D21DTREATMENT OF THE MATERIALS BEFORE PASSING TO THE PAPER-MAKING MACHINEIn this subclass non-limiting references (in the sense of paragraph 39 of the Guide to the IPC) may still be displayed in the scheme. D21D1/00 D21D1/00Methods of beating or refiningBeaters of the Hollander type knotter screens D21F D21D1/002Control devices D21D1/004Methods of beating or refining including disperging or deflaking D21D1/006Disc mills D21D1/008Discs D21D1/02Methods of beatingBeaters of the Hollander type D21D1/04Beater rolls or bars D21D1/06Bed plates D21D1/08Beaters with means for driving the pulp quickly D21D1/10Beaters with means for regulating the pressure between the beater roll and the bed plate D21D1/12Beaters with means for continuous pulp discharge D21D1/14Beaters with one beater roll and with vertical stuff circulation canal D21D1/16Beaters with means for returning the pulp over the head of the beater roll D21D1/18Beaters with two or more beater rolls D21D1/20Methods of refining D21D1/22Jordans D21D1/24Jordan rolls D21D1/26Jordan bed plates D21D1/28Ball or rod mills D21D1/30Disc mills D21D1/303Double disc mills D21D1/306Discs D21D1/32Hammer mills D21D1/34Other mills or refiners D21D1/36with vertical shaft D21D1/38with horizontal shaft D21D1/40Washing the fibres D21D5/00Purification of the pulp suspension by mechanical meansApparatus therefor centrifuges, cyclones B04 D21D5/005Forming fibrous aggregates D21D5/02Straining or screening the pulp D21D5/023Stationary screen-drums D21D5/026with rotating cleaning foils D21D5/04Flat screens D21D5/043Vibrating screens D21D5/046Rotary screens D21D5/06Rotary screen-drums D21D5/08combined with a rocking movement D21D5/10of the tank D21D5/12of the screen D21D5/14of the tank and the screen D21D5/16Cylinders and plates for screens D21D5/18with the aid of centrifugal force D21D5/20in apparatus with a horizontal axis D21D5/22in apparatus with a vertical axis D21D5/24in cyclones D21D5/26De-aeration of paper stock D21D5/28Tanks for storing or agitating pulp D21D99/00Subject matter not provided for in other groups of this subclass