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1、Chapter10PaperManufacture-WetEndOperationTheartoftruepapermakinghaditsorigininChinaaround100ADbasedonthediscoverythatadilutesuspensionoffibers(obtainedbymaceratingtheinnerbarkportionofbamboo)couldbeformedintoamatbyfilteringthesuspensionthroughafinescreen.Thematwasthenmadesuitableforwritinganddra
2、wingbypressing,dryingandsizing.Papercontinuedtobemadebyhanduptothebeginningofthe19thcentury.AFrenchman,LouisRobert,wasthefirsttopatentadesignforacontinuouspapermachinein1799.thefirstmachineevertobebuiltandsuccessfullyoperatedwasstartedupinEnglandin1803.TheFourdrinierbrotherstookoverdevelopmentri
3、ghts.ThemachineeventuallybecameknownastheFourdrinrermachine.Theearlypapermachinesconsistedofaheadboxaddingpaperstocktoamovingwiresupportedbetweentorolls.Thewetsheetwaspressedonceonthewireandthentakentoafeltandrunthroughanotherpressnipbeforebeingaccumulatedonarollforeventualdryinginsheetedform.10
4、.1INTRODUCTIONTOTHEPAPERMACHINESincethedaysofLouisRobert,thepapermachinehasundergonecontinualdevelopment,makingitpossibletoproduceawiderwebofpaperateverincreasingspeedandtomoreexactingstandardsofquality.Abasicfourdrinier-typemachineisillustratedinFigure10-1,andthefollowinggivesabrieffunctionalex
5、planationforeachmajorcorrmonent:Theflowspreadertakesintheincomingpipelinestockflowanddistributesitevenlyacrossthemachinefrombacktofront.Thepressurizedheadboxdischargesauniformjetofpapermakingstockontothemovingformingfabric.-Theendless,movingfourdrinierfabricformsthefibersintoacontinuousmattedweb
6、whilethefourdriniertabledrainsthewaterbysuctionforces.(onothertypesofpapermachines,thesheetmaybeformedbyothermeans,e.g.betweentwofabrics,oronafabric-coveredcylinder.)-Thesheetisconveyedthroughaseriesofrollpresseswhereadditionalwaterisremovedandthewebstructureisconsolidate(i.e.,thefibersareforced
7、intointimatecontact).-Mostoftheremainingwaterisevaporatedandfiber-to-fiberbondsaredeveloperasthepapercontactsaseriesofsteam-heatedcylindersinthedryersection.-Thesheetiscalenderedthroughaseriesofrollnipstoreducethicknessandsm
