Device for separating coarse and fine particles from ultrafines

An improvement in a machine for separating coarse and fine particles as gravel and/or sand from a sludge containing ultrafine substances, as laitance, the machine comprising a rotatably mounted drum provided with a pair of axially opposite openings, one said opening forming a discharge opening for said coarse and fine particles and the other said opening forming a discharge opening for the sludge, means to flow said sludge towards said other opening, feeding means being provided for feeding a mass containing components to be separated, said feeding means extending through said other of said pair of openings into the drum, a water feeding pipe extending through said one of said pair of openings into the drum, a sludge water mixture within said drum, a helical web provided at the inside of a peripheral wall of the drum, and a plurality of buckets fastened at said peripheral wall between said one opening and the helical web, said helical web being constructed and arranged to move said coarse and fine particles towards said buckets each of the said buckets being provided with a bottom wall and a pair of side walls and draining means in said bottom wall, and a discharge chute extending through said other one of said pair of openings;

• the improvement comprising:
• draining means provided in each one of said pair of side walls of each said bucket, the draining means of the bottom wall of the buckets comprising a plurality of longitudinal slots having a width in the range of 10 to 30 mm and extending substantially parallel with one another and with the drum axis;
• the slots running substantially over the whole axial width of the bottom wall, each slot being overlapped by a guide plate which in a horizontal position of the bottom wall of the bucket forms an inclined ramp the radial inward edge of which is spaced above the bottom wall, the draining means of each one of said pair of side walls comprising a plurality of slots extending downwardly with the bottom wall in a horizontal position and ending at a small distance above the bottom wall, said plurality of slots being overlapped by guide plates respectively at the inside of each side wall, the said side wall guide plates forming inclined ramps with respect to the side walls, and the radial inward edge of each side wall guide plate in a horizontal position of the bottom wall extending upwards and being spaced from the side wall.