Device for filtering of solids / liquid - mixtures, in particular sludges and suspensions, or to clean piece strength solid materials by washing and / or separation of solid piece strength, in particular granular and / or fibrous materials made of moist materials, in particular pasty or. pastenfoermigen materials by washing out, or for the classifying of solid granular and / or piece strength materials according to the grain size and / or detached of solid, in particular contaminating, constituents of such materials