WO2021058249A1

WO2021058249A1 - Cutting assembly

Info

Publication number: WO2021058249A1
Application number: PCT/EP2020/074567
Authority: WO
Inventors: Habib Saridikmen
Original assignee: Element Six (Uk) Limited
Priority date: 2019-09-23
Filing date: 2020-09-03
Publication date: 2021-04-01
Also published as: GB2589435A; GB201913658D0; GB202013832D0

Abstract

This disclosure relates to a cutting assembly (10) for a rock excavation machine. The cutting assembly comprises a base unit (12), one or more moveable support arms (14) extending from the base unit, a drive spindle (16) rotatably mounted to the or each moveable support arm, and a disk cutter (18) fixed about the drive spindle such that rotation of the drive spindle causes a corresponding rotation of the disk cutter. The disk cutter comprises a cutter body (20) and one or more cutting elements (22) arranged peripherally around the cutter body. The disk cutter further comprises a body protection element (44) on or in an axial surface of the cutter body to protect the cutter body from bodywash.

Description

CUTTING ASSEMBLY

Field of the Invention

The present disclosure relates to mining and excavation machines. In particular, it relates to a cutting assembly for a rock excavation machine.

Background

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.

The same equipment used above ground may not always be directly usable within the confined space of a subterranean mine.

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

According to the invention, there is provided a cutting assembly fora 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 disk cutter further comprises a body protection element on or in an axial surface of the cutter body to protect the cutter body from body wash.. The body protection element has the sole role of protecting the cutter body from body wash. No cutting or drilling or milling or planning or the like is carried out by the body protection element. During use, the cutting assembly is otherwise vulnerable to body wash, which is the premature wearing away of the typically steel cutter body that surrounds and supports the cutting elements. The body protection element mitigates this body wash.

Preferably, the disk cutter comprises two axial surfaces and the body protection element is provided on one or other or both axial surfaces.

The body protection element may extend at least partially across the axial surface. Alternatively or alternatively, the body protection element may extend across the entire axial surface.

The body protection element may comprise a single unit. Alternatively, the body protection element may comprise a plurality of units.

Optionally, the body protection element is a wear resistant layer forming a hard-facing. Optionally, the body protection element comprises one or more plates. Optionally, the body protection element comprises one or more elongate ribs. Optionally, the body protection element comprises one or more teeth.

Optionally, the body protection element comprises one or more protrusions. The body protection element a plurality of protrusions. The plurality of protrusions may form a first group of protrusions having a first size. Additionally, the plurality of protrusions may also form a second group of protrusions having a second size, the second size being different from the first size. The plurality of protrusions may form one or more groups of protrusions of different materials.

The body protection element may comprise polycrystalline diamond (PCD) material. Additionally or alternatively, the body protection element comprises cemented carbide material(s).

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. 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.

Brief Description of the Drawings

The invention will now be more particularly described, by way of example only, with reference to the accompanying drawings, in which

Figure 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;

Figure 2 is a schematic end view of the long wall mining system of Figure 1;

Figure 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;

Figure 4 is schematic end view of the long wall mining system of Figure 3;

Figure 5 shows a front elevation view of a first embodiment of a disk cutter;

Figure 6 shows a front elevation view of a cutting element for use with the disk cutter of Figure

5;

Figure 7 shows a side elevation view of the cutting element of Figure 6;

Figure 8 shows a front perspective view of a second embodiment of the disk cutter;

Figure 9 shows a side elevation view of a plurality of cutting elements for use with the disk cutter of Figure 8;

Figure 10a is a side elevation view of a first individual cutting element from Figure 9;

Figure 10b is a side elevation view of a second individual cutting element from Figure 9; Figure 11 is a front elevation view of the cutter body of Figures 5 and 8 with a first embodiment of a body protection element in the form of a hard-facing, the cutting elements having been omitted for clarity;

Figure 12 is a front elevation view of the cutter body of Figures 5 and 8 with a second embodiment of a body protection element in the form of a plurality of plates, the cutting elements again having been omitted for clarity;

Figure 13 is a front elevation view of the cutter body of Figures 5 and 8 with a third embodiment of a body protection element in the form of a plurality of plates, the cutting elements again having been omitted for clarity;

Figure 14 is a front elevation view of the cutter body of Figures 5 and 8 with a fourth embodiment of a body protection element in the form of a plurality of plates, the cutting elements again having been omitted for clarity;

Figure 15 is a front elevation view of the cutter body of Figures 5 and 8 with a fifth embodiment of a body protection element in the form of a plurality of plates, the cutting elements again having been omitted for clarity;

Figure 16 is a front elevation view of the cutter body of Figures 5 and 8 with a sixth embodiment of a body protection element in the form of a plurality of plates, the cutting elements again having been omitted for clarity;

Figure 17 is a front elevation view of the cutter body of Figures 5 and 8 with a seventh embodiment of a body protection element in the form of a plurality of plates, the cutting elements again having been omitted for clarity; and

Figure 18 is a front elevation view of the cutter body of Figures 5 and 8 with an eighth embodiment of a body protection element in the form of a plurality of plates, the cutting elements again having been omitted for clarity.

In the drawings, similar parts have been assigned similar reference numerals. Detailed Description

Referring initially to Figures 1 to 2, a cutting assembly for slicing into natural formations 2 underground is indicated generally at 10.

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.

In a first embodiment, indicated in Figures 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.

In a second embodiment, indicated in Figures 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.

In an alternative embodiment, not shown, only a single disk cutter 18 is used.

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.

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.

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 Figures 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 Figures 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.

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.

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 Figure 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.

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 manoeuvrability.

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 50kW per disk cutter 18, depending on the type of disk cutter 18 selected and the cutting force required. As best seen in Figure 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.

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.

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.

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.

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.

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.

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.

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 Figures 5, 6 and 7, or it is detachably mounted to the cutter body 20 using a retention mechanism, as in the embodiment shown in Figure 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.

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.

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.

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.

In one embodiment, the cutting elements 22 are polycrystalline diamond compacts (PDCs), more commonly found in the field of Oil and Gas drilling. Such PDCs are often cylindrical and usually comprise a diamond layer sinter joined to a steel or carbide substrate.

The PDC has a diameter of between 6 mm and 30 mm, preferably between 8 mm and 25 mm. For example, the PDC 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. Each PDC may be chamfered, double chamfered or multiple chamfered.

Each PDC may comprise a polished cutter surface, or be at least partially polished.

Alternatively, rather than being a traditional PDC, 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.

In a first embodiment of a tool holder 24, in Figures 5, 6 and 7, each tool holder 24 is generally frusto-conical when viewed axially (see Figure 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.

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. 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.

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.

Preferably, the seat fully supports the rear (i.e. the surface that is generally opposite the cutting surface 32) of the cutting element 22.

In side view (see Figure 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.

A lateral extent (best seen in Figure 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 1mm 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.

In a second embodiment of a tool holder 24, as shown in Figures 8 and 9, successive tool holders 24 are laterally offset with respect to the cutter body 20. As indicated in Figures 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 Figure 10a, the tool holder 24 kinks rightwards and in Figure 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.

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.

Along a 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.

The cutting assembly 10 may additionally comprise a hard-facing material. The hard-facing material may comprise a low melting point carbide (LMC) material, characterised by its iron base. Exemplary materials are described in US 8,968,834, US 8,846,207 and US 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.

The cutting assembly 10 comprises a body protection element 44 on or in an axial surface 46 of the cutter body 20, as seen in Figures 11 to 18. The body protection element 44 minimises wear of the axial surface 46, thus helping to maximise the operational life of the cutting elements 22 because should the cutter body 20 wear away first, and can no longer provide structural support to the cutting elements 22, the remaining life of the cutting elements 22 becomes irrelevant. In Figure 11 , the body protection element 44 is a coating 44a that extends partially across the axial surface 46. The coating 44a may be a hard-facing material as described above. Alternatively, the coating 44a may cover the entire axial surface 46 (not shown).

In Figure 12, the body protection element 44 comprises a plurality of plates 44b that extends partially across the axial surface 46. In this embodiment, they are rectangular plates 44b although any shape could be used. Again, the plates 44b may be configured and arranged such that they cover the entire axial surface 46.

In Figure 13, the body protection element 44 comprises a plurality of elongate ribs 44c that extends partially across the axial surface 46. Again, the ribs 44c may be configured and arranged such that they cover the entire axial surface.

In Figure 14, the body protection element 44 comprises a plurality of teeth 44d that extends partially across the axial surface 46. The teeth 44d are arranged equi-angularly spaced about the axis of rotation of the disk cutter 20.

In Figure 15, the plurality of teeth 44d are aligned side by side, forming a continuous ring adjacent a peripheral edge of the cutter body 20.

In Figure 16, the body protection element 44 comprises a plurality of protrusions 44e which are regularly spaced about on the axial surface. Protrusions 44e may comprise polycrystalline diamond (PCD) and/or carbide studs (sometimes known as ‘inserts’) that are attached to the axial surface 46, for example by brazing. In Figure 16, the studs 44e are all the same size.

By contrast, in Figure 17, there are two groups of studs 44e of different sizes. A first group 48 of larger studs 44e are located radially inwardly of a second group 50 of smaller studs 44e.

In Figure 18, the reverse is true; the second group 50 of smaller studs 44e are located radially inwardly of the first group 48 of larger studs 44e.

Any number of studs 44e may be provided.

The body protection element 44 may extend at least partially across the axial surface 46 or it may extend completely across the axial surface 46, whether the body protection element 44 is a single unit or it comprises a plurality of units. For example, the studs 44e may be provided only in a radially central zone of the axial surface 46, or they may be provided across the entire surface, as shown in Figures 16, 17 and 18.

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.

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 a 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.

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.

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.

IB 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.

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.

For example, the or each cutting element may comprise single crystal diamond instead of polycrystalline diamond material.

For example, the cutting element 22 may comprise diamond or abrasive grit impregnated metal or be ceramic based.

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.

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 10would 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.

For example, in Figures 11 to 18, although only one support arm is shown, the body protection element may be used in combination with one or two support arms.

Certain standard terms and concepts as used herein are briefly explained below.

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 per cent 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.

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 disk cutter further comprises a body protection element on or in an axial surface of the cutter body to protect the cutter body from body wash.

2. A cutting assembly as claimed in claim 1, in which the disk cutter comprises two axial surfaces and the body protection element is provided on one or other or both axial surfaces.

3. A cutting assembly as claimed in claim 1 or 2, in which the body protection element extends at least partially across the axial surface.

4. A cutting assembly as claimed in claim 3, in which the body protection element extends completely across the axial surface.

5. A cutting assembly as claimed in any preceding claim, in which the body protection element comprises a single unit.

6. A cutting assembly as claimed in any of claims 1 to 4, in which the body protection element comprises a plurality of units.

7. A cutting assembly as claimed in any preceding claim, in which the body protection element is a wear resistant layer forming a hard-facing.

8. A cutting assembly as claimed in any preceding claim, in which the body protection element comprises one or more plates.

9. A cutting assembly as claimed in any preceding claim, in which the body protection element comprises one or more elongate ribs.

10. A cutting assembly as claimed in any preceding claim, in which the body protection element comprises one or more teeth.

11. A cutting assembly as claimed in any preceding claim, in which the body protection element comprises one or more protrusions.

12. A cutting assembly as claimed in claim 11 , comprising a plurality of protrusions.

13. A cutting assembly as claimed in claim 12, in which the plurality of protrusions form a first group having a first size.

14. A cutting assembly as claimed in claim 13, in which the plurality of protrusions additionally form a second group having a second size, the second size being different from the first size.

15. A cutting assembly as claimed in claim 12, 13 or 14, in which the plurality of protrusions form one or more groups of different materials.

16. A cutting assembly as claimed in any preceding claim, in which the body protection element comprises polycrystalline diamond (PCD) material.

17. A cutting assembly as claimed in any preceding claim, in which the body protection element comprises cemented carbide material(s).