Grinding discs for defibering fibrous material

Claim 1

A grinding disc for defibering fibrous material in an interspace between two opposed relatively rotating discs comprising: a. a circular plate mounted for rotational movement; b. an opening located at the center of said plate for introducing the material into a central feeding section; c. a plurality of arcuate grinding segments having radially extending edges disposed peripherally about said plate and extending inwardly from the outer periphery of the segment to an inner periphery thereof which merges with said feeding section; d. said grinding segments having a grinding face comprising a plurality of spaced ribs with intervening material flow channels extending obliquely from the inner periphery to the outer periphery of the segments; and e. the outer and inner peripheries of said segments both having a radius of curvature which is shorter than the dimension of the spacing of said segment inner periphery from the center of said plate opening to cause the outer and inner peripheries of the adjoining segments to define scalloped peripheral edges forming a wave-shape about the disc circumference so that the two opposed relatively rotating discs subject fibrous material therebetween to radial forces which vary in frequency and magnitude in response to the wave-shape producing pulsating pressure variations resulting in improved defibration.