GB2092207A

GB2092207A - Improvements in or relating to mining systems

Info

Publication number: GB2092207A
Application number: GB8201867A
Authority: GB
Original assignee: Dobson Park Industries Ltd
Current assignee: Joy Global Industries Ltd
Priority date: 1981-01-24
Filing date: 1982-01-22
Publication date: 1982-08-11

Abstract

Monitoring of the position of a mining machine along a longwall mine face working is provided by sensing changes in a mechanical parameter such as applied weight, noise, vibration, pressure fluid back pressures or pulsations, or strain. Sensors responsive to the mechanical parameter concerned are spaced at intervals along the mine face, typically at or adjacent to self-advancing mine roof supports (20) arranged in a row coupled to a mine face conveyor (14). Suitable mining machine guide, face conveyor and support sites for appropriate sensors are shown (40A to 40H). Electrical detection of changes of the mechanical parameter will usually be performed after filtering and on a suitable sampling basis. <IMAGE>

Description

SPECIFICATION Improvements in or relating to mining systems The invention relates to mining apparatus and is applicable especially to monitoring the position of a mining machine as it travels to and fro along a mineral face from which mineral is won by one or more cutters carried by the mining machine.

Monitoring, and remote indication, of the position of such a machine along the face may be necessary for several reasons, for example, signalling machine stoppages or enabling management to compare rates of traverse during successive traverses or cuts of the face by the machine. A more important reason for monitoring machine position, however, concerns the advancing of the roof supports and conveyor once the machine has passed, especially if such advancing is to be done automatically.

It is important to advance the conveyor and roof supports or at least parts of the latter as soon as possible after the machine has passed along the face, so that the roof of the space exposed by the machine will not be left unsupported very long.

Otherwise debris may fall on the face side and thus into the path of the conveyor preventing it being fully advanced. This may also result in a roof condition which is difficult to support without manual intervention. However, a certain space or distance, usually referred to as the "machine head way", must be left behind the machine as it travels along the face, usually on a guide rail carried by or an integral part of the conveyor, so that the machine is not trapped between the conveyor and the face. Thus the conveyor generally known as an armoured face conveyor advances in snake-like manner from one end of the face as the machine traverses the face.

Typically the "head way" is approximately equivalent to the distance occupied by five or six of the roof supports arranged in a row behind the conveyor generally parallel to the face.

Various proposals have been made for monitoring the position of the machine relative to the end of the face. According to one proposal this is done by measuring the paid-out length of a chain or cable attached to the machine from a known datum at the face end. This system is not very reliable or accurate however and does not easily give readings which are related directly to the position or location in the row of a particular roof support to which the machine is adjacent.

It has also been proposed to transmit high frequency signals, for example infra-red or microwave signals, between the machine and the roof supports it passes. This is not entirely satisfactory, however, since fragile expensive equipment must be attached to the machine, its carriage and/or the roof supports where it is liable to be damaged. Also the transmission path between the machine and the roof supports can easily be obstructed.

An object of the present invention is to eliminate or at least mitigate one or more of these problems and to provide apparatus for monitoring the position of the mining machine which is or may be robust, simple and reliable.

According to the present invention, there is provided apparatus for monitoring the position of a mining machine traversable along the length of a longwall mine face, comprising a plurality of sensors spaced apart along the length of the face and adjacent the path of travel of the mining machine, each sensor being operative to provide an output signal in response to a mechanical parameter which changes at the sensors according to the position of the mining machine, means operative in response to output of the sensors to provide a signal representative of machine position relative to the sensors.

It is convenient to refer to the accompanying drawings, in which: Figure 1 shows part of a longwall mine working where a mineral face 10 is cut by a mining machine 12 that delivers cut mineral into a serial pan articulated armoured face conveyor 1 4 snakable (16) in front of a row of mine roof supports 20 (only bases of which are shown) having advancing ram means 22; Figure 2 shows a mine roof support 20 having a roof-engaging canopy 24, a floor-engaging base 26, hydraulic raising and lowering props 28, 30; and Figure 3 is a block circuit diagram for monitoring apparatus hereof having at each support, support position, or other suitable spaced intervals, a sensor 40 providing an electrical signal for a selection filter 42, detector 44 and indicator/ communication system 46.

The passage of a mining machine along a mineral face results in many mechanical parameters changing.

In one preferred embodiment each sensor 40 detects a temporary change in the mechanical parameter, advantageously directly related to proximity of the machine to the sensor. In particular, the sensors may detect vibration or noise associated with the mineral winning operation, for example generated by the cutting head. The intensity of this vibration or noise will increase as the machine approaches a particular sensor, reach a maximum when the machine cutting head is, or the machine mountings are, close to the sensor, then diminish as the machine travels away from the sensor.

It will be appreciated that in the case of a bidirectional shearer, or like machine having two spaced cutters, the sensors 40 may detect the proximity of the particular cutter which is operating. Control of the particular cutter which is operating. Control means may then take account of this in accordance with the direction of travel.

Where both cutters operate simultaneously, the control means may provide a mean machine position signal, perhaps derived from several sensors 40.

Sensors responding to actual cutting operations will not sense the position of the machine when it is flitting without the cutter operating.

One solution to this problem could be to mount sensors on or adjacent a part of the machine guide, for example on the conveyor spill plate, so as to respond to local vibration of the conveyor due to passage of the machine itself. For illustrative purposes only, Figure 2 indicates a machine guide rail 32 actually attached to the face conveyor 14 and a spill plate 34 with possible sensor positions indicated at 40A, 40B and 40C.

Alternatively, the sensors may respond to a change which, though temporary, is more directly related to the presence of the machine. For example, where the mining machine is supported, at least partly, by a conveyor which transports the mineral away from the face, as a particular stretch of the conveyor is traversed by the machine it, or its joints, will experience an abrupt change in the forces applied thereto, both laterally and vertically.

The laterai forces will increase due to reaction forces needed to maintain the cutter in contact with the mineral being hewn and will usually be absorbed by advancing rams between the conveyor and the roof supports. Therefore, the change in this force may be sensed by monitoring the fluid pressure in those rams say as back pressure or pulsations or the strain in the parts connecting the advancing rams to the conveyor and/or support, see 40D and 40E in Figure 2.

Even if the machine is not operating, the presence can be detected by monitoring the loading on the guide rail or conveyor (see 40A, 40B) which will, of course, be increased due to the weight of the machine itself.

Another parameter which experiences a steplike increase is the load applied to the roofsupports by the roof. As the machine passes by a particular roof support, the extent of unsupported roof ahead of that roof support suddeniy increases due to removal of mineral from the face by the machine. The increased loading persists until some time after the machine has departed, when the support is lowered prior to being advanced. It is envisaged that the sensors might conveniently detect the change in loading by sensing the strain in the forwardly-projecting part of the roofengaging part of the support, see 40F, or any other suitable part say extension 36, or by sensing the fluid pressure (say as back pressure or pulsations in the front prop 28 of the support, see 40G, or in a specific forward canopy support ram (40H) should the canopy be hinged as at 38.

Especially where the mechanical parameter being sensed is vibration or noise, detection means and/or control means may be arranged to sample the output from each sensor several times during a predetermined time interval, say several seconds, and then produce-an average signal for that interval. In this way effects of false readings due to spurious disturbances are reduced. A sampling circuit 48 is shown in Figure 3 along with a local indicator 50 should that be required.

Addressing and sample gating logic are indicated at 52, 54 for remote control and information processing over lines 56, 58, 60, or a lesser number of lines with serial transmission.

Preferably the sensors 40 are each associated with a particular one of a row of roof-supports past which the machine travels along the face.

Every roof-support may have an associated sensor 40, or possibly selected ones, preferably spaced at regular intervals along the row. Then the detection means 40 and/or control means 46 may provide an output signal indicating the position or location in the row of the roof support relative to which the machine position is determined, for example that which is being passed by, or was last passed by, or is closest to, the machine. This output signal may then be used in controlling automatic advancing of the conveyor and roof supports after the machine has passed, i.e. making addressing 52 irrelevant and unnecessary.

Operation of the control means may readily take account of the need to leave unadvanced the predetermined length of conveyor behind the machine, previously referred to as "headway".

The sensor 40 may, of course, be associated positionally with a particular roof support without actually being connected to it. For example, the sensor 40 may be coupled to an advancing ram or to the conveyor or a guide rail for the machine at a position corresponding to that of a roof support.

The sensors may respond to transient changes due to passage of the machine and transmitted to the roof supports by way of the mine-roof. Such transient changes may be due to cutter proximity, or to fluctuation in roof load as mineral is removed. The sensors may then comprise pressure transducers connected to the roof support so as to respond to the pressure of the hydraulic fluid in the props. A high-pass filter means may then be provided to filter out the steady state signal corresponding to the comparatively static pressure in the props, and pass only the relatively high frequency signal corresponding to the transients. Specific noise emission means may be associated with the mining machine.

A suitable low pass filter means might also be connected to the output of the same pressure transducer enabling it, advantageously, also to be employed to produce a signal indicating actual prop-or leg-pressure, and/or whether a required setting pressure has been attained.

Conveniently a transducer is of the acoustic type, such as commonly used for detecting vibration in machine bearings, and preferably derives the energy for its output signal directly from the mechanical energy it is sensing. A moving-coil type transducer, suitably loaded and damped, may be of particular advantage since it could be permanently coupled in the detection circuit without significant power drain.

It is envisaged that the position monitoring system of the invention could be iinked to a computer for controlling automatic advancement of the conveyor and mine roof supports as required by the position of the cutting machine. In some embodiments, the position sensors will, of course, only indicate the cutting machine when its prime mover or cutter is in operation. However, the computer system can be programmed to remember the last indicated position.

Claims

1. Apparatus for monitoring the position of a mining machine traversable along the length of a longwall mine face, comprising a plurality of sensors spaced apart along the length of the face and adjacent the path of travel of the mining machine, each sensor being operative to provide an output signal in response to a mechanical parameter which changes at the sensors according to the position of the mining machine, means operative in response to output of the sensors to provide a signal representative of machine position relative to the sensors.

2. Apparatus according to claim 1, wherein the sensors detect vibration.

3. Apparatus according to claim 1, wherein the sensors detect changes of loading on mine face equipment.

4. Apparatus according to claim 2 or claim 3, wherein the sensors are mounted to detect vibration in or loading of guide means traversed by and due to the mining machine.

5. Apparatus according to claim 2 or claim 3, wherein the sensors are mounted to detect vibration in or loading of parts coupled to the guide means.

6. Apparatus according to claim 4 or claim 5, wherein the guide means is of or associated with a face conveyor.

7. Apparatus according to claim 6 with claim 5, wherein the sensors are mounted to detect vibration induced in or loading of pans or spill plate means of the face conveyor.

8. Apparatus according to claim 6 with claim 5, wherein the sensors are mounted to detect vibration induced in or loading of couplings between the face conveyor and roof supports arranged in a row to support the face working.

9. Apparatus according to claim 8, wherein the couplings include ram means by which the supports and face conveyors are advanceable.

1 0. Apparatus according to claim 9, wherein the sensors serve to detect changes of pressure in hydraulically operated said rams.

11. Apparatus according to claims 3, wherein the sensors are mounted to detect vibration in or changes of loading of roof supports arranged in a row to support the face.

12. Apparatus according to claim 1 wherein the sensors serve to detect changes of pressure in hydraulic prop means of the supports.

13. Apparatus according to any one of claims 3 to 12, wherein the loading detected by the sensors corresponds to lateral forces.

14. Apparatus according to any one of claims 3 to 13, wherein the loading detected corresponds or further corresponds to vertical forces.

1 5. Apparatus according to claim 14 with claim 11, wherein the vertical forces comprise strata loading according to whether or not mineral has been cut from in front of the supports prior to sequential advance thereof.

1 6. Apparatus according to claim 15, wherein the sensors are associated with forwardly extensible parts of the roof supports.

17. Apparatus according to claim 16, wherein the sensors comprise strain gauges associated with said extensible parts.

1 8. Apparatus according to claim 1, wherein the sensors detect noise from the mining machine.

1 9. Apparatus according to claim 18, wherein the noise is from a specific source associated with the mining machine.

20. Apparatus according to claim 18, wherein the mining machine has at least one cutting head and the sensors serve to detect operation of such shearing head.

21. Apparatus according to any preceding claim, wherein the positions of sensors correspopnds to positions of some or all of roof supports or said roof supports arranged in a row to support the face working.

22. Apparatus according to claim 21, wherein sensor control or detection means is linked with an overall face control system for the roof supports.

23. Apparatus according to claim 22, wherein the control or detection means includes means for periodically sampling the sensors.

24. Apparatus according to any preceding claim, wherein the sampling means includes selective filter means for selecting desired relevant sensor output variations.

25. Apparatus for monitoring the position of a mining machine traversable along the length of a mine face, substantially as herein described in accordance with claim 1 and as shown in the accompanying drawings.