GB2129035A

GB2129035A - Mineral cutting machine

Info

Publication number: GB2129035A
Application number: GB08318952A
Authority: GB
Inventors: Alan John Cooper
Original assignee: Pitcraft Summit Ltd
Current assignee: Pitcraft Summit Ltd
Priority date: 1982-10-22
Filing date: 1983-07-13
Publication date: 1984-05-10
Also published as: GB8318952D0; GB2129035B

Abstract

A mineral cutting machine, particularly for coal winning operations, comprises at least one rotary mineral cutting head 9, at least a discharge end of a hollow air supply shaft 12, located in the vicinity of the head 9, along which shaft 12, air is, in use, fed towards a mineral face 2, an air sampling element 18 of a sensing means 20, sensitive to air flow located within the hollow shaft 12, and capable of discharging air into the hollow shaft 12, and control means 23, 8, 39, 40-44, responsive to the sensing means 20, to provide active and/or passive warning signals at a local and/or remote location as to whether an adequate air flow, or is not, being sensed within the hollow shaft 12. <IMAGE>

Description

SPECIFICATION Mineral cutting machine This invention relates to a mineral cutting machine, whether for mineral winning purposes e.g. during coal mining operations, or for tunnel or roadway driving purposes e.g. during civil engineering or mining operations.

In the longwall mineral winning technique, in contrast to the room and pillar technique, a mineral winning machine is reciprocated along a mineral face to remove a web of material.

However, irrespective of the technique involved, conventional mineral winning machines are provided with at least one rotary cutting head, provided with picks, the head being driven through a transmission, from a prime mover, e.g. an electric motor mounted in the machine body and the head usually being displaceable with respect to the machine, e.g. by being mounted on a ranging arm pivotally attached to the machine body, whereby undulations of the mineral seam may be followed and/or roadway ripping operations may be effected at one or both ends of the mineral face. In principle, longwall machines are provided with one of two cutting heads dependent upon whether they are single-ended or double-ended machines, while continuous mining machines have at least one leading end cutting head.

In order to control and dilute methane etc., released at the face, it is standard practice to ventilate the face by coursing an air supply along the face. In addition, a technique known as hollow shaft ventilation, employs a high pressure water supply e.g. at 1 500-2000 p.s.i., generated by a water pump, to induce a flow of diluting air along a hollow shaft on which the rotary cutting head is mounted, from the goaf side to the face side of the head, where of course methane etc. release occurs, with the jet or mist of water droplets additionally serving for dust suppression purposes.

Such a system has proved generally satisfactory, even where fissures are encountered with the consequent release of large volumes of methane but requires a high pressure hose extending from the water pump which is conventionally located in a roadway at one end of the face, with further, low pressure hose to convey water; e.g. at 300-400 p.s.i. for what is known as pick face flushing, for the main dust suppression effect.

In our co-pending U.K. Patent Application No.

8212345 there is described a mining machine which firstly eliminates the need for the high pressure hose and secondly employs a transmission comprising a clutch, with a water pressure sensing device controlling the clutch, whereby the latter may not be engaged in a drive condition until a predetermined water pressure has been obtained.

In some circumstances however, even the attainment of a satisfactory water pressure and hence engagement of the clutch and activation of the transmission does not guarantee that ventilation is occurring -- there may for instance be a blockage of the hollow shaft and/or the spray jet located within the hollow shaft, which produces an air flow along the hollow shaft.

According to the present invention, there is provided a mineral cutting machine, particularly for coal winning operations, comprising at least one rotary mineral cutting head, at least a discharge end of a hollow air supply shaft located in the vicinity of the head, along which shaft air is, in use, fed towards a mineral face, an air sampling element of a sensing means sensitive to air flow located within the hollow shaft and capable of discharging air into the hollow shaft, and control means responsive to the sensing means to provide active and/or passive warning signals at a local and/or remote location as to whether an adequate air flow is, or is not being sensed within the hollow shaft.

Thus, the machine in accordance with the invention provides a warning signal to the machine operator in accordance with air flow or non-air flow conditions within the hollow shaft.

In a passive mode, adequate air flow may be used to create a voltage (to be described in detail later) to indicate safe conditions, while absence of a voltage, resulting from a non-existent or inadequate air flow, may be used to trigger an audible and/or visible alarm or indicator.

It is preferred however to use the warning signals in an active mode -- possibly simultaneously with the passive mode. Hence alternatively or in addition, an active mode may be used to prevent initial start-up of the rotary cutting head, or to bring about stoppage of the rotary cutting head. Thus, in the active mode or combined active and passive modes, an air flow, and hence proper ventilation is guaranteed before start-up of the rotary cutting head can occur.

Air feed along the hollow shaft may be induced by the presence and operation within the hollow shaft of one or more spray nozzles to direct a water jet or mist along the hollow shaft, and this induced flow along the hollow shaft in turn induces an air flow along the sampling tube for discharge into the hollow shaft.

In a first embodiment, the machine may be of the shearer type, with the or each rotary cutting head having a hollow shaft co-axial with the axis of rotation of the head, with the head rotatable about the shaft.

In a second embodiment, the machine may be of the roadheader type, with the hollow shaft carried by a boom which, at its end remote from the machine, carries a rotary cutting head.

In one construction an inlet end of the air sampling element may be provided at a location remote from the hollow shaft, and hence draw in ambient air, while in a second embodiment, the inlet end may also be located within the hollow shaft.

The machine may incorporate a transmission from a prime mover, e.g. an electric motor, to the or each rotary cutting head, the or each transmission incorporating a clutch. Thus, the control means may, in the modes other than purely passive, be employed to control the clutch via a circuit, e.g. a pilot circuit or an electrohydraulic circuit. Thus, if a non-healthy signal is received during mineral cutting, the clutch is disengaged by the electro-hydraulic circuit and/or the electric motor is switched off by the pilot circuit, and iikewise before start up a healthy signal must be supplied before the clutch can be engaged and/or electric motor switched on.In detail, a first timer, e.g. of an electronic type may be employed, which by-passes the sensing means, and after a pre-determined delay period, e.g. 1 5 seconds, this first timer stops the motor unless the sensing means indicates a healthy condition. It will be appreciated that additional sensing means to monitor functions other than air flow in the hollow shaft may similarly be by-passed initially and subsequently trigger motor shut down if a non-healthy condition is sensed.Assuming however, as would usually be the case, that the motor is still running after the first timer has completed its timing period, the clutch may be engaged to transmit drive to the associated rotary cutting head, but preferably not until a second timer, e.g. of an electronic type, has completed its timing period, e.g. 7-10 seconds, to enable a pre-start warning to be activated, and after this period, the pre-start warning device -- which may be of an audible kind - is de-activated and the clutch is engaged. Conveniently, the clutch is hydraulically actuable. It follows that it is also preferred to provide a sensing device for clutch oil pressure (if the oil pressure is low, the clutch will slip and overheat), which constitutes another health monitoring feature.

Sensing of the air flow along the hollow shaft may be effected by the vortex shedding technique.

In detail, an air sampling tube may be located in the hollow shaft and piped back to a safe location on the machine where a flow transducer is located. The flow transducer preferably incorporates means to disturb the air flow and create vortices and measuring means or counting means, e.g. an ultrasonic beam projected across a tube, to count the vortices, no vortex count indicating no air flow and hence, in the example described above, prevents clutch engagement.

Conveniently, the presence of vortices is used to generate a voltage by electronic circuitry, with no vortices producing no voltage. In detail a piezoelectric transmitter may be located at one side of the sampling tube in the vicinity of the flow transducer, with a piezoelectric receiver located at the opposite side of the sampling tube, the receiver generating an output in response to the output of the transmitter and the presence or absence of vortices, and the output of the receiver being fed to one or more electronic circuits capable of generating a voltage upon vortices being sensed between prescribed parameters. The safe location of the flow transducer can be on or in the machine body, or on or in a ranging arm thereof on which the cutting head is rotatably mounted.The flow transducer may be sensitive to too high or too low an air flow beyond a pre-set range, to sense a variety of conditions. Thus, complete or partial blockage of the inlet end of the hollow shaft would result in high air flow along the sampling tube outside the pre-set range to trigger a warning signal. On the other hand complete or partial blockage of the inlet end of the sampling tube would result in a non-existent or low vortices count to trigger a warning signal.If it should be the case that particular operating conditions could result in the inlet end of the hollow shaft and also a remotely located inlet end of the sampling tube becoming partially blocked, then it is not inconceivable that healthy signals may result, when healthy conditions do not in fact exist, and in this case, location of the inlet end of the sampling tube within the hollow shaft obviates erroneous signals from partial blockage of both of the inlet ends.

The invention will now be described in greater detail, by way of examples, with reference to the accompanying drawings, in which: Figure 1 is a plan view of a first embodiment of single-ended ranging drum shearer type of mineral winning machine in accordance with the invention; Figure 2 corresponds to Figure 1 but shows a second embodiment; Figure 3 corresponds to Figure 1 but shows a third embodiment; Figure 4 corresponds to Figure 1 but shows a fourth embodiment; Figure 5 corresponds to Figure 1 but shows a fifth embodiment; Figure 6 is a side elevation of a tunnel or roadway driving machine in accordance with the invention.

In ail embodiments, like components will be accorded like reference numerals.

In Figures 1 to 5, a longwall mineral mining machine 1 is shown located alongside a face 2 of a mineral seam 3, the machine being mounted on, and guided by, an armoured, scraper chain conveyor (not shown) also located alongside the face 2 and connected, in the well-known manner, to a series of self-advancing, hydraulically powered, mine roof supports (not shown). The machine comprises a motor module 4 housing an electric motor (not shown) having a first output shaft to a machine haulage unit 5 comprising a drive sprocket 6 adapted to engage a rack bar or a chain associated with the conveyor. The electric motor has a second output shaft 7 to power via a clutch 8 (to be described in detail later) a pick carrying, rotary cutting head 9 mounted on a ranging arm 10 which is pivotally attached to a gearhead 11 of the machine 1 and is displaceable about its pivot by a double-acting control ram (not shown), in the well-known manner.

A hollow shaft 12 is located in the vicinity of the rotary cutting head 9 in that it is co-axial with the axis of rotation of the rotary cutting head 9 and incorporates at least one water spray nozzle 13 connectable to a source of pressurised water, to produce water jets 14 to induce a flow of air along the hollow shaft for methane dilution purposes, the major proportion of air being drawn into an inlet end 1 5 of the hollow shaft 12 remote from the mineral face 2 as indicated by arrows 16, and a minor proportion of air being drawn from a discharge end 1 7 located within the hollow shaft 12 of a sampling tube 18, this air supply being indicated by arrow 19.The sampling tube 18 extends through a vortex shedding flow transducer 20 incorporating an air filter 21 to terminate in an inlet end 22 to draw in ambient air under the inducement of the water jets 14. In the embodiment of Figure 1 the flow transducer 20 has an electrical output connected to an electrical relay 23 having an electrical power supply via leads 24 from a source not shown, the relay 23 in turn being connected to a solenoid-operable control valve 25, in turn connected by a line 26 to a hydraulic actuator 27 adapted to displace a clutch operating lever 28 to place the mating drive elements 29, 30 of the clutch into or out of driving engagement, the element 30 being attached to a drive shaft 31 to drive a speed reducing transmission 32 contained within the gearhead 11 and 33 contained within the ranging arm 10, to power the rotary cutting head 9.Connected in series with the solenoid-operable clutch control valve 25 is a manually operable clutch control valve 34, having a manually operable lever 35.

The valve 34 is in turn connected to a hydraulic pump 36 and pressure relief valve 37, the valves 25,34, pump 36 and relief valve 37 all being connected to tank 38.

The arrangement is such that with the electric motor of module 4 running, the machine operator appropriately displaces operating lever 35 when it is desired to commence rotation of the rotary cutting head 9 and pressure water is supplied to spray nozzles 13 to produce water jets 14 to induce an air flow along the hollow shaft 12.

However, because of the interposition of valve 25 between valve 34 and the hydraulic actuator 27, the clutch is not immediately engaged, but remains in the position illustrated, until such time as a healthy signal -- indicating an adequate air flow in the hollow shaft 12 - has been received by the sampling tube 1 8, flow transducer 20, and relay 23. Thus in the embodiment of Figure 1, an active warning signal is received from the components 1 8 and 20, resulting in the prevention of clutch engagement and hence rotation of the rotary cutting head 9 until adequate air flow has been proved.

In the embodiment of Figure 2, a passive warning system is employed in that output signals from the flow transducer 20 are simply fed to an analogue or digital readout 39 calibrated in units of volume.

In the embodiment of Figure 3, a passive warning is again employed with output signals from the flow transducer 20 fed to a first electrical relay 23A and then to a bell 40 -- operation of which would indicate a high air flow and hence a blocked intake end of the hollow shaft 12, and a second electrical relay 23B and then to a horn 41 - operation of which would constitute a low flow warning.

In the embodiment of Figure 4, another passive system is indicated, but one which would overcome the possibility of a false condition being sensed, due to partial blockage of the inlet end of both the hollow shaft 12 and the sampling tube 18. In this embodiment the inlet end 22 of the sampling tube is located within the hollow shaft and hence draws not ambient air but air from within the shaft. A relay 23A is connected to a low warning light 42 and adequate flow indicator light 43.

In the embodiment of Figure 5, is illustrated an active system with the output from relay 23 opening or closing a conventionally provided pilot circuit 44 of the machine 1.

In the embodiment of Figure 6, a roadheader type mineral cutting machine 1A is illustrated, for the driving of a tunnel or roadway 45, shown being advanced at a face 46. A rotary cutting head 9A is mounted at one end of a displaceable boom 47 attached at its other end to the machine 1 A, which is mounted on crawler tracks 48.

Conventionally, the machine 1A is provided with a pick-up conveyor 49 to discharge onto a belt conveyor 50 extending along the roadway 45.

A discharge end 51 of a hollow shaft 1 2A is located in the vicinity of the rotary cutting head 9A, the hollow shaft in this embodiment being constituted by ventilation ducting extending a considerable length along the roadway 45 and carried on a wheeled track or runner system in turn carried by the conventionally provided I-section, roadway supporting rings 52. The hollow shaft 1 2A is carried in part by the boom 47 and in part by rings 52 supporting the roadway 45.

Adjacent the discharge end of the hollow shaft 12 is a water spray nozzle 1 3 connectable to a source of pressurised water, to produce jets 14 of water, to induce an air flow along the hollow shaft 12. Also adjacent the discharge end of the hollow shaft 12 is a sampling tube 1 8 connected to an air flow transducer 20 mounted on the machine 1 but, for purposes of illustration, shown to an enlarged scale in Figure 6, the sampling tube 1 8 having an inlet end 22 and an air filter 21, with electrical leads 53 extending to an alarm system.

In this embodiment there is also illustrated the possibility of monitoring the condition of the air entering the inlet end 1 5 of the hollow shaft 12, by means of a methanometer 54 having sampling tubes 55 located within the hollow shaft 12 and electrical leads 56 connected to an alarm circuit.

Claims

1. A mineral cutting machine comprising at least one rotary mineral cutting head, at least a discharge end of a hollow, air supply shaft located in the vicinity of the head, along which shaft air is, in use, fed towards a mineral face, an air sampling element of a sensing means sensitive to air flow located within the hollow shaft, and control means responsive to the sensing means to provide active and/or passive warning signals at a local and/or remote location as to whether an adequate flow is, or is not, being sensed.

2. A machine as claimed in Claim 1, in a passive mode, wherein warning signals are used to trigger an audible and/or visible alarm.

3. A machine as claimed in Claim 1, in an active mode, wherein warning signals are used to prevent initial start-up of the rotary cutting head or to bring about stoppage of the rotary cutting head.

4. A machine as claimed in any preceding Claim, wherein the machine is of the shearer type, with the or each rotary cutting head having a hollow shaft co-axial with the axis of rotation of the head and with the head rotatable about the hollow shaft.

5. A machine as claimed in any one of Claims 1 to 3, wherein the machine is of the roadheader type, with the hollow shaft carried by a boom which, at its end remote from the machine, carries a rotary cutting head.

6. A machine as claimed in any preceding claim, comprising a transmission from a prime mover.

7. A machine as claimed in Claim 6, wherein the prime mover is an electric motor.

8. A machine as claimed in Claim 7, wherein the transmission incorporates a clutch, which clutch is controlled by the control means.

9. A machine as claimed in any one of Claims 1 to 8, incorporating a first timer, which bypasses the sensing means and after a predetermined delay period stops the motor unless the sensing means indicates a healthy condition.

10. A machine as claimed in Claim 9, wherein the timer is of an electronic type.

11. A machine as claimed in Claims 9 or 10, incorporating a second timer also effective to control engagement or non-engagement of the clutch to enable an audible pre-start warning to be sounded.

12. A machine as claimed in any preceding Claim, wherein the sensing of the air flow along the hollow shaft is effected by a vortex shedding flow transducer.

13. A machine as claimed in Claim 12, wherein an air sampling tube is located in the hollow shaft and piped back to a safe location on the machine where the flow transducer is located.

14. A machine as claimed in Claim 12 or 13, wherein the flow transducer is sensitive to too high or too low an air flow beyond pre-set datum.

1 5. A machine as claimed in Claim 5, and any Claim appendant thereto, incorporating a methanometer connected to ventilation ducting.

1 6. A mineral cutting machine substantially as hereinbefore described with reference to Figure 1 of the accompanying drawings.

17. A mineral cutting machine substantially as hereinbefore described with reference to Figure 2 of the accompanying drawings.

18. A mineral cutting machine substantially as hereinbefore described with reference to Figure 3 of the accompanying drawings.

19. A mineral cutting machine substantially as hereinbefore described with reference to Figure 4 of the accompanying drawings.

20. A mineral cutting machine substantially as hereinbefore described with reference to Figure 5 of the accompanying drawings.

21. A mineral cutting machine substantially as hereinbefore described with reference to Figure 6 of the accompanying drawings.