Patent ID: 8511595

Claim:
A refiner for refining fibrous material, the refiner comprising: at least one refining element forming a shell having a back side, a shell body and a front side, the front side defining a first refining surface comprising portions of the shell body which extend away from the shell body forming outwardly extending blade bars which terminate at the first refining surface, the blade bars defining blade grooves therebetween; wherein the refining element has portions forming a regular geometrically distributed pattern of a multiplicity of first openings passing though the shell body from the back side to the refiner surface so that at least most of the first openings cut through at least one blade bar, and substantially every blade bar is cut by said openings a plurality of times; at least one second refining surface which is arranged at least partly substantially opposite to the first refining surface to define a refining area, and a refiner chamber therebetween; wherein the first refining surface and the second refining surface are arranged to provide for movement between the first refining surface and the second refining surface; wherein the first refining surface defines a total refining area and wherein the first refining surface first openings are ones through which fibrous material to be refined is arranged to be fed into or removed from the refiner chamber of the refiner, the first openings defining a first opening area; and wherein a ratio is defined between the first opening area composed of said first openings and the total refining area of the first refining surface, which ratio is from 10% to 40%.