GB2609282A - Disc cutter - Google Patents

Abstract

A disc cutter comprising a cutter body 300 having an axis of rotation, a plurality of tool holders and a plurality of cutting elements, the tool holders and cutting elements arranged in at least one set about the cutter body, each set comprising a plurality of tool holders arranged in first 302a, second 302b, third 302c positions and so on 302d, said positions being in sequential order one behind the other in the direction of rotation, each tool holder supporting one or more of the plurality of cutting elements, the cutting elements being provided in a pre-determined sequence of configurations from first position to last position, wherein in the pre-determined sequence of configurations the quantity of cutting elements and/or the lateral spacing of the cutting elements varies, the disc cutter further comprising a tool holder stabilising system for reducing vibration of the cutting elements during use (fig. 28).

Description

DISC CUTTER

Field of the Invention

The present disclosure relates to a rotatable disc cutter for use in an excavation machine finding utility in mining, construction, trenching, and tunnel boring applications. In particular, it relates to a disc cutter comprising superhard cutting elements mounted in tool holders around a peripheral edge of the disc cutter.

Backqround WO 2019/180164 Al, WO 2019/180169 Al and WO 2019/180170 Al each disclose a cutting assembly for use in above and below ground quarries and mines. The cutting assembly is typically used to extract slabs of rock from the ground, before the slabs are taken for further processing, such as polishing.

Each cutting assembly comprises a circular disc cutter, which is moveable between horizontal and vertical cutting orientations. Referring initially to Figures 1 and 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.

As 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 disc cutters 18 fixed about the drive spindle 16.

In a second example, 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 disc cutters 18 is mounted to the drive spindle 16, distributed either side of the single support arm 14.

The base unit 12 functions as a transport system for the disc cutter 18. The base unit 12 is moveable to advance and retract the disc 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 disc 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 disc cutter 18 are correspondingly horizontal.

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.

In use, the disc cutter 18 is brought into contact with the rock formation 2 and rotation of the drive spindle 16, and therefore its disc 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, the size of which depends 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.

A problem with the assemblies described above is that cutting generates vibrations that transmit through the cutting assembly. These vibrations can lead to damaged cutting elements on the cutting assembly, and therefore shortened service life.

It is an object of the invention to provide a cutting assembly which minimises damage to the cutting elements caused by vibrations experienced during cutting.

Summary of the Invention

According to the invention, there is provided a disc cutter comprising a cutter body having an axis of rotation, a plurality of tool holders and a plurality of cutting elements, the tool holders and cutting elements arranged in at least one set about the cutter body, each set comprising a plurality of tool holders arranged in first, second, third positions and so on, said positions being in sequential order one behind the other in the direction of rotation, each tool holder supporting one or more of the plurality of cutting elements, the cutting elements being provided in a pre-determined sequence of configurations from first position to last position, wherein in the pre-determined sequence of configurations the quantity of cutting elements and/or the lateral spacing of the cutting elements varies, the disc cutter further comprising a tool holder stabilising system for reducing vibration of the cutting elements during use.

Optional and/or preferable features of the invention are provided in the dependent claims.

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 an example of a prior art 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 further example of a prior art 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 is a perspective view of an example disc cutter; Figure 6 is a side view of a cutter body forming part of the disc cutter of Figure 5; Figure 7 is a front view of a set of tool holders and cutting elements forming part of the disc cutter of Figure 5; Figure 8 is an exploded partial view of the disc cutter of Figure 5; Figure 9 is a top view of the disc cutter of Figure 5; Figure 10 is another top view of the disc cutter of Figure 5; Figure 11 is a schematic front view showing the effective combined cutting face provided by the cutting elements of Figure 5; Figure 12 is a partial view of one embodiment of a disc cutter for use with the invention; Figure 13 is a partial perspective view of another embodiment of a disc cutter for use with the invention; Figure 14 is a plan view of an example of a tool holder for use in the disc cutter of Figure 12 or 13; Figure 15 is a plan view of another embodiment of a tool holder for use in the disc cutter of Figure 12 or 13; Figure 16 is a schematic front view showing the spatial distribution of the cutting faces provided by the cutting elements of Figure 13 when incorporating at least one tilt cutting element; Figure 17 is a partial perspective view of another embodiment of a disc cutter for use with the invention, Figure 18 is a schematic front view showing the effective combined cutting face provided by the cutting elements of Figure 17; Figure 19 is a schematic perspective view showing the equivalent combined cutting face provided by the cutting elements of Figure 17; Figure 20 is a schematic front view showing the spatial distribution of the cutting faces provided by the cutting elements of Figure 17, when incorporating at least one tilt cutting element; Figure 21 is a side view of a tool holder and cutting element, with a 20 degree back rake angle (Figure 21a) and with a 10 degree back rake angle (Figure 21b); Figure 22 is a line graph showing normal and cutting forces over time for a tool holder and cutting element, with a 20 degree back rake angle and with a 5 degree back rake angle; Figure 23 is a bar chart showing averaged normal and cutting forces for a tool holder and cutting element, with a 20 degree back rake angle and with a 5 degree back rake angle; Figure 24 is a side view of a tool holder and cutting element positioned at a first height (Figure 24a) and at a greater, second height (Figure 24b); Figure 25 is the schematic front view showing the spatial distribution of the cutting faces provided by the cutting elements of Figure 13 when incorporating at least one tilt cutting element, and shows in particular the relative height of the tilt cutting element compared to the remaining cutting elements in the set; Figure 26 is a perspective view of an embodiment of the cutter body, which forms part of a tool holder stabilising system; Figure 27 is a perspective view of an alternative embodiment of the disc cutter, with the tool holder enlarged for clarity; Figure 28 is a partial perspective view of the disc cutter of Figure 27, showing in particular how the tool holder is mounted to the cutter body and secured using rolled pins; Figure 29 is a side view of an alternative embodiment of the tool holder stabilising system; Figure 30 is a side view of another embodiment of the tool holder stabilising system; Figure 31 is a side view of another embodiment of the tool holder stabilising system; Figure 32 is a side view of another embodiment of the tool holder stabilising system, Figure 33 is a partial perspective view of a cutting assembly incorporating an embodiment of a base unit stabilising system, showing in particular a pair of stabilising outriggers that extend outwardly an angle of approximately 45 degrees to the vertical orientation of the cutting assembly when in the ground-engaging position; Figure 34 is a partial perspective view of a cutting assembly incorporating another embodiment of a base unit stabilising system, showing in particular a pair of stabilising outriggers that extend in parallel with the vertical orientation of the cutting assembly when in the ground-engaging position; Figure 35 is a partial perspective view of a cutting assembly incorporating another embodiment of a base unit stabilising system, showing in particular a pair of stabilising outriggers that extend perpendicularly to the vertical orientation of the cutting assembly when in the ground-engaging position; Figure 36 is a partial perspective view of a cutting assembly incorporating another embodiment of a base unit stabilising system, showing in particular a pair of short stabilising legs that extend perpendicularly to the vertical orientation of the cutting assembly when in the ground-engaging position; Figure 37 is a partial perspective view of a cutting assembly incorporating another embodiment of a base unit stabilising system, showing in particular a pair of long stabilising legs that extend perpendicularly to the vertical orientation of the cutting assembly when in the ground-engaging position; Figure 38 is a partial perspective view of a cutting assembly incorporating another embodiment of a base unit stabilising system, showing in particular a support frame when in the ground-engaging position; Figure 39 is a perspective view of an embodiment of a machine locking system, and shows in particular an inflatable balloon element; Figure 40 is a perspective view of another embodiment of a machine locking system, and shows in particular a claw member, and Figure 41 is a perspective view of another embodiment of a machine locking system, and shows in particular a hydraulic support system.

10 15 20 25 In the drawings, similar parts have been assigned similar reference numerals.

Detailed Description

Figure 5 shows an example of a disc cutter 18, which comprises a generally 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 disc cutter 18.

The disc cutter 18 comprises a plurality of tool holders 24 for each receiving at least one cutting element 22. In this example, there is a repeating set of four tool holders 24 and seven cutting elements 22. There are forty-two cutting elements 22 in total. Each set is repeated identically about the circular body 20. In each set, there are four different spatial configurations of tool holder 24 and cutting element 22, as explained in more detail below. When arranged in sequence, one behind the other in the direction of rotation of the disc cutter 18, the required cutting force of the disc cutter 18 is significantly reduced.

Each tool holder 24 comprises a body portion 26 and a pair of spaced apart legs 28 extending from the body portion 26. The body portion 26 is generally cuboidal. The body portion 26 hosts the or each cutting element 22. Each leg 28 of the pair of legs is plate-like. The legs 28 are spaced apart by a gap 30, which enables coupling of the tool holder 24 either side of the circular body 20. A plurality of slots 32 are positioned periodically along the circumferential surface 34 of the generally circular body 20, as shown in Figure 6. Each slot 32 becomes occupied with said gap 30 when the tool holder 24 is mounted on the circular body 20. Two sets of nuts and bolts are used to secure each tool holder to the body 20, the bolts passing through apertures 44 on the body 20 and apertures 46 in the legs 28. The slots 32 reduce the shear force on the bolts during use. By virtue of the circumferential surface 34 of the circular body 20 extending between neighbouring slots 32, tool holders 24 are regularly spaced apart around the circular body 20. In this example, twenty-four slots are provided for twenty-four tool holders 24.

Turning now to Figure 7, the tool holder 24 tapers inwardly from a first end 36, proximate the or each cutting element 22, towards a second end 38, proximate a free end of each leg 28.

A first variant of the tool holder 24 is shown in Figure 7a, which is configured to seat a single, (axially) centrally mounted, cutting element 22.

A second variant of the tool holder is shown in Figure 7b, which is configured to seat two adjacent cutting elements 22.

A third variant of the tool holder 24 is shown in Figure 7c, which is configured to seat two spaced apart cutting elements 22.

A fourth variant of the tool holder 24 is shown in Figure 7d, which is configured to seat two spaced apart cutting elements 22 with a central recessed channel 40 between the two cutting elements 22. The elongate channel 36 extends in the direction of intended rotation of the disc cutter 18 -see Figure 10.

Preferably, the tool holders are arranged in the following sequence: d), c), b), a) as shown in Figure 8. However, any ordering within the sequence is envisaged provided that all four tool holder configurations are used. For example, see Table 1.

Position within sequence First Second Third Fourth Tool holder configuration a b c d a b d c a c b d a c d b a d b c

Table 1

It is also feasible to use sets containing two, three or more configurations of tool holder(s) and cutting element(s). The size of each cutting element 22 and the spacing between the cutting elements, if more than one cutting element is used on a particular tool holder 24, will need to be adjusted accordingly.

The cutting elements 22 in each set produce an overlapping cut, indicated generally at 42, in the rock, as shown in Figure 11. This evenly distributes the cutting force on the cutting slot.

The overlapping cut in the main embodiment is 60 mm, and this is based on four tool holder and cutting element combinations within each set. If a larger overlapping cut is required, more tool holder and cutting element combinations would be used, for example, six, eight, ten, twelve etc. If a smaller overlapping cut is required, less tool holder and cutting element combinations would be required, for example two or three.

Figure 12 shows one embodiment of a disc cutter at 100. The disc cutter 100 comprises a set of six tool holders 102. Cutting elements 104 mounted on the tool holders 102 are arranged in a pre-determined sequence. The total quantity of cutting elements 104 in each set is eleven. Multiple sets are mounted about the disc body. The quantity and spacing of the cutting elements depends on the position of the tool holder 102 in the set. The tool holder in first position, designated 102a leads the set. The tool holder in second position is designated 102b. The tool holder in third position is designated 102c. The tool holder in fourth position is designated 102d. The tool holder in fifth position is designated 102e. The tool holder in sixth position, designated 102f, trails the set. This is also a 'prime' tool holder. A prime tool holder is one that includes a tilt (or 'gauge') cutting element, which is explained in more detail below.

The tool holders 102 are similar to those described earlier with respect to Figure 7. There is a single cutting element on the tool holder 102a in first position. There are two adjacent cutting elements on the tool holder 102b in second position. There are two spaced apart cutting elements on the tool holder 102c in third position. In the last position of the sequence 102f, there are two spaced apart cutting elements on the tool holder, and a recessed channel extends between the two cutting elements. However, the set additionally contains two modified versions of tool holder c. In tool holder c', the spacing between cutting elements is greater than in tool holder c. In tool holder c", the spacing between cutting elements is greater than in tool holder c'.

The sequence is summarised in Table 2.

Position within sequence First Second Third Fourth Fifth Sixth Tool holder configuration a b c c' c" d

Table 2

Figure 13 shows another embodiment of a disc cutter 200. The disc cutter 200 comprises a set of six tool holders 202. Cutting elements 204 mounted on the tool holders 202 are again arranged in a pre-determined sequence. The total quantity of cutting elements 204 in each set is eleven. Multiple sets are mounted about the disc body. The quantity and spacing of the cutting elements 204 on each tool holder 202 depends on the position of the tool holder 202 in the set. The tool holder in first position, designated 202a leads the set. This is also a prime tool holder since it includes a tilt cutting element. The tool holder in second position is designated 202b. The tool holder in third position is designated 202c. The tool holder in fourth position is designated 202d. The tool holder in fifth position is designated 202e. The tool holder in sixth position, designated 202f, trails the set.

In this embodiment, the tool holder 202a in the first position comprises two spaced apart cutting elements. A recessed channel extends between them. The channel slopes upwardly between a leading and a trailing edge of the tool holder 202a. Tests have proved that the material between two cutting elements will gradually wear away in use. Thus, the corresponding torque and power will be higher. By removing the material between the cutting elements removed prior to first use, the unnecessary initial load is reduced and cutting occurs more smoothly. The tool holder 202b in the second position comprises two spaced apart cutting elements. There is no recessed channel extending between them. The tool holder 202c in the third position comprises two spaced apart cutting elements. These cutting elements are slightly closer together than the cutting elements on the tool holder in the second position. The tool holder 202d in the fourth position comprises two spaced apart cutting elements. These cutting elements are slightly closer together than the cutting elements on the tool holder in the third position. The tool holder 202e in the fifth position comprises two adjacent cutting elements. The tool holder 202f in the sixth position comprises a single cutting element.

The sequence is summarised in Table 3 and it is the preferred sequence.

Position within sequence First Second Third Fourth Fifth Sixth Tool holder configuration d c" c' c b a

Table 3

In brief, the sequence is a reverse of the one shown in Table 2.

Possible alternative sequences are provided in Table 4.

Position within sequence First Second Third Fourth Fifth Sixth Tool holder configuration d c" c' c b a b a d c' c c c b a d c" c' c' c b a d c" c' c' c b a d

Table 4

However, any ordering within the sequence is envisaged provided that all six tool holder configurations are used and at least one of the tool holders supports a tilt cutting element.

In this embodiment, the cutting elements are polycrystalline diamond compacts (PDCs), commonly found in the Oil and Gas industry on drill bits. Each cutting element 204 is cylindrical with a planar working face that comprises polycrystalline diamond. The working surface of each cutting element 204 are all aligned in the same direction. The cutting elements 204 all face tangentially in the direction of rotation -see Figure 13. Most of the cutting elements 204 face in a direction that is parallel and in line with the disc body. At least one of the cutting elements, designated the tilt cutting element, faces in a direction that is not parallel and in line with the plane of the disc. As an example only, in Figure 14, the tilt cutting element faces in a direction that is 5 degrees from alignment with the plane of the disc body. As a further example, in Figure 15, the tilt cutting element faces in a direction that is 21 degrees from alignment with the plane of the disc body.

The prime tool holder may be the tool holder disposed in any of the positions within the set, for example, first position, second position, third position and so on. Typically, the prime tool holder comprises two cutting elements, both of which will be tilt cutting elements, like the example shown in Figure 14. The two tilt cutting elements are ideally located furthest apart (like variants c" or d mentioned previously), to the extent possible along the lateral extent of the tool holder.

As the disc cutter 200 rotates, the first tool holder 202a is presented to the rock formation, then the second tool holder 202b, then the third tool holder 202c and so on. The cutting elements 204 supported by the tool holders 202 sequentially cut into the rock formation. The effect of the pre-configured sequence of cutting elements 204 results in the effective cutting pattern shown in Figure 16.

During use, the tilt cutting elements experience complex loads. It is therefore important to manage the load distribution on the cutting elements across the lateral extent of the tool holder. By doing so, the load on the tilt cutting elements can be minimised, thereby protecting the tilt cutting elements from damage. Such load distribution is achieved by varying the distance between cutting elements across the tool holder, and from first position through to the last position. Figure 16 shows the distance between the centreline of cutting elements from one side of the tool holder to the other side. The distances are non-uniform and vary, depending on the position of the cutting element across the tool holder. The greatest overlap between the cutting elements occurs proximate the outer cutting elements Figure 17 shows another embodiment of a disc cutter 300. The disc cutter 300 comprises a set of four tool holders 302. Cutting elements 304 mounted on the tool holders 302 are again arranged in a pre-determined sequence. The total quantity of cutting elements 304 in each set is seven. Multiple sets are mounted about the disc body. The quantity and spacing of the cutting elements 304 on each tool holder 302 depends on the position of the tool holder 302 in the set. The tool holder in first position, designated 302a leads the set. This is also a prime tool holder since it includes a tilt cutting element. The tool holder in second position is designated 302b. The tool holder in third position is designated 302c. The tool holder in fourth position, designated 302d, trails the set.

In this embodiment, the tool holder 302a in the first position comprises two spaced apart cutting elements. There is no recessed channel extending between them. The tool holder 302b in the second position comprises two spaced apart cutting elements that are closer together than the cutting elements in the first position. The tool holder 302c in the third position comprises two adjacent cutting elements. The tool holder 202d in the fourth position comprises a single cutting element.

The sequence is summarised in Table 5.

Position within sequence First Second Third Fourth Tool holder configuration c' c b a

Table 5

As the disc cutter 300 rotates, the first tool holder 302a is presented to the rock formation, then the second tool holder 302b, then the third tool holder 302c and so on. The cutting elements 304 supported by the tool holders 302 sequentially cut into the rock formation. The effect of the pre-configured sequence of cutting elements 304 results in the effective cutting pattern shown in Figure 18. This effect is equivalent to using a single tool holder and a multitude of cutting elements in a side-by-side arrangement as shown in Figure 19 but with significantly reduced forces during cutting.

Figure 20 shows the distance between the centreline of cutting elements from one side of the tool holder to the other side. As with the cutting elements in Figure 16, the load distribution on the cutting elements across the lateral extent of the tool holder 302 is managed by varying the distance between cutting elements across the tool holder 302, and from first position through to the last position.

In all embodiments, the back rake angle of the (PDC-type) cutting element is preferably between 5 degrees and 14 degrees. Ideally, the back rake angle is around 10 degrees. Figure 21 shows a comparison between a 20 degree back rake angle from a previous design (Figure 21a) and a 10 degree back rake angle (Figure 21b). By reducing the back rake angle from 20 degrees to 10 degrees, the cutting force is significantly reduced. This reduces the risk of damage to the cutting element(s).

As a further example, Figure 22 shows the cutting forces required for the 20 degree back rake angle compared with a 5 degree back rake angle over time. Both the normal force and cutting force are lower for the 5 degree back rake angle. Figure 23 summarises the data from Figure 22 and shows average normal and cutting forces; it is clear to see that the reduced back rake angle results in lower forces experienced by the cutting elements during cutting.

The forces during cutting can also be reduced by lowering the height of the tilt cutting element in the prime tool holder. Figure 24a shows a prime tool holder in which the height of the tilt cutting element has been reduced and Figure 24b shows a prime tool holder in which the height of the tilt cutting element is unchanged. This new location manifests itself in the effective cutting pattern of Figure 25, in which the height of the tilt cutting element (indicated at X) is lower than the rest of the cutting elements in the set. In this way, the tilt cutting element may be configured to only bear the side loads, thereby protecting it from damage.

In an alternative embodiment, the disc cutter 1000 further comprises a tool holder stabilising system for reducing vibration of the cutting elements during use. Vibrations generated by the effect of cutting transmit through the disc cutter and can prove catastrophic for the cutting elements. Reducing transmission of the vibrations is achieved in a number of different ways, either alone or in combination with each other, depending on the nature of the rock being cut.

In Figures 26, 27 and 28, the cutter body 1002 comprises a series of recesses 1004 set into two opposing major surfaces 1006, 1008 thereof. The series of recesses 1004 are in addition to the slots 32 mentioned earlier. The recesses 1004 are in radial alignment with the slots 32.

A tool holder 1010 is mounted in each slot 32, and in each recess 1004. The fit is such that the legs 1012 protrude axially past the major surfaces 1006, 1008; they are not flush with the major surfaces 1006, 1008-see Figure 27. Two side by side rolled pins 1014 pass through side by side holes 1016 in the tool holder legs 1012 and side by side holes 1018 in the cutter body 1002 to secure the tool holder 1010 to the cutter body 1002.

As an alternative to the rolled pins 1014, the tool holder stabilising system may comprise heavy duty bolts that extend axially through the legs 1012 of the tool holder 1010. In such an embodiment, the tool holder stabilising system preferably further comprises wear elements arranged between adjacent tool holder legs for protecting the bolts and preventing shearing.

Such wear elements are typically rectangular blocks and made from wear resistant material such as carbide. They are attached to the major surfaces and protrude axially past the bolts, thereby shielding the bolts.

Additionally or alternatively, the tool holder stabilising system may comprise radial pins 1020, as shown in Figure 29. The radial pins 1020 extend radially at least partially through the tool holder 1000 and also through the cutter body 1002. The radial pins 1020 are spaced apart circumferentially. In such an embodiment, the radial pins 1020 are in addition to the aforementioned standard pins 1014 (or heavy-duty bolts if used) that extend axially. One or more radial pins 1020 may be provided. The radial pins 1020 are mounted in the cutter body 1002, and then the tool holder 1010 is mounted onto the radial pins 1020, and then the axial pins 1014 (or heavy-duty bolts if used) are fitted. A combination of pin types provides a tight fit for all pins and minimises movement of the tool holder 1010 relative to the cutter body 1002.

In addition to the recesses 1004 or radial pins 1020 mentioned above, the tool holder stabilising system may comprise a weld joint 1022 around the tool holder 1010-see Figure 30. Using radial 1020 and axial pins 1014 together is not as good as welding, but they are better than using axial pins 1014 as a sole approach to securing the tool holders 1010 to the cutter body 1002. The disadvantage of welding the tool holder 1010 to the cutter body 1002 is that should the tool holder 1010 require replacement, more effort is required as the weld must be removed before refitting another tool holder 1010.

Where welding is used, it is in combination with the recesses 1004 mentioned above. However, the other means of reducing vibrations may be used in combination or on their own.

Optionally, the tool holders 1010 and cutting elements are mounted on the cutter body 1002 via an intermediate segment block 1024-see Figure 31. Several segment blocks 1024 are required. In such an embodiment, there is no gap between successive segment blocks 1024 and the segment blocks 1024 abut one another. The benefit of this arrangement is that it results in no impact vibration of the leading tool holder in e.g. a trench. The downside is that more tool holder material is required.

As an alternative, the tool holders 1010 and cutting elements may be mounted directly onto the cutter body 1002, i.e. without intermediate segment blocks 1024. In such an embodiment, the tool holders 1010 are mounted continuously around the circumferential surface of the cutter body 1002 -see Figure 32. As before, the benefit of this arrangement is that it results in no impact vibration of the leading tool holder. However, the downside is that should a tool holder require replacing, the whole disc cutter would need reconditioning.

Turning now to Figures 32 to 37, in order to further reduce vibration of the cutting elements during use, the cutting assembly may comprise a base unit stabilising system.

In a preferred embodiment, the base unit stabilising system comprises one or more stabilising outriggers pivotably attached to the base unit and operable between a rest position and an operable ground-engaging position.

The stabilising outriggers stabilise the base unit primarily during sustained cutting, but also during the initial phase of cutting. For example, during trenching operations, the initial cut occurs during sumping of the disc cutter 1000 as it reaches the target depth. During the subsequent phase of sustained cutting, the cutting assembly advances and the disc cutter 1000, low in the ground, proceeds to form the trench. Whilst tracking forwards, vibrations generated by cutting, but for the base unit stabilising system, could reach the cutting elements and lead to premature failure.

Optionally, the base unit stabilising system comprises two stabilising outriggers 1026, 1028 extending from the base unit, as shown in Figures 32 and 33.

The preferred configuration of the stabilising outriggers 1026, 1028 includes a hydraulic cylinder (not shown), an outrigger leg 1030 and a foot 1032 attached to the leg 1030. The outrigger leg 1030 and hydraulic cylinder are pivotally attached to the base unit via a brace enabling the stabilising outriggers 1026, 1028 to be raised and lowered to place the feet 1032 into ground engaging contact. The stabilising outriggers 1026, 1028 therefore increase the area of ground contact to stabilize the cutting assembly when the disc cutter 1000 is used. When not in use, the stabilising outriggers 1026, 1028 are retracted and rest in a generally upright vertical orientation with the base unit.

Each stabilising outrigger 1026, 1028 includes a pivot means for pivotally attaching each outrigger independently to the base unit and means for independently positioning each stabilising outrigger 1026, 1028.

Alternatively, the base unit stabilising system may comprise four stabilising outriggers extending from the base unit. In such an embodiment, adjacent outriggers are spaced apart at approximately ninety degrees from one another. In one embodiment, the base unit has four corners and a stabilising outrigger extends angularly from each corner.

Optionally, each stabilising outrigger 1026, 1028 extends at angle of approximately 45 degrees to a vertical axis of the base unit when in the operable ground-engaging position. An example of this arrangement is shown in Figure 32. The vertical axis is not intended to be interpreted as being precisely vertical -rather, it is intended to mean generally the upright orientation of the cutting assembly.

When the stabilising outrigger(s) 1026, 1028 is/are extended, the foot 1032, having a shoe 1034, is placed on the ground outside of the footprint of the base unit. For example, the foot of the right stabilising outrigger 1028 is both far in front and far to the right of the base or platform of the vehicle. Similarly, the left stabilising outrigger 1026 is both far out front and far to the left of the base unit. Together, the stabilising outriggers 1026, 1028 form a generally support area much larger than the base unit of the cutting assembly alone. This preferred orientation provides a much more stable base for the cutting assembly when used, and minimises vibrations reaching the cutting elements.

Optionally, the or each stabilising outrigger 1036, 1038 extends in parallel with a vertical axis of the base unit when in the operable ground-engaging position. An example of this arrangement is shown in Figure 33. When not in use, the stabilising outriggers 1036, 1038 are retracted into a rest position.

As mentioned above, each stabilising outrigger 1026, 1028, 1036, 1038 comprises a foot having a ground-engaging shoe 1034. In Figures 32 and 33, the ground-engaging shoe 1034 is a planar support plate.

Optionally, the or each outrigger 1040 extends at angle of approximately 90 degrees to a vertical axis of the base unit when in the operable ground-engaging position. Preferably, each stabilising outrigger 1040 comprises a foot having a ground-engaging wheel 1042. An example of this arrangement is shown in Figure 34. Although not clearly visible in the examples of Figure 34, two stabilising outriggers are provided either side of the disc cutter 1000. When not in use, the stabilising outriggers 1040 are retracted and rest in a generally upright vertical orientation with the base unit.

In an alternative embodiment, the base unit stabilising system comprises one or more stabilising legs 1044 pivotably attached to the base unit and operable between a rest position and an operable ground-engaging position, the one or each stabilising leg 1044 extending proximate to and adjacent to the disc cutter 1000. Although not clearly visible in the examples of Figure 35 and 36, a pair of stabilising legs 1044 is preferably provided, the stabilising legs 1044 extending either side of the disc cutter 1000. When not in use, the stabilising legs 1044 are retracted into a rest position, elevated off the ground.

In Figure 35, the pair of stabilising legs 1044 extends fore of the axis of rotation 1046.

In Figure 36, the pair of stabilising legs 1044 extends both fore and aft of the axis of rotation 1046.

In an alternative embodiment, the base unit stabilising system comprises a frame support 1048 pivotably attached to the base unit and operable between a rest position and an operable ground-engaging position, the frame support 1048 encircling the disc cutter 1000. An example of this arrangement is shown in Figure 37. The frame support 1048 is annular and rectangular when viewed from above. In the ground-engaging position, the frame support 1048 contacts the ground all around the disc cutter 1000. It provides good support and resistance to any of-angle movement. The only downside is that it can be harder to maintain consistent ground contact. Again, the frame support 1048 helps to minimise vibrations that can reach the cutting elements and cause damage thereto. Wien not in use, the frame support 1048 is retracted into a rest position, elevated off the ground.

The cutting assembly may form part of a cutting system together with a machine locking system operable between a transport position in which the cutting assembly is movable from its location, and a locking position in which the cutting assembly is immoveable from its location.

In one embodiment, the machine locking system comprises an inflatable balloon element 1050, the balloon element being contracted in the transport position and expanded in the locking position. It is envisaged that the inflatable balloon element fits between the base unit and a ceiling in confined spaces. When inflated, the balloon element wedges the base unit in position and prevents it from being movable, for example, see Figure 39 in the context of long wall mining. When the balloon element is contracted, the base unit is able to be relocated to another position.

In another embodiment, the machine locking system comprises a claw member 1052 with multiple digits 1054 for locking onto the ground. An example of such a claw member 1052 is shown in Figure 40. The cutting assembly (not shown) is mounted on the claw member 1052. It is envisaged that by drilling into the ground through anchor points 1056 at the end of the digits 1054, it is possible to secure the claw member 1052 to the ground. Preferably, the cutting assembly, or specifically the base unit, is rotatable with respect to the claw member 1052.

In another embodiment, the machine locking system comprises a hydraulic support system 1058 to support the cutting disc during cutting. As shown in Figure 41, the hydraulic support system 1058 comprises a support structure 1060 and also piston rods 1062 that extend to engage with the ceiling 1064 and/or floor 1066 in confined spaces such as underground mines. Preferably, the hydraulic support system 1058 is connected to the base unit, and is positioned intermediate the base unit and the disc cutter 1000.

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.

Claims (10)

1. Claims 1 A disc cutter comprising a cutter body having an axis of rotation, a plurality of tool holders and a plurality of cutting elements, the tool holders and cutting elements arranged in at least one set about the cutter body, each set comprising a plurality of tool holders arranged in first, second, third positions and so on, said positions being in sequential order one behind the other in the direction of rotation, each tool holder supporting one or more of the plurality of cutting elements, the cutting elements being provided in a pre-determined sequence of configurations from first position to last position, wherein in the pre-determined sequence of configurations the quantity of cutting elements and/or the lateral spacing of the cutting elements varies, the disc cutter further comprising a tool holder stabilising system for reducing vibration of the cutting elements during use.
2. 2 A disc cutter as claimed in claim 1, wherein the cutter body comprises a series of recesses machined in two opposing major surfaces thereof and one of said tool holders is mounted about each recess.
3. 3. A disc cutter as claimed in claim 1 or 2, wherein the tool holder stabilising system comprises axial pins.
4. 4. A disc cutter as claimed in any preceding claim, wherein the tool holder stabilising system comprises radial pins.
5. 5. A disc cutter as claimed in any of claims 2 to 4, wherein the tool holder stabilising system comprises a weld joint around the tool holder.
6. 6. A disc cutter as claimed in any preceding claim, wherein the tool holder stabilising system comprises heavy duty bolts that extend axially through the legs of the tool holder.
7. 7. A disc cutter as claimed in claim 6, wherein the tool holder stabilising system further comprises wear elements arranged between adjacent tool holder legs for protecting said bolts.
8. 8. A disc cutter as claimed in any preceding claim, wherein tool holders and cutting elements are mounted on the cutter body via an intermediate segment block.
9. 9. A disc cutter as claimed in any of claims 1 to 7, wherein tool holders and cutting elements are mounted directly onto the cutter body.
10. 10. A disc cutter as claimed in any preceding claim, at least one of the tool holders within the or each set being a prime tool holder, said prime tool holder comprising a tilt cutting element that faces in a plane forming a non-zero tilt angle a with the plane of the cutter body.