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中国矿业大学2008届本科生毕业设计第1页英文原文THESHEARERShearerLongwallequipmentconsistsofthreemajorcomponents:thehydraulicallypoweredroofsupport,thechainconveyor,andthecoal-cuttingmachine.Thetwodifferenttypesofcoal-cuttingequipmentusedincoalminesareshearersandplows.Plowsareusedinlowseams,42in.orless.Theunitconsistsofsteelconstructionequippedwithcarbon-tippedbits.Thispassivesteelunitisengagedtoaguidingsystemonthefaceconveyor.Anendlessroundlinkchainpoweredbysynchronizedelectricdrivesoneachendofthefaceconveyorpullstheplowbodyatspeedsbetween120and420ft/minalongtheface.Forthecuttingprocesstheplowhastobeforcedagainstthecoalface.Thisisdonebyhydrauliccylinderattachedtothegobsideofthefaceconveyorandtothebaseofthesupports,orbyaseparatehydraulicprop.Forcesofbetween1and3tonsareappliedpercylinder.Aplowdriveisattachedtoeachdriveframeofthefaceconveyor.Only30%to60%ofthedrivepowersuppliedtotheplowisusedforcuttingandloadingofcoal；theremainderislostinfriction.Thismeansthatthepowerlossisconsiderablyhigherthanthatofashearer,whichuses75%to85%ofitspowerfortheremovalofthecoal.Asaresult,ratherlargedrivesarerequiredatthefaceends.Althoughtherearemanymodels,theshearerhasseveralcommonbasiccomponents.Adouble-endedranging-drumshearer(Fig.8.1),forexample,consistsoffourmajorcomponents:electricmotors,gearheads,haulageunit(powerpack),andcuttingdrums.中国矿业大学2008届本科生毕业设计第2页Theelectricmotorrangingfrom300to1000horsepower(223750kW)isthepowersourcefortheshearer.Itprovidespowertorunthehydraulicpumpsinthehaulageunitandthegearheadsforthecuttingdrum.Thelarge-capacityshearersaregenerallyequippedwithtwoelectricmotors:oneforthehaulageunitandonegearheadandtheotherfortheothergearheadandotherancillaryequipment.Themotorscanberemotelycontrolled.Therearetwogearheads,oneontheleft-handtheotherontheright-handsideoftheshearer.Eachgearheradconsistsofagearheadgearboxandarangingarm.Thecuttingdrumislacedwithspiralvanesonwithspiralvanesonwhichthecuttingbitsaremounted.Itsdiameterrangesfrom34to72in.(0.861.83m)withrotationalspeedsfrom30to105rpm.Thetrendsaretowardfewerbutlargerbitsandslowerdrumspeedforbettercuttingefficiencyandlesscoaldustproduction.Thedrumsarealsoequippedwithpowercowlstoincreasethecoalloadingefficiency.Thepowercowlisusuallylocatedbehindthecuttingdrum.Forthatreason,itcanberotatedafull180º.Theelectricmotor,haulageunit,andgearheadboxescombinetoformtheshearersbodywhichismountedontheunderframe.Theunderframehasfourslidingshoes.Theface-sideshoesarefittedandrideontheface-sidetopguideofthefaceconveyorpan,andtheothertwogob-sideslidingshoesarefittedonaguidetubetopreventderailment.Thetrammingapedoftheshearerrangesfrom19to46ft/min(5.814.0m/min).Inaddition,theshearerisequippedwithauxiliaryhydraulicpumpsandcontrolvalvesforoperatingtherangingarmsandpowercowls,waterspraying中国矿业大学2008届本科生毕业设计第3页devices,cable,chainanchorageandtensioners,andsoonInselectingtheshearer,miningheightshouldfirstbeconsidered；thatis,thediameterofthecuttingdrum,bodyheight,lengthoftherangingarm,andswinganglemustbeproperlyselected.Forthedouble-endedranging-drumshearer,themaximumminingheightcannotexceedtwicethediameterofthecuttingdrum.Theminingheightcanbedeterminedby(Fig.8.3)H=Hb-B/2+Lsin+D/2WhereH=seamthicknessorminingheightHb=shearersbodyheightB=bodydepthL=lengthoftherangingarm=theanglebetweentherangingarmandthehorizontallinewhentherangingarmisraisedtoitsmaximumheightD=diameterofthecuttingdrumForexample,fortheEichhoffEDW-170Ldoubleranging-drumshearer,Hb=4.3ft,L=3.90ft,=52°，andD=5.3ft.ItsmaximumcuttingheightisH=9.2ft.TypesofmodernshearersSinceitsfirstappearancein1954,theshearerhasundergonecontinuouschangesbothincapabilityandstructure.Itisnowthemajorcuttingmachineinlongwallcoalfaces.Therearetwotypesofshearers,single-anddouble-drum.Intheearliermodels,thedruminthesingle-drumshearerismountedontheshearersbodyandcannotbeadjustedforheight.Thereforeitisnotsuitableforareaswherethereareconstantchangesinseamthicknessandfloorundulation.Thusthesingle-endedfixed-drumshearerisusedmostlyforthinseams.中国矿业大学2008届本科生毕业设计第4页Figure6.10showsasingle-drumshearerwitharangingarm.Thecuttingdrumismountedattheveryendoftherangingarm.Therangingarmcanberaisedupanddownbyhydrauliccontroltoaccommodatethechangingseamthicknessandfloorundulation.Butwhentheseamexceedsacertainthickness,thesingle-drumshearercannotcuttheentireseamheightinonecutandareturncuttingtripisnecessarytocompleteafullwebcut.Furthermore,sincethedrumislocatedontheheadentryside,itgenerallyrequiresanicheinthetailentryside.Anicheisaprecutfaceend,onewebdeepandashearerslengthlong.Withanicheatthefaceendtheshearercanturnaround.Nowadays,thedoubleranging-drumshearersareusedpredominantly.Theshearercutsthewholeseamheightinonetrip.Thetwodrumscanbepositionedtoanyrequiredheight(withinthedesignedrange)duringcuttingandloweredwellbelowthefloorlevel.Thearrangementofthedrumsenablesthewholeseamtobecutineitherdirectionoftravel,therebyensuringrapidfaceadvanceandshorteningroofexposuretime.Therearevarioustypesofdoubleranging-drumshearers.Basedonthelocationofthedrums,therearetwotypes:onewithonedrummountedoneachsideoftheshearersbodyandtheotherwithbothdrumsmountedononesideofthemachine.Theformertypeisthemostwidelyused.Itsadvantageisthatwithonedrumoneachsideoftheshearer,itcansumpineitherdirection.Duringthecuttingtrip,theleadingdrumcutstheupper70%oftheseamheightwhilethereardrumcutsthelower30%andcleansupthebrokencoalonthefloor.Thetwodrumsareapproximately2333ft(710m)apart.Whenthesheareristravelingintheoppositedirectiontothatofthefaceconveyor,thecoalcutbytheleadingdrumhastopassundertheshearersbody,whichincreasesthemovingresistanceoftheshearerandthefaceconveyorandcouldcausea“crowding”condition.Ifthebrokencoalistoolarge,itmayblocktheshearerandstoptheoperation.Ingeneral,whentheshearerandthefaceconveyoraretravelingintheoppositedirections,approximately70%ofthecoaltakenbytheleadingdrumwillpassundertheshearer.Butwhentheyaretravelinginthesamedirection,thecoaltakendownbythereardrumtogetherwiththefloatcoalfromthefloorconstitutetheapproximately30%ofthecoalthathastopassundertheshearer.Theformercaseconsumes25%morepowerthanthelatter.Ascomparedtothesingle-endedshearer,theunderframeofthedouble-endedshearerishigher,therebyensuringasufficientcrosssectionfor