Patent ID: 7931779

Claim:
A screening apparatus for screening pulp suspensions, comprising a housing ( 2 ; 64 ), a tubular screen basket ( 8 ; 70 ) dividing the interior of the housing into a central chamber ( 10 ) and an outer substantially annular chamber ( 14 ), an inlet member ( 4 ) for supplying a suspension to be screened into either the central chamber or the outer chamber, an accept outlet member ( 16 ) for discharging a developed accept fraction of the suspension that has passed through the screen basket, a reject outlet member ( 20 ) for discharging a developed reject fraction of the suspension, a rotor ( 26 ) arranged in the housing for providing pressure and suction pulses in the suspension to be screened along the screen basket, a dilution liquid header ( 28 ) in the housing for supplying dilution liquid to counteract thickening of the suspension during operation, the header forming a tubular channel ( 46 ) dividing the basket into at least two parts ( 40 , 42 ) and extending at least substantially around the screen basket, and at least one dilution liquid supply conduit ( 51 ; 66 , 68 ) for supplying dilution liquid from outside the housing to the channel of the header, the header being provided with a plurality of ejection nozzles ( 50 ) for ejecting dilution liquid from the tubular channel, characterized in that each ejection nozzle forms a channel ( 58 ) including at least two channel sections, an entrance channel section ( 60 ) that opens into the channel ( 46 ) of the header and an exit channel section ( 62 ) downstream of the entrance channel section, the entrance channel section being substantially wider than the exit channel section.