文献翻译自移式液压支架Word格式文档下载.docx

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Self-AdvancingHydraulicPoweredSupports

Modernlongwallminingemployshydraulicpoweredsupportsatthefacearea.Thesupportnotonlyholdsuptheroof,pushesthefacechainconveyor,andadvancesitself,butalsoprovidesasafeenvironmentforallassociatedminingactivities.Thereforeitssuccessfulselectionandapplicationaretheprerequisiteforsuccessfullongwallmining.Furthermore,duetothelargenumberofunitsrequired,thecapitalinvestedforthepoweredsupportusuallyaccountsformorethanhalfoftheinitialcapitalforalongwallface.Thereforebothfromtechnicalandeconomicpointsofview,thepoweredsupportisaveryimportantpieceofequipmentinalongwallface.

Theapplicationofmodernpoweredsupportscanbetracedbacktotheearly1950’s.Sincethen,followingitsadoptionineverypartoftheworld,therehavebeencountlessmodelsdesignedandmanufacturedinvariouscountries.Butunfortunately,therestillisnouniformsystemofclassification.

Asimplifiedclassificationisusedinthissection.sinceapoweredsupportconsistsoffourmajorcomponents（i.e.,canopy,cavingshield,hydrauliclegsorprops,andbaseplate）,thewaysbywhichtheyareinterrelatedareusedforclassification.Inthisrespect,twofactorsaremostimportant:

（1）presenceorabsenceofacavingshield-ifacavingshieldisincluded,thesupportisa“shield”type,otherwise,aframeorachock;

（2）numberandtypeofarrangingthehydrauliclegs-sincesupportcapacityisgenerallyproportionaltothenumberofhydrauliclegs,itisimportanttospecifythenumberofhydrauliclegsthatasupporthas.Furthermore,thewaythehydrauliclegsareinstalledisimportant;

forexample,averticalinstallationbetweenthebaseandthecanopyhasthehighestefficiencyofapplicationwhereasaninclinedinstallationbetweenthebaseandthecavingshieldhastheleastefficiencyinsupportingtheroof.

Basedonthisconcept,therearefourtypesofpoweredsupport,thatis,theframe,chock,shield,andchockshield,inorderofevolutionoftheirdevelopment.However,itmustbenotedthatthetrendofdevelopmentineachtypeissuchthatitbecomeslessdistinguishableintermsofapplication.

Thefourtypesofroofsupportscanbeobtainedforeitherlongwallretreatingoradvancingsystems,andtheyareavailableinstandard,one-web-back,andimmediateforwardsupport（IFS）versions.

Withthestandardsystem,thewinningmachinetakesacutoraslice,andthearmoredfaceconveyorispushedoverbythehydraulicramsthatarefixedtothesupportunits.Thesupportunitsthenareadvancedsequentiallytotheconveyor.Withtheone-web-backsystem,asupportissetbackfromtheconveyorbyadevicethatautomaticallykeepstheleadingedgeofthesupportatafixeddistancefromtheconveyor.Thisallowseasyaccessthroughthefaceandemploysthestandardmethodofadvancing;

i.e.,pushingtheconveyorfirst,andthenadvancingthesupport.

WiththeIFSsystem,thesupportunitisadvancedtotheconveyorimmediatelyafterthecuttingmachinehaspassed,andtheforwardcanopyofthesupportunitislongenoughtosupportboththerecentlyandnewlyexposedroofsections.Afterthesupportshavebeenadvanced,theconveyorispushedover.

FRAME

Theframesupportisanextensionofthesinglehydraulicpropsconventionallyusedunderground.Thusitisthefirsttypedevelopedinmodernself-advancinghydraulicpoweredsupports.Itinvolvessettinguptwohydraulicpropsorlegsverticallyintandemthatareconnectedatthetopbyasingleortwosegmentedcanopies.Thetwosegmentedcanopiescanbehinge-jointedatanypointbetweenthelegsorinfrontofthefrontleg.Thebaseofthetwohydrauliclegsmaybeacircularsteelshoeweldedatbottomofeachlegorasolidbaseconnectingbothlegs（Fig.8.8）.

Generally,aframesupportconsistsoftwoorthreesetsofhydrauliclegs.Thesetmovingfirstisthesecondaryset,thesetmovinglateristheprimaryset.Thereisadouble-actingraminstalledbetweeneachset.Thepistonoftheramisconnectedtothesecondarysetandthecylindertotheprimaryset.Duringsupportadvance（Fig.8.9）,theprimarysetissetagainsttheroofwhilethesecondarysetisloweredandpushedforwardbythepiston.Havingreachedthenewposition,thesecondarysetissetagainsttheroofwhiletheprimarysetisloweredandpulledforwardbythecylinder.Thedistanceofeachadvancerangesfrom20to36in.（0.50~0.91m）.

Fig.8.8Framesupport

a-primarysetb-secondaryset

ABC

Fig.8.9Methodofadvancingtheframesupport

Theframesupportisverysimple,butmoreflexibleorlessstablestructurally.Thereareconsiderableuncoveredspacesbetweenthetwopiecesofcanopywhichallowsbrokenroofrocktofallthrough.Consequently,theframesupportisnotsuitableforaweakroof.Frameshavebecomeseldomusedbecausetheyarelessstableandrequirefrequentmaintenance.

CHOCK

Inachocksupport,thecanopyisasolidpieceandthebasemaybeeitherasolidpieceortwoseparatepartsconnectedbysteelbarsattherearand/orthefrontends.Inbothcasesalargeopenspaceisleftatthecenterforlocatingthedouble-actinghydraulicramwhichisusedtopushandpullthechainconveyorandthechockinawholeunit,respectively,adistinctivedifferencefromtheframesupport.Thissetupdesignedforthinseamswithtwolegsinthefrontandfourlegsintherear,separatedbyawalkwaisalsousedintheshieldsandchockshields.

Again,allhydrauliclegsareinstalledverticallybetweenthebaseandthecanopy（Fig.8.10）.Thenumberoflegsrangesfromthreetosix,butthefour-legchocksarebyfarthemostpopularones.Thesix-legchocksarey（Fig.8.10c）.Forthesix-legchocks,thecanopyisgenerallyhinge-jointedabovethewalkway.Mostchockarealsoequippedwithagobwindowhangingattherearendofthecanopy.Thegobwindowconsistsofseveralrectangularsteelplatesconnectedhorizontallyatbothends.

ABC

Fig.8.10Schematicsofvariouschocksupport

Inmostchocksupports,therearehingejointconnectionsbetweenthelegsandthecanopyandbetweenthelegsandthebase.Butinordertoincreasethelongitudinalstability,itisreinforcedmostlywithabox-shapedsteelframebetweenthebaseandeachleg.Alegrestoringdeviceisinstalledaroundeachlegatthetopofthebox-shapedsteelframe.

Thechocksaresuitableformediumtohardroof.Whentheroofoverhangswellintothegobandrequiresinducedcaving,thechockscanprovideaccesstothegob.

SHIELD

Shields,anewentryintheearlyseventies,arecharacterizedbytheadditionofacavingshieldattherearendbetweenthebaseandthecanopy.Thecavingshields,whichingeneralareinclined,arehinge-jointedtothecanopyandthebasemakingtheshieldakinematicallystablesupport,amajoradvantageovertheframesandthechocks.Italsocompletelysealsoffthegobandpreventsrockdebrisfromgettingintothefacesideofthesupport.Thustheshield-supportedfaceisgenerallyclean.

Thehydrauliclegsintheshieldsaregenerallyinclinedtoprovidemoreopenspacefortraffic.Becausethecanopy,cavingshield,andbaseareinterconnected,itcanwellresistthehorizontalforcewithoutbendingthelegs.Thus,unlikethesolidconstraintintheframe/chocksupports,thepinconnectionsbetweenthelegsandthecanopy,andbetweenthelegsandthebaseinashieldsupportmakeitpossiblethattheangleofinclinationofthehydrauliclegsvarieswiththeminingheights.Sinceonlytheverticalcomponentofhydrauliclegpressureisavailableforsupportingtheroof,theactualloadingcapacityoftheshieldalsovarieswiththeminingheights.

Therearemanyvariationsoftheshieldsupports.Inthefollowing,sixitemsareusedtoclassifytheshields,whichenablesaunifiedterminologytobedevelopedforallkindsofshields.Thetypesofmotionaltracesofthecanopytip,legpositionsandorientation,numberoflegs,canopygeometry,andotheroptionaldesignsanddevicescanbeclearlyspecifiedbytheterminology.

TYPESOFMOTIONALTRACESFORTHELEADINGEDGEOFTHECANOPY.

Thisisthemostcommonlyrecognizedwayofclassifyingtheshield.Basedonthiscriterion,therearethreetypes,lemniscate,caliper,andellipse（Fig.8.11）.

A.Lemniscate.LB.Caliper.CC.Ellipse.E

Fig.8.11Threetypesofmotionaltracesforleadingedgeoftheshieldcanopy

A.Lemniscate.Thisisthemostpopulartype.Thecavingshieldandthebasearejointedbytwolemniscatebarswhichhaveatotaloffourhinges.Asthehydrauliclegsareraisedandlowered,thedimentionsofthelemniscatebarsareselectedsuchthattheleadingedgeofthecanopymovesupanddownnearlyvertically,thusmaintaininganearlyconstantunsupporteddistancebetweentheface-lineandtheleadingedgeofthecanopy.Thisisafeaturethatiswidelyconsideredmostdesirableforgoodroofcontrol.Thereareclearlimitsofminingheightwithinwhichtheleadingedgeofthecanopymovesnearlyvertically.Theselimitsarestrictlycontrolledbythedimentionalandpositionalarrangementsofthecanopy,cavingshield,lemniscatebars,andthebase.Beyondtheselimits,theedgeswillmoverapidlyawayfromtheface-linecreatingalargeunsupportedarea.

B.Caliper.Inacalipershield,thecavingshieldandthebaseareconnectedbyasinglehinge.Whenthehydrauliclegsareraised,theleadingedgeofthecanopymovesinanarcawayfromtheface,thusincreasingtheunsupportedareaThisisconsider