US Patent 7712694 Disc refiner with plates having logarithmic spiral bars

A special shape of bars on refining discs or plate segments of a rotating disc refiner is disclosed including a plurality of bars generally extending outwards towards the outer end of the disk across its surface, arranged in a single, two or more radial zones, the plurality of the bars within a zone being curved with the shape of a logarithmic spiral. Disc refiners including such refining discs are also disclosed.