The present invention relates to a non-core drill bit for boring concrete, cement mortar, building blocks and others.
For example, where an outdoor unit of an air conditioner is mounted to a concrete wall, the concrete wall is first bored, anchor bolts are mounted into the thus bored holes, and the outdoor unit is fixed to the anchor bolts with screws.
As a boring tool for making the above-described bored holes, there is known a hammer drill and a diamond drill. The hammer drill is a tool for hammering and boring the concrete wall, while a carbide tip of a bit is pierced to break the wall. However, this tool causes troublesome hammering noise.
On the other hand, the diamond drill is a tool in which a diamond grindstone body is fixed to the tip of a base constituting a seat, making a hole by firmly pressing a rotating bit against the concrete wall and cutting the surface thereof. Therefore, this tool is advantageous in lower working noise.
Incidentally, the diamond drill must continue to constantly press a bit attached to the tip thereof, thereby generating high heat resulting from frictional heat. Thus, there is generally used a wet-type diamond drill which allows water to flow inside the bit (refer to Patent Documents 1 and 2). However, since this type requires a hole made for allowing water to pass through a center thereof, the bit must be hollow. Therefore, in the case of a core drill bit, it requires, a device for circulating cooling water and also requires means for removing concrete debris (swarf) remaining inside the hollow bit.
In contrast, a dry-type diamond drill, which is free of water, is constituted so that it is at least partially solid, the tip thereof is formed in a flat shape and a diamond grindstone body is fixed on an iron-based seat. The dry-type diamond drill does not require a device for circulating water or means for removing concrete debris. This drill is provided with a slit-like recessed cutout portion opened to one side, and swarf is to be removed outside from the recessed cutout portion.
However, a conventional non-core drill bit (hereinafter, simply referred to as a bit) has the following disadvantages.
(1) In
(2) The performance will be improved as a bit wears at the center. However, due to a difference in rotating speed between the outer periphery side and the inner periphery side of the bit, a conically projected portion uncut and remaining develops at the center of the leading end of a hole 15. At the beginning, no problem is found. However, when the outer periphery side wears to decrease in height, and develops into a state shown in
(3) When the boring work is further continued from a state in (2), not only does the boring speed decrease but the diamond grindstone body 21 also lowers in height at the outer periphery portion. At the same time, the outer periphery face of a base 23 (made of iron and free of diamond grains) is more vulnerable to wear than the bit tip, thereby as shown in
One or more embodiments provide a non-core drill bit capable of keeping the boring performance substantially constant from a beginning of use to an end thereof.
According to a first aspect of the present invention, a non-core drill bit is provided with: a metallic seat attached to the tip of a shank of a boring tool; an approximately annular or cylindrical first diamond grindstone body fixed to the metallic seat and having a recessed cutout portion to be opened to one side; and a second diamond grindstone body installed inside the recessed cutout portion, in which the second diamond grindstone body is formed so as to be lower than the first diamond grindstone body.
According to a second aspect of the present invention, in the non-core drill bit of the first aspect, the inner side of the tip face of the first diamond grindstone body is formed in an approximately reverse-conical recessed shape.
According to a third aspect of the present invention, in the non-core drill bit of the first or the second aspect, the height of the second diamond grindstone body is made substantially equal to a minimum height by which the outer periphery face of the first diamond grindstone body is able to provide a straight-forward boring guide.
According to a fourth aspect of the present invention, in the non-core drill bit of the first or the second aspect, the height of the outer periphery face of the first diamond grindstone body remaining when the top portion of a projected portion uncut and remaining in a conical shape at the center of a hole by boring work is in contact with the base is set to be a minimum height capable of providing a straight-forward boring guide.
According to a fifth aspect of the present invention, in the non-core drill bit of any one of the first to the fourth aspect, the first diamond grindstone body is installed as a separate member from the second diamond grindstone body and then formed in an integral manner.
According to the above-described first aspect, the non-core drill bit is provided with a metallic seat attached to the tip of a shank of a boring tool, an approximately annular or cylindrical first diamond grindstone body fixed to the metallic seat and having a recessed cutout portion to be opened to one side, and a second diamond grindstone body installed inside the recessed cutout portion, in which the second diamond grindstone body is formed so as to be lower than the first diamond grindstone body. Therefore, after repetition of boring work, the first diamond grindstone body wears off and the top portion of a conically projected portion uncut and remaining at the center of the tip of a hole will soon be in contact with the second diamond grindstone body. The second diamond grindstone body is installed inside a recessed cutout portion, and it is thereby cut off in a short time due to the fact that the rotating speed is slow and the top portion of the projected portion is accordingly small. As described above, since the second diamond grindstone body can be used to cut the projected portion in an accelerated manner, the boring speed is not decreased. Further, since the projected portion is cut by the second diamond grindstone body, swarf cut by the second diamond grindstone body is similar in appearance to swarf cut by the first diamond grindstone body. Thus, swarf from both can be discharged together without any special procedures. As a result, it is possible to retain substantially the constant boring performance from the beginning of use to the end thereof.
According to the above-described second aspect, the inner side of the tip face of the first diamond grindstone body is formed in an approximately reverse-conical shape. Therefore, the outer periphery edge of the tip face is able to cut well into a material to be bored such as concrete, and the outer periphery side of a bit is also higher in rotating speed, by which the working capability is greater than the inner side which is slower in rotating speed. Therefore, when a non-core drill bit is first pressed against concrete, cutting is started from the outer periphery edge, and the inner periphery side portion lower in working capability is not in contact with the face of the concrete. Thus, it is possible to perform boring at high speed from the beginning of use.
According to the above-described third aspect, the height of the second diamond grindstone body is substantially equal to a minimum height by which the outer periphery face of the first diamond grindstone body is able to provide a straight-forward boring guide. Therefore, it is possible to know the end of use by observing the extent of wear of the second diamond grindstone body in the boring work and also to provide a good straight-forward boring guide even at the end of use.
According to the above-described fourth aspect, the height of the outer periphery face of the first diamond grindstone body remaining when the top portion of a projected portion uncut and remaining in a conical shape at the center of a hole after the second diamond grindstone body wears by boring work is in contact with the base is set to be a minimum height capable of providing a straight-forward boring guide. Therefore, when the projected portion is in contact with a base, the boring speed decreases greatly due to the base which has no boring performance. Further, the exposed face of the base can be clearly visibly recognized. Thus, it is possible to know reliably the timing of the end of using a non-core drill bit. Still further, the outer periphery face of the first diamond grindstone body secures the straight-forward guide even at the time when the bit is completely used and a bored hole will not be deflected until the bit is completely used, thus making it possible to retain appropriately members such as an anchor bolt. It is also possible to keep the second diamond grindstone body to a minimum amount.
According to the above-described fifth aspect, the first diamond grindstone body is installed as a separate member from the second diamond grindstone body. Accordingly, a problem that a projected portion uncut and remaining is changed in shape, depending on whether or not a material to be bored is concrete, cement mortar, or light-weight building blocks which contain stones, and the bit is also accordingly changed in usability is resolved by changing a composition of the second diamond grindstone body based on the material to be bored so as to make it possible to provide an optimal non-core drill bit.
If both the first diamond grindstone body and the second diamond grindstone body are changed in compositions according to a material to be bored, it becomes possible to provide a non-core drill bit optimal for boring.
Other aspects and advantages of the invention will be apparent from the following description, the drawings and the claims.
a) is a plan view of the non-core drill bit.
b) is a front elevational view of the non-core drill bit.
c) is a bottom plan view of the non-core drill bit.
a) is a cross sectional view showing an aspect of attaching a second diamond grindstone body.
b) is a cross sectional view showing an aspect of attaching the second diamond grindstone body.
c) is a cross sectional view showing an aspect of attaching the second diamond grindstone body.
a) is an explanatory diagram of a wear state resulting from the use of a conventional non-core drill bit.
b) is an explanatory diagram of a wear state resulting from the use of the conventional non-core drill bit.
c) is an explanatory diagram of a wear state resulting from the use of the conventional non-core drill bit.
In the above drawings, the numeral 1 denotes a bit. The bit 1 is constituted with a metallic seat 2, a first diamond grindstone body 3 provided on the metallic seat 2, and a second diamond grindstone body 4 provided on the inner side of the first diamond grindstone body 3.
The metallic seat 2 is made of iron and includes an external thread portion 5 on one side of an approximately rectangular-shaped seating portion 2a having a segmental portion on one side thereof and a raised portion 6 on the other side. As shown in
The first diamond grindstone body 3 is formed in a cylindrical shape having a recessed cutout portion 10 opened on the outer periphery face, that is, a sintered body prepared by mixing metal bonded grains (for example, alloy based on copper and tin) with diamond grains and sintering them. A base portion layer 3a of the first diamond grindstone body 3 is a diamond free portion which contains no diamond grains and a diamond containing portion 3b is installed on the tip side of the diamond free portion. Then, the recessed portion 9 is formed at the center of the diamond free portion 3a and fixed by brazing, with the raised portion 6 of the metallic seat 2 fitted into the recessed portion 9. The diamond free portion 3a has no boring capability, and a base 100 is constituted with the diamond free portion 3a and the metallic seat 2.
The diamond free portion 3a of the first diamond grindstone body 3 is that which forms at the center thereof a recessed portion 9 for being fitted into the raised portion 6 of the metallic seat 2, enlarging a contact area between the metallic seat 2 and the diamond grindstone body, thereby the first diamond grindstone body 3 is less likely to be peeled from the metallic seat 2. Therefore, this is not necessarily needed. The first diamond grindstone body, which does not contain the diamond free portion, may be directly fixed to the metallic seat. Further, the outer periphery face 11 of the first diamond grindstone body 3 acts as a guide for providing a straight-forward boring, and since the diamond free portion 3a and the metallic seat do not contain diamond grains, the outer periphery face 11 thereof will gradually wear off, resulting in a failure of providing a straight-forward boring guide.
The above-described recessed cutout portion 10 is formed in a fan-like shape in planar view, and the base portion 10a thereof is formed so as to surpass the center O of the bit 1. Further, the inner periphery face 13 on the inner side of a ring-shaped outer periphery edge 12 on the tip face of the first diamond grindstone body 3 is formed in an approximately reverse-conical recessed shape. The angle of inclination of the approximately reverse-conical inner periphery face 13 is formed so as to be substantially equal to that of an inclined face of a projected portion (the numeral 16 indicated in
Since the recessed cutout portion 10 of the first diamond grindstone body 3 is a portion for removing outside concrete swarf which is peeled off mainly on boring, this portion is not necessarily formed in a fan-like shape in planar view.
Next, the second diamond grindstone body 4 is also a sintered body having the same constitution as that of the first diamond grindstone body 3, provided with the same outer side shape as the inner side shape of the recessed cutout portion 10 of the first diamond grindstone body 3, and fixed by brazing to the tip face of the diamond free portion 3a which is formed to be smaller than the recessed cutout portion 10 and exposed to the recessed cutout portion 10 of the first diamond grindstone body 3. Therefore, the second diamond grindstone body 4 is arranged so as to be set back to the inner side from the outer end portion of the recessed cutout portion 10 of the first diamond grindstone body 3.
Further, the second diamond grindstone body 4 is formed so as to be lower than the first diamond grindstone body 3. That is, the tip of the second diamond grindstone body 4 in the axial direction is positioned on the metallic seat 2 side from the tip of the first diamond grindstone body 3. The height of the second diamond grindstone body 4 is set so as to be substantially equal to a minimum height “h” so that the outer periphery face 11 (excluding the diamond free portion 3a) of the first diamond grindstone body 3 can provide a straight-forward boring guide. More specifically, the length of the second diamond grindstone body 4 in the axial direction is shorter than that of the diamond containing portion 3b in the axial direction. In addition, the axial direction of the bit 1 means a direction of the rotation axis of the bit 1. If the diameter of the first diamond grindstone body 3 is approximately 16 mm, the straight-forward boring guide can be provided at a minimum height of approximately 6 mm (an axial length).
Next, a description will be given for a use aspect of the above-constituted bit 1. In this case, the diamond free portion 3a and the metallic seat 2 are collectively denoted as a base 100. In addition, in the following description, the base 100 corresponds to the metallic seat 2 in an embodiment where the first diamond grindstone body 3 does not have the diamond free portion 3a.
As shown in
Incidentally, in the above-described bit 1, the inner periphery face 13 of the outer periphery edge 12 is formed in a reverse conical shape. Therefore, the outer periphery edge 12 of the bit 1 is first in contact with concrete 14. As shown in
Then, the inner periphery face 13 of the bit 1 is also in contact with the concrete 14, thereby cutting is proceeded by all the tip of the bit 1. A projected portion 16 which is uncut and remains in a conical shape is generated at the center of the bit 1, and grows. However, due to the fact that concrete 14 contains stone debris or the like, this portion, when it grows, is broken or crushed by vibration resulting from the rotation and discharged is naturally from the recessed cutout portion 10. Therefore, it is acceptable that the working capability is low at the center and the boring speed is influenced only slightly. The thus cut swarf is discharged via the side portion of the base 100 from the recessed cutout portion 10 to the shank 7 side. The recessed cutout portion 10 is formed so as to include the center of the bit 1. Thus, as shown in
After repetition of boring work, the diamond grindstone body 3 wears off, and as shown in
When the boring further proceeds, the first diamond grindstone body 3 wears off and, as shown in
As described above, since the base 100 (including the diamond free portion 3a) does not contain diamond grains, the outer periphery face thereof will gradually wear, resulting in a failure of providing the straight-forward boring guide.
According to the above-constituted bit 1, the following effect can be obtained. That is, an approximately reverse-conical shaped inner periphery face 13 is formed on the inner side of the tip face of the first diamond grindstone body 3. Further, as shown in
Further, in association with the boring work, the conical projected portion 16 is made at the center of the tip of the thus bored hole 15. When the top portion 17 thereof is in contact with the second diamond grindstone body 4, an outer side portion of concrete 14 in contact with the bit 1 is cut by the first diamond grindstone body 3, while an inner side portion thereof is cut by the second diamond grindstone body 4 in an auxiliary manner. Thus, there is no decrease in boring speed.
Still further, when the surface of the second diamond grindstone body 4 wears off and is formed into a reverse conical shape, the height thereof is substantially equal to a minimum height by which the outer periphery face 11 of the first diamond grindstone body 3 is able to provide a straight-forward boring guide. No further boring is secured for the straight-forward guide. Therefore, it is possible to know the use limit of the bit 1 and timing of exchanging the bit 1 by observing the extent of wear of the second diamond grindstone body 4. Further, the thus bored hole 15 will not be deflected until the bit is completely used, making it possible to retain appropriately members such as an anchor bolt.
Further, when the top portion 17 of the projected portion 16 made at the center of the hole 15 on boring is in contact with the base 100, the height of the outer periphery face 11 of the first diamond grindstone body 3 (excluding the diamond free portion 3a) may be adjusted so as to give a minimum height, h, capable of providing a straight-forward boring guide (it may be adjusted so that the outer periphery face 11 of the diamond containing portion 3 in the axial direction is set to be a minimum axial length “h” capable of providing the straight-forward boring guide). For example, as shown in
According to the above constitution, the height of the outer periphery face 11 of the first diamond grindstone body (excluding the diamond free portion 3a) (an axial length of the outer periphery face 11 of the diamond containing portion 3b) remaining when the top portion 17 of the projected portion 16 uncut and remaining in a conical shape at the center of a hole after the second diamond grindstone body 4 wears by the boring work is in contact with the base 100 is set to be a minimum height “h” (an axial length “h”) capable of providing straight-forward boring guide. Therefore, the straight-forward boring guide can be secured on complete use of the bit. Further, when the projected portion 16 is in contact with the base 100, the boring speed decreases greatly due to the base 100 which has no boring performance. Still further, an exposed face of the base 100 can be clearly visibly recognized. Therefore, it is possible to reliably know the use limit of the bit 1 and the timing of complete use. It is also possible to keep the second diamond grindstone body 4 to a minimum quantity.
Further, the first diamond grindstone body 3 and the second diamond grindstone body 4 may be formed integrally, or they may be installed as separate members and constituted in an integral manner. Where they are installed as separate members, a projected portion uncut and remaining is changed in shape, depending on whether or not a material to be bored is concrete 14, cement mortar, or light-weight building blocks which contain stones, and the bit 1 is also changed in usability. The second diamond grindstone body 4 is changed in compositions according to the material to be bored, thereby making it possible to provide an optimal non-core drill bit.
The present invention has been described in detail and by referring to specific embodiments. It is apparent for a person skilled in the art that the present invention may be changed or modified in various ways within a scope not departing from the spirit and scope of the invention.
The present application is based on the Japanese patent application (No. 2006-217767) filed on Aug. 10, 2006, with the content incorporated herein as reference.
The present invention is applicable to a non-core drill bit for boring concrete, cement mortar, building blocks and others.
Number | Date | Country | Kind |
---|---|---|---|
2006-217767 | Aug 2006 | JP | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/JP2007/065652 | 8/9/2007 | WO | 00 | 2/5/2009 |