机械零件齿轮中英文对照外文翻译文献.docx

机械零件齿轮中英文对照外文翻译文献.docx

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机械零件齿轮中英文对照外文翻译文献

（文档含英文原文和中文翻译）

中英文资料对照外文翻译

MachineParts（I）

Gears

Gearsaredirectcontactbodies,operatinginpairs,thattransmitmotionandforcefromonerotatingshafttoanotherorfromashafttoaslide（rack）,bymeansofsuccessivelyengagingprojectionscalledteeth.

Toothprofiles.Thecontactingsurfacesofgearteethmustbealignedinsuchawaythatthedriveispositive;i.e.,theloadtransmittedmustnotdependonfrictionalcontact.Asshowninthetreatmentofdirectcontactbodies,thisrequiresthatthecommonnormaltothesurfacesnottopassthroughthepivotalaxisofeitherthedriverorthefollower.

Asitisknownasdirectcontactbodies,cycloidalandinvoluteprofilesprofilesprovidebothapositivedriveandauniformvelocityratio;i.e.,conjugateaction.

Basicrelations.Thesmallerofagearpairiscalledthepinionandthelargeristhegear.Whenthepinionisonthedrivingshaftthepairiscalledthepinionandthelargeristhegear.Whenthepinionisonthedrivingshaftthepairactsasaspeedreducer;Whenthegeardrives,thepairisaspeedincrreaser.Gearsaremorefrequentlyusedtoreducespeedthantoincreaseit.

IfagearhavingNteethrotatesatnrevolutionsperminute,theproductN*nhasthedimension“teethperminute”.Thisproductmustbethesameforbothmembersofamatingpairifeachtoothacquiresapartnerfromthematinggearasitpassesthroughtheregionoftoothengagement.

Forconjugategearsofalltypes,thegearratioandthespeedratioarebothgivenbytheratioofthenumberofteethonthegeartothenumberofteethonthepinion.Ifagearhas100teethandamatingpinionhas20,theratiois100/20=5.Thusthepinionrotatesfivetimesasfastasthegear,regardlessofthegear.Theirpointoftangencyiscalledthepitchpoint,andsinceitliesonthelineofcenters,itistheonlypointatwhichtheprofileshavepurerolingcontact.Gearsonnonparallel,non-intersectingshaftsalsohavepitchcircles,buttherolling-pitch–circleconceptisnotvalid.

Geartypesaredeterminedlargelybythedispositionoftheshafts;inaddition,certaintypesarebettersuitedthanothersforlargespeedchanges.Thismeansthatifaspecificdispositionoftheshaftsisrequired,thetypeofgearwillmoreorlessbefixed.Ontheotherhand,ifarequiredspeedchangedemandsacertaintype,theshaftpositionswillalsobefixed.

Spurgearsandhelicalgears.Agearhavingtoothelementsthatarestraightandparalleltoitsaxisisknownasaspurgear.Aspurpaircanbeusedtoconnectparallelshaftsonly.

Ifaninvolutespurpinionweremadeofrubberandtwisteduniformlysothattheendsrotatedabouttheaxisrelativetooneanother,theelementsoftheteeth,initiallystraightandparalleltotheaxis,wouldbecomehelices.Thepinionthenineffectwouldbecomeahelicalgear.

Wormandbevelgears.Inordertoachievelinecontactandimprovetheloadcarryingcapacityofthecrossedaxishelicalgears,thegearcanbemadetocurvepartiallyaroundthepinion,insomewhatthesamewaythatanutenvelopsascrew.Theresultwouldbeacylindricalwormandgear.Wormsarealsomadeintheshapeofanhourglass,insteadofcylindrical,sothattheypartiallyenvelopthegear.Thisresultsinafurtherincreaseinload-carryingcapacity.

Wormgearsprovidethesimplestmeansofobtaininglargeratiosinasinglepair.Theyareusuallylessefficientthanparallel-shaftgears,however,becauseofanadditionalslidingmovementalongtheteeth.

V-belt

TherayonandrubberV-beltarewidelyusedforpowertransmission.Suchbeltsaremadeintwoseries:

thestandardV-beltandthehighcapacityV-belt.Thebeltscanbeusedwithshortcenterdistancesandaremadeendlesssothatdifficultywithsplicingdevicesisavoided.

First,costislow,andpoweroutputmaybeincreasedbyoperatingseveralbeltssidebyside.Allbeltsinthedriveshouldstretchatthesamerateinordertokeeptheloadequallydividedamongthem.Whenoneofthebeltsbreaks,thegroupmustusuallybereplaced.Thedrivemaybeinclinedatanyanglewithtightsideeithertoporbottom.Sincebeltscanoperateonrelativelysmallpulleys,largereductionsofspeedinasingledrivearepossible.

Second，theincludedangleforthebeltgrooveisusuallyfrom34°to38°.Thewedgingactionofthebeltinthegroovegivesalargeincreaseinthetractiveforcedevelopedbythebelt.

Third，pulleymaybemadeofcastiron,sheetsteel,ordie-castmetal.Sufficientclearancemustbeprovidedatthebottomofthegroovetopreventthebeltfrombottomingasitbecomesnarrowerfromwear.Sometimesthelargerpulleyisnotgroovedwhenitispossibletodeveloptherequiredtractiveforcebyrunningontheinnersurfaceofthebelt.Thecostofcuttingthegroovesistherebyeliminated.Pulleysareonthemarketthatpermitanadjustmentinthewidthofthegroove.Theeffectivepitchdiameterofthepulleyisthusvaried,andmoderatechangesinthespeedratiocanbesecured.

ChainDrives

Thefirstchain-drivenor“safety”bicycleappearedin1874,andchainswereusedfordrivingtherearwheelsonearlyautomobiles.Today,astheresultofmoderndesignandproductionmethods,chaindrivesthataremuchsuperiortotheirprototypesareavailable,andthesehavecontributedgreatlytothedevelopmentofefficientagriculturalmachinery,well-drillingequipment,andminingandconstructionmachinery.Sinceabout1930chaindriveshavebecomeincreasinglypopular,especiallyforpowersaws,motorcycle,andescalatorsetc.

Thereareatleastsixtypesofpower-transmissionchains;threeofthesewillbecoveredinthisarticle,namelytherollerchain,theinvertedtooth,orsilentchain,andthebeadchain.Theessentialelementsinaroller-chaindriveareachainwithsideplates,pins,bushings（sleeves）,androllers,andtwoormoresprocketwheelswithteeththatlooklikegearteeth.Rollerchainsareassembledfrompinlinksandrollerlinks.Apinlinkconsistsoftwosideplatesconnectedbytwopinsinsertedintoholesinthesideplates.Thepinsfittightlyintotheholes,formingwhatisknownasapressfit.Arollerlinkconsistsoftwosideplatesconnectedbytwopress-fittedbushings,onwhichtwohardenedsteelrollersarefreetorotate.Whenassembled,thepinsareafreefitinthebushingsandrotateslightly,relativetothebushingswhenthechaingoesonandleavesasprocket.

Standardrollerchainsareavailableinsinglestrandsorinmultiplestrands,Inthelattertype,twoormorechainsarejoinedbycommonpinsthatkeeptherollersintheseparatestrandsinproperalignment.Thespeedratioforasingledriveshouldbelimitedtoabout10∶1;thepreferredshaftcenterdistanceisfrom30to35timesthedistancebetweentherollersandchainspeedsgreaterthanabout2500feet（800meters）perminutearenotrecommended.Whereseveralparallelshaftsaretobedrivenwithoutslipfromasingleshaft,rollerchainsareparticularlywellsuited.

Aninvertedtooth,orsilentchainisessentiallyanassemblageofgearracks,eachwithtwoteeth,pivotallyconnectedtoformaclosedchainwiththeteethontheinside,andmeshingwithconjugateteethonthesprocketwheels.Thelinksarepin-connectedflatsteelplatesusuallyhavingstraight-sidedteethwithanincludedangleof60degrees.Asmanylinksarenecessarytotransmitthepowerandareconnectedsidebyside.Comparedwithroller-chaindrives,silent-chaindrivesarequieter,operatesuccessfullyathigherspeeds,andcantransmitmoreloadforthesamewidth.Someautomobileshavesilent-chaincamshaftdrives.

Beadchainsprovideaninexpensiveandversatilemeansforconnectingparallelornonparallelshaftswhenthespeedandpowertransmittedarelow.Thesprocketwheelscontainhemisphericalorconicalrecessesintowhichthebeadsfit.Thechainslooklikekeychainsandareavailableinplaincarbonandstainlesssteelandalsointheformofsolidplasticbeadsmoldedonacord.Beadchainsareusedoncomputers,airconditioners,televisiontuners,andVenetianblinds.Thesprocketsmaybesteel,die-castzincoraluminum,ormoldednylon.

MachineParts（II）

Fastener

Fastenersaredeviceswhichpermitoneparttobejoinedtoasecondpartand,hence,theyareinvolvedinalmostalldesigns.

Therearethreemainclassificationsoffasteners,whicharedescribedasfollows：

（1）Removable.Thistypepermitsthepartstobereadilydisconnectedwithoutdamagingthefastener.Anexampleistheordinarynut-and-boltfastener.

（2）Semipermanent.Forthistype,thepartscanbedisconnected,butsomedamageusuallyoccurstothefastener.Onesuchexampleisacotterpin.

（3）Permanent.Whenthistypeoffastenerisused,itisintendedthatthepartswillneverbedisassembled.Examplesarerivetedjointsandweldedjoints.

Theimportanceoffastenerscanberealizedwhenreferringtoanycomplexproduct.Inthecaseoftheautomobile,thereareliterallythousandsofpartswhicharefastenedtogethertoproducethetotalproduct.Thefailureorlooseningofasinglefastenercouldresultinasimplenuisancesuchasadoorrattleorinaserioussituationsuchasawheelcomingoff.Suchpossibilitiesmustbetakenintoaccountintheselectionofthetypeoffastenerforthespecificapplication.

Nuts,bolts,andscrewsareundoubtedlythemostcommonmeansofjoiningmaterials.Sincetheyaresowidelyused,itisessentialthatthesefastenersattainmaximumeffectivenessatthelowestpossiblecost.Boltsare,inreality,carefullyengineeredproductswithapracticallyinfiniteuseoverawiderangeofservices.

Anordinarynutloosenswhent