HOISTS10-15Table10/2/10TypicalDataforElectricChainHoists*Table10/2/11TypicalDataforElectricWireRopeHoists*SomeairhoistsalsoincludeaWeston-typeloadbrake/Thehoistmaybesuspendedbyahook/lug/ortrolley；thelattermaybeplain/geared/orair-motor-driven/Horizontalmovementislimitedtoabout25ft(7/6m)becauseoftheairhose/althougharunwaysystemisavailablewithaseriesofnormallyclosedportsthatareopenedbyaspecialtrolleytosupplyairtothehoist/Airhoistsprovideinfinitelyvariablespeed/accordingtothemovementofthecontrolvalve/Veryhighspeedsarepossiblewithlightloads/Whenseverelyoverloaded/theairmotorstallswithoutdamage/Airhoistsaresmallerandlighterthanelectrichoistsofequalcapacityandcanbeoperatedinexplosiveatmospheres/Theyaremoreexpensivethanelectrichoists/requiremufflersforreasonablyquietoperation/andnormallyarefittedwithautomaticlubricatorsintheairsupply/JacksJacksareportable/hand-operateddevicesformovingheavyloadsthroughshortdistances/Therearethreetypesincommonuse/screwjacks/rack-and-leverjacks/andhydraulicjacks/Bell-bottomscrewjacks(Fig/10/2/23)areavailableincapacitiesto24tonsandliftingrangesto14in/ThescrewisrotatedbyabarinsertedinholesinthescrewheadorByaratchetleverfittedtothehead/Gearedbridgejackswillliftupto50shorttons(45tonnes)/Aleverratchetmechanismturnsabevelpinion；aninternalthreadinthegearraisesthenonrotatingscrew/Rack-and-leverjacks(Fig/10/2/24)consistofacast-steelormalleable-ironhousinginwhichtheleverpivots/Theracktoothedbarpassesthroughthehollowhousing；theloadmaybeliftedeitheronthetoporonatoeextendingfromthebottomofthebar/Theleverpawlmaybebiasedeithertoraiseortolowerthebar/thehousingpawlholdingtheloadonthereturnleverstroke/Rack-and-leverjacksto20shorttons(18tonnes)aredirectacting/Leveroperatedgearedjacksrangeupto35shorttons(32tonnes)/Liftingheightsto18in(0/46m)areprovided/Trackjacksarerack-and-leverjackswhichmaybetrippedtoreleasetheload/Theyareusedforrailroad-trackworkbutnotforindustrialservicewherethetrippingfeaturesmightbehazardous/Hydraulicjacks(Fig/10/2/25)consistofacylinder/apiston/andalever-operatedpump/Capacitiesto100shorttons(91tonnes)andliftingheightsto22in(0/56m)areavailable/Jacks25shorttons(22/7tonnes)andlargermaybeprovidedwithtwopumps/thesecondpumpbeingahigh-speedunitforrapidtravelatpartialload/MINEHOISTSANDSKIPSbyBurtGarofabTherearetwotypesofhoists/thedrumhoistandthefrictionhoist/Onadrumhoist/theropeisattachedtothedrumandiswoundaroundandstoredonthedrum/Adrumhoistmaybesingle-drumordouble-drum/Therearealsoseveraldifferentconfigurationsofboththesingle-drumandthedouble-drumhoist/Adrumhoistmaybefurtherdividedaseitherunbalanced/partiallybalanced/orfullybalanced/Onafrictionhoist/whichisoftenreferredtoasaKoepehoist/theropeisnotwoundaroundthedrum/butratherpassesoverthedrum/Africtionhoistmayutilizeasingleropeormultipleropes/Theoperationofhoistsmaybecontrolledmanually/automatically/orsemiautomatically/Therearealsoarrangementsthatusecombinationsofthedifferentcontroltypes/Therearecurrentlythreetypesofgroovingbeingusedonnewdrumsfordrumhoists/Theyarehelicalgrooving/counterbalance(Lebus)grooving/andantisynchronousgrooving/Helicalgroovingisusedprimarilyforapplicationswhereonlyasinglelayerofropeiswoundaroundthedrum/Counterbalanceandantisynchronousgroovingareusedforapplicationswheremultiplelayersofropearewoundaroundthedrum/Minehoistsaregenerallydividedinto(1)Metal-minehoists(e/g//iron/copper/zinc/salt/gypsum/silver/gold/ores)and(2)coal-minehoists/Theseclassessubdivideintomainhoists(forhandlingoresorcoal)andhoistsformen/timbers/andsupplies/Theyaredesignedforoperating(1)mineshafts/verticalandinclined/balancedandunbalanced；and(2)slopes/balancedandunbalanced/Whenanemptycageorplatformdescendswhiletheloadedcageorplatformascends/aswhenbothcablesarewoundonasingledrum/themachineisreferredtoasabalancedhoist/Mostmedium-andlarge-sizedhoistsnormallyoperateinbalance/asthetonnageobtainedforagivenloadandropespeedisaboutdoublethatforanunbalancedhoistandthepowerconsumptionpertonhoistedislower/Balancedoperationcanalsobeobtainedbyacounterweight/Thecounterweight(approximatelyequaltoallthedeadloadsplusone-halftheliveload)isusuallyinstalledinguideswithinasingleshaftcompartment/Theaveragedepthoforeminesisabout2/000ft(610m)/andthatofcoalminesiscloseto500ft(152m)/Mostoreminehoistsareofthedouble-drumtype/normallyhostinginbalance/eachdrumbeingprovidedwithafrictionclutchforchangingtherelativepositionsofthetwoskipswhenoperatingfromvariouslevels/Hoistsforcoalminesareprincipallyofthekeyed-drumtype/foroperatinginbalancefromonelevel/Forhighropespeedsinshallowshafts/itisgenerallyadvantageoustousecombinedcylindricalandconicaldrums/Thecylindroconicaldrumplacesthemaximumropepull(weightofropeandloadedskip)onthesmalldiametersothatduringtheaccelerationperiodofthecycle/theweightoftheopposingskipisofferingthegreatestcounterbalancetorque/reducingmotorpeakloadsandslightlyreducingthepowerconsumption/Thepeakreductionobtainedbecomesgreaterwhen
免责声明：
1. 《外文翻译---电动平台型起重机的典型数据》内容来源于互联网，版权归原著者或相关公司所有。
2. 若《86561825文库网》收录的文本内容侵犯了您的权益或隐私，请立即通知我们删除。
