Filter belt with means forming therewith plural pressure filter chambers

Claim 1

Apparatus for filtration of raw liquid comprising at least two filter frames and at least three filter plates, said filter frames and filter plates each having central cavities and each being alternately superimposed on one another, each of said filter frames being provided at its one side with a raw liquid supply opening, each of said filter plates having a filtrate discharge passage and each having a partition member extending across the respective cavity, each of said partition members having a filtration passage opening communicatory with said filtrate discharge passage, and endless filter cloth interposed between each contiguous filter frame and filter plate, guide rollers over which said endless filter cloth is disposed to define a serpentine path of travel for said endless filter cloth in which upper and lower cloth portions are interposed between each contiguous filter frame and filter plate to extend across said cavities, whereby a plurality of filtration chambers are superimposed one over the other between said raw liquid supply openings and said filtrate discharge passages with each filtration chamber being defined by an upper and a lower cloth portion, means for supplying raw liquid under pressure through said supply openings into said filtration chambers, said upper and lower cloth portions being disposed between two partition members of two opposed filter plates, and expandable means located between said lower portion of said filter cloth and the adjacent partition member for reducing the volume of said filtration chamber to compress the filtered material in the form of cakes and deposit the latter on the upper surface of said lower cloth portion, means conducting the filtrate from the upper and lower cloth portions along separate upper and lower paths respectively for discharge through said filtrate discharge passages, means for supplying pressure fluid into said expandable means to expand the latter, means for controlling the liquid in the filtration chambers from backflowing into said supply openings when said expandable means and expanded, means for moving said filter cloth along its serpentine path, and cake scraper means located on one side of said filtration chambers for removing said cakes from the same side of said filtration chambers as said cakes travel in the same direction in being discharged from their respective lower filter cloth portions.