Note: Descriptions are shown in the official language in which they were submitted.
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Improved drilling assembly comprising a friction bolt
Field of the Invention
The present invention relates to drilling tools and assemblies for installing
friction
bolts and more particularly drill bits for drill tools and assemblies for
installing friction
bolts. The present invention also relates to friction bolts and methods of
drilling
involving friction bolts.
Background of the Invention
Friction bolts are used to stabilise rooves and walls during underground
mining and
most often have a generally cylindrical body and a collar at the trailing end
of the
body.
Friction bolts are designed so that when they are driven into a slightly
undersized
hole in a formation, such as a rock strata, they resiliently deform. This
resilient
deformation exerts radial and frictional forces against the wall of the hole
to retain
the friction bolt within the hole and to reinforce the rock strata.
Friction bolts can be installed in a two step process where the first step
involves
drilling a hole with one drill tool and the second step involves inserting the
friction
bolt with another tool. This two step process, whilst allowing for the
recovery of the
entire drill string used to drill the hole, is time consuming and otherwise
inefficient.
The deficiencies with the two step process has lead to the development of one
step
processes where the friction bolt is inserted as the hole is drilled. A range
of drilling
tools and assemblies for the one step process have been developed and these
tend
to rely on the use of drill bits that are detached from the drill string, once
the friction
bolt has been installed, so the remainder of the drill string can be retrieved
through
the inside of the friction bolt and re-used. The loss of the drill bit with
each friction
bolt comes at a cost and also requires a new drill bit to be fitted before the
next
friction bolt can be installed.
The present invention seeks to provide an alternative that at least partially
addresses
one or more of the problems with existing one step friction bolt systems.
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Summary of the Invention
According to a first aspect, the present invention provides a drilling
assembly for
simultaneously drilling a hole and inserting a friction bolt, the drilling
assembly
comprising a drill string, a drill bit and a friction bolt, wherein:
(i) the drill string defines a leading end adapted to releasably
operatively
connect to the drill bit and a trailing end adapted to operatively engage
with a means for imparting energy on said drill string;
(ii) the drill bit is mounted on the leading end of said drill string;
(iii) the friction bolt at least partially surrounds said drill string; and
wherein
(iv) the drilling assembly further comprises an elongate spacer that
defines a
leading end and a trailing end and is located between said friction bolt and
said means for imparting energy on said drill string.
According a second aspect, the present invention provides a means for
imparting
energy on a drill string for simultaneously drilling a hole and inserting a
friction bolt,
said means comprising:
(i) a drill string adapted to receive the friction bolt thereon, and
(ii) an elongate spacer mounted on said drill string;
wherein said elongate spacer defines a leading end and a trailing end and is
adapted
to transfer energy from said means for imparting energy on said drill string
towards
said leading end.
According to a third aspect, the present invention provides a method for
simultaneously drilling a hole and installing a friction bolt into a body
requiring
reinforcement, the method comprising the steps of:
(i) providing a drill string including the friction bolt, a drill bit and
an elongate
spacer located at the trailing end of the friction bolt; and
(ii) imparting rotational energy to the drill string and impact energy to
the
elongate spacer simultaneously.
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According to a fourth aspect, the present invention provides a two part drill
bit
assembly comprising:
(i) a first annular drill bit defining a leading end, a trailing end and an
inner
surface and comprising a first cutting part disposed at the leading end;
(ii) a second drill bit defining a leading end, a trailing end and an outer
surface
and comprising a second cutting part disposed at its leading end;
wherein the first annular drill bit is adapted to be releasibly received on
the second
drill bit via said inner surface of the first drill bit and said outer surface
of the second
drill bit.
Brief Description of the Drawings
Figure 1A is an exploded perspective view of a drilling assembly according to
one
embodiment of a first aspect of the present invention including a two part
drill bit;
Figure 1B is a perspective side view of the drilling assembly in Figure 1A in
a ready
to drill configuration;
Figure 1C is a cross sectional side view of the drilling assembly in Figures
1A and 1B
partway through the process of installing a friction bolt;
Figure 1D is the same view as Figure 1C but shows the friction bolt fully
installed;
Figure 2A is a perspective view of an example of the elongate spacer that
forms part
of the embodiment in Figures 1A-1 D;
Figure 2B is cross sectional side view of the elongate spacer in Figure 2A;
Figure 3A is a perspective view of an example of the coupling that that forms
part of
the embodiment in Figures 1A-1D,
Figure 3B is a perspective view of the coupling in Figure 3A from the opposite
end;
and
Figure 3C is cross sectional side view of the coupling in Figures 3A and 3B;
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Figures 4A to 4C are perspective views of an example of a two part drill bit
according
to a fourth aspect of the present invention that forms part of the embodiment
in
Figures 1A-1D, where Figure 4A depicts, the sacrificial part of the bit,
Figure 4B the
other part of the bit that is reusable and Figure 4C the two parts assembled
together.
Detailed Description of the Invention
According a first aspect of the present invention there is provided a drilling
assembly
for simultaneously drilling a hole and inserting a friction bolt, the drilling
assembly
comprising a drill string, a drill bit and a friction bolt, wherein:
(i) the drill string defines a leading end adapted to releasably
operatively
connect to the drill bit and a trailing end adapted to operatively engage
with a means for imparting energy on said drill string;
(ii) the drill bit is mounted on the leading end of said drill string;
(iii) the friction bolt at least partially surrounds said drill string; and
wherein
(iv) the drilling assembly further comprises an elongate spacer that
defines a
leading end and a trailing end and is located between said friction bolt and
said means for imparting energy on said drill string.
The present invention is based on the discovery and/or recognition of two
problems
associated with one step or single pass drilling assemblies and their use.
Firstly, operation of prior art systems can result in undesirable rotation of
or against
the friction bolt during the installation process. Such rotation can damage
the friction
bolt, particularly the trailing end of the friction bolt. Furthermore,
rotation of or
against the friction bolt reduces the efficiency of the process as the
rotational energy
is better focussed on the drill bit.
Secondly, it is common in prior art systems to experience an increased
frequency of
drill rod breakage during the installation process. Such breakages are
contributed to
by the limited ability of the drill assembly to flex, particularly at the
coupling between
the drill string and the drill rig. The flex, particularly at this coupling
becomes more
limited as the friction bolt is installed further in the hole.
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Surprisingly, applicant has found that the inclusion of an elongate spacer
addresses
the above problems or at least partially ameliorates the problems with the
prior art.
Preferably, the elongate spacer at least partially surrounds a part of the
drill string.
Preferably, the part of the drill string is the trailing part of the drill
string.
Preferably, the part of the drill string is the part of the drill string
adjacent to the
means for imparting energy on said drilling string,
Preferably, the leading end of the elongate spacer is adapted to contact the
trailing
end of the friction bolt and transfer energy from the means for imparting
energy on
said drill string to the friction bolt.
Preferably, the energy transferred from the means for imparting energy on said
drill
string to the friction bolt is impact energy.
Preferably, the elongate spacer is adapted not to transfer at least some of
the
rotational energy from the means for imparting energy on said drill string to
the
friction bolt.
Preferably, the elongate spacer is generally cylindrical.
Preferably, the elongate spacer comprises a longitudinal axial passage or bore
adapted to receive the drill string therethrough.
Preferably, the longitudinal axial passage or bore defines a substantially
smooth
inner surface.
Preferably, the longitudinal axial passage or bore has a uniform cross
sectional
shape and size.
Preferably, the longitudinal axial passage or bore is sized to enable the
drill string to
rotate therein without unduly impacting the elongate spacer.
Preferably, the elongate spacer is at least 50, 100, 150, 200, 300, 400, 500,
750 or
1000mm long.
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The drilling assembly may further comprise at least one washer member located
between the elongate spacer and the means for imparting energy on said drill
string.
Preferably, the washer member at least partially surrounds a part of the drill
string.
Preferably, the washer member at least partially surrounds a trailing part of
the drill
string.
Preferably, the washer member at least partially surrounds the part of the
drill string
adjacent to the means for imparting energy on said drilling string.
Preferably, the leading end of the washer member is adapted to contact the
trailing
end of the elongate spacer and transfer energy from the means for imparting
energy
on said drill string to the elongate spacer.
Preferably, the energy transferred from the means for imparting energy on said
drill
string to the elongate spacer is impact energy.
Preferably, the washer member is adapted not to transfer at least some of the
rotational energy from the means for imparting energy on said drill string to
the
elongate spacer.
Preferably, the washer member is a split washer.
Preferably the washer member is an annular ring.
Preferably, the washer member comprises an annulus adapted to receive the
drill
string therethrough.
Preferably, the washer member is sized to enable the drill string to rotate
therein
without unduly impacting the washer member.
Preferably, the washer member is at least 10, 20 or 30mm long.
Preferably, the at least one washer member comprises two washer members.
Preferably, the at least one washer member is lubricated.
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The drilling assembly may further comprise a coupling member adapted to
operatively connect the means for imparting energy on said drill string with
the drill
string.
Preferably, the coupling member is adapted to releasably couple the means for
imparting energy on said drill string with the drill string.
Preferably, the coupling member is generally cylindrical and defines first and
second
threads.
Preferably, the first and second threads are located at opposed ends of the
coupling
member
Preferably the first and second threads have different widths. In this regard,
it is
preferred that the coupling member is a reducer.
Preferably, the first thread on the coupling member is adapted to engage with
a
suitably threaded portion on the trailing end of the drill string and the
second thread
of the coupling member is adapted to engage with a suitably threaded portion
on the
means for imparting energy.
Preferably, the drill bit is disposable.
Preferably, the drill bit comprises a plurality of parts. When the drill bit
comprises
two parts it is preferred that one part is disposable and the other part is
reusable.
Preferably, the disposable drill bit or drill bit part is adapted to be
detached from the
drill string or other part of the drill bit prior to retraction of the drill
string from the hole
at the end of the drilling process.
Preferably, the drill bit is adapted to be releasibly engaged with the end of
the friction
bolt. In this regard, the drill bit may comprise a means for engaging with end
of
friction bolt. Preferably, the means for engaging with end of friction bolt is
a
circumferential groove on the drill bit that provides for a friction fit
between the friction
bolt and the drill bit.
Preferably, the friction bolt is a generally cylindrical structure adapted to
be inserted
into a rock or other formation to provide reinforcement. Preferably, the
friction bolt is
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adapted to exert outward pressure on the hole into which it has been inserted.
Preferably, the friction bolt has a configuration when inserted into a
formation or in
situ ("stressed configuration") where the width or diameter of the
longitudinal axial
passage therein is reduced relative to the width or diameter of the
longitudinal axial
passage prior to insertion of the friction bolt ("relaxed configuration").
Preferably, the friction bolt defines a longitudinal axial passage.
Preferably, the friction bolt comprises a longitudinal split along at least a
portion of its
length and whereby radial expansion of the tube is facilitated by lateral
expansion of
the longitudinal split. Preferably, the longitudinal split extends the full
length of the
friction bolt.
Instead of a longitudinal split, the friction bolt may comprise a fold or
overlap
extending along at least a portion of its length that enables the friction
bolt to exert
outward pressure on the hole into which it is inserted. In this regard, the
fold or
overlap is adapted to function as a spring that when constrained in the drill
hole
exerts outward pressure on the hole.
According a second aspect of the present invention there is provided a means
for
imparting energy on a drill string for simultaneously drilling a hole and
inserting a
friction bolt, said means comprising:
(i) a drill string adapted to receive the friction bolt thereon, and
(ii) an elongate spacer mounted on said drill string;
wherein said elongate spacer defines a leading end and a trailing end and is
adapted
to transfer energy from said means for imparting energy on said drill string
towards
said leading end.
Preferably the means for imparting energy on a drill string is a drilling
machine such
as a jumbo.
According to a third aspect of the present invention there is provided a
method for
simultaneously drilling a hole and installing a friction bolt into a body
requiring
reinforcement, the method comprising the steps of:
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(i) providing a drill string including the friction bolt, a drill bit and
an elongate
spacer located at the trailing end of the friction bolt; and
(ii) imparting rotational energy to the drill string and impact energy to
the
elongate spacer simultaneously.
Preferably, the method further comprises the step of not applying rotational
energy to
the elongate spacer and/or the friction bolt.
Preferably, the method further comprises the step of not rotating the elongate
spacer
and/or the friction bolt.
Preferably, the method further comprises the step of detaching at least part
of the
drill bit prior to retracting the drill string from the hole.
According to a fourth aspect of the present invention there is provided a two
part drill
bit assembly comprising:
(i) a first annular drill bit defining a leading end, a trailing end and an
inner
surface and comprising a first cutting part disposed at the leading end;
(ii) a second drill bit defining a leading end, a trailing end and an outer
surface
and comprising a second cutting part disposed at its leading end;
wherein the first annular drill bit is adapted to be releasibly received on
the
second drill bit via said inner surface of the first drill bit and said outer
surface of
the second drill bit.
Preferably, the inner surface of the first annular drill bit defines a
plurality of recessed
portions and the outer surface of the second drill bit defines a plurality of
raised
portions that are compatibly shaped.
Preferably, the second drill bit further comprises a shank member at its
following end
adapted to operably engage with a drill string.
Preferably, the first annular drill bit comprises a drill bit according to
Figure 4A.
Preferably, the second drill bit comprises a drill bit according to Figure 4B.
Preferably, the two part drill bit comprises a drill bit according to Figure
4C.
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General
Those skilled in the art will appreciate that the invention described herein
is
susceptible to variations and modifications other than those specifically
described.
The invention includes all such variation and modifications. The invention
also
includes all of the steps and features referred to or indicated in the
specification,
individually or collectively and any and all combinations or any two or more
of the
steps or features.
Each document, reference, patent application or patent cited in this text is
expressly
incorporated herein in their entirety by reference, which means that it should
be read
and considered by the reader as part of this text. That the document,
reference,
patent application or patent cited in this text is not repeated in this text
is merely for
reasons of conciseness. None of the cited material or the information
contained in
that material should, however be understood to be common general knowledge.
The present invention is not to be limited in scope by any of the specific
embodiments described herein. These embodiments are intended for the purpose
of
exemplification only. Functionally equivalent products and methods are clearly
within the scope of the invention as described herein.
The invention described herein may include one or more range of values (e.g.
size
etc). A range of values will be understood to include all values within the
range,
including the values defining the range, and values adjacent to the range
which lead
to the same or substantially the same outcome as the values immediately
adjacent
to that value which defines the boundary to the range.
For the purposes of the present invention the terms "leading" and "following"
for
example in the phrases "leading end" and "following end" refer to positions
relative to
the drilling process. "Leading" as used herein refers to a feature or part
thereof that
is closest or proximal to the drilling interface whereas "following" refers to
a feature
or part thereof that is furthest or distal to the drilling interface.
For the purposes of the present invention it is preferred that the term
"friction bolt" is
interpreted to cover any apparatus adapted to be inserted into a rock or other
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formation to provide reinforcement by exerting outward pressure on the hole
into
which it has been inserted.
Throughout this specification, unless the context requires otherwise, the word
"comprise" or variations such as "comprises" or "comprising", will be
understood to
imply the inclusion of a stated integer or group of integers but not the
exclusion of
any other integer or group of integers.
Other definitions for selected terms used herein may be found within the
detailed
description of the invention and apply throughout. Unless otherwise defined,
all
technical terms used herein have the same meaning as commonly understood to
one of ordinary skill in the art to which the invention belongs.
The present invention now will be described more fully hereinafter with
reference to
the accompanying drawings, in which preferred embodiments of the invention are
shown. This invention may, however, be embodied in many different forms and
should not be construed as limited to the embodiments set forth herein;
rather, these
embodiments are provided so that this disclosure will be thorough and
complete, and
will fully convey the scope of the invention to those skilled in the art. Like
numbers
refer to like elements throughout.
Description of the Preferred Embodiments
One embodiment of a drilling assembly, for simultaneously drilling a hole and
inserting a friction bolt, according to a first aspect of the present
invention, is
depicted in Figures 1A-1D and generally indicated by the numeral 10. The
drilling
assembly 10 comprises a friction bolt 12 that includes a longitudinal split
and is
supported on a drill string including a drill rod 14. The drilling assembly
also includes
a plate 15 that is threaded over the friction bolt 12 and provides an
increased surface
area that facilitates the engagement of the flange 17 at trailing end of the
friction bolt
12 with mesh (not shown) when the friction bolt 12 is fully installed.
The leading end of the drill rod 14 includes a threaded portion 16 that is
adapted to
engage with a two part drill bit assembly, according to an embodiment of a
fourth
aspect of the present invention and depicted separately in Figures 4A-4C, via
a
threaded bore in the shank portion 18 of a second drill bit in the form of
reusable drill
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bit 20. The other part of the two part drill bit assembly comprises a first
annular drill
bit in the form of sacrificial drill bit 22 that includes an inner surface
shaped to
releasibly engage with a suitably shaped outer surface on the leading end of
the
reusable drill bit 20.
The trailing end of the drill rod 14 includes another threaded portion 24 that
is
adapted to operatively engage with a means for imparting energy on said drill
string
via a coupling member in the form of a cylindrical threaded reducer coupling
26. The
reducer coupling includes a first thread 28 and a second thread 30 (best seen
in
Figure 30). The first thread 28 is wider and is adapted to engage with a
compatible
thread in the a means for imparting energy on said drill string such as a
jumbo (not
shown), the second thread 30 is adapted to engage with the threaded portion 24
on
the trailing end of the drill rod 14.
Also supported on the drill rod 14 is an elongate spacer in the form of
generally
cylindrical spacer member 32 (depicted separately in Figures 2A and 2B) that
defines a longitudinal axial passage 34 (best seen in Figure 2B). The
longitudinal
axial passage 34 is sized to allow for the drill rod 14 to pass therethrough
and rotate
therein without unduly impacting the cylindrical spacer member. Between the
cylindrical spacer member 32 and the reducer coupling 26 is provided a washer
member in the form of ring washer 36.
In use, best depicted in Figures 1C-1D, the drill assembly 10 simultaneously
drills a
hole and installs a friction bolt 12 into a body 38 requiring reinforcement as
follows.
A drill rod 14 is operatively connected to a drill rig (not shown) via
cylindrical
threaded reducer coupling 26. The ring washer 36 and cylindrical spacer member
32 are then placed on to the drill rod 14 followed by friction bolt 12 and
plate 15. At
this stage, the two part drill bit 20, 22 is then attached to the leading end
of the drill
rod 14 to form the drill string in a ready to use configuration. The operator
then
positions the leading end of the drill string in contact with the body 38 and
commences the drilling process by imparting impact and rotational energy on
the drill
string. In particular, rotational energy is imparted on drill rod 14 that in
turn rotates
two part drill bit 20, 22 to create a hole and impact energy is imparted
through
reducer coupling 26 and ring washer 36 onto cylindrical spacer member 32 and
in
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turn onto the trailing end of the friction bolt 12. Thus, as the hole is
drilled into body
38, friction bolt 12 is installed therein. Throughout the drilling process,
debris can be
removed by the action of a flushing fluid, such as water and/or air, conveyed
through
a longitudinal conduit or bore 35 in the drill string that is in fluid
communication with
the leading end of the part of the drill bit 20 via holes 37 in the part 20 of
the two part
drill bit. Holes 37 extend to the drilling interface with the body 38 when the
two part
drill bit 20, 22 is assembled, via openings 40.
The ring washer 36 and cylindrical spacer member 32 act to limit and
preferably
prevent rotational energy from the drill rig being transferred to the friction
bolt 12
during installation. The present invention has also been found to limit and
preferably
prevent undesirable breakage of drill rod 14 during the installation of the
friction bolt
12. In this regard, cylindrical spacer member 32 preferably ensures that the
coupling
between the drill rod 14 and the drill rig is always spaced apart from the
body 38
requiring reinforcement. This allows for increased flex of the drill string at
all stages
of the installation process.
