Non-core drill

Abstract

 The present invention is to facilitate the forming f a blind hole by providing a recess (14) at the tip of a diamond grinding wheel assembly (12) and attaching super-hard material piece (16) at the bottom of said recess to crush the workpiece having entered into the recess.

Description

BACKGROUND OF THE INVENTION

[0001] This invention relates to a diamond tool for drilling a blind hole in concrete, stone and other or non-core drill.

[0002] A diamond core drill is highly effective in drilling a through-hole in hard brittle materials such as concrete, stone and others, but can not be used for a blind hole in these materials.

[0003] Non-core drills for the latter purpose have been so far such ones as shown in Fig. 4 and Fig. 5, and have a diamond grinding wheel assembly 2 attached to the tip of a hollow shunk 1. A jet hole 3 for water or air from a spindle opens at an eccentric position, and has a groove 4 on its side. Since the relative velocity to a workpiece is zero at the center of the tip surface 5, the tool has no cutting ability thereon. In fact, small vibrations of the drill will crush the workpiece on this spot to continue drilling, and therefore drills with diameters less than 10 mm are nearly enough to be used, however the distribution of diamond grinding particles near this center gives much irregular cutting qualities. For tools with diameter not less than 10 mm, the cutting qualities will sharply decrease, and further ones with diamter not less than 14 mm can not be used practically for work materials other than highly crushable ones.

[0004] Applications of conventional non-core drills have been so far limited to highly crushable materials, and their poor cutting qualities for concrete, stone and others have been a problem.

SUMMARY OF THE INVENTION

[0005] The purpose of the present invention is to provide a non-core drill which has ability to crush workpiece near the center of its rotation, and a good cutting quality accordingly.

[0006] The present invention provides a non-core drill which has a recess at the tip of a diamond grinding wheel assembly, and at least one large sized diamond particle or one super-hard object such as sintered diamond tip and others attached at the bottom of said recess.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] 

Fig. 1(a) shows a plan view of a first embodiment of a non-core drill in accordance with the present invention, and

Fig. 1(b) a longitudinal cross-sectional view, and

Fig. 2(a) shows a plan view of a second embodiment, and

Fig. 2(b) a longitudinal cross-sectional view, and

Fig. 3(a) shows a plan view of a third embodiment, and

Fig. 3(b) a longitudinal cross-sectional view, and

Fig. 4(a) shows a plan view of a fourth embodiment,

Fig. 4(b) a longitudinal section view,

Fig. 4(c) a perspective view thereof, and

Fig. 5(a) and Fig. 6(a) shows plan views of conventional non-core drills, and

Fig. 5(b) and Fig. 6(b) longitudinal cross-sectional views of the same.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0008] Fig. 1 shows an embodiment of a core drill in accordance with the present invention, and a recess 14 is provided at the tip surface 13 of a diamond grinding wheel assembly 12 attached to the tip of a shunk 11, and a tough large particle diamond 16 is disposed at the bottom 15 of the recess. The numeral 17 denotes a jet hole for water or air, and the numeral 18 a longitudinal relief extending the full length of the grinding wheel assembly 12.

[0009] Due to the existence of the recess 14, the grinding wheel assembly 12 penetrates into the workpiece as a core drill does, and the core generated resultingly is easily crushed due to the small size of the core. Crushed chips, as larger particles, are expelled through the relief 18.

[0010] Fig. 2 shows another embodiment, and a groove 19 is formed on the grinding wheel 12 in place of the relief 18 in Fig. 1. Larger crushed tips are again crushed to be powdered, and a dressing action is performed while this powder is expelled through the space between the drill tip surface 13 and workpiece.

[0011] The larger the diameter of the recess 14 is made, the thinner the wall of the diamond grinding wheel assembly 12 becomes and the smaller the velocity difference between the outer and inner diameter becomes; therefore the wear in the outer and inner periphery is more uniform, and the cutting quality at the tip 13 is improved. This however gives larger core diameters, which results in larger loads to the large particle diamond 16, and accordingly causes a poorer cutting quality. Since there exists such a discrepancy in large diameter drills, the grinding wheel assembly is given a double ring or 21 and 22, as shown in Fig. 3.

[0012] The above-mentioned discrepancy can be removed by making the recess 14 eccentric to the drill center or non-circular shape.

[0013] The embodiment in Fig. 4 shows an example wherein a V-type relief is formed in the grinding wheel assembly 12, and a diamond piece 16 is exposed and a jet hole 17 opened at the bottom surface exposed by the relief 18.

[0014] The table below shows results of an experiment where holes of depth 50 mm were drilled through concrete with compressive strength 250 kg/mm² using 10 kinds of non-core drills.

[0015] A in Column I is for conventional non-core drills as shown in Fig. 5, and B in the same Column for non-core drills of the present invention in Fig. 1, and these drills are the same in the composition of their diamond grinding wheel assemblies. Column II and III are their major dimensions which are different for these 10 kinds of drills. Column IV shows the times required to reach the depth 50 mm. Column V shows the number of holes which can be drilled during the period immediately after the first dressing to the state requiring the next dressing.

[0016] In the experiment, revolutional speeds in Column VI were selected as optimum cutting conditions for respective drills used.

[0017] Shorter cutting times required indicate better cutting qualities, and higher working efficiencies. And dressing intervals are indices for showing the sustaining power of cutting quality. In all cases, non-core drills B of the present invention are superior to conventional ones A; larger diameters are superior for diameters up to 6 mm, but the diameter 10 mm (* mark) results in poor cutting quality due to excessively strong core resulted. That is, the above-mentioned rule has been varified.

I	II	III	IV	V	VI
Drill type	Drill dia. ø mm	Recess dia. ø mm	Required time sec.	Dressing interval No.of hole	Revolution speed PRM
A (conv.)	10.5		28	7	11,000
B (INV.)		4	20	20	9,000
A			65	1
B	14.5	3	38	6	9,000
B		5	22	13
B		*10	55	1
A			80	0.5-1
B	16.5	3	43	4	7,000
B		6	37	10
B		*10	60	1

[0018] For the purpose of drilling a blind hole for an anchor bolt in a concrete structure, a vibrating drill has been generally used; however noises and vibrations are severe and breaking off in workpiece results. A suitable diamond drill has been highly demanded, but conventional non-core drills are not enough to satisfy practical needs because of their low performance or poor cutting quality and others, poor working efficiencies, and operabilities. The prevent invention can provide basic solutions for these setbacks, and is highly effective for drilling blind holes in hard brittle materials such as stone, ceramics and other as well as blind holes for anchor bolts in concrete.

Claims

1. Non-core drill characterized in that, a recess (14) is provided at the tip of its diamond grinding wheel assembly (12), and at least one piece of a large sized diamond particle (16) or super-hard object such as sintered diamond tip and others.

2. Non-core drill as claimed in claim 1, characterized in that,a relief (18) or a groove (19) extending longitudinally through the full length of its diamond grinding wheel assembly (12) is formed for expelling crushed pieces of a workpiece.

3. Non-core drill as claimed in claims 1 or 2, characterized in that, its grinding wheel is formed in a double ring shape (21,22).

4. Non-core drill as claimed in claims 1,2 or 3, characterized in that, its recess (14) is disposed eccentrically to the center of said drill.

5. Non-core drill as claimed in claims 1,2,3 or 4, characterized in that, its recess is non-circular.

Drawing