AU2005201926B2 - Rock cutting machine - Google Patents

Description

00 N la ROCK CUTTING MACHINE Technical Field The present invention relates to a rock cutting machine for cutting rock, or removing rock Sfrom a surface. More particularly, the invention relates to rock cutting machines for cutting ,hard rock by means of an oscillating disc cutter device.

C Background Art (Ni Traditionally, excavation of hard rock in the mining and construction industries, has taken Sone of either two forms, namely explosive excavation, or rolling edge disc cutter excavation. Explosive mining entails drilling a pattern of holes of relatively small diameter into the rock being excavated, and loading those holes with explosives. The explosives are then detonated in a sequence designed to fragment the required volume of rock for subsequent removal by suitable loading and transport equipment. The explosives are detonated once all personnel are evacuated from the excavation site and the explosive process is repeated cyclically, until the required excavation is complete.

The use of explosives for excavation is known to be dangerous, while it is also environmentally unfriendly and results in damage to the country rock, with the result that clearing of loosened rock pieces and the erection of supports for the excavated surfaces is both dangerous and difficult. Additionally, the cyclical nature of the process and the violent nature of the rock fragmentation has to date, prevented automation of the explosive process, so that the modem requirement for continuous operation and increased production efficiency has not been met. Moreover, the relatively unpredictable size distribution of the rock product formed, complicates downstream processing.

Mechanical fragmentation of rock eliminating the use of explosives, has already been achieved and is well known through the use of rolling edge-type disc cutter technology.

This technology has facilitated automation of the excavation process including the benefit of remotely controlled excavation machinery. However, rolling edge cutters require the application of very large forces in order to crush and fragment the rock under excavation.

500735718_2.DOC 00 2 For example, the average force required per cutter is in the order of 50 tonnes and typically, peak forces experienced by each cutter are more than twice than this. It is common for multiple cutters to be arranged to traverse the rock in closely spaced parallel paths, and ISO cutters per cutting array is common. Cutting machinery of this kind can weigh upwards of 800 tonnes, thereby requiring electrical power in the order of thousands of kilowatts for Soperation. As such, that machinery can only be economically employed on large projects, such as water and power supply tunnels. Additionally, the excavation carried out by such machinery is limited to a cross-section which is circular.

It is an object of the present invention to overcome or ameliorate at least one of the disadvantages of the prior art, or to provide a useful alternative.

Disclosure of the Invention Accordingly, in a first aspect, the invention provides, a rock boring device including: a housing; a shaft mounted within the housing for rotation about a longitudinal shaft rotation axis, the shaft having a driven section and a mounting section, the mounting section including a mounting axis, parallel to and spaced from the shaft rotation axis; rotational drive means connected to the driven section of the shaft, the drive means providing rotational drive to the shaft; and a disc cutter mounted on the mounting section of the shaft and axially aligned with the mounting axis such that rotation of the shaft induces a lateral oscillation of the disc cutter about the shaft rotation axis; a bearing disposed between the disc cutter and the mounting section to provide free axial rotation of the disc cutter with respect to the shaft about the mounting axis; wherein the cutting disc includes a circumferential workface engaging periphery; an inertial reaction mass connected to the housing, the mass relatively large in proportion to the disc cutter.

500735718_2.DOC 00 3 Preferably, the inertial reaction mass is disposed to have a center of mass substantially aligned with the impact force created upon engagement of the disc cutter with the workface.

O Preferably, the inertial reaction mass is annular and substantially surrounds the disc cutter.

IND Preferably, the inertial reaction mass includes a plurality of stacked iron and/or lead plates.

Preferably, the inertial reaction mass is provided to stabilize the disc cutter and provide inertial absorption of peak impact forces of the cutter on the workface and effect rock Scutting generally radially from the disc cutter periphery.

Preferably, the axial bearing system includes a primary bearing substantially aligned with a load path of the disc cutter and a secondary bearing provided to preload the primary bearing.

Preferably, a reaction force created by engagement of the rock face is substantially along the line extending through the primary and secondary bearings.

Preferably, the cutting disc periphery includes a plurality of removable cutting bits.

Preferably, the cutting disc periphery comprises a substantially continuous cutting ring.

Preferably, the cutting disc periphery defines a leading tip and a trailing heel, the leading tip being movable along a path that is substantially parallel to the rock face and substantially perpendicular to the oscillation axis to effect rock boring, the trailing heel of the disc cutter being spaced from the rock face during cutting.

In accordance with a second aspect, the invention provides, a rock cutting machine including: a chassis; a boom attached to the chassis at a proximal end of the boom; and a rock cutting device according to the first aspect mounted on a distal end of the boom.

Preferably, the rock cutting device is hingedly mounted to the distal end of the boom to pivot about a wrist axis.

500735718_2.DOC 00 4 SPreferably, the boom is hingedly mounted at or adjacent the proximal end for rotation about a first boom axis to allow global pivoting of the combined boom and disc cutting device.

O Preferably, the boom is hingedly mounted at the proximal end for movement about a second boom axis, the second boom axis being disposed generally orthogonal to the first boom axis.

5 Preferably, the first boom axis is substantially vertical.

Alternatively, the first boom axis is substantially horizontal.

SPreferably, the device is rotatable about a longitudinal axis of the boom.

Preferably, a linear cutting velocity of the rotary disc cutter is controlled by interaction with a computer that processes algorithms with variable information input being provided by strain gauges and accelerometers mounted adjacent to the rotary disc cutter.

Preferably, the machine includes referencing means to reference the position of the machine with respect to the rock face, thereby allowing a predetermined depth of cut to be maintained at the rock face throughout a cutting cycle.

Preferably, the machine is anchored with respect to the rock face thereby allowing a predetermined depth of cut to be maintained at the rock face throughout a cutting cycle.

In accordance with another aspect, the invention provides, a rock cutting machine including: a chassis; a plurality of booms attached to the chassis at a proximal end of each boom; and a rock cutting device according to the first aspect mounted on each respective distal end of each boom.

For the cutting action to be initiated the leading tip of the disc should initially contact the rock at significant angle. Probably in excess of 45', but differing rock types or conditions may reduce or increase this requirement.

500735718_2.DOC 00 C tbAdvantageously, at least in a preferred form, the device of the invention can operate to cut or excavate very hard rock, with greatly reduced applied force and much higher output per disc cutter, while using less power per unit volume of rock removed. Thus the device can be mounted on a vehicle of significantly reduced weight and cost, compared, for example, to rolling edge disc cutters, while providing much greater flexibility in the geometry of excavation.

I The cutting device of the invention is not restricted to a single disc cutter, but can include more than one. For example, the cutting device may include three disc cutters arranged along the same plane, but angled at approximately 45 degrees to each other. Such an arrangement can produce a cut face of a particular shape, while the speed at which rock is removed is greatly increased. In this arrangement, each of the three disc cutters can be driven by the one drive means, or they may be driven by separate drive means. The use of multiple disc cutters is particularly useful for long wall operations.

Advantageously, at least in a preferred form the device of the invention typically requires substantially reduced applied forces relative to known rock excavating machinery. A reduction at least in respect of normal forces, in the order of one tenth is envisaged. Such low forces facilitates the use of a support structure in the form of an arm or boom, which can force the edge of the disc cutter into contact with the rock at any required angle and to manipulate the position of the disc cutter in any direction. In particular, in relation to long wall mining, the disc cutter, or array of disc cutters, may be mounted to traverse the length of the long wall face and to be advanced at each pass. Advantageously, the invention provides for entry of the disc cutter into the rock face from either a previously excavated drive in a long wall excavation, or from pre-bored access holes, or by attacking the rock at a shallow angle to the face until the required depth for the pass is achieved. With the disc cutter mounted on a movable boom, the disc cutter can be moved about the rock face to excavate that face at any desired geometry.

Advantageously, at least in a preferred form the cutting device of the invention is suitable for a range of cutting and mining operations and machinery, such long wall mining, mobile mining machines, tunnelling machines, raise borers, shaft sinkers and hard rock excavation generally.

500735718_2.DOC 00 6 tb Brief Description of the Drawings Several preferred embodiments of the invention will now be described with reference to the accompanying drawings, in which: Figure 1 is a schematic view of the rock cutting device of the preferred embodiment of the C 5 present invention and showing the manner in which it makes contact with a rock face; SFigure 2 is also a schematic view of the rock cutting device showing the manner in which it ("4 t acts to remove rock material; Figure 3 is a detailed cross-sectional side elevational view of the rock cutting device; Figure 4 is a schematic side elevational view of a rock cutting machine in accordance with the invention; Figure 5 is a plan view of the machine of Figure 4; and Figure 6 is a schematic view of another example of a rock cutting machine mounted to achieve the creation of a bore hole.

Best Modes for Carrying Out the Invention With reference to Figures 1 and 2 of the drawings, the rock cutting device 10 according to this preferred embodiment of the present invention includes a rotary disc cutter 11, that in use, is either inserted into a pilot opening formed in the rock face R, or approaches the rock face at an angle to enable entry (see Figure 1).

For this cutting action to be initiated the tip of the disc should initially contact the rock at significant angle. (Probably in excess of 45', but differing rock types or conditions may reduce or increase this requirement).

The cutting device 10 includes the disc cutter 11, is driven in an oscillating manner, and also may be driven or free to nutate. The disc cutter 11 is driven to move in this manner about separate or combined oscillating and nutating axes. The nutation angle may be varied or fixed from 00 to almost 90' (Most probably less than 50). That motion, when applied to the rock face, will cause the disc cutter to apply force to the rock that promotes cracks which 500735718_2.DOC 00 7 Spropagate toward the rock face adjacent the opening (see Figure By this mechanism rock fragments or chips 12 can be separated from the rock when a crack 13 propagates from the wall of the opening to the adjacent rock face. The crack will propagate from a pressure bulb 14 created by the motion of the oscillation, nutation or combination of both motions.

O 5 This cutting action enables the rock to fail in tension rather than the current traditional compressive first then tension technique. This phenomenon significantly reduces the supporting structure mass for the proposed technology.

Advantageously, the nutating motion of the disc cutter also lends to promote separation of the rock segments from the rock face and may assist sharpening of the contact point of the rotatably mounted disc. Because the disc is rotatably mounted, during each oscillation, the disc will precess. This action provides a new portion of the consumable portion of the disc to the rock and also will assist to distribute the temperature created due to the interaction of the disc and the rock. The cutting action of the tip 15 of the disc will require that the heel 16 of the disc does not contact the rock. To accomplish this a positive rake angle must be achieved. This angle may be fixed or varied depending upon the operational mechanism.

This angle may also be varied depending upon the rock type of characteristics. The variables being monitored by assessment of the forces within the drive mechanism and surrounding support structure, and the results applied to algorithms in an allied computer control system. Depending upon the result of the interpretation of the data, the computer can act to alter angle f by providing a suitable signal to an electro-mechanical actuator that can provide the required force to alter the angle of the disc during the cutting action.

A rock cutting device according to the invention principally will bore a groove in the rock at circa the diameter of the disc, and at the depth of plunge into the rock. The cutter excavates the rock by generating cracks in the rock and separating rock segments formed by the cracks. However, rock normally will also be removed by the abrasive action of the cutting tips against the rock and the nutating motion of the disc cutter against the rock will also facilitate removal of rock in this manner.

However, the amount of rock removed by this mechanism is relatively small. This rock is in the zone referred to previously as the pressure bulb 14.

500735718_2.DOC 00

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8 o Currently the pressure bulb area or disc to rock contact zone is cooled and airborne dust is Z controlled by the addition of low-pressure water (Less than 10 Bar) applied through the disc via a series of holes. This coolant could also be applied from an external source so that it is directed to contact the tip of the disc area. It may be possible to increase the performance of the system by directing high-pressure water (Probably above 200 Bar) at the pressure bulb area. This jet could be applied either perpendicular to the direction of travel, or in line with the axis of travel, or any angle in between. The water jet indicated as 17 in Figure 2 may enter the crack that is propagating from the pressure bulb and apply a force in equal and all Sdirections, thereby forcing the rock chip to break to the free air side.

The disc cutter of the boring device preferably has a circular, rock engaging periphery, and may include a plurality of cutting tips which are removably connected to the cutter, but could be permanently connected.

Preferably, those tips extend from the disc cutter at or adjacent to the circular periphery thereof either radially, axially, or in a combination of both. The cutting tips can be formed of any suitable material, abrasion resistant, with inherent toughness such as tungsten carbide, alloy and hardened steel, possibly ceramic or other, depending on the type of rock being bored. They can also have any suitable shape and can be fixed to the disc cutter in any suitable manner. The cutter may also be contiguous and be produced of any or a combination of the materials mentioned.

The oscillating movement of the disc cutter can be generated in any suitable manner. This motion may be direct mechanical means, or by poly-phase hydraulic pump and motor combination.

With reference to Figure 3 of the drawings the cutting device 10 includes a mounting assembly 17 as well as the rotary disc cutter 11. The mounting assembly 17 includes a mounting shaft 18 which is rotatably mounted within a housing 19, that can constitute or be connected to a large mass for impact absorption. The housing 19 thus, can be formed of heavy metal or can be connected to a heavy metallic mass. The shaft 18 is mounted within the housing 19 by a bearing 20, which can be of any suitable type and capacity. The bearing 500735718_2.DOC 00 9 b) 20 is mounted in any suitable manner known to a person skilled in the art, such as against a stepped section 21.

O The housing 19 can have any suitable construction, and in one form includes a plurality of metal plates fixed together longitudinally of the shaft 18. With one such arrangement, the r, 5 applicant has found that a plurality of iron and lead plates provides effective impact absorption based on weight and cost considerations.

t The shaft 18 is mounted for rotating motion about a central longitudinal axis A-A. The shaft 18 includes a driven section 21 and a mounting section 22. The driven section 21 is connected to drive means 23 at the end thereof remote from the mounting section by any suitable connectors, such as heavy duty threaded fasteners 24, while a seal 25 is applied between the facing surfaces of the mounting section and the drive means.

The drive means 23 can take any suitable form and the means shown in Figure 3 is a shaft that may be driven by a suitable engine or motor. The drive means 23 is mounted within the housing 19 by bearings 26, which are tapered roller bearings, although other types of bearings, either anti friction, plain hydrostatic, or hydrodynamic, that provide radial and axial force reaction could also be employed. With one typical arrangement, the bearings 26 are mounted against a stepped section 27 of the drive means 23 and against a mount insert 28 which is also stepped at 29. The mount insert 28 is fixed by threaded connectors 30 to the housing 19, and fixed to the mount insert 28 by further threaded connectors 31 is a sealing cap 32 which seals against the drive means 23 by seals 33. The sealing cap 32 also locates the outer race 34 of the bearings 26 by engagement therewith at 35, while a threaded ring 36 locates the inner race 37.

The mounting section 22 is provided for mounting of the disc cutter 11 and is angularly offset from the axis A-A of the driven section 21, which generally will be approximately normal to the rock face being excavated. The axis B-B of the mounting section 22 is shown in Figure 3 and it can be seen that the offset angle 0 is in the order of a few degrees only.

The magnitude of the offset angle 0 determines the size of the oscillating and nutating movements of the disc cutter I I and the angle 0 can be arranged as appropriate. The angle 0 500735718_2.DOC 00 Oil could be zero, but the axis of the eccentric section offset from the A-A axis (Fig This would provide oscillation but no nutation.

0 The disc cutter 11 includes an outer cutting disc 38 that is mounted on a mounting head 39 by suitable connecting means, such as threaded connectors 40. The outer cutting disc 38 could include a plurality of tungsten carbide cutting bits 41 which are fitted to the cutting disc matrix in any suitable manner. Alternatively, a tungsten carbide ring could be Semployed. The outer cutting disc can be removed from the cutting device for replacement or reconditioning, by removing the connectors The disc cutter 11 is rotatably mounted on the mounting section 22 of the mounting shaft 18. The disc cutter 11 is mounted by a tapered roller bearing 42, that is located by a step 43 and a wall 44 of the mounting head 39. An incline surface 45 of the mounting head 39 is disposed closely adjacent a surface 46 of a mounting insert 47. The surfaces 45 and 46 are spaced apart with minimum clearance to allow relative rotating movement therebetween and the surfaces have a spherical curvature, the centre of which is at the intersection of the axes A-A and B-B.

A seal 48 is located in a recess 49 of the surface 45 to seal against leakage of lubricating fluid from between the mounting shaft 18, and the housing 19 and the disc cutter 11. A channel 50 is also provided in the surface 45 outwardly of the seal 48 and ducts 51 connect the channel 50 to a further channel 52 and a further duct 53 extends from the channel 52 to a front surface 54 of the outer cutting disc 38. Pressurised fluid can be injected into the various channels and ducts through the port 55 and that fluid is used to flush the underside of the cutting disc 38 as well as the relative sliding surfaces 45 and 46.

The disc cutter 11 is rotatably mounted to the mounting section 22 of the mounting shaft 18 by the tapered roller bearing 42 and by a further tapered roller bearing 56. The bearing 56 is far smaller than the bearing 42 for the reason that the large bearing 42 is aligned directly in the load path of the disc cutter and thus is subject to the majority of the cutter load. The smaller bearing 56 is provided to pre-load the bearing 42.

5007357182.DOC 00 C~ 11 t) The bearing 56 is mounted against the inner surface of the mounting shaft 18 and the outer surface of a bearing loading facility, comprising a nut 57 and a preloading shaft 58.

Removal of the outer cutting disc 38 provides access to the nut 57 for adjusting the pre-load of the bearing 56.

N 5 The nutating movement of the disc cutter 11, occurs simultaneously with the oscillating motion and that nutating movement is movement in which a point on the cutting edge of the C disc cutter is caused to move sinusoidally, in a cyclic or continuous manner as the disc cutter rotates. This movement of the disc cutter applies an impact load to the rock surface 7 under attack, that causes tensile failure of the rock.

The direction of impact of the disc cutter against the rock under face is reacted through the bearing 42 and the direction of the reaction force is substantially along a line extending through the bearing 42 and the smaller bearing 56.

The cutting device of the invention is not restricted to a single disc cutter, but can include more than one. For example, the cutting device may include three disc cutters arranged along the same plane, but at approximately 450 to each other. Such an arrangement can produce a bore of a particular shape, while the speed at which rock is removed is greatly increased. In this arrangement, each of the three disc cutters can be driven by the one drive means, or they may be driven by separate drive means.

Alternatively with reference to Figures 4 and 5 the cutting device 10 may be mounted on a moveable boom 58 to enable the disc cutter 11 to be moved about the pilot opening as that opening is enlarged. In this arrangement the housing, and impact absorption mass (if provided) may also be mounted on the boom. The boom may be elevated by an actuator 59 to tilt about a horizontal axis X and pivotable laterally via a turntable 63 about a vertical axis Z by extension and retraction of a pair of rams 64 and 65 extending from cradle 66 to either side of the turntable 63 and mounted on a chassis 70. The boom 58 has shaft 67 therethrough which in turn carries a connector 68 to which the cutting device 11 is pivotably connected at W. The shaft 67 can rotate about its longitudinal axis Y. As a consequence of the pivot axes W, X, Y and Z, the cutting device can be positioned through a whole range of orientations including over one arc dictated by a short radius RI about pivot axis W and an 500735718_2.DOC 00 N 12 Sarc dictated by a larger radius R 2 about pivot axes X and Z. The entire assembly would be anchored by a clamping means. This may be by vertical anchoring, horizontal anchoring or by application of a mass or adhesive mechanism to ensure the entire vehicle is in a finite position prior to commencing the first cut. Subsequent cuts at the rock face must be ID 5 referenced to the previous cut to ensure a predetermined depth of cut is maintained. To increase the depth of cut beyond the design limit will cause the surrounding mechanism to engage the rock and stall or cease the cutting action.

(Ni This indexing and the geometry to cut the face can be composed by computer control in N order to provide appropriate speed of operation.

With reference to Figure 6 of the drawings, in a still further arrangement, a pair of boring devices 10 may be mounted on separate booms 60 and the disc cutters are swept in an arc across the rock face and about pivot points 69, to continually remove successive layers of rock from the face. The entire machine platform 61 must be securely anchored within the bore by gripping mechanisms 62.

The disc cutters of each device is arranged to sweep in an arc across the rock face being excavated in a first direction D, and having completed that sweep, return in the reverse direction D 2 with each sweep of the disc cutters removing a layer of the rock face.

Entrance of the disc cutters into the rock for each successive pass, may be at the cusp C between adjacent concave sections formed by the sweep of each disc cutter.

The complete machine for the purpose of excavating a tunnel should be mobile and may be mounted on a crawler or on wheels. Providing the carrier or supporting vehicle will fit into the hole size selected, the opening in the rock can be from completely circular at the minimum end of the cutting shape spectrum, to somewhat ovoid. However most customers currently prefer to have a flat floor to enable them to operate subsequent vehicles.

500735718 2.DOC

Claims (17)

1. A rock boring device including: a housing; a shaft mounted within said housing for rotation about a longitudinal shaft rotation axis, said shaft having a driven section and a mounting section, said mounting Ssection including a mounting axis, parallel to and spaced from said shaft rotation axis; rotational drive means connected to said driven section of said shaft, said drive means providing rotational drive to said shaft; and a disc cutter mounted on said mounting section of said shaft and axially aligned with said mounting axis such that rotation of said shaft induces a lateral oscillation of the disc cutter about the shaft rotation axis; a bearing disposed between said disc cutter and said mounting section to provide free axial rotation of the disc cutter with respect to the shaft about the mounting axis; wherein said cutting disc includes a circumferential workface engaging periphery; an inertial reaction mass connected to said housing, said mass relatively large in proportion to the disc cutter.

2. A rock cutting machine according to claim 1, wherein the inertial reaction mass is disposed to have a center of mass substantially aligned with the impact force created upon engagement of the disc cutter with the workface.

3. A rock cutting machine according to claim 1 or 2, wherein the inertial reaction mass is annular and substantially surrounds the disc cutter.

4. A rock cutting machine according to any one of the preceding claims, wherein the inertial reaction mass includes a plurality of stacked iron and/or lead plates. 500735718_2.DOC 00 14 A rock cutting machine according to any one of the preceding claims, wherein the inertial reaction mass is provided to stabilize the disc cutter and provide inertial absorption of peak impact forces of the cutter on the workface and effect rock cutting generally radially from said disc cutter periphery. ,I 5 6. A rock cutting device according to any one of the preceding claims, further including an axial bearing system to distribute axial loads from the disc to the housing.

7. A rock cutting device according to claim 6, wherein said axial bearing system includes a primary bearing substantially aligned with a load path of the disc cutter and a secondary bearing provided to preload the primary bearing.

8. A rock cutting device according to claim 7, wherein a reaction force created by engagement of the rock face is substantially along the line extending through the primary and secondary bearings.

9. A rock cutting device according to any one of the preceding claims, wherein the cutting disc periphery includes a plurality of removable cutting bits.

10. A rock cutting device according to any one of claims 1 to 8, wherein the cutting disc periphery comprises a substantially continuous cutting ring.

11. A rock boring device according to any one of the preceding claims wherein the cutting disc periphery defines a leading tip and a trailing heel, the leading tip being movable along a path that is substantially parallel to the rock face and substantially perpendicular to the oscillation axis to effect rock boring, the trailing heel of the disc cutter being spaced from said rock face during cutting.

12. A rock cutting machine including: a chassis; a boom attached to said chassis at a proximal end of said boom; and a rock cutting device according to any one of the preceding claims mounted on a distal end of said boom. 500735718_2.DOC 00 S13. A rock cutting machine according to claim 12, wherein said rock cutting device is hingedly mounted to the distal end of the boom to pivot about a wrist axis. O 14. A rock cutting machine according claim 12 or 13, wherein the boom is hingedly mounted at or adjacent the proximal end for rotation about a first boom axis to allow N 5 global pivoting of the combined boom and disc cutting device. A rock cutting machine according to any one of claims 12 to 14 wherein the boom is t hingedly mounted at the proximal end for movement about a second boom axis, said Ssecond boom axis being disposed generally orthogonal to said first boom axis.

16. A rock cutting machine according to claim 14, wherein said first boom axis is substantially vertical.

17. A rock cutting machine according to claim 14, wherein said first boom axis is substantially horizontal.

18. A rock cutting machine according to any one of claims 12 to 17, wherein said device is rotatable about a longitudinal axis of said boom.

19. A rock cutting machine according to any one of claims 12 to 18, wherein a linear cutting velocity of said rotary disc cutter is controlled by interaction with a computer that processes algorithms with variable information input being provided by strain gauges and accelerometers mounted adjacent to said rotary disc cutter. A rock cutting machine according to any one of claims 12 to 19, including means to reference the position of the machine with respect to the rock face, thereby allowing a predetermined depth of cut to be maintained at said rock face throughout a cutting cycle.

21. A rock cutting machine according to any one of claims 12 to 120, wherein said machine is anchored with respect to said rock face thereby allowing a predetermined depth of cut to be maintained at said rock face throughout a cutting cycle.

22. A rock cutting machine including: a chassis; 500735718 2.DOC 16 a plurality of booms attached to said chassis at a proximal end of each boom; and a rock cutting device according to any one of claims 1 to 11 mounted on each respective distal end of each boom.

23. A rock cutting machine substantially as herein described with reference to any one of the embodiments of the invention illustrated in the accompanying drawings and/or examples. 500735718 2.DOC