Patent Publication Number: US-2023151733-A1

Title: Disk cutter

Description:
FIELD OF THE INVENTION 
     The present disclosure relates to a disk cutter for use in mining and excavation machines or in trenching machines. In particular, it relates to a disk cutter with cutting elements comprising superhard materials, such as polycrystalline diamond. 
     BACKGROUND 
     Many types of rock formations are available around the world as large deposits, commonly known as slabs. Various types of mining equipment are deployed in above ground quarries in order to extract the slabs from the ground. The slabs are retrieved using specialist equipment, typically dragged from their resting place by large and very powerful vehicles. Rock slabs may weigh up to 40 tons (40,000 kg). Processing, such as polishing, may take place on site, or alternatively the slabs may be transported off site for cutting into appropriately sized pieces for domestic and industrial use. 
     Providing a compact and versatile cutting assembly to facilitate the mining and extraction of geometrically or non-geometrically shaped blocks of specific rock formations is challenging. 
     The Applicant&#39;s co-pending applications WO 2019/180164 A1, WO 2019/180169 A1, WO 2019/180170 A1 disclose a cutting assembly comprising a circular disk cutter, which is moveable between horizontal and vertical cutting orientations. Cylindrical cutting elements and a corresponding quantity of tool holders are arranged and seated around a circumferential surface of the disk cutter. Each tool holder may be at least partially laterally offset with respect to the circular body. 
     It is an object of the invention to provide a super-compact cutting assembly particularly suitable for robotic application. 
     SUMMARY OF THE INVENTION 
     In accordance with a first aspect of the invention, there is provided a disk cutter for a cutting assembly of a rock excavation machine, the disk cutter comprising a cutter body with a diameter of less than 500 mm, the cutter body including at least one light-weighting aperture, a plurality of tool holders mounted in succession along a peripheral surface of the cutter body, and a cutting element mounted to at least one of the plurality of tool holders, wherein the total mass of the disk cutter is less than 5 kg. 
     This arrangement is particularly advantageous for use in a robotic cutting assembly. Activity may take place underground but the robotic cutting assembly may be operated remotely from above ground. This minimises local human involvement, rendering cutting operations safer. Thanks to the reduced weight, the cutting assembly is nimble and easy to manoeuvre from afar. 
     Preferably, the cutter body comprises a plurality of light-weighting apertures. The cutter body may comprises more than three light-weighting apertures. For example, the cutter body may comprise four, five or six light-weighting apertures. 
     Optionally, the cutter body comprises a drive spindle aperture for receiving a drive spindle and a plurality of spokes, one of said plurality of light-weighting apertures being located between a pair of adjacent spokes. 
     The drive spindle aperture may be located radially offset from a centre of the body. Alternatively, the drive spindle aperture may be located radially centrally. 
     Preferably, the plurality of spokes extend radially outwardly from the drive spindle aperture. The plurality of spokes may be arranged asymmetrically about the driver spindle aperture. Alternatively, the plurality of spokes may be arranged symmetrically about the driver spindle aperture. 
     Preferably, the spokes taper from a first end towards a second end. Optionally, the second end is located at or near a peripheral surface of the body. 
     The cutter body may comprise a series of slots. 
     In an embodiment, the cutter body has a diameter of less than 450 mm. Preferably, the cutter body has a diameter of between 200 and 400 mm. 
     Preferably, the cutter body comprises aluminium alloy. 
     Optionally, the tool holder comprises a body portion and a pair of spaced apart legs extending from the body portion that sit astride the cutter body. 
     Optionally, a single cutting element is mounted in a tool holder. The single cutting element may be mounted centrally on the tool holder. 
     Optionally, two cutting elements are mounted in a tool holder. The two cutting elements may be arranged spaced apart from each other on the tool holder. 
     Optionally, the two cutting elements point outwardly from the plane of the cutter body. 
     Preferably, the cutting element comprises polycrystalline diamond (PCD). The cutting element may be a polycrystalline diamond compact (PDC). 
     Preferably, the total mass of the disk cutter is less than 3 kg. 
     In accordance with a second aspect of the invention, there is provided a robotic cutting assembly for a rock excavation machine comprising a disk cutter in accordance with the first aspect of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will now be more particularly described, by way of example only, with reference to the accompanying drawings, in which 
         FIG.  1    is a schematic plan view of an underground mine incorporating a first variant of a known cutting assembly as part of a long wall mining system, and in particular shows the cutting assembly in a horizontal orientation; 
         FIG.  2    is a schematic end view of the long wall mining system of  FIG.  1   ; 
         FIG.  3    is a schematic plan view of an underground mine incorporating a second variant of a known cutting assembly as part of a long wall mining system, and in particular shows the cutting assembly in a vertical orientation; 
         FIG.  4    is schematic end view of the long wall mining system of  FIG.  3   ; 
         FIG.  5    is a perspective view of a disk cutter in a first embodiment of the invention, with a generally circular cutter body, a plurality of tool holders mounted to the disk cutter and a cutting element secured to each tool holder; 
         FIG.  6    is a side view of the disk cutter of  FIG.  5   ; 
         FIG.  7    is a side view of a first embodiment of a tool holder and cutting element forming part of the disk cutter of  FIG.  5   ; 
         FIG.  8    is a front view of the tool holder and cutting element of  FIG.  7   ; 
         FIG.  9    is a side view of a second embodiment of a tool holder and cutting element; 
         FIG.  10    is a front view of the tool holder and cutting element of  FIG.  9   ; 
         FIG.  11    is a side view of a second embodiment of the cutter body; 
         FIG.  12    is a side view of a third embodiment of the cutter body; 
         FIG.  13    is a side view of a fourth embodiment of the cutter body; 
         FIG.  14    is a perspective view of a disk cutter in a second embodiment of the invention; 
         FIG.  15    is a side view of the disk cutter of  FIG.  14   ; 
         FIG.  16    is a perspective view of a third embodiment of a tool holder and cutting element; 
         FIG.  17    is a side view of the tool holder and cutting element of  FIG.  16   ; and 
         FIG.  18    is a front view of the tool holder and cutting element of  FIG.  16   . 
     
    
    
     In the drawings, similar parts have been assigned similar reference numerals. 
     DETAILED DESCRIPTION 
     Referring initially to  FIGS.  1  to  2   , a known cutting assembly for slicing into natural formations  2  underground is indicated generally at  10 . 
     The cutting assembly forms part of a long wall mining system  1 , commonly found in underground mines. The cutting assembly is a substitute for known shearer technology, which operates on a mine floor  4 , amidst a series of adjustable roof supports  6 . As the shearer advances in the direction of mining, the roof supports  6  are positioned to uphold the mine roof  8  directly behind the shearer. Behind the roof supports  6 , the mine roof  6  collapses in a relatively controlled manner. Typically, a gathering arm collects mined rock at the cutting face and transfers it onto a conveying system for subsequent removal from the mine. 
     As indicated in  FIGS.  1  and  2   , the cutting assembly  10  comprises a base unit  12 , a pair of spaced apart support arms  14  extending from the base unit  12 , a drive spindle  16  extending between and rotatably mounted to the pair of moveable support arms  14 , and a plurality of disk cutters  18  fixed about the drive spindle  16 . 
     In a second known cutting assembly, indicated in  FIGS.  3  and  4   , a single support arm  14  extends from the base unit  12 . The drive spindle  16  is supported centrally by the single support arm  14 , and the plurality of disk cutters  18  is mounted to the drive spindle  16 , distributed either side of the single support arm  14 . 
     The or each disk cutter  18  is typically mounted at is centre (i.e. centrally) about the drive spindle  16 . 
     The base unit  12  functions as a transport system for the disk cutter  18 . The base unit  12  is moveable to advance and retract the disk cutter  18  into and out of an operational position, in close proximity to the rock formation  2  to be cut. The speed at which the base unit  12  moves closer to the rock formation  2  is one of several variables determining the feed rate of the cutting assembly  10  into the rock formation  2 . The base unit  12  (in concert with the roof supports  6 ) is also moveable sideways, from left to right and vice versa, along the long wall of the rock formation  2  to be mined. 
     Each support arm  14  is configured to be moveable into a first and a second cutting orientation. In the first cutting orientation, best seen in  FIGS.  1  and  2   , the drive spindle  16  is horizontal. As a result, cuts in the rock formation  2  made by the disk cutter  18  are correspondingly vertical. In the second cutting orientation, best seen in  FIGS.  3  and  4   , the drive spindle  16  is vertical. Consequently, cuts in the rock formation  2  made by the disk cutter  18  are correspondingly horizontal. First and second cutting orientations are possible with either first or second embodiments mentioned above. 
     The support arm(s)  14  may also be moveable such that the drive spindle  16  is operable in any cutting orientation between the aforementioned vertical and horizontal, though this is not essential. The support arm(s)  14  may alternatively be configured such that they are moveable between the first and second cutting orientations but only fully operational (i.e. the disk cutter(s) to rotate in order to facilitate cutting or pulverising of the rock) in the first and second cutting orientations. 
     Each support arm  14  is moveable between a first operative position and a second operative position, in optionally each of the first and second cutting orientations, according to the depth of cut required. This is indicated by double end arrow A in  FIG.  2   . For example, in the first operative position, the drive spindle  16  is lowered so as to be in close proximity to the mine floor  4  and in the second operative position, the drive spindle  16  is raised so as to be in close proximity to the mine roof  8 . 
     Each support arm  14  may have a first arm portion connected to a second arm portion by a pivot joint (or alternatively, a universal joint), each first and second arm portion being independently moveable relative to each other. This arrangement augments the degrees of freedom with which the cutting assembly  10  may operate and advantageously improves its manoeuvrability. 
     The drive spindle  16  is driven by a motor to rotate at a particular speed. The power of the motor is typically between 20 and 50 kW per disk cutter  18 , depending on the type of disk cutter  18  selected and the cutting force required. 
     A disk cutter specially adapted for use in a robotic cutter assembly has been devised. 
     Turning now to  FIGS.  5  and  6   , in an embodiment of the invention, the disk cutter  100  comprises a circular cutter body  102  and a plurality of tool holders  104  arranged peripherally around the cutter body  102 . A single cutting element  106  is mounted in each tool holder  104 . Rotation of the drive spindle  16  causes a corresponding rotation of the disk cutter  100 . 
     To minimise the weight of the disk cutter  100 , panels have been removed from the cutter body  102  to leave apertures. These apertures extend through the thickness of the cutter body  102 . Removing several panels leaves spokes in-between apertures. Typically, these panels are removed by laser, though any form of machining could be used. The pattern of the apertures maintains structural strength whilst reducing the weight of the whole disk. Optimised strength to weight ratios for different applications can be achieved with different geometric designs. 
     In this embodiment, the cutter body  102  comprises five radial spokes  108  and five light-weighting apertures  110 , one aperture  110  between a pair of neighbouring spokes  108 . The spokes  108  are regularly spaced apart about a central shaft aperture  112 . However, the spokes  108  are off-set centrally and the cutter body  102  is asymmetric about its axis of rotation, the shaft aperture  112 . The breadth of the spokes  108  remains largely unchanged from the centre of the cutter body  102  towards a peripheral (or circumferential) surface  113  of the body  102 . Each aperture  110  is triangular with rounded corners. Two surfaces  114  of the triangular aperture  110  extend generally radially and a third surface  116  extends generally circumferentially. 
     The cutter body  102  has a diameter of approximately 421 mm and a thickness of 3 mm. The shaft aperture  112  has a diameter of 10 mm, and is sized and shaped to receive the drive spindle  16 . The cutter body  102  is made from aluminium alloy 7068 and weighs approximately 1.47 kg. Were the cutter body  102  to be made from steel, it would weigh approximately 2.58 kg. 
     In an alternative embodiment, the cutter body has a diameter of less than 500 mm. Preferably, the cutter body has a diameter of less than 500 mm. Preferably, the cutter body has a diameter of between 200 and 400 mm. 
     Turning now to  FIGS.  7  and  8   , twenty-four tool holders  104  are mounted to the cutter body  102 . Each tool holder  104  comprises a body portion  118  and a pair of spaced apart legs  120  extending from the body portion  118 . The proportion of the lengths of the body portion  118  to the pair of legs  120  is around 1:1. The body portion  118  hosts the cutting element  106 . The body portion  118  is generally cuboidal but the height starts to decrease mid-way from front to back to the tool holder  104 , such that a head  121  of the tool holder  104  slopes downwardly. The cutting element  106  is inserted into the front of the tool holder  104  at an angle such that the cutting element  106  points upwardly. Each leg  120  of the pair of legs is plate-like. The pair of legs  120  are spaced apart by a gap  122 , which enables coupling of the tool holder  104  either side of the cutter body  102 . A hole  124 , for receiving a bolt, extends through the pair of legs  120 . 
     The cutter body  102  comprises a plurality of slots  126 , positioned periodically along the peripheral surface  113  of the cutter body  102 , best seen in  FIGS.  11 ,  12  and  13   . When the tool holder  104  is mounted onto the cutter body  102 , the legs  120  pass either side of and adjacent to the cutter body  102  and each body portion  118  sits at least partially within the slot  126 . Each tool holder  104  is secured to the cutter body  102  with a nut and bolt (not shown). Alternatively, a permanent connection such as brazing or welding could be used. A mixture of brazing, welding and/or mechanical connections may also be used. Alternatively, the tool holder(s)  104  may be formed integrally with the cutter body  102 , for example, by forging, powder metallurgy etc. The slots  126  reduce the shear force on the bolts during use. By virtue of the peripheral surface  113  of the cutter body  102  extending between neighbouring slots  126 , tool holders  104  are regularly spaced apart around the cutter body  102 . 
     Each tool holder  104  is made from steel but may alternatively comprise any metal(s) or carbides or ceramic based materials with a hardness above 70 HV (Vickers Hardness). The tool holder  104  may comprise aluminium alloy and comprise the same material as the cutter body  104 . The tool holder  104  may comprise carbide, for example, tungsten carbide. 
     The tool holder in this embodiment has a thickness of approximately 8 mm. 
     Each cutting element  106  comprises a hard, wear resistant material with a hardness value of 130 HV and above. The cutting element  106  preferably comprises a superhard material selected from the group consisting of cubic boron nitride, diamond, diamond like material, or combinations thereof, but may be a hard material such as tungsten carbide instead. The cutting element  106  may comprise a cemented carbide substrate to which the superhard material is joined. 
     In  FIGS.  5  to  10   , the cutting elements  106  are polycrystalline diamond compacts (PDCs), more commonly found in the field of Oil and Gas drilling. Such PDCs are often cylindrical and usually comprise a diamond layer sinter joined to a steel or carbide substrate. The PDC has a diameter of between 6 mm and 30 mm, preferably between 8 mm and 25 mm. For example, the PDC may have a diameter of 6 mm, 11 mm, 12 mm, 13 mm, or 16 mm or 19 mm. In  FIGS.  5  to  8   , the PDC has a diameter of 6 mm. In the embodiment shown in  FIGS.  9  and  10   , the PDC has a diameter of 12 mm. A combination of diameters may be used in a disk cutter  100 . Each PDC may be chamfered, double chamfered or multiple chamfered. Each PDC may comprise a polished cutter surface, or be at least partially polished. 
     For a PDC with a dimeter of 11 mm, the preferred cutter body has a diameter of 400 mm and a thickness of 6 mm. Again, the cutter body preferably comprises aluminium alloy 7068. Twenty-four tool holders are used to support twenty-four PDCs. Each tool holder has a thickness of 13 mm. The shaft aperture is again 10 mm. The resulting weight of the disk cutter is approximately 2.48 Kg. Were the cutter body to be made from steel, the weight of the whole assembly would be approximately 4.51 Kg. 
     Optionally, the rake angle of the (PDC-type) cutting element is between 15 degrees and 30 degrees. Optionally, the rake angle is around 20 degrees. Optionally, the rake angle may be positive or negative.  FIG.  7    shows how the cutting element  106  protrudes from the tool holder  102 . 
     In rock excavation applications, the disk cutter  100  is brought into contact with the rock formation  2  and rotation of the drive spindle  16 , and therefore its disk cutter(s)  100 , causes slicing of the rock formation  2 . The cutting assembly  10  slices into the rock formation  2 , for example, to create clean orthogonal cuts of around 16 mm, depending on the size of the cutting elements  22  selected. The cut rock breakouts either under its own weight or with secondary wedge force, e.g. using a wedge-shaped tool. 
       FIGS.  11  to  13    depict an alternative form of cutter body  102 , which could be used in any combination with of the features described herein. In  FIGS.  12  and  13   , four panels have been removed from the body to leave four apertures. Similarly, in  FIGS.  5 ,  6 ,  11 ,  14  and  15   , five panels have been removed. Typically, these panels are removed by laser, though any form of machining could be used. The pattern of the apertures maintains structural strength whilst reducing the weight of the whole disk. Optimised strength to weight ratios for different applications can be achieved with different geometric designs. 
     Referring to  FIG.  11   , a second embodiment of the cutter body is indicated at  200 . The body comprises five radial spokes  202  and five light-weighting apertures  204 , one aperture  204  between a pair of neighbouring spokes  202 . The spokes  202  are regularly spaced apart and symmetrical about the central shaft aperture  112  that receives the drive spindle  16 . The spokes  202  taper circumferentially outwardly from the centre of the cutter body  200  towards the peripheral surface  113  of the body  200 . As a consequence, each aperture  204  is generally trapezoidal in shape, with a pair of arcuate inner and outer surfaces  206  and a pair of straight surfaces  208  adjoining the arcuate surfaces  206 . The arcuate surfaces  206  extend circumferentially, whereas the straight surfaces  208  extend radially. 
     In  FIG.  12   , a third embodiment of the cutter body is indicated at  300 . The body comprises four radial spokes  302  and four light-weighting apertures  304 , one aperture  304  between a pair of neighbouring spokes  302 . The spokes  302  are regularly spaced apart about the central shaft aperture  112 . However, the spokes  302  are off-set centrally and the body  300  is asymmetric about its axis of rotation, the shaft aperture  112 . The breadth of the spokes  302  remains largely unchanged from the centre of the body  300  towards the peripheral surface  113  of the body  300 . Each aperture  304  is a quadrilateral, with two adjoining surfaces  306  extending generally radially and an opposing pair of adjoining surfaces  308  extending generally circumferentially. 
     Referring to  FIG.  13   , a fourth embodiment of the cutter body is indicated at  400 . The body comprises four radial spokes  402  and four light-weighting apertures  404 , one aperture  404  between a pair of neighbouring spokes  402 . The spokes  402  are regularly spaced apart and symmetrical about the central shaft aperture  112  that receives the drive spindle  16 . The spokes  402  taper circumferentially outwardly from the centre of the body  400  towards the peripheral surface  113  of the body  400 . As such, each aperture  404  is generally trapezoidal in shape, with a pair of arcuate inner and outer surfaces  406  and a pair of straight surfaces  408  adjoining the arcuate surfaces  406 . The arcuate surfaces  406  extend circumferentially, whereas the straight surfaces  408  extend radially. 
     Rather than being a traditional PDC, the cutting element  106  may be a 3-D shaped cutter. A strike tip of the cutting element  106  may be conical, pyramidal, ballistic, chisel-shaped or hemi-spherical. The strike tip may be truncated with a planar apex, or non-truncated. The strike tip may be axisymmetric or asymmetric. Any shape of cutting element  106  could be used, in combination with any aspect of this invention. Examples of such shaped cutters can be found in WO 2014/049162 and WO 2013/092346. 
     In  FIGS.  14  and  15   , a second embodiment of a disk cutter is shown. The disk cutter  1000  comprises a generally circular cutter body  102  and a plurality of tool holders  1002  arranged peripherally around the circular body  20 . The cutter body  102  is the same as the cutter body of the first embodiment, and so a further description is omitted. 
     A single cutting element  1004  is coupled to each tool holder  1002 . The cutting element  1004  comprises a 3-D shaped cutter, best seen in  FIGS.  16  and  17   . The cutting element  1004  has a conical strike tip  1006 , which is truncated, joined to a carbide substrate  1008 . The strike tip  1006  comprises superhard material. A wide base of the cutting element  1004  is firmly seated within a recess of the tool holder  1002 , and a free end at the strike tip  1006  points in the intended direction of rotation of the disk cutter  1000 , in line with the plane of the cutter body  102 —see  FIG.  18   . The substrate  1008  is sat almost completely within the tool holder  1002  such that the strike tip  1006  projects out of the tool holder  1002 —see  FIG.  17   . In this way, the strike tip  1006  helps to reduce ‘bodywash’ (i.e. erosion) of the tool holder  1002  in use. 
     In a further embodiment, not shown, two cutting elements  1004  may be provided on the tool holder  1002 . These cutting elements  1004  are spaced apart. The two strike tips  1006  still point in the intended direction of rotation of the disk cutter  1000  but their direction is not in line with the plane of the cutter body  1000 . They each point outboard, in opposing directions, symmetrical about the plane of the cutter body  1000 . 
     The total mass of the disk cutter  1000  is less than 5 kg. 
     While this invention has been particularly shown and described with reference to embodiments, it will be understood by those skilled in the art that various changes in form and detail may be made without departing from the scope of the invention as defined by the appended claims. 
     For example, any embodiment of the cutter body  102 ,  200 ,  300 ,  400 , may be used in combination with a PDC cutting element  106  and/or with a 3-D shaped cutter  1004 . 
     For example, the two cutting elements each pointing outboard, in opposing directions, symmetrical about the plan of the cutter body may be PDCs rather than 3-D shaped cutting elements  1004 . 
     Certain standard terms and concepts as used herein are briefly explained below. 
     As used herein, polycrystalline diamond (PCD) material comprises a plurality of diamond grains, a substantial number of which are directly inter-bonded with each other and in which the content of the diamond is at least about 80 volume percent of the material. Interstices between the diamond grains may be substantially empty or they may be at least partly filled with a bulk filler material or they may be substantially empty. The bulk filler material may comprise sinter promotion material.