Patent Description:
A variety of different types of excavation machines have been developed for cutting drifts, tunnels, subterranean roadways and the like in which a rotatable head is mounted on an arm that is in turn movably mounted at a main frame so as to create a desired tunnel cross sectional profile. <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT> all described apparatus for mill cutting of rock and minerals in which a rotating cutting head forced into contact with the rock face as supported by a movable arm. In particular, <CIT> describes the cutting end of the machine in which the rotatable heads are capable of being raised and lowered vertically and deflecting in the lateral sideways direction by a small angle in an attempt to try enhance the cutting action.

<CIT> describes a machine for digging roadways tunnels and the like in which a plurality of cutting heads are movable to dig into the rock face via a pivoting arcuate cutting path. <CIT> describes a rock excavator having a cutter head mounting a plurality of annular disc cutters suitable to operate in an undercutting mode.

However, conventional cutting machines are not optimised to cut hard rock having a strength typically beyond <NUM> MPa whilst creating a tunnel or subterranean cavity safely and reliably of desired cross sectional configuration. <CIT> and <CIT> both describe a type of machine that addresses some of these problems, however the inventors have determined that the cutters used on those machines are not as well optimised for the cutting apparatus as they could be.

<CIT> discloses a cutter in the form of a disc having buttons on its periphery for mining of rock material by means of undercutting.

<CIT> discloses a cutter in the form of a disc having buttons on its periphery. The cutter is for use with a tunnel boring machine.

A further issue with known cutting machines is that the cutters experience large forces during a cutting operation. Typically, disc cutters are mounted on a shaft, and the shaft (and hence disc) is supported for rotation by bearings. The bearings are typically roller bearings. Cutters of this type include buttons to abrade rock. The buttons protrude radially outwards from an edge of the disc. The inventors have determined that the shape of the buttons used in the cutters can significantly affect the lifetime and design of the bearings used to facilitate rotation of the cutter. For example, the inventors have determined that cutters having conical buttons transmit a component of cutting force (often referred to as the "side force") to the bearings that pushes and pulls on the bearing in an alternating fashion during a cutting operation. It is the relatively high frequency of change of direction of the side force transmitted to the bearings that shortens the life of the bearings. Accordingly it is desirable to eliminate or minimise the frequency with which the side force transmitted to the bearings changes direction. In particular, it is desirable to eliminate or minimise the side force being transmitted in the pulling (negative) direction, that is, the direction of pulling the cutter disc away from the bearings, since it is force in this direction that is most damaging to the bearings.

The inventors have also determined that other geometrical aspects of the cutter can also affect the cutting performance of the cutting apparatus.

It is an objective of the present invention to provide cutting apparatus suitable to form tunnels and subterranean roadways being specifically configured to cut hard rock, say beyond <NUM> MPa, in a controlled and reliable manner, that is, apparatus capable of mine development work. It is a further objective to provide a cutting apparatus capable of creating a tunnel with a variable cross sectional area within a maximum and a minimum cutting range. It is a further objective to provide cutting (excavator) apparatus operable in an 'undercutting' mode according to a two stage cutting action. It is a further objective to provide a cutter that has an optimised cutting geometry for the cutting apparatus. It is a further objective to provide a cutter that reduces the occurrence of pulling side forces. It is a further object to provide a cutter that has an optimised geometry for balancing cutter strength and reducing cutter wear.

At least some of the objectives are achieved by providing cutting apparatus having a plurality of cutting assemblies, each including a rotatably mounted cutting head that is attached to a support structure by a mounting assembly. Each mounting assembly is arranged to enable its respective cutting head to be pivoted in an upward and downward direction and a lateral side-to-side direction, with respect to the support structure. In particular, each mounting assembly comprises a support pivotally mounted to the support structure and carrying an arm via a respective additional pivot mounting such that each cutting head is capable of pivoting about two pivoting axes. The desired range of movement of each head is provided as the dual pivoting axes are aligned transverse (including perpendicular) to one another and are spaced apart in the longitudinal direction of the apparatus between a forward and rearward end.

Advantageously, the cutting heads comprise a plurality of disc-like roller cutters distributed circumferentially around a perimeter of each head so as to create a groove or channel into the rock face as the heads are driven about their respective rotational axes. The heads may then be raised vertically so as to overcome the relatively low tensile strength of the overhanging rock to provide breakage via force and energy that is appreciably lower than a more common compressive cutting action provided by cutting picks and the like. Advantageously each cutter includes a disc body and an arrangement of hard buttons for abrading the rock. The buttons are arranged in a manner that optimises the cutting action for the cutting apparatus.

At least some of the objectives are achieved by providing a roller cutter that includes a disc body and an arrangement of buttons for abrading the rock, wherein at least some of the buttons each include a domed cutting surface, and preferably substantially a hemi-spherical cutting surface. At least some of the objectives are achieved by providing a cutting head for use in cutting apparatus suitable for creating tunnels or subterranean roadways, said cutting head including a plurality of cutters that each include a disc body and an arrangement of buttons for abrading the rock, wherein at least some of the buttons each include a domed cutting surface, and preferably substantially a hemi-spherical cutting surface. At least some of the objectives are achieved by providing cutting apparatus suitable for creating tunnels or subterranean roadways, said cutting apparatus including a plurality of cutting heads, each cutting head including a plurality of cutters that each include a disc body and an arrangement of buttons for abrading the rock, wherein at least some of the buttons each include a domed cutting surface, and preferably substantially a hemi-spherical cutting surface.

According to one aspect of the invention there is provided a cutter for a cutting unit used in cutting apparatus suitable for creating tunnels or subterranean roadways, said cutter including: a disc body having an underside, an upper side arranged substantially opposite to the underside, and a radially peripheral part; a plurality of buttons for abrading rock, said buttons are mounted in the radially peripheral part of the disc body and protrude outwardly therefrom to engage rock during an undercutting operation, wherein at least some, and preferably each, of the buttons have a cutting part comprising a dome-shaped cutting surface.

The cutting part consists of the dome-shaped cutting surface, and therefore is entirely convex. Accordingly the domed-shaped cutting surface does not include the tapered sides of a conical button. The domed-shaped cutting surface significantly reduces the frequency of pulling (negative) side forces thereby extends the life expectancy of cutting unit bearings. The invention is particularly applicable to cutters used for cutting very hard rock, such as granite.

According to the invention, the domed-shaped cutting surface comprises a substantially hemi-spherical cutting surface. The inventors have determined that a substantially hemi-spherical cutting surface reduces the frequency of negative (pulling) side forces most significantly. The substantially hemi-spherical cutting surface also provides a well-balanced cutting surface when considering all the components of the cutting force acting on the buttons. The hemi-spherical buttons are also more robust than conical buttons. Conical buttons are prone to breaking, particularly for smaller sized conical buttons.

In preferred embodiments the radius of the cutting surface is greater than or equal to <NUM>. In preferred embodiments the radius of the cutting surface is less than or equal to <NUM>. Using cutting parts within these ranges provides a good balance between the cutting forces experienced by the buttons and the number of cutting cycles required to abrade a rock face. In preferred embodiments the disc body includes a plurality of button recesses formed in a radially peripheral surface, and each button includes a mounting part located in a respective button recess. This provides a robust cutter. Typically the cutter includes <NUM> to <NUM> button recesses and buttons.

According to the invention, the disc body has a central axis arranged substantially perpendicular to a plane of the disc.

In preferred embodiments the radially peripheral surface comprises a sloping annular surface. In preferred embodiments the sloping annular surface slopes inwardly and downwardly towards the central axis of the disc. Preferably the sloping annular surface is a lower surface.

In preferred embodiments the mounting part is substantially cylindrical and has a radius defining the cylinder, the substantially hemi-spherical cutting surface has a radius defining the cutting surface, wherein the cylinder radius substantially matches the hemi-spherical radius. This is an efficient arrangement.

In preferred embodiments the mounting part is made from a different material from the cutting part, and the cutting part is fixed to the mounting part. This enables a more expensive hard material to be used for the cutting part and a less expensive material to be used for the mounting part. For example, the mounting part can include steel. The cutting part can include tungsten carbide, for example cemented tungsten carbide.

According to the invention, each of the buttons has a central longitudinal axis that subtends an angle α with respect to a reference axis, which extends perpendicularly outwards from the central longitudinal axis of the shaft.

According to the invention the angle α is greater than or equal to <NUM>° and less than or equal to <NUM>°. The inventors have determined through detailed experimentation that buttons aligned in this manner provide the best cutting efficiency for cutting apparatus of this type, which has sideways and upwards-downwards cutting movements.

In preferred embodiments the angle α is less than or equal to <NUM>°, preferably less than or equal to <NUM>°, more preferably less than or equal to <NUM>°, and more preferably still less than or equal to <NUM>°. In preferred embodiments the angle α is greater than or equal to <NUM>°, preferably greater than or equal to <NUM>°, more preferably greater than or equal to <NUM>°, and more preferably still greater than or equal to <NUM>. The inventors have determined that a particularly advantageous range for angle α is <NUM>° to <NUM>°. The inventors have determined that these are particularly effective cutting angles, particularly when angle α is around <NUM>°.

In preferred embodiments the disc body has a recessed underside to reduce frictional engagement between the disc and a rock face during a cutting operation. Reducing frictional engagement between the underside of the disc and the rock face reduces cutter wear. The underside is arranged substantially opposite to the upper side of the disc. The underside faces towards the rock face during a cutting operation.

In preferred embodiments the underside of the disc includes a sloping annular surface that slopes inwardly into the disc body from a radially peripheral part of the disc towards the central axis. When the disc is in a substantially horizontal orientation, with the underside facing downwards, the sloping annular surface slopes upwardly and inwardly from the peripheral part of the disc, and preferably from a lower edge of the disc. In preferred embodiments the maximum diameter of the sloping annular surface is located at the peripheral part of the disc and/or a lower part of the disc.

In preferred embodiments the sloping annular surface subtends an angle γ with respect to a reference axis. The reference axis extends perpendicularly outwardly from the central longitudinal axis of the shaft. The angle γ is greater than or equal to <NUM>°, preferably greater than or equal to <NUM>°, more preferably greater than or equal to <NUM>°, and more preferably still greater than or equal to <NUM>°. Typically the angle γ is less than or equal to around <NUM>°. It is desirable to have a relatively shallow angle of slope to maximise the amount of material adjacent the buttons, to provide a strong cutting disc. The inventors have determined that a slope of around <NUM>° to <NUM>°, and preferably around <NUM>° is a good balance between reducing friction on the one hand and disc strength on the other.

In preferred embodiments the radially peripheral portion of the disc includes a sloping annular surface, said sloping annular surface sloping inwardly and upwardly towards the central axis of the disc. In preferred embodiments the sloping annular surface subtends an angle β with a reference axis that is arranged parallel with the central axis of the disc, wherein the angle β is greater than <NUM>°, preferably is greater than or equal to <NUM>°, and more preferably is greater than or equal to <NUM>°, and more preferably still is greater than or equal to <NUM>°. The annular sloping surface reduces friction between the disc and the rock face during a cutting operation. Preferably the sloping outer surface slopes inwardly and upwardly from a circumferential edge of the disc. In preferred embodiments the circumferential edge of the disc is the maximum diameter of the disc. However the buttons extend outwardly beyond the maximum diameter of the disc body. The sloping annular surface is located above the first sloping annular surface, when the disc body is oriented horizontally with the underside facing downwards. The first sloping annular surface is a lower surface, with respect to this sloping annular surface. In preferred embodiments the sloping annular surfaces converge towards a peripheral edge of the disc. In preferred embodiments the peripheral edge defines the maximum radius of the disc body. It will be appreciated that the buttons extend radially outwardly beyond the peripheral edge of the disc. In preferred embodiments the sloping annular surface formed in the underside of the disc body and this sloping annular surface formed in the radially peripheral part of the disc body converge towards a lowermost edge of the disc body.

It is desirable to have a relatively small angle β to maximise the amount of material adjacent the buttons, to provide a strong cutting disc. However, the smaller the angle β the greater the amount of friction between the disc and the rock face during a cutting operation. In preferred embodiments the angle β is less than or equal to <NUM>°, preferably is less than or equal to <NUM>°, and more preferably is less than or equal to <NUM>°, and more preferably still less than or equal to <NUM>°. The inventors have determined that a slope of around <NUM>° to <NUM>°, and particularly around <NUM>°, is a good balance between reducing friction on the one hand and disc strength on the other.

In preferred embodiments the disc body is annular.

According to another aspect of the invention there is provided a cutting unit for a cutting head used in cutting apparatus suitable for creating tunnels or subterranean roadways and the like, as set out in claim <NUM>.

The upper side of the disc body faces away from the rock face during a cutting operation.

In preferred embodiments the shaft includes a flange. The upper side faces towards the shaft flange. Typically the upper side is substantially planar, or includes a substantially planar portion. In preferred embodiments the upper side abuts the shaft flange.

According to another aspect of the invention there is provided a cutting head for cutting apparatus suitable for creating tunnels or subterranean roadways and the like, as set out in claim <NUM>.

In preferred embodiments the cutting units are mounted to a radially peripheral part of the cutting head body. Typically a cutting head includes around <NUM> to <NUM> cutting units, and preferably around <NUM> to <NUM> cutting units.

In preferred embodiments the cutting units are distributed around a pitch circle on the cutting head body.

At least some, and preferably each, of the cutting discs are arranged to freely rotate. That is, at least some, and preferably each, of the cutting discs are not independently directly driven to rotate by a drive source. Instead, all of the cutting discs are mounted to a cutting head body. The cutting head body is rotatable, typically driven by a motor. Thus the cutting disc bodies rotate with the cutting head body. However, each cutting disc body is arranged to rotate freely with respect to the cutting head body. Thus the cutting discs rotate relative to the cutting head body in response to frictional engagement with the rock face. According to another aspect of the invention there is provided cutting apparatus suitable for creating tunnels or subterranean roadways and the like, as set out in claim <NUM>.

In preferred embodiments each mounting assembly includes: a support pivotally mounted relative to the support structure via a the first pivot axis, which is aligned generally upright relative to the upward and downward facing regions such that each support is configured to pivot laterally in a sideways direction relative to the side facing regions; at least one support actuator to actuate independent movement of each of the supports relative to the support structure; an arm assembly pivotally mounted to the support via the second pivot axis aligned in a direction extending transverse including perpendicular to each support pivot axis to enable the arm to pivot independently relative to the support in an upward and downward direction relative to the upward and downward facing regions; at least one arm actuator to actuate independent pivoting movement of the arm relative to the support; wherein each rotatable cutting head is mounted towards a free end of its respective arm, and each cutting head is rotatable about a head axis orientated to extend substantially transverse to each arm pivot axis, and the cutting units provide an undercutting mode of operation. This provides a flexible cutting action that can develop new mines.

The first and second cutting assemblies are independently operable from one another. The first and second cutting heads are moveable independently of each other. The cutting units are distributed about a peripheral edge of each cutting head. Typically each cutting head includes at least <NUM> cutting units. Typically each cutting head includes less than or equal to <NUM> cutting units. The cutting units are preferably distributed about a pitch circle on the cutting head.

In preferred embodiments each rotatable cutting head is mounted towards a free end of its respective arm, and each cutting head is rotatable about a head axis orientated to extend substantially transverse to each arm pivot axis. Preferably the cutting units provide an undercutting mode of operation.

The configuration of each head to provide the undercutting action is advantageous to break the rock with less force and in turn provide a more efficient cutting operation that draws less power. Preferably, the apparatus comprises a plurality of cutters independently rotatably mounted at each rotatable cutting head. Preferably, the cutters are generally annular cutters each having a generally annular cutting edge or layered cutting edges to provide an undercutting mode of operation. More preferably, the cutters are mounted at a perimeter region of each cutting head such that the cutters circumferentially surround each cutting head. Such a configuration is advantageous to provide the undercutting action of the apparatus with the cutters first creating a channel or groove extending generally horizontally in the rock face. The cutters may then be moved upwardly to break the rock by overcoming the tensile forces immediately above the channel or groove. A more efficient cutting operation is provided requiring less force and drawing less power. Preferably, the cutters are mounted at generally cylindrical bodies and comprise generally annular cutting edges distributed around the perimeter of the cutting head. Each generally circular cutting edge is accordingly positioned side-by-side around the circumference of the cutting head with each cutting edge representing an end most part of each pivoting arm. Preferably an alignment of the rotational axes of the cutters relative to the rotational axis of the respective cutting head is the same so that the respective cutting edges are all orientated in the same position around the cutting head.

The following embodiments are not relevant for describing the claimed invention but are present for illustration purposes only. It will be apparent to the skilled person that modifications can be made so long as these modifications fall within the scope of the invention as defined by the appended claims.

In preferred embodiments each arm actuator comprises a planetary gear assembly mounted at the junction at which each arm pivots relative to each support. The apparatus may comprise a conventional planetary gear arrangement such as a Wolfram type planetary gear having a high gear ratio. The planetary gear assembly is mounted internally with each arm such that the cutting apparatus is designed to be as compact as possible.

In preferred embodiments each arm actuator includes at least one first drive motor to drive the pivoting movement of the arm relative to the support. Preferably, the apparatus comprises two drive motors to drive each of the first and second arms about their pivoting axis via the respective planetary gears. Preferably, the respective drive motors are mounted in-board of each arm and are coupled to each arm via the planetary gear assembly and/or an intermediate drive transmission.

In preferred embodiments each cutting assembly includes at least one second drive motor to drive rotation of the cutting head relative to the arm. In some embodiments each head comprises two drive motors mounted at the side of each arm. Such an arrangement is advantageous to pivot each drive motor with each cutting head and to provide a direct drive with minimal intermediate gearing.

In preferred embodiments each support actuator comprises a hydraulic linear actuator. Preferably, each support actuator comprises a linear hydraulic cylinder positioned at the lateral sides of the support structure and coupled to extend between the sled and an actuating flange extending laterally outward from each support. Such an arrangement is advantageous to minimise the overall width of the apparatus whilst providing an efficient mechanism for the sideways lateral slewing of each support and accordingly each arm.

In preferred embodiments the support structure includes a main frame and a powered sled movably mounted at the main frame to be configured to slide in a forward cutting direction of the apparatus relative to the main frame. The apparatus may further comprise a plurality of 'runners' or guide rails to minimise the frictional sliding movement of the sled over the main frame. Preferably, the apparatus comprises at least one powered linear actuator to provide the forward and rearward movement of the sled relative to the main frame. As will be appreciated, the sled may be configured to move axially/longitudinally at the machine via a plurality of different actuating mechanisms including rack and pinion arrangements, belt drive arrangements, gear arrangements and the like. Preferably the supports and the arms are mounted at the sled and are all configured to move in the forward and rearward direction collectively.

In preferred embodiments each cutting head is mounted at the sled via its respective arm and support so as to be configured to advance in the forward cutting direction. Optionally, the sled may be positioned to operate longitudinally between the supports and each of the respective arms. That is, each arm may be configured to slide in the axially forward direction relative to each support via one or a plurality of actuators. Optionally, each arm is connected to each support via a respective sliding actuator such that each arm is configured to slide independently relative to one another. Optionally, each arm may be configured to slide in a forward and rearward direction relative to each support via a coordinated parallel sliding mechanism.

In preferred embodiments each arm is configured to pivot in the upward and downward direction by up to <NUM>°; and each support is configured to pivot in the lateral sideways direction by up to <NUM>°. Optionally, each arm may be configured to pivot over a range of up to <NUM>°. Optionally, the first and second supports are configured to pivot in the lateral sideways direction by up to <NUM>°. Optionally, the supports may be configured to pivot up to <NUM>° in the lateral sideways direction. Such a configuration provides control of the profile shape and avoids any cuts or ridge that would otherwise remain on the roof and floor of the as-formed tunnel.

In preferred embodiments the apparatus comprises tracks or wheels mounted at the main frame to allow the apparatus to move in a forward and rearward direction. The tracks or wheels enable the apparatus to be advanced forwardly and rearwardly within the tunnel both when manoeuvred into and from the cutting face between cutting operations and to be advanced forwardly during cutting operations as part of the cut-and-advance cutting cycle that also utilises the sliding sled.

According to another preferred embodiment of the invention there is provided cutting apparatus suitable for creating tunnels or subterranean roadways and the like comprising, the cutting apparatus including: a main frame having generally upward, downward and side facing regions; a powered sled movably mounted at the main frame to be configured to slide in a forward cutting direction of the apparatus relative to the main frame; first and second arms pivotally mounted to the sled by respective pivot arm axes aligned in a direction extending transverse including perpendicular to a longitudinal axis of the main frame to allow each arm to pivot independently of one another in an upward and downward direction relative to the upward and downward facing region of the main frame; at least one first and second arm actuator to actuate independent pivoting movement of the first and second arms relative to one another and the main frame; each of the first and second arms having a rotatable cutting head mounted at so as to be configured to be moved in the upward and downward direction and advanced in the forward cutting direction, each cutting head rotatable about a head axis orientated to extend substantially transverse to respective pivot arm axes; and wherein each of the cutting heads includes a plurality of cutting units, each cutting unit includes a rotatable shaft having a central longitudinal axis and a cutter mounted to the shaft, said cutter being arranged to any configuration described herein.

In preferred embodiments each of the first and second arms is respectively mounted at a first and second support slidably mounted relative to the main frame via a common or respective slidable means such that each first and second support is configured to slide laterally in a sideways direction relative to the side facing regions.

In preferred embodiments each rotatable cutting head comprises a generally annular roller cutter each having a generally annular cutting edge or layered cutting edges to provide an undercutting mode of operation.

In preferred embodiments each of the roller cutters is independently rotatably to its respective cutting head.

In preferred embodiments the plurality of roller cutters are generally annular roller cutters each having a generally annular cutting edge or layered cutting edges to provide an undercutting mode of operation.

In preferred embodiments each of the first and second arm actuator comprises a planetary gear assembly mounted at the junction at which each arm pivots relative to each support.

Referring to <FIG>, cutting apparatus <NUM> comprises a support structure <NUM> mounting a plurality of cutting components configured to cut into a rock or mineral face <NUM> to create tunnels or subterranean roadways. Apparatus <NUM> is configured specifically for operation in an undercutting mode in which a plurality of rotatable roller cutters <NUM> may be forced into the rock to create a groove or channel and then to be pivoted vertically upward so as to overcome the reduced tensile force immediately above the groove or channel and break the rock. Accordingly, the present cutting apparatus is optimised for forward advancement into the rock or mineral utilising less force and energy typically required for conventional compression type cutters that utilise cutting bits or picks mounted at rotatable heads. However, the present apparatus may be configured with different types of cutting head to those described herein including in particular pick or bit type cutting heads in which each pick is angularly orientated at the cutting head to provide a predetermined cutting attack angle.

Referring to <FIG>, the support structure <NUM> includes a main frame <NUM>. The main frame <NUM> comprises lateral sides <NUM> to be orientated towards the wall of the tunnel; an upward facing region <NUM> to be orientated towards a roof of the tunnel; a downward facing region <NUM> orientated to be facing the floor of the tunnel; a forward facing end <NUM> intended to be positioned facing the cutting face and a rearward facing end <NUM> intended to be positioned facing away from the cutting face.

The support structure includes an undercarriage <NUM>. The undercarriage <NUM> is mounted generally below main frame <NUM> and in turn mounts a pair of crawler tracks <NUM> driven by a hydraulic (or electric) motor to provide forward and rearward movement of apparatus <NUM> over the ground when in a non-cutting mode. A pair of rear ground engaging jacking legs <NUM> are mounted at frame sides <NUM> towards rearward end <NUM> and are configured to extend and retract linearly relative to frame <NUM>. Frame <NUM> further comprises a forward pair of jacking legs <NUM> also mounted at each frame side <NUM> and towards forward end <NUM> and being configured to extend and retract to engage the floor tunnel. By actuation of legs <NUM>, <NUM>, main frame <NUM> and in particular tracks <NUM> may be raised and lowered in the upward and downward direction so as to suspend tracks <NUM> off the ground to position apparatus <NUM> in a cutting mode. A pair of roof engaging grippers <NUM> project upwardly from main frame <NUM> at frame rearward end <NUM> and are extendable and retractable linearly in the upward and downward direction via control cylinders <NUM>. Grippers <NUM> are therefore configured to be raised into contact with the tunnel roof and in extendable combination with jacking legs <NUM>, <NUM> are configured to wedge apparatus <NUM> in a stationary position between the tunnel floor and roof when in the cutting mode.

The support structure <NUM> includes a sled <NUM>. The sled <NUM> is slidably mounted on top of main frame <NUM> via a slide mechanism <NUM>. Sled <NUM> is coupled to a linear hydraulic cylinder <NUM> such that by reciprocating extension and retraction of cylinder <NUM>, sled <NUM> is configured slide linearly between frame forward and rearward ends <NUM>, <NUM>.

A pair of hydraulically actuated bolting units <NUM> are mounted at main frame <NUM> between sled <NUM> and roof gripping unit <NUM>, <NUM> relative to a lengthwise direction of the apparatus. Bolting units <NUM> are configured to secure a mesh structure (not shown) to the roof of the tunnel as apparatus <NUM> is advanced in a forward cutting direction. Apparatus <NUM> also comprises a mesh support structure (not shown) mounted generally above sled <NUM> so as to positionally support the mesh directly below the roof prior to bolting into position.

The cutting apparatus <NUM> includes first and second cutting assemblies <NUM>. The first cutting assembly <NUM> includes a first cutting head <NUM> and a first mounting assembly <NUM>. The second cutting assembly <NUM> includes a second cutting head <NUM> and a second mounting assembly <NUM>. Each of the first and second mounting assemblies <NUM> includes a support <NUM>. Each support <NUM> is pivotally mounted at, and projects forwardly from, sled <NUM> immediately above frame forward end <NUM>. Supports <NUM> are generally spaced apart in a lateral widthwise direction of the apparatus <NUM> and are configured to independently pivot laterally outward from one another relative to sled <NUM> and main frame <NUM>. Each support <NUM> comprises a forward end <NUM> and a rearward end <NUM> referring to <FIG>. A first mount flange <NUM> is provided at support rearward end <NUM> being generally rearward facing. A corresponding second mount flange <NUM> projects laterally outward from a side of sled <NUM> immediately behind the first flange <NUM>. A pair of linear hydraulic cylinders <NUM> are mounted to extend between flanges <NUM>, <NUM> such that by linear extension and retraction, each support <NUM> is configured to pivot in the generally horizontal plane and in the lateral sideways direction relative to frame sides <NUM>. Referring to figured <NUM>, each support <NUM> is mounted at sled <NUM> via a pivot rod <NUM> extending generally vertically (when apparatus <NUM> is positioned on horizontal ground) through sled <NUM> and being suspended generally above the main frame forward end <NUM>. Each support <NUM> is therefore configured to pivot or slew about pivot axis <NUM>. Referring to <FIG>, each support <NUM> is further coupled to a respective inner hydraulic cylinder <NUM> mounted at an inner region of sled <NUM> to cooperate with side mounted cylinders <NUM> to laterally slew each support <NUM> about pivot axis <NUM>.

Referring to <FIG> and <FIG>, as the respective pivot axes <NUM> are spaced apart in the widthwise direction of apparatus <NUM>, supports <NUM> are capable of being slewed inwardly to a maximum inward position <NUM> and to be slewed laterally outward to a maximum outward position <NUM>. According to the specific implementation, an angle between the inner and outer slewing positions <NUM>, <NUM> is <NUM>°.

Referring to <FIG>, each mounting assembly <NUM> includes an arm <NUM>. Each arm is pivotally mounted generally at the forward end <NUM> of each support <NUM>. Each cutting head <NUM> is rotatably mounted at a free distal end of each arm <NUM>. Each cutting head <NUM> comprises a disk like (generally cylindrical) configuration.

Each cutting head <NUM> includes a body <NUM> and <NUM> cutting units <NUM>. Details of the cutting units <NUM> are best seen in <FIG>. Each cutting unit <NUM> includes a casing <NUM>, a shaft <NUM>, a first bearing <NUM>, a second bearing <NUM>, a third bearing <NUM> and a cutter <NUM> comprising a disc body <NUM> and an arrangement of buttons <NUM>. The shaft <NUM>, and hence the disc, has a central longitudinal axis <NUM>. The central axis <NUM> is arranged substantially perpendicular to the plane of the disc. The shaft <NUM> is journalled in the first, second and third bearings <NUM>,<NUM>,<NUM> and is arranged to rotate freely in the bearings. The bearings <NUM>,<NUM>,<NUM> are typically roller bearings. The shaft <NUM> includes a flange <NUM> towards a lower end <NUM> of the shaft. The disc <NUM> is fixed to the lower end <NUM> of the shaft, and rotates with the shaft. The disc <NUM> is attached to the shaft by bolts <NUM>. The bolts <NUM> pass through holes <NUM> formed through the plane of the disc <NUM>, and into threaded holes <NUM> in the flange <NUM>. The disc <NUM> is annular. The disc <NUM> has a central through hole <NUM>. The disc <NUM> is mounted onto the shaft <NUM> such that the lower end <NUM> of the shaft protrudes through the central through hole <NUM>. A collar assembly <NUM> sits in an annular space between an outer surface <NUM> of the lower end of the shaft and an inner surface <NUM> of the annular disc.

The disc <NUM> includes an upper side <NUM>, an underside <NUM>, and a radially peripheral part <NUM>.

The upper side <NUM> faces generally towards arms <NUM>, and away from the rock face <NUM>, during an undercutting operation. The upper side <NUM> includes an annular upper surface <NUM>, which is substantially planar. The upper surface <NUM> abuts against the flange <NUM>.

The radially peripheral part <NUM> is generally the outer edge portion of the disc. The radially peripheral part <NUM> includes a first (upper) annular tapering surface <NUM>, which tapers upwardly and inwardly towards the upper surface <NUM>. The first tapering surface <NUM> has a maximum diameter at its lower edge <NUM> and a minimum diameter at its upper edge <NUM>. The radially peripheral part <NUM> includes a second (lower) annular tapering surface <NUM>, which tapers downwardly and inwardly from the lower edge <NUM> of the first tapering surface, to its own lower edge <NUM>. Thus the second annular tapering surface <NUM> has a maximum diameter at edge <NUM> and a minimum diameter at edge <NUM>. The edge <NUM> is the maximum diameter of the disc <NUM>.

The underside <NUM> faces generally towards the rock face <NUM> during an undercutting operation. The underside <NUM> is recessed to reduce the amount of friction between the disc <NUM> and the rock face <NUM>. It will be appreciated that the recessed underside <NUM> can take many different forms, for example the recessed underside <NUM> can have a substantially concave formation. A particularly preferred arrangement is for the underside <NUM> to include an annular tapering surface <NUM> which tapers inwardly and upwardly from lower edge <NUM> to upper edge <NUM>. Thus the annular tapering surface <NUM> has a maximum diameter at lower edge <NUM> and a minimum diameter at upper edge <NUM>.

Many holes <NUM> are bored into the annular tapering surface <NUM>. The number of holes is selected according to the application. Typically around <NUM> to <NUM> holes <NUM> are formed in the disc <NUM>. A button <NUM> is located in each of the holes <NUM>. The buttons <NUM> are arranged abrade rock as the cutting head <NUM> rotates. Preferred cutters <NUM> include <NUM> or <NUM> buttons <NUM>.

Each button comprises a mounting part 710a and a cutting part 710b. The mounting part 710a comprises a cylindrical body of radius Rc. The cutting part 710b comprises a body having a domed cutting surface <NUM>, and in particular the cutting surface consists of a hemi-spherical cutting surface <NUM>. The cutting part 710b is mounted at one end of the cylindrical body. Preferably the hemi-spherical surface matches the size of the cylindrical body. That is, the radius RHS of the hemi-spherical cutting surface can be substantially equal to the radius Rc of the cylindrical body. The radius RHS of the hemi-spherical cutting surface is typically in the range <NUM> to <NUM>.

The cutting part 710b body can include a substantially planar underside for engagement with an end face of the cylindrical body. Alternatively, the cutting part 710b and the end of the cylindrical body can be arranged for mating engagement. For example, one of the underside of the cutting part and the end of the cylindrical body can include a protrusion and the other of the underside of the cutting part and the end of the cylindrical body can include a recess for receiving the protrusion. This is to assist fixing the cutting part 710b to the mounting part 710a.

Preferably the cylindrical body 710b is made from steel. The hemi-spherical body is made from a hard material such as tungsten carbide. While the buttons <NUM> are preferably made from two separate parts that are joined together, it will be appreciated that the button <NUM> can comprise an integral body that includes the mounting part 710a and the cutting part 710b.

The mounting part 710a of the button <NUM> is inserted into its respective hole <NUM>. The hole <NUM> is sized to receive the entirety of the mounting part 710a. The cutting part 710b sits proud of the annular tapering surface <NUM>. Each button <NUM> protrudes outwardly from the disc beyond the maximum diameter <NUM> of the disc. Thus the circumscribed diameter of the cutting head <NUM> is defined by the extent to which the buttons <NUM> protrude beyond the disc.

During a cutting operation cutting forces are generated at the cutting surface <NUM> of each button <NUM>. The cutting force can be broken down into three orthogonal component parts, at tip region 710c: "side force" (see direction X in <FIG> and <FIG>, wherein a positive force represents the disc pushing on the bearings and a negative force represents the disc pulling on the bearings); "roll force" (see direction Y in <FIG>, direction Y is perpendicular to the plane of the paper in <FIG>, wherein a positive force represents the buttons compressing rock and a negative force represents the rock compressing the buttons); and "normal force" (see direction X in <FIG> and <FIG>, wherein a positive force represents the disc pushing on the rock and a negative force represents the disc bouncing back from the rock). The inventors have determined that by using buttons <NUM> having a hemi-spherical cutting part 710b, there is a significant reduction in the extent to which the side force component changes direction during a cutting operation. This is illustrated in the graph of <FIG>. The graph shows probability (y axis) and side force (x axis) for a cutter including hemi-spherical buttons and, for comparison purposes, a cutter including conical buttons. The data was generated by attaching a cutting unit <NUM> to a load cell. Since the geometry of the cutting unit <NUM> and load cell is known, the output from the load cell accurately indicates the magnitude of forces experienced during the cutting operation. In the graph, negative side force values represent pulling side forces, which urge the disc <NUM> away from the bearings <NUM>,<NUM>,<NUM>. Positive side force values represent pushing side forces, which urge the disc <NUM> towards the bearings <NUM>,<NUM>,<NUM>. It can be seen from the graph in <FIG>, that the conical buttons produce a negative (pulling) side force for around <NUM>% of the cutting operation. It will be understood by the skilled person that there is a somewhat random alternating of the pushing and pulling forces during a cutting operation for the conical buttons. The graph also shows that the hemi-spherical buttons <NUM> produce a negative (pulling) side force for a much smaller proportion of the cutting operation, almost to the point of elimination of the side force in the pulling direction.

The inventors have determined that the pulling side forces cause most damage to the bearings <NUM>,<NUM>,<NUM>. Therefore it is desirable to minimise the pulling side forces. The pushing side forces are less damaging due to the mechanical arrangement of the cutting units <NUM>. The interaction of upper and lower casing members 701a,701b mechanically blocks the potentially damaging effect of pushing forces on the bearings <NUM>,<NUM>,<NUM>. Accordingly, the use of hemi-spherical buttons is advantageous to the design and life expectancy of the bearings <NUM>,<NUM>,<NUM>. This is particularly the case in the context of the cutting apparatus <NUM>.

Each button <NUM> has a central longitudinal axis <NUM>. The central longitudinal axis of the button <NUM> subtends an angle α with a reference axis <NUM>, which projects perpendicularly outwards from the central longitudinal axis of the shaft <NUM> (see <FIG>). The reference axis <NUM> is aligned with the plane of the disc body. The angle α determines how the resultant cutting force acting on the tool will be split along the button <NUM> geometry, and perpendicular to it. An α = <NUM>° arrangement would be optimised for a pure shear up cutting movement, however this arrangement would not work in the sump phase. The inventors have determined that α must be larger than zero in order for the machine to operate. For at least some buttons <NUM>, and preferably each button <NUM>, on the disc <NUM>α is set in the range <NUM>° to <NUM>°, preferably between <NUM>° and <NUM>°. The inventors have determined, after significant testing, that these ranges provide the best overall cutting effect for cutters <NUM> for this type of boring machine. In particular, taking into account the range of movement of the cutting heads <NUM> that is undertaken by this type of rock cutting apparatus.

Other geometric aspects of the disc <NUM> are important for the purposes of strength and the effect of friction caused by rock during a cutting operation. It can be seen from <FIG> that the surface <NUM> subtends an angle γ to a reference axis <NUM>. The reference axis <NUM> is perpendicular to the central longitudinal axis of the shaft <NUM>. The reference axis <NUM> is aligned with surface <NUM>. The reference axis <NUM> extends radially outwards from the central longitudinal axis <NUM> at a position substantially in line with lower edge <NUM>. The inventors have determined that when γ is substantially equal to <NUM>° the interaction between the surface <NUM> and the rock is too large and causes significant wear to the disc. However if γ is too large the amount of material that surrounds to the buttons <NUM> is significantly reduced thereby degrading the strength of the cutter <NUM>. The inventors have determined, by significant testing, that γ should be greater than <NUM>°, and ideally should be in the range <NUM>° to <NUM>° to balance friction reduction, while maintaining disc strength. A particularly preferred range is <NUM>° to <NUM>°, and a particularly preferred value is around <NUM>°.

Another geometric aspect of the disc <NUM> that is important for the purpose of determining the frictional force acting on the disc <NUM> during a cutting operation is the slope of the second tapered surface <NUM>. It can be seen from <FIG> that the second tapered surface <NUM> subtends an angle β with a reference axis <NUM> which is arranged parallel with the central longitudinal axis <NUM>. In <FIG>, the reference axis <NUM> extends vertically upwards from surface <NUM>, for example from the lower edge <NUM> of the surface, when the disc <NUM> is in a substantially horizontal orientation with the underside <NUM> facing downwards towards the ground. The inventors have determined that when β is substantially equal to <NUM>° the interaction between the surface <NUM> and the rock generates large frictional forces, and there is significant wear to the disc <NUM>. The inventors have determined, by significant testing, that β should be greater than <NUM>°, and ideally should be in the range <NUM>° to <NUM>° to reduce the frictional forces generated, while maintaining sufficient strength in the vicinity of the buttons <NUM>.

The size of the cutting disc <NUM> is selected for the application. A preferred maximum diameter of the disc is typically around <NUM>" (<NUM>).

Thus the plurality of generally annular or disc shaped roller cutters <NUM> are mounted at the circumferential perimeter of each head <NUM> and comprise a sharp annular cutting edge configured specifically for undercutting the rock. The cutting units <NUM> are mounted to the body <NUM> about a pitch circle, and are typically evenly distributed about the pitch circle. Cutters <NUM> are rotatably mounted independently relative to one another and head <NUM> and are generally free to rotate about their own axis. Each cutter <NUM> projects axially beyond a forwardmost annular edge of head <NUM> such that when arms <NUM> are orientated to be extending generally downward, roller cutters <NUM> represent a lowermost part of the entire head <NUM> and arm <NUM> assembly.

Each arm <NUM> may be considered to comprise a length such that arm <NUM> is mounted at each respective support <NUM> at or towards a proximal arm end and to mount each head <NUM> at a distal arm end. In particular, each arm <NUM> comprises an internally mounted planetary gear indicated generally be reference <NUM>. Each gear <NUM> is preferably a Wolfrom type and is coupled to a drive motor <NUM> via a drive train indicated generally by reference <NUM>. A pair of drive motors <NUM> are mounted at the lateral sides of each arm <NUM> and are orientated to be approximately parallel with the rotational axis of each respective cutting head <NUM> as shown in <FIG>. Each arm <NUM> further comprise an internal drive and gear assembly <NUM> coupled to a gear box <NUM> mounted at one end of each of the drive motors <NUM>. Each cutting head <NUM> is driveably coupled to the drive motors <NUM> via the respective gear assembly <NUM> to provide rotation of cutting head <NUM> about axis <NUM>.

As shown in <FIG>, each arm <NUM> is coupled to a respective motor <NUM> mounted at a forward end of sled <NUM>. Each planetary gear <NUM> is centred on a pivot rod <NUM> having a pivot axis <NUM> referring to <FIG>. Each axis <NUM> is aligned to be generally horizontal when apparatus <NUM> is positioned on horizontal ground. Accordingly, each arm <NUM> is configured to pivot (relative to each support <NUM>, sled <NUM> and main frame <NUM>) in the upward and downward direction (vertical plane) by actuation of each motor <NUM>. As such, each cutting head <NUM> and in particular the cutters <NUM> may be raised and lowered along the arcuate path <NUM> referring to <FIG>. In particular, each arm <NUM>, head <NUM> and cutters <NUM> may be pivoted between a lowermost position <NUM> and an uppermost raised position <NUM> with an angle between positions <NUM>, <NUM> being approximately <NUM>°. When in the lowermost position <NUM>, each roller cutter <NUM> and in particular head <NUM> is suspended in a declined orientation such that a forwardmost cutter <NUM> is positioned lower than a rearwardmost cutter <NUM>. According to the specific implementation, this angle of declination is <NUM>°. This is advantageous to engage the cutters <NUM> into the rock face at the desired attack angle to create the initial groove or channel during a first stage of the undercutting operation. Additionally, the extensive range of movement of the cutting heads <NUM> over the rock face is possible due, in part, to axis <NUM> being separated and positioned forward relative to axis <NUM> by a distance corresponding to a length of each support <NUM>.

Thus the cutting movement of the apparatus <NUM> can be conceptualised as comprising two main sub movements. At first, there is a shallow interaction of the cutters <NUM> with the rock face towards the mine floor level (often referred to as "sump in"). Here the cut depth is increased from zero to a few millimetres. At this stage each disc body <NUM> is approximately parallel with the floor, with the underside <NUM> facing towards the floor.

The arms <NUM> then move the head <NUM> upwards across the rock face <NUM>. In this stage the disc bodies <NUM> are arranged substantially perpendicular to the floor, or a moving towards that orientation, with the underside <NUM> facing towards the rock face <NUM>. At this stage, the cut thickness reaches it maximum. This is typically referred to as "shear up". The shear up phase lasts longer in the cutting cycle.

Referring to <FIG>, each support pivot axis <NUM> is aligned generally perpendicular to each arm pivot axis <NUM>. Additionally, a rotational axis <NUM> of each cutting head <NUM> is orientated generally perpendicular to each arm pivot axis <NUM>. A corresponding rotational axis <NUM> of each cutter <NUM> is angularly disposed relative to the cutting head axis <NUM> so as to taper outwardly in the downward direction. In particular, each roller cutter axis <NUM> is orientated to be aligned closer to the orientation of each cutting head rotational axis <NUM> and support pivot axis <NUM> relative to the generally perpendicular arm rotational axis <NUM>.

Accordingly, each support <NUM> is configured to slew laterally outward in a horizontal plane about each support axis <NUM> between the extreme inner and outward positions <NUM>, <NUM>. Additionally and referring to <FIG>, each respective arm <NUM> is configured to pivot in the upward and downward direction about arm pivot axis <NUM> to raise and lower the cutters <NUM> between the extreme positions <NUM>, <NUM>.

A gathering head <NUM> is mounted at main frame forward end <NUM> immediately rearward behind each cutting head <NUM>. Gathering head <NUM> comprises a conventional shape and configuration having side loading aprons and a generally inclined upward facing material contact face to receive and guide cut material rearwardly from the cutting face (and cutting heads <NUM>). Apparatus <NUM> further comprises a first conveyor <NUM> extending lengthwise from gathering head <NUM> to project rearwardly from frame rearward end <NUM>. Accordingly, material cut from the face is gathered by head <NUM> and transported rearwardly along apparatus <NUM>.

Referring to <FIG>, a detachable control unit <NUM> is mounted to the frame rearward end <NUM> via a pivot coupling <NUM>. Control unit <NUM> comprises a personnel cabin <NUM> (to be occupied by an operator). Unit <NUM> further comprises an electric and hydraulic power pack <NUM> to control the various hydraulic and electrical components of apparatus <NUM> associated with the pivoting movement of supports <NUM> and arms <NUM> in addition to the sliding movement of sled <NUM> and the rotational drive of cutting heads <NUM>.

Control unit <NUM> further comprises a second conveyor <NUM> extending generally lengthwise along the unit <NUM> and coupled at its forwardmost end to the rearwardmost end of first conveyor <NUM>. Unit <NUM> further comprises a discharge conveyor <NUM> projecting rearwardly from the rearward end of second conveyor <NUM> at an upward declined angle. Accordingly, cut material is capable of being transported rearwardly from cutting heads <NUM> along conveyors <NUM>, <NUM> and <NUM> to be received by a truck or other transportation vehicle.

In use, apparatus <NUM> is wedged between the tunnel floor and roof via jacking legs <NUM>, <NUM> and roof grippers <NUM>. Sled <NUM> may then be displaced in a forward direction relative to main frame <NUM> to engage cutters <NUM> onto the rock face. Cutting heads <NUM> are rotated via motors <NUM> that create the initial groove or channel in the rock face at a lowermost position. A first arm <NUM> is then pivoted about axis <NUM> via motor <NUM> to raise cutters <NUM> along path <NUM> to achieve the second stage undercutting operation. The first support <NUM> may then be slewed in the lateral sideways direction via pivoting about axis <NUM> and combined with the raising and lowering rotation of cutters <NUM> creates a depression or pocket within the rock immediately forward of the first arm <NUM> and support <NUM>. The second arm <NUM> and associated head <NUM> and cutters <NUM> are then actuated according to the operation of the first arm <NUM> involving pivoting in both the vertical and horizontal planes. This sequential dual pivoting movement of the second arm <NUM> is independent of the initial dual pivoting movement of the first arm <NUM>. A phasing and sequencing of the pivoting of arms <NUM> about axes <NUM> and supports <NUM> about axes <NUM> is controlled via control unit <NUM>. The cutters <NUM> are optimised for the cutting action, and balancing low frictional engagement of the cutters <NUM> with the rock face <NUM> and strength of the cutters <NUM>.

When the maximum forward travel of sled <NUM> is achieved, jacking legs <NUM>, <NUM> are retracted to engage tracks <NUM> onto the ground. Tracks <NUM> are orientated to be generally declined (at an angle of approximately <NUM>° relative to the floor) such that when ground contact is made, the roller cutters <NUM> are raised vertically so as to clear the tunnel floor. The apparatus <NUM> may then be advanced forward via tracks <NUM>. Jacking legs <NUM>, <NUM> may then be actuated again to raise tracks <NUM> off the grounds and grippers <NUM> moved into contact with the tunnel roof to repeat the cutting cycle. A forwardmost roof gripper <NUM> is mounted above sled <NUM> to stabilise the apparatus <NUM> when sled <NUM> is advanced in the forward direction via linear actuating cylinder <NUM>.

Although the present invention has been described in connection with specific preferred embodiments, it should be understood that the invention as claimed should not be unduly limited to such specific embodiments. Furthermore, it will be apparent to the skilled person that modifications can be made so long as these fall within the scope of the invention as defined by the appended claims.

Claim 1:
A cutter (<NUM>) for a cutting unit (<NUM>) used in cutting apparatus (<NUM>) suitable for creating tunnels or subterranean roadways, said cutter (<NUM>) including:
a disc body (<NUM>) having an underside (<NUM>), an upper side (<NUM>) arranged substantially opposite to the underside (<NUM>), and a radially peripheral part (<NUM>);
a plurality of buttons (<NUM>) for abrading rock, said buttons (<NUM>) are mounted in the radially peripheral part (<NUM>) of the disc body and protrude outwardly therefrom to engage rock during an undercutting operation, wherein at least some of the buttons (<NUM>) have a cutting part (710b) comprising a hemi-spherical cutting surface (<NUM>), characterized in that the disc has a central axis (<NUM>) arranged substantially perpendicular to a plane of the disc and each button (<NUM>) has a central longitudinal axis (<NUM>) that subtends an angle α with respect to a reference axis (<NUM>), which extends perpendicularly outwards from the central axis (<NUM>) of the disc, wherein the angle α is greater than or equal to <NUM>° and less than or equal to <NUM>°.