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时间:2020-04-24
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1、附录一:外文资料原文ELEMENTSOFCAMDESIGNHowtoplanandproducesimplebutefficientcamsforpetrolenginesandothermechanismsCamsareamongthemostversatilemechanismsavailable.Acamisasimpletwo-memberdevice.Theinputmemberisthecamitself,whiletheoutputmemberiscalledthefollower.Throughtheuseofcams,a
2、simpleinputmotioncanbemodifiedintoalmostanyconceivableoutputmotionthatisdesired.Someofthecommonapplicationsofcamsare——Camshaftanddistributorshaftofautomotiveengine——Productionmachinetools——Automaticrecordplayers——Printingmachines——Automaticwashingmachines——Automaticdishwa
3、shersThecontourofhigh-speedcams(camspeedinexcessof1000rpm)mustbedeterminedmathematically.However,thevastmajorityofcamsoperateatlowspeeds(lessthan500rpm)ormedium-speedcamscanbedeterminedgraphicallyusingalarge-scalelayout.Ingeneral,thegreaterthecamspeedandoutputload,thegrea
4、termustbetheprecisionwithwhichthecamcontourismachined.Camsinsomeformorotherareessentialtotheoperationofmanykindsofmechanicaldevices.Theirbest-knownapplicationisinthevalve-operatinggearofinternalcombustionengines,buttheyplayanequallyimportantpartinindustrialmachinery,fromp
5、rintingpressestoreapingmachines.Ingeneral,acamcanbedefinedasaprojectiononthefaceofadiscorthesurfaceofacylinderforthepurposeofproducingintermittentreciprocatingmotionofacontactingmemberorfollower.Mostcamsoperatebyrotarymotion,butthisisnotanessentialconditionandinspecialcas
6、esthemotionmaybesemi-rotary,oscillatoryorswinging.Evenstraight-linemotionoftheoperatingmemberispossible,thoughthetermcammaynotbeconsideredproperlyapplicableinsuchcircumstances.Mosttextbooksonmechanicsgivesomeinformationonthedesignofcamsandshowexamplesofcamformsplottedtopr
7、oducevariousordersofmotion.Whereneithertheoperatingspeednorthemechanicaldutyisveryhigh,thereisagooddealoflatitudeinthenermissibledesignofthecamanditisonlynecessarytoavoidexcessivelysteepcontoursorabruptchangeswhichwouldresultinnoise,impactshock,andsidepressureonthefollowe
8、r.But,withincreaseofeitherspeedorload,muchmoreexactingdemandsaremadeonthecam,callingforthemostca
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