GB2228755A - Mining machine with roof support apparatus - Google Patents

Abstract

A continuous mining machine consists of a mobile frame (13) and a forward sub-frame (12) moveable relative thereto. Pivotally mounted on the sub-frame (12) is a jib (15) which carries a horizontal cutter (14, 16, 17) extending across the full width of the machine. The machine also includes a roof support installer (11) and a conveyor (36) for removing mined material to the rear of machine. Preferably a floor-plate is provided on the sub-frame. The machine is operated by sumping the cutter into the mine face at floor level and raising the jib relative to the sub-frame until it reaches roof level. Reaction forces from this cutting operation act downwards on the sub-frame, preferably through the optional floor-plate, and help to stabilise the machine, enabling simultaneous installation of roof bolts or other supports. <IMAGE>

Description

IMPROVEMENTS IN OR RELATING TO MINING MACHINES AND METHODS The invention relates to a mining machine for mining material in a continuous manner, and which can install roof supports during a mining operation. The invention also relates to a method of mining.

Proposals have been made for continuous mining machines which have been able to install roof supports, but these have involved unsatisfactory aspects, or aspects which limit operability to certain areas only. For example, in W085/00636, a continuous mining machine is proposed which has a main frame mounted on tracks, a cutter head mounted on a sub-frame movable by rams towards and away from the main frame and roof bolters mounted at the cutter end of the main frame. The cutter head is of the shearer type having two cylindrical cutting drums attached to each end of a T-shaped arm, the axis of the cutting drums being normal to the direction of movement of the machine. The cutting drums are sumped in and cutting is effected by traversing from one side to the other across the face.This traversing cutting arrangement allows the main frame to remain stable enough to have the roof bolters near the cutter sub-frame, but cutting performance falls well short of being adequate.

The conventional method of cutting for a continuous miner is for the jib to sump in at roof level and to shear down, as opposed to the traversing operation described in W085/00636. However, shearing down in this matter requires mass to be built in to the cutter sub-frame to balance upward forces on it which arise as the cutter shears.

Typically, continuous miners have in the past had a horizontal cutting drum extending the full width of the machine, the drum having cutting picks extending outwardly to attack the face when the drum is rotated. The conventional way for such continuous miners to operate has been to sump in at the roof and cut from roof to floor.

Because of upward forces on the machine generated when cutting downwards in this way, machine instability has been induced such that roof bolting is carried out when the machine is not actually cutting. The applicants for W085/00636 have proposed a modification to the machine shown therein to improve cutting performance but this proposal involves a cutter extending half only of the width of the machine, and even with a half width cutter, roof to floor cutting causes stability problems unless cutting speed is significantly slowed. Thus for simultaneous cutting and roof bolting at the front of the main frame, the cutting speed is slow, negating the advantage of simultaneous cutting and roof bolting, and in any case two passes of the cutter are needed for each roadway advance.

There is thus an unfulfilled need for a continuous mining machine of the type which has a cutting head, extending across the full width of the machine (hereinafter referred to as "a single pass continuous mining machine", a term of art arising from the fact that such machines need a single pass of the cutter head to achieve a full roadway cut) for advantageous speed of cut, but which has machine stability during cutting such that roof bolting can be carried out towards the front of the machine simultaneously with cutting.

In a radical departure from convention, there is provided in accordance with the invention a continuous mining machine comprising a main frame, means for advancing the main frame, means on the main frame in a front region thereof for installing roof support means, a sub-frame, jib means pivotally mounted on the sub-frame and cutter means mounted on the jib means, the cutter means extending substantially horizontally across at least the full width of the machine, means for advancing the sub-frame with respect to the main frame, conveyor means for conveying mined material to the rear of the machine, and means for moving the jib means from a lower position in which the cutter means are at floor level and in which advancement of the sub-frame from the main frame takes place, in use, to sump in the cutter means, to an upper position at roof level, whereby downward force is exerted on the subframe via the jib means during cutting to stabilise the sub-frame and permit stable simultaneous operation of the roof support installation means.

The sub-frame preferably has a floor plate through which downward forces arising from the mass of the subframe, jib means and cutter means and downward reaction from upward movement of the cutter means during cutting are transmitted to the floor.

The floor plate preferably extends across at least most of the width of the machine to adjacent the cutter means when the cutter means are in the lower position.

The pivotal mounting of the jib means on the sub-frame is preferably rearward of the floor plate such that a substantial proportion of the mass of the sub-frame and jib lie rearward of the floor plate.

During cutting, the centre line of downward force arising from the mass of the sub-frame, jib means and cutter means preferably passes through or adjacent the floor plate, in order to minimise reaction transfer to the main frame.

The means for moving the jib means preferably comprises ram means acting between a pivotal mounting on the sub-frame and a pivotal mounting on the jib means.

The pivotal mounting on the jib means is preferably on a lever arm extending on the jib means from the pivotal mounting of the jib means on the sub frame away from the cutter means.

The machine preferably includes a pivoting sliding connection between the main frame and the sub-frame.

The pivoting connection preferably provides for pivotal movement about a horizontal axis only.

The means for advancing the sub-frame with respect to the main frame preferably comprises ram means.

Control means are preferably provided for automatically sequencing the cutting and advancing operations.

The means for advancing the main frame are "CTfi) preferably caterpillaritype tracks.

The means for installing roof supports preferably comprise a multiplicity of roof bolters, there being preferably four roof bolters spaced over the main frame in a front region thereof.

The main frame may include support jacks for supporting the main frame.

The conveyor means may comprise cross conveyors on the sub-frame, which cross conveyors feed to a central conveyor on the sub-frame for conveying material rearwards. The main frame preferably has a conveyor for accepting material from the central sub-frame conveyor for discharging material from the machine.

According to a further aspect of the invention, there is provided a method of mining using a single mining machine comprising the steps of sumping in horizontal cutter means at floor level by advancing a front portion of the machine relative to a rear portion of the machine, carrying out a cutting operation by raising the cutter means to roof level, and simultaneously with the cutting operation installing roof support means over the machine at a forward end of the rear machine portion.

The method preferably comprises an initial cutting step of sumping in at floor level the cutter means by advancing the entire machine, raising the cutter means to roof level and lowering the cutter means prior to sumping in the cutter means by advancing the front portion of the machine.

The cutter means are preferably lowered to floor level after the cutting operation.

The cutting operation may be carried out a plurality of times before the rear machine portion is moved up to the front machine portion again.

By way of example, one embodiment of a mining machine, and a method of mining, according to the invention will now be described with reference to the accompanying drawings, in which: Figure 1 is a side view of a mining machine showing the machine in a closed position; Figure 2 is a side view of the machine of Figure 1 in an extended position; Figure 3 is a plan view of the machine of Figures 1 and 2 in a closed position; and Figure 4 is a larger scale side view of a front sub-frame of the machine of Figures 1 to 3.

Figures 1 to 4 show a continuous mining machine 10 capable of excavating a roadway while simultaneously roof bolting from one central position. Bolters 11 are positioned such that a minimum length of virgin roof is left unsupported and a full complement of roof and cusp bolts can be installed from the basic machine.

The provision for rib bolters can also be made, being mounted at the rear of the machine 10.

The machine 10 is divided into two main parts, a primary chassis 12 and a main machine chassis 13.

Mounted on the primary chassis 12 is a cutting element 14 which is of full face continuous miner type mounted on a central jib 15. The cutting element 14 is capable of excavating up to 4.8m in width and from 1.8 to 3.52m in height. The cutting element has telescopic outer augers 16, 17, being powered both in and out by individual hydraulic cylinders. The closed width of the jib is 4.2m, which affords clearance for the machine during tramming and place changing.

The cutting element 14 is powered by two 190kW (50Hz) continuously rated, water cooled, A.C. electric motors, which have a combined instantaneous pull out power of 950kW. The transmission from each motor is via individual safety clutches, ensuring overload protection and equal load sharing of the two transmissions. The final output to the common headshaft is through epicyclic gear boxes, both housed within the augers.

The use of epicyclic gear boxes gives high power within a small space. Change gears are designed into the early stages of the transmission system, allowing for the selection of the cutting pick tip speed best suited to the individual installation, speed variations of between 2 to 3m/s are available.

Two large 250mm bore hydraulic lift cylinders 18 raise the jib 15 during cutting. Each of the cylinders 18 is fitted with linear displacement transducers giving a continuous readout of the jib position. The jib 15 and the lift cylinders 18 are supported by pivotal mountings 19, 20 respectively on the primary chassis 12.

Reaction to vertical cutting forces are transmitted to the floor through the primary chassis 12 via a floor plate 21. The floor plate 21 supports cross conveyors 22, 23 and has a large area to ensure a low ground pressure of between 29kN/m2 and 40kN/m2 depending on the jib position.

The primary chassis 12, including the jib 15 and cutting element 14 is connected to the main chassis 13 via a sliding, pivoting arrangement as shown in detail in Figure 4. There are two pivoting sliding assemblies 25, one each side of a central member 26 of the primary chassis. As shown in Figure 4, a pivot support 27, to which the central member 26 is pivotally attached, slides in an upwardly opening channel in an elongate support arm 28 being part of the main chassis 13. The pivot support 27 is flanged within the support 28, the channel of the support 28 being inwardly flanged at the top to retain the flanged portion of the pivot support 27 therewithin. The primary chassis 12 can thus move forwards and backwards relative to the main chassis 13, movement being effected by using sump cylinders 30, one for each slide.The sump cylinders have a total stroke of 1.03m and also have linear displacement transducers incorporated giving total control and positional indication of the primary chassis 12 and therefore the jib 15 and cutter element 14 relative to the main chassis 13.

Oil to the jib lift cylinders 18 and sump cylinders 30 is provided by a variable delivery pump controlled electronically by the pump stroker responding to the current feedback from the cutter motors, via an onboard computer.

Horizontal cutting reaction from the cutter element 14 is transmitted back through the jib 15 to the primary chassis 12, the main chassis 13 and ultimately to tracks 32 which are part of a tractor drive arrangement described later. Track pad grousers are designed to give maximum grip to resist slippage during cut.

The loading system of the machine consists of two main conveyors, a primary conveyor 35 mounted on the primary chassis 12 and a delivery conveyor 36 mounted on the main chassis 13. The primary conveyor 35 is fed by the two cross conveyors 22, 23 described earlier. The cross conveyors 22, 23 are individually driven by 22kW high slip, water cooled, electric motors, through an epicyclic and straight spur reduction gear box to a twin strand strap link conveyor chain. The 500mm cross conveyors 22, 23 feed on to the primary conveyor 35 which is driven by a 45kW, water cooled, high slip electric motor 37 through a gear box. The primary conveyor 35 also uses twin strand strap link chain with a width of 760mm.

The whole primary conveyor system moves forward with the primary chassis 12, jib 15 and cutter 14, thus ensuring the most efficient loading position relative to the cutter drum. To provide full width gathering, two large hydraulically powered vertical scoops 39, 40 are located on each end of the apron of the floor plate 21, ensuring a complete pick up of all cut material.

Sufficient overlap exists between the primary conveyor 35 and the delivery conveyor 36 to accommodate full movement of the primary chassis 12 (1.03m). The discharge point of the primary conveyor 35 is linked to the delivery conveyor 36 by a roller mechanism (not shown in detail) ensuring continuity of primary conveyor discharge position, irrespective of the discharge height of the delivery conveyor and position of the primary chassis 12. The delivery conveyor is a 760mm wide, 67mm pitch centre strand chain conveyor driven at the footshaft by a 45kW water cooled, high slip electric motor through a spur reduction gear box.

The delivery section can articulate through 450 either side (see Figure 2) and has a maximum delivery height of 2.565m. The total conveying capacity is commensurate with the cutting capacity of the jib cutter.

Traction for the machine is provided by two 26kW SCR. controlled motors, through a gear box 40 to a double sprocket output drive. Track pads are 550mm wide giving a low ground pressure of 0.164N/mm2 during machine operation. The tracks running on skids are tensioned by grease powered cylinders, with the under carriage and main frame forming an oil tank.

The D.C. powered traction gives a positive sumping action for the cutting element 14 if used as part of a cutting cycle, applied current control offering protection to the traction gearing by eliminating shock loads.

Variable speed is used during the cutting cycle, with traction. Cutter head motor current feedback is provided to reduce traction drive current, and therefore forward thrust. An intermediate and high tramming speed of 0.15m/s and 0.3m/s respectively is available for machine relocation purposes.

Electric motor over speed, over current, and under voltage protection circuits are built into the controller, with diagnostic L.E.D.'s being provided for the aid of troubleshooting.

The main chassis 13 is a three-piece fabrication, with a track frame being an integral part of the chassis forming an oil tank. A header oil tank is also provided into which is built internal oil cooling coils. The header and chassis combine to give a total oil capacity of 1500 litres.

The hydraulic system power pack consists of a 150kW double ended, water cooled motor situated low in the rear of the main chassis 13 to afford optimum aspiration for the hydraulic pumps. The use of a double ended drive motor gives easy access to the hydraulic pumps, and eliminates the need for splitter gear boxes.

A four section fixed displacement pump is used to power drills 11 and machine ancillaries. A further pump is mounted on the opposite end of the pump drive motor providing oil to both the jib lift cylinders 18 and sump cylinders 30, with a special pump strpker controlling the pump capacity to suit the feed requirements determined by the cutter head motor current feedback and the onboard computer. The combined oil flow from the pumps is 590 litres per minute at 136 bar.

High pressure filters with electrical health monitoring are fitted to all pump sections, with optional return line filtration being incorporated into the header tank.

Control of the machine hydraulics is done by proportional and solenoid I.S. control valves, purpose built for the mining industry. The control valves are mounted directly on to the motive unit to reduce the number of hydraulic hoses and improve response times. Where required, linear displacement transducers are built into the hydraulic cylinders as an integral part.

Hydraulically powered support jacks 55 are provided on the main chassis 13 to enable the main chassis 13 to be lifted off the tracks 32 if particular stability is required for the machine.

A programmable controller is used for automatic control of the machine cutting cycle. Access to the computer memory allows for full health monitoring of the machine; functions such as oil temperature, filter conditions, oil pressure are continually monitored.

Output can be to a liquid crystal digit display module positioned at operator position 50, giving warning of imminent problems. Password protected multi channel loggers can be incorporated into the system such that they can record the time a warning has been displayed, useful for warnings such as changing filters or low oil level.

Two electronic inclinometers are built into the main chassis and monitor pitch and roll attitude of the machine.

The drills 11 are heavy duty single mast telescopic drills mounted on the front of the main chassis 13. The drills 11 can all be leant forward by up to 200 from the vertical position and 100 back. The two inner drills lean in or out by 100 from the vertical.

With the two outer drills being able to lean inward by up to 100 from the vertical and outwards by up to 350 from vertical, a full range of bolting patterns including cusp bolt is possible for any size roadway.

Controls for the individual drills 11 are adjacent to each drill 11, with two joystick valves to each drill controlling all main functions. A wide platform has been provided for ease and comfort of the drill operators at the operator position 50. Radio control may be used for driving the machine during manual cutting and tramming, offering the driver the best vantage point for manoeuvring.

Between the cutter element 14 and the operator, a dust barrier is provided, the system used being a proprietary system called the Coanda air curtain. The system is positioned between the drills and the cutter drums on the jib 15. For the system to be fully effective, exhaust ventilation should be in front of the curtain. This is achieved by connecting the exhaust ventilation ducting to the connection at the rear of the machine, ducting passing along the body of the machine up through the jib body. Ventilation is achieved through grilles at the sides, on top and bottom of the headshaft shrouds. Ventilation could alternatively be passed through an onboard scrubber. Additionally, water dust suppression fan sprays are positioned around the auger cutters. Phased high pressure water may be incorporated into the jib.

OPERATIONAL PROCEDURE The operation procedure is determined by a number of variables, namely: 1) Roof conditions (permissible virgin roof) 2) Strap centres 3) Seam height 4) Machine function (turning or straight drivage) Assuming all the above criteria are acceptable, the machine is positioned online in the centre of the roadway.

The jib 15 is positioned so that the cutter element 14 is at floor level and the primary chassis 12 fully closed to the main chassis 13. (position in Figures 1 and 2). The machine is tracked forward to the face and, if presump is required, the cutter element 14 is sumped in to the required depth, using the tracks 32. At this stage, the automatic cut sequence can be brought into operation. This will perform a required number of repeats of the cycle starting with sumping in, then raising the jib 15 to perform a cut, lowering the jib 15 to the floor and sumping in again using the rams 30. Performance of these cycles will continue until sufficient advance for the machine to move forward to the next start position. The cutting sequence may be done manually if so desired. After completing the last shear up of the sequence, the cutter jib 15 will be withdrawn from the face at roof level to ensure a flat roof, then lowered to the start position ready for the next cutting cycle.

The onboard computer has a teach/learn facility, which will enable the operator to go through the complete cutting cycle, taking into account such things as the depth of sump, speeds of shear and other variables which will depend on the particular environment involved.

The computer will then repeat the sequence of commands for the cutting cycle every time the autostart is selected. Alternatively, the time required for the drilling operation may be keyed into the computer. The computer will then calculate the optimum depths of sump and shear speeds, within predetermined maximum limits, in order to complete the cutting cycle at the same time as the drilling operation finishes.

A significant advantage of cutting being carried out from floor to roof, as against the conventional roof to floor method, is that cutting reaction is passed through to the floor of the roadway via the floor plate 21 of the primary chassis 12. This ensures that the floor plate is always kept on the floor during cutting, thus guaranteeing that material cannot get under the primary chassis which would cause horizontal control problems.

Whether manual or computer control of the cutting cycle is selected, once the presump (if required) is completed and shear has commenced, the drill operators are free to commence roof support operations. A safety interlock is positioned at each drill station.

A red light will show when the machine tracks are still in operation, thus warning the drill operators not to commence drilling. Once the machine operator has selected autocut or completed his presump operation, the tracks are then isolated. The red light is then extinguished and the green light lit. The tracks cannot be used again until all four drill operators press the button on their console to indicate that they have completed drilling operations, thus releasing the tracks for operation. The cycle can then recommence.

It will be appreciated that the foregoing description is by way of example only and that alterations and modifications may be made within the scope of the invention.

Claims (23)

CLAIMS:

1. A continuous mining machine comprising: a main frame; means for advancing the main frame; means on the main frame in a front region thereof for installing roof support means; a sub-frame; jib means pivotally mounted on the sub-frame; cutter means mounted on the jib means and extending substantially horizontally across at least the full width of the machine; means for advancing the sub-frame with respect to the main frame; conveyor means for conveying mined material to the rear of the machine; and means for moving the jib means from a lower position in which the cutter means are at floor level and in which advancement of the sub-frame from the main frame takes place, in use, to sump in the cutter means, to an upper position at roof level; whereby downward force is exerted on the sub-frame via the jib means during cutting to stabilise the sub-frame and permit stable simultaneous operation of the roof support installation means.

2. A mining machine according to claim 1, wherein the sub-frame is provided with a floor plate through which downward forces arising from the mass of the sub-frame, jib means and cutter means and downward reaction from upward movement of the cutter means during cutting are transmitted to the floor.

3. A mining machine according to claim 2, wherein the floor plate extends across at least most of the width of the machine and to adjacent the cutter means when the cutter means are in he lower position.

4. A mining machine according to claim 2 or claim 3, wherein the pivotal mounting of the jib means on the subframe is rearward of the floor plate such that a substantial proportion of the mass of the sub-frame and jib means lie rearward of the floor plate.

5. A mining machine according to any one of claims 2-4, wherein the net torque exerted, during cutting, by the downward forces arising from the mass of the sub-frame, jib means and cutter means and downward reaction from upward movement of the cutter means, about at least one point on the floor under or adjacent the floor plate, is substantially zero.

6. A mining machine according to any preceding claim, wherein the means for moving the jib means comprises ram means acting between a pivotal mounting on the sub-frame and a pivotal mounting on the jib means.

7. A mining machine according to claim 6, wherein the pivotal mounting on the jib means is on a lever arm extending on the jib means from the pivotal mounting of the jib means on the sub-frame away from the cutter means.

8. A mining machine according to any preceding claim, further including a pivotal slidable connection between the main frame and the sub-frame.

9. A mining machine according to claim 8, wherein the pivotal slidable connection provides for pivotal movement about a horizontal axis only.

10. A mining machine according to any preceding claim, wherein the means for advancing the sub-frame with respect to the main frame comprises ram means.

11. A mining machine according to any preceding claim, further including control means for automatically sequencing the cutting and advancing operations.

12. A mining machine according to any preceding claim, wherein the means for advancing the main frame comprise caterpillar-type tracks.

13. A mining machine according to any preceding claim, wherein the means for installing roof supports comprise a plurality of roof bolters.

14. A mining machine according to claim 13, wherein there are provided four roof bolters spaced over the main frame in a front region thereof.

15. A mining machine according to any preceding claim, wherein the main frame includes support jacks for supporting the main frame.

16. A mining machine according to any preceding claim, wherein the conveyor means comprise cross conveyors on the sub-frame, which cross conveyors feed to a central conveyor on the sub-frame for conveying material rearwards.

17. A mining machine according to claim 16, wherein the main frame is provided with a conveyor for accepting material from the central sub-frame conveyor and for discharging material from the machine.

18. A mining machine substantially as described herein with reference to the accompanying drawings.

19. A method of mining using a single mining machine comprising the steps of: sumping in horizontal cutter means at floor level by advancing a front portion of the machine relative to a rear portion of the machine; carrying out a cutting operation by raising the cutter means to roof level; and simultaneously with the cutting operation installing roof support means over the machine at a forward end of the rear machine portion.

20. A method according to claim 19 further comprising an initial cutting step of sumping in at floor level the cutter means by advancing the entire machine, raising the cutter means to roof level and lowering the cutter means prior to sumping in the cutter means by advancing the front portion of the machine.

21. A method according to claim 19 or claim 20, further comprising the step of lowering the cutter means to floor lever after the cutting operation.

22. A method according to any one of claims 19-21, wherein the steps of sumping in horizontal cutter means and carrying out a cutting operation are performed a plurality of times, and further comprising the subsequent step of moving the rear machine portion up to the front machine portion.

23. A method of mining substantially as described herein.