CA1095939A - Remote control system for mining machines - Google Patents

Abstract

REMOTE CONTROL SYSTEM FOR MINING MACHINES

Abstract of the Disclosure An intrinsically safe system controls all miner hydraulic and electrical functions from a hand held miner remote control pendant. Pendant control devices provide on/off control signals to interfaces with miner drive and pump controllers, as well as a group of ? 6 VDC differen-tial proportional and on/off control signals to respective electronic valve drivers. Valve driver outputs are fed to respective force motors on pilot stage valves which control each hydraulic function. Each valve driver output is modified by offset and dither signals to overcome power stage valve dead band and frictional characteristics.
Pilot stage valves have an internal feedback sleeve coacting with a pilot valve spool in a hydraulic servo circuit.
Pilot stage valves operate in a pilot oil system which may be isolated from power oil systems.

File 5623-A-2 G. G. Dower -1-

Description

Background o~ the In~ntion . Fle}d o~ the Inve~ntlon Thi3 invention relate~ broadly to underground m~ning machlne~, and more particularly to remote control systems ~or underground mlnlng machine~. The invention 5 1, may be used in an underground cont;~nuous miner a~ de~crlbed hereln, or used in other mlnln~ machines such as conveyor-bolters and the llke.
~¦ In underground coal minin~ ~ac~llties, ~or .1 ex~mple, there has been a long need to incre~se coal pro-¦ ductlon~ minlng ef~iclency and operatin~ sa~ety procedures.
One way to lncrease coal productlon and mining ef~lclency j with contlnuous miners ln both new and exi~ting coal mine~
¦ is to permit the continuous miner to take deeper cut~ 1l 1l be~ore moving to a new mlnin~ site. Tb1s practice~ howe~er, I
15 l¦ sub~ects the human operator of conventional contlnuou~
1~ mlner~ and con~eyor-bolters to undue hazards rather than increasin~ operatin~ 3afety procedures.
It has been ~ug~ested that one way to achleve ~1 increased coal production9 mining e~iciency and operatin~
20 ~¦ 3afety ls to mak~ the deeper cuts with continuou~ mlners andJor conveyor-bolters operatlng under ~ontrol o~ a remo~e control system. However~ those minlng machine manu~ac- I
Il turers that may build mining machines with a remote control Il ~yste~ do so to provlde a ~ervice-rellable packa~e tha~
25 I wlll ~lth3tand the severest electrlcal hazard and other mlning envlronmental condltions~ but at the expense of operatln~ ~lexibillty.

-2-For e~ample, one prlor art remote control ~y~tem may include ba~ic features of an on/o~r control in ~he electrlcal and ~olenoid controlled hydraulic systems.
Il Another may o~fsr complex stepwl~e control o~ certain 5 I funct~ons, but thi~ i3 no~ a true proportional control system. Such baslc and stepwise control systems are listed by the U- S. Dept. of Labor, Mlne Sa~ety and ~ealth Admintstratlon (MSHA), as "permi~lblet'. That i8, electrical I and~or control ~ystems whlch operate a' energy le~el~
10 1l ~ur~iclent to ignite a methane and alr m~xture are permitted j in mines lf contained in heaYy metalllc exploslon-proof I enclosures and/or other mean~ to sa~ely handle electrlcal I hazards sometlmes present in mlnes ln the form of an ~ explo~lYe mix~ure of methane gas and alr.
15 l~ Other de~iciencies ~n ~he prior art minlng machlne remote control system, in additlon to that of lacklng true proportlonal control ~eature~, include the absence o~ MSHA
l~sted "intrinsically safe" electro-co~trol ~alves and I¦ controller~ ~or both proportional and onfoff ~luid control 20 l,~ functlons. That ls, electrlcal control ~y~tems whlch operste at low ener~y le~els are con~ldered "intrinslcally safe" and permltted ln mines ln nonexploslon-proo~ enclo~ure~
if the electrical energy released by the control c~rcuit is I¦ not surrlclent to i~nite an explosl~e ~ixture of methane and 25 l~ alr. Thl3 classlflcatlon i8 in contrast to MS~IA "permi3sible"
de~ine~ above and 1~ attainable permits much slmpler control hou~ln~ and wlrlng requlrements, in addition to reducing maintenance pro~,rams and per~onnel requlrements as compared to "permisslble" ~ystems.

~5~j3~q ,, Additional deflciencies ln the prlor art ~lnlng macAlne remote control ~y3tem8 are attribut~ble to thelr lack o~ applicabllity to all coal minlng machines; their I inablllty to be retro~itted into e~xl~tlng minin~ machines;
5 1l their lack o~ o~ferin~ a llght-weight control console; t~eir ! susceptibillty to control valve contaminatlon and sub equent l~ malfunction; and~or their inability to be ea~ily repalre~
¦¦ under~round.

I Summary o~ the Inventlon 10 ll A maln ob~ect of the present in~ention i~ to ~! provlde an i~proYed remo~e control sy~tem for mlnlng machln~s ~hich ~ill overcome the aroresald deflciencies in the prlor I art.
l Another ob~ect o~ thls lnventlon 18 to provlde an 15 1 i~proved remote control system ~or minin~ machlnes which results in lncreased production, ~ining erflclency, operatlng safety and reliablllty.
The ~oregoin~ obJects may be achleved by an lntrin-11 sically sa~e, universal, mine-worthy re~ote control ~ystem 20 !~ for m1nln& machines havlng both electrical a~d hydraullc sys~ems whereln there 13 lncluded banks of proportional and ¦ on~of~ electro-control valve~, each havin~ an lntrln~ically safe pilot stage force motor, an lntrinslcally sa~e low lll voltage power ~upply, a hand-held remote control pendant 25 l~, cabled to trall the mining machlne and provlded with pro-portlonal and on~o~r control devlces whlch ~enerate low i voltage slgnal~ ~or rontrolling all elec~rical and hydraullc runctlon~ on the mlnlng machine includin~ half-tram speed, a ~roup Or dlrr~!rentlal electronic electro-control valve s~

drlver~ each receiving a dlf~erent propor~ional or on/of~
control slgnal rrom the pendant for energizlng differentially a reapective ~orce motor, eacn valYe drlver di~ferential ,, output ~i~nal being mo~i~led by offset and dither component~ !
5 .I to overcome valve dead band and ~rlctlon, al o solid-state ~, ~achine lnter~ace clrcuitry for u~in~ low volta~e control device~ to csntrol high volta~e machine pump ~nd cutter drive ~unction~, and remote~manual and interfac~ ~est switche~.
, mhe pre~ent remo~e control system i~ made intrln~i-lO l cally sare ln an exploslon-proof enclosure by tran~ormin~
450 YAC hi~h Yolta~e to a lower volta~e which energi3e~
, sQl~d-~tate rectlfler~ that produce - 7 ~D~ low volta~e jl sources ~hich ~re pas3ed throu~h re~pectlve protective Il barrler network~, thereby establis~ing a low voltage power 15 ,ll source havin~ - 6 VDC output~. Al~o hou3ed in another Il exploslon-proof enclo~ure are hi~h voltage pump and drlve I motor controllers and the machine lnterPace circuitry. ~he ¦ low voltage valve dr~vers and related circul~ry, each pllo~
¦ valYe ~orce motor~ the remote~manual ~wltch and test ~wi~ches 20 l¦ are housed ln re~pectlve nonexplo~ion-proof housings, there~y impli~ying the remote control ystem de~l~n, C05t, installatlon and maintenance requirement~. ' Universality of the present remote control sy~tem 'I 13 achieved in part by open-center clo~ed-center, ~anual-25 ,, override, electo-control valve~ dri~en by a respective ~orce mo'or in both proportional control and on/off electro-control valve ba.nk~, eac~ val~e beln~ a dl rec~ sub~titute ~or exl~tin~ manual valves on man~ ~ypes o~ ~ining machlnes.

,j _~_ In addition, the remote control pendant 13 provided with , control devices havlng one low volta~e output and all valve ' drlYer~ are o~ one de~ign and con~structed on plug-in clrcu~
boards ~or interchangeabllity wlthln their enclo~ure. Those 5 1 unl~er~al festure~ make the present remote control system I capable of being retro~ltted into existln~ manually controlled ,~ mining machines.
The present remote control sy~tem i~ mAde mine-I worthy ln part by spec~al hydraullc features relat~d to 10 ll resi~tance to heat, dirt and vlbration in electro-control i val~e~ whereln pilot ~ta~es are re~ ~ro~ a rlltered and cooled pilot sta~e oil source completely lsolated ~rom a po~er ata6e oil source whlch ~eeds po~er sta~e~ coupled ~o ~ pilot sta~es in electro-proportional control ~a~ves. In 15 1 addition, each pilot stage is proYided with an lntr~nsically sare rorce motor coupled to a pllot spool which operat2s wlth a mechanical ~eedback sleeve ln a hydraulic ser~o I circutt with the pllot stage pl3ton. Thus, when the force 1~ motor i~ ener~lzed ~ith the val~e driYer di~ferential 31gnal 20, ~odl~ied ~lth of~et and dither components, the pilot stage hydraullc serYo clrcult~ a~ we}l aa the power stage circu~t, ~l 18 considerably less susceptlble to undesirable effects of li dirt and vlbratlon. In addition to these features and Il ~alve lnterchan~eabillty, the intrln~lcally safe leYel of 25 ~I remote control pendant slgnals, valve dr~ Yers ~ force motor~
and ~otor lnterf'ace circuitry ma~e ~t possible to repalr and maintain the present remote control 3ystem in a ha~ardous atmosphere underground ln a mine site. Thi3 is hlghly

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advantageous because of the lost productivity, and increased expense of repairing underground mining machines above ground as is the case of prior art apparatus such as the "permissible" mining machine noted above.
According to a first broad aspect of the present invention, there is provided a mining machine remote control system for controlling one or more fluid-powered machine operating functions, said system comprising:
(a) electro-control valve means for controlling the machine operating functions in response to operating function control signals, at least one valve in said means having proportional flow and deadband character-istics, (b) pendant means producing a separate operator-initiated remote control signal for each said machine operating function, at least one of these remote control signals having valve-related proportional characteristics, and (c) controller means receiving the separate remote control signals for producing the separate operating function control signals, at least one of these operating function control signals having the valve-related propor-tional flow characteristic modified by an offset signal component for over-coming valve deadband characteristics.
According to another broad aspect of the invention, there is provided a mining machine system for remotely controlling one or more fluid-powered machine operating functions, said system comprising:
(a) a pressurized fluid source, (b) electro-control valve means including a hydraulic servo-controlled pilot stage valve for each machining operation function which receives a separate operating function control signal, each pilot stage valve connected to the fluid source and to a load having proportional flow and/or valve deadband characteristics, and (c) remote control means initiated by an operator for the separate operating function control signals, at least one of said signals having valve-relatecl proportional flow characteristics and/or modified by an offset signal component for overcoming the valve deadband characteristic.

_7 ~

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According to yet another broad aspect of the invention, there is provided a mining machine system for remotely controlling one or more fluid-powered machine operating functions, said system comprising:
(a) a pressurized power fluid source susceptible to contamination, (b) a pressurized control fluid source isolated from the power fluid source, (c) electro-control valve means including a hydraulic servo-controlled pilot stage valve for each machine operating function which receives a separate operating function control signal, each pilot stage valve connected hydraulically to the control fluid source and coupled mechanically to a corresponding power stage valve which is connected hydraulically to the power fluid source, at least one power stage valve having proportional flow and deadband characteristics, and (d) remote control means initiated by an operator for producing the operating function control signals, at least one of said signals having valve-related proportional flow characteristics modified by an offset signal component for overcoming the valve deadband characteristics.
The invention will now be described in greater detail with reference to the accompanying drawings, in which:
FIGURE 1 is a plan view of a continuous miner which incorporates the present invention.
FIGURE 2 is an elevational view of the FIGURE 1 continuous miner.
FIGURE 3 is a block diagram of the combined electrical and hydraulic systems of the FIGURE 1 continuous miner.
FIGURE 4 is a schematic cross-sectional view of an electro-hydraulic control valve having a force motor driven pilot stage, a power stage and a manual override Eeature as used in the present invention.
FIGURE 5 i5 a graph representing the FIGURE 4 valve power stage output flow vs. power stage spool position and force motor voltage require-ments, and illustrates ofEset or pretravel and dither signals required to overcome power stage valve deadband, frictional characteristics and con-taminant effects.

-7a-FIGURE 6 is a block diagram of an intrinsically safe low voltage power source used in the present invention.
FIGURES 7A and 7B are electrical schematic diagrams showing a portion oE the miner remote control pendant, inter~ace controls and high voltage (H.V.) pump and cutter head drive controls.

-7b-FI~S. 8A and 8B are electrlcal block ~la~rams of the remalnln~ portlon of the mlner remote contrsl pendant, low volta~e val~e con~ro].3 and proportlonal and ~l on~o~ banks Or electro-control ~alves which per~orm hydraulic control ~unction~.
~ IGS. 9A-9D are electrical schematlc dia~r~mq of ~arlous proportlonal and o~ofi~ control de~lces u~ed , in the mlner remote control pend~lt o~ the pre~ent lnventlon.
FIG. 10 1~ an electrical sche~atlc dia~ram o~ the 10 I dirrerentlal ~al~e dr~vers u~ed to power a force motor on a ,I pllot stage valve ln response to, ~or ex~mple, a dl~erential proportional control device, the ~alve driver having of~et i and dither reatures ~or ~roduclng an output si~nal charac-~ terized in FlG. 5.
15 " FIG. 11 13 an electrlcal ~chematic diagram o~ a tram half-speed clrcuit used ln the present lnvention.

De~criptlon o~ the Preferred ~mbodiment Referring no~ to the drawlngs J particularly FIGS-ll 1 and 2, there i4 shown miner 20 exempllfled a~ a Lee-Nor~e 20 1I Co. continuous mlning ~achlne ln an underround coal mine haYlng a coal 8eam 21. Miner 20 include~ a miner ele~tri~al ~ystem 22 and a miner hydraulic system 23 shown diagram-matlcally ln FIG. 3 and i~ modi~ied to be remotely controlled Il rrom an lntrinsically ~areS hand-held miner remote control 25 . pendan~ 25 by way of cable 26 trRlling mlner 20 a ~afe dlstance. Wlth the trailln~ pendant 25, deeper than traditional cuts may be sa~ely made into coal seam 21 by "

o~erator 24 before mo~lng min~r 20 to a di~ferent mine ~lte.
A traditlonal manual operatin~ positlon not shown i~ ~ar more hazardou3 and offers le~ controllability of miner 20 , because operator 24 l~ normally couched at the rlght rear 5 I corner of mlner 20 between machinle upper and lower extremlties while plying coal ~rom seam 21.
¦ ~qiner 20 includes chas~is 27 whlch i~ ~upported by le~t tram 2~ and right tram 29 whlch are dri~en by hydraulic ~ motors not shown. Chassl3 27 plvotally supports cutter boom 10 i' 30 which l~ po~ered by a hydraullc cyllnder not shown ~o ! ~e raised from a down po~ition 31 to an up positlon 32.
Cutter boom 30 piYotally Yupport~ le~t cutter head 33 and ri~ht eutter hesd 34, each bein~ dri~en by a separate high i voltage electrlc ~otor 35, 36, re~pectively, and both move~ !
15 I Yertically wheneYer cutter boom 30 is rai~ed and lowered.
~il L~ft and right cutter heads 33, 34 are mounted on pl~otal cutter head arms 37, 3& which are caused to 03cillate ll~ horizontally in uni~on from thelr inward positons 39, 40 ¦I to thelr outward posltions 41, 42 by a ~ydraulically powered 20 ,~ mech~nism not shown but dl~clo3ed, for example, in U.S.
i Patent No. 3,460,o68 to T.Luk~ich. In thi~ manner, coal i seam 21 is mined to a width Ereater than the nominal wldth ~ o~ ~lner 20, and wlth the hydraulic mean~ ~or ralsin~ cut ~er ¦ boom 30 to posll;ion 32 the coal seam 21 i~ mlned to a helght 25 ' 43 which is gre~ter than the nominal hei~ht of miner 20.
Al~o pivotally supported fro~ ~lner cha~sls 27 gathering pan 44 whlch ha~ a hydraulically powered mechanism not ~own for ~atherlng coal cut from seam 21.

_g_ ~:9t5~

Gathering psn 44 18 ralsed and lowered between its down po~itlon 45 and its up po3ition 45 ~y a hy~raulic cylinder not shown. Coal gathered by pan 44 s~ red to conveyor 47 !I whlch ls powered ~or r~versible operation by a hydraulic 5 motor not ~hown. Conveyor 47 ls plvotally ~upported from , cha3~1~ 27 and is raiqed and lowered between lts do~n poslt1On Il 48 and up posltion 49 by a hydraulic cyllnder not ~hown. In 'i addition, conveyor 47 tall 1~ pl~oted to swlng horlzontally from lts center po~ition 50 ~o lt~ le~t or ri~ht positlon~
10 l 51, 52 by another hydraulic cyllnder not 3hown. In th~ 9 manner~ coal cut from seam 21 may be di~charged rearwardly from conveyor 47 at a ~ar~ety o~ eleYation~ and in a varlety o~ dlrections wlthin seam 21 onto a bolter-con~e~or not Il ~hown.
15 li If, du~ln~ the course of mining ~eam 21, mlner 20 i¦ develop~ an unstable operation force condition3 3tabillzing il ~ack 53 may be lowered ~rom chassis 27 to contact seam 21 1l as shown in FIG. 2 by stlll another hydraulic ~ac~ not shown~
I¦ Otherwise, stablli~lng ~ack 53 ~hould b~ retained ln it~
20 ~ u~ward posltion. Al~o durin~ operation of miner 20~ the I custo~ary water spray and water delu~e require~ents are i 9upplied by way of water hose 54, but are con~rolled remotely by ~endant 25 a~ will be desGrlbed below.
!! Miner electrlcal ~Jstem 22 i5 ~ed 460 VAC hi~h 25 . voltage over power cable 55 to e~plo~lon-prool enclo~ure 56 from whlch lt ls distrlbuted to hi~h Yolta~e motor controllers and other de~lces not shown in FIGS. 1 and 2 but shown dlagrammatically in FIG. 3. Included are electric ~' 10 drive motors 35, 36 ror drlYing cutter hea~3 33, 34, respectlvely, which, ln additlon to electr~cally driven , pump~, are the only loads having direct electrical drive, ` In miner hydraullc system 23, electric motor 57 5 'l drives dual constant volu~e hydraulic pumps 58 and electrlc I, motor ~ drlv~s a varlable volu~e hydraullc pump and 3ytem 60. Hydraullc pumps 58, 60 are connected to a main ba~c o~
proportional electro-hydraulic control valves 61, to an I aux li~ry bank of on/of~ electro-hydraulic control valves 10 , 62, and to other load& not shown in FIGS. l and 2, but shown dia~rammatically ln FIG. 3.
Rererrlng now to FIG. 3, the mlner electrlcal system 1 ~2 lnclud~ high volta~e being ~ed ~rom power ~ource 55 over .I cable 63 to hi~h volta~e pump and drive motor controller 64.
15 ll In addltion, high volta~ i8 ~ed over cable 65 to an elght-j oole remote/manual switch 66 which determine~ whether miner 1 2~ i~ to be operated in either remote or ~an~al mode as will !, be explained below. High voltage ~rom remote/manual ~witch 1 66 19 ~ed over cable ~7 to the input of low volta~e power 2C 1~ source 68 whlch~ as shown in FIG. 6, produces an lntrin~ically I ~are + 6VDC low voltage output on cable 69. Thi~ low voltage i source is fed to mlner remote control pendant 25~ low volta~e inter~ac~ csntrol~ for hi~h volta~e tH.~.~ ~otors 70, and ~ low voltage controls ror electro-valve~ 71, all as shown ln 25 Ij FIGS. 7A, 8A and 8B and descr~bed below.
Rererrlng to remote~manual ~witch 66 al~o 19 invol~ed ln start and stop functions Or the high ~oltage motors noted above by ~ay of cable~ 72, 73 to and ~rom .1 ~

5~J~
i -interface controls for hlgh voltage motors 70. Inter~ace control3 70 provl~es low volta~e ~i~nals related to pu~p I dump control on cable 74 and tr~m half-speed control on ; cable 75 to low volta~e control for electro-valves 71 5 I descrlbed below.
Miner remote cQntrol pendant 25 has two control deYices whlch generate in~rlnsically sa~e low Yoltage on/orr slgnals, one for pump drive3 and the other ~or cutter drives.
i These on/of~ signals are fed over cable 76 to lnterface 10 . controls lO where solid state relays con~ert them into high voltage start and stop si~nal~. ~ne ~tart and stop signals are over cable 77 to control hi~h voltage pump and drlve ,l controller 64. Con~equently, pendant 25 intrinsically sa~e Il low voltage on/off control signals cause high Yoltage 15 1¦ controller 64 to remotely ~tart and stop pump motor~ ~7~ 59 through cables 78, 79, and le~t and rl~ht cutter head drlve ~otors 35, 36 through cables &0, 81. Test switches 82 veri~y solid state deYlce act~vity in inter~ace control~ 70 ,~ by prov~ding manual local hl~h voltage start and ~top control 20 !I signals ~or controller 64 by way o~ cables 83~ 84. Circuit ;I details ~or remote control of pump and cutter head drive motors ~rom pendant 25 are shown ln ~IGS. 7A and 7B.
¦ Miner remote control pendant 25 also has fourteen I control deYices which ~enerate fourteen ~ntrinsically sa~e 25 l low ~olta~e dirl~erential proportional and on~of~ control signals representing ~ourteen re~otely controlled hydraullc I runctions on mlner 20. Pend~nt Z5 control device circuitry is shown ln FIGS. 9A-9D. A first rroup o~ slx dl~erentlal ~.

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proportional control i~nals are applied to cable ~5 and a second group of eiæht di~ferential on~o~ control slgnals I r are applled to cable 86, both ca~les belng connected to ' low voltage controls for electro-valves 71. Cables ~5 3 86 5 ;1 and 69~ 76 comprlse pendant trall~ng cable 26 mentloned above.
Each of the ~ourteen control signals ~ed over il cables 85, 86 ls connected in device 71 to an input o~ a i'l di~rerent one of ~ourteen intrinsicall~J ~are electronlc 10 il dlfferential valve dri~ers o~ e desi~n. ~ach valve ~rlver dif~erential lnput is clrcuited to sum the propor-~ional or on~off sl~nal with both an internal o~r~et si~nal component initlated by monitorln~ pendant control po~itlon Il and an lnternal dither 31gnal component. In this manner, 15 1l each val~e driver di~ferential output signal ~s modi~ied by of~set and ditner components to overco~e valve dead band and f~ietional characterlstics as well as contarllnation e~fects. FIG. 10 ~hows the valve drlver circuitry. I
Each valYe driver in device 71 1~ lncluded ln one 20 11 o~ the control channels } to 14 whlch correspond ~o ~ourteen mlner hydraulic control ~unctions dla~rammed in FI~S. 8A and 8B. Control channels 1 to 6 haYe proportlonal valve driver output signal~ applled to cable 87 and control channels 7 to 1 14 have on/o~f valve driver output sl~nals applied to cable 2~ 9' Cable~ 87, 88 are connected to intrin3ically sa~e low voltage di~erentlal force motors associated with control channels 1 to 6 and 7 to 14 a~30ciated with electro-control valve banks 61, 62, respectlvely.

1, ~

~, MINE~ DRAULIC S~S~
Still re~erring to FIG. 3, miner hydraulic system 23 includes dual constant Yolume hydraullc pumps 58 dri~en '1 by electrlc motors 57 and variable volume hy~raulic pump 5 , and system 60 drlven by electric motor 59. Dual pumps 58 i const 8t 0~ isolated pilot oil pu~p and ~y~tem 89 havlng supply (S) and return (R) lines QO, 9l, and a power oil system ~2 ha~ln supply ~S) and return (R) lines 93, ~4.
1l Var~able ~olume hydraullc pu~.p and syste~ ~0 has ~upply (S) 10 l¦ and return (R) line8 95, ~Ç, and dump control (D) line 97 ~or relieYing pump pres~ure be~ore ~tarting motor ~9.
Pilot o~l sy~tem ~9 13 completely isolated rrom all other oil systems in miner hydraullc sy~t~m 23, thereby I¦ mlni~izing seYere contamlnation effects caused ln prlor 15 ~ art remote ¢ontrol sy~ems ~hlch normally used a mir.er power oll sy~te~ ~or both power and control valv~ supply and return I¦ source3. In t~e present isolated pilot oil system 89, ¦~ ~yste~ filterln not shown is provided ln both su~ply and I -i¦ return llnes 90~ 31 to keep contaminants at a min~um level 20 ~ here thelr e~ects are predicabl~ and theref'ore acco~ltable Il in valve driver constru&tion. Also not ~hown ~or each I, isol~ted pilot O:L1J power oil and ~ariable ~rolume hydraulic y3tem 80, ~2, 50 are val~ln~, ~anks, oil coolers and the ~I like as required to provide separate respective hydraulic 25 1 systems on miner ~0.
Main ~alve bank 61 cont~ln~ proportional electro-control val~es 9S to 103, each havln~ a pilot ta~e 104 coupled to a ~ower 3tage 1~5 which ls coupled to manual ~S~3~

override 106, all a9 shown ln FIG. 4. . Pilot sta~:e 104 includes a differential ~orce motor not shown in FIG. 3 which receives a dif~erent one o~ the v~lve driv~r propor-I tlonal output s~gnals o~ cable 87. All si~ pilot stage 10~
5 ~I supply and return port~ ~re ~anifolded to laolated pllot oilsupply and return lines 909 91. All six power stage . pressure and tank ports are ~eparately manlfolded to varlable volume system supply and return lines 95, 96. ~lectro-con~rol valvea 98-103 are connected dlrectly to proportionally 1~ ¦ controlled hy~raulic loads 107, llsted in TABL~ 1 below~
which are powered t~rough a plurality of supply an~ return j line~ shown slmply as line~ 10~, 109.
Auxlllary val~e bank 62 contains el~ht pilot l on/ofr valves 110-117, each having a pilot stage llke pilot 15 ¦ stage 104 and a manual overrlde 118 like manual oYerrlde 106. ~ach pilot ~tage lncludea a dlfferentlal ~orce mo~or l whlch receives a di~feren~ one of the ~alve driYer on/o~f ! output ~i~nals on cable &8. Seven of ei~ht pilo~ sta~e .
~1 supply and ret~rn ports are manlfolded to constant volume 20 1¦ power oil jys~em supply and ret~rn lines ~3, 94. ~he ei~hth ¦I pllo~ s~age supply and return ports are co~nected to varlable olume dump (D) and return (R) llnes 97, 96 ~o relieve nydraulic pressl~e on pump 60. Electro-control valves 110-¦1 117 haYe their pilot 3tage spools connected to other 25 ~ nydr~ulic valve.~, m~chanis~s, cylin~ers and the llke required ¦ for on/ofr controlled hydraulic loads 11~ also llsted inTABLE 1 below. These load~ are powered throu~h a ~lurality of supply and r~turn llnes ~hown 3imply as lines 93, 120, 33~3 i TABL~ I
¦ Control ~lectro-Channel Control Miner Hy~aulic Control No. ValYe No. ~alve Function I
5l PROPORTIONAL CONT~OL
1 98 Cutter Boom 30 - Up 32/Down 31 l 2 99 Con~eyor Lift 47 - Up 49/Down 48 I 3 100 Con~eyor Tail Swing 47 -~ Le~t 51~Ri~ht 52 lQ ! 4 101 Right Tram 29 - Forward~Reverse 102 Le~t Tr~ ~8 - For~rd~Re~erse 6 103 Gatherin~ Pan 44 -Up 46~Down 45 ONfOFF C0NTROL
~ 7 110 Variabl~ Volume Pump 62 -15 ¦ Dump Con~rol 97 ¦ & 111 Cutter Xaad 33, 34 O~cillator -On/O~
112 Stabllizlng Ja~k 53 - ~p/Down 1 10 113 ~aln Water Sprays - 0n/O~r 11 114 Water Deluge - 0n/O~r 12 11~ Conveyor 47 Ru~ - On~O~f .
13 116 Tram Half-Spe~d - High~Low 14 117 Conveyor 47 Dlrection -ForwardJReverse Turnlng now to FIG. 4~ there 18 ~ho~n in schematlc cross-3ection a typ~cal proportlonal electro-control ~al~e I 98-103 having h~draullc ~ervo-type pilot 3ta~e 104~ a power i stage 105 and a manual o~erride 10~, all mechan$cally coupled ~ together. ~or ~implicity of lllustratlon, detail~ o~ valve 3ol or 3hart seal3 or other manufacturin~ detail~ are not shown.
Inclucled in hyc~aullc servo-type pllot stage 104 is an intrlnsically ~a~e di~ferential force motor 122 having a dl~erential electrlcal coil 1~3 and a vertically movln~

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'I

5Y i~

armature 124 which cooperates with coil 123 from a center l or neutral deener~ized po~ltion a~ sho~m. Coil 123 ls ~¦ rated at - 10 VDC and ls equlpped wlth ~lack (B) and whlte (W) ,I termlnals which receive one of th~ dl~rerential proportional 5 ~ drl~er output slgnalY on cable 87 mentioned above. Dif~eren-tial operation occurs when B~ and ~l-, armature 124 moves upw-ard fro~ the neutral poRitlon; ~hen ~- and W~ armature 124 moves downward from the neutral positlon.
l Hydraullc servo-type pllot Rtage 104 al~o include3 a pllot valve body 125, a supply port 126 and a return port 127 bein~ connected, through mani~oldin~; not shown, to respective i~olated pilot oil supply and return line~ 90, 91 shown ln FI~. 3. Supply port 12~ is connected throu~h ~llter ~creen 128 to ~upply pa~sageway 129 which lead3 to 15 l a ~ertical pilot ~pool bore 130. A mechanlcal ~eedback sleeYe 131 slidably ~itted ln vertlcal p~lot spool bore 130 has a lower cone end 132 biased by sleeve spring 133 ag ~nst pilot plston 134 at a central reglon of ~eed~ack ~ -l cone 135.
20 ¦ Pilot pl~ton 134 is prov~ded wlth pull and push p~lot pl~ton heads 136, 137, re3pectlvely, whlch are slldably ~ltt~d in horl30ntal pilot plston bore 13~. Op~o~in~ ~aces of pull and push plston head~ 136, 137 co~municate throu~h respectlve ~ir~t an~ second control pas~ageways 13~, 140 to 25 l opposlte acting :regions of ~eedback sleeve 131. Ad~acent faces o~ pull and push piston heads 136, 137 co~munlcate directly to return port 127. Pilot plston output connection -17- ~
~ I i 141 transmit~ double acting val~e operatin~ ~orces ~rom pllot piston 134 ln pilot stage 104 to other loads ~uch as power . sta~e 10~.

I In order to produce double acting rorc~s ~ pilot 5¦ pi~ton output connect1on 1419 mechanical ~eedback ~leeve 131 is provided with four ~eedback ~leeve lands 142, 1~3, 144, 145 ~nd three set~ of ~leeve radlal port~ 146, 1479 ~ 1~8 located between the ~our sleeve lands and ali~ned for ¦¦ communication indlvidually with second control passageway 10 ¦ 140, ~upply pa~ageway 129 and ~lr~t control pa~a~eway 139, respectively, durlng pilot staæe 104 operation. Fluid pa~age through the radlal ports and related pas~a~eway~
and lts actlon on pllot pi~ton 134 wl}l ~e de~crlbed ~elow.
Slidably ~itted coaxlally wlth~n mechanical feed-1~ back ~leeve 131 i3 hollow pllot ~pool 149 ha~lng an upper ~ end pinned to force motor armature 124 and a lower end I biased by pllot spool spring 150 agalnst the lnterior cone .
end 132 of mechanical ~eed~ack ~lee~e 131. Pilot spool 149 ls provided with upper, center and lower lands 151, 152, 153, respe~ti~ely, and ~irst and second draln ori~lce~ 1~4, ~ 155 wh~ch are arilled through the wall and lnto the hollow ¦ of pilot spool :149. Fir~t and second pllot control chambers 1~6, 157 are established in the two spaces between center ~nd lower lands 152, 153 and center and upper lands 152, 151, respectlvely.
As ~hown ln the enlarged in~ert o~ FIG. 4, pilot spool center land 152 i 3 30 con~l~ured as to provide first and ~econd ~mall leakage openings 158, 159 w~.ich are Il I

Il -18-~3S.~3~ 1 , equally posltioned with ~eedback l31eeve center radlal port 147 when pi~ot 3pool 14g is in either a neutral or a null po~tion. ~ir~t and ~econd leakalse pa~hway~ are establi~hed I¦ when ~upply rluid entering reedback ~leeve center radial 5l~ port 147 leaka two way That 1~, through leakage openings Il 15~, 159, ~irst and second ~llot control chambers 156, 157, ! fir~t and second drain orl~ices 154, 155~ re~pectively, and into the hollow o~ pilot ~pool 149 where the ~wo leakage l path3 co~bine into one. The ~ingle leaka~e path flows throu~h ~eedback ~leeve radial drain hole~ 160 at the cone and 132 o~ sle~ve 131, lnto pllot piston dra~n chamber 161 between inslde faces o~ pull and push piston head~ 136, 137, ~¦ and then ~lowa to pilot valve return port 127.
~ In addltion~ first and ~econd control pathways 151 are also establlsh~d when supply ~luld entering reedbsck .
sleeve center radial port 147 elther leak3 or rlow~ lnto two other pathway~ in addltlon to the two leaka~e pathway~
that ls, through leaka~2 openlng~ 158, 159, ~lr~t and second ~ pllot control chamber~ 156, 157, rlrst and ~econd control 2011 pa~sa~eway~ 139~ 140 and opposlng faces of pllot piston pull and push pl~ton head~ 136, 137, respectively. Operation o~ the aforesaid pilot stage 104 component~ a3 they a~ect both the leaka~e and control path~ays will be de~crlbed below.
Still re~errlng to FIG. 4 electro-control valve con~truction, power ~ta~e 105 1~ of a four-way valve con-tructlon, including a power valve body 162, a pre~ure (P) supply port 163 and two tar.k (T) return port 164, 165 3~

bein~ connected, through manifoldin~ not ~hown, to re~pective v~riable volume oll ~ystam supply and return lines 95, 96 shown ln FI0. 3. Supply port 16~ leads to a horlzontal power spool bore 166 wherein a power ~pool 167 i3 slideably ~itted in a~ial allgnment wlth ptlot plst;on bore 13~. Power ~pool 167 has an lnput stem 168 coupled to the pilot pis~on output connectlon 141, four axially spaced land~ 16g, 170] 171, 17Z, an output stem 173 and a power spool output~input connectlon ~ 174.
lQ Power 3ta~e 105 out~low is handled by cyllnder 1 and cyllnder 2 port~ 1?5, 176 which are sealably allgned with po~er spool lands 170, 171 when power spool 167 ls ln neutral posltlon as determined by the posltlon of' pilot piston 134. A B+ ~rolta~e on coil 123 in ~orc~ motor 122 causes pilot pi~ton 134 to ~ull po~er ~pool 167 to the left. Inltial le~tward mo~ement or pretraYel o~ power spool 167 elimlnates the offset between ~ace 177 o~ land 170 and leading ed~e 17S
of cylinder 1 port 175, whlle increasln~ the off~et between face 179 o~ land 171 and leadin~ ed~e 180 of cylinder 2 port 20. 176. Addltlonal le~tward movement o~ power 3pool 167 by pilot pl~ton 134 wlll open land 170 and permlt proportional outrlow ~rom supply port 163~ through cylinder 1 por~ 17~, to a proportionally controlled hydraulic load lC7 shown ln FIG. 3. Simultaneously, additlonal le~tward movemen~ of power spool 167 wlll open land 171 and perm.it proportlonal back~low through cylinder 2 port 176 to return port 16~.
A B- ~roltage on coll 123 ln rorce motor 122 cau~e~ pllot pl~3ton 134 to push power s~ool 167 to the rl~ht.

3~

Inltlal rlghtward movement or pr~travel o~ power ~pool 167 elimlnates the offs~t b~tween fa~e 179 o~ l~nd 171 and : leadln~ edge 180 of cylinder 2 port 176, whlle increa~in~
the o~set between ~ac~ 177 o~ land 170 and leadin~ ed~e 178 5: of cyllnder 1 port 175. Additional rightward movement Or po~er spool 167 by pllot plston 134 will open land 171 and permit proportional out~low ~rom supply port 163~ through cyllnder 2 port 176, to the proportlonally controlled I hydraulic loads 107 shown in FIG. 3. Simultaneou~ly, 10, addltlonal rlshtward movement of power spool 167 will open land 170 and permit proportional bac~flow throu~h cylinder 1 port 175 to return port 164.
A zero voltage on ~orce motor coil 123 will cau~e pllot plston 134 ~nd power ~pool 167 to as~ume a neutral 15: po3itlon betwe~n of rsets . l~i8 poslt~l on cau3es spool land~
170, 171 to block both proportional outflow and bac~low through cylinder 1 and 2 ports 17~ 176 to and from external hydraullc loads 107. Conver~ely, a rull B+ or 3- volta~e on force motor coil 123 wlll cause pilot piston 134 to assume 20- a ~ull pull or pu~h posltion and correspondin~ly power ~pool 167 to a full out~low position ~or cylinder 1 or 2 por~s 175, 176. Th~s cause~ a ~ull outflow and backflow thro~gh cylinder 1 or 2 po~ts 175~ 176 to and from external hydraulic load~ 107.
A mamlal overrlde 106 1~ provided ~n each electro-hydraullc control valve ~-103 for use to control miner 20 proportlonal control functlon~ llsted in Table 1 when electronic control si~nals may ~ail~ or when remote/manual switch 66 shown in FIG. 3 i~ placed ln the manual operatlng position as de~cribed below. Manual oYerrlde iO6 lnclude~
a manual hlnge ~ittlng 181 mounted on YalYe body 162. An operatlng arm 1~2 i3 provided wlth one end pivoted throu~h pln 183 in hlnge fltting 1~1 ~nd the other end ~itted wlth a Xnob 184 ~or hand operation.
Included is double-a~tlng ~prlng bia~ mechanl~m 18~ located ln axial alignment wlth horizontal power spool bore 166 and adapted to cooperate with power sta~e body 162 and power spool 167. Double-actins mecha~ism 185 18 enga~ed w~th po~er 3pool end connection 174 and pln 186 ln operating arm 182 to self-center power spool 1~7 to a neutral posltion~
~n pu~h~ng to the lert on knob 184, pilot spool 167 causes out~low through cyllnder 1 port 175 and back~low through cylinder 2 port 176. When pulllng to the right on kn~b la~
` ptlot spool 167 opcrate~ oppo~itely and causes out~low through cyl~nder 2 port 17~ and bac~flow through cyl~nder 1 port 175.
~h~n knob 184 i~ relea~ed, or no e~ort applied thereto, ~anual oYerrlde 106 cau~es the four-way val~e actlon o~ power s~age 105 to return to a center neutral posltion.
Re~err'Lng to FIGS. 3 and 4 J pilot on/of~ electro-con~rol ~alves 1:10-117 in auxiliary ~alve bank 62 perform the channel 7 to 14 mlner hydraullc on~o~ control function~
113ted in TABLE ~ ach pllot on~of~ electro-control valve 110-117 bas ~he same construction and operatln~ ~eatures a~ the FIG. 4 pl.lot 3tage 104 de~cribed above with two exceptions mentlloned below. Each force mo~or 122 electrical input slgnal i3 derlved from cable 8aJ

-22- :

J~

A3 for the fir~t exception to ~,ilot ~ta~e 104 con tr~lction, there i~ no power stage 105, ~o that manual overrlde 118, which is the same a3 de~lce 106, 19 connected to operate on pilot ~iston 134 in~tead of power spool 167.
5 ~ach pllot pi~ton i~ connected to an external hydraulic load 60 and 119 and may have a ~tem extended ~or this purpose.
3econd, on pilot on~of~ electro-control valve 110 ~upply and return ports are connected to vsriable voluDIe pump and sy3tem 60 dump control and return llne~ 97, 96, r~spectively~
to relieve pump pres~ure durlng startlng of electric motor 59. The remalning pilot on/o~f electro-control ~alve~
117 have their ~upply and return port3 manl~olded as descri~ed above, except they are connected to constant volume power oil sy~tem 92 8upply and return lines q3, 94, respectlvely~
Otherwise, the pilot on~orf electro-control valves 110-117 haYe lntrlnslcally sa~e ~orce motors 122 which receive control channel 7 to 14 on/o~ control slgnal~ over cable 87 from v21ve drlver~ tn low volt~ge valve control~
71. l~ese valve drlvers recelve on/off' contr~l signai~ from 20 pendant 25 oYer cable 86 and modi~y each val~e drlver output si&nal wlth offset and dither components as well. In thi~
~ay, all valve driver~ pllot stages and manual overridas are lnterchangable with respective devices to perform both proportional and on/off control function~. Thls is a tremendous a~vanta~e ln re~ard~ to Da~ntaining m~ner 20 remote control f~u~ctions under~round in a ha:~ardou~ environ-ment.

5~3331 operation of pilot stage 104 hydraullc ser~o e~ployed ~n all electro-control val~es 98 to 103 and 110 to 117 present in ~ain and auxiliary valve bank~ 61, ~2 wlll now be descrlbed. Reference will be made to a pilot ~ta~;e 104 having a proportional load conslstln~ of power stage 105 and manual override 1~6 wlth dual--action ~prin~ bia~ to neutral in control channel~ 1 ~o 6 as oppo~ed to simply on/o~f load3 that occur iI~ control cnannel~ 7 to 14. In addltion, refer~nce wlll also be ~ade to FI~. 5 ~raph in whlch curve 186 repre~ents FIG. 4 electro-control valve proportional operatlng characteristlcs les~ e~treme end~ in terms o~ power ~tage 105 ~alve outflow through cyllnder 1 and 2 port~ 175, 196 Y3. power ~pool po~ition, including power ~pool o~et or pretravel resultlng in power ~tage 105 dead band.
- Cur~e 186 ln FIG. 5 also lllustrates power sta~e 10~ outflow v~. rorce mo~or 122 volta~e and po}ar~ty app}led to coll 123 "B'l termlnal, including o~set and dither s~gnal 187 components incorporated in ~alve dr~er output sl~nals as requtred to oYercome o~rset or ~retravel, ~rictional, and contamination characteristlc3 of the load ln pllot stage 104. As ~hown ln FIG. 5 inset, dlther ~l~nal 187 component has a constant amplltude square wave present at all times, eYen when the proportlonal control signal summed therewith i~ ~ero.
Pllot oll enterlng supply port 126 contlnuously ~low~ through ~ilter 128, supply ps~sageway 129, the fir~t and second leak~ge pathways described abo~e, lnto pilot plston draln ch~mber 161 and out of return port 127. ~hen ~ 3 ~

there 15 no electrical ~ignal applied to ~orce motor 122, pllot spool 149 1~ in both a neutral and null posltLon and center land 152 i~ aligned with the center or supply port 147 on ~echanlcal feedback sleeve 131. E~ual low-level pres~ures develop in the ~irst and second control pathways descrlbed above becau~e equal amounts o~ supply oil bleed o~ through the fir~t and second leakage pathways. As a result~ equal low-level pre~sures act on pull and push piston heads 135, 137 o~ pilot pl~ton 1~4 ~o maintain a central or Or~ positlon. Feedbac~ sleeve 131 i9 biased by spring 133 ~o that cone end 132 main~ain~ a null po~l~ion ~n the s~rvo loop at the center o~ pilo~ piston ~eedback cone 135.
~hen ~orce motor 122 recelves a proportlonal B~, W- electrical signal, pilot 3pool 149 move~ upward a di3tance dlrectly proportlonal to the ma~nltude Or the electrlcal ~ignal. The second leakage pathway i9 blocked momentarily and the ~irst leakage pathway i3 increa~ed momentarlly.
~his actlon resul~s ln a pressure dlf~erential ~avorlng the ~irst control p~thway, thereby causing a pressure dl~ferentlal across pllot pist,on pull and push heads 13~, 137 that cau~e pull head 136 to move p~lot piston 134 le~tward and pull on power ~tage ~poo:L 167. Leftward movement Or pilot plston cone 135 cau~e3 ~eedback sleeve 131 to rlse 7 tendLng to reduce the momentary leakage pressure di~ferential in favor Or the rirst conl;rol pathway. Movement o~ pllot piston 134 and reedback slee~e 131 contlnue 510~1y until the pilot stage 104 hydrau:Llc servo stabilizes ~t a null posltion between pilot spool oenter land 152 and ~eedback sleeve supply port 147.

-2~-3~

'.~he null positlon ~s reached off-center or neutral ~hen the rlrst leaka~e opening 158 is 31ightly larger than the second leaka~e openin~ 159 as oppo~e~ to ; havin~ equal openlng3 at the neutral posltlon described 5 ~ abo~e. A dir~erentlal con~rol pre3sure results in ~a~or of the firat control pat~way wlth su~'ficiency to provlde pilot p~ston 134 wlth enou~h pulling rorce by head 136 to overcome the centerlng e~ort o~ double-actin~ ~pring mechanism 1~5 in manual overr~de 106. Pllot pis~on 134 1~ mainta~ned static at the null po~ition by the dif~erential control pressure favorlng pull plston head 136 as long as the same magnitude of electrical ~lgnal i~ applied to force motor 122. In addltion, power ~ta&e spool 167 maintains the leftward posltion established by pllot ~iston 134, thereby causing an outflow through cylinder 1 port 175, and a back ~low throu~h cylinder 2 port 176, proportional to the magnitude of the B~, W- electrical sl~nal applied to force ~otor 122.
When force motor 122 recel~es a proportional B-, 2Q W+ electrical slgnal ~ro~ a valve driver~ pllot stage 104 hydraulic servo loop operates ~u~t the opposite of that descrlbed a~ove for B+, W- electric~l sl~nal. That i~g pilot spool 149 moves downward a dlstance proportional to the magnitude of' the electrical al~nal. ~he first lea~age pathway is block:ed momentarlly and the second leaka~e pathway is increased momentarlly. ~his action reaults ln a pressure di~feren~lal fa~oring the second control pat~way, thereby causln~ a pressL~e dirferential across pilot piston push and pull heads 136, 137 that cau~es push head 137 to move pilot piston 134 rl~htward and push on power 3tage spool 167.
Rlghtward ~o~e~ent o~ p~lot pl~ton cone 13~, together with bis~in~ ~prln~ 1333 cau~e ~eedback sleeve 131 to lower, tendin~ to reduce the momentary leakage ~res~ure differentlal 5 in ~a~or of the ~econd control pathway, Mo~ement of pilot pigton 134 and reedbac~ sleeve 131 con~lnue un~il the pilo~
~ta~e 104 hyd-aullc ~erYo ~tabilizes at ~ null position the opposite a3 described above.
~hen reachlng the downward null po5ition, a di~fer-10 ential pressure favorin~; the second control pa~hway issu~flcient to pro~lde pllot pi~ton 134 with enou~h pushing power rightward to overcome the centerin~ erfort o~ double-actin~ spring bla~in~ me¢hanism 185. Pllot plston 134 i3 msintained ~tatlc at the null position untll the magnitude o~ electrlcal si~nal is changed at ~orce motor 122. In additlon~ power sta~e spool 167 malntalns the rl~htward position established by pilo~ piston 134, thereby causin~ an outrlQw through cylinder 2 port 176, and ~ backflow through cylinder 1 port 175, proportlonal to the magnitude Or the B-~ W+ electrical ~ignal Qpplied to ~orce motor 122.
Thu~, lt ha~ been shown how pilot ~ta~e 104 hydraul~c servo perform~ a di~ferentlal proportional control ~unction at power stage 104 ~alvin~ when a dlr~erential electrlcal signa.l B~, W- or 3-, 1~ i3 applied to force motor 122.
One aclditlonal characteristlc Or the electro-control ~alves used ln the pre~ent in~ention will now be described. During normal operatlon~ a d~ther si~nal 137 _~

~ 3~

co~ponent o~ the valve driver OUtpllt 1s applied to each ~orce motor 122. The purpose o~ the dlther ~l~nal i3 to ~lnimize frlctional characteristlc~3 o~ each valve'~ moving ~ part~ and to minimize, or elimlnate ~ possible, the e~fects of oil contaminants on valve movin~ part~0 In most ln~tances the dlther 3ignal per~ormance 13 very good. Howe~er, i~ oil contamination ~hould occur that would completely block one o~ the leaka~e openln~s 1589 1593 the pilot pi~ton 134 will retur~ to center neutral po~ition. Thl~ i3 because the leakage flow in the remainlng leakage pathway at an off-neutral null poslt~on i3 not large enouæh to produce a control pressure in the remaining control pathway hl~h enough ~o overcome the force exerted by the centerin~ ef~ort o~ dual-ac~in~ bla~ing 3prlng mechanl3m 185.

MINER ELECTRICAL SYSTEM

The mLner electrical 3y~tem 22 ~hoNn dia~rammat~-cal}y in FI~. 3 ~ill now be ds~cribed by re~errin~ to FIGS.
6-11. As noted above, the remote control system o~ this ln~ention i~ made lntrinslcally safe by tran~orm~n~ 460 VAC hlgh voltage ~o a lower volta~e ln an exploslon-proo~
hou~in~. One e~ample o~ thls i3 low volta~e power source 68 shown ln FIG. ~ block dlagram. ~ere step-do~n tran3former 188 recelves 460 VAC from hi~h voltage source 66 over cable 67 and reduces lt to a lower volta~e of 3~y 115 VAC output at leads la9, 190. The 115 VAC on lead~ 189, 190 ls ~ed to the input~ o~ +7~DC and -7VDC conventlonal solld-state power ~upplies 1.91, 192, each havlng as~ earth grounàed input lead and a~ coD~on grounded output lead. The other ~L~3r`~5;~33~

output lead~ 193, 194 o~ +7VDC and -7V~C power supplies l91, 192 are fed to respecti~e intrln~31cally sare barrler~
1~5, 196.
Esch barrier 195 9 196 ln low voltage power source 5 ~ 58 consi~ts o~ rugged selectable ~eries-parallel connected voltage dropplng resistor3 which llmit low Yolta~e output to all electronic load~3 to a 3a~e +6Y, -6~ and a common connection, respectively. The ~6~ V and common lead3 form cable 69 wh~ch provide3 lntrlnslcally safe low volta~e power requirements to miner remote control pendant 259 interrace controls 70 and low voltage controls ror elec~ro-valves 71 as ~3hown in ~IGS. S to ll and de~crlbed ~elow.
As shown in FIG. 7~, the +6V and ~6V conductors are switched on and of~ ln miner remote control pendant 25 ~y power-on s~ltch 197. Thl~3 swltch controls low ~o}ta~e power fed to all control devices in pendant 25 and con~e-quently acts as a master swi~ch ~or all remote control functlons on min~r 20. On the load side o~ power-on switch 197 ln FIG. 7A, as well as devices ln FIGS. 8A, 8B, 9A to 9D and lO, the low voltage conductors to control devices and Yal~e clri~ers and the iike are identi~led as ~6'V and -6'Y to distingulsh them ~rom the unswltched +6V and -6V
conductor~ a~eacl of power-on switch 197.
Miner remote control pendant 25 lnclude~ two momentary D~P~DoT~ control swttche~3 19~, 199 labeled pUmpB
and cutter head~3, respectively. ~hen remote/manual swttch 66 is select2d ~or remote mode of mlner 20 operatlon, control switchel3 198, l99 provide separate remote on and 3~

~ r control slgnals to solid-~tate relays ~n interface control~ 70- The~e on and off control si~nals cau~e solid-state relay contact~ in inter~ace controls 70 to parallel I local manual start and stop control actlon in hl~h voltage 5 1l pump and drlve motor controllers 64. As wlll be de~crlbed .I below, thls circult arran~ement provides an operator wlth mean~ on pendant 25 ~or remotely controlling both the operation of pump motor3 57, 59 from ~witch 198 and cutter ll~ head drive motors 35, 36 from swltch 199.
10~1 The ~olid state relays and other deYices in inter-! race control~ 70~ as well as motor s~arter~ and other devlce~
~¦ in hlgh voltage pump and drlve motor controller 64, arehoused in an explos~on-proo~ enclosure on miner 20 to comply Il wlth mine sa~ety requirements.
15 ~ During a momentary on closure of pump ~wltch 198, ~ one pole feeds a momentary ~6'~ sl~nal over lead 200 to I the inpu~s o~ solld-s~ate start relays K4, X5. Relays ~4, ~5 momentarily close their normally open contac~s in the 1~ con~tant volume pump motor 57 (CVP-M57) control circult 20 1l descrlbed below. The momentary +6'V signal on lead 200 , is also fed to the lnputs of electronic circuits consistlng I o~ ad~ustable time delay on energize 201, ad~ustable time delay on deenergize 202 and latch circult 203. After a predetermlned time delay, tlme delay circult 201 ~eed~ the 25 ~ momentary +6'Y ~lgnal over lead 204 to the lnput of solld-~tate start relay RK2. Relay K2 momentarily close3 lts normally open contact ln the ~arlable volume pump ~otor 59 ( W p-M5g) control c~rcuit also descrlbed below.
~ I
,~, ;' ' .

Further, the momentary ~6'V sl~nal on lead 200 cause~ tlme delay on ueenergl~e 2Cl2 to l~medlately feed a dif~erential dump control slgnal i~olated rrom ground 1ll over leads 205, 206 to the input Or a valve driver ln control 5 channel 7 shown ln FIG. 8B. The ctump control si~nal i~ ;
i m-~ln~ained at the output Or devlce 202 ~or a predetermined dela-y a~ter deener~i~lng its input. As wlll be explalned below, the d~mp control slgnal on lea~s 205, 20~ acts to Il momentarlly relleve hydraulic pre~ssure on the var~able 10! volume pump ( W P) 60 so that relay ~2 may permlt starting o~
pump motor 59 with ~ minlmum of load durlng the deenergi~.lng delay pertod.
. In addltlon, the momentary +6'V signal on lead ~ 200 cause~s a capac~lor within latch clrcult 203 to charge 15 ll and inhlbit both s~op circuits of conestant and varlable volume pumps.
When a momentary off closure of pump switch 198 occur8, both pole are grounded ancl the latch circult 203 I input l~s ~rounded by way of lead 207, Thi~ enables latch 20j! circuit 203 which ~eeds a momentary ~6'V ~i~nal over lea~
208 to the input~ Or ~solld state stop relays K3, Kl. Relay~
K3, Kl momentarily open their normally closed contact~ in ¦ the constant vo}.ume pump motor 57 (CVP-M57) and variable I volume pump motor 59 ~ W P-M5~) control clrcuits descrlbed 25~ below.
Further, the momentary groundln~ Or pump switch 198 durlng a moment~Lry o~P closure oP both pole~s also re~ets time delay devlc:es 201, 202 so they may be ready ~or circuit operatlon a~s de~scrlbed above.

~1 ..

3~

Durin~ a m~ment~ry on closure o~ cutter head Il switch 1~9, one pole fee~ a momentary +6'V slgnal on lead ,~ 20~ to the lnput~ of solid-state start relays ~7, K~ and lll latch circult 210. Relays ~7, XS momentarily close their 5 li normally open contacts in control circuit~ descrlbed below ll ln connectlon with left and right cutter head motors 35, 36 i¦ (C~LT-~35 and CERT-~136) respectiYely. The momentary +6'~
Il on lead 209 causes a capacitor ln latch clrcui~ 210 to char~e ¦ and inhibit the stop clrcult for both cutter heads.
lO~j When a momentary Ofr clo3ure of cutter head switch 199 occurs, both pole~ are grounded and the latch circuit ~¦ 210 input 1~ grounded throu~h lead 211. Thi~ enable~ latch ¦ clrcuit 210 whlch reeds a momentary +6'~ si~nal over lead Il 212 to solid-state stop relay X6. Relay K6 momentarily 15 ll opens its normally clo3ed contact in the cutter head drlve motor control circults 35, 36 described below tC~LT-M35 and C~RT-M36).
Further, durlng the momentary of~ closure of cutter ll head swltch 199, the momentary +6~V 31~nal on cutter head 2Q¦ stop circuit lead 212 i~ ~ed to the lnput of 2 tram halr-speed circuit descrlbed below wltn reference to FIG. 8A. Th~
5~ gnal cause3 tram forw~rd speed to be au~omatlcally reduced to half-3peed when cutter head driYe motors 35, 35 are not l, stopped, and to return to tram full ~peed when cutter heads 25~ are not being drlven.
¦ In adclition, a momentary D.P.S.T. mu~hroom-head ¦ pu~hbutton switch 213 l~beled emer~ency stop ceases operation Or all pump and outter head drlve r.otors 57, 59, 35, 36, -32- !

S~3~

simultaneously. Both pole~ o~ switch 213 are ~rounded on one side of the swltch and the othler slde o~ each pole i3 wired to leads 207, 211 connected to the inputs o~ latch Il circuits 203, 210. When emer~ency stop swltch 213 1~ closed 5 ¦ momentarily, a momen~ary +6tV 31gni~1 energlzes solid-state 1 3top relays Xl, ~3, K6 a~ de~cribed abo~e. Relays Kl, K3, ~6 all momentarlly open their normally closed contacts and simultaneously deener~ize the control circuit ~or all pump l and cutter head drive motors as described below.
10¦ Stlll rererring to FIGS. 7~ and 7B, a description l will now be ma~e o~ all motor starter and control circults I ln hlgh Yoltage pump and drlve motor controller3 64, and the in~eractlon therewlth of test swltches 82~ remote/manual Il switch 66, and a bank of local manually operated pushbutton 15l~ swltches 214. Test s~itches 82-1 ~o 82-6 are momentary contact start and 3top pushbuttons noused in a separate enclosure.
Independently of remote~manual swltch 66 operating ll mode, test swltches 82-1 to 82-6 permit activatlon of the 20j control clrcults ~or pump and cutter head drl~e motors 57, 59, 35, 3S a~ a mean~ ~or determlning whether solid state start and stop relay~ Kl to K8 are functionin~ properly under remote control ~rom miner pendant 25.
Local manually operated switches 214-1 to 214-6 ~5 are momentary contact start and stop pushbutton~ h~used ln ~eparate enclosure~ from test ~wltche~ 82. When under manual operating mode O.r remote/manual swltch 66, manual pu3hbutton swltch~ 214-1 to 214-6 are arran~ed ~or local start and :

, . ~

~top operations in the control clrcuits of all pump and cut~er head drlve motors ~7, ~9, 35, 36. In o~her words, manual pushbutton qwltches 214-1 to 214-6 provide local ~ control in place of remote pump, cutter headg and emergency 5~, stop swltches 198, 199~ 213 on miner pendant 25. These ~wltches, a~ well as all others on mlner pendant 25, are ! deactivated when remotefmanual swltch 66 lq placed ln the Il manual mode o~ operation.
il Control c~rcuit po~er for controller 64 is derived 101 from step-down tran~former 215. Trans~ormer 215 receive~
¦ 460 ~AC o~er cable 63 from high volta~e source 55 and reduces I lt to, for example, a 230 VAC output. Thl output 19 fed to ¦1 output leads Ll and L2 and through sa~ety s~itch 216 to all l! pump and cutter head motor control clrcult~. 460 VAC is also fed over cable 65 from high voltage source 55 through normally closed contact~ 66-1, 66-2 and over cable 67 to low ~oltage power source 67 described above ln FIG. 6. Thus, when r,emote~manual switch 66 is chan~ed from remote to manual mode, contacts 66~ 6-2 opsn and deenerglzes not only low ~oltage 20 ¦ power supply 68 but the mlner pendant 25 and all other lntrlnsically 3afe loads connected thereto.
l The remote control mode ~or switch 66 shown in I FIGS. 7A and 7B ~ lrst be described followed b~J the ~ manual control mode. Regardles3 of whlch operating mode i9 selected there i,5 a predeterm$ned motor starting sequence which must be ~ollowed ln order to minimlze hlgh ~oltage luctuations ~rom high ~olta~e source 55 whlch would result ~rom large chang~e~ in connected loadO First, the constant Il 1 33~

volume pump motor 57 i3 ~tarted, second the Yariable ~olume pump motor 5~ ls ~tarted, third the le~t cutter head drlve ~otor 35 ls started, and ~ourth the rl~ht cutter head drl~e Il ~otor i3 started.
5,, Constant volume pump motor 57 start~ after pump swltch 198 1~ turned on momen~arlly and current rlowY
~rom Ll through manual stop pu~hbutton 214-1, lead 217, test 3top pushbutton 82-1~ lead 218, X3 relay normally I closed contact, lead 219~ normally closed switch fi6-4, lead lOi~ 220, and X4, K5 relay contacts momentarily closed by pump ¦ swltch 198. The 3tart current path contlnues through lead~
221, 222, to motor starting coll M57 and time delay relay ¦ coil T57, through lead 223 and motor overload relay contacts ¦ OL-~57 to L2.
15 I As soon as starter coil M57 become~ ener~ized, normally open sealing contact ~57 close3 permanently ~o l maintain a sesllng current path dlrectly from lead 219 to ! coils M57 and T57, thereby starting con~tant volume pu~p l motor 57. The constant volume pump motor 57 and colls M57 20,~ and T57 remain energl~ed even thou~h normally open relay l~ contact3 X4, X5 experlenced only a momentary closure. Time ¦ delay relay contacts T57 close after a predetermined time delay and are u~ed in the sequential ~tartlng Or ~ariable I volume pump moto:r 59 descrlbed below.
25 ll An alternate start current path for constant volume pump 57 is established when test start switch 82-2 9 clo~ed momentarily and current flow~ directly to colls M57, T57J through OL-M57 relay contacts and then to L2.

,, , Sealing contact ~57 clo3e~ permanently.when test start switch 82-2 is released, thereby maintainlng pump motor 57 operatlon.
Constant volume pump motor 57 ls ~topped when 5l pump switch 198 is turned of~ momentarily, thereby momen~arlly opening relay contact X3 and breaking the sealing current path through leads 219, 222 and 3eallng contact~ M57 and Il deener~l~ln~ botn coil~ M57 a~d T57. Alternatively, a il momentary opening o~ either te3t ~top switch a2-1 or motor lOIl oYerload relay contacts OL-M5T also break3 the ~ealing current 1 pathway to coil~ M57 an~ T57, thereby deener~izlng constant I volume pump motor 57.
Yariable volu~Le pump motor 59 ~tart~ after constant volume pump motor 57 i~ runnin~ and a~ter a time delay pre-determined by deYlce 203 when pump s~ltch 198 i3 turned on momentarily and current ~lows fro~ Ll throu~h manual stop pushbutton 214-3, lead 224, test Btop pu~hbutton 82-3, lead ¦ 225, normally closed relay Xl contact, lead 226, normally Il closed s~itch 66-6, lead 227 and X2 relay contact closed 20 1l momentarlly by pU~Lp switch 198. The start current path continues through leads 228, 2~9, T57 time delay sequence ..
interlock contacts whlch close after pump motor ~7 starts, to motor starter coil ~59, through lead 230 and motor over-l load relay contacts OL-M5g to L2.
25l As soc,n as starter coil M57 becomes energlzed~
, normally open se!alln~ contacts M59A and M59B close permanently to maintain a current path dlrectly ~rom lead 226 through lnterloc~ contact T57 to ~tarter coil M5~, thereby starting ~5~3~

variable ~olume pump motor 59. The ~ariable volume pump otor 59 and starter coil M59 remain energlzed through sealing contacts ~59A even though normally open relay con-~ tacts K2 experiencè only a momentary clo~ure, and as long 5,~ a3 con~tant volume pump motor 57 is energized and contactsT57 rema~n closed. Sealing contacts M59B open and clo3e wlth contacts M59A and are used in the sequential Rtarting of left and rlght cutter head dri~e motor3 35, 36 described below.
o l! An alternate start current path ~or ~arlable ~olume pump motor 59 1~ eitablished when test start swltch 82-4 is closed momentarily and current ~lows directly ~hrough contacts T57 to ~tarter coil ~59, o~erload relay contacts . OL-M59 and to L2. Sealin~ contacts M59A close permanently 5 ll ~han test ~tart switch 82-4 1~ released, thereby maintainlng pump motor 59 operat~on.
ll ~ariable volume pump motor 57 i~ ~topped when I pump ~witch 19~ i~ turned o~f mementarily, thereby momentarily Il opening stop relay contact Kl and breakin~ the seallng current 20 1l path through contact M59 and deenerglzln~ 3tarter coil M59.
Alternatively, a momentary opening o~ either test ~top s~itch 82-3 or motor overload relay contact~ OL-M59 also l break~ the seali.ng current pathway to Rtarter coll M59.
I Left and rlght cutter head drive motors 35, 36 start 25 1l sequentially art;er constant and ~arlable pump motors 57, 59 ¦1 are runnlng and after cutter head switch 199 i~ turned on momentarlly and current flows from Ll, through manual stop pushbutton 214-';, lead 231~ te~t stop pushbutton 82-5, lead .
, .

3 ~

232, normally closed ~6 relay contact, lead 233, normally closed swltch 6G-8, lead 234 and K7, X8 relay contact~
momentarlly clo~ed by cutter head switch 199. A single ~tart current pathway through leads 235, 236 branche~ lnto three parallel pathway3.
I A ~irst branch current ~athway extends to lert cutter hea~ dri~e motor 3S starter coil M35, ~hrough lead 237, left motor 35 o~erload relay contacts OL-M35, lead 23 ,, and var~able ~olume pump motor 59 sealing lnterlock contact 10l1 M59B to L2. A ~econd branch current pathway extend~ to time jl delay relay coil T35, through lead 239, motor 36 overload I relay con~acts OL-M36, lead 238 and interlock contact M59B
!i to L2. A thlrd branch current p~thway extends to rtght Il cutter head dri~e motor 36 starter coll M36 3 through lead 15 ll 240, right motor 36 overload relay contact~ OL-M36, lead 238 and interlock con~act M5~B to L2. ¦
I Le~t starter coil M35 beco~es energl2ed ~irst ¦ and, after a short time delay deter~ined by contact T35 ,I closure tlme~ rlght starter coll M36 then becomes energized.
20 ~ ~en starter coil~ M35, M36 become ener~ized 3 normally open ¦ ~eallng contacts M35, M36 close permanently to malnta~n a seallng current pathway dlrectly ~rom lead 233 throu~h sealing contacts M35, M36, lead 241 and lead 236 to coils ~ ~35, M36 and T35, thereby startlng le~t and right cutter 25 1I head motor~ 35, 36 sequentlally under control o~ varlable il ~olume pump lnterlock contact M59B. The le~t and right cutter head drlve motors 35, 36 and coils I~35 3 M36~ T35 l remaln ener~lzed even though normally open relay contacts I K7, K8 experlence only a momentary closure.

;

An al~ernate start current path ~or le~t and ri~ht cutter head drlve motor~ 35, 36 i~ establlshed when t~t start ~wltch 82-6 la closed momentarily and current flows il dlrectly through lead 236 to coils ~135, M36, T35 and other 5' oYerload~ time delay and lnterlock contacts in the three j branch current pathways as descrlbed abo~e. Sealing contacts Il M35, .~36 close permanently when te~t start ~witch 82-6 13 released, thereby ~aintainln~ left and right cutter head Il drive motors 35, 36 ln oper~tion.
lO, Le~t and rlght cutter head drive motor~ 35, 36 are stopped when cutter head switch l99 i8 turned of~ momentarlly, thereby momentarlly openln~ stop relay contact X6 and breaking the seallng current pathway throu~h contacts M35, M36 and ! deenerglzin~ ~tarter coils M35 J M36. Alternatively, a 15 momentary openlng of te~t stop 3witch ~2-~ or motor oYer- j i load rel~y contacts OL-M35 or OL-M36, or varlable Yolume pump 59 interlock contact M5gB also breaks the sealing current pathway to starter colls M35, M36.
~ The manual control mode for ~witch 66 shown ln 20l FIGS. 7A and 7B will now be dPscribed. Flrst, normall~

i closed swltche3 66-l, 66-2 are opened and deener~l~e the low ¦ vol~a~e power supply 68 and all intrin3ically sa~e remote controls. Second, the normally clo~ed ~wltches ~6-4, 66-6, 66-8 in the pump and drlve ~otor control circults are opene~
251 and the normally open ~witthes 66-3, 66-5, 66-7 therein are closed. This switching arrangement ~ypasse~ the solid-state relay contact ~l to ~ action as descrlbed aboYe. All motors are started in the same sequence a~ de~crlbed above.

.~ I

-3g-, 3~
, . .
I ~he constant volume pu~p motor 57 is ~tarted by a momentary closure o~ manual ~tart pushbutton 214-~ whlch energizes starter coll M57 and tlme delay coil T57 as described above. A sealing current pathway i~ maintained 5 l by sealln~ contacts M57 which bypass pushbut~on 214-2. Pump j motor 57 ls ~topped by a ~omentary openin~ of manual stop pushbutton 214 1, or any of the o~h~r method3 ~escribed above, thereby breaklng the sealin~ current pathwsy throu~h 1 sealing contacts M57 and deenerglzing starter coil ~157 and 10 I time delay eoll T57.

il The varlable volume pump motor 5S i9 3tarted ln equence after a time delay by a momentary clo~ure o~ manual ~tart pushbutton 214-4 which energlzes starter coil ~59 also Il as descrlbed above. A seallng current pathway is maintained 15 1l by sealln~ contact M59 which bypas~es pushbutton 214-4.
Pump motor 59 ia 3topped by a momentary openlng o~ manual ¦
top pu~hbutton 214-3, or any of the other methods descrlbed above, thereby breakin& the ~ealin~ current pathway throu~h 1~ sealin~ contact~ M59 and deenergi~ing ~ta~ter coll M59.
20l~ The le~t and ri~ht cutter head drlve motor~ 35, 36 ,l are started in aequence wlth the varlable volume pump 59 and I¦ each other by a momentary closure o~ manual start pushbutton 214-6 whlch energi~es starter coll~ M35, M36, and time delay I¦ coll ~3~ also as descrlbed above. A ~ealing current pathway 25~ main~ained by sealln~ contact~ ~3~9 M36 which bypass pu~hbutton 214-lS. Cutter head motor~ 35, 36 are s~opped by a momentary openlng o~ manual stop pu~hbutton 214-5, or by any other metllod de~cribed above, thereby breaking the sealin~ current pathway through sealing contacts M35, M36 and deener~izing starter coils M35, M~6 and tlme delay coil 1, Re~erence will now be made to FIGS. 8A, 8B block 5 1l dlagrams of the intrinsically ~afe mlner remote control 1 channels 1 to 14 whose runctions ~re listed ln TABLE 1.
Each control channel operates at not more than ~6VDC and Il will be descrlbed below. In addition to ha~lng the fore- I
il going pump and cutter head on/off ~witches 198, l99, miner lO ~ remote control pendant 25 al~o includes ~ix ~IG. 9A-9~ ¦
I dif~erenttal proportlonal control devlces 242 to 247 with spring centered rotary levers, some of which incorporate a deadman swltch, controlling channel~ 1 to 6. In additlon, pendant 25 ha~ 3e~en FIG. 9D dl~rerent~al step type control devices 24~ to 255 ~ith sprlng centered toggles controllin~
I channels 8 to 14. Chann~l 7 i~ controlled by monitoring pump operation and is not pro~lded wlth a control deYlce on pendant 25.
l The ~ntrinsically sa~e remote control ~y3tem permit~ the mlner remote control pendant 25 to be h~nd-held.
It ls pre~erred to make an intrlnslcally sa~e pendant 25 out of llght-weight high-lmpact moisture-reslstant plastlc rather than metal. Plastic elimlnates a multlple groundin~
path from the electronlc 3ystem used hereln, thereby mlniml~ing elect:ronic design and maintenance problems with the entlre remote control ~ytem.
Thlrteen dl~erentlal proportlonal and step type control 31 ~nals from miner pendant 25, together wlth one di~erential ste]p type control signal from pump-monitor time !l I

delay device 202 in FIG. 7A, are fed a~ ~ourteen individual lnputs to correspondlng differentlal valve driver~ 256 to 269 operative ln control channels 1 to 14 a~ part of low I voltage controls 71. ~ach dirferential valve drlver 256 to 5l, 269 1~ clrcuited as ~hown in FIG. 10 so that it can be used jl lnterchan~ably with any electronic ~orce motor 122 actuatin~
on a FIG. 4 electro-control ~alve, whether or not it~ use ls ln a proportional val~e bank 61 or in on/o~f valYe bank 62.
Il Valve drlYer interchangability contribute~ to the univer~allty 10 1 o~ the remote control ~ystem.
Each dlf~erentlal valve drlver 256 to 269 is capabl~ of produclng a di~erentlal output volta~e havlng of~Ret and dlther components as ~hown in FIG. 5. The output !l ~oltage varies proportlonal to a llnear input current from pendant ?~ which represent~ the mlner hydraulic ~unction to be controlled, regardlesR o~ whether the input current 1~ a proportlonal or ~tep type current.
I Low voltage controls 71 also lnclude dither o~clllator 270 which generates a conventional dirferential 20l ~quare wave output si~nal on lead 187. ~he dlther output 1gnal ls pread~uated to a ~ixed amplltude and ~requency.
Dlther frequency i~ between ~0 and 60 hz. and represent3 the be~t ~requency range ror m~nlmlzin~ ~rictional and con-tamlnation effects o~ the electro-control valve 3hown in 25 ~ FIG. 4. The dlther output 3i~nal on lead 187 is connected to an input summlng ~unctlon of every valve driver 256 to ¦ 26~. Here the d~ther ~i~nal becomea a component, along with an of~et component, Or what ls com~ined with the remote , f3~ 33~

control current to ~orm a total lnput current for each control channel 1 to 14. A typica~. dlther sl~nal 187 co~ponent is shown in FIG. 5 in~et and is alway~ present la I valve dri~er output signal regardl~ss of whether the remote 5 1¦ control current 18 zero, max~mum, or a proport~onal value therebetween.
A tram halr-~peed circuit 271 shown in FIG. 11 1B
also included in low voltage controls 71. The tram hal~-ll speed circuit 271 monltor~ cutter head operation by way of the ~i~nal on lead 212. This signal is fed from latchclrcuit 210 output in the cutter head motor 35, 36 ~top c~rcult shown in FIG. 7A. Rlght ~nd left trams 29, 28 are normally permitted to be drive hydraulically up to ~ull , for~ard and reverse speeds by the remote control currents o~
15 ~ proportional remo~e control devices 245~ 246 belng red to two inputs o~ tram ha}r-speed cirruit 271~ However, when cutter head motors 35, 36 become operational, tram half-peed circult 271 automatically reduces tram forward speed ~l only by one-half the value of up to a ~ull ~etting of remote 20 1l¦ control device ~45, 246. Output from tram half-speed ¦ circult 271 i~ ~ed to the inputs of valve drivers 259, 260 ¦ in the right and left tram remote control cha~mel~ 4 and 5.
All of the val~e drl~er~ 256 to 26g, the dither ¦ 03cillator 270 and the tram hal~-speed circult 271 comprlsin~
10W Yoltage circults 71 are lntrinsically safe clrcuits fabricated preferably on plug-in clrcult boards and housed in a nonexplosion-proof enclosure not shown. Thl~ construc-tlon ~eature ~acllltates malntenance o~ the mlner remote .

i control 3y~tem both above ground and below ground ln a 1ll hazardous enYiro~ment.
f,l Sl~ outputs from dlfrerentlal valve drlver~ 256 to Il 261 in propor~ional control channe3.s 1 to 6 are fed to 5 ll corre3pondin~ force motors 272 to 277 ln the main bank of proportlonal electro-control valves 61. Elght outputR from . differentlal valYe drlver~ 262 to 26g are fe~ to corre3ponding force motors 278 to 285 ln the auxillary bank of pilot l! on~off electro-control valYe~ 62. Each ~orce mo~or 272 to 10 ¦ ~85 ls the 3ame as force motor 122 shown schematically in FI&. 4 and provides an electro-valve pull and push con~rol force characterized in FIG. 5 when energized by the dlr~erential output ~rom any valve driver noted above. Operation of ! control channels 1 to 14 whereln ~orce motor 272 to 28 ~unct~n wlll be de~cribed below.
In FIGS. 9A to 9D there 1~ shown four ~chematic ¦ dlagrams o~ thirteen remote control devices 242 to 247 and 249 to 255 ~hown in FIGS. 8A, 8B that are lncorporated ln miner remote control pendant 25. FI~. 9A lllustr2te 20 1 dif~erential proportional remote control device~ 242, 247 used in control channel~ 1, 6 ~or up-down control action.
~ach of the~e control devices consi~t of selfcenterln~, lever action, dual potentiometer~ 286A, 286B connected ln . parallel across t.he +6'~, -6'V source. Pot2ntlometers 286A~ I
25 ll 286B are connecteld ~or slider counter-rotatlon so that an output slgnal on leads 287, 288 will vary differentlal~y proportlonal to ~llder posltlon and hydraulic functlon to be controlled on mlner 20.

. . ~

;
When the sliders are centered there i~ ~ero output acro~s leads 287~ 288. I~en the slider~ are dlrected to the ll up positlon, the signal on lead 287 13 ne~atlve (-) and on il lead 288 is posltlve (+), both ~ary~n~ proportlonal to !i !
5 ii slider positions ~rom center. When the sl~ders are dlrected ¦ to the down posltlon, the opposite polarity of the same magnltude 3ignal is produced on leads 287, 238. That 1~, the si~nal on lead 287 be~omes positive and that on lead 1 288 becomes negatlve proportional to ~lider positions from 10 1 center. The diP~erentlally ~arying proportional output I sl&nals on leads 287, 288 ln remote con~rol devices 242, 247 are connected to the input~ of correspondlng val~e drivers 256, 261.
l FIG. 9B illu~trates differentlal proportional 15 ~ remote control devlces 243,244 used in control channels 2, 3 ~or up-down or le~t-right control actlon3 re~pectiYely.
Each of these control devlces includes a press-type D.P.D.T.
deadm~n switch 2$9 having a normally open pair o~ contact~
¦ connected to the -6'Y, +6'V source and a normally clo3ed 20 1I pair o~ contact3 connected ~o ground. Also included in each o~ these control devlce3 is a ~elf-centering, lever-action, l dual potentiometer 290A, 290B connected in parallel across I the co~mon poles of dead~an switch 289 by way of lead~ 290, ~ 291. Potentiometers 290A, 290B are connected for slider 25 ~ counter-rotation so that an output ~i~nal on leads 293, ~94 will vary dlrfer~entially proportlonal to slider posltlon and ydraullo ~unct1Dn to be controlled.

-~5-,, .

3f~

Il When deaoman switch 289 is released or otherwlse not pre~sed, the output on lead3 293, 294 ~ grounded regard-1 lesQ o~ slider positlon. '.ihen deac~an switch 289 i~ pressed Il and maintained that way and both s;Liders are centered, there 5 ~ zero output on leads 293, 294. h~en the sllders ar~
I directed to the up, or le~t, po~itlon, the signal on lead 293 is positive (+) and on lead 294 ls ne~atiYe (-) ~ both varylng proportional to slider posltions ~rom center- When ~I the sllder3 are dlrected to the down, or ri~ht, po~ition, a 10 ~ signal o~ the opposlte polarlty and same msgnitude is produced on leads 292, 294. That is, the si~nal on lead 293 l become~ negatlve and that on lead 294 becomes pos~tl~e I proportional to their sllder positions from center. The ~ di~ferentially varyln~ proportlonal output 31gnals on leads 15 l¦ 293, 294 ln remote control deYices 243, 244 are connected to ~i the inputs o~ corresponding valve drivers 257, 258.
l FIG. 9C illu~trates dl~erentlal proportlonal i remote control devlces 245, 246 beln~ ~sed cooperatively ln I control channel~ 4, 5 ~or reverse-~orward control actlon, 20 ~ respectl~ely. ~ach of these control deYices includes pres~-type D.P.D~T. deadman switch 295 havin~ a normally open palr of contact~ connected to ~6'V, -6'V source and a normally closed palr of contact3 connected throu~h respectlve resi~tors 296, 297 to ~round. Also lncluded ln each of these control dewlces ls a self-centerlng, lever-action, dual potentiometer 298A, 2983 connected ln parallel acros~
, the common poles of deadman switch 295 ~y way of leads 299, ll _~6-335~

,, 300. Potentiometers 2g~A~ 29~B are connected for slider ! counter-rotatlon 90 that ~n output ~lgnal on lead~ 301, 302 wlll vary differentially proportlonal to ~llder po~ition and Il hydraulic functlon to be controlled.
5 ¦I When deadman switch 295 i9 relea~ed or otherwlse not pressed, the output on leads 301, 302 1~ ~rounded I through re~31stors 296, 297 regardle~s of slider posltion.
When deadman swltch 289 i~ pre~ed and maintalned that way ~ and both sliders are centered, ~here i~ ~ero output on leads 10 ¦ 301, 302. '~hen the sllders are directed to their reverse posl~ion, the sl~nal on lead 301 ls ne$ativs (-) and on I lead 302 is po31tive (~), both varyln~ propor~lonal to ! sllder po~ltlons from center. ~hen the sliders are directed ~ to the ~orward position, a ~ignal of opposite po~arlty and 15 ¦ same magnltude 1~ produced on lead~ 3013 302. That i~, the slgnal on lead 301 becomes positlYe and that on lead 302 become~ negatlve proportional to thelr sllder positlons from center.
ll The difrerentially varyin~ output ~i~nals on leads 20 ~ 301, 302 ln rlght tram remote control device 245 is connected to a rlght tram input o~ tram hal~-speed circuit 271 in FIG.
11. Cooperatln~ wlth remote control device 245 ls device I 246 which ha3 the common poles o~ its deadman ~wltch 295 l connect~d in parallel with devlce 245 by ~ray of leads 2~9, 25 ~ 3 In that way, either deadman swltch 295 may be pres~ed to start mlner tram movement, but both deadman switches mu~t be released to 3t;0p tram movement. ~he dlf~erentially I varyin~ output signals Or left tram remote control devtce I !

l -47-3:~ .

246 occur on separate output leads 303, 304 which are connected j to a le~t tram input o~ tram hal~-speed clrcui~ 271 in FIG.
i 11. Rlght and le~ tram output~ ~rom tram hal~-~peed Il circults 271 are connected to re3pectlve valve dr~vers 259, 5 '1i 260 a~ de~cr~bed below.
FIG. 9D illustrates dif~erentlal 3tep type remote control devlces 249 to 255 being used in control channels 8 ~o 14 for on-of~ up-do~n, or for~Yard-reYerse control actlon.
~I Each of these control deYlce~ consi~ts Or a tog~le type 10 ¦ D.P.D.T. 3witch 305 having a normally open pair of contac~
connected to the +5'V, -6'~ ~our~e and a nor~ally closed l pa~r of contacts connected to the -6 IV9 l6'~ source. Output ! leads 30~, 307 are connected ~o the common poles of tog~le~
~ 3witch 305 and to the ln~ut~ of corre3pondlng Yalve drivers 15 1 263 to 269.
To~le 3witch 305 ~unction~ a~ a polarity reversal swltch. When qwitch 305 13 in ~he O~r, down, or reverse po~lt~on as shown, lead 306 recelves a -6'Y ~lgnal and lead i 307 recelve~ a +6'V si3nal. ~,~en ~witch 305 18 in the on, up, or ~orward posltlon opposlte that shown, lead 306 receive~
a +6'V ~lgnal and lead 307 recelves a -6'V si~nal. Thus, the particular 3tep type hydraulic functlon ~o be controlled by remote control devlce~ 24~ to 255 wlll depend on the polarlty rever~lng po~ition o~ thelr correspondin~ toggle swltche~ 305.
Turning now to FIG. 10, there i3 ~hown a schematic dlagram o~ an intrln~lcally qa~e di~rerentlal ~alve drlver circuit havlng ~lrst and second halYe~ o~ subqtantlally the .
1l ! -48-æame circultry operating at reversed polaritie~. ~IG. 10 typifies each o~ the ~ourteen di~erential ~alve drlvers 256 to 269 that are used for both proportional and step type remotely controlled hydraulic ~uncl.ions on miner 20. In the de~crlptlon o~ a valve driver that follow~, re~erence will be ~ade to only a dl~rerential proportional control ~ignal input of up to +6'Y ~rom a remote control device, uch as de~lce 2423 output on leads 287, 288, as opposed to a step type control 31gnal whlch wlll become ~elf-evldent.
10 ¦ The purpose of such Yalve drlver 256 ~o 269 1~ to recei~e a dl~erentially variable control si~nal and a di~rerentlal dither signal component~ monltor the control si~nal ~nd produ¢e pos~tlve (~) and negati~e ~-) of~et signal components, amplify the combined control, dit~er and offset ~ignals, tAereby to produce a dirrerentlally Yariable val~e driver output ~lgnal having a combined control and of~et characteri3tic as sho~n in FIG. 5. It ls to be noted that the dither ~ignal 187 component shown in FIG. 5 lnset is al~ays o~erlald ln the valYe driver output sibnal to mlnlml ze valve frlctlonal and contamination e~fects, even ~hPn the lnput control ~ignal 19 zero. ~alve drl~er output is fed to B~ W terminals o~ coll 123 ln electro-val~e force motor 122.
~ he maJor components o~ both ~rst and ~econd halves of each d'l~ferentlal val~e driver 256 to 26~ lnclude a pair of contro:l ~lgn~l lnput terminals 30~, 309 which receive a differentially varlable control ~i~nal ~rom remote control devlce 242. A dlther sl~nal lnput termlnal 310 ls ,~ ' 3i~

¦ included to recelve a differentlal dlther signal from dither o~cillator 270 over lead 187. In ,addltlon, 3011d ~tate dlrferentlsl of~set ampll~lers 311~ 312 are lncluded to Il monitor the lnput signal~ snd genera~e the posltl~e ~+) and 5 1¦ negative ~-) o~r~et slgnal compone.nts. ~urther, solid~state dlfferentlal power op~rational ampll~iers 313, 314 ~re 1l! ~ncluded to combine the sontrol, dlther and o~set ~i~nal~, I¦ thereby producing a ~6'V dl~erentially variable valve ¦¦ driver output slgnal at output terminal~ 315, 316.
10 ~ More ~peclfically, in the ~irst half Or valve l driver clrcultry a control sl~nal current from input ~¦ terminal 308 pas~es through monltorlng Junctlon 317, control summing resistor 318, ~ummlng ~unction 319, and to the ' negatiYe (-) lnput o~ power operational amplirier 313.
15 ~ The positlYe (~) input of ampli~ier 313 is ~rounded. The . dlfrerential voltage ou~put Or po~er operational ~mplifler 313 at termlnal 315 is determ4ned by the value of ieedbac~
re~istor 320 and the polarlty Or the control voltage at ~ input term~nal 308. ~hen input terminal 303 1~ +~ output 20 11¦ terminal 315 will be +, and vlce Yer~a. I
0~3et amplifler 311 posi~ive (+) input i~ connected to control si~nal monitor Junctlon 317 by way of resistor 321 ~or the purpose of sen~lng the amplitude and polarity of l the control signal at input terminal 308. Ampli~ier 311 25 ~ negative (-) or re~erence lnput i~ connected between voltage ~ dlvidin~ re313tors 322 and 323~ the latter belng connected I to a +6V referenc:e ~ource.

~, I -5o-5~

" Assu~lng lnput termlnal~ 308~, 309- conditlon ., arises, o~set ampli~ler 311 compare~ only a positlve ~ariable ~ignal at monitorlng Junction 317 wlth the po~itive ' reference signal acro~s resl~tor 322. The dlf~erence 5 I between lnputa i~ ampli~ied by o~et a~plifier 311 and Il output to o~set ~unction 324 a~ a. posltlve of~set voltage ii component. ~he magnltude o~ poæltiYe of~et voltage at or~3et ~unction 324 1~ determined by the value o~ ~eedback 1~ re~istor 325 and the Yol~age dlvlding resis~or 322, these 10 1~ being selected to produce the ~osltlve o~set requlrement for the electro-~alve characterl~ed ln FIG. 5.
Il The off~et voltage component at Junctlon 324 is ~ed through ofrset resi~tor 326 to su~mlng ~unctlon 319 Il where lt is combined with the dlf~erentially variable 15 ¦~ control ~oltage produced by control current ~lowing throu~h ¦ control ~ummi~g resi~tor 318. Thus, the po~itlve o~set voltage component at ~umming Junctlon 319 modlfle3 the input to power operatlonal amplifler 313~ and thererore 1~8 output l at output termlnal 315, lnver~ely proportional to the ZO l di~ference between inputs o~ o~set ampll~ier 311 as will be e~plalned below.
, Al~o comblned at summing Junctlon 319 ls the i dl~rerential dlther 3ignal component input at terminal 310 l whlch is ~ed through dither ~ummlng re~istor 327 to ~umming ~unction 319. Ttne dif~erential dither si~nal component 1 added to the control and o~fset signal~, thereby modl~ying the output of power operational ampllfler 313 and the di~rerential output signal at output terminal 315. The comblnlng o~ control, o~fset and dither signals i3 permltted to occur at ~ummin~ Junction 319 up to the saturation point o~ solld-state power operational ~mplifier 313. It i to be I' noted that the dither slgnal component is always present in 5 ~I the dif~eren~ial output signal st terminal 315, re~ardless o~ whether the control lnput signal varies between zero and +6'Y.
The second half o~ the di~erentlal Yalve driver ~ circultry and operatlon thereof is the same as t~e fir~t lO ~¦ hal~ clrcuitry, except ~he polarity iY rever~ed and there is Il r.o dither 31gnal to combine wlth the control and offset ¦~ signal~. A control slgnal current from inout terminal 309 1~ passes through monitorln~ ~unctlon 323, control summing l resi3tor 329, summing Junction 330, and to the negatlve t-) 1~ ~ lnput o~ power operatlonal ampl~ier 314. The positl~e (+) tnput to amplifler 314 1~ ~rounded. The dirrerential Yoltage output o~ power operatlonal ampllfier 314 at termlnal 316 ~ i~ dete~mined by t~e value of reedback resistor 331 and the 1 polarlty of the control Yoltage at input terminal 309. ~hen 201 inout terminal 309 ls negative (-), output terminal 316 will I be negative (-) and vice versa.
Orfset ampllfler 312 po~itlve ~ 1-) is conne~ted to control sl~nal monitor Junction 328 by ~ay of reslstor 332 ~ ~or the purpose o~ senslng the amplitude and polarity o~ the 25l~ control slgnal at input terminal 3Q9. Amplifier 312 ¦ negatlve (-) or re~erence input ls connected between volta~e ~ dlviding resl~tors 333 and 334, the latker belng connected ¦ to a +6 re~erence source . As sumlng a~ above lnput terminals ~5~

~! 309-, 308+, of~set ampll~le~ 312 ~las no output because lt only compares posltive lnput slgnals.
However, when input termlnal 309~, 30&- condltion Il ari~es, o~set ~mpli~ier 312 compares the posltiYe varlable 5 ~ nal at monitorlng ~unction 328 with the po3itive reference Il 3ignal across re31stor 333. The di~rerence between inputs '.1 i8 ampli~ied by ofrset ampllfier 312 and output to o~fset ~unctlon 335 as a posltive o~set volta~e component. The magnltude o~ posltive o~f~et volta~e st o~set Junctlon 335 0 1 i3 detsrmined by the value o~ feedback re~istor 336 and ~he voltage dlvid~ns resistor 333, these belng selected to produce the negative orfset require~ent ~or the electro-alve char~cterlzed in FI~. 5 by curve lSS.
The o~set voltage component at ~unctior. 335 is 15i red through o~fset resistor 337 to ~umming ~unctlon 330 where lt ls combined with the dlf~erentlally Yariable control volta~e produced by control current ~low~ng through control I ~umming resl~tor 329. Thus, a posltlYe offset voltage component at 3umming Junction 330 modi~les the tnput to 20, power operational ampli~ier 314, and therefor~ lts output at I output terminal 31~, lnversely proportlonal to the dif~erence between lnputs o~ offset ampli~ier 312 as will be explained as ~ollows.
I Operation of both first and second halves of 25l differential valve drivers 256 to 259 will now be described.
Assuming the potentiometer 286A~ 286B ~liders are centered ! and remote control device 240 has zero output on output ~ leads 287, 288. A zero voltage appear~ at control signal l l ~l -53- , ', ;

3S~3~

lnput termlnal~ 308, 309, and at respective monitorin~
Junctions 317, 328. This produce~, minlmum positlve dlf~erence signals across re~pective lnputs o~ o~fset ampll~i~r~ 311, , 312. Thi~ produces equal posltlve ofYset slgnal component~
5 l, at summing ~unctions 319, 330, and there~ore equal positi~e ~i dri~er output slgnals at output termlnals 315, 31~. Conse-quently, the B, W termlnals have equal positive sl~nal~
Il bucking each other ln ~orce motor coll 123, thereby causin~
I ~orce motor armature 124 to assume a centered positlon.
101~ ~ence, in FIB. 4 the pilot Rpool 14~ in pilot sta~e 104 and po~er spool 167 ln power tage 105 assume a centered or neutral position.
~¦ When potentlometer 286A, 2~6B sliders move very ¦ sllghtly toward the down po~ltlon, a finite po~itive and 15l negatlve signal ls produced at output leads 287,28~, 1 l reYpectively, proportional to sllder sha~t movement. Thl~ ¦
¦~ establlshes a flnite positlve and negative input control signals at lnput term~n 19 308 9 309~ respec~ively~ as well ¦ a$ at flrs~ and second half monitoring ~unc~lons 317, 328, 20 ~ respectiv~ly. Inasmuch a~ offset ampllf~ers 311, 312 only I amplify positlve differences at thelr di~ferentlal lnputs, ¦ only o~rset ampllrler 311 produces the positive of~et signal component at summing ~unctlon 319 in reqpon~e to the l ~lnlte positive lnput at monltorin~ ~unctlon 317. Of~set 25 I ampli~ler 312 lnput becomes ~ero because o~ a flnite ne~ati~e input control ~ignal at monltorin~ ~unctlon 328.
The net ef~ect o~ thls at valve drlver output termlnalq 315, 316 l~q a rlnlte posiklve control 3ignal !

3 3~

combined wlth the po~lti~e ofrset slgnal at terminal 315 and ~inite negatlve control signal at termlnal 316. Thls causes ~ a B~, W- ~ignal condltion at force motor coil 123 which il i~medlately moYes armature 124 upward proportional to the of~set sl~nal and the poslti~e ~inite input ~ignal. In FIG.

4, pilot stage piston 135 immediately pull~ on power ~pool 167 to o~ercome its ofrset at cyllnder 1 port and allows a proportionally flnite power ~luld outflow ~rom cylinder 1 ,~ port to begln immedlately.
10l¦ As potentiometer 2&6A, 2863 311der~ are moved to ! the full down posltlon, an increasln~ly larger po ltive and negative input control siænal appears at monitoring ~unction~
I¦ 317, 328, respectively, as well as summing Junctlons 319, I 330, respectlvely. By sulta~le cholce of volta~e divlder 15l reslstors 322, 323 and ~eedback reslator 325 in what wlll be re~erred to as ~he posttive of~set ampli~ler 311, the positiYe off~et s~nal component at su~min~ ~unction 319 wlll Yary lnversely proportional to the input control slgnal at terminal 308.
The inverse relationship continues until the monltored and re~erenae lnputa Or positlve offset amplifler ~¦ 311 are equal, at whlch point ampllfier 311 saturate3 and producea its maximum positlve o~et slgnal at summlng ¦ ~unction 319. The positi~e lnput control volta~e moni~ored 25 l at ~unction 317 continues to lncreaae beyond the ~aturation point of amplifier 311 until the combineà control, offset and dither 3igna.1a at summing Junction 319 cauae power operatlonal ampll~ier 313 to saturate wlth a positive output voltage at output terminal 315.

3~

As the negatlve control ~lgnal lnput at termlnal 309 lncrea~es, so doe~ the control slgnal at summing ~unction 330. There 1~ no negatl~e o~set ~lgnal component at summing ~unction 330 becau3e of the difference in polarlty o~

5, monitoring and re~erence signal~ at the lnputs o~ ~hat wlll be re~erred to a~ the negative off~e~ ~mpllrl2r 312.
Nevertheless, the negatlvely variable control si~nal at summing ~unction 330 ~111 cau~e power operat1onal ampllrier Il 314 to produce a negative output signal at output terminal 10~, 316 proportional to the negatlve control signal i.~put at I terminal 309.
il As a val~e driver developes a dl~erentlally varying output si~nal at output terminals 315l J 316-, the I¦ B~ W- slgnal in ~orce motor coil 123 varle~ proportionally 151j to cau~e pilot sta~e piston 135 and power ~pool 167 to vary cylinder 1 port out M ow propor~lonal thereto.
When potentiometer 286A, 286B ~liders are moved opposltely from thelr cent~red po~itlon toward the up position~ ¦
,I the pol~rity of their output 3i~nal3 reverse at output lead~
20~ 287, 288~ as does the polarity o~ the respectlve control ! ~lgnal at input termlnal3 308, 30~ and ~irst and second half ¦ monitorln~ Junctlons 317, 328. At ~ir~t~ a flnite negatlve and po~ltlve control ~i3nal t3 produced at lnput terminals Il 308, 309, then a larger magnitude control ~l~nal, both 25 11 proportlonal to potentlometer 286A, 286B ~lider sha~t position. Both halve~ of the valve drlYer circuitry now operate oppo~ite to that described abo~e.

,1 , ~ r~3 ~

The positive of~et ampllfier 311 does not produce an o~f~et ~ignal component at summing ~unction 319 becauæe the control lnput terminal 308 ls ne~atlve, thu~ cau~ing the I monitorlng lnput o~ ampllfier 311 to be negative wlth re~pect 5 1¦ to its po~itive reference signal input. Thererore the power opera~ional amplirier 313 output w~ll now be negative at outpu~ terminal 315 lnstead Or po~itive a~ above.
The negative o~rset ampllfler 312 does produce the Il negatlve of~set ~ignal tha~ varles inver~ely proportlonal at lOIl summing ~unctlon 330 because the control input terminal 309 i~ is pos~tlve, thus causing the monitoring input of ampl~fier 312 to be po~ltive with re~pect to its posltive rererence s~ gnal input. Although the o~rset signal produced by o~rset ~ amplifier 312 was lnitiated by a posltlve monltored 31~nal 15~ at lnput terminal 309, its e~fect on power operatlonal amplifler 314, and there~ore on force motor coil 1~3, ls the opposite Or the posltlve o~f3et signal component from ampl~rler 311. The output ~rom off~et ampll~ier 312 fed to summlng ~unctlon 330 wlll be re~erred to 8$ the ne~at~ve 20 ¦ orfset si~nal component and this corresponds to the negatlve o~set portlon Or curve 186 in FIG. 5.
¦ The comblned positive-polarlty control and offset slgnal~ at summlng ~unction 330 are ampll~led by power l operatlonal amplifier 314 and output at valve drlver output 25~ termlnal 316 as a po31tive si~nal. Thls causes a B-~ W+
~i~nal relationship in force motor coil 123 that cau~e~
armature 124 to move downward or oppo~lte to that described above. Thi~ e~ectively cause~ pilot ~pool 149 in FIG. ~ to , r~33~il i~

move downward, pilot piston 135 ~ld power spool 167 pushed on to lmmediately overcome power .~pool 167 of~et with ll respect to cylinder port 2. Power ~luid outflow from ,I cylind~r 2 port i3 proportional to the 30~-~ 309~ input 5 I! control si~nal.
In summarlzlng the FIG. 10 dlfferent~al valve dri~er operation~ lt ha3 been shown that a di~ferentlal I proportional input ~lgnal at control signal lnput terminals I 308, 309 ~ill produce a correspondlng dt~ferentlal propor-10~¦ tional output slgnal at output termlnals 315, 316. Further~1, that a dither ~ignal component and an o~set signal component '' are comblned with the v2riable control sl~nal ts produce the dir~erentlal output sl~nal. Moreover, that elther a pos~ti~e 1~ or a negatiYe orf~et signal component i~ producedg one at a 15 il time, by mon~torin~ a po~ltive control sl~nal at one of the control signal input~ 308, 30g when the other lnput is ~ negstive. mhe o~f~et signal compon~nts correspond to the ¦ deadband of an electro-control valve such 3$ iS shown in I FIG. 4.
201, To complete the de~crlptlon Or low Yoltage control3 71, of which the aboYe-described valve drlvers 256 to 26g are a ma~or part, re~erence wlll now be made to FIG. 11 schematic diagra~m of tram half-speed circuit 271. This clrcuit 271 i~ c:onnected between rlght and le~t ~ram pro-25~ portional remot~! control deYices 245, 246 and dlf~rential valve drivers 2'i9, 260 in control channels 4, 5. Purpose o~
tram hal~-speed clrcult 271 i3 to electronically monitor cutter head drl~e motor 35, 36 operation and automatlcally ll l ~l -58-3~

reduce to one-hal~ the proportional rorward speed, but not rever~e speed, Or hydraullc-driven right and left tram~ 29, 28 establlshed by proportional remote control devlces 245, ,1 246. When cutter head~ are not operating, both tram~ are 5 i permitted to operate up to full forward or re~erse proportional ~peed under channel 4, 5 re~ote control, unles~ overrldden by control channel 13 step type remote control of tram hal~-speed hydraulically as de~cribed below.
11 Tram hal~-~peed circuit 271 ha~ two mode~ of 101l operatlon, namely, hal~-speed and full-speed modes. These are determined by solid-state lo~ic control ~ate~ 33a, 33g operating in re~pecti~e ri~ht and le~t tram ~peed control circutts, ln unison, in re~pon~e to a hl~h or low monttoring 1 ~ignal recei~ed oYer lead 212 ~rom the cutter head stop 15 ¦ relay ~6 ln FIG. ~A. A high monltoring sl~nal on head 212 indicates the cutter head stop relay K6 1~ energized and the cutter heads are not operating. A low mon~toring ~i~nal on lead 212 indicat~s the cutter head~ are not stcpped but are ~ operating.
20l Control gates 338, 339 each include solld-3tate comparator, logic circult~, and relay clrcuits K9, X10, respecti~ely, which operate slmultaneou~ly in respon~e to the monitorin~ nal on lead 212. Control ~ate 338 I¦ comparator operates a&ainst a ~6Y re~erence source and 2~l control gate 33~ comparstor operates aEain~t a -6Y re~erence source.
A high monitoring ~ignal at control gates 338, 339, indicating stopped cutter heads, closes normally open 5~
.1 relay contacts K9, X10 and bypasse~ corre~ponding ri~ht and left tram hslf-~peed ad~u~ting network~ 3403 341. This establi~hes a ~ull-speed operatln~ mode and connects the I right and le~t tram remote control 3i~nal9 on leads 301, 302 5,l and 303, 304 dlrectly to re~pective output lead~ 342, 302 and 343, 304 ln network~ 340, 341. In thi~ manner, the ~ull right and left tram remote control 91 gnal~ are applled directly to ~alYe dri~er 259, 260 inputs.
Il Each half-speed adJusting network 340 3 341 consl~t~
1~ll o~ a resi3tor 344, 345 serlally connected with a respective rheostat 346, 347, and inserted serially between respectl~e lnput lead3 301, 303 and output leads 342, 343. Rheostat~
346, 347 provide ~or ~ndiYidual half-speed tram ~o o~ercome ¦ di~rerences in right and left tram 29, 28 traction mechanisms.
15 ll A low monitoring 31gnal at control gates 338~ 339, indicatlng operatlng cutter head~, open relay contacts X9, K10 and directs rlght and left remote control sl~nal~ ~rom de~ices 245, 246 through hal~-~peed adJu3tin~ networks 340, 341. Thl~ e3tablishes the half-3peed operating mode and 201 reduces by about 50~ the rlght and le~t tram output 3ignal5 on leads 342, 302 and 343, 304 whlch feed the inputs to corre~pondlng valve driver~ 259, 260. Thus, it can be seen that chan~in~ o~ the monitoring ~lgnal from hlgh to low, I indlcatlng a chan~e ln cutter head operatlon from stopped to 25l operating, auton~ltlcally changes control o~ rlght and left tram forward speed ~rom ~ull-speed to hal~-~peed operatlng mode of tram hall'-~peed clrcuit 271. Inasmuch a3 the half-~peed adJustln~ networ~s 340, 341 are only ln the ~orward i ~peed output leads 301, 303, they do not arrect the reduction of revers~ tram ~peed control sl~nal from remote control deYice~ 245, 246.

IlOPERATION OF MINER REMOT~ CONTROL SYSTEM
.1 _ _ _ 5 ¦Operation Or the intrinslcally ~a~e remo~e control system for continuous minlng machlne 20 w~ll now be descrlbed ~ith reference to TABLE 1 and the drawin~, particularly ¦I FIG3. 1, 2, 3, 7A, 7~, 8A, 8B. It ls a sumed that remote/
~ manual switch 66 on mlner 20 is ln the remote position, 10~I thereby permlttln~ operator 24 to remotely control miner 20 from hand-held miner remote control pend~nt 25 trailinæ
miner 20, Further~ that master power-on switch 1~7 on pendant 25 19 turned on to energize the intrln~ically sa~e l remote control system with +6'V and -6'V.
15l me control functions that follow ~re lnltlated by ¦l operator 24 fro~ indl~idual remote control deYices on mlner remote control pendant 25. ~ydraulic pumps and electrically drlven cutter heads must be started in sequence be~ore other , remote control ~unctlon~ msy be perrormed. First, pump 20l switch 198 must be closed momentarily to the on position ~hich starts dua:L hydraulic pump drl~e motor 57 instantly, and a~ter a tlme delay automatically starts varia~le ~olume hydraullc pump motor 5~.
l Dr~ Ye motor 57 i~ coupled to dual constant volume 25 ll hydraulic pumps 58 whlch lnclude i~olated pllot oll system 89 and power oil ~y3tem 92. Iqolated pilot oll system 89 13 connected to only pllot ~ta~es 104 ln maln bank o~ pro-portional electro-control ~al~es 61 u~ed ln control channels ,1 1 , I
~1 3~

.

' 1 to 6 described below. Power oll system 92 i~ connected to auxillary bank o~ pilot on/o~ electro-control valve~ 62 used in control channels 7 to 14 and to other hydraullc Il loads on mlner 20. Drlve motor 5g is coupled to varlable 5 1I volume hydrau}ic pump and system 60 which i8 connected to i power stages 105 of main valve bank 61, the latter powerlng 'i the miner proportlonally controlled hydraulic loads ln control channels 1 to 6. Thus, all hydraulic power and !I control systems are now operating.
10l~ Second in seQuence star~ing, cutter head swltch i 19g 13 clo3ed momentarlly to the on posltion whlch ~tart~
lert cutter head drive motor 35 instantly, and a~ter a time delay automatlcally starts rlght cutter drive motor 36. In I practice, cutter head drive motor3 35, 36 drive left and 151 ri~ht cutter heads 33, 34. The~e c~tter head drl~e motors are interlocked w~th the variable volume hydraullc pump drive motor 59 an~ may actually be started at any time after Il pump motor 59 i8 operating.
!~ Pump and cutter head ~witches 198, lg9 both have a 20 I momentary o~ positlon whlch may be used to stop respective Il pump drlve motors 57, 59 and cutter head drive motors 35, 36 ,i in reverse starting sequence. In addltion, emergency ~top ~¦ switch may be pushed momentarily to stop all pump and cut~er Idrlve motors 57, 59, 35, 369 slmultaneou~ly.
25lOperatlon o~ control channels 1 to 6 lnrolv ng the main bank of proportional electro-control valves 61 may occur any time a.~ter pres3ures in the hydraulic system~ have bullt up to thelr respectlve operating levels. Reference to 33~3 dead~an remote control deYice~ below rnean that thelr control . action i~ contlngent upon operator 24 flr~t pres~in~ the deadman swltch lncorporated into the control devlce.
~ hene~er the deadman switch is relea~ed 3 the control function 5ll cease~. A de~crlptlon o~ proportlonal control channel3 1 to Il ~ fQllo~

Control channel 1 i~ devoted to controlling the elevation of cutter boom 30 anywhere between up and down , llmlts 32, 31 by ~eans o~ remote control de~rice 242, valve 10j drlver 256 and ~orce motor 272 acting on cukter boom valve g8. When control deYice 242 is centered and produces a zero ¦ output ~ignal~ valve 98 1~ neutral and holds cutter boom 30 ,~ midway between up and down positions 32, 31. Up control il produc~s a proportlonal B-~ W+ si~nal on force motor 272 15~ which act~ on valve 98 to cause cutter boom 3~ to elevate a~ !
~ar a~ upper limit 32. Do~n control produces a proportlonal B~ W- sl~nal on force motor 272 which act~ oppo~itely to the up slgnal and cau~e~ cutter boom 30 to lo~er a~ ~ar a~
I, down lir~lt 31.
Con~rol channel 2 i~ devoted to controlling I¦ conYeyor 47 lirt anywhere between up and down limit~ 49, 48 I by means o~ remote control device 243~ ~al~e drlYer 257 ~nd I and force motor 273 acting on conveyor lift valve 99. When l deadman remote control device 243 i~ centered and produce~ a 25¦ zero output signal, val~e 99 ls neutral and hold~ conYeyor 47 midway between it8 Up and down po8itlon~ 49, 48. Up control produce~ a proportional B~ J~ nal on ~orce motor 273 which act~ on valve ~9 to cau~e conveyor 47 to lift a3 Il ! i ~ 5~ 3 ~

far as it~ up~er llmlt 49. Down contr.ol produces a propor-tional B-, W+ signal on ~orce motor 273 which acts oppositely to the up signal.
Control channel 3 is devoted to controllin~ conveyor I' , 5l 47 tai} swing horizontally from center positlon 50 to anywhere bet~een left and rlght limits 51, 52 by means o~ dea~man I remote control devlce 244, valve driYer 258, and force motor Il 274 actlng on conveyor tail s~ing valve 100. When dead~an Il remote control de~lce 244 i~ centered and produces a zero 101 output si~nal, Yalve lO0 18 neutral and holds conveyor 47 tall s~in~ at center po~ition sa. Le~t control produces a proportlonal B+, ~- slgnal on ~orce motor 274 which acts on valve lO0 to cause conveyor 47 tail to swing horizontally I fro~ center posltlon 50 le~tward anywhere with~n le~t limit 15j 51. Ri~ht control produces a B-, W~ sl~nal on ~orce motor 274 which act3 opposltely to the left sl~nal and cause~
conveyor 47 tall to swin~ horiæontally from center positlon 50 r~ght~ard anywhere wlthin rlght llmit 52, I¦ Control channels 4 and ~ are devoted to controlllng 201~ rl~ht and le~t tram 29~ 28 speed, ~orward and reverse d~rectlon, and forward halr-speed wlth cutter heads 33, 34 operating. Both control channel~ 3 and 4 operate in unison i to remove coal from seam 21, but lndependently, or in l oppo31tion to each other to 3teer the fore/a~t/turn~ng 25l dlrection o~ miner 20. Control channel~ 4 and 5 are con-trolled by means of deadman right and left tram remote control devlce~ 245, 246, tra~ half-speed circult 271, valve dri~ers 25g, 260 and ~orce motor~ 275, 276 acting on rlght and le~t tram valves lOl, 102.

.l ~4 !l ~' 3~ .

~hen deadman remote control deYices 245, 246 in control channels 4 and 5 each ls centered and produce~ a zero output si~nal, valYes 101, 102 are bo~h ln a neu~ral , posltion and maintaln right and left tram~ 29, 28 at a ~tand 5 1l stlll. Forward control produce~ a proportional B-~ W~
signal on force motors 259, 260 which act on ~alves 101, 102 to cause tram~ 29, 28 to move mlner 20 ~orward at a full ~peed proportional to control po~itlon. When cutter head ¦ motor~ 35, 36 are operatlng~ tram half-3peed circult 271 i~
10 1 activated and automatlcally limlts forward tram 293 28 speed to about 50~ proportional ~or~ard speed. Reverse control ~¦ produce~ a ~, W- slgnal on force motor~ 275, 276 whlch act on Yalves 27~, 276 oppo81 tely to the rorward signal~ that Il i3, to cau~e trams 29, 28 to mo~e mlner 20 at a ~ull reverse 151~ speed proportional to control po~ltion. ~here i~ no tram halfspeed control in elther tr~m reverse speed control. It should be noted that mlner 20 may be ~teered rl~ht or left 3 . ~orward or rever~e~ or turned about a vertlcal a~is by l moYing controls on remote control de~lces 2l~5~ 246 dlr-20~ ~erentially or oppositely wit~ re~pect to each other.
,il Control channel 6 i3 devoted to controlling theelevation o~ ~atherlng pan 44 anywhere between up and down ¦ llmlts 46, 45 by means o~ remote control devlce 247, valve l dri~er 261 and ~orce motor 277 actin~ on ~atherln~ pan valve 25~ 103. ~hen control device 247 1~ centered and produc~s a zero output sl~nal, val~e 103 i~ neutral and holds ~atherlng pan 44 midway between up and down limit~ 46, 45. Up control produces a proportional B-, W+ ~i~nal on force motor 277 ~ 3 ~

which acts on valve 103 to cau~e ,~athering pan 44 to elevate as rar a~ upper limit 4g. Down control produce~ a pro-por~lonal B~, W sign21 on force motor 277 wh~ch act~
i opposltely to the up ~i~nal and cau~es gathering pan 44 to lower as far as down llmit 48.
., Operatlon Or control channels 7 to 14 ln~olYing ! the auxiliary bank o~ pllot on~o~ electro~control valves 62 , may al30 occur any time arter pres~ures in the hydraul~c 1' system~ have built up to thelr re~ectlve operatln~ levels.
10~I A descrlption of on/off control channels 7 to 14 ~ollows:
Il Control channel 7 ls devoted to automatic dump ;I control remotely of variable Yolume hyùraulic pump system 60 Il by means of time delay devlce 202 ln the pump start circuit Il rather than a control de~ice on pendant 25 9 the valve driver 15 ll 2~2 connected to device 202, and a ~orce motor 278 acting on ¦ Yarlable volume pump dump control valYe 110. When variable volume pump sy~tem 50 ha~ been started by pump switch 198 and ls operating, time delay de~lce 2C2 does not become 1 act~vated but produces a B-, W+ step type ~ignal on force 20 1l motor 278 whlch acts on ~alve 110 to permit normal operation of pump ~y3tem 600 However, a preset tlme delay after pu~p sy~tem 60 i~ deener~ize~, time delay devlce 202 becomes acti~ated and produce~ a B+~ 3tep type si~nal on force l motor 278 ~hich acts on valve 110 to actuate a dump control 25l hydraullc clrcuit for pump 3ystem 60, thereby relievin~ pump system ~0 pressure so that on the next start ~equence drive motor 59 may start without pump load and allow ~ariable ~ 6-, i .
..

S~3~

, I volume hydraullc p~mp sy~tem 60 to bulld up pressure ~radually.
Thi~ minlmizes ~tarting load fluctuation~ ln hlgh voltage j source 55.
1, Control channel 8 i8 devoted to turnln~ on and o~f S,1 a hydraulic mechani~m ror oscillatlng le~t and rl~ht cutter head arms 37, 38 continuously between lert and ri~ht arm Il inward positlons 39, 40 and thelr outward posltlons 41, 42, 'i lndependently o~ cu~ter boom elevat~ on control by channel 1.
Il This control i~ ef~ected by rem~te control device 249, valve 10l c~river 263 and force mo~or 279 actlng on cutter head osclllator valve 111. 0~ control produceg a ~tep type B-, W~ sl~nal on force motor 279 whlch acts on Yalve 111 to lncapacitate the hydraullc cutter oscillator mechanism. On , control produce~ a ~te~ type B~, W- signal on ~orce motor 15~ ~hich acts on val~e 11l to turn on the hydraulic cutter oscillator mechanl~m.
Control channel 9 is devoted to rai~in~ and I lowerln~ hydraulic ~tabllizing Jack 53 on miner 20 by means l of remote control device 250, valve driver 264 and ~orce 20l~ motor 280 actin~ on stabllizin~ ~ack valve 112. Up and down control produces a ~tep type ~+, W- and B-, W~ signal on force motor 280 whlch act~ on valve 112 to rai~e and lower hydraullc tabillzlng ~ack 53 to respectlve up and down l po~itions.
251 Control channel 10 ls devoted to turnlng on and of~ maln water ~prays, ~d by miner water ho~e 54, by mean~
o~ remote contrc~l device 251, valve drlver 265 and ~orce motor 281 actinE on water deluge valve 113. On and o~

,~
.~ .

~ 3 ~

control produces respective B~ and B-, W+ step type control 3ignals on rorce motor 28'L wh~ch acts on valve 113 to turn the maln water spray on and off, respecti~ely.
I Control channel 11 ls devoted to turning on and 5 1l o~f Rater deluge~ ~ed by ~iner ~ater hose 54, by means of i remote control devlce 252, valYe ~rlver 266 and force motor 282 actlnæ on water deluge valve 114. On and of~ control produces respectiYe B+, ~- and B-, W~ step type control 1 3ignals on ~orce m~tor 282 which act~ on valve 114 to turn 10ll~ the water deluge on and o~f, respectlvely.
Control channel 12 i3 devsted to turning on and ,l o~ con~eyor 47 hydraullc drive motor by means o~ remote control deYlce 2~3, valYe drlver 267 and ~orce motor 283 ~l actlng on con~eyor run val~e 11~. On an~ o~f control produce3 15l~ reApecti~e B~ and B-, W~ step type control ~ignal~ on ',I force motor 283 which acts on ~alve 115 to turn conveyor 47 on and off, respectively.
Con~rol channel 13 is devoted to hydraulic ~wi~chlng 1~ from hi~h to low speeds o~ rlght and left tram 29, 28 20 il hydraulic drive motors by mean~ o~ remote control devlce 254, valve driver 268 and force motor 284 actlng on tram hal~-~peed ~alve 116. This control channel operate~ I
lndependently of' proportio~al control channels 4 and 5.
ll Hlgh and low ~peed control produce3 B~, W- and B-, W* ~tep 25l type control ~l~al~ on ~orce motor 2~4 which act3 on valve 1 116 to chan~e tram speed ~rom high to low ~peed, respectlvely.
¦ Control channel 14 is devoted to hydraullc switchlng rrom forward to reverse dlrectlon Or conveyor 47 by mesns o~

~ ~3~

remote control device 255, val~e driver 269 and force motor 285 actlng on conYeyor direction Yalve 117. Forward and Il reverse dlrectlon control produces B~ W-and B-, W~ step il ~ype control ~lgnals on force mo~or 285 which acts on val~e 5 l 117 to change conYeyor 47 dlre~tl~n o~ operatlon from i rorw~rd to revers~, respectlvely.
In the ~oregoin~ de3criptlon, the quantlty and type of proportlonal and on/off electiro-¢ontrol ~alves in ! each valve banks cl, 62 may be well sulted ~or retro~lttlng lOIl a continuou~ minin~ machine such as repre~ented by miner 20.
Howe~er, it will now be apparent that at le~st some, lr not all, o~ the step type control functior.~ descri~ed abo~e may be controlled wlth proportional type electro-control valYes I in new ins~allation~ where valve and pip~n~ ~pace constraints are not a3 severe a3 in older mining machlnes.
Finally, ~anual mode o~ operatin~ the ~iner remote control system will be descrlbed. Remote/manual ~witch 66 is turned to manual po~ition and it 15 aqsumed that cutter l head and pump ~witches l~9~ 198 were turned off ln 3equence.
Low Yoltage power supply 6~ i~ deenerglzed, consequently all remote control devices on pendant 25, all val~e drlver~ and the like ~n low voltage control~ 719 and all rorce motors ln val~e bank~ 61, 62~ are all incapacitated because they too ~l~ are deener~ized. Under this conditlon, constant volume-pump motor 57 and variable volume pump motor 59 may be stopped and started locally b~J respective manual ~top and start I pushbuttons 214--l, 214-3 and 214-2 and 214-4 in sequence.
I After that, left and rlght cutter head drlve ~otors 35, 36 l -6~-~ S~ 3 ~

may be ~topped and ~tarted sequentlally as above by local manual ~top and start pushbuttons 214-5 and 214-6, re~pectively.
When hydraul~c pressur,D~ build up~ hydraulic ~unctions in control channel~ 1 to 6 may be controlled indivldually by 5, manual oYerrides 106 in valve bank 61~ Hydraulic runctlons ln control channels 7 to 14 may be controlled lndlvidually ~il by manual o~errides 118 in ~alve bank 62. A retuxn to remote mode of operatlon o~ m~ner 20 may be made at any Il tlme.
10ll Based on the roregolng de~crlptlon o~ a pre~erred embodiment of this inventlon, it will be apparent ~rom the ~I descriptlon of the mlner hydraulic system that although 1~ electro-control ~al~es 98 to lC3 ln the main bank of pro-Il portlonal electro-con~rol 61 which are used for pr~por~ional 15, control Or hydraulic load3 herein, may al30 be u~ed elsewhere to control on~of~ hydraullc loads. Ll~ewi~e~ elec~ro-I control valves 110 to 117 in the auxiliary banX oP plloton~o~ ~al~es 62 whlch are u~ed ~or on/o~f control o~ load~
1~ hereln, may also be used el3ewhere ~or proportional load 20 11 control. In addltlon, lt will also be apparent rrom the descriptlon o~ the miner electrlcal sy~tem that dlf~erential proportlonal ~alYe drlver~ 256 to 26g each contain Ylrst and econd clrcult hal~es wherein each hal~ contalnln6 an ofrset l~ ampli~ier may be u~ed el~ewhere alone ~or a proportlonal valve load not having a dlrrerentlal operatlng re~ulrement.

_7,~_

Claims (27)

1. Claims We claim:
   l. A mining machine remote control system for controlling one or more fluid-powered machine operating functions, said system comprising:
   (a) electro-control valve means for con-trolling the machine operating functions in response to operating function control signals, at least one valve in said means having proportional flow and deadband characteristics, (b) pendant means producing a separate operator-initiated remote control signal for each said machine operating function, at least one of these remote control signals having valve-related proportional characteristics, and (c) controller means receiving the separate remote control signals for producing the separate operating function control signals, at least one of these operating function control signals having the valve-related proportional flow char-acteristic modified by an offset signal component for overcoming valve deadband characteristics.
2. 2. The system according to claim l wherein the pendant means and the controller means incorporate intrinsically safe circuits.
3. 3. The system according to claim 1 wherein the controller means includes a dither oscillator and produces at least one offset-modified proportional operating function control signal further modified by a dither signal component for minimizing additional valve frictional characteristics.
4. 4. The system according to claim l wherein the pendant means and controller means each have differential type proportional remote control signals and corresponding proportional operating function control signals.
5. 5. The system according to claim 1 wherein the pendant means produces a differential type proportional remote control signal, and the controller means includes means for monitoring the differential proportional remote control signal and produces the offset signal component.
6. 6. The system according to claim l wherein the pendant means produces a differential type proportional remote control signal, and the controller means includes differential valve driver means for monitoring and amplifying the differential proportional remote control signal, and in response thereto selectively applying either a positive or negative type offset signal component modification to the differential proportional operating function control signals.
7. 7. The system according to claim l wherein the pendant means includes a deadman switch incorporated in at least one remote control signal producing device to insure human operator participation in remote control of said mining machine.
8. 8. The system according to claim 1 wherein there is incorporated means operatively associated with the pendant means and controller means for providing remote and manual operating modes of the remote control system.
9. 9. The system according to claim 1 wherein there is incorporated test switch means operatively associated with solid-state control devices in the controller means.
10. 10. The system according to claim 1 wherein the pendant means includes individual remote control devices for pump operation, material cutting gathering, conveying and spraying, and machine tram propelling, steering and position-ins 3 and jacking.
11. 11. The system according to claim l wherein the pendant means and the controller means includes means for starting at least one hydraulic pump, and if desired other loads, automatically in sequence responsive to one of the remote control signals.
12. 12. The system according to claim l wherein the controller means includes circuit means for automatically reducing remote control means tram speed a predetermined amount in response to monitoring the operation of another machine operating function.
13. 13. The system according to claim 1 wherein the controller means includes circuit means for automatically reducing remote control means tram speed signal a predeter-mined amount, and limited to one direction of tram travel, in response to monitoring the operation of another machine operating function.
14. 14. The system according to claim 1 wherein the electro-control valve means includes one or more electrically operated valves with a hydraulic servo controlled valve stage having a mechanical feedback element for nulling the proportional valve operation.
15. 15. A mining machine system for remotely controlling one or more fluid-powered machine operating functions, said system comprising:
    (a) a pressurized fluid source, (b) electro-control valve means including a hydraulic servo-controlled pilot stage valve for each machining operation function which receives a separate operating function control signal, each pilot stage valve connected to the fluid source and to a load having proportional flow and/or valve deadband characteristics, and (c) remote control means initiated by an operator for the separate operating function control signals, at least one of said signals having valve-related proportional flow characteristics and/or modified by an offset signal component for overcoming the valve deadband characteristic.
16. 16. A mining machine system for remotely con-trolling one or more fluid-powered machine operating functions, said system comprising:
    (a) a pressurized power fluid source susceptible to contamination, (b) a pressurized control fluid source isolated from the power fluid source, (c) electro-control valve means including a hudraulic servo-controlled pilot stage valve for each machine operating function which receives a separate operating function control signal, each pilot stage valve connected hydraulically to the control fluid source and coupled mechanically to a corresponding power stage valve which is connected hydraulically to the power fluid source, at least one power stage valve having proportional flow and deadband characteristics, and (d) remote control means initiated by an operator for producing the operating function control signals, at least one of said signals having valve-related proportional flow characteristics modified by an offset signal component for overcoming the valve deadband characteristics.
17. 17. The system according to claims 15 or 16 wherein the mining machine operating functions include pump operation, material cutting, gathering, conveying and spraying, and machine tram propelling, steering and po positioning, and jacking.
18. 18. The system according to claims 15 or 16 wherein a pressurized source includes a motorized variable volume pump having a dump control activated by a valve in the electro-control valve means.
19. 19. The system according to claims 15 or 16 wherein electro-control valve means with pilot stage hydraulic servo includes a mechanical feedback element for nulling proportional valve operation.
20. 20. The system according to claims 15 or 16 wherein electro-control valve means with pilot state hydraulic servo comprises an electrical force motor acting on a pilot stage spool in cooperation with a mechanical feedback sleeve and pilot stage piston.
21. 21. The system according to claims 15 or 16 wherein electro-control valve means includes a manual overide mechanism.
22. 22. The system according to claims 15 or 16 wherein the means for producing operating function control signals includes intrinsically safe circuits.
23. 23. The system according to claims 15 or 16 wherein the remote control means comprises:
    .1 pendant means producing a separate operator-initiated proportional remote control signal for each said machine operating function, and .2 controller means receiving the separate remote control signals for producing separate proportional operating function control signals.
24. 24. The system according to claims 15 or 16 wherein the remote control means produces differential type proportional control signals.
25. 25. The system according to claims 15 or 16 wherein the remote control means produces the proportional control signals modified by a dither signal component for minimizing valve frictional characteristics.
26. 26. The system according to claims 15 or 16 wherein the remote control means includes circuit means for reducing machine tram speed a predetermined amount in response to monitoring another machine operating function.
27. 27. The system according to claims 15 or 16 wherein the remote control means includes circuit means for reducing machine tram speed a predetermined amount, and limited to one direction of tram travel, in response to monitoring another machine operating function.