Classifier with rifflers and variable throat

Claim 1

A classifier for separating heavier and lighter fractions in a liquid-borne stream of mixed particles of different densities, said classifier comprising, a hollow cylindrical body having a wall defining an annular internal chamber, a bowl at a lower end of said chamber, said bowl curving downwardly and inwardly from the wall of said body to a conical central opening, an inlet pipe leading to a substantially tangential inlet opening through said wall into said chamber adjacent an upper end of the chamber, a top cover for said chamber, an overflow pipe projecting downwardly through said cover and axially into said chamber toward said conical opening, said overflow pipe having an open lower end positioned above said conical opening and below said inlet opening, and a plurality of rifflers mounted to said wall at angularly spaced positions around said chamber below said inlet opening and above said bowl, each said riffler being a projection on said wall extending into said chamber and having a generally semicircular cross-sectional shape with gradually inclined leading and trailing surfaces thereon, each riffler extending angularly with respect to the direction of fluid flow over said wall between said inlet opening and said central opening, the dimension of said rifflers in the direction across the radius of said chamber being no greater than about one-third the diameter of the largest particles to be separated, said rifflers in use of said classifier jigging liquid-borne material passing over them and thereby releasing lighter particles entrapped by heavier particles so that such lighter particles move inwardly with respect to the heavier particles while said heavier particles continue to move over said wall.