Patent ID: 7407123
Filing Date: 2008-08-05
Classification: B02C,D21D

Abstract:
1. A refining disc having a working surface, a radially inner end and a radially outer end, the working surface including a plurality of bars having inner and outer ends, laterally spaced by intervening grooves, and extending generally outwardly toward said outer end across said surface, said bars and grooves forming a pattern defining at least one radially extending substantially annular zone and wherein each of at least a majority of said plurality of bars in said zone being curved with the shape of a logarithmic spiral from the inner to the outer end of said bars, wherein said shape of said bars conforms within manufacturing tolerances to the mathematical expression in polar coordinates: where “r” is the radial position along the centerline of the bar, “a” is a scale parameter for r and α is the intersecting angle between any tangent to the curve and the generatrix of the coordinate system.