MATERIAL

TECHNICAL FIELD

This invention relates to methods and apparatus for cutting solid material or cutting and breaking solid material and particularly relates to an apparatus which can be mounted to a movable vehicle such as an excavator, bulldozer, tractor and the like and which can be used to cut into ground surfaces.

BACKGROUND ART

Many types of excavations require relatively small and manoeuvrable vehicles to which ground working implements are attached. These vehicles include excavators such as drotts and backhoes The advantage of these types of excavators is that they are manoeuvrable and self- powered.

Most excavators are provided with an excavating bucket on the end of an articulated arm. These buckets are limited in their digging capability to dirt, clay and soft rock. In the case of harder ground surfaces, it is necessary to remove the bucket and to attach other types of accessories

One type of accessory is the ripper tine This tine is formed from steel and allows penetration, fragmentation and loosening of material which cannot be dug by the bucket alone The tine can penetrate weak rock and can be used to pry embedded or jointed material so as to loosen it for subsequent removal by the bucket A disadvantage with the ripper tine is that it is not suitable for anything more than weak rock material

Another accessory which can be fitted to excavators is a transverse mounted dual cutterhead This accessory has two rotating cutters mounted to a common transverse drive shaft and to each side of a support arm The cutters are able to penetrate much stronger material than the ripper tine and have the further advantage that they leave a machined surface The accessory can remove one layer of a composite stmcture such as layer of bitumen from the surface of a concrete road The cutterhead is moderately productive but has dust emission problems and cannot be steered except towards the excavator

For hard rock, a rock hammer is provided The rock hammers are extremely common and are used to break up even the strongest type of rock, reinforced concrete staictures and the

like. A rock hammer is however extremely noisy and has excessive vibration Rock hammers have a low productivity when used with softer solid material

The ripper tine and the rock hammer also leave jagged holes which must be extensively finished if a smooth trench is required (for instance for foundation work or laying of pipes) OBJECTS OF INVENTION

It is an object of the invention to provide methods and apparatus for cutting through solid material or cutting and breaking through solid material which overcomes the abovementioned disadvantages or provide the public with a useful or commercial choice

DISCLOSURE OF INVENTION According to one embodiment o the invention there is provided a method of cutting an excavation in solid material, said method comprisin cutting the excavation in the material with two cutting wheels supported by support means wherein said cutting wheels are arranged relative to each other whereby reaction forces from the cutting ofthe excavation result in a required net force on the support means. According to another embodiment of the invention there is provided a method of cutting an excavation in solid material, said method comprising: cutting the excavation in the material with two cutting wheels supported by support means; arranging said cutting wheels relative to each other whereby reaction forces from the cutting of the excavation result in a required net force on the support means. Advantageously, the cutting wheels are arranged relative to each other prior to and/or during the cutting. It is especially advantageous to arrange the cutting wheels during the cutting.

According to a further embodiment of the invention there is provided an apparatus for cutting an excavation in solid material, said apparatus comprising two cutting wheels for cutting an excavation in the material; support means supporting the cutting wheels; and arrangement means operatively associated with the cutting wheels to arrange the cutting wheels relative to each other whereby reaction forces from cutting the excavation in the solid material result in a required net force on the support means lt is particularly advantageous for the support means to support the cutting wheels whereby at least one ofthe cutting wheels is movable relative to the support means

Advantageously, the apparatus enables the cutting wheels to be arranged relative to each other prior to and/or during the cutting lt is especially advantageous to arrange the cutting wheels during the cutting.

Generally the two cutting wheels are spaced apart from one another In one form the invention resides in an apparatus for cutting an excavation in solid material the apparatus comprising at least two spaced apart cutting assemblies, each assembly having a shaft and a cutting wheel attached to one end of the shaft, the shafts being generally parallel with respect to each other; a support frame supporting the cutting assemblies, optionally attachment means attached to the support frame which is capable of attaching the support frame to a vehicle; and arrangement means operatively associated with the cutting assemblies to arrange the cutting wheels relative to each other whereby reaction forces from cutting the excavation in the solid material result in a required net force on the support frame

Advantageously the positions ofthe cutting wheels are adjustable relative to one another Thus, as required, two cutting wheels may be arranged relative to each other whereby the position of one of the cutting wheels is side by side with the other cutting wheel. Typically the two wheels are so arranged because in this arrangement when cutting in uniform solid (e.g. uniform rock) a near zero net sidewards force on an excavator arm supporting the support frame supporting the wheels (for example) will be typically produced. In addition, as required, two cutting wheels may be arranged relative to each other whereby the position of one of the cutting wheels is at a trailing position relative to the other cutting wheel Typically the two wheels are so arranged (one wheel in a trailing position) because in this arrangement when cutting in uniform solid material (e.g. uniform rock) a non-zero sideways force on an excavator arm supporting the support frame supporting the wheels (for example) will be typically produced which may be used for steering purposes. Alternatively the two wheels are so arranged (one wheel in a trailing position) because in this arrangement when cutting in non uniform solid material (e.g non uniform rock) a near-zero sideways force on an excavator arm supporting the support frame supporting the wheels (for example) will be typically produced so as to enable a substantially straight cut. The position of a wheel in a trailing position may be adjusted as required so as to produce a non-zero steering force on an excavator arm supporting the support frame supporting

the wheels (for example) so as to enable steering while the wheels are cutting in non uniform solid material (e.g. non uniform rock). The cutting wheel at the trailing position is typically arranged so that its path at least partially intersects the path taken by the other cutting wheel so that the excavation (e.g. groove) cut by the cutting wheel in the trailing position at least partially intersects the excavation (e g groove) cut by the other cutting wheel The depth of the excavation (e.g. groove) cut by the cutting wheel in the trailing position may be substantially the same as or different from the depth of the excavation (e g groove) cut by the other cutting wheel. It is particularly advantageous that the depth of the excavation (e g groove) cut by the cutting wheel in the trailing position is substantially the same as the depth of the excavation (e.g groove) cut by the other cutting wheel, enabling, for instance, excavation to a defined plane The usual arrangement for the cutting wheels is side-by-side since non-uniform rock or the need for steering or the need for both simultaneously will be common but not usual

Alternatively the cutting wheel at the trailing position may be arranged whereby its path does not intersect the path taken by the other cutting wheel so that the excavation (e g groove) cut by the cutting wheel in the trailing position does not intersect the excavation (e.g groove) cut by the other cutting wheel The depth of the excavation (e g groove) cut by the cutting wheel in the trailing position may be substantially the same as or different from the depth of the excavation (e g groove) cut by the other cutting wheel It is particularly advantageous that the depth of the excavation (e.g groove) cut by the cutting wheel in the trailing position is substantially the same as the depth of the excavation (e g groove) cut by the other cutting wheel The two excavations (e g grooves) may be close together whereby the solid material between the two excavations (e g grooves) breaks off as a result of the cutting action of the trailing cutting wheel or alternatively, the two excavations (e g grooves) may be spaced apart a sufficient distance whereby the solid material between the two excavations (e g. grooves) does not break off as a result of the cutting action cutting action of the trailing cutting wheel, leaving two separate excavations (e g two separate grooves) in the solid material after a single pass The cutting wheels may be arranged relative to one another so that when cutting a solid material (e.g. rock) a rib of solid material (e.g rock) is left between the grooves cut by the wheels or so that no rib of solid material (e.g rock) is left between the grooves cut by the wheels because of zero overlap between leading and trailing wheels or because there is an overlap or a substantial overlap between leading and trailing wheels Excavations (e g grooves) may be arranged so that later excavations (e.g grooves) are cut deeper than earlier excavations (e g grooves) The later

cut excavations (e.g. grooves) may be parallel or non parallel with the earlier excavations (e g grooves). If parallel they may be displaced (e g laterally or sideways) relative to the earlier excavations (e.g. grooves) or alternatively, they may not be displaced (e g laterally or sideways) relative to the earlier excavations (e g. grooves) According to another embodiment of the invention there is provided a method of excavating solid material in bulk, said method comprising

(i) cutting an excavation in a portion of the material with two cutting wheels supported by support means wherein said cutting wheels are arranged relative to each other whereby reaction forces from the action of the cutting of the excavation result in a required net force on the support means,

(ii) repeating (i) a plurality of times to excavate the material in bulk

According to another embodiment of the invention there is provided a method of excavating a solid material in bulk, said method comprising

(i) cutting an excavation in a portion of the material with two cutting wheels supported by support means,

(ii) arranging said cutting wheels relative to each other whereby reaction forces from the action ofthe cutting ofthe excavation result in a required net force on the support means, and

(iii) repeating (i) and (ii) a plurality of times to excavate the material in bulk

According to a further embodiment of the invention there is provided a method of excavating a solid material by a cutting and breaking action, said method comprising excavating the material by a cutting and breaking action with two cutting and breaking wheels supported by support means wherein said cutting and breaking wheels are arranged relative to each other whereby reaction forces from the excavating result in a required net force on the support means According to a further embodiment of the invention there is provided a method of excavating a solid material in bulk by a cutting and breaking action, said method comprising

(i) excavating a portion of the material by a cutting and breaking action with two cutting and breaking wheels supported by support means wherein said cutting and breaking wheels are arranged relative to each other whereby reaction forces from the excavating result in a required net force on the support means, and

<s (ii) repeating (i) a plurality of times to excavate the material in bulk

According to another embodiment of the invention there is provided a method of excavating a solid material by a cutting and breaking action, said method comprising

(i) excavating the material by a cutting and breaking action with two cutting and breaking wheels supported by support means; and

(ii) arranging said cutting and breaking wheels relative to each other whereby reaction forces from the excavating result in a required net force on the support means

According to another embodiment of the invention there is provided a method of excavating a solid material in bulk by a cutting and breaking action, said method comprising (i) excavating a portion of the material by a cutting and breaking action with two cutting and breaking wheels supported by support means,

(ii) arranging said cutting and breaking wheels relative to each other whereby reaction forces from the excavating result in a required net force on the support means, and

(iii) repeating (i) and (ii) a plurality of times to excavate the material in bulk Advantageously, the cutting and breaking wheels are arranged relative to each other prior to and/or during the cutting It is especially advantageous to arrange the cutting and breaking wheels during the cutting

According to a further embodiment of the invention there is provided an apparatus for excavating a solid material by a cutting and breaking action, said apparatus comprising two cutting and breaking wheels for excavating the material by a cutting and breaking action, support means supporting the cutting and breaking wheels, and arrangement means operatively associated with the cutting and breaking wheels to arrange the cutting and breaking wheels relative to each other whereby reaction forces from the excavating the solid material result in a required net force on the support means It is particularly advantageous for the support means to support the cutting and breaking wheels whereby at least one of the cutting and breaking wheels is movable relative to the support means.

Advantageously, the apparatus enables the cutting and breaking wheels to be arranged relative to each other prior to and/or during the cutting and breaking lt is especially advantageous to arrange the cutting and breaking wheels during the cutting and breaking

The arrangement means may also be at least part of the support means

In one form the invention resides in an apparatus for excavating solid material by a cutting and breaking action the apparatus comprising at least two spaced apart cutting and breaking assemblies, each assembly having a shaft and a cutting and breaking wheel attached to one end of the shaft, the shafts being generally parallel with respect to each other, a support frame assembly supporting the cutting and breaking assemblies, optionally attachment means to attach the support frame assembly to a vehicle; and arrangement means operatively associated with the cutting and breaking assemblies to arrange the cutting and breaking wheels relative to each other whereby reaction forces from excavating the solid material result in a required net force on the support frame assembly

Advantageously, the step of excavating comprises forming one or more grooves, one or more channels, one or more slits, one or more furrows, one or more gouges, or one or more gutters, or a combination thereof Typically when the step of excavating is conducted once, one or two of grooves, channels, slits, furrows, gouges, gutters, or a combination thereof is/are formed in the solid material When the step of excavating is repeated a plurality of times, a plurality of grooves, channels, slits, furrows, gouges, gutters, or a combination thereof may be formed in the solid material and/or the grooves, channels, slits, furrows, gouges, gutters, or a combination thereof, formed by the first excavation/step of excavating may be deepened and/or widened and/or lengthened and/or crossed with the subsequent steps of excavating

Generally the two cutting and breaking wheels are spaced apart from one another Advantageously the cutting and breaking wheels are arranged relative to each other whereby the position of one of the cutting and breaking wheels is at a trailing position relative to the other cutting and breaking wheel The cutting and breaking wheel at the trailing position is arranged so that its path at least partially intersects the path taken by the other cutting and breaking wheel so that the excavation (e g groove) cut by the cutting and breaking wheel in the trailing position at least partially intersects the excavation (e g groove) cut by the other cutting and breaking wheel The depth of the excavation (e g groove) cut by the cutting and breaking wheel in the trailing position may be substantially the same as or different from the depth of the excavation (e.g groove) cut by the other cutting and breaking wheel It is particularly advantageous that the depth of the excavation (e g groove) cut by the cutting and breaking wheel in the trailing position is substantially the same as the depth of the excavation (e g

X groove) cut by the other cutting and breaking wheel, enabling, for instance, excavation to a defined plane

Alternatively the cutting and breaking wheel at the trailing position is arranged whereby its path does not intersect the path taken by the other cutting and breaking wheel so that the excavation (e g groove) cut by the cutting and breaking wheel in the trailing position does not intersect the excavation (e g groove) cut by the other cutting wheel The depth of the excavation (e g groove) cut by the cutting and breaking wheel in the trailing position may be substantially the same as or different from the depth of the excavation (e g groove) cut by the other cutting wheel It is particularly advantageous that the depth of the excavation (e g groove) cut by the cutting and breaking wheel in the ti ailing position is substantially the same as the depth of the excavation (e g groove) cut by the othei cutting wheel The two excavations (e g two grooves) may be close together whereby the solid material between the two excavations (e g two grooves) breaks off as a result of the cutting action of the trailing cutting and breaking wheel or alternatively, the two excavations (e g two grooves) may be spaced apart a sufficient distance whereby the solid material between the two excavations (e g two grooves) does not break off as a result ofthe cutting action cutting action o the trailing cutting wheel, leaving two separate excavations in the solid material after a single pass

The effective distance between the peripheries of the two cutting wheels or the two cutting and breaking wheels (such as for instance the gap between adiacent peripheral teeth or picks on adjacent wheels) is generally small enough that the solid material (e g rock) web between the two wheels will break free when the wheels are in operation cutting/breaking the material The effective distance required to attain this will depend on the material being cut, the stronger and/or less fractured the material the narrower the effective distance Typically the effective distance is 1 -200mm, more typically - ] 00mm, even more typically 30-75mm, yet even more typically 40 - 60mm, more typically 45 - 55mm and advantageously about 50mm

Typically when excavating a solid material one or a plurality of excavations (e g grooves) (e g 2- 10,000) which may be overlapping or non overlapping, adiacent or non adjacent, parallel or non parallel, are formed in the solid material by repeating a method of the invention a plurality of times in order to excavate the required amount of material from the solid material

The apparatus and methods of the invention have many applications such as in excavations for roadworks, foundations, carpai k excavations, foi mmg trenches including

trenches for pipe laying, foundations, and may be used for trimming purposes including trimming tunnels, and the like and in mining for excavating solid material such as coal, or rock including asphalt, shale, limestone, metallic ores including some iron ores, gold ores, nickel ores, rock salt, potash, talc, calcspar, fluorspar, gypsum, borax, sandstone, and the like The type of material suitable for excavation is dependent on the strength and fabric of the material and the precise nature ofthe cutting pick or drag tool

An apparatus of the invention is typically attached to a vehicle such as an excavator, bulldozer, tractor or the like

The apparatus of the invention may include a drive motor to dπve each cutting wheel or cutting and breaking wheel The drive motor may be independently powered or may be powered from the vehicle The drive motor may comprise a fluid motor such as an hydraulic or pneumatic motor, and can also include an electric motor, diesel motor, petrol motor and the like It is preferred that the drive motor is an hydraulic drive motor powered by the vehicle Each cutting wheel or cutting and breaking wheel is typically coupled to a drive shaft (integrally or non integrally) The drive motor may be directly or indirectly attached to the shaft to rotate the shaft and therefore the cutting wheel or the cutting and breaking wheel

The cutting wheel or the cutting and breaking wheel may be coupled to or integral with the lower end or working end of a shaft The wheel may extend through a plane substantially perpendicular to the longitudinal axis of the shaft The cutting wheel or the cutting and breaking wheel may be provided with cutting tools such as peripheral teeth or picks which can be formed from hard material such as tungsten-carbide The teeth or picks may be adjustable and/or replaceable The cutting and breaking wheel and/oi coupled shaft includes breaking means, typically a bursting wheel or wedge Typically the wheel or wedge are on one or both faces of the cutting wheel. Typically the support means supports the cutting wheels or the cutting and breaking wheels to enable them to engage the solid material at a desired position or angle Typically the support means includes two shafts the lower end or working end of each shaft being coupled to or integral with a cutting wheel or the cutting and breaking wheel to form a cutting assembly, and a support frame assembly The support frame assembly supports the cutting assemblies to allow the cutting wheels or the cutting and breaking wheels to engage the solid material at a desired position or angle The support frame assembly may include an upper attachment area to support an upper part of a said cutting assembly, and a lower attachment area to support a lower

in part ofthe cutting assembly. The lower part may support the cutting assembly for movement in two dimensions and in a preferred form this can be achieved by a ball and socket arrangement.

The upper attachment area preferably allows movement in one dimension only.

The arrangement means may be capable of: (a) passively arranging the cutting wheel or cutting and breaking wheels relative to each other whereby reaction forces from excavating (e.g. forming at least one groove) in the solid material result in a required net force on the support frame assembly (i.e. it may be adjustable prior to commencing cutting wheel or cutting and breaking the solid material); or (b) actively arranging the cutting wheel or cutting and breaking wheels relative to each other whereby reaction forces from excavating (e.g forming at least one groove) in the solid material result in a required net force on the support frame assembly (i.e. it may actively arrange or dynamically arrange the cutting wheel or cutting and breaking wheels during the cutting wheel or cutting and breaking of the solid material). Generally the arrangement means is capable of (b). The arrangement means may comprise a passive or an active linkage arrangement, typically an active parallelogram linkage arrangement. The linkage arrangement may form part of the support frame assembly and is used to adjust, typically actively, the position of the cutting assemblies and more particularly the positions of the two cutting wheels or the cutting and breaking wheels relative to each other whereby reaction forces from excavating (e.g. forming at least one groove) in the solid material result in a required net force on the support means. The linkage arrangement may include a forward link member mounted more towards the vehicle and a rear link member mounted behind the forward link member. The link members are preferably rotatable about a vertical axis and about a position mid-way between the ends of each link member Both link members may extend in the same plane. A cutting assembly comprising a rotatable shaft and a cutting wheel coupled to one end thereof, or a cutting and breaking assembly comprising a rotatable shaft and a cutting and breaking wheel coupled to one end thereof, may be attached to both the forward and the rear link member, and these link members may comprise the upper attachment area as described above. Pivoting movement of the link members causes the cutting assemblies to be moved relative to each other such that one cutting assembly can adopt a leading or preferential cutting position relative to the other cutting assembly Advantageously the rotatable shafts are parallel to one another and remain parallel to one another during and after the pivoting movement of the link members. Advantageously, the distance between two parallel planes perpendicular to the rotatable shafts and passing through each of the wheels varies in a way which keeps the vertical

separation of the wheel in planes parallel to the surface being excavated constant and substantially zero even during orientation of one wheel relative to another, lt is to keep the distance between the planes passing through the centres of the cutting wheels and parallel to the ground (ie. at an angle 'alpha' to the plane of the cutting wheels) that the parallelogram movement has been devised. Typically, the arrangement means forms part of the support frame assembly and is an parallelogram linkage arrangement which is capable of adjusting the positions of the two wheels relative to each other whereby reaction forces from excavating in the solid material result in a required net force on the support means and an excavator is coupled to the support means and the linkage arrangement via an excavator arm whereby in use in cutting an excavation with the two wheels the net force on the excavator arm is adjustable via the linkage arrangement so as to permit an operator to steer the apparatus in the required direction and to cut the required excavation in the solid material. Alternatively, the arrangement means forms part of the support frame assembly and is an parallelogram linkage arrangement which is capable of adjusting the positions of the two wheels relative to each other whereby reaction forces from excavating in the solid material result in a required net force on the support means and an excavator is coupled to the support means via an excavator arm and coupled to the linkage arrangement whereby in use in cutting an excavation with the two wheels the net force on the excavator arm is adjustable via the linkage arrangement so as to permit an operator to steer the apparatus in the required direction and to cut the required excavation in the solid material.

Additionally, the linkage allows the wheels, whilst parallel to one another, to adjust the distance between the planes defined by the wheels so as to keep the distance of the centres of the wheels from the ground surface a constant.

Advantageously the two wheels are parallel to one another and remain parallel to one another during and after the pivoting movement of the link members. One or more actuators may be used to pivot the link members, and the actuators may comprise rams. The linkage is adjusted by the operator to arrange the wheels relative to each other whereby the position of one of the wheels is at a trailing position relative to the other wheel In use the linkage is adjusted so that the wheel at the trailing position is arranged so that its path at least partially intersects the path taken by the other wheel so that the excavation cut by the wheel in the trailing position at least partially intersects the excavation cut by the other wheel, ln addition, the linkage is adjusted as required by the operator so that the depth of the excavation cut by the wheel in the trailing

position is substantially the same as or different from the depth of the excavation cut by the other wheel.

Typically the two wheels are rotated in opposite directions such that the torque reaction force of one is at least partially cancelled by the other during the excavating to result in a required force on the support means Alternatively, the two wheels may be rotated in opposite directions such that the torque reaction force of one is substantially cancelled by the other during the excavating whereby the net resultant force from the wheels on the support means is substantially zero

Advantageously the two wheels are rotated in opposite directions and the positions of the wheels are adjusted relative to one another such that the force of one is at least partially cancelled by the other during the excavating to result in a required force on the support means The required net force may be that required by an operator of machinery which is attached to the support means (e.g. an excavator) to drive and/or steer and/or control the apparatus for excavating solid material through the solid material in the required direction, or drive and/or steer and/or control the machinery as the apparatus for excavating solid material cuts and/or breaks the solid material

The two wheels may be rotated in opposite directions and the positions of the wheels adjusted relative to one another such that the force of one is substantially cancelled by the other during the excavating whereby the net resultant force from the wheels on the support means is substantially zero Typically the two wheels are rotated at substantially the same speeds (but in opposite directions), although they may be rotated at different speeds and in opposite directions, if desired

Each of the wheels can be thrust into the solid material such as rock with a force from zero in soft material up to a force that does not stall the motors driving the cutting wheels Typically the wheels are thrust into the solid material such as rock at a force in the range 500- 25,0001b, more typically 1 ,000- 1 ,0001b and even more typically 4,000- 12,000 lb, and yet even more typically 8,000 lb or 4 tonnes This implies a cutting force of about 2 5 tonnes which in turn requires a torque for each wheel of about 5,000 Nm if each wheel is about 400 mm in diameter Larger wheels will require larger forces and larger torques and vice versa By making a cutting and breaking wheel free of picks in the vicinity of the means to break the material, all the thrust and torque is available to push the means to break the material into the excavation (e.g. groove) to break under-cut material away

Examples of suitable wheels for use in this invention include

(A) A cutting wheel for excavating a solid material, the wheel comprising means to cut the material.

(B) A cutting wheel for excavating a solid material, the wheel comprising (a) means to cut the material, and

(b) means to allow excavation of an undercut in the solid material

(C) A cutting wheel for excavating a solid material, the wheel comprising

(a) means to cut the material,

(b) means to allow excavation of an undercut in the solid material comprising means to allow escape of excavated material from the solid material and from the wheel during excavation of the solid material, and

(D) A cutting and breaking wheel for excavating a solid material, the wheel comprising (i) a cutting wheel having

(a) means to cut the material, and (b) means to allow excavation of an undercut in the solid material, and

(ii) means to break the material being operatively associated with the cutting wheel, said means to break the material being disposed so as to enter into an undercut and break the material only after the undercut has been cut by the means to cut the material

(E) A cutting and breaking wheel for excavating a solid material, the wheel comprising (i) a cutting wheel having

(a) means to cut the material,

(b) means to allow excavation of an undercut in the solid material comprising means to allow escape of excavated material from the solid material and from the wheel during excavation of the solid material, and (ii) means to break the material being operatively associated with the cutting wheel, said means to break the material being disposed so as to enter into an undercut and break the material only after the undercut has been cut by the means to cut the material

(F) A cutting and breaking wheel for excavating a solid material, the wheel comprising (i) a cutting wheel having

(a) means to cut the material,

(b) means to allow excavation of an undercut in the solid material comprising means to allow escape of excavated material from the solid material and from the wheel during excavation ofthe solid material; and (ii) means to break the material being operatively associated with the cutting wheel, said means to break the material being disposed so as to enter into an undercut and break the material only after the undercut has been cut by the means to cut the material

(G) A cutting and breaking wheel for excavating a solid material, the wheel comprising

(i) a cutting wheel having a central portion and a plurality of arms extending outwardly and upwardly from and about the periphery of the central portion

(ii) means to break the material being located on at least one of said arms, said means to break the material being disposed so as to enter into an undercut and break the material only after the undercut has been cut by means to cut the material, the means to cut the material being attached to the ends of the other of said arms, and (iv) means to allow excavation of an undercut in the solid material

(H) A cutting and breaking wheel for excavating a solid material, the wheel comprising

(i) a cutting wheel having a central portion and a plurality of arms extending outwardly and upwardly from and about the periphery of the central portion

(ii) means to break the material being located on at least one of said arms, said means to break the material being disposed so as to enter into an undercut and break the material only after the undercut has been cut by means to cut the material, the means to cut the material being attached to the ends of the other of said arms, and

(iii) means to allow excavation of an undercut in the solid material comprising means to allow escape of excavated material from the solid material and from the wheel during excavation of the solid material

(I) A cutting and breaking wheel for excavating a solid material. the wheel comprising (i) a cutting wheel having a central portion and a plurality of arms extending outwardly and upwardly from and about the periphery of the central portion

(ii) means to break the material being located on at least one of said arms, said means to break the material being disposed so as to enter into an undercut and break the material only after the

undercut has been cut by means to cut the material, the means to cut the material being attached to the ends ofthe other of said arms;

(iii) means to allow excavation of an undercut in the solid material comprising means to allow escape of excavated material from the solid material and from the wheel during excavation of the solid material

A method of excavating a solid material may comprise: cutting and breaking the solid material with one of the above wheels (A) to (I).

The wheel may be in the form of a disc, drum, barrel, cylinder, annulus, or roller, for example. Typically at least a portion of the wheel adjacent and including the peripheral edge of the wheel is curved or angled upwardly through an angle equal to the angle between the drive shaft and the normal to the surface of the solid material being excavated, so as to allow excavation of an undercut in the solid material effectively parallel to the surface of the solid material.

Typically the means to cut the material are located at and attached to the peripheral edge of the wheel. Typically the means to cut the material comprises a plurality of cutting teeth or cutting picks (alternatively called drag tools), typically 2-25, more typically 3- 15, even more typically 5-10) spaced substantially evenly (or unevenly) or uniformly spaced but in orientations determined by a lacing pattern around a portion of the periphery of the cutting wheel One particular form ofthe cutting wheel comprises nine slots and ten uniformly spaced drag tools and an unoccupied portion ofthe periphery adjacent the bursting wheel.

Typically the means to allow excavation of an undercut in the solid material comprises means to allow escape of excavated material which comprises one or more slots (typically 2- 1 , more typically 4-8, even more typically 5-7, and even more typically 6 or 9 slots) in the wheel Typically the slots are apertures through the wheel disposed about the peripheral edge of the wheel or there are one or more slots that form part ofthe peripheral edge of the wheel Typically each slot is located between the means to cut the material such as between adjacent cutting picks (typically forming a spoke-like wheel). The slots are large enough to substantially allow escape of at least some if not substantially all of the excavated material from the solid material and from the wheel during excavation of the solid material Not all the drag tools on each cuttin» wheel need necessarily be at the same radius.

ir. The means to break the material may comprise at least one wedge or bursting wheel. The wedge(s) or bursting wheel(s) may be located on the top surface or the bottom surface of the wheel or on both the top and bottom surfaces Alternatively the wedge(s) or bursting wheel(s) may be coupled (integrally or non integrally) to a rotatable shaft member which is also coupled to the wheel. Generally the wedge(s) or bursting wheel(s) is spaced inwardly from the cutting picks and more typically is spaced inwardly from the peripheral edge of the wheel so as to break the material only after it has been undercut by the means to cut the material Thus the wheel can initially cut the excavation (e.g groove) and when the excavation (e.g groove) is at a predetermined depth (corresponding to the spacing between the periphery of the wheel and the wedge or bursting wheel), the wedge or bursting wheel will enter into the cut excavation (e.g groove) and will cause the solid to be broken The wedge or bursting wheel may be located on the flat portion of the wheel or on the curved or angled portion of the wheel When the wedge or bursting wheel is on the angled portion of the wheel the curved or angled portion is lengthened to accommodate the wedge or bursting wheel When the wedge or bursting wheel is located on the curved or angled portion the wear on the cutting and breaking wheel, in use, will be typically less than when it is on the flat portion of the wheel, and/or the wheel may break a greater thickness of rock

If desired, the wedge or bursting wheel may be rotatably mounted relative to the wheel In this manner, the wedge or bursting wheel may be rotatably inserted into a cut excavation (e g groove) which may minimise wear

The wedge or bursting wheel may be adjustably mounted with respect to the wheel to allow it to extend from the wheel at a plurality of distances This may be of advantage should the hardness of the solid material vary according to cutting depth It may also allow the wheel to enter deeply into the cut excavation (e g groove) with subsequent expansion of the wedge or bursting wheel to cause the rock to break

The wedge or bursting wheel may be spaced inwardly from the peripheral edge of the wheel by varying distances depending on the type of rock to be cut and the cutting action, power capability of the apparatus and the like For instance, with soft friable solid, the wedge or bursting wheel can be spaced more towards the peripheral edge and can have a higher raised profile For strong friable rock, the wedge or bursting wheel can be spaced closer to the centre of the wheel to improve its leverage For strong non-friable rock, the wedge or bursting wheel height may be reduced

It is preferred that the cutting and breaking wheel is provided with a pair of wedges or bursting wheels which are connected to an attachment member, the attachment member being mountable in an aperture in the wheel The attachment member may threadingly engage with the opening in the wheel. In one particular form of the cutting and breaking wheel, a first wedge or part of the bursting wheel extends from the top surface of the wheel, and a second wedge or part of the bursting wheel extends from the bottom surface of the wheel. The first and second wedges of the bursting wheel may be coupled together (integrally or non-integrally) with a coupling shaft or shafts which passes through an aperture in the cutting and breaking wheel Typically, the first and second wedges of the bursting wheel are releasably mounted relative to each other, and to the cutting and breaking wheel If the wedge or bursting wheel is rotatably mounted with respect to the cutting and breaking wheel, it is preferred that the wedge or bursting wheel profile is symmetrical about its rotation axis Typically when the first and second wedges of the bursting wheel are releasably mounted relative to each other, and to the cutting and breaking wheel there is slop or clearance between the coupling shaft or shafts and the aperture in the cutting and breaking wheel to allow dirt and grit which may enter the aperture to leave but without allowing larger particles to get in. Typically the slop or clearance is 0 5-5mm, more typically 0.75 - 3mm, even more typically 0.8 - 2mm, yet even more typically 0 9- 1 5mm and even more typically about 1mm Alternatively, the first and second wedges of the bursting wheel or bursting wheel assembly may be fitted with bearings and seals so as to prevent the entry of dirt and grit into the aperture

Various types of profiles for the wedge or bursting wheel may be employed and may include, for example, in the case of a wedge - a simple wedge shape, or in the case of the wedge or bursting wheel a cone shape or a "pyramid" shape or a "mushroom" shape The angle of inclination of the leading face of the shape and the height of the profile (i e., the distance that the wedge or bursting wheel can be raised above the wheel) may also vary Typically the angle of inclination of the inclined face is between I to 1 degrees, more typically 2 to 10 degrees and even more typically 3 to 8 degrees The profile of the wedge or bursting wheel surface may vary and may depend on the type of solid to be cut and the type of cutting action If a pair of wedges or bursting wheels are provided, each wedge or bursting wheel may have an identical or a different profile relative to the other. In one form, the wedges of the bursting wheels may have identical profiles (such as mushroom shapes) while in another form, one wedge of the bursting

I S wheel may be substantially planar while the other wedge or bursting wheel may have a mushroom shape, or a conical shape or a pyramidal shape, for example Typically, the top surface ofthe bursting wheel is a mushroom shape and the bottom surface a cone shape designed to roll easily on the floor of the excavation Typically the cutting wheel is coupled (integrally or non integrally) to or adjacent to one end of a rotatable shaft member, the shaft member being rotatably drivable by a drive means (e g a motor) The drive means may be hydraulic, pneumatic, electric or internal combustion Suitably, the drive means is coupled to a reduction gearbox to provide the rotatable shaft member with a lower rotating speed but high torque A biasing means may be coupled to the rotatable shaft member to bias the rotatable shaft member, and therefore the wheel against and away from the solid material to be cut Typically the biasing means provides sufficient force to the wheel to allow it to cut into the solid, but allows the shaft member to kick back should the wedge become jammed or stuck within the solid Typically the shaft, drive means, gearbox, any linkage, and biasing means are supported by a support frame assembly which is attachable to a vehicle (e.g an excavator) The biasing means may be hydraulic, pneumatic or mechanical Suitably, the supporting framework is pivotally mounted and the biasing means can function to bias the supporting framework and therefore the rotatable shaft member towards and away from the solid to be cut Ground engageable stabilisers to restrict sideways movement of the vehicle may be included The periphery of the cutting wheel/disc may be slightly thicker (e l %-35%, more typically 5%-15%) relative to the remaining body of the wheel/disc Alternatively, the central portion of the cutting wheel/disc may be thicker (e g l %-35%, more typically 5%- 1 %) relative to the periphery of the cutting wheel/disc One or more cutting teeth may be provided and these may be mounted adjacent the periphery of the wheel (but not in the slots) Preferably, a plurality of cutting teeth are provided The teeth may be equally spaced about the periphery of the disc but it is preferred that cutting teeth are not present in the immediate vicinity of the wedge or bursting wheel The cutting teeth may be at various angles and it is preferred that some of the cutting teeth extend upwardly from the wheel, some of the cutting teeth are in line with the wheel and some of the cutting teeth are spaced downwardly from the wheel This can ensure that the cut excavation (e.g groove) is sufficiently large to accommodate the wheel without the wheel itself becoming wedged in the excavation (e g groove)

BRIEF DESCRIPTION OF DRAWINGS

An embodiment of the invention will be described with reference to the following drawings in which

Figure 1 is a perspective view of a cutting and breaking wheel coupled to a rotatable shaft;

Figure 2 is a side view of a cutting and breaking wheel coupled to a rotatable shaft of Fig. 1 ;

Figure 3 is an isometric view of an apparatus according to an embodiment of the invention, Figure 4 is a view of the support frame assembly, attachment means and part of the adjustment means ofthe apparatus illustrated in Figure 3;

Figures 5A-5D show top, rear, side and isometric views of the apparatus having the two cutting or cutting and breaking assemblies in line with each other;

Figures 6A-6D show top, rear, side and isometric views of the apparatus of Figure 3, where the cutting or cutting and breaking assemblies are in an extreme leading and trailing configurations. The assemblies may be at any intermediate positions between the extremes as well as at the extremes;

Figure 7 shows a cutting or cutting and breaking wheel shaft cylinder link assembly;

Figure 8 shows a rear views of the apparatus having the two cutting or cutting and breaking assemblies in line with each other the cutting and breaking wheels attached to the apparatus being of the type depicted in Figs I and 2,

Figure 9 is a side view of the cutting and breaking wheel coupled to a rotatable shaft of Fig. 1 excavating an undercut;

Figure 10 is a schematic depiction of two cutting and breaking wheels excavating solid material;

Figure 1 1 is a schematic side view depiction o the apparatus having the two cutting or cutting and breaking assemblies attached to an excavator arm excavating solid material,

Figure 12 is a side view of part of an alternative cutting and breaking wheel coupled to a rotatable shaft to that of Fig. 1 ;

Figs. 13(a) and 13(b) depict a parallelogram linkage which couples, supports and arranges two cutting wheels or two cutting and breaking wheels.

Figs. 13(c) to 13(i) depict alternative parallelogram linkages which couple, support and arrange two cutting wheels or two cutting and breaking wheels; and Figure 14 is a perspective view of a cutting and breaking wheel coupled to a rotatable shaft;

Figure 15 is a side view of a cutting and breaking wheel coupled to a rotatable shaft of Fig. 14 where the wheel of Figure 14 has been rotated through - 180° (arms 607 and 608 of Figure 14 are not depicted); Figure 16(a) schematically depicts a side view of a wheel of the type shown in Figures 1 and 2 cutting an excavation; and

Figure 16(b) schematically depicts a side view of a wheel of the type shown in Figures 14 and 15 cutting an excavation

BEST MODE AND OTHER MODES FOR CARRYING OUT THE INVENTION

Referring to Figure 1 , there is illustrated a cutting and breaking wheel 300 to which is fitted a bursting wheel assembly 301 . Wheel 300 has a top surface 302 and a bottom surface 303. Top surface 302 is curved upwardly adjacent the peripheral edge 3 10 of wheel 300 at 304, 305, 306, 307, 308 and 309 to allow excavation of an undercut in the solid material. Wheel 300 typically comprises a strong, tough steel and has a wear resistant steel layer welded by electric arc on its surfaces 302 and 303. Bursting wheel assembly 301 typically comprises case hardened steel.

Attached to peripheral edge 3 10 are a plurality of cutting picks or drag tools 3 1 1, 3 12, 313, 314 and 3 15. Picks or drag tools 3 1 1 -3 1 may be conventional insert picks, in which a tungsten carbide tool tip is inserted into an axial hole in the steel main body of the pick and are used for gauge cutting Drag tools 3 1 1 -3 1 may be any type of conventional, or unconventional drag tool. Tools 3 1 1 -3 1 may or may not be fitted with means to allow rotation. Tools 3 1 1 -3 15 may or may not be provided with dust suppression or working or assisting water jets. Tools 3 1 1 - 315 may be arranged with any type of conventional or unconventional lacing pattern in which the tools are oriented so as to excavate the undercut Preferably whatever lacing pattern is used will ensure that the excavation (e.g groove) which is cut has sharp stress-concentrating corners,

making for easy breaking Picks 3 I 1 -3 15 are arranged such that at least one of the picks extends above top surface 302 (e.g pick 3 12), at least one of the picks extends below bottom surface

303 (e.g. pick 315) and at least one of the picks are in line (e g picks 3 13. 14 and 31 1 ) or are in intermediate positions It is also noted that picks may be absent at the peripheral edge 310 immediately adjacent bursting wheel assembly 301 so as to allow that portion of the cutting wheel having the bursting wheel to be pushed further into a cut slot/groove Wheel 300 is mounted onto a rotatable shaft 3 16 which itself can be rotated by a drive means Wheel 300 has slots 317, 3 18, 3 19, 320, 321 and 322 which allow escape of excavated material from solid material and from wheel 300 during excavation of the solid material Bursting wheel assembly 301 is formed from a pair of bursting wheel components being upper bursting wheel component 301 a and lower bursting wheel component 301 b, shown exploded with reference to Figure 2 Bursting wheel assembly 301 is rotatable as a single unit such that bursting wheel components 301 a and 301 b are able to rotate independently of wheel 300 Bursting wheel component 301 a has a "mushroom" profile which is a consequence of the mushroom shape of its upper surface 322 Bursting wheel component 301 b has a "pyramid" profile which is formed when the pyramid shaped bottom portion 324 of bursting wheel component 301 a is inserted through aperture 325 of wheel component 301b Prior to or during insertion O ring clip 326 is located over O ring clip retaining portion 327 of wheel component 301a to fit bursting wheel components 301 a and 301 b together In this arrangement, bursting wheel components 301 a and 301 b are free to rotate relative to each other Bursting wheel components 301 a and 301 b are fitted to an attachment portion 328 which is in the form of a annulus having an external thread The annulus fits within a corresponding threaded opening within bursting wheel 300 and this results in attachment portion 328 being securely threadingly engaged with bursting wheel 301 via threaded portion 329 There is typically about a 0 9- 4mm, more typically 0 75 - 1 5mm, even more typically about I mm clearance between the various parts to allow dirt which may enter the arrangement to leave but without allowing larger particles to get in The parts are easily assembled but requires a sledgehammer to take bursting wheels 301 a and 301 b apart

Each wheel 300 is supported, rotated, and mounted by an assembly, an embodiment of which is illustrated in Figure 3

Referring to Figure 3 there is illustrated an apparatus 10 which can be attached to an excavator arm, for example, and which can be used for cutting through ground material such as

rock and the like. Apparatus 10 has two spaced apart cutting assemblies 1 1 , 12 which shall be described in greater detail below. Cutting assemblies 1 1 , 12 respectively comprise a rotatable shaft 13, 14, the bottom of each shaft coupled to and supporting a cutting or cutting and breaking wheel 15, 16 respectively (note wheels 1 and 16 are depicted as showing the effective cutting width rather than showing details of the wheels per se).

A support frame assembly (better shown in Figure 4) supports the two cutting assemblies 1 1, 12 in the desired position which is spaced apart with shafts 13, 14 being generally parallel with respect to each other.

To each cutting assembly 1 1 , 12 is coupled an upper hydraulic drive motor 17, 18 respectively, each motor being of a type known in the art and which is powered by hydraulic fluid from the vehicle to which it is coupled For the purposes of clarity, the vehicle and the hydraulic hoses have been omitted The drive motors 17, I S drive shafts 1 , 14 which in turn rotate the cutting wheels 1 , 16 Assemblies 1 1 , 12 may be fitted or coupled to an excavator via an excavator arm by attaching plate 23 of Fig 4 to the excavator arm via appropriate "ears" in place of a bucket of an excavator and power is to be taken from the hvdraulic pumps of the excavator, rather than from a power take-off (though a power take off could be used to drive a hydraulic pump if appropriate, or indeed an external separate pump and drive motor could be used). A direct drive motor may be used i.e no gearbox being used Choice of drive motor type (petrol, diesel, electric pneumatic etc.) and type of drive (direct or via a gearbox) and gearbox type and ratio are engineering decisions depending on the precise application of a realisation of this technology. Choice of final speed depends on circumstance, but will generally be such as will give a drag tool a speed through solid rock of 2 or 3 m/sec (though speeds of 0 25 to 5 m/s may be used). A typical operating speed of a cutting wheel operates 70-90rpιn, more typically about 78rpm. The angle at which shafts 13, 14 (and therefore wheels 1 5 and 16) extends below the drive assembly can be varied The angle of each of shafts 13, 14 to the vertical is typically the same and is typically between 3° to 45°, more typically 5° to 30°, even more typically 10° to 27°, and yet even more typically about 25°

Referring to Figure 4, there is shown in greater detail the support frame assembly 19 Support frame assembly 19 comprises a main mounting structure 20 formed from box steel To the bottom of main mounting structure 20 is an extending end plate 21 which extends under a socket arrangement 22 which shall be described in greater detail below On an upper part of

main mounting structure 20 is provided an attachment means 23 to attach the entire apparatus to an excavator arm, but it should be appreciated that the type of attachment means can of course vary depending on to what type of vehicle the apparatus is attached Forward of attachment means 23 is an extending plate 24 which is strengthened by gussets 25, 26 to prevent sag At the front end of extending plates 24 is a pivot connection 27 to pivotally couple a rear link member

28 to plate 24. The rear link member shall be described in greater detail below Intermediate the ends of extending plate 24 is a central support assembly 29 which depends from and is pivotally attached to plate 24 Central support assembly supports a forward link member 30 adjacent its upper end, and supports the socket arrangement 22 adjacent its lower end Forward link member 30 and rear link member 28 form an upper attachment area to which an upper part of each cutting assembly 1 1 , 12 can be attached The socket arrangement 22 forms a lower attachment area to which a lower portion of each cutting assembly 1 1 , 12 can be attached.

As illustrated in the various drawings but particularly in Figures 3 and 4, it can be seen that the lower portion of each cutting assembly has a ball 1 , 32 each ball locating within a respective socket 33, 34 to form a ball and socket connection It can be seen that in this manner the cutting assembly can freely swivel in its socket Each socket is of a split ring configuration which can be seen in Figure 4 to allow the respective ball to be removed therefrom If desired, seals or lubricants can be positioned within the sockets 33, 34 The upper end of each cutting assembly 1 1 , 12 is attached to forward and rear link members 28, 30 via a cylinder link assembly as illustrated in Figure 7 Cylinder link assembly 35 comprises a hollow tube 36 through which a respective rotatable shaft member ( 13 or 14) can extend with motor at the top and ball joint at the bottom Fixed to the outside of tube 36 is a flat plate 37 which extends in a diametrically opposed manner from tube 36 Plate 37 has openings 38, 39 the openings functioning to accommodate pivot pins to pivotally couple plate 37 to one end of forward and rear link members 28, 30 (see Figures 3 and 4) A mirror image of assembly 35 is located on the other end of forward and rear link members 28, 30 to attach the other cutting assembly 12 to the support frame assembly Note that plate 37 is obliquely mounted

Link members 28, 30 are moved by an actuator in the form of two hvdraulic rams 40, 4 1 only one of which is illustrated in Figure 3 but both of which are illustrated in Figures 5A and 6A Each hvdraulic ram is pivotally attached at one end to main mounting structure, and a spacing lug 42 is provided on each side of structure 20 to correctly position the respective ram

The other end of each ram is pivotally connected to an arm 43, the arm being rigidly attached to the respective cylinder link assembly 35 (see Figure 7) Thus, each ram acts on the respective cylinder link assembly (one link assembly for each cutting assembly), which in turn causes the forward and rear-link members 28, 30 to pivot about their respective vertical axis, at the same time rotating arrangement 22 (of Fig. 4) and moving balls 3 1 , 32 within sockets 33, 34. The affect of this is to change the positions cutting assemblies 1 1 , 12 with respect to each other to cause one of the cutting assemblies to adopt a leading position and the other one to adopt a trailing position. Shafts 13, 14 which are substantially parallel to one another before changing the positions of cutting assemblies 1 1 , 12, with respect to each other, remain substantially parallel to one another after changing the positions of cutting assemblies 1 1 , 12 due to the way in which the respective cylinder link assemblies 35 are changed The changes in the positions of cutting assemblies 1 1 , 12, may be viewed as corresponding to distorting a parallelogram linkage, to which cutting assemblies 1 1 , 12, are respectively coupled to opposite sides of the parallelogram in such a way that shafts 13, 14 are substantially parallel to one another, to form another parallelogram in the same plane such that shafts 1 , 14 remain substantially parallel to one another. The ball and socket arrangement facilitates movement of cutting assemblies 1 1 , 12 relative to each other. By appropriately adjusting the positions of cutting assemblies I 1 , 12 in cutting an excavation in the solid material a required net force on support frame assembly 19 results. An excavator is coupled to plate 23 via an excavator arm and coupled to the linkage arrangement comprising link members 28, 30 which are moved by two hydraulic rams 40, 41 whereby in use in cutting an excavation with the two wheels 15 and 16 the net force on the excavator arm via plate 23 is adjustable by appropriately adjusting link members 28, 30 and thus the relative positions of wheels 1 and 16 to each other in the solid material so as to permit an operator to steer the apparatus 10 in the required direction and to cut the required excavation in the solid material.

Figures 5A-5D show the apparatus with cutting assemblies 1 1 , 12 in alignment, that is neither of cutting assemblies 1 1 or 12 lead or trail. This arrangement would be suitable when cutting through uniform rock when no steering action is needed Whether the rock is weak (not soft) or strong (not hard) is substantially irrelevant Figures 6A-6D show the arrangement where cutting assembly 1 1 is now the leading cutting assembly and cutting assembly 12 is the trailing cutting assembly, ln this configuration, cutting assembly 1 1 presents its cutting wheel forward of the cutting wheel of cutting assembly

12. The arrangement of Figures 6A-6D is provided and maintained by operation of the two hydraulic rams 40, 41 and this can be controlled by a driver in the cabin That is, by extension or retraction of rams 40, 41 , the cutting assemblies can adopt a leading/trailing position relative to each other, or an aligned position as illustrated in Figures 5A-5D Relative to the central pivot axis of the apparatus (fig 4-7) the lower ball joints both move in an arc, defined by the distance of the ball from the central pivot axis However, the outer tubes containing the drive shaft do not rotate with the rotation of the socket arrangement (22) but rather slide within the socket (33, 34) as the socket rotates so that relative to the main frame they do not rotate Motion in an arc without rotation is achieved by a parallelogram linkage of which the struts 28 and 30 foπn two sides ( the other side being the plate 37 of figure 7 pivoting about holes 39-38)

Since movement in an arc without rotation has been defined by the comparatively light structure of struts 28 and 30 of figure 4 and the plates 37 of figure 7, the parallelogram does not need to be repeated at the bottom end of the link 36 of figure 7 This joint may be constaicted massively so as to take all forces other than the comparatively small forces required to orient this link 36 of Figure 7 through the parallelogram linkage

The apparatus 10 according to the invention typically uses two cutting or cutting and breaking wheels, such as for example, the two cutting and breaking wheels 300 and 300a (similar to that described in Figs 1 and 2 or similar to that described in Figs 14 and 1 ) illustrated in Figure 8 (mounted so as to counter rotate to one another), the orientation of the shafts 316 and 316a of which is at an angle α to the normal to the rock face, α being closer to normal to the rock face being excavated than it is to parallel to it The two wheels 300, 300a are counter rotated relative to each other This allows the torque reaction from one wheel 300 to be at least in part cancelled by that from the other wheel 300a and substantially cancelled providing that both wheels 300 and 300a are thrust equally into the same material Each wheel 300, 300a is typically trust into the solid material (e g rock depending on the type of rock) with a force of about 8,000 lb or 4 tonnes This implies a cutting force of about 2 5 tonnes which in turn requires a torque of about 5,000 Nm if each bursting wheel is about 400 mm in diameter Larger wheels will require larger forces and larger torques By making each of the wheels free of picks in the vicinity of the bursting wheel, all the thrusl and torque is available to push the bursting wheel into the groove to break the under-cut material away

Cutting-and-breaking wheel angle, α, depth of undercut, etc.

Each cutting or cutting and breaking wheel undercuts rock, the rock between the cutting wheel or cutting and breaking wheel and the free face of the rock being broken by the bursting wheel. The centre of the cutting wheel or cutting and breaking wheel is translated so that it follows a path parallel to the free face of the rock For convenience in describing the geometry ofthe situation, it will be assumed that the free face is plane, though this need not, in practice, be the case, and indeed there are occasions when it is advantageous that the surface be not plane For convenience in describing the geometry, it will be assumed that the cutting wheel or cutting and breaking wheel is progressing in a straight line, though it may in practice follow a curve, ln this simplified geometry therefore the axle of the cutting wheel or cutting and breaking wheel lies in a plane which is normal to the surface of the rock and includes the direction of motion of the centre of the cutting wheel or cutting and breaking wheel The following discussion refers to only one wheel but comments are equally applicable to both wheels. Referring to Fig 9 the shaft 57 coupled to the cutting and breaking wheel 50 is inclined forward, so that there is an angle, , to the vertical, the plane of the cutting and breaking wheel therefore being at an angle 51 , α to the horizontal

It will be appreciated that the projection of the trajectory of any particular tool tip 54 in a plane normal to the rock surface 65 and perpendicular to the direction of motion of the centre of the cutting and breaking wheel will be an ellipse, the eccentricity of which is greater the smaller the angle α

Only a portion of this ellipse will be present as an undercut 53 beneath the plane of the rock surface, since the breaking action of wheel 50 removes rock progressively as each wheel 50 advances. In the plane described, perpendicular to the direction of translation of the centre of the cutting and breaking wheel 50 and normal to the rock surface, the undercut 53 has that the general appearance of a "happy smile" Since the specific energy (energy per unit volume excavated) of the breaking action of the cutting and breaking process is very small, whilst the specific energy of the cutting process is very high, it is desirable to minimise the volume cut whilst maximising the volume broken.

Let δ represent the maximum perpendicular distance between the plane surface of the rock and the upper surface ("top lip") of the "happy smile", when the cut-and-break cutting and breaking wheel 50 is operating at its maximum depth at which the cutting and breaking action will occur. Experiment and analysis agree that, provided the rock properties are the same at all

scales, then δ will be proportional to the diameter of the cutting and breaking wheel Let d represent a generalised maximum depth of excavation, d being typically somewhere between about 1/3 and 2/3 of the diameter of the cutting and breaking wheel 50 when the cutting and breaking wheel 50 is operating in comparatively weak or jointed rock 52 (jointed rock 52 will break along the joints rather then in the way described for massive rock), it being understood that a wheel of larger diameter would operate at a larger value of d It is evidently desirable to design the excavation machine so as to maximise the broken volume, and, this implies finding a suitable balance between α and d, since the effect of increasing α is to increase d but at the same time reduce the cross sectional area broken for a given d Experiment has indicated that a value of α in the vicinity of 25 degrees may be close to optimum in the rock so far subjected to experiment Typically α lies in the range of 0 to 45 degrees, more typically 5 to 45 degrees, or more typically in the range of 1 5 to 35 degrees, more typically 20 to 30 degrees and even more typically 25 degrees

The cutting and breaking wheel 50 has the appearance of a dish or saucer, the outer portions 66 being bent up at an angle α in relation to the plane of the central part of the cutting and breaking wheel 67 (Because of the clearance excavated by the gauge tools 54, the angle need not in practice be exactly α, though the angles are generally substantially the same)

In Fig 9, which is drawn for the plane in the direction of motion of the centre of the cutting and breaking wheel 50 and including the axis of rotation of the cutting and breaking wheel 50, the quantity d is shown, together with other quantities I, w, x, y and t Of these, I, the depth undercut, will for a given geometry be proportional to the diameter of the cutting and breaking wheel 50 that is, d and I will behave similarly as the diameter of the cutting and breaking wheel is varied It has been found that a value of I in the vicinity of 1 /6 the diameter of the cutting and breaking wheel 50 is appropriate, though values of up about 1/3 may be possible It is desirable to make I as large as possible, since a larger I will make the undercut material more easily broken, and imply an increase in d There are however geometrical constraints which limit the length that be used for I, the distance from the bend in the wheel 50 to the tool tips 54 In particular, it is important cutting and breaking wheel 50 does not nib against the excavation, and so clearance is excavated, represented by x and y in the sketch In the case of 465 mm cutting and breaking wheel designed to operate in Helidon Sandstone, x and y were both about 10 mm It would be anticipated that x and y would increase proportional to the diameter of the cutting and breaking wheel 50 The longer I, the larger x and y should be. which implies that if there is a

2K minimum to t, (which is, in the case of a 465 mm diameter wheel designed to operate in Helidon

Sandstone, about 30 mm) which, since the material of the wheel 50 needs to be sufficiently strong to support the tools 54, there is, in turn implies that a large 1 will require an increase in w, which is typically about 1/10 of the diameter of the cutting and breaking wheel 50, being, in the case of a 465 mm cutting and breaking wheel 50 designed to excavate Helidon sandstone, about 50 mm. Now the increase in w demands an increase in the volume of the rock cut rather than broken, which is an effect in the opposite direction to that desired The choice of the values of t, w, I, and α is therefore one demanding engineering judgement on the part of the designer, it being quite possible that there is no one optimum, but rather that the optimum exists differently for each strength of material such as rock and rock fabric Dimensions x and y, the clearances above and below the cutting wheel (Figure 9) need not be the same in fact there is advantage in making x rather large (e g 15 mm) and y rather small (e g 3 mm)

Principle of spoke design

Each drag tool 54 produces fragments of cut material, and these have to be removed from the excavation by being swept aside by the passing tools and their mountings The tools and their mounting boxes project a portion of the distance 1, the remainder of I being the raised portion of the cutting and breaking wheel 50 itself At large advances-per-turn of the cutting and breaking wheel 50, which experiment has shown to be desirable since these correspond to low specific energies of the overall excavation process, and also correspond to high productivity from the excavation machine, the volume of cuttings may be larger than can easily be accommodated between the tools 54 and their mountings 55 In this case and referring momentarily to Fig 1 it is desirable to increase the available volume, by mounting the tools 3 1 1 -

315 on what approximate to spokes (see spokes 330-335 in Fig 1 ), so providing an increase in available space for enabling cuttings and so providing means to allow escape of excavated cut material from the solid material and from the wheel 300 during excavation ofthe solid material

It is desirable to maximise both the length and the slenderness of the spokes 330-335, whilst maintaining sufficient strength in the spokes 330-335 to allow the appropriate forces to be applied to the tools 3 1 1 -3 15 Choosing the appropriate dimensions for the spokes 330-335, is thus a matter of engineering judgement, it being unlikely that there is any particular optimum, but rather that the optimum may depend on the strength and fabric of the material such as rock to be excavated. It is in practice possible to mount the tools on "spokes" which place the tool tips as much as 1/4 of the diameter of the cutting and breaking wheel from the roots of the

"spokes. In the case of a 465 mm diameter cutting and breaking wheel designed to excavate Helidon Sandstone the tool tips were about 120 mm from the roots ofthe "spokes".

Required net force

Cut-and-break rock cutting wheel or cutting and breaking wheels are of necessity operated with a substantial torque, so as to apply a suitable load to the drag tools and so cause them to penetrate the rock which has to be cut. The cutting force applied to a drag tool can be several tens of kilo-Newtons, in the case of a 465 mm cutting wheel or cutting and breaking wheel designed to excavate Helidon Sandstone, a resultant of up to 30.000N has been designed for, and a cutting wheel or cutting and breaking wheel may have several tools engaged at one time, but only along a part of the circumference of the cutting wheel or cutting and breaking wheel. In the process of rock cutting there therefore arises a force which may conveniently be called the "torque reaction" and which acts in a direction perpendicular to the thrust force which is used to push the drag tools against the rock face to be cut So large are torque reaction forces that rock cutting machinery fitted with a single cutting head is of massive construction and great stability. A single cutting head fitted to an excavator can only possibly be stable if the axis of rotation of the cutting head is parallel to the surface to be excavated and perpendicular to the plane containing the boom and the stick of the excavator This is the orientation used by Mitsui- Miike, for their twin-header machine which, for reasons of symmetry, is in fact fitted with two cutting heads. This orientation of the axis of rotation is inappropriate for cut-and-break excavation, in which the axis of rotation of the cutting wheel or cutting and breaking wheels is at an angle α to the surface being excavated, α being typically 25 degrees. It follows that a single cut-and-break cutting wheel or cutting and breaking wheel would not be suitable for fitting to a machine such as an excavator.

It is appropriate to fit two cutting wheel or cutting and breaking wheels which counter- rotate, since in this arrangement the torque-reactions would be expected substantially to cancel (there being sufficient stability available from the excavator to ensure that limited out-of-balance torque reactions would not be a problem). Rock is however so variable a material that it is quite possible for the two wheels to be in sufficiently different conditions for the cancelling not to occur, in which case the path followed by the cutting wheel or cutting and breaking wheels through the rock would not be in the direction of the applied force (towards the slew axis of the excavator) but rather at an oblique angle to that direction. This following of an oblique path is not generally desirable, (though on particular occasions it may be desirable, if, for example, an

excavation is required alongside a vertical wall, so that the excavator cannot get into a position where the desired cutting direction is actually towards the excavator) If there is an asymmetry between the torque reaction of two cutting wheel or cutting and breaking wheels, that asymmetry may be eliminated by introducing an opposite asymmetry, and this may in practice be achieved by moving the cutting wheel or cutting and breaking wheel with the larger reaction into a position behind and partially to the side of that with the smaller With the two cutting wheel or cutting and breaking wheels operating at substantially the same rotational speed and depth this movement will have the efTect of reducing the torque reaction from the trailing wheel, since its path now partially intersects the excavation made by the other wheel It is thus possible to adjust the torque reaction from cutting wheel or cutting and breaking wheels that are in different rock strengths sufficiently close to zero to allow the cutting wheel or cutting and breaking wheels to be drawn towards the slew axis of the excavator rather than the path of the excavation move uncontrollably to one side of the intended path lt is not anticipated that the movement will in practice be frequently required, though it will be a valuable feature of the equipment when it is required

It may occasionally be necessary to steer the cutting wheel or cutting and breaking wheels so that they follow a path which is not directly towards the slew axis of the excavator under these conditions, it may be appropriate that the two torque reactions be deliberately arranged to be significantly out-of-balance, so as to allow the tools to follow a path other than directly towards the slew axis of the excavator It would be anticipated that the steering action would involve a combination of steering by the cutting-and-breaking wheels combined with operation of the slew mechanism of the excavator Using this ability to steer the cutting may be an uncommon occurrence, but invaluable when required

Principle of parallelogram It is evidently necessary that cut-and-break cutting wheel or cutting and breaking wheels should be operated with the drive shaft at the angle α discussed above It is also desirable that they should operate at the same, depth, d, which should be close to the maximum possible in that particular rock The discussion of the preceding paragraph also indicated that it is desirable that it be possible to move one cutting wheel or cutting and breaking wheel relative to the other, so as to adopt a path behind and to one side of the leading wheel, in a position where the path of the trailing cutting wheel or cutting and breaking wheel partially intersects the path of the leading one This can be achieved by partial rotation of the centres of the two cutting wheel or

cutting and breaking wheels in a plane parallel to the general rock surface about an axis which lies at some point on a perpendicular bisector of the line joining the centres of the two cutting wheel or cutting and breaking wheels. This rotation must however preserve both the orientation of the axes of rotation of the cut-and-break wheels and the depth of cut. This is most easily achieved if the axes of rotation of the axles in which the cut-and-break wheels are mounted are constrained by appropriate mountings to lie within parallel planes perpendicular to the general rock surface, and a linkage constmcted which is, in a plane parallel to the general rock surface, a parallelogram, distortion of the parallelogram giving the required rotation of the cutting wheel or cutting and breaking wheel centres about a point lying on a perpendicular bisector of the line joining the centres of the cutting wheel or cutting and breaking wheels, the orientation in space of the axes of rotation of the cutting wheel or cutting and breaking wheels being preserved during the distortion, as also is the depth of cut

The geometry of the parallelogram linkage may be realised in practice through a combination of ball joints and light rods The passive or active distortion of a parallelogram linkage may be accomplished in numerous different ways. Active distortion methods include fitting a ram or extending screw device between diagonally opposite corners of the parallelogram, or fitting a ram between a fixed point and a corner or side of the parallelogram. Another alternative is to use a motor and a sector plate, the sector being fixed to one of the sides of the parallelogram, the motor to an adjacent side

In use the two cutting wheel or cutting and breaking wheels are not typically thrust equally into the same material, either deliberately or as a consequence of the practical difficulty of doing so. As a consequence, there will be an out-of-balance force, tending to rotate the excavator about the slew axis. In the apparatus according to the invention, this out-of-balance force may be controlled, and be enhanced or diminished as the operator requires, by using a parallelogram linkage controlled by the operator. As is shown in Figs. 3-8, the parallelogram linkage allows the direction of the cutting wheel or cutting and breaking wheel shaft to be held constant while the disposition of the cutting wheel or cutting and breaking wheel may be changed, so that one is partially behind the other. Figs 13(a) and 13(b) illustrate, in schematic form, a parallelogram linkage which couples, supports and arranges two cutting wheels or two cutting and breaking wheels 500 and 501 which are coupled respectively to one end as shown of rotatable shafts 502 and 503 Shafts 502 and 503 are linked by linkages 504 and 505 as depicted

in Figs. 13(a) and (b). Parallelogram A is formed by linkages 504, 505, 506 and 507, as depicted in Fig. 13(a). Linkage 506 is joined rigidly to linkage 1 I by rotatable linkage structure 508

(comprising a rotatable tube to which linkages 506 and 5 1 1 are rigidly fixed and through which tube passes a support rod 590) which may rotate about its axis. Consider the situation when the entire apparatus is being translated in the +ve y direction. To arrange wheels 501 and 500 relative to one another so that wheel 500 trails wheel 501 , parallelogram A is distorted by movement at joints located where the linkages are joined to one another which allow movement about pins with their axes in the z direction so as to allow movement only in an x - y plane in the x-y plane by rotation of structure 508 in direction 509 to form another parallelogram in the x-y plane, designated parallelogram B in Fig 13(b) Formation of parallelogram B causes wheel 500 and coupled shaft 502 to move in the direction of arrow 510 as depicted in Fig 13(a) so as to trail wheel 501 as depicted in Fig. 13(b). The leading cutting wheel or cutting and breaking wheel will experience more resistance to its motion than the one following it, and so there will be a larger torque reaction from the leading wheel than the one behind it Tt is possible for the operator to choose at will which wheel is the lead wheel, and which is the following wheel, and so he can choose the direction of the unbalanced force created on the excavator about the slew axis. Since the operator can choose the extent of the shadowing of one wheel behind the other (up to a maximum dictated by the size of the components and the geometry of the structure), the operator can not only choose the direction of the force tending to slew the excavator, he can within limits, control its magnitude also This facility allows the operator either to compensate for differences in the material through which the two wheels are progressing, so as to eliminate the out-of-balance forces tending to slew the excavator, or alternatively to allow the out-of- balance forces actually to assist in the deliberate slewing of the excavator as a cut is made, thus steering the cutting direction Figure 13 (c) illustrates the conceptual basis of the invention. This requires that two cutting wheels or cutting and breaking wheels 500 and 50 ] be arranged so that each of their axis of rotation is oblique to the surface to be excavated (the x - y plane), yet that at least one of wheels 500 and 501 should be movable so as to enable it to be shadowed behind the other This requires movement of each point of one shaft 502 or 503 and cutting wheel 501 or 500 relative to the other along similar arcs which are in planes substantially parallel to the surface to be excavated, (the x -y plane). This is most simply achieved by locating one cutting wheel 500 or 501 and shaft assembly 502 or 503 relative to the other by a framework consisting of a minimum

of three linkage rods, hinged so as to allow movement only in a plane parallel to the surface to be excavated, the x - y plane ln figure 13(c) any three of the rods 504, 506, 51 1 and 514, hinged so as the be able to move only in an x - y plane will suffice to locate the two cutting wheels 500 and 501 and drive shafts 502 and 503 appropriately. In figure 13 (c) the structure is clearly one of two parallelograms, one above the other, 504, 505. 506 and 507 being above 514, 517, 51 1, and 513. This basic stmcture can be simplified by the omission of any one of the rods 504, 506, 51 1 or 514, provided that the simplified structure includes a rigid connection to ensure that the structure moves in the same way that it would were the fourth rod present. In figure 13 (a), for example, this rigid connection is provided by tube 508 rigidly joining rods 506 and 51 1. In this realisation of the invention, wheels 501 and 500 can be moved relative to one another so that wheel 500 trails wheel 501 , parallelogram A is distorted by movement at joints located where the linkages are joined to one another which allow movement about pins with their axes in the z direction so as to allow movement only in an x - y plane in the x-y plane by distortion of parallelogram A to form another parallelogram B in the x-y plane Formation of parallelogram B causes wheel 500 and coupled shaft 502 to move in the direction of arrow so as to trail wheel 501 (not shown but see Fig. 13(b) which illustrates the change in positions of wheels 500 and 501 relative to one another). From a geometrical point of view any of the alternative linkages shown as figures 1 (d), 13 (e), 1 (f) or 1 (g) would be equally effective in controlling the motion of one cutting wheel relative to another, the choice between these (or any similar ones geometrically equivalent) being one of convenience bearing in mind the function of the machine

Referring now to figure (4) as well as to figure 13 (a) and 13 (c) Part 30 is the equivalent of rod 506, part 28 corresponds to rod 504, socket arrangement 22 corresponds to rod 51 1 , and these three rods suffice to ensure that the cutting wheels and the drive shafts may only move relative one to the other through an arc of length that of any of the rods 504, 506 or 51 1 . Staicture 506, 508, 51 I ( corresponding in figure 4 to 22,29,30,33 and 34) is attached to structures 505 and 507 (these are tubular structures containing the drive shafts to the cutting wheels, items 1 1 and 12 of figures 3 and 4) by means of ball joints

In figure 13 (c) 512, 5 1 , 516 and 19 are pins passing through and linking the corners ofthe top and bottom parallelograms A and A'. These pins 12, 5 1 5, 16 and 519 are drawn as single pins, though each pin could equally well be two short pins, one in each of the upper and lower parallelograms.

Alternative and equally effective arrangements of parallelograms are illustrated in figures

13 (d), 13 (e), 13(f) and 13 (g) In figure 13 (d) the top parallelogram A has been extended (as compared to parallelogram A in Fig 13(a), for example), with extensions to linkages 505 and

507, namely linkages 521 and 520, and with a linkage 522 similar to 504 now displaced parallel to its former position (as depicted in Fig 13(a) as 504 In figure 13 (e) rigid link 508 of Fig

13(d) has been replaced by long pins, 523 and 524 ln figure 13 (f) two parallelograms, an upper one, designated parallelogram A, formed of linkages 529, 53 1 , 528, 530 together with extensions 535 536 which are linked to shafts 507 and 502, is linked by long pins, 537, 534, 533 and 532 to a lower parallelogram designated parallelogram A', formed by linkages 527, 525, 51 1 and 526 Figs 13(a) and 13(b) illustrate, in schematic form, a parallelogram linkage which couples, supports and arranges two cutting wheels or two cutting and breaking wheels 500 and 501 which are coupled respectively to one end as shown of rotatable shafts 502 and 503 In Fig 13(g) shafts 502 and 503 are linked by linkages 544 and 5 1 1 as depicted Parallelogram A is formed by linkages 551 1 ,54 1 , 542 and 540, as depicted in Fig 13(g) Linkage 544 is joined rigidly to linkage 542 by rotatable linkage structure 543 (comprising a rotatable tube to which linkages 542 and 544 are rigidly fixed and through which tube passes a support rod 591 ) which may rotate about its axis Consider the situation when the entire apparatus is being translated in the +ve y direction To arrange wheels 501 and 500 relative to one another so that wheel 500 trails wheel 501, parallelogram A is distorted by movement at joints located where the linkages are joined to one another which allow movement about pins with their axes in the z direction so as to allow movement only in an x - y plane in the x-y plane by rotation of structure 543 in direction 509 to form another parallelogram in the x-y plane, designated parallelogram B (not shown) Formation of parallelogram B causes wheel 500 and coupled shaft 502 to move in the direction of arrow 510 as depicted in Fig 13(a) so as to trail wheel 501 Figure 13 (h) illustrates schematically how the rigid component 506, 508, 5 1 1 of Fig

13(d) is supported The central tube, 508, is supported by a rigid bar, 508 (a), which passes through it, and which is permanently fixed at the top to the support stmcture which forms a frame, 561 , 562, and 560 This is also shown in figure 4, where parts 24,25,26,23, correspond to 561, 20 corresponds to 562, and 21 to 560 Part 508(a)of figure 13 (h) is invisible in figure 4, but is in fact, present inside the tube, 29 Figure 13 (h) also illustrates one of a number of alternative possible means of adjusting the shape of parallelogram A In figure 13 (h) is

illustrated a ram, 565, which by extending or contracting would rotate the rigid structure 506,

508, 51 1 (corresponding to stmcture 30, 29, 34, 32 of figure 4) about the rigid bar 508 (a)

Figure 13 (i) illustrates schematically the means which may be used to change the shape of parallelogram A (which is depicted in more detail in Figs 3-7 Two rams 572, 575, and attachments 573, 574, 570, 571 , connect corners of parallelogram A to the support stmcture 562. In figure 3 one of the rams is visible, 40, the other invisible behind the rest of the apparatus. As is shown in figures 5 (b), (c) and (d), but most clearly in 5(c), the ram actually connects not to the parallelogram itself, but to the structures I 1 and 12 and at a point below the plane of the top parallelogram It will be apparent from Figs 1 (a)- 13(i) that the apparatus has a steering capability It is possible for a skilled operator to make the cutting wheel or cutting and breaking wheel follow a straight path which does not pass through the slew axis of the excavator, and so the machine may be used to cut a straight edge alongside itself, as may be required if, for example, a rectangular foundation is to be excavated for the basement of a building This special geometry allows the use of the apparatus which is proven to be significantly more efficient than the conventional cutting head designs conventionally used for rock cutting

Provision is made for partial or complete electronic control and automation of the rock cutting system of cutting machine and excavator, in that the apparatus can be fitted with transducers which report some or all of the following data - 1 Pressure across the drive motor or motors,

2 Rate of rotation of the cutting wheel or cutting and breaking wheels,

3. Angular orientation of the parallelogram linkage of the cutting machine,

4 Angular orientation of the cutting machine relative to the stick, boom, and chassis of the excavator This electronic control may comprise limited control of the motion of the excavator stick so as to ensure that the speed of motion is such as will keep the cutting wheel or cutting and breaking wheels operating efficiently, or complete operation of the cutting process under computer control, or any alternative between these extremes

Fig 9 depicts a single cutting and breaking wheel 50 but the following description is equally applicable the simultaneous use of two cutting and breaking wheels ln order to excavate the undercut 53 each cutting and breaking wheel 50, which is driven by inclined shaft 57, at

angle α, 51 , advances to the right in figure 9 The rate of rotation of the cutting wheel or cutting and breaking wheel 50 is determined by the properties of the tips of the drag tools and the available power With conventional tungsten carbide tipped tools, the rate of rotation is such as will give to the tool tips a speed relative to the rock across which they are being driven in the range of 0 1 to 5 metres per second, more typically 0 5 to 3 5 metres pre second, even more typically 1 to 3 metres pre second, a speed of 2 metres per second being typical It is necessary to lace the cutting tools, of which two of several fitted to the wheel are illustrated, 54, 62, the tools being arranged so that they do not all follow the same path, some being angled up 62, some being in the middle 54 and some pointing down not shown Appropriate lacing is a skill known to practitioners of the art of mechanical rock excavation The tools, which are replaceably mounted in tool holders 55, 56, are held in place by clips (not shown) so that they may easily be replaced when they are worn The tool holders 55, 56 and others not shown suffer wear in use, and are replaced by cutting and welding replacements as is necessary, a jig being provided for the purpose Substantial slots are left 63 between the tools to provide space for the cuttings excavated by the tools to fall into as they are cut By making the bursting wheel free of picks in the vicinity of the wedge, all the thrust and torque is available to push the wedge into the groove to break the under-cut material away However, it may be that this introduces undesirable vibration in which case tools may be fitted all around the wheel 50 The cuttings are removed from the undercut and deposited in the spoil area 63 by the cutting wheel or cutting and breaking wheel as it rotates and advances Eventually, as the cutting wheel or cutting and breaking wheel advances, the rotatable bursting wheel assembly 58, 59, 60 and 61 will be carried into the undercut Here upper, mushroom shaped surface of the bursting wheel will press against the underside of the undercut 52, the lower surface of the cone of the bursting wheel resting on the lower surface of the undercut, the two parts, which fit with some slack in the retaining ring 58 which is screwed into the bursting wheel 50, being wedged together into the undercut 53 The slack between the components of the bursting wheel, which is typically between 0 75 and 4 mm, serves two purposes It allows grit, which may be between the parts o the bursting wheel, to fall free as the bursting wheel cone 59 hangs from the mushroom 61 held by the spring clip 60, to fall free as the bursting wheel passes behind the undercut Secondly, the slack ensures that when the bursting wheel is jammed into the undercut, the flat mating surfaces of the mushroom 61 and the cone 59 transfer the forces need to break the rock 52 dii ectly from the lower to the upper surface of the undercut without applying significant forces to the wheel through excessive contact with the retaining ring 58 The bursting wheel 61 may become worn with use, the spring

clip 60 being chosen so as to allow disassembly of the bursting wheel and replacement of components as necessary. It is anticipated that a variety of different profiles will be required for the mushroom 61 depending on the strength, fabric, and friability of the rock being excavated

In Fig. 10 is shown two cut-and-break cutting and breaking wheels 76, 77 being used to excavate a trench 78, the cutting and breaking wheels having undercut rock, 79, the cuttings emerging in the gaps 73 between the tools 72 The cutting and breaking wheels are progressing in the direction of the arrow 80 The cutting and breaking wheels are driven by shafts, 74 It is appropriate for the cutting and breaking wheels to counter-rotate so that the torque reaction forces they apply to the machine to which they are both attached tend to cancel The rotations shown have the advantage that large fragments of material broken free tend to be carried between the two shafts and be dumped behind the machine The alternative rotation may have advantage if the rock breaks into fragments too large conveniently to pass between the shafts If the opposite rotation is used, the excavated lumps will tend to be dumped beside the excavation Note that the direction in which the tools 72 are fitted depends on the intended rotation It will be seen that cutting and breaking wheel 76 is trailing cutting and breaking wheel 77 in this illustrated example, though the two wheels could be side-by-side, or wheel 76 could alternatively be in advance of wheel 77 depending on the arrangement of the wheels In the position illustrated, wheel 77 is excavating the rock equivalent to the full diameter of the wheel, whilst wheel 76 excavates only a fraction of its diameter Under these circumstances, in homogeneous rock, the torque reactions are unlikely to cancel completely, there being a net force in the direction shown by the arrow 75 This arrangement may be particularly appropriate if the machine supporting the cutting and breaking wheels is able only to provide a force in a direction oblique to the intended path of the cutting and breaking wheels, 8 1 say In this case, the out of balance torque reaction force 75 will with the available thrust force 80 give a resultant in the direction 8 1 , thus allowing the cutting and breaking wheels to be steered along a path not exactly parallel to the thrust force from the machine supporting the cutting and breaking wheels This could be particularly useful were the shaded area 82 to be inaccessible to the machine driving and propelling the cutting and breaking wheels, so limiting the machine to providing a force in the direction 81 The disposition of the cutting-and-breaking wheels illustrated might also be appropriate even when the machine supporting the cutting and breaking wheels is able to provide a thmst force in the required direction of progress of the cutting and breaking wheels, 80, but however the two cutting and breaking wheels happen to be in rock which differs in properties,

S that being excavated by wheel 76 being stronger than that being excavated by wheel 77 In this case, the reduction in the quantity of rock being excavated by wheel 76 in comparison with that excavated by wheel 77 allows the torque reactions between the two cutting and breaking wheels to brought to almost complete or complete cancellation, and so the cutting and breaking wheels 5 will proceed in the direction of the thrust force, 80, even though one wheel is in stronger rock than the other

In an alternative bursting wheel 89, shown in Fig 12, the upper mushroomed shaped portion 90 of the bursting wheel 89 is partially or completely recessed in the thickness of the cutting and breaking wheel, 94 which is coupled to rotatable shaft 98 The lower pyramid

10 shaped portion 91 of the bursting wheel 89 is not similarly recessed, since the cutting and breaking wheel, advancing into the rock at the angle α (see 92) has removed the rock Spring 93 is included in spring holding cavities 99 and 100 located in portions 90 and 91 respectively Interconnected hydraulic fluid channels 95, 95a and 95b are included in shaft 98, wheel 94, and bursting wheel 89 as depicted in Fig 12 Bursting wheel 89 may be expanded such that portions

15 90 and 91 expand above the general profile of wheel 94 to break the under-cut material Bursting wheel 89 is then subsequently retracted Expansion is achieved by, for example, by admitting high-pressure water into channel 95, and thence to channels 95a and 95b to force portions 90 and 91 apart against spring 93 which is attached to cavities 99 and 100 Contraction is achieved by, for example, by releasing the pressure applied to the water in channel 95, and

20 thence to channels 95a and 95b so that the tension is expanded spring 93 forces portions 90 and 91 together as depicted which is attached to cavities 99 and 100 lf high-pressure water is used, it may also be passed through flushing nozzles 101 and 102 (and other flushing nozzles around the periphery of wheel 94 not depicted) to provide the dual effect of flushing away debris and exerting an extra large force on the under-cut material Alternatively, rotating shaft 98 may be

25 hollow and a space may be provided with a phasing valve to be used with a high-pressure water supply so as only to supply water whilst the tools are in the immediate vicinity of the rock to be cut or in contact with the rock, or it may be available at all times Typically phased high pressure water is provided via channels 95, 95a and 95b to the bursting wheel 89 only when the bursting wheel 89 is in an undercut, to hydraulically separate portions 90 and 1 of a bursting wheel so as

30 break the undercut rock The provision of water may increase the efficiency of picks 95, as it leaks out from between the spacings bursting wheel 89 and wheel 94. by cooling them as well as suppressing airborne dust Alternative configurations include (a) Bursting wheel fitted with seals

to prevent dust or dirt entering, (b) As for (a) but with appropriate ball or roller bearings to grease at; (c) Operated by high pressure water which leaks out subsequently, (d) Operated by hydraulic oil (or oil mix as is used in underground mining machines) and returns to tank, so seals etc. are used. Water may be used as (a) Dust suppressing agent, using jets, (b) As a cooling agent, using jets, (c) As a means of assisting the cutting action of the tools, aiming high pressure water jets close to the tool tips

Fig 1 1 depicts an articulated excavator arm which comprises three parts, and has three movements, limited normally to a single plane The part of the articulated arm closest to the excavator itself is called the boom, 2 in Fig 1 1 , the associated movements being up and down The boom is jointed to the stick, 5 in Fig 1 1 , which moves in and out Articulated to the end of the stick is the bucket, and its movements are curl, when the bucket moves towards the excavator, and uncurl, when it moves the other way Filling an excavator bucket starts with the stick out, the boom down, and the bucket partially curled In this position the bucket teeth are correctly oriented to dig into the ground To fill the bucket, the operator is required to bring the bucket towards the excavator whilst maintaining the bucket at the correct orientation for the bucker to fill, and at a constant depth below the surface This is accomplished by '

• Initially uncurling the bucket as it approaches the excavator, the stick coming closer the angle of the stick becoming larger Later, when the bucket is very close, the operator will curl it so as to fill the bucket completely • Bringing the stick in towards the excavator

• Initially raising the boom, as the stick approaches the vertical, then lowering it again as the stick passes the vertical in its approach towards the excavator

The excavator operator is used to this sequence of operations, to the point where a skilled operator performs this sequence of operations without any substantial conscious thought To set up to make a cut with a cut-and-break apparatus, the excavator operator unhitches the bucket and replaces it with the cut-and-break apparatus, 1 in Fig 1 I connecting the appropriate hydraulic hoses and any electronic transducers associated with the cut-and-break apparatus 10 (see for example Figs 3-6 for more details of apparatus 10) The operator then lifts the apparatus 10 clear of the ground, and verifies that the two cutting and breaking wheels were both at the same distance from the operator, that is, neither wheel is advanced in front of the other The operator will then start the oil flow to the hvdraulic motors, which will begin to turn the cutting and breaking wheels Lowering the boom, sending the stick out, and curling the

cut-and-break apparatus 10 slightly will result in the cutting and breaking wheels being poised just above the ground level, at an angle rather greater than , in a position where operating the curl will simultaneously decrease the angle of the drive shafts to α and bury the cutting and breaking wheels beneath the surface at the appropriate depth, d 10 in Fig 1 1 below the surface, 1 1 in Fig. 1 1. Thereafter, as with the bucket, the operator, 3 in Fig 1 I , will initially raise then lower the boom 2 in Fig. 1 1 by means of the rams 1 in Fig 1 1 as the stick passes through vertical, bring the stick 5 in Fig I 1 by means of the ram 4 in Fig I 1 in, and uncurl the cut-and- break apparatus 10 by means of the ram 6 in Fig I I and the linkage 7 in Fig 1 1 as it approaches the excavator, leaving a trail of debris 9 in the process, in Fig 1 I Since the cut-and-break apparatus 10 operates at its best when loaded so as to be almost in a stalled state, since this maximises the load on the tools, and corresponds to maximum penetration of the tools, it will be necessary to monitor the speed of the approach of the apparatus 10 to keep it as fast as is possible without stalling the cutting and breaking wheels This part of the operation of the cut- and-break apparatus 10 may well be best under electronic control limiting the speed of the stick movement

Under normal operation of the excavator, if excavating a trench, a second cut would be taken immediately below the newly exposed rock surface, 8 in Fig. I I , or, if excavating a surface, the excavator would be moved sideways by the width of the cut, and another cut would be taken. ln the event that the two cutting and breaking wheels were in dissimilar material, the operator would become aware of the tendency of the cutting and breaking wheels to move sideways, and the resulting tendency of the excavator to slew Under these conditions, the operator would bring into the lead the cutting and breaking wheel which required an increase in torque-reaction compared with the other, and would continue to cut with the cutting and breaking wheels thus disposed, the rearward cutting and breaking wheel operating so as at least partially to intersect the excavation made by the leading wheel

In the event that the cut-and-break apparatus 10 has to follow a path not directly toward the excavator, the operator would initially use the slew mechanism of the excavator to encourage the cut-and-break apparatus 10 to follow the desired path If the slew was insufficient to achieve this steering, then the cutting and breaking wheel which produced the torque reaction in the desired direction would be put into the lead position, thus producing as additional force to steer the cut-and-break wheels in the desired direction

After a number of cuts in sequence, the excavation site will have become littered with rock fragments: the operator would remove the cut-and-break apparatus 10, and replace it with the bucket, for cleaning the surface, subsequently re-fitting the cut-and-break apparatus 10 should further excavation be required Referring to Figure 14, there is illustrated an alternative cutting and breaking wheel 600 to which is fitted a bursting wheel assembly 601 . Wheel 600 has a top surface 602 and a bottom surface 603. Top surface 602 has arms 604, 605, 606, 607, 608 and 609 extending therefrom which are curved (or alternatively angled) upwardly therefrom to allow excavation of an undercut in the solid material. Wheel 600 typically comprises a strong, tough steel and has a wear resistant steel layer welded by electric arc on its surfaces 602 and 603. Bursting wheel assembly 601 typically comprises case hardened steel

Attached respectively to the end of each of arms 604, 605, 606. 607 and 608 is a cutting pick or drag tool 61 1 , 612, 613, 614 and 615. Picks or drag tools 61 1 -6 1 5 may be conventional insert picks, in which a tungsten carbide tool tip is inserted into an axial hole in the steel main body of the pick and are used for gauge cutting Drag tools 61 1 -61 5 may be any type of conventional, or unconventional drag tool. Tools 61 1 - 1 may or may not be fitted with means to allow rotation. Tools 61 1 -61 may or may not be provided with dust suppression or working or assisting water jets. Tools 61 1 -615 may be arranged with any type of conventional or unconventional lacing pattern in which the tools are oriented so as to excavate the undercut. Preferably whatever lacing pattern is used will ensure that the excavation (e g. groove) which is cut has sharp stress-concentrating coi ners, making for easy breaking Picks 61 1 -61 5 are arranged such that at least one of the picks extends above the surface of its corresponding arm (e.g. pick 612 extends above the upper surface of arm 604), at least one of the picks extends below its corresponding arm (e.g. pick 615 extends below the lower surface of arm 607) and at least one of the picks are in line with their corresponding arms (e picks 613, 614 and 61 1 ). It is also noted that picks are absent at the peripheral edge 610 adjacent bursting wheel assembly 601 so as to allow that portion of the cutting wheel having the bursting wheel to be pushed further into a cut slot/groove. Wheel 600 is mounted onto a rotatable shaft 616 which itself can be rotated by a drive means. Wheel 600 has slots 617, 618, 619, 620, 321 and 622 which allow escape of excavated material from solid material and from wheel 600 during excavation of the solid material.

Bursting wheel assembly 601 is formed from a pair of bursting wheel components being upper bursting wheel component 601 a and lower bursting wheel component 601 b, shown exploded with reference to Figure 15. Bursting wheel assembly 601 is rotatable as a single unit such that bursting wheel components 601 a and 601 b are able to rotate independently of wheel

5 600. Bursting wheel component 601 a has a "mushroom" profile which is a consequence of the mushroom shape of its upper surface 622 Bursting wheel component 601 b has a "pyramid" profile which is formed when the pyramid shaped bottom ponion 624 of bursting wheel component 601 a is inserted through aperture 625 of wheel component 601 b Prior to or during insertion O ring clip 626 is located over O ring clip retaining portion 627 of wheel component

10 601 a to fit bursting wheel components 601 a and 601 b together ln this arrangement, bursting wheel components 601 a and 601 b are free to rotate relative to each other Bursting wheel components 601 a and 601 b are fitted to an attachment portion 628 which is in the form of a annulus having an external thread The annulus fits within a corresponding threaded opening within bursting wheel 600 and this results in attachment portion 628 being securely threadingly

15 engaged with bursting wheel 601 via threaded portion 629 There is typically about a 0 9- 4mm, more typically 0.75 - 1 .5mm, even more typically about l mm clearance between the various parts to allow dirt which may enter the arrangement to leave but without allowing larger particles to get in The parts are easily assembled but requires a sledgehammer to take bursting wheels 601 a and 601 b apart.

20 Each wheel 600 is typically supported, rotated, and mounted by an assembly, as shown for wheel 300 of Figures 1 and 2 in Figures 3- 13i Figure 16(a) schematically shows an undercut excavation being made by a wheel 300 (as per wheel 300 of Figs I and 2) and Figure 16(b) schematically shows an undercut excavation being made by a wheel 600 (as per wheel 600 of Figs. 14 and 1 5) As is apparent from a comparison of Figures 16(a) and 16(b) that because

25 bursting wheel 601 is located on curved or angled arm 609 on wheel 600, bursting wheel 601 is able to fit more easily under overhang 700 as shown in Figure 16(b) than bursting wheel 301 which is located on flat surface 302 of wheel 300, is able to fit under overhang 800 as shown in Figure 16(a) This enables wheel 600 to break off at least a portion of overhang 700 easily and with less wear on cutting and breaking wheel 600 than on wheel 300

30 It should be appreciated that various other changes and modifications may be made to the embodiment described without departing from the spirit and scope of the invention