Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates to rock drill systems and
bits and rock drilling methods, particularly to drill systems
using nonrotating bits.
Drill bits used for percussive drilling are of many
different forms. Typically, however, rock drill bits have
carbide elements or buttons made of relatively hard material
selected to withstand the wear and erosion caused by the
rotation and percussive forces applied during drilling.
Occasionally, cylindrical bits are used in soft material such
as mud for drilling relatively shallow holes.
A rock drill bit according to this invention can
often be cheaply manufactured, is adaptable to drilling a
wide range of material, obtains superior results in many
percussive applications, and has superior wear characteristics.
The objects and other advantages of this invention will be
apparent from the following description.
According to a broad aspect of the present invention
there is provided a rock drilling system which comprises a
dril~ing means for producing a selected high frequency and
low energy per blow periodic drilling force and for delivering
the drilling force at the selected frequency to a drill bit
without rotating the bit. A drill bit is connected to the
drilling means and has an annular sleeve with a drilling end
at one end of the annular sleeve.
~ ccording to a further broad aspect of the present
invention there is provided a method of drilling through
rock material by using a drill bit having an annular sleeve
with a drilling end. The method comprises directing the
drilling end of the sleeve into the material to be drilled,
and applying a high frequency, low energy per low periodic
drilling force onto th~ sleeve to drive it into the rock
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material while preventing significant rotation of the
drill bit.
According to a still further broad aspect of the
present invention, there is provided a rock drill bit for
drilling through rock material without being significantly
rotated by the force delivered by a high frequency, low
energy per blow percussive device. The bit comprises an
annular sleeve having a cutting end at one end of the
sleeve and adapted to be connected to the percussive device
at the other end.
Fig. 1 is a simplified schematic of a rock drill
system according to this invention;
Fig. 2 is a cross-sectional front view of a
portion of a drill bit assembly and of a drill bit
according to this invention usable in the system shown
in Fig. 1,
Fig. 3 is a partial, cross-sectional side view
of the cutting end of the drill bit shown in Fig. 2 taken
along line III-III of Fig. 2,
Fig. 4 is an enlarged view of a portion of the
cutting end of the drill bit shown in Fig. 2;
Fig. 5 is an end view of the drill bit shown in
Fig. 2 taken along line V-V of Fig. 3
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.
Fig. 6 is a cross-sectional side view of another drill
bit acsording to this invention;
Fig. 7 is an end view of the bit shown in Fig. 6 taken
along line VII--VII of Fig. 6;
Fig. 8 is a cross-sectional side view of another drill
bit according to this invention;
Fig. 9 is an end view of another drill bit according to
this invention; and
Fig. 10 is a split-sectional side view of the drill bit
shown in Fig. 9 taken along line IX--IX.
Referring to Fig. 1, a rock drilling system comprises a
drilling means 12 of any known type for producing a high
frequency, low energy p~r blow periodic drilling force and
for delivering the force to a drill bit without producing
any significant rotation of the drill bit, in any known
manner during normal drilling operation, and a drill bit
aæsembly 14. The drilling means comprises a percussive
drill device 13 or other device producing a periodic force
suitable for drilling and a connecting means 16 for connecting
the percussive device to the drill bit assembly and for
transferring the energy from the percussive device to the
drill ~it assembly. Percussive drill device 13 is of any
known type that produces a high frequency at the bit and low
energy per blow percussive drilling force and typically
comprises a hydraullc or pneumatic mechanism that provides a
cyclical hammer beat at a selected force. A high frequency
in a typical application is and means in excess of the
general range of five thousand beats per minute and preferably
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higher, and a low energy is and means generally about one to
ten foot pounds for smaller bits in the range of up to three
inch diameter and ten to one hundred foot pounds for larger
bits in the range of up to thirty-six inch diameter but
higher energy levels would probably be used in practice
because of the limitations of the current state of the art.
Connecting means 16 is of any known type and would typically
comprise a drill rod or series of drill rods and connecting
devices.
Referring to Figs. 2, 3, 4, and 5, drill bit assembly
14 comprises a drill bit 22 and a coupler or interconnecting
sleeve 26 connected in any manner to connecting means 16
~hich comprises a connecting drill rod 24 connected to
coupler 26. Bit 22 comprises an annular sleeve 23, typical-
ly circular but of any cross-sectional form since the bit is
not rotated, of a preselected thickness; a connecting end
25; a drilling or cutting end 29; a means for breaking chips
produced by the drill bit that comprises a rod 27 within the
internal portion or inner diameter of the bit near or
adjacent but at a preselected distance from cutting end 29;
and a means for removing debris from the cutting area that
comprises air holes 28. Cutting end 29 is smooth but a
jagged or tooth arrangement could be used but would probably
create no advantage since the projected area in contact with
the rock would be the same. A small lip portion 30, shown
only in Fig. 4, extends radially outwardly around the
external perimeter of ~he cutting end of the bit to produce
a greater outer diameter than thQ outer diameter of the main
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body of the drill bit. This lip portion is relatively
small, that is on the order of .0l to .l inches, selected
depending on bit diameter, generally in the range of one-
hundredth of the bit diameter in most cases, and may be
provided upon initial manufacturing in any known manner or
may be formed during use of the bit by the occurring peening
effect created by the action of the drill on the material
drilled.
Drill bit 22 and other bits according to this invention
are preferabl~ constructed of a material ha~ing a hardness
selected to be such that lip portion 30 is naturally formed
and maintained during a drilling operation by peening as the
drill is hammered by the percussive means into the drilled
material. Wear or destruction of the bit is controlled by
limiting the stress on the bit. Typically, suitable stress
levels result in operating indentations into the drilled
material per blo~ of-abo~t one-half to two mils in hard rock
and a~out fi~e to fifteen mils to soft rock.
Ii the outwardly extending lip portion is not provided
at ma~ufacture of the bit it will form during drilling.
Occasionally, it may be necessary to rotate the b~t for
brief periods while applying the drilling force to heat ana
soften the bit to create the desired peening and enhance the
formation of the lip portion. This may be necessary and the
lip portion needs to be formed if softer material is encoun-
tered during initial drilling.
During drilling, the drilling or cutting end of the bit
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is directed into the material to be drilled and the per-
cussive force from the drilling means is applied to the
drill bit through the connecting means. This percussive
force is selected to have a high frequency and low energy
S per blow so that the drill bit will not be rapidly destroyed
or deformed. To accomplish this, the relationships of the
- hardness of the material being drilled, the hardness of the
material of the bit, the thickness of the bit cutting en~,
the frequency of percussion, and the energy applied per blow
are selected to produce the greatest permissible penetration
or indentation per blow without destroying or deforming the
bit by the force of the blow. In this manner, readily
available and less costly material may be used for the bit
since the stresses applied to the bit are limited greatly as
compared to typical drilling systems.
Percussive devices having relatively high frequency and
low energy per blow are known in the art. Typically, for a
drilling operation into limestone a frequency of ten thou-
sand to one hundred thousand beats per minute with an energy
range from three to thirty foot pounds and an AISI of 4340
at 50-55 Rockwell C hardness steel would produce the expected
results.
In addition to controlling the relationship between the
hardness of the drilled material, the hardness of the bit
material, the bit thickness, the energy per blow, and the
percussion frequency, it is important to hold the bit to
prevent significant rotation during normal drilling.
Rotation causes unnecessary erosion and wear on the bit.
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Contrary to expectations, the combination of forces and
materials and the elimination of rotation results in even
and consistent wear so that during drilling the drilling
rate does not change as the drill bit wears since the drill
rate is dependent on the bit face area in contact with rock.
If exceptionally varying materials are encountered, it may
be desirable to rotate the bit between blows to even out
wear.
Since the size of the bit may vary from ranges of about
an inch to many inches or several feet in diameter, it is
usually necessary to break up the pieces that are chipped
out by the bit. In small bits nothing may be necessary, but
larger bits have a means for breaking the formed chip into
smaller components such as a rod 27 as shown in Figs. 2, 3,
and 5. As the bit digs deeper and the chip being formed
moves upwardly inside the drill bit, the rod meets and beats
against the chip to break it into smaller pieces. These
smaller pieces are then drawn up through or around the drill
rod in any manner known in the art.
The means for removing drilling debris is of any known
type and typically comprises a means (not shownl for apply-
ing a vacuum to the center of the drill bit through the
drill rods so that chips are drawn up thr~ugh the center
with air being drawn from around the outside or through air
holes 28 as shown in Figs. 2 and 5.
Referring to Figs. 6 and 7, a bit 62 according to this
invention has a connector 68 and a means for breaking the
chip and comprises a sleeve portion 63 and a central portion
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65 of connector 68 that has a smaller diameter edge 66.
Chips formed within the inner diameter of portion 63 are
broken up by edge 66 to a size small enough to pass up
through an air passage 67 in connec~or 68 to the surface.
S Sleeve portion 63 is connected to sleeve connector 68 by a
rod 69. Connector 68 also has air passages 64 for receiving
air around thP outside of the connector to carry drilling
debris. The air is drawn around the bit and cutting area
and is drawn upwardly through passage 67.
For larger diameter bits, the means for breaking the
chips formed could comprise additional rods similar to rod
27 as shown in Fig. 2, placed at angles to each other or it
could comprise a series of concentric sleeves connected
together to form a drill bit 33 as shown in Fig. 8. Drill
bit 33 has an outer sleeve 34 that functions in the same
manner as drill bit 22 shown in Fig. 2, and has rods 37 and
38 that generally function in the same manner as rod 27
shown in Fig. 2. In addition, a group of two concentrically
positioned sleeves 35 and 36 are held by rods 37 and 38
within sleeve 34 to produce smaller chips able to be drawn
upwardly by the vaccuum applied to central passages 39 and
31 of the drill bit as air is drawn down through an outer
air passage 32 formed between sleeves 34 and 35.
Referring to Figs. 9 and 10, a drill bit 40 according
to this invention is made in any known manner from selected
material and comprises four concentric drill sleeves 41, 42,
¦ 43, and 44. Each of these sleeves has downwardly extending
cutting ends 45, 46, 47, and 48, respectively, that function
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in the same manner as the cutting ends of the drill bits
shown in Figs. 2, 6, and 8. A lip portion 50 is formed
around the outer perimeter of sleeve 41. A means for
removing drilling debris comprises a means (not shown) for
supplying air down the outer circumference of the connecting
rods (not shown) and the outer circumference of a drill bit
connector (not shown) through air passages to have air
flowing over the drilling area to remove the debris upwardly
through a central passage 51. The air path and passages
carrying the air and de~ris are through vertical passages 49
into and along the path formed on the inner side of sleeve
41, out through passages 53, into both central passage 51
and into and along the path formed along the inner side of
sleeve 42, out through passages 54, into both central
passage 51 and the path formed on the inner side of sleeve
43, into and along the path formed along the inner side of
sleeve 43, and out under cutting end 48 into central passage
51.
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