U.S. patent application number 16/982925 was filed with the patent office on 2021-02-04 for cutting assembly.
The applicant listed for this patent is DE BEERS GROUP SERVICES PROPRIETARY LIMITED, ELEMENT SIX (UK) LIMITED. Invention is credited to VALENTINE KANYANTA, MATTHEW JOHN IAN LEEMING, HABIB SARIDIKMEN, ADRIAAN VERMEULEN.
Application Number | 20210032988 16/982925 |
Document ID | / |
Family ID | 1000005163136 |
Filed Date | 2021-02-04 |
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United States Patent
Application |
20210032988 |
Kind Code |
A1 |
LEEMING; MATTHEW JOHN IAN ;
et al. |
February 4, 2021 |
CUTTING ASSEMBLY
Abstract
This disclose relates to a cutting assembly (10) for mining
comprising a disk cutter (18), which is moveable between horizontal
and vertical cutting orientations.
Inventors: |
LEEMING; MATTHEW JOHN IAN;
(DIDCOT, GB) ; KANYANTA; VALENTINE; (DIDCOT,
GB) ; SARIDIKMEN; HABIB; (DIDCOT, GB) ;
VERMEULEN; ADRIAAN; (JOHANNESBURG, ZA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ELEMENT SIX (UK) LIMITED
DE BEERS GROUP SERVICES PROPRIETARY LIMITED |
DIDCOT, OXFORDSHIRE
JOHANNESBURG |
|
GB
ZA |
|
|
Family ID: |
1000005163136 |
Appl. No.: |
16/982925 |
Filed: |
March 21, 2019 |
PCT Filed: |
March 21, 2019 |
PCT NO: |
PCT/EP2019/057132 |
371 Date: |
September 21, 2020 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
E21C 35/1835 20200501;
E21C 35/1833 20200501; E21C 35/1831 20200501; E21C 25/52 20130101;
E21C 25/18 20130101; E21C 35/1837 20200501 |
International
Class: |
E21C 25/18 20060101
E21C025/18; E21C 25/52 20060101 E21C025/52; E21C 35/183 20060101
E21C035/183 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 23, 2018 |
GB |
1804694.6 |
Claims
1. A cutting assembly for a rock excavation machine comprising: a
base unit, one or more moveable support arms extending from the
base unit, a drive spindle rotatably mounted to the or each
moveable support arm, a disk cutter fixed about the drive spindle
such that rotation of the drive spindle causes a corresponding
rotation of the disk cutter, the disk cutter comprising a cutter
body and one or more cutting elements arranged peripherally around
the cutter body, wherein the or each support arm is configured to
be moveable into first and second cutting orientations, in which in
the first cutting orientation the drive spindle is horizontal and
in which in the second cutting orientation the drive spindle is
vertical.
2. The cutting assembly as claimed in claim 1, in which a pair of
spaced apart support arms is provided.
3. The cutting assembly as claimed in claim 1, in which the or each
support arm is moveable between a first operative position and a
second operative position, in each of the first and second cutting
orientations, according to the depth of cut required.
4. The cutting assembly as claimed in claim 2, in which each
support arm comprises a first arm portion connected to a second arm
portion by a joint, each first and second arm portion being
independently moveable relative to each other.
5. The cutting assembly as claimed in claim 1, in which a plurality
of disk cutters are arranged on the drive spindle.
6. The cutting assembly as claimed in claim 5, in which the
plurality of disk cutters are regularly spaced apart along the
length of the drive spindle.
7. The cutting assembly as claimed in claim 6, in which the
plurality of disk cutters are spaced apart by a gap measuring
between 10 cm and 50 cm.
8. The cutting assembly as claimed in claim 6, in which the gap
between adjacent disk cutters is adjustable.
9. The cutting assembly as claimed in claim 1, in which at least
one disk cutter is mounted perpendicularly about the drive
spindle.
10. The cutting assembly as claimed in claim 1, in which at least
one disk cutter is mounted non-perpendicularly about the drive
spindle.
11. The cutting assembly as claimed in claim 1, the disk cutter
further comprising one or more tool holders extending radially
outwards from the cutter body, one tool holder for each cutting
element.
12. The cutting assembly as claimed in claim 11, in which the tool
holders are regularly spaced apart around the cutter body.
13. The cutting assembly as claimed in claim 11, in which the tool
holders are irregularly spaced apart around the cutter body.
14. The cutting assembly as claimed in claim 1, wherein the cutting
element comprises a hard material selected from the group
consisting of cemented carbide (e.g. tungsten carbide), cubic boron
nitride, diamond, diamond like material, or combinations
thereof.
15. The cutting assembly as claimed in claim 14, in which the or
each cutting element is a polycrystalline diamond compact
(PDC).
16. The cutting assembly as claimed in claim 15, each tool holder
having a leading face and a trailing face, each cutting element
being seated in the leading face of the tool holder, facing the
direction of rotation.
17. A long wall mining system comprising a cutting assembly as
claimed in claim 1, a conveying system to transport mined rock away
from a cutting face, and a gathering arm to collect mined rock from
the cutting face and transfer it on to the conveying system.
18. The long wall mining system as claimed in claim 17, further
comprising a secondary wedge tool.
Description
FIELD OF THE INVENTION
[0001] The present disclosure relates to mining and excavation
machines. In particular, it relates to a cutting assembly for a
rock excavation machine.
BACKGROUND
[0002] Many types of rock formations are available around the world
as large deposits, commonly known as slabs. Various types of mining
equipment are deployed in above ground quarries in order to extract
the slabs from the ground. The slabs are retrieved using specialist
equipment, typically dragged from their resting place by large and
very powerful vehicles. Rock slabs may weigh up to 40 tons (40,000
kg). Processing, such as polishing, may take place on site, or
alternatively the slabs may be transported off site for cutting
into appropriately sized pieces for domestic and industrial
use.
[0003] The same equipment used above ground may not always be
directly usable within the confined space of a subterranean
mine.
[0004] It is an object of the invention to provide a compact and
versatile cutting assembly to facilitate the mining and extraction
of geometrically or non-geometrically shaped blocks of specific
rock formations, and one that may be used above or below
ground.
SUMMARY OF THE INVENTION
[0005] According to a first aspect of the invention, there is
provided a cutting assembly for a rock excavation machine, the
cutting assembly comprising: a base unit, one or more moveable
support arms extending from the base unit, a drive spindle
rotatably mounted to the or each moveable support arm, a disk
cutter fixed about the drive spindle such that rotation of the
drive spindle causes a corresponding rotation of the disk cutter,
the disk cutter comprising a cutter body and one or more cutting
elements arranged peripherally around the cutter body, wherein the
or each support arm is configured to be moveable into first and
second cutting orientations, in which in the first cutting
orientation the drive spindle is horizontal and in which in the
second cutting orientation the drive spindle is vertical.
[0006] The cutting assembly is particularly useful underground for
slicing into rock formations, such as kimberlite, granite, or
dolerite. The intention is that the cut rock breaks out under its
own weight, or by secondary wedge force, thereby enabling the
mining of bulk rock material, in geometrically shaped solid
blocks.
[0007] Alternatively, the cutting assembly may be used in the
pre-conditioning of rock surfaces by creating micro-cracks on the
rock surface, thereby facilitating less energy consuming subsequent
extraction. In this application, pulverised rock may be extracted
in a slurry.
[0008] In one embodiment, a pair of spaced apart support arms is
provided.
[0009] Preferably, the or each support arm is moveable between a
first operative position and a second operative position, in each
of the first and second cutting orientations, according to the
depth of cut required.
[0010] Optionally, the or each support arm comprises a first arm
portion connected to a second arm portion by a joint, each first
and second arm portion being independently moveable relative to
each other.
[0011] In some embodiments, a plurality of disk cutters are
arranged in the drive spindle. In such embodiments, the plurality
of disk cutters are preferably regularly spaced apart along the
length of the drive spindle.
[0012] The plurality of disk cutters may be spaced apart by a gap
measuring between 10 cm and 50 cm.
[0013] Optionally, the gap between adjacent disk cutters is
adjustable.
[0014] In some embodiments, at least one disk cutter is mounted
perpendicularly about the drive spindle. In other embodiments, at
least one disk cutter is mounted non-perpendicularly about the
drive spindle.
[0015] Optionally, the disk cutter further comprising one or more
tool holders extending radially outwards from the circular body,
preferably one tool holder for each cutting element. Preferably, a
plurality of tool holders may be used.
[0016] In some embodiments, the tool holders are equi-angularly
spaced around the cutter body. In other embodiments, the tool
holders are irregularly spaced about the cutter body.
[0017] In some embodiments, the cutting element comprises a hard
material selected from the group consisting of cemented carbide
(e.g. tungsten carbide), cubic boron nitride, diamond, diamond like
material, or combinations thereof.
[0018] The or each cutting element is optionally a polycrystalline
diamond compact (PDC).
[0019] In some embodiments, each tool holder has a leading face and
a trailing face, each cutting element being seated in the leading
face of the tool holder, facing or pointing towards the direction
of rotation of the disk cutter.
[0020] According to a second aspect of the invention, there is
provided a long wall mining system comprising a cutting assembly in
accordance with the first aspect of the invention, a conveying
system to transport mined rock away from a cutting face, and a
gathering arm to collect mined rock from the cutting face and
transfer it on to the conveying system. The long wall mining system
may comprises a secondary wedge tool.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] The invention will now be more particularly described, by
way of example only, with reference to the accompanying drawings,
in which
[0022] FIG. 1 is a schematic plan view of an underground mine
incorporating a first embodiment of a cutting assembly as part of a
long wall mining system, and in particular shows the cutting
assembly in a horizontal orientation;
[0023] FIG. 2 is a schematic end view of the long wall mining
system of FIG. 1;
[0024] FIG. 3 is a schematic plan view of an underground mine
incorporating a second embodiment of a cutting assembly as part of
a long wall mining system, and in particular shows the cutting
assembly in a vertical orientation;
[0025] FIG. 4 is schematic end view of the long wall mining system
of FIG. 3;
[0026] FIG. 5 shows a front elevation view of a first embodiment of
a disk cutter;
[0027] FIG. 6 shows a front elevation view of a cutting element for
use with the disk cutter of FIG. 5;
[0028] FIG. 7 shows a side elevation view of the cutting element of
FIG. 6;
[0029] FIG. 8 shows a front perspective view of a second embodiment
of the disk cutter;
[0030] FIG. 9 shows a side elevation view of a plurality of cutting
elements for use with the disk cutter of FIG. 8;
[0031] FIG. 10a is a side elevation view of a first individual
cutting element from FIG. 9;
[0032] FIG. 10b is a side elevation view of a second individual
cutting element from FIG. 9; In the drawings, similar parts have
been assigned similar reference numerals.
DETAILED DESCRIPTION
[0033] Referring initially to FIGS. 1 to 2, a cutting assembly for
slicing into natural formations 2 underground is indicated
generally at 10.
[0034] The cutting assembly forms part of a long wall mining system
1, commonly found in underground mines. The cutting assembly is a
substitute for known shearer technology, which operates on a mine
floor 4, amidst a series of adjustable roof supports 6. As the
shearer advances in the direction of mining, the roof supports 6
are positioned to uphold the mine roof 8 directly behind the
shearer. Behind the roof supports 6, the mine roof 6 collapses in a
relatively controlled manner. Typically, a gathering arm collects
mined rock at the cutting face and transfers it onto a conveying
system for subsequent removal from the mine.
[0035] In a first embodiment, indicated in FIGS. 1 and 2, the
cutting assembly 10 comprises a base unit 12, a pair of spaced
apart support arms 14 extending from the base unit 12, a drive
spindle 16 extending between and rotatably mounted to the pair of
moveable support arms 14, and a plurality of disk cutters 18 fixed
about the drive spindle 16.
[0036] In a second embodiment, indicated in FIGS. 3 and 4, a single
support arm 14 extends from the base unit 12. The drive spindle 16
is supported centrally by the single support arm 14, and the
plurality of disk cutters 18 is mounted to the drive spindle 16,
distributed either side of the single support arm 14.
[0037] In an alternative embodiment, not shown, only a single disk
cutter 18 is used.
[0038] Preferably, the or each disk cutter 18 is mounted at is
centre (i.e. centrally) about the drive spindle 16. However, this
is not essential, and the or each disk cutter 18 may alternatively
be mounted off-set from its centre about the drive spindle 16.
Optionally, a combination of the two arrangements could be used
instead. For example, when multiple disk cutters 18 are used in a
series, i.e. in parallel next to each other along a drive spindle
16, alternating disk cutters 18 may be mounted centrally about the
drive spindle 16. Each centre of the remaining disk cutters 18 may
be radially off-set from the point at which the disk cutter 18 is
mounted about the drive spindle 16. Other combinations are
envisaged.
[0039] The base unit 12 functions as a transport system for the
disk cutter 18. The base unit 12 is moveable to advance and retract
the disk cutter 18 into and out of an operational position, in
close proximity to the rock formation 2 to be cut. The speed at
which the base unit 12 moves closer to the rock formation 2 is one
of several variables determining the feed rate of the cutting
assembly 10 into the rock formation 2. The base unit 12 (in concert
with the roof supports 6) is also moveable sideways, from left to
right and vice versa, along the long wall of the rock formation 2
to be mined.
[0040] Each support arm 14 is configured to be moveable into a
first and a second cutting orientation. In the first cutting
orientation, best seen in FIGS. 1 and 2, the drive spindle 16 is
horizontal. As a result, cuts in the rock formation 2 made by the
disk cutter 18 are correspondingly vertical. In the second cutting
orientation, best seen in FIGS. 3 and 4, the drive spindle 16 is
vertical. Consequently, cuts in the rock formation 2 made by the
disk cutter 18 are correspondingly horizontal. First and second
cutting orientations are possible with either first or second
embodiments mentioned above.
[0041] Optionally, the support arm(s) 14 may also be moveable such
that the drive spindle 16 is operable in any cutting orientation
between the aforementioned vertical and horizontal, though this is
not essential. The support arm(s) 14 may alternatively be
configured such that they are moveable between the first and second
cutting orientations but only fully operational (i.e. the disk
cutter(s) to rotate in order to facilitate cutting or pulverising
of the rock) in the first and second cutting orientations.
[0042] Each support arm 14 is moveable between a first operative
position and a second operative position, in optionally each of the
first and second cutting orientations, according to the depth of
cut required. This is indicated by double end arrow A in FIG. 2.
For example, in the first operative position, the drive spindle 16
is lowered so as to be in close proximity to the mine floor 4 and
in the second operative position, the drive spindle 16 is raised so
as to be in close proximity to the mine roof 8.
[0043] Optionally, each support arm 14 may have a first arm portion
connected to a second arm portion by a pivot joint (or
alternatively, a universal joint), each first and second arm
portion being independently moveable relative to each other. This
arrangement augments the degrees of freedom with which the cutting
assembly 10 may operate and advantageously improves its
maneuverability.
[0044] The drive spindle 16 is driven by a motor to rotate at a
particular speed. The power of the motor is typically between 20
and 50 kW per disk cutter 18, depending on the type of disk cutter
18 selected and the cutting force required.
[0045] As best seen in FIG. 5, in one embodiment, the disk cutter
18 comprises a circular body 20 and a plurality of cutting elements
22 arranged peripherally around the circular body 20. Rotation of
the drive spindle 16 causes a corresponding rotation of the disk
cutter 18. However, the disk cutter 18 need not be circular and may
just be generally circular, for example, depending on its size, an
octagonal shaped cutter could approximate a generally circular disk
cutter. Accordingly, the disk cutter 18 may be hexagonal,
octagonal, decagonal etc, or indeed have any number of
circumferentially extending sides.
[0046] The or each disk cutter 18 may further comprise one or more
sensors. These sensors may be embedded or integrated into the
cutter body 20. The sensor may be any one of the following: a
temperature sensor, a pressure sensor, an X-ray sensor, a gamma ray
sensor, an accelerometer, a sensor configured to monitor the
chemistry of the cutting conditions, or a sensor to identify the
rock formation or materials for extraction. In such an embodiment,
the sensors may be coupled to a data harvesting system, and
potentially also coupled with a data analysis package on-line or
remote from the mining/extraction operation.
[0047] In a preferred embodiment, a plurality of disk cutters 18 is
arranged on the drive spindle 16. Typically, six or more disk
cutters 18 may be provided. The disk cutters 18 are preferably
regularly spaced apart along the length of the drive spindle 16,
between the pair of spaced apart support arms 14a, 14b, or either
side of the support arm 14, depending on the embodiment.
[0048] The spacing of the disk cutters 18 is selected according to
the depth of cut required and the mechanical properties, e.g.
Ultimate Tensile Strength (UTS), of the rock formation 2 being cut
in order to optimise the specific cutting energy, which will
dictate the required power consumption. The aim is to achieve
conditions under which the cut material will breakout under its own
weight. For example, for a 0.4 m depth of cut in Kimberlite, the
ideal spacing between adjacent disk cutters is around 0.3 m.
However, this can be increased or decreased depending on the force
required for breakout. Preferably, the spacing is adjustable
in-situ and may be an automated process or a manual process. The
spacing may be remotely adjustable, for example from an operations
office above ground. A wedge shaped tool may be used to apply such
a breakout force, to assist in rock breakout.
[0049] The disk cutters 18 are spaced apart by a gap measuring
between preferably 0.01 m and 2 m, more preferably between 0.01 m
and 0.5 m. Yet more preferably, the disk cutters are 18 spaced
apart by a gap measuring between 10 cm and 40 cm.
[0050] The circular body 20 of the disk cutter 18 is typically made
from steel and has a diameter of approximately 1000 mm and a
thickness (measured axially, also considered to be a lateral extent
for subsequent descriptions) of approximately 11 mm. Realistically,
such a diameter enables a depth of cut of up to 400 mm. The
circular body 20 has a shaft diameter 23 of between 60 mm and 100
mm, and is sized and shaped to receive the drive spindle 16.
[0051] The diameter (or effective diameter in the case of
non-circular disk cutters) and thickness of the disk cutter 18 are
selected appropriately according to the intended application of the
cutting assembly. For example, cable laying applications would
require a disk cutter 18 with a smaller diameter. Robotic arm angle
grinders would require a yet smaller diameter. Tunnelling
applications though would require a disk cutter 18 with a
significantly greater diameter and would be adapted
accordingly.
[0052] In this embodiment, the disk cutter 18 also comprises a
plurality of tool holders 24 for receiving a corresponding quantity
of cutting elements 22. In an alternative embodiment, the disk
cutter comprises one or more tool holders.
[0053] Preferably though not essentially, each tool holder 24
provides a seat for one cutting element 22. Preferably, each tool
holder 24 is made from steel but may alternatively comprise any
metal(s) or carbides or ceramic based materials with a hardness
above 70 HV (Vickers Hardness). Each tool holder 24 may be either
permanently connected to the cutter body 20 (e.g. using brazing or
welding), as in the embodiment shown in FIGS. 5, 6 and 7, or it is
detachably mounted to the cutter body 20 using a retention
mechanism, as in the embodiment shown in FIGS. 8, 9 and 10a and
10b. A mixture of brazing, welding and/or mechanical connections
could be used. Alternatively, the tool holder(s) 24 may be formed
integrally with the body 20 of the disk cutter 18, for example, by
forging, powder metallurgy etc.
[0054] The retention mechanism may comprise a locking pin
arrangement 25 which is used to secure the tool holder 24 to the
cutter body 20. Clamping, shrink fitting etc may alternatively be
used.
[0055] In one embodiment, each cutting element 22 is rigidly or
fixedly supported by one of the tool holders 24. Each tool holder
24 is preferably equi-angularly spaced around a circumferential
surface of the cutter body 20. Each cutting element 22 may be
secured in place in or on the tool holder 24 using brazing.
Alternatively, the or each tool holder 24 may be configured to
rotatably receive a cutting element 22. In such an embodiment, the
cutting element 22 and tool holder 24 may be configured such that
the cutting element 22 may freely rotate within the tool holder 24,
e.g. with a clearance fit, or alternatively be able to rotate
within the tool holder 24 only when the cutting element 22 comes
into contact with the rock formation being mined/excavated, e.g.
with a transition fit.
[0056] Each of the cutting elements 22 comprise a hard, wear
resistant material with a hardness value of 130 HV and above. The
cutting element 22 preferably comprises a superhard material
selected from the group consisting of cubic boron nitride, diamond,
diamond like material, or combinations thereof, but may be a hard
material such as tungsten carbide instead. The cutting element 22
may comprise a cemented carbide substrate to which the superhard
material is joined.
[0057] In one embodiment, the cutting elements 22 are
polycrystalline diamond compacts (PCDs), more commonly found in the
field of Oil and Gas drilling. Such PCDs are often cylindrical and
usually comprise a diamond layer sinter joined to a steel or
carbide substrate.
[0058] The PCD has a diameter of between 6 mm and 30 mm, preferably
between 8 mm and 25 mm. For example, the PCD may have a diameter of
13 mm, or 16 mm or 19 mm. Preferably, the PCD has a diameter of 16
mm. A combination of diameters may be used in a disk cutter.
[0059] Each PCD may be chamfered, double chamfered or multiple
chamfered.
[0060] Each PCD may comprise a polished cutter surface, or be at
least partially polished.
[0061] Alternatively, rather than being a traditional PCD, the
cutting element 22 may be a 3-D shaped cutter. A strike tip of the
cutting element 22 may be conical, pyramidal, ballistic,
chisel-shaped or hemi-spherical. The strike tip may be truncated
with a planar apex, or non-truncated. The strike tip may be
axisymmetric or asymmetric. Any shape of cutting element 22 could
be used, in combination with any aspect of this invention. Examples
of such shaped cutters can be found in WO2014/049162 and
WO2013/092346.
[0062] In a first embodiment of a tool holder 24, in FIGS. 5, 6 and
7, each tool holder 24 is generally frusto-conical when viewed
axially (see FIG. 6). Each tool holder 24 has a leading face 26 and
a trailing face 28, each cutting element 22 being received into a
seat 30 in the leading face 26 of the tool holder 24. Each seat 30
is angled such that the cutting element 22 tangentially faces (or
generally points towards) the intended direction of rotation. This
is particularly useful for PCDs which have a planar primary cutting
surface 32. Thanks to the seat, a cutting edge 33 of the cutting
element 22 can be oriented in a range of angles with respect to the
cutter body 20, which contrasts with the conventional approach of
having cutting elements 22 pointing exclusively radially or axially
outwards in the direction of advance of the rock face. This allows
great flexibility for obtaining a desired cutting angle without
having to modify the configuration of the strike tip of the cutting
element.
[0063] Furthermore, having a seat for receiving a separate cutting
element 22 means that advantageously, any surplus PDC stock can be
used up and find utility in a new application, thereby reducing the
working capital of a company.
[0064] Optionally, the rake angle of the cutting element is between
25 degrees and 30 degrees. Optionally, the rake angle is around 25
degrees. Optionally, the rake angle may be positive or
negative.
[0065] The leading face 26 of the tool holder 24 is generally
shorter than the trailing face 28, thereby providing significant
structural back support for the cutting element 22 during use. The
tool holder 24, particularly the rear of the tool holder 24 in the
direction of rotation, absorbs a significant proportion of the
impact forces during use, and reduces the risk of the cutting
element 22 otherwise popping out of the cutter body 20 and being
lost.
[0066] Preferably, the seat fully supports the rear (i.e. the
surface that is generally opposite the cutting surface 32) of the
cutting element 22.
[0067] In side view (see FIG. 7), each tool holder 24 has a varying
lateral cross-section, indicated by arrow B. Each tool holder 24
tapers laterally inwardly from the head 34 of the tool holder 24
near the cutting element 22 to a foot 36, near the circular body
20.
[0068] A lateral extent (best seen in FIG. 7) of each cutting
element 22 is greater than a lateral extent of the tool holder 24.
This overhang protects the tool holder 24 from significant wear
during use. Preferably, a thickness (i.e. lateral extent) of the
tool holder 24 is around 14 mm. In this embodiment, the cutting
element 22 protrudes past the tool holder 24 by approximately 1 mm
on either side. This ensures that it is the cutting element 22, and
not the tool holder 24 or the cutter body 20, which is subject to
the primary wear during use. The overhang prevents the tool holder
24 from rubbing against the rock formation 2. In the event of
rubbing, a hard coating or multi-layered approach may be used.
[0069] In a second embodiment of a tool holder 24, as shown in
FIGS. 8 and 9, successive tool holders 24 are laterally offset with
respect to the cutter body 20. As indicated in FIGS. 10a and 10b,
each tool holder 24 includes a slight kink to one side. In other
words, a distal portion 24a of the tool holder 24 is laterally
offset with respect to the circular body 20 and a proximal portion
24b of the tool holder 24. Both the distal and proximal portions
24a, 24b are laterally elongate. The distal and proximal portions
24a, 24b of the tool holder 24 meet at an intersection, indicated
generally at 38. The direction of the lateral offset is in either a
first direction, axially away from one side of the cutter body 20,
or in a second opposing direction, away from the other side of the
cutter body 20. In FIG. 10a, the tool holder 24 kinks rightwards
and in FIG. 10b, the tool holder 24 kinks leftwards. The
intersection 38 may be a sharp change of direction, such as a dog
leg, or a prolonged change of direction, such as a curve. The
intersection 38 may comprise a mid-portion joining the distal
portion 24a to the proximal portion 24b.
[0070] As an alternative, it is envisaged that the proximal portion
24b could be laterally offset with respect to the cutter body 20
whilst the distal portion 24a is in alignment with the circular
body 20. However, since the cutting element 22 is usually located
on the distal portion 24a of the tool holder 24, the first
mentioned arrangement is preferable.
[0071] Along the circumferential surface 40 of the cutter body 20,
the direction of the lateral offset alternates for successive tool
holders 24. The benefit of this arrangement is that it increases
the effective cutting area offered by the cutting elements 22
during rotation of the circular body 20, regardless of the size of
the cutting element 22. It also facilitates a quick and easy change
of an individual tool holder 24 during maintenance and repair,
without having to remove the entire cutter body 20. Furthermore,
the arrangement helps reduce erosion of the cutter body 20
(sometimes known as `body wash`) caused by the flow of cut rock
past the cutting assembly 10.
[0072] The cutting assembly 10 may additionally comprise a
hard-facing material (not shown). The hard-facing material may
comprise a low melting point carbide (LMC) material, characterised
by its iron base. Exemplary materials are described in U.S. Pat.
Nos. 8,968,834, 8,846,207 and 8,753,755, although other wear
resistant materials could be used instead. The purpose of the hard
facing material is to limit body wash of the circular body 20. The
hard-facing material may be located rotationally behind the tool
holder 24, proximate to the trailing face 28. If the tool holders
24 are spaced apart, then the hard-facing material may be provided
in or on the cutter body 20, between successive tool holders 24.
Additionally, or alternatively, the hard-facing material may be
provided on the trailing face 28. Additionally, or alternatively,
the hard-facing material may be provided on the leading face 26.
The hard-facing material may be provided on the leading face 26,
the trailing face 28 and on the circumferential surface 40. The
location of the hard-facing material on the cutter body 20 and/or
tool holder 24 is site specific, and is selected according to the
nature of the rock formation being mined at that site.
[0073] In use, the disk cutter 18 is brought into contact with the
rock formation 2 and rotation of the drive spindle 16, and
therefore its disk cutter(s) 18, causes slicing of the rock
formation 2. The cutting assembly 10 slices into the rock formation
2, for example, to create clean orthogonal cuts of around 16 mm,
depending on the size of the cutting elements 22 selected. The cut
rock breakouts either under its own weight or with secondary wedge
force, e.g. using a wedge-shaped tool.
[0074] Although several applications of the cutting assembly have
been mentioned above, tunnelling is a particularly attractive
application. Conventionally, in order to create a new tunnel
underground, a tunnel boring machine (TBM) is used. TBMs create a
cylindrical shaped tunnel in a well-known manner. If the purpose of
the tunnel is for vehicular or pedestrianised traffic, and only a
circular lateral cross-section is possible, a new horizontal floor
must be included within the lower portion of the tunnel.
Effectively, the diameter of the tunnel is oversized. Excess rock
material must be extracted in order to create the actual required
useable space within the upper portion of the tunnel and this
increases tunnelling costs, not only because a larger TBM demands
more consumable cutting tips than s smaller TBM, but also that the
tunnelling operation takes significantly longer. Furthermore,
additional material is required for construction of the new floor.
Thanks to the cutting assembly described herein, a tunnel with a
smaller lateral cross-section can be created, thereby producing the
required shape of the upper tunnel. The cutting assembly then
follows the smaller TBM to shape the lower half of the tunnel,
creating a floor perpendicular to the walls, and removing
significantly less material than with a larger TBM.
[0075] While this invention has been particularly shown and
described with reference to embodiments, it will be understood by
those skilled in the art that various changes in form and detail
may be made without departing from the scope of the invention as
defined by the appended claims.
[0076] For example, in the second embodiment of the cutting
assembly, though only a single support arm 14 has been described,
two or more spaced apart supports arms 14 may be provided
instead.
[0077] For example, the two embodiments described herein both
include a plurality of disk cutters 18 mounted on the drive spindle
16. This need not be the case and a single disk cutter 18 could be
used instead.
[0078] For example, instead of using a combination of paired
cutting elements 22 and tool holders 24, the cutting elements may
be integrated directly into the body of the disk cutter 18 at a
peripheral edge thereof, thereby obviating the need for an
intermediate tool holder 24.
[0079] For example, the or each cutting element may comprise single
crystal diamond instead of polycrystalline diamond material.
[0080] For example, the cutting element 22 may comprise diamond or
abrasive grit impregnated metal or be ceramic based.
[0081] Although, the cutting assembly 10 has been described as been
of being utility underground, it may equally be used above ground,
for example in an open quarry.
[0082] Furthermore, a smaller scale version could be used for
digging micro trenches in roads and pavements, for example, for
laying small diameter fibre optic cables. In this case, the cutting
assembly 10 would be cutting into asphalt and concrete, not rock.
In such an embodiment, the diameter of the cutter body 20 would be
in the order of 300 mm, the lateral thickness of the cutter body up
to 20 mm, and the cutting elements sized correspondingly. The
intention is to achieve a depth of cut of around 50 mm to 100
mm.
[0083] Certain standard terms and concepts as used herein are
briefly explained below.
[0084] As used herein, polycrystalline diamond (PCD) material
comprises a plurality of diamond grains, a substantial number of
which are directly inter-bonded with each other and in which the
content of the diamond is at least about 80 volume percent of the
material. Interstices between the diamond grains may be
substantially empty or they may be at least partly filled with a
bulk filler material or they may be substantially empty. The bulk
filler material may comprise sinter promotion material.
[0085] PCBN material comprises grains of cubic boron nitride (cBN)
dispersed within a matrix comprising metal, semi-metal and or
ceramic material. For example, PCBN material may comprise at least
about 30 volume percent cBN grains dispersed in a binder matrix
material comprising a Ti-containing compound, such as titanium
carbonitride and or an Al-containing compound, such as aluminium
nitride, and or compounds containing metal such as Co and or W.
Some versions (or "grades") of PCBN material may comprise at least
about 80 volume percent or even at least about 85 volume percent
cBN grains.
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