Mining method and apparatus

Abstract

 Method and apparatus for long wall mining are described in which a series of slots (12, 14) are cut into a face (10) at suitable angles, the slots (12, 14) intersecting to define a block (16). Portions are progressively separated from the block (16) e.g. by an impact hammer (38) which follows the cutters (32, 34). Conveniently at least one pair of inclined slots (12, 14) are produced simultaneously by using a pair of appropriately positioned cutters (32, 34), one of which follows immediately after the first so that the first and second slots (12, 14) are cut substantially simultaneously. The cutters are rotary diamond saws and the method allows mining of very hard material, for example gold bearing rocks, without the necessity to use blasting techniques.

Description

[0001] This invention is concerned with a method, winning machine and apparatus for mining, and especially for so-­called longwall mining.

[0002] In mining of hard rock, for example mining from gold bearing reefs, there has so far been little mechanisation due partly to the natural conditions encountered, including the extreme hardness of material being mined and difficulty of handling the environmental conditions at the enormous depths at which gold mining is commonly carried out. It is desirable to devise a method of mining such hard materials without the usual drilling and blasting operations which have commonly been used until now. Other methods have been proposed but none has been altogether satisfactory because of an inability to provide reliable bulk output under the demanding conditions, especially of severe roof pressures normally encountered in deep mines.

[0003] Longwall mining is a technique commonly used for mining coal, in which a winning machine traverses a long coal face, cutting the coat as it goes, the coal falling onto a conveyor for removal. It is common to use a rotatable cutting device having picks, known as a shearer drum, which breaks up the coal as it moves along the face.

[0004] The present invention provides a method of mining, and a winning machine and apparatus therefor, which may cut coal more efficiently and which can also be used for cutting harder materials, as in gold mines.

[0005] US-A-2390562 was published in 1945 and proposed a system of mining in which slots were cut into a coal face using a circular abrasive saw. The proposal did not relate to longwall mining, but was concerned with cutting a recess into a face to remove the coal. It was proposed to cut a series of slots which intersected, so that blocks of material fell from the face. It is believed that this proposal was never worked in the United States of America, or elsewhere.

[0006] The method described in US-A-2390562 is a slow process as compared with modern mining techniques, but it has the advantages of avoiding the use of explosives and reducing the amount of dust produced. Apart from this problem of the method being slow, the method will not work, where there is substantial pressure in the rock, due to the depth of the seam to be mined. This is because a slot being cut by a saw is thin and immediately starts to close up, so that the saw becomes trapped. This is probably the main reason that the method was never used commercially.

[0007] The present invention overcomes these problems and provides a method of mining material from a longwall mineral face wherein material is separated from the face by cutting intersecting first and second slots with a rotary cutting implement at an acute angle to the face, characterised in that the first and second slots are cut simultaneously by movement of first and second cutting implements longitudinally of the face and in that the first cutting implement is closely positioned adjacent the second cutting implement during such movement.

[0008] The invention also provides a mineral winning machine for mining material from a longwall mineral face comprising rotary cutting means operable to cut intersecting first and second slots in the face at acute angles thereto, characterised by drivable support means supporting the implements and adapted for movement along the face, in that the rotary cutting means comprises first and second rotary cutting implements mounted adjacent each other and inclined relative to each other, with their axes offset in the direction of movement of the support means whereby the implements simultaneously cut intersecting slots along the face.

[0009] Referring to the accompanying drawings:

Figure 1 is a diagrammatic side view showing one method embodying the invention;

Figure 2 is a further diagrammatic side view showing a second method embodying the invention;

Figure 3 is a perspective view of a severed block indicating the point at which a portion of the block may be separated;

Figures 4 to 6 are side views showing various stages in carrying out the method shown in Figure 2;

Figure 7 is a diagrammatic view of apparatus embodying the invention for carrying out a method embodying the invention;

Figure 8 is a front view of a further apparatus which may be used in carrying out the invention;

Figure 9 is a view of part of the apparatus shown in Figure 8;

Figure 10 is a plan view showing headers and face;

Figure 11 is a side view, with parts broken away for clarity, of a winning machine in an operative location; and

Figure 12 is a plan view of the machine as in Figure 11.

[0010] In Figure 1 is illustrated a method embodying the invention in which material is mined from a longwall face 10 by cutting first and second slots 12, 14 in the face 10, the slots 12, 14 being inclined at acute angles to the face and arranged to intersect one another. The slots 12, 14 are cut progressively in a longitudinal direction along the face 10, to form a block of material 16 (see also Figure 3) which extends along the face 10. Portions may separate from the block due to brittleness of the material. In Figure 3 the portion 18 is shown as being separated by an impact hammer which hits the block 16 at a region indicated by the reference 20.

[0011] The blocks may be separated by a suitable pneumatic or hydraulic impact hammer or by providing a third cut intersecting both the second and first cuts, e.g. in a vertical direction, whereby to separate the portion of the block.

[0012] In carrying out the first method, after the block 16 has been excavated holes 22 are bored in the face 10 above and below the part from which the block 16 has been removed, and the remainder of the material is blown from the face by suitable explosive charges placed in the holes 22. However, because this first method involves the use of explosives which is preferably avoided, the first method is not preferred.

[0013] In a second method embodying the invention shown diagrammatically in Figure 2, a plurality of intersecting cuts are made in a face 10, a first series of spaced parallel slots 12 being cut at an acute angle to face 10 and a second spaced parallel set of slots 14 being cut at a different angle to the face 10 to intersect the first slots, each of the second slots 14 intersecting an associated one of the first slots 12. In Figure 2 two of the sets of first and second slots are shown. It will be seen that at the top and bottom of the working, slots 26 are cut which are generally perpendicular to the face 10 at the top and bottom of the face to define the floor 28 and roof 30 of the working. All the cuts may be made simultaneously, or the cuts may be made in pairs, i.e. cutting simultaneously one pair of intersecting first and second slots in one traverse of the face and then cutting another pair in a return traverse.

[0014] In one method of mining by cutting a pattern of slots substantially as shown in Figure 1 or 2, a winning machine in accordance with the invention is used comprising cutting means 37 including first and second rotary diamond saw cutters 32, 34 mounted on a carriage 36 (see Figure 7).

[0015] As can be seen from Figure 4 the two cutters are inclined at an acute angle to the face 10 and the slots 12, 14 cut by them are arranged to intersect. As can be seen from Figure 7, the cutters 32, 34 are adjacent each other, but their axes are offset from one another longitudinally of the face 10 so that there is no clash when simultaneously cutting the slots. An impact hammer 38 is arranged to follow the cutters as they progress along the face 10 in the direction indicated by the arrow A (Figure 7) and separate portions of blocks 16 of material cut by the cutters 32, 34 from the face in a manner generally similar to that described with reference to Figure 3.

[0016] The cutters 32, 34 are first used to remove a substantially central block 16 disposed roughly midway between the roof 30 and floor 28 of the working and then to successively removed in successive passes along the face other blocks 16 in a second operation and a third operation. The cutters 32, are arranged to be adjustable in angle of cut so that for a fourth operation, the cutters 32 can be arranged to cut a perpendicular slot which defines the roof 30 and in the fifth operation, the cutters 34 can be adjusted to cut a slot which defines the floor 28. Depending on the height of the face a greater or lesser number of operations may be required and a greater or lesser number of blocks 16 cut.

[0017] In Figures 8 and 9 one suitable apparatus is shown for simultaneously cutting of several slots. The apparatus comprises cutting means 37 having two parallel cutters 34. Any desired number of parallel cutters may be provided to provide spaced parallel cuts and a further set of parallel cutters (not shown) inclined to the first set is provided to make the second slots simultaneously.

[0018] Each cutter may comprise a disc having a peripheral edge formed with saw teeth reinforced by diamond material.

[0019] The operation is started by first making recesses 40, 42 at opposite ends of the longwall face 10, such recesses being known as "stable holes". The cutters are positioned in one of these recesses at the start of an operation. The cutters are inclined at an angle "X" of about 60 to 70° to the face 10 as shown in Figure 4.

[0020] As previously mentioned, the portions may be broken off the block defined by the slots 12, 14 by impact hammers or other percussive tools hydraulically, pneumatically or electrically powered. Percussive tools are able to break off the portions of previously cut material, for example gold bearing rock, using relatively little power. The impact point of the tools may be positioned so that the portions of material separated are limited in length so that the conveyor clearing system can readily deal with them.

[0021] The apparatus shown in Figure 7 and Figures 8 and 9, includes a conveyor system of the type commonly known as a self-advancable armoured flexible conveyor 50 (Figure 9). In this type of system, a series of heavy duty steel trays, commonly referred to as pans, are pivotally connected together and the trays are connected at one end to a drive unit adjacent the junction of the face 10 and an access tunnel 40 and the other end to a return unit at the junction of the face 10 and the output tunnel 42. Conveying means is provided to transport the mined material along the line of pans to a secondary conveyor. The conveying means commonly comprises spaced bars which are moved along the line of pans by a driven chain assembly. Rams are provided to push the conveyor 50 forward as the face 10 retreats. The winning machine rides on the line of pans of the armoured flexible conveyor, the pans defining rails for the machine in known manner.

[0022] In trials, speeds of cutting of 0.75 metres to 1.0 metre per minute in limestone making a slot about 1.6 cms wide and about 46 cms deep were achieved. It is expected that by suitable selection of diamond cutters, speeds considerably in excess of this will be obtained and these may be further enhanced by use of other aids, for example pressure water jetting.

[0023] Where only one pair of cutters is to be used, the height of the cutters is adjustable to cut the blocks at the various heights up the coal face. Impact hammers may be provided at both sides of the cutters so that the trailing hammer, depending on the direction of movement of the machine, is used.

[0024] Referring to Figures 11 and 12 more detail of the construction of the equipment such as shown in Figures 9 and 10 is illustrated.

[0025] The winning machine comprises a frame 50, which rests on rails 51, 52 of a conveyor assembly. The rails extend longitudinally of the assembly at opposite sides thereof and a transverse plate 53 interconnects the rails. Conveying means 54 of any conventional form may move along the top of the plate to convey deposited mineral. The frame 50 is captivated on the rails by means of flanged members 55, 56 which engage beneath shoulders 57, 58 on the rails. The frame also includes a track 60 which receives headed member 61 on the conveyor for guiding the frame 50 along the rails.

[0026] A pair of main arms 70 are pivotally mounted on the frame 50 for adjustment about a common pivot axis 71 which extends longitudinally of the face 10. Each arm 70 is of H-form and a respective cutting head 72, 73 is pivotally mounted between the legs of the H for adjustment about axes 74, 75, parallel to the axis 71. Each cutting head comprises a motor 77, 78 and a rotary cutting blade 32, 34.

[0027] Each main arm 70 is held and is adjustable about the axis 71 by a respective hydraulic piston/cylinder unit 80, 81 mounted on the frame about a pivot axis 82 and pivotally connected to lugs 83, 84 on the main arms. Further hydraulic piston/cylinder units 85, 86 adjust the cutting heads relative to the main arms.

[0028] At the forward and rearward sides of the frame (along the direction of travel) hydraulic percussive tools 90, 91 are mounted. The tools are operated by hydraulic or pneumatic piston/cylinder units 92, 93. These tools are also pivotally mounted for adjustment along with the cutting heads.

[0029] Also mounted on the frame, and located between the conveyor assembly and the face 10, is a deflector 100.

[0030] In use, the winning machine rides along the face conveyor rails 51, 52 simultaneously cutting intersecting slots in the face 10. The following percussive tool 90 or 91 is operated to break up the block so formed. The mineral forms onto the deflector 100, which directs the mineral onto the face conveyor. The output from the face conveyor is deposited on an outbye conveyor 101 in the exit tunnel 102.

[0031] The roof adjacent the face is supported by a row of hydraulic props 103. The props have hydraulic rams 104 connected to the face conveyor assembly. The conveyor assembly can, thereby, be advanced by these rams as the face recedes. The hydraulic props are then advanced and rubble is packed behind the props. This arrangement is well known in coal mining.

Claims

1. A method of mining material from a longwall mineral face (10) wherein material is separated from the face by cutting intersecting first and second slots (12, 14) with a rotary cutting implement (32 or 34) at an acute angle to the face, characterised in that the first and second slots (12, 14) are cut simultaneously by movement of the first and second cutting implements (32, 34) longitudinally of the face and in that the first cutting implement is closely positioned adjacent the second cutting implement during such movement.

2. A method according to Claim 1 wherein a separating device (38) follows the cutting implements to break up the elongate block (16) formed by the cutting implements as the block is being formed.

3. A method according to Claim 1 or 2, wherein a plurality of intersecting first and second slots are cut simultaneously along the face.

4. A mineral winning machine for mining material from a longwall mineral face (10) comprising rotary cutting means (32) operable to cut intersecting first and second slots (12, 14) in the face at acute angles thereto, characterised by drivable support means (36) supporting the implements and adapted for movement along the face, in that the rotary cutting means comprises first and second rotary cutting implements (32, 34) mounted adjacent each other and inclined relative to each other, with their axes offset in the direction of movement of the support means whereby the implements simultaneously cut intersecting slots (12, 14) along the face.

5. A mineral winning machine according to Claim 4 wherein each cutting implement (32, 34) comprises a disc having a peripheral edge formed with saw teeth reinforced by diamond material.

6. A mineral winning machine according to Claim 4 or 5 comprising additional said first and second cutting implements mounted on the support to form a bank of such implements which cut slots along the face as the support is moved along the face.

7. Apparatus for mining material from a longwall mineral face including a winning machine according to Claim 4, 5 or 6 and separating means trailing said cutting implements and operable simultaneously therewith for breaking up the block or blocks of material formed by cutting of the intersecting slots.

8. Apparatus for mining mineral from a longwall face including a winning machine according to Claim 4, 5 or 6, or according to Claim 7, including a conveyor mounted along the face for removing mineral separated from the face, the support of the winning machine being located on the conveyor and drivable along the conveyor.

Drawing