Abstract: A rotatable wood chip thickness classifying device. The apparatus includes two coaxial, spaced sets of apertured discs, each set defining a drum. The interdisc spacing of each drum is uniform, each drum having a different interdisc spacing from the other drum. For each set of discs, the inside diameter of adjacent discs alternates. Wood chips are fed into the interior of the first drum, this drum having a typical disc interspacing of 2 mm. The common axis of drum rotation is slightly tilted to the horizontal and chips of less than 2 mm fall through the interdisc openings of the first drum. The remainder of the chips pass to the interior of the second drum, typically of 8 mm interdisc spacing. Chips less than 8 mm fall through the interdisc openings of the second drum. The alternation of inside disc diameters, for each drum, yields a chip tumbling effect to thereby inhibit an elongated chip, of a diameter of less than 2 mm for example, from straddling the 2 mm openings and not falling therethrough.

Abstract: A disc screen wood chip sorter of the type having a series of corotating shafts, each of which is provided with an axially spaced series of concentric discs. The peripheries of the discs carried by one shaft interdigitate with those of the next adjacent shafts. The discs on any one shaft are maintained in parallelism by spacer elements in the general form of short cylindrical washers. The specific improvement of this invention relates to a novel configuration of these spacing elements. Each spacer end is provided with a flange to thereby define a central, annular groove or recess between the flanges, each annular receiving recess receiving a portion of the periphery of an adjacent disc, i.e., a disc mounted on a neighboring shaft. By virtue of this novel form of disc spacer, the disc screen sorter severely inhibits the passage of wood chips of a thickness greater than intended, i.e., chips of a thickness greater than the spacing between interdigitated discs.