BACKGROUND OF THE INVENTION
[0001] This invention relates to a non-core drill of the kind defined by the precharacterizing
features of claim 1.
[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] Conventional non-core drills of the kind in question for the latter purpose are shown
in Fig. 2 and Fig. 3, 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 diameter
not less than 14 mm can not be used practically for work materials other than highly
crushable ones.
SU-A 682 379 shows a non-core drill according to the precharacterizing part of claim
1. This drill is designed to make small holes in hard and brittle materials and comprises
a diamond-grinding wheel assembly, besides with a groove making a longitudinal relief.
It is a disadvantage of this known drill that a concrete core may remain in the recess
so that the drilling properties are worsened.
From the US-A 2 731 236 a non-core drill is known comprising a head having provided
at the tip thereof a recess, at the bottom of which a large and massive elongated
cutting diamond is attached. A large number of diamond cutters which are smaller than
the massive elongated cutting diamond are provided in the peripheral surface of the
recess and at the crown of the head. For the escapement of drill water which is supplied
into the recess channels are disposed around the crown and extend upwardly along the
outer periphery of the bit head. There are two main drawbacks in connection with this
known non-core drill. The first is concerned with the relative pure sharpness of the
drill head caused by the diamond cutters defining a rough cutting surface. Therefore,
this known non-core drill is not suited for boring smaller holes. The second drawback
is concerned with a rather pure removing of the cuttings because the channels for
the escapement of the drill water and hence for the cuttings are too small for an
effective washing out of the cuttings.
SUMMARY OF THE INVENTION
[0004] It is the object of the invention to improve the non-core drill of the kind defined
at the preamble with respect to the cutting quality thereof.
This object is attained by the characterizing features of claim 1. An advantageous
development of the invention is given by the subclaim.
In accordance with the present invention a hole is bored while grinding concrete or
the like by the diamond grinding wheel, and the material to be bored is crushed only
at the central portion of the grinding wheel. This combination of grinding and crushing
results in a good cutting quality which is superior to the prior art. A good cutting
quality is assisted by an effective removement of crushed chips as well as larger
particles which are expelled through the elongated relief.
BRIEF DESCRIPTION OF THE DRAWINGS
[0005]
Fig. 1(a) shows a plan view of an embodiment, Fig. 1(b) a longitudinal section view,
Fig. 1(c) a perspective view thereof, and
Fig. 2(a) and Fig. 3(a) show plan views of conventional non-core drills, and fig.
2(b) and Fig. 3(b) longitudinal cross-sectional views of the same.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENT
[0006] 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. This embodiment 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 which extends
the full length of the grinding wheel assembly 12.
[0007] 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.
[0008] 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 showed that cutting times could
be reduced with the drill of the invention.
[0009] 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 of the present invention are superior
to conventional ones as shown in Figs. 2 and 3.
[0010] 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 present 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.
1. Non-core drill comprising a cylindrical diamond grinding body (12) having a non-circular
eccentric recess (14) extending downwards at the tip surface (13) of said body (12)
and opening into a relief (18) at the circumference of said body (12),
characterized
in that the recess (14) extends longitudinally over the full length of said body (12),
in that the recess (14) has a generally V-shaped cross section transverse to the longitudinal
axis of said body (12), the vertex thereof being disposed at the longitudinal axis
of said body (12),
in that the walls of the recess (14) extend in parallel to the longitudinal axis of
said body (12) over the full length of said body (12), and
in that at least one tough large diamond particle (16) or a superhard object such
as a sintered diamond tip is attached to the bottom of the recess (14) at the vertex
of the V-shaped relief (18).
2. Non-core drill according to claim 1,
characterized in that
two tough large diamond particles (16) are provided adjacent to one another.
1. Hohlbohrer mit einem zylindrischen Diamantmahlkörper (12), der eine nicht kreisförmige
exzentrische Ausnehmung (14) aufweist, die sich von der Spitzenoberfläche (13) des
Körpers (12) abwärts erstreckt und sich in eine Aussparung (18) an dem Umfang des
Körpers (12) öffnet,
dadurch gekennzeichnet,
daß sich die Ausnehmung (14) longitudinal über die gesamte Länge des Körpers (12)
erstreckt,
daß die Ausnehmung (14) einen im allgemeinen V-förmigen Querschnitt quer zu der longitudinalen
Achse des Körpers (12) hat, und der Scheitelpunkt derselben an der longitudinalen
Achse des Körpers (12) angeordnet ist,
daß die Wandungen der Ausnehmung (14) sich parallel zu der longitudinalen Achse des
Körpers (12) über die gesamte Länge des Körpers (12) erstrecken, und
daß mindestens ein hartes, großes Diamantteilchen (16) oder ein superhartes Objekt,
wie eine gesinterte Diamantenspitze, am Boden der Ausnehmung (14) an dem Scheitelpunkt
der V-förmigen Aussparung (18) angebracht ist.
2. Hohlbohrer nach Anspruch 1,
dadurch gekennzeichnet,
daß zwei harte, große Diamantteilchen (16) benachbart zueinander vorgesehen sind.
1. Trépan travaillant sans carotte, qui comprend un corps de meulage (12) cylindrique,
diamanté, comportant un évidement excentrique (14) non cùculaire qui s'étend vers
le bas au niveau de la surface de bout (13) dudit corps (12) et s'ouvre en un dégagement
(18) au niveau de la circonférence dudit corps (12),
caractérisé en ce que:
- l'évidement (14) s'étend longitudinalement sur toute la longueur dudit corps (12),
- l'évidement (14) a une section globalement en forme de V transversalement à l'axe
longitudinal dudit corps (12), dont le vertex se trouve au niveau de l'axe longitudinal
(12),
- les parois de l'évidement (14) s'étendent parallèlement à l'axe longitudinal dudit
corps (12), sur toute la longueur dudit corps (12), et
- au moins une grosse particule dure de diamant (16) ou un objet superdur comme une
pointe en diamant fritté est fixée au fond de l'évidement (14) au niveau du vertex
du dégagement (18) en forme de V.
2. Trépan travaillant sans carotte selon la revendication 1, caractérisé en ce que deux
grosses particules dures de diamant (16) sont placées adjacentes l'une à l'autre.