Abstract: An apparatus for sorting wood chips or other particulate material into groups according to size. The apparatus includes a housing having an opened top, a first screen attached to the housing substantially covering the opened top thereof, a second screen attached to the housing beneath the first screen, and a hopper fixedly attached to the housing for holding a quantity of wood chips and for depositing wood chips onto substantially the center of the first screen. The first and second screens slope downwardly from the centers thereof so that any wood chips of a size too large to pass therethrough will pass, aided by the force of gravity, to the periphery thereof.

Abstract: A drum screen for cleaning and classifying wood chips is mounted for rotation. The screen has apertures of varying size to permit cleaned chips to pass through to be deposited on conveyors located below. An internal annular spiral baffle extends the full length of the drum and a series of chip lifters are located between the flights of the spiral baffle and project radially inwards from the interior surface of the drum. Wood chips are fed into the drum at one end and are carried through the drum while being lifted towards the axis of the drum by the chip lifters to effect loosening of waste material from the chips. Cleaned chips pass through the apertures in the drum and chips too large to pass through are carried forward and discharged from the end of the drum onto a conveyor. A casing surrounds the upper portion of the drum and partially encloses the discharge end of the drum. An air suction device is connected to the discharge end of the drum, drawing off all waste material loosened from the chips.