a plan view showing another example of a drill bit according to the present invention.

[Explanation of symbols]

1,10 ... perforated bit, 2,11 ... bit body, 3,1
2 Lead bit portion 2c, 3a Blade body, 2d, 11a
Through holes, 2e: inner space, 2f: groove, 3b, 12a: tapered surface, 3c: notch

Claims (4)

[Claims] 1. A large-diameter bit body having a plurality of blades provided at predetermined intervals on a front end face thereof, formed in a hollow shape, and a small-diameter projecting coaxially at the center of the front end face of the bit body. Wherein a through hole is provided between the blades on the front end face of the bit body. 2. The perforated bit according to claim 1, wherein the outer peripheral surface of the bit body has a groove in the axial direction, and the through hole is opened near the groove. 3. The leading bit portion has a substantially cylindrical shape, a tip end portion including a blade body thereof is formed in a wedge-shaped tapered surface, and a notch is provided in a peripheral surface connected to each tapered surface. The perforation bit according to claim 1 or 2, wherein the through-hole is opened near the notch. 4. The perforated bit according to claim 1, wherein the through-hole is opened obliquely outward with respect to the axis of the bit main body.