Mine roof support control

A mine roof support control monitoring system in which at least some of a row of self advancing mine-roof supports at a mine face each include means for providing data relating to successive advances of that support. This data is accumulated by other means of the system and stored to give readily available indicationsof differences of actual support advances. The system preferably further includes means for pre-energizing the advance mechanisms of such supports to eliminate data relating to slack or tolerance.

The invention relates to mining, and has particular application in remote 
control systems for self-advancing mine-roof supports. 
At the mineral face of a mine working it is normal to have a row of 
self-advancing mine-roof supports cooperating with a face conveyor and a 
mining machine that traverses the face to cut material which is carried by 
the face conveyor to conveyor systems usually in a gate at one end of the 
face for transportation away from the face. It is common practice for the 
mine-roof supports to be equipped with pressure-fluid-operated means so as 
to be advanced sequentially. Each support serves first in pushing the face 
conveyor towards the face behind the mining machine as it traverses the 
face. When there is at least a predetermined headway on the mining 
machines the mine-roof supports are sequentially lowered usually one at a 
time, and pulled towards the face conveyor whereupon they are reset to the 
roof. Any attempt to automate these operations will meet the usual demand 
that the face be kept straight and the services of surveyors are required 
to ensure that the advances of the mine-roof supports do not result in 
unwanted curvature of the face, as would result from differential advances 
of the supports, particularly over a succession of advances thereof. 
It is an object of this invention to provide means to facilitate the 
maintenance of desired relative positions of self-advancing mine-roof 
supports, and to this end the invention proposes a system for monitoring 
the relative positions of such supports by separately accumulating and 
storing data relating to successive actual advances for at least some of 
the supports. 
Preferably, the data accumulated concerns erros between actual advances and 
specified advance distances, though, clearly, accumulation of actual 
advance data would give, for the supports concerned, totals from which 
corrections could readily be made. 
In a preferred embodiment of the invention, such a central system comprises 
a plurality of separate support-related units each for receiving and 
translating coded electrical control signals into support advance 
implementing signals, and for supplying coded electrical data signals 
representative of the extent of an advance movement of the related 
support, a control unit, and a communication network for carrying the said 
control and a data signal between the support-related units and the 
control unit, the control unit including resettable means responsive to 
the data signals for accumulating, for each mine-roof support, individual 
differences from successive desired advances or even the numerical values 
of the data signals themselves. 
In implementing such a system, the control unit may be provided with 
word-organised binary data storage means having at least one word location 
dedicated to each support, and accumulator or adder means for updating the 
contents of each such word location at the time of an advance of the 
corresponding support. The word locations may be registers driving a 
single numerical display via register scanners or other means, or driving 
individual numerical displays or parts of a display, or may be part of a 
word-organised writable semiconductor store, often referred to as a RAM, 
included in a controlling computer system associated with a visual display 
for accumulated error or total advance data. 
The support-related units may supply a direct digitised representation of 
the extent of an advance, in which case the control unit may compare 
incoming data signals with a preset datum value, say by a subtractor or in 
a subtraction operation. Alternatively, the support related units may 
supply an offset from a preset desired advance of the corresponding 
support, in which case the control unit will simply accumulate incoming 
data signals, which should, of course, include a sign indication, using an 
adder or an addition operation in a computer, preferably a micro-computer, 
system. 
Such a system will therefore store, and display as required, indications of 
the extents to which individual mine roof supports exceed or fall short of 
a total advance represented by the number of advance cycles which have 
taken place since the storage means was reset. Initially, or periodically, 
such resetting will take place following a survey of the face and 
adjustment of the positions of the supports until they have a desired 
relative relationship. At the time of each such re-survey the monitoring 
system can supply correction data via the display. System embodying this 
this invention are therefore particularly well adapted to use in a mine 
face control system that provides for automatic advancing of the supports 
in an automatic mode of operation, and allows support position adjustments 
or corrections by an operator in a separate manual mode of operation, 
which, if desired, may be one of two manual modes, one latched to achieve 
a preset advance and the other unlatched to advance for as long as there 
is a manual demand for it. Provision could be made so that, during the 
correction operation, the accumulated error for a particular support is 
displayed and offset automatically in accordance with the positional 
adjustment made, thereby automatically resetting the storage means. 
Preferred self-advancing mine-roof supports use a double-acting hydraulic 
ram for pushing the face conveyor and pulling the support, and known 
devices, for example using potentiometers, for measuring the extension or 
stroke of the ram and thus the extent of the advance. Such devices may be 
associated with selective presets to control a maximum or desired advance 
and/or supply a different signal relative to an adjustable preset. 
It would, of course, be equally possible, if not preferable, to use 
ultrasonic ram extension monitoring devices of the type to which our 
copending application No. 52259/75 relates. 
Often, although the pulling operation to bring a support to the face 
conveyor is required for every support, it is satisfactory for an even 
distribution of less than all, say as few as a quarter, of the supports to 
perform the pushing operation whereby the face conveyor is moved up to the 
mineral face. In such a system, face adjustment may be satisfactorily 
monitored using data signals from only those supports that will be 
involved in pushing the face conveyor. 
Adjustment of individual mine roof supports in order to cancel cumulative 
advance discrepancies and thereby maintain the alignment of the face, 
places stringent requirements on the accuracy of the advance measuring 
signal, and it is further desirable herein to facilitate such accuracy. 
Accordingly a mine roof support having advance measuring, and signal 
producing means is, for an advance of the support, made operative to 
energise its support advance means prior to release of the support from 
between the floor and the roof, so as to take up any play in the linkages 
associated with such advance means, the advance measuring and signal 
producing means being operative after such take-up of play, say on release 
of the support. 
In operating the advance means, typically a pressure-fluid-operated ram, 
while the roof support is set between the floor and roof, it may be that, 
in addition to taking up any play, the face conveyor itself, where that 
acts as an anchorage for the advance means, will also be moved to some 
extent. However, this will not affect the accuracy of the signal generator 
in representing actual roof support advance. 
In preferred embodiments, a sequencer will be incorporated whereby a 
support advance phase of operation will, on initiation, automatically 
cause energisation of the support advance means prior to lowering of the 
roof-engaging structure of the support to allow the advance to take place. 
Such a sequencer may be incorporated at the roof supports themselves, say 
as a pre-determined time delay prior to release and lowering of the 
support, or as a pre-requirement regarding the achievement of a minimum 
resistance, typically pressure or back pressure, in the support advance 
means, or even related to sensing roof support ram conditions. 
Such a sequencer may be incorporated in the support related coding, 
decoding and control units of the system of our above-mentioned 
application. Alternatively, a sequencer may be incorporated in a remote 
control unit where that unit also issues support control signals to the 
supports, although it may well be generally preferred for a single signal 
to initiate predetermined sequenced operation via interlocks or time 
delays at the support as mentioned above. 
The pre-energisation feature may be applied to a conveyor pushing operation 
preceding the support advance proper and this feature of the invention 
concerns taking up any play in the support to conveyor linkage prior to 
measuring the ram stroke and producing corresponding signals, say using a 
ram pressure sensor for enabling or resetting purposes.

A mineral face 10 is traversed by a mining machine 11 between a main gate 
12 and a tail gate 13. As shown, the mining machine 11 is cutting on a 
traverse from the main gate to the tail gate. Cutting may also take place 
for the opposite direction of traverse, or idle return runs may be made. 
The mining machine 11 is associated with a face conveyor 14 to which a row 
of self-advancing mine supports are attached by double-acting hydraulic 
rams 16 for pushing the conveyor towards the face 10 and subsequently 
pulling lowered supports successively up to the face conveyor as indicated 
at the left hand side of FIG. 1, and so to form the familiar snake of the 
face conveyor. The supports are raised to engage the roof so that in this 
way, the roof of the face is left unsupported for a minimum length of 
time. The face conveyor 14 is shown feeding a conveyor 17 in the main gate 
for transporting material away from the face. A similar conveyor will be 
provided in the tail gate if cutting is to take place on both directions 
of traverse of the mining machine. 
The supports 15 are shown with interconnecting multi-core cables 20 which 
form part of a communication network between a remote control unit 25 and 
support-mounted units indicated in FIG. 2 by the numeral 26. The remote 
control unit 25 includes command circuitry 28 for supplying coded command 
signals controlling sequential advances required of the supports 15, and 
will normally comprise a parallel operating, word organised, micro 
computer system. These will be transmitted over the multi-core cables 20 
to support units such as shown at 26 and 27 for supports that, 
respectively, do and do not push the face conveyor. 
For convenience, it is assumed that coded control or data words are 
transmitted bit by bit in series over one of the lines of the cables 20. 
In practice, different lines may be used for the different directions of 
transmission, with other lines serving for power supplies, clock pulses, 
emergency warning signals, and audio linking, etc. Alternatively, data 
and/or control signals may be transmitted in parallel, say a byte at a 
time over groups of the lines of the cable 20. For the preferred serial 
mode, some form of word assembler, such as a serial-to-parallel converter, 
may be required at the input at each of the units 26 and 27 as these will 
normally be parallel operated, word organised, data processing units, with 
means performing the opposite function for transmission in the opposite 
direction. 
The supports units 26 and 27 are each shown as including a decoder 30. For 
the unit 27, decoder 30 is operative to supply control signals over line 
31 to a control solenoid 32 for ram action to pull the associated support 
up to the face conveyor, and a signal on a line 33 enabling output from a 
pressure detection device 34 for indicating that the hydraulic props of 
the support are pressed against the roof of the mine working. 
In the case of the support units 26, similar functions are controlled by 
its decoder 30 as indicated by the use of the same reference numerals. In 
addition, however, decoder output line 36 is also shown connected to a ram 
control solenoid 37 for controlling the application of pressure-fluid to 
push the face conveyor towards the mineral face. A further decoder output 
line 38 is shown for enabling outputs from a ram extension sensor 39 that 
is assumed to provide a digital output, say by a digitiser from a 
potentiometer-based device. 
In practice the two support units 26 and 27 may well be identical with the 
additional decoder outputs 36 and 37 not used for every support, though it 
may be preferred to use a ram extension sensor if desired. For convenience 
of description it is assumed that the ram extension sensor is operative 
relative to a preset so that it supplies signals which represent an error 
in relation to that preset. Alternatively, of course, the total ram 
extension would be transmitted to the remote control unit. 
The remote control unit 25 is shown as including an adder 45, normally the 
computing arithmetic and logic unit of a micro processor system, with 
parallel input lines 46 enabled by a control line 47 from the command 
means 28 when ram extension data is being received. Outputs 48 of the 
adder 45 are shown feeding a multi-word store 49 normally part of the 
memory of a micro-processor system, which is addressed over lines 51 
according to which support is being controlled at any particular time as 
determined by the enabling line 52 for controlling up dating of the store 
addressing facility during an addressing phase when a mine roof support is 
selected, for example, using a counter. 
The store 49 is also shown supplying the adder 45 over lines 53 so that the 
adder serves to accumulate the present contents of a particular word 
location of the store with the error or total extension signal for the 
current advance operation. 
Lines 53 are shown branched at 54 to feed a visual display unit 55 so that 
information regarding accumulated errors can be displayed either 
individually for each mine roof support, or simultaneously for a plurality 
or all of the mine roof supports. 
In FIGS. 3 and 4 the local support control unit 26 is shown as including 
electrical means for ensuring that play is taken up in the advancing ram 
linkages before a support is released from the roof and pulled up to the 
face conveyor thereby ensuring that ram extension data is more accurate. 
For double-acting roof supporting props the solenoid 40 may control only 
lowering of the support canopy, or raising too depending on its 
energisation state and may be suitably interlocked with the other 
solenoids, or by pressure fluid control valving for automatically 
advancing on an advance command. FIG. 3 shows a time delay device 42, 
which could be digital, say a counter responsive to cycles of the remote 
monitoring unit, or analogue, say an RC network. In its simplest digital 
form, the delay may be a monostable or bistable device responsive to a 
subsequent signal from the remote monitoring and control unit. 
The timing device is shown connected in the advance ram solenoid energising 
line 31 after branching to the roof support ram solenoid energising line 
43. 
FIG. 3 also shows the roof pressure detector 34 for supplying signals to 
the remote control unit on interrogation by energisation of decoder output 
line 33, and the ram extension sensor 39 that is assumed to provide a 
digital output sampled by decoder output lines 38, though an analogue 
output could be digitised within the unit 26. The roof solenoid line 43 
from the delay 42 is shown branched at 44 to the sensor 39 to zero or 
reset the latter or, for a pulse producing sensor, enable its pulse line. 
FIG. 4 shows an alternate arrangement in which a device 60 responsive to 
pressure in the advance ram is indicated as providing a signal for 
enabling a coincidence gate 61 between the advance solenoid and roof 
support solenoid lines 31 and 43. 
Alternatively, of course, as will be described in FIG. 5, there may be a 
pressure-fluid servo interlock between the support advance ram and the 
roof support ram to achieve the energisation of advance ram and the roof 
support ram to achieve the energisation of advance rams prior to lowering 
the support canopy. 
Clearly, a remote monitoring and control unit could be arranged to send 
over lines 20 separate advance solenoid energising and roof support 
solenoid energising command signals with a desired delay or a logic 
interlock dependent upon feed-back of pressure detection signals. 
Alternatively, a fine read-out of the advance ram extension could be 
provided, and the roof support lower signal sent only after the fine 
read-out signals had remained steady for a predetermined number of cycles, 
perhaps only one, of the remote control means. The latter operation would 
be temporary and would not result in accumulation to existing ram 
extension data at the control unit. 
Other embodiments could utilise ram-extension measurement on pushing over a 
face conveyor prior to advancing the support itself. Then both of the 
above techniques specifically described, i.e. time delay or ram pressure 
sensing, could be used for getting signals to the remote control unit, but 
the requirement for interlocking with roof support ram release would not 
exist. 
In the pressure fluid interlocked system of FIG. 5, the conveyor 
pushing/support advancing ram in indicated at 65 and the roof support 
props at 66 with appropriate non return valves to ensure safe operating 
conditions. A pilot operated control valve 68 for the ram 65 is shown as 
having drive and drain states for support advancing i.e. retraction of the 
piston or ram 65, with a safety bias to the drain state. In the drive 
state shown, pilot pressure is applied via branch line 69 when the support 
advance signal is received and operates the appropriate solenoid valve. 
The build up of pressure in the ram 65 will take up play in the mechanical 
couplings by the time a predetermined pressure is reached therein. This is 
sensed by a valve 71 with a preset or presettable bias so as to move from 
the position shown to its other position and cannot pilot pressure fluid 
over line 72 to a prop control valve 74 shown in its prop energising state 
and moved therefrom by such action of the valve 71 to cause connection of 
the rams to return for positive retraction if desired. 
It will be appreciated that the pressure sensitive valve 71 could be 
connected anywhere in the supply line to the advance side of the advancing 
ram 65 and still sense the appropriate pressure to cause pilot operation 
of the valve 72, i.e. without requiring a separate connection to the 
cylinder of the ram 65. It is also to be understood that where, as often 
is the case, the pilot and main supplies are taken in common from one 
source, the pilot arrangement of the valve 72 may be made directly 
pressure sensitive so as to itself to provide the desired operation at a 
predetermined pressure.