机械工程专业英语 李光布

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1、Keys，CouplingsandSealsAkeyisthemachinerycomponentplacedattheinterfacebetweenashaftandthehubofapower—transmittingelementforthepurposeoftransmittingtorque(seeFigure1．6(a))．Thekeyisdemountabletofacilitateassemblyanddisassemblyoftheshaftsystem．Itisinstalledinanaxialgroovemachinedintotheshaft，calledak

2、eyseat．Asimilargrooveinthehubofthepower—transmittingelementisusuallycalledakeyway，butitismoreproperlyalsoakeyseat．Thekeyistypicallyinstalledintotheshaftkeyseatfirst；thenthehubkeyseatisalignedwiththekey，andthehubisS1．dintoposition．Figure1．6Parallelkeys1．SquareandRectangularParallelKeysThemostcommo

3、ntypeofkeyforshaftsuDto6．5inchesindiameteristhesquarekey，asillustratedinFigure1．6(b)．Therectangularkey(illustratedinFigure1．6(c))isrecommendedforlargershaftsandisusedforsmallershaftswheretheshorterheightcanbetolerated．Boththesquareandtherectangularkeysarereferredtoasparallelkeysbecausethetop，bott

4、omandthesidesofthekeyareparallel．Thekeyseatsintheshaftandthehubaredesignedsothatexactlyone—halfoftheheightofthekeyisbearingonthesideoftheshaftkeyseatandtheotherhalfonthesideofthehubkeyseat．2．CouplingsThetermcouplingreferstoadeviceusedtoconnecttwoshaftstogetherattheirendsforthepurposeoftransmittin

5、gpower．Therearetwogeneraltypesofcouplings：rigidandflexible．1)RigidCouplingsRigidcouplingsaredesignedtodrawtwoshaftstogethertightlysothatnorelativemotioncanoccurbetweenthem．Thisdesignisdesirableforcertainkindsofequipmentinwhichprecisealignmentoftwoshaftsisrequiredandcanbeprovided．Insuchcases，theco

6、uplingmustbedesionedtobecaoableoflransmittinathe．tnrn=Ipinthpthoft。AtypicalrigidcouplingisshowninFigure1．7，inwhichflangesaremountedontheendsofeachshaftandaredrawntogetherbyaseriesofbolts．Theloadpathisthenfromthedrivingshafttoitsflange，throughthebolts，intothematingflange，andouttothedrivenshaft．The

7、torqueplacestheboltsinshear．Thetotalshearforceontheboltsdependsontheradiusoftheboltcircleandthetorque．Rigidcouplingsshouldbeusedonlywhenthealignmentofthetwoshaftscanbemaintainedveryaccurately，notonlyatthetimeofinstaIIa