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. 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. 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 1 A 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 1 B is a perspective side view of the drilling assembly in Figure 1A in a ready to drill configuration;

Figure 1 C is a cross sectional side view of the drilling assembly in Figures 1 A and 1 B partway through the process of installing a friction bolt;

Figure 1 D is the same view as Figure 1 C 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 1 A-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 1 A-1 D;

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; 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-1 D, 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. 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. 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. 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 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: (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. 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 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-1 D 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 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 3C). 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 1 C-1 D, 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 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.