Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates to a drill bit for use with a
reciprocating device, wherein the bit is in the form of a
corrugated frusto-conical roller, supported by a U-shaped
member attached to a mounting post.
Corrugated frusto-conical rollers are presently used to
crush hard material such as rock by rolling a roller across
the surface to be crushed. Such a system, however, has the
disadvantage of crushing the hard material into very small
granules or even dust, when larger particles would have been
preferred. Such an arrangement is inefficient since more
energy is needed to reduce the hard material to dust than to
lumps of variable size. The removal of such lumps of hard
material from the site of drilling is also easier and more
efficient than removal of equivalent amounts of fine dust.
The drill bits of the prior art also suffer from rapid loss
of an effective cutting edge because the prior designs of
such bits provide that always the same area of cutting edge
is in contact with the hard material to be drilled. As a
result, such drill bits require frequent sharpening or
replacement.
An object of the present invention is therefore to provide a
drill bit which granulates hard material to produce chunks
instead of small granules or dust.
Another object of the invention is to provide a drill bit
wherein the section of the cutting edges contacting the
surface to be drilled, continously change, thereby avoiding
the rapid deterioration of sharpness mentioned above.
Accordingly the invention provides a drill bit for use with
a reciprocating device, comprising:
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(a) a mounting post having an upper end and a lower end,
the post having i-ts upper end designed for attachrnent to
the reciprocating device so as to be reciprocated by the
reciprocating device in the direction of its
longitudinal axis;
(b) a U-shaped member having two arms and a base attached to
the lower end of the mounting post;
(c) a single corrugated frusto conical roller for striking a
surface to be drilled, the roller being mounted between
the arms of the U-shaped member on an axle so that the
roller is rota-table about is geometrical axis, the axis
of the post as extended intersecting the central portion
of the roller, the corrugations being alternating peaks
and furrows, each peak being tipped with a hard material
and defining a circle, the circles being concentric
about the roller's geometrical axis and having diameters
which decrease from one end of the roller to its other
end; the axle being orien-ted so that aligned points on
the peaks of the roller at the drilling end of the drill
bit define an imaginary line substantially perpendicular
to the direction of reciprocation of the mounting post.
The drill bit according to the invention is for use wi-th any
known reciprocating device such as the hydraulic/pneumatic
hammers disclosed :in UK patent applica-tion GB 2 108 594 A
(published 18-5-86) or with the drill head and impact hammer
system disclosed in Canadian Pa-tent 1,133,954, or with the
drilling apparatus disclosed in Canadian Patent Appiication
No. 449,751. Such devices may for example be hydraulically,
pneumatically or electrically powered.
The present invention overcomes the difficulties of the
prior art by causlng the material to be drilled to break off
in lumps.
This is achieved by a characteristic of the new design which
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allows that the Eorce irnparted to the drill bit by the
reciprocating device is not equally spread over the length
of the roller section of the drill bit when striking the
hard material to be drilled. Instead, due to the difference
in diameter of the peaks, the force imparted by each peak
on the roller to the surface to be drilled is different from
the next and reduces gradually along the length of the
roller with the peak of greatest diameter imparting the
greatest force. This inequality of applied force as well as
the difference in diameter of the peaks cause the material
to be drilled to crumble under much less overall force.
Another advantage of the present invention is that the shape
of the drill bit causes force to be transmitted via the
corrugated peaks at an angle to the surface to be impacted.
This facet again renders the material to be drilled more
susceptible to crumbling since the force applied is not
perpendicular to the impacted surface.
In this invention the roller is rotatable about its axis
thereby alowing different parts of the cutting ridges to be
in contact with the surface to be imparted at every strike
of the reciprocating device. This provision means that the
cutting edges, because they lie in series, circumferentially
along the roller, have increased area (compared with the
prior art) of potential contact with the impacted surface,
thereby lengthening their useful lifetime, and concomitantly
allowing sharp edges to be maintained longer.
The objects, advantages and other features of the present
invention will become more apparent upon reading of the
following non-restrictive description of a preferred
embodiment thereof, made within reference to the
accompanying drawings; in which:
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Figure 1 is a side elevation of the drill bit;
Figure 2 is also a side elevation of the drill bit but
viewed at 90 to the elevation shown in Figure 1; and
Figure 3 is a cross section along the line AA marked on
figure 1, showing the spline configuration on the mounting
post.
In Figures 1 and 2, the frusto-conical roller (4), including
corrugations formed by alternating peaks and furrows, is
mounted between the arms of a U-shaped member (5) on an axle
(7) which runs along the geometrical axis CC' of the
roller (4). The axle (7) is surrounded by roller bearings
and rings of ball bearings (not shown) within the roller,
enabling the roller to rotate freely about its geometrical
axis. The axle and the bearings are strong enough to
withstand the impacting stresses to which they are
subjected. Otherwise, the axle and bearings are of any
design commonly known in the art and are therefore not
further described here. The roller is preferably made from
tempered steel.
The U-shaped member (5) is designed so that it retains the
roller (4) through the axle (7) so that the peaks (6) of the
corrugated roller include striking points defining the free
end of the drill bit and located along an imaginary line
BB', which is substantially perpendicular to the direction
of reciprocation of the mounting post (8).
The angle of the geometrical axis of the roller to the
imaginary line BB' is variable and may be chosen to select
the desired gradation of forces imparted by each peak (6)
along the length of the roller (4).
The cutting edges (teeth) on the roller are sited at the
peaks (6) of the corrugations and may be made from material
suitable for whatener hard material it is desired to
fragment. However, it is preferred that the cutting teeth
(6) are carbide tipped. The number of teeth may be varied
but the preferred number is seven.
The drill head shown in figures 1 and 2 can be attached to
any impacting device as explained above, so that the bit is
caused to move alternately in opposite directions X and Y
(see figures 1 and 2). From figure 1 it is therefore clear
that the cutting teeth (6) of the roller (4) meet the
surface to be impacted at a slight angle to the
perpendicular. This results in shock waves penetrating the
hard material being drilled in an asymmetrical manner
thereby causing fragmentation to occur more easily than if
the impact were perpendicular.
The U-shaped member (5) which retains the roller (4) is
attached to one end of a mounting post (8) which carries
splines (9) so that in cross-section -see F'igure 3- the
mounting post has the aspect of a cog. This embodiment
prevents rotational movement of the bit while allowing
guided percussive movement of the same. When this embodi-
ment is employed, the bit is suitable for mounting, for25 example, in an hydraulic reciprocating device of the type
disclosed in U.K. application GB 2 108 594 A which describes
a similar mounting arrangement using splines.
The mounting post (8) carries an indented ring (10) towards
its proximal end, to facilitate attachment to the desired
impacting tool. Such an indented ring (10) normally
provides a recess into which fit two half-annuli attached to
the impacting tool employed (not shown), in order to secure
the bit firmly while the device undergoes reciprocal longi-
tudinal motion.
Finally at the proximal end of the drill bit of the presentinvention there may be provided a bit valve (11) which
allows percussive action of same types of reciprocating
device or hamer which can be used in conbination with the
drill bit.
Although the present invention has been described
hereinabove by means of a preferred embodiment thereof, it
should be pointed out that any modification to this
preferred embodiment, within the scope of the appended
claims, is not deemed to change or alter the nature of the
invention.
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