Patent ID: 7458533

Claim:
A method for refining material between opposing discs in a refiner comprising: feeding the material to an inlet of at least one of the discs; rotating one disc with respect to the other disc while the material moves radially outward between the discs; intermeshing rows of teeth on the rotating disc with rows of teeth on the other disc, wherein each tooth on the rows of teeth has a front surface facing radially inward and oriented transverse to a radial extending through the tooth and a sidewall oriented substantially perpendicular to the front surface and facing towards a direction of rotation of the rotating one disc, wherein the front surface and sidewall intersect along a leading edge of the tooth; subjecting the material to impacts from teeth in a first row of said rows of teeth, where at least one tooth in the first row has a first row feed angle formed by the leading edge of the tooth in the first row; subjecting the material to impacts from the teeth in a second row of said rows of teeth, wherein the second row is radially outward of the first row and at least one tooth in the second row has a second row feed angle formed by the leading edge of the tooth in the second row, and the second row feed angle is at least 5 degrees and differs from the first row feed angle by at least 20 degrees and no more than 90 degrees, and the second row of teeth is one of an outer four rows of teeth on the disc, and subjecting the material to impacts from teeth in a third row of said rows of teeth, which is intermediate to the first row and second row, and at least one tooth in the third row has a third row feed angle formed by the leading edge of the at least one tooth in the third rows, wherein the third row feeding angle differs from the first row and second row feed angles.