Patent Publication Number: US-2011062768-A1

Title: Mining Machine and Method of Mining

Description:
The present invention relates to a mining machine. In particular, the invention relates to a method of mining and to a mining machine. 
     BACKGROUND OF THE INVENTION 
     It has been recognized for many years that mining machines greatly improve productivity in underground mines. For this purpose, continuous mining machines were developed fin particular for usage in coal mines. These mining machines utilize rotating teeth-faced drums or rotating borer heads that scrape coal from the seam. 
     The inventors are aware of mining machines which date back to the early years of 1940. In U.S. Pat. No. 2,565,528 one particular example of such an early prior art mining machine is described. 
     Another mining machine is shown in U.S. Pat. No. 4,669,560. A continuous mining machine is described having an elongated conveyor assembly for continuously conveying coal cut from a coal seam rearwardly away from the face of the coal seam being cut having a frame structure associated therewith. A power driven cutting assembly is disposed forwardly with respect to the frame structure for cutting coal from the coal seam for conveyance rearwardly by the conveyor assembly. 
     A problem associated with this known prior art machine is that often the walls of the seam are not evenly scraped, as for example illustrated in  FIG. 1  of the above disclosure. 
     Another mining machine is shown in U.S. Pat. No. 3,197,256. There, a borer type cutting head is used in order to cut the coal from the seam. A problem associated with this known prior art machine is that the machine experience large forces on the drum which have to be counter balanced by suitable anchoring of the machine to the ground. 
     A further example of mining machines is described in U.S. Pat. No. 5,871,260. A continuous mining machine is provided for mining ultra thin coal seams, e.g. seams having a thickness of about 24 inches or less. A chassis supported by crawler tracks has a substantially horizontal axis powered cutter head mounted to its front and a conveyor extending from a gathering head toward the rear of the chassis. The conveyor includes a conveyor chain driven by at least one motor near the rear of the chassis for driving a sprocket. 
     Other mining machines are described in U.S. Pat. No. 4,341,424 and U.S. Pat. No. 4,037,875. 
     What is ideally required is a mining machine and/or a method of mining which is not only easier to operate but offers more even scrapping of the mine&#39;s seam. 
     OBJECTS OF THE INVENTION 
     It is an object of the present invention to provide a mining machine and a method of mining which overcomes, at least partly, the disadvantages associated with the state of the art mining machines. 
     It is also an object of the present invention to provide a new mining machine and a method of mining involving an inventive step. 
     SUMMARY OF THE INVENTION 
     According to a first aspect of the invention, there is provided a method of mining, the method including:
         providing a mining machine defining a body, an arm mounted on the body for angular displacement relative to the body and a mining head mounted on an end region of the arm for rotation relative to the end region;   advancing the mining machine such that the mining head abuts against a mining face;   driving the mining head to rotate relative to the end region of the arm while the mining head is in abutment with the mining face; and   driving the arm to displace angularly relative to the body to sweep the mining head across the mining face while the mining head is driven to rotate and in abutment with the mining face, thereby to mine the mining face.       

     The arm may be mounted on the body for generally horizontal angular displacement relative to the body, driving the arm to displace angularly relative to the body to sweep the mining head across the mining face then including driving the arm to displace angularly relative to the body to sweep the mining head generally horizontally across the mining face. 
     The mining machine may define anchor means for anchoring the arm relative to the mining face as the arm is driven to displace angularly relative to the body to sweep the mining head across the mining face, the method then including anchoring the arm relative to the mining face, by means of the anchor means, as the arm is driven to displace angularly relative to the body to sweep the mining head across the mining face. 
     The arm may be mounted on the body for angular displacement relative to the body about a pivot, anchoring the arm relative to the mining face, by means of the anchor means, as the arm is driven to displace angularly relative to the body to sweep the mining head across the mining face then including anchoring the pivot relative to the mining face. 
     The anchor means may include a prop formation, anchoring the pivot relative to the mining face then including actuating the prop formation to cause the prop formation to prop the pivot between a roof of the mine and a floor of the mine thereby to anchor the arm relative to the mining face. 
     The prop formation may define a prop axis, driving the arm to displace angularly relative to the body then including driving the arm to displace angularly relative to the body about the prop axis. 
     The arm may define a wrist portion positioned between the mining head and the rest of the arm, the wrist portion being angularly displaceably mounted on the arm, the method including driving the arm to displace angularly relative to the body to sweep the mining head across the mining face to perform successive sweeping strokes across the mining face and driving the wrist portion to displace angularly relative to the rest of the arm between successive sweeping strokes. 
     The wrist portion may be mounted on the rest of the arm for generally horizontal angular displacement relative to the rest of the arm, driving the wrist portion to displace angularly relative to the rest of the arm between successive sweeping strokes then including driving the arm to displace angularly relative to the rest of the arm in a generally horizontal direction between successive sweeping strokes. 
     The arm may be mounted on the body for angular displacement relative to the body in a generally vertically extending direction, the method including driving the arm to displace angularly in the generally vertically extending direction between successive sweeping strokes. 
     The wrist portion may be mounted on the rest of the arm for angular displacement relative to the rest of the arm in a generally vertically extending direction, the method including driving the wrist portion to displace angularly in the generally vertically extending direction relative to the rest of the arm between successive sweeping strokes. 
     The mining head may be generally elongate drum shaped defining a longitudinally extending axis of rotation, driving the mining head to rotate relative to the end region of the arm while the mining head is in abutment with the mining face then including driving the generally elongate drum shaped mining head to rotate about the longitudinally extending axis of rotation. 
     The generally elongate drum shaped mining head may be mounted on the end region of the arm such that the longitudinally extending axis of rotation extends generally horizontally, driving the mining head to rotate relative to the end region of the arm while the mining head is in abutment with the mining face then including driving the mining head to rotate about the generally horizontal longitudinally extending axis of rotation. 
     The generally elongate drum shaped mining head may define opposed generally truncated cone shaped portions, driving the arm to displace angularly relative to the body to sweep the mining head across the mining face to perform successive sweeping strokes across the mining face and driving the wrist portion to displace angularly relative to the rest of the arm between successive sweeping strokes then including causing the opposed generally truncated cone shaped portions alternately to abut against the mining face between successive sweeping strokes. 
     According to another aspect of the invention, there is provided a mining machine including:
         a body;   an arm mounted on the body for angular displacement relative to the body;   a mining head mounted on an end region of the arm for rotation relative to the end region of the arm;   drive means for driving the mining head to rotate relative to the end region of the arm while the mining head is in abutment with a mining face; and   drive means for driving the arm to displace angularly relative to the body, such that, in use, the arm can be driven to displace angularly relative to the body to sweep the mining head across a mining face while the mining head is driven to rotate and in abutment with the mining face, thereby to mine the mining face.       

     The arm may be mounted on the body for generally horizontal angular displacement relative to the body. 
     The mining machine may define anchor means for anchoring the arm relative to a mining face when the arm is driven to displace angularly relative to the body to sweep the mining head across a mining face. 
     The anchor means may include a prop formation arranged to prop the mining machine between a roof of a mine and a floor of a mine thereby to anchor the arm relative to a mining face. 
     The prop formation may be displaceably mounted to the rest of the mining machine to be displaceable between a deployed condition, in which the prop formation is extended, and a collapsed condition, in which the prop formation is retracted. 
     The mining machine may include drive means for selectively driving the prop formation to displace between the deployed condition and the retracted condition. 
     The prop formation may define a prop axis. 
     The arm may be mounted on the body to be angularly displaceable relative to the body about the prop axis. 
     The arm may define a wrist portion positioned between the mining head and the rest of the arm, the wrist portion being angularly displaceably mounted on the rest of the arm. 
     The wrist portion may be mounted on the rest of the arm for generally horizontal angular displacement relative to the rest of the arm. 
     The mining machine may define drive means for driving the wrist portion to displace angularly relative to the rest of the arm. 
     The arm may be mounted on the body for angular displacement relative to the body in a generally vertically extending direction. 
     The mining machine may define drive means for driving the arm to displace angularly in the generally vertically extending direction. 
     The wrist portion may be mounted on the rest of the arm for angular displacement relative to the rest of the arm in a generally vertically extending direction. 
     The mining machine may define drive means for driving the wrist portion to displace angularly in the generally vertically extending direction relative to the rest of the arm. 
     The mining head may be generally elongate drum shaped. 
     The mining head may define a longitudinally extending axis of rotation. 
     The drive means for driving the mining head to rotate relative to the end region of the arm may be arranged to drive the mining head to rotate about the longitudinally extending axis of rotation. 
     The generally elongate drum shaped mining head may be mounted on the end region of the arm such that the longitudinally extending axis of rotation extends generally horizontally. 
     The generally elongate drum shaped mining head may define opposed generally truncated cone shaped portions. 
     Mining elements may be provided to extend across an outer surface of the elongate drum shaped mining head. 
     The mining elements may be in the form of mining picks. 
     The mining machine may further include mined material removal means for removing mined material from a mining face. 
     The mined material removal means may include an auger. 
     The mining material removal means may further include an arm on which the mined material removal means is mounted. 
     The arm may be angularly displaceably mounted on the body to be displaceable between a mined material removal position, in which the arm is extended relative to the body and the mined material removal means is in a position for removing mined material from a mining face, and a retracted position, in which the arm is retracted toward the body. 
     The mining machine may include two opposed arms on each of which mining material removal means is mounted, the arms being displaceably mounted on the body to be displaceable between mined material removal positions, in which the arms are extended relative to the body and the mined material removal means are in positions for removing mined material from a mining face, and retracted positions, in which the arms are retracted toward the body. 
     The mining machine may include a cartridge for carrying operating means or moving means of the mining machine, the cartridge being retractably mounted at an end opposite to the mining means. 
     The cartridge may include fastening means for retracting the cartridge. 
     According to another aspect of the invention, there is provided a mining vehicle being capable of carrying the mining machine according to the invention. 
     The mining vehicle may comprise a cartridge for carrying the operating means or moving means of the mining machine, the cartridge being retractably mounted at an end opposite to the mining means. 
     The cartridge may include fastening means for retracting the cartridge. 
     DETAILED DESCRIPTION OF THE INVENTION 
     The invention will now be described, by way of non-limiting example and drawings. The different embodiments of the invention are now further illustrated with reference to the following drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the accompanying diagrammatic drawings: 
         FIG. 1  shows a schematic plan view of a major part of a mining machine in accordance with an embodiment of the invention; 
         FIG. 2  shows a part sectional side view of the mining machine shown in  FIG. 1  of the drawings; 
         FIG. 3  shows a schematic side view of the mining machine shown in  FIGS. 1 and 2  of the drawings, a prop formation of the mining machine being in a deployed condition and an arm of the mining machine being shown in a lifted condition, in which the arm is angularly displaced relative to the body in a generally vertically extending direction; 
         FIG. 4  corresponds with  FIG. 3  of the drawings, the prop formation of the mining machine being in a collapsed condition and the arm of the mining machine being in a lowered condition; 
         FIG. 5  shows a schematic plan view of the mining machine shown in  FIGS. 1 to 4  of the drawings, the arm of the mining machine being in an initial position to displace angularly relative to a body of the mining machine so as to sweep a mining head of the mining machine across a mining face while the mining head is driven to rotate and is in abutment with the mining face, thereby to mine the mining face; 
         FIG. 6  shows a schematic plan view of the arm, the mining head having been displaced angularly relative to the arm; 
         FIG. 7  shows a schematic plan view of the arm and shows the arm being displaced angularly relative to the body of the mining machine so as to sweep the mining head of the mining machine across a mining face; 
         FIG. 8  shows a schematic plan view of the arm after the arm has been displaced angularly relative to the body of the mining machine and after the mining head of the mining machine has been swept across a mining face; and 
         FIG. 9  shows a schematic plan view of the mining machine, and indicates the operation of mined material removal means of the mining machine; 
         FIG. 10  shows a part sectional side view of a mining vehicle carrying the mining machine shown in  FIG. 1  of the drawings; 
         FIG. 11  shows a schematic plan view of the mining machine, and indicates the operation of mined material removal means of the mining machine; 
         FIG. 12  shows a schematic front view of the mining machine, and indicates the operation of mined material removal means of the mining machine; and 
         FIG. 13  shows a schematic front view of the mining machine, and indicates the operation of mined material removal means of the mining machine. 
     
    
    
     In all drawings, like reference numerals refer to like parts, unless otherwise indicated. 
     Referring to  FIGS. 1 to 4  of the drawings, a mining machine, in accordance with an embodiment of the invention, is generally indicated by reference numeral  10 . 
     The mining machine  10  includes a body  12 . An arm  14  is mounted on the body  12  for angular displacement relative to the body  12 , as indicated by arrows AA in  FIG. 1  of the drawings. The arm  14  is mounted on the body  12  for generally horizontal angular displacement relative to the body  12 . A mining head  16  is mounted on an end region  14 . 1  of the arm  14  for rotation relative to the end region  14 . 1  of the arm  14 , as indicated by arrow B in  FIG. 2  of the drawings. 
     Drive means for driving the mining head  16  to rotate relative to the end region  14 . 1  of the arm  14 , is generally indicated by reference numeral  18 . The mining head  16  is driven to rotate while the mining head  16  is in abutment with a mining face, so as to perform a mining operation against the mining face. The drive means  18  can include, an electric motor, a hydraulic motor, or the like, for example. The drive means  18  can be positioned at any appropriate position, such as on the body  12 , on the arm  14 , or the like, for example. 
     The mining head  16  is generally elongate drum shaped. The mining head  16  defines a longitudinally extending axis of rotation  16 . 1 . The drive means for driving the mining head  16  to rotate relative to the end region  14 . 1  of the arm  14  is arranged to drive the mining head  16  to rotate about the longitudinally extending axis of rotation  16 . 1 . 
     The generally elongate drum shaped mining head  16  is mounted on the end region  14 . 1  of the arm  14  such that the longitudinally extending axis of rotation  16 . 1  extends generally horizontally. 
     The generally elongate drum shaped mining head  16  defines opposed generally truncated cone shaped head portions  16 . 2 ,  16 . 3 . It will be appreciated that, instead of the opposed generally truncated cone shaped head portions  16 . 2 ,  16 . 3 , opposed generally barrel shaped portions, or opposed generally cylindrically shaped portions, or the like, for example, can be used. Mining elements  16 . 4  are provided to extend across an outer surface of the elongate drum shaped mining head  16 . Typically, the mining elements  16 . 4  are in the form of mining picks. 
     In use, the arm  14  is driven to displace angularly relative to the body  12 , as indicated by arrows AA, to sweep the mining head  16  across a mining face while the mining head  16  is driven to rotate and in abutment with the mining face, thereby to mine the mining face. 
     Drive means for driving the arm  14  to displace angularly relative to the body  12 , as indicated by arrows AA, is generally indicated by reference numeral  20 . The drive means  20  can include, an electric motor, a hydraulic motor, or the like, for example. Typically, the drive means  20  is positioned on the body  12 . 
     It will be appreciated that the drive means  18 ,  20  can include corresponding transmission components, such as, gears, chains, hydraulic conduits, hydraulic pumps, or the like, for example. 
     The mining machine  10  further includes anchor means, generally indicated by reference numeral  22 , for anchoring the arm  14  relative to a mining face when the arm  14  is driven to displace angularly relative to the body  12  to sweep the mining head  16  across a mining face. The anchor means  22  includes a prop formation  24  arranged to prop, or wedge, the mining machine  10  between a roof of a mine and a floor of a mine thereby to anchor the arm  14  relative to a mining face. The prop formation  22  is displaceably mounted on the rest of the mining machine  10  to be displaceable between a deployed condition, in which the prop formation  22  is extended, as can best be seen with reference to  FIG. 3  of the drawings, and a collapsed condition, in which the prop formation  22  is retracted, as can best be seen with reference to  FIGS. 1 and 2  of the drawings. The mining machine  10  includes drive means, generally indicated by reference numeral  24 , for selectively driving the prop formation  22  to displace between the deployed condition and the retracted condition, as indicated by arrows CC in  FIG. 3 . The drive means  24  can include an electric motor, a hydraulic motor, or the like, for example, and corresponding transmission components, such as, gears, chains, hydraulic conduits, hydraulic pumps, or the like, for example. 
     The arm  14  is mounted on the body  12  for angular displacement relative to the body  12  about a pivot  27 . The anchor means  22  is arranged to anchor the arm  14  relative to the mining face  40  at the pivot  27 , thereby to anchor the arm  14  relative to the mining face  40 . Accordingly, when the prop formation  22  is actuated the prop formation  22  props the pivot  27  between a roof of the mine and a floor of the mine thereby to anchor the arm  12  relative to the mining face  40 . 
     The prop formation  22  defines a prop axis  26 . Advantageously, the arm  14  is mounted on the body  12  to be angularly displaceable relative to the body  12  about the prop axis  26 . Accordingly, an axis  25  of angular displacement of the arm  14  is coaxial with the prop axis  26 . 
     By mounting the arm  14  on the body  12  such that the arm  14  is anchored at the pivot  27 , the rest of the mining machine  10  other than the arm  14 , is relatively isolated from stresses and strains during a mining operation. 
     The arm  14  defines a wrist portion  14 . 2  positioned between the mining head  16  and the rest of the arm  14 . The wrist portion  14 . 2  is angularly displaceably mounted on the rest of the arm  14 , as indicated by arrows DD, as can best be seen with reference to  FIG. 1  of the drawings. The wrist portion  14 . 2  is mounted on the rest of the arm  14  for generally horizontal angular displacement relative to the rest of the arm  14 , as indicated by arrows DD. Drive means for driving the wrist portion  14 . 2  to displace angularly relative to the rest of the arm  14  is provided, as indicated generally by reference numeral  28 . The drive means  28  can include an electric motor, a hydraulic motor, or the like, for example, and corresponding transmission components, such as, gears, chains, hydraulic conduits, hydraulic pumps, or the like, for example. 
     The arm  14  is mounted on the body  12  for angular displacement relative to the body  12  in a generally vertically extending direction, as indicated by arrows EE, as can best be seen with reference to  FIGS. 3 and 4  of the drawings. Drive means for driving the arm  14  to displace angularly in the generally vertically extending direction, as indicated by arrows EE, is generally indicated by reference numeral  30 . The drive means  30  can include an electric motor, a hydraulic motor, or the like, for example, and corresponding transmission components, such as, gears, chains, hydraulic conduits, hydraulic pumps, or the like, for example. Conveniently, the arm  14  is mounted on the body  12  for angular displacement relative to the body  12  in the generally vertically extending direction, as indicated by arrows EE, by means of a parallelogram type linkage generally indicated by reference numeral  32 . 
     The wrist portion  14 . 2  is mounted on the rest of the arm  14  for angular displacement relative to the rest of the arm  14  in a generally vertically extending direction, as can best be seen with reference to  FIGS. 3 and 4  of the drawings and as indicated by arrows FF. The wrist portion  14 . 2  is caused to displace angularly relative to the rest of the arm  14  automatically by means of the parallelogram type linkage  32  in response to the drive means  30  driving the arm  14  to displace angularly in the generally vertically extending direction, as indicated by arrows EE. 
     Instead of a parallelogram type linkage  32 , a rigid arm can be used. In such a case, drive means can be provided for driving the wrist portion  14 . 2  to displace angularly in a generally vertically extending direction relative to the rest of the arm  14 . 
     The mining machine  10  further includes mined material removal means, generally indicated by reference numeral  50 , for removing mined material from a face of a mine. The mined material removal means  50  includes an auger  52 . The auger  52  is mounted for rotation on an arm  54 . The arm  54  is angularly displaceably mounted on the body  12  to be displaceable between a mined material removal position, in which the auger  52  can be driven to rotate to remove mined material from the face of a mine, and a retracted position, as indicated in  FIG. 1  of the drawings. Typically, as can best be seen with reference to  FIG. 9  of the drawings, the mining machine  10  includes two opposed arms  54 . 1 ,  54 . 2  on each of which an auger  52 . 1 ,  52 . 2  is mounted for rotation. The arms  54 . 1 ,  54 . 2  are displaceably mounted on the body  12  to be displaceable between mined material removal positions, in which the arms  54 . 1 ,  54 . 2  are extended relative to the body  12  and angularly displaced away from one another as indicated in solid lines in  FIG. 9 , in which the mined material removal means  50  are in positions for removing mined material from a mining face, and retracted positions, in which the arms  54 . 1 ,  54 . 2  are angularly displaced toward one another and retracted toward the body  12 , as indicated in dashed lines in  FIG. 9 . In the retracted positions, the arms  54 . 1 ,  54 . 2  are positioned in a snug position adjacent the body  12  to render the mining machine  10  more maneuverable in a mine when the mined material removal means  50  is not in use. The arms  54 . 1 ,  54 . 2  can have wheeled formations at free ends for rollingly engaging a floor of a mine when angularly displaced relative to the body  12 . The wheeled formations can define driven wheels, or free rotating wheels. 
     It will be appreciated that a scraper, or scraper chain, or the like, for example, can be provided instead of, or in addition to, the augers  52 . 1 ,  52 . 2 . 
     In use, the mining machine  10  can be used in a method of mining, in accordance with another aspect of the invention, as will now be described with reference to  FIGS. 5 to 9  of the drawings, in which like reference numerals have been used to designate similar parts, or features, unless otherwise stated. 
     In accordance with the method, the mining machine  10  is advanced such that the mining head  16  abuts against a mining face, as indicated by reference numeral  40 , in  FIG. 5  of the drawings. The wrist portion  14 . 2  is displaced angularly in a generally horizontal plane relative to the rest of the arm  14 , as indicated by arrow D in  FIG. 5  of the drawings, such that a trailing one of the truncated cone shaped head portions, in this case the one indicated by reference numeral  16 . 3 , engages the mining face  40 , as can best be seen with reference to  FIG. 6  of the drawings. The mining head  16  is driven to rotate relative to the end region  14 . 1  of the arm  14  while the mining head  16  is in abutment with the mining face  40 . 
     The anchor means is actuated to anchor the arm  14  relative to the mining face  40 . In consequence, the prop formation  24  is displaced from the collapsed condition, as can best be seen with reference to  FIG. 4  of the drawings, into the deployed condition, as can best be seen with reference to  FIG. 3  of the drawings. When in the deployed condition, the prop formation  24  props, or wedges, the mining machine  10  between a roof of the mine and a floor of a mine thereby to anchor the arm  14  relative to a mining face  40 . 
     As can best be seen with reference to  FIG. 7  of the drawings, and as indicated by arrow A, the arm  14  is then driven to displace angularly relative to the body  12 , in a generally horizontal plane, to sweep the mining head  16  across the mining face  40  while the mining head  16  is driven to rotate and in abutment with the mining face  40 . In this way the mining face  40  is mined. The arm  14  is driven to displace angularly relative to the body  12  about the prop axis  26 . Typically, the arm  14  is driven to displace angularly relative to the body  12  about the prop axis  26  by about 140°. 
     After the arm  14  has been driven to displace angularly relative to the body  12  to sweep the mining head  16  across the mining face  40 , as indicated by arrow A, so as to be positioned as indicated in dashed lines in  FIG. 7  of the drawings, the arm  14  is driven to displace angularly relative to the body  12  in a generally vertically extending direction, as can best be seen with reference to  FIGS. 3 and 4  of the drawings as indicated by arrows EE. At generally the same time, the wrist portion  14 . 2  is driven to displace angularly in the generally vertically extending direction relative to the rest of the arm  14 , as can best be seen with reference to  FIGS. 3 and 4  of the drawings as indicated by arrows FF. In this way, the position of the mining head  16  is raised or lowered relative to the body  12 . It will be appreciated that the mining head  16  is raised or lowered relative to the body  12  in this way while being driven to rotate, thereby to mine the mining face  40  while being raised or lowered relative to the body  12 . 
     The wrist portion  14 . 2  is then displaced angularly in a generally horizontal plane relative to the rest of the arm  14 , as indicated by the dashed arrow D in  FIG. 7  of the drawings, such that a trailing one of the truncated cone shaped head portions, in this case the one indicated by reference numeral  16 . 2 , engages the mining face  40 , as can best be seen with reference to  FIG. 8  of the drawings. Typically, the wrist portion  14 . 2  is driven to displace angularly relative to the rest of the arm  14  by about 20°. 
     As can best be seen with reference to  FIG. 8  of the drawings, and as indicated by arrow A, the arm  14  is then driven to displace angularly relative to the body  12 , in a generally horizontal plane, to sweep the mining head  16  across the mining face  40  while the mining head  16  is driven to rotate and in abutment with the mining face  40 . In this way the mining head performs another sweep across the mining face, this sweep being above or below the prior sweep. Accordingly, the mining head  16  is driven across the mining face  40  to perform successive sweeping strokes across the mining face  40 , one above the other, and the wrist portion  14 . 2  is driven to displace angularly relative to the rest of the arm  14  between successive sweeping strokes and the mining head  16  is raised or lowered relative to the body  12  between successive sweeping strokes. 
     After the successive sweeping strokes have been performed, the prop formation  24  is displaced from the deployed condition, as can best be seen with reference to  FIG. 3  of the drawings, into the collapsed condition, as can best be seen with reference to  FIG. 4  of the drawings. The mining machine  10  is then advanced closer to the mining face  40  and the process is repeated. 
     The mining machine  10  can be mounted on a mining vehicle, part of which is schematically indicated in dashed lines at  51  in  FIG. 1  of the drawings. The mining vehicle is then used to advance the mining machine  10  closer to the mining face  40  to repeat the process. Instead, the mining machine  10  can be self propelled to advance closer to the mining face  40  to repeat the process. 
     As can best be seen with reference to  FIG. 3  of the drawings, the mining machine  10  can be provided with opposed apertures  55  and opposed piston and cylinder assemblies  57 . Only one of each aperture  55  and piston and cylinder assembly  57  is shown, the opposed aperture and the opposed piston and cylinder assembly being positioned behind the aperture  55  and the piston and cylinder assembly  57  shown in  FIG. 3 . Typically, the mining machine  10  can be mounted on a mining vehicle so as to be angularly displaceable about the apertures  55  which then serve to define opposed pivots. The piston and cylinder assemblies  57  are connected to the mining vehicle to enable the mining machine  10  to displace angularly relative to the mining vehicle about the pivots then defined at the apertures  55 , as indicated by arrows II. By angularly displacing the mining machine  10  relative to the mining vehicle about the pivots at  55  in this way, the inclination of the mining machine  10  relative to the mining vehicle can be varied. Accordingly, the inclination can be varied when it is desired to mine at an angle or when it is desired to move, or manoeuvre, the mining machine  10 . 
     The arm  14  can be radially outwardly extendable relative to the pivot  27  so that a to and fro mining sweep operation can be performed as described above and the arm  14  can then be extended to repeat the process. Then, only after an end of a range of the arm  14  has been reached, is the prop formation displaced into the collapsed condition and the mining machine  10  is advanced closer to the mining face  40  to repeat the process. 
     During such a mining operation, the mined material removal means  50  can be actuated periodically to remove mined material from the mining face  40 . This is achieved by displacing the arms  54 . 1 ,  54 . 2  from the retracted positions into the mined material removal positions and driving the augers  52 . 1 ,  52 . 2  to rotate. The arm  14  when performing a sweep while in a lower position serves to displace mined material toward the augers  52 . 1 ,  52 . 2 , as indicated schematically at  53  in  FIG. 5  of the drawings. When the mining machine  10  is then advanced toward the mining face  40  to perform another mining sweep operation, the augers  52 . 1 ,  52 . 2  advance across the mined material after the mined material has been displaced toward the augers  52 . 1 ,  52 . 2  during a previous mining sweep operation. In this way, the arm  14  serves as a scraper to enable mined material readily to be removed from the mining face  40  by the augers  52 . 1 ,  52 . 2 . 
     Making now reference to  FIG. 10 , an embodiment of the invention is shown wherein the mining machine  10  is mounted on a mining vehicle  60 . It should be noted that part of the mining vehicle  60  is schematically indicated in dashed lines at  51  in  FIG. 1  of the drawings. The mining vehicle  60  is used to advance the mining machine  10  closer to the mining face  40  to repeat the process. 
     As shown in  FIG. 10 , the mining vehicle  60  includes a main frame  62 . The main frame  62  includes a support structure  64  which is capable of accommodating the mining machine  10 . Furthermore, a pair of crawlers  66  is present so as to advance the mining machine  10  closer to the mining face  40  when in operation. Furthermore, the mining vehicle  60  includes a cartridge  68  for carrying operating means  70  or moving means  72  of the mining vehicle  60 . Operating means  70  can be operated by an operator an allow controlling the mining vehicle  60 . Moving means  72  can be a motor, which is operatively connected to the pair of crawlers  66  so as to advance the mining machine  10  closer to the mining face  40 . 
     The cartridge  68  is retractably mounted at an end opposite to the mining means. In order to enhance maintenance operations of the mining vehicle  60 , the cartridge  68  includes fastening means  74  for retracting the cartridge. Fastening means  74  can be provided in the form of a hook, for example. Retracting the cartridge can also be helpful during a break-down of the mining vehicle  60  because most of the parts of the mining vehicle  60  become accessible for repair. 
     In another embodiment (not explicitly shown in  FIG. 10 ), the mining machine  10  is self propelled to advance closer to the mining face  40  during the mining process. It is also conceivable that operating means  70  and the moving means  72  are mounted in the retractable cartridge  68 . 
     Making now reference to  FIG. 11 , operation of the mining machine  10  is shown in a top view. The mining machine  10  is advanced such that the mining head  16  abuts against the mining face, as indicated by reference numeral  40 , in  FIG. 11  of the drawings. The mining head  16  is driven to rotate relative to the end region  14 . 1  of the arm  14  while the mining head  16  is in abutment with the mining face  40 . During such a mining operation, mined material from the mining face  40  is periodically removed by displacing the arms  54 . 1 ,  54 . 2  from the retracted positions into the mined material removal positions and driving the augers  52 . 1 ,  52 . 2  to rotate. Furthermore, nozzles  80  are present on both sides of the end region  14 . 1  of the arm  14 . While the mining head  16  is mining the mining face  40 , water streams  82  from the nozzles  80  are used to bind coal dust during operation of the mining machine  10 . The mining machine  10  generally achieves a circular shaped mining face  40 , when viewed from above, as depicted in  FIG. 11 . 
     Making now reference to  FIG. 12 , operation of the mining machine  10  during the lower sweep of the mining head  16  is shown in a schematic front view. The front view of  FIG. 12  follows the line FF, as indicated in  FIG. 11 . As can be seen from  FIG. 12 , the mining head  16  achieves an arc shaped cross section of the mining face  40  during mining. 
     In one example, the width  90  of the mining face  40  can be 7 m. The height  92  of the mining face  40  can be 0.8 m in the lower sweep. The distance  94  of the arms  54  to the top of mining face  40  can be below 0.30 m while the end tips of the arms  54  are located at a distance  96  below 0.5 m from the mining face. 
     Making now reference to  FIG. 13 , operation of the mining machine  10  during the upper sweep of the mining head  16  is shown in a schematic front view. The front view of  FIG. 12  follows the line FF, as indicated in  FIG. 11 . 
     In one example, the width  90  of the mining face  40  can be 7 m. The height  92  of the mining face  40  can be 1.2 m in the upper sweep. The distance  94  of the arms  54  to the top of mining face  40  can be below 0.70 m. When the prop formation  22  is actuated the prop formation  22  props the pivot  27  between the roof of the mine and the floor of the mine thereby to anchor the arm  12  relative to the mining face  40 . The prop formation  22  is covering a distance  98  of approximately 0.4 m between the mining machine  10  and the roof of the mining face  40 . 
     It should be noted that the above example is merely illustrative to indicate the dimensions of the mining machine  10 . The mining machine  10  can be adapted for other dimensions, depending upon the specific requirements in an underground mine. 
     As can be seen from  FIGS. 12 and 13 , the mining head  16  achieves an arc shaped cross section of the mining face  40  during mining. Accordingly, the walls of the seam, i.e. the mining face  40 , are evenly scraped, which greatly reduces the risk of coal dust induced explosions. 
     Although certain embodiments only of the invention have been described herein, it will be understood by any person skilled in the art that other modifications, variations, and possibilities of the invention are possible. Such modifications, variations and possibilities are therefore to be considered as falling within the spirit and scope of the invention and hence forming part of the invention as herein described and/or exemplified. 
     This invention having been described in its preferred embodiment, it is clear that it is susceptible to numerous modifications and embodiments within the ability of those skilled in the art and without the exercise of the inventive faculty. Accordingly, the scope of the invention is defined by the scope of the following claims.