>> P.49
1N=0.102kgf=0.2248lbs.1mm=0.03937inchABCDEFGHIJKLMentryofharmfulforeignsubstances,suchasdirt,dustandwater.Forthisreason,sealingdevicesmustalwaysworkeffectivelytosealandpreventagainstdustpenetrationunderalloperatingconditions.Also,whenselectingasuitablesealingmethod,itisneces-sarytoconsidersuchfactorsasthetypeoflubricant,peripheralspeedoftheseal,operatingtemperature,shafteccentricity,sealfriction,etc.aswellaseaseofassemblyanddisassembly.Sealingmethodsareofthenon-contactandcontacttypes,anditisnecessarytoselecttheappropriatetypedependingontheapplication.Non-contacttypesealingmethodtheuseofoilgrooves,Therearemanymethodsofnon-contacttypesealing,includingflingersandlabyrinths,whichutilizethecentrifugalforceandnar-rowgaps.Sincetheydonotmakedirectcontactwiththeshaftorhousing,itisunnecessarytoconsiderfrictionandwear,andthenon-contactsealingmethodissuitableforhighspeedrotationandhighoperatingtempera-tures.However,becauseofgaps,thismethodisnotalwayssufficientinpreventingoilleakageanddustentrywhenthemachineisnotinoperation.1OilgrooveOilgroovesareprovidedoneithertheshaftorhousingbore,oronbothformoreeffectivesealing(SeeFig.14.).Theclearancebetweentheshaftandthehous-ingboreshouldbeassmallaspossible,andtheval-uesshowninTable30aregenerallyused,takingintoconsiderationerrorsinmachiningandassembly,shaftdeformation,etc.Threeormoregroovesaremadewithawidthof3〜5mmandadepthof4〜5mm.Ifthegroovesarefilledwithgrease,itwillbemoreeffec-tivefordustprevention.AsshowninFig.15,helicalgroovesaresuitableforhorizontalshaftswhichhaveafixeddirectionofrota-tion.Rightorlefthandedgroovesareusedaccordingtothedirectionofrotation,andtheyareusedforoillubricationnormallyinconjunctionwithasuitableanti-dustdevice.Table28Largestpermissiblesinglecornerradiusofshaftsandhousings rasmaxunit:mm HousingrsminrasmaxrsminrsminrasmaxShaftrsmin0.10.150.20.30.40.65111..52222340.10.150.20.30.40.61.511.1.12.522345rsminSmallestpermissiblesinglechamferdimensionrasmaxLargestpermissiblesinglecornerradiusofshaftsandhousingsTable29Filletreliefdimensionsforgroundshaftsunit:mm andhousings hsgrtrsminbFilletreliefdimensionsb22.43.2444.75.97.48.610rgs.31.51.52.52234567t0.20.30.40.50.50.50.50.60.60.6rsminSmallestpermissiblesinglechamferdimension1.511.1.12234567.5SealingToobtainthebestperformanceofrollingbearings,ittheisnecessarylubricantandtopreventleakageof(1)(2)Fig.14(3)A46
| < 
| 
> | 
>>
