A filter characterized in that a plurality of screen plates each having a penetration hole at its central portion are disposed inside of a filter box in a stacked form with a distance between each other in such a manner that the penetration holes are aligned up-and down-wards. The raw liquid to be filtered is fed through said penetration holes and the filtrate is collected at plurality of portions disposed at a nearly equal intervals in the peripheral part of said screen plates.
A filter (10) comprises a stack of flat rectangular filtrate-collecting chambers (12) defined by sheets (26) of stainless steel filter medium, and connected via respective thyristors (54, 58) to a power supply (50). Anode plates (14) are arranged between adjacent chambers (12). At intervals a current (of for example 1000A) is supplied to each chamber (12) in turn such that it is a cathode, for a short time sufficient to remove any fouling.
A filter device exhibits a chamber with a spiral which revolves helicoidally about the chamber axis. The spiral is constituted by a channel-shaped support which holds taut a filter constituted by a spiral-shaped tube. During the filtration of a suspension the liquid component of the suspension passes through the filter into the channel-shaped support and from the latter to a filtrate outlet. Because at least that part of the filter effective for the filtration forms a substantially smooth fold-free surface, uniform utilization of the total effective surface of the filter is possible. The solid residue deposited upon the surface of the filter can also be transported out of the chamber without difficulty by rotating the spiral.
