Rotatable filter disc assembly

Claim 1

In a rotatable filter assembly for separation of fibers from a fiber suspension and including in combination, a plurality of annular filter discs each comprising a plurality of filter elements, a horizontal drum, means for rotating said drum about an axis, said filter discs being mounted on said drum in substantially parallel, axially spaced relation to each other, a container for said fiber suspension in which said drum is rotatable, each filter element being a hollow chamber having walls of filter cloth and radially inner and outer ends, means for each of said chambers defining a filtrate outlet at the radially inner end of each of said chambers, said drum being generally cylindrical and including a series of discharge tubes extending in an axial direction, said tubes forming a grating-like mantle wall of the drum, each hollow chamber communicating through its filtrate outlet with a discharge tube, and a collecting hopper extending into the drum through an open end thereof and surrounded by said filter discs, said hopper having an upwardly facing entrance opening extending along all of said filter discs, the interior of each filter element being subjected to a lower pressure than that outside said element during part of the drum's revolution, the improvement in which said discharge tubes, as seen in a cross-sectional view transverse to said axis, are arranged in a plurality of groups each including at least two tubes, the spacing between adjacent tubes in each group being substantially less than the spacing between adjacent groups.