Abstract: A screening apparatus (10) for screening particulate material includes a frame (12) having an open bottom (14) through which screened particles can pass and a plurality of banks of blades (16A–16E) supported on the frame (12). Each bank of blades (16) is rotatable about respect axes of rotation (18A–18E). The blades (20) of each bank (16) are evenly spaced and arranged in a single row coincident with their respective axes of rotation (18). At least one of the banks of blades (16) is able to slide linearly along its respective axis of rotation (18) to provide a predetermined amount of axial freeplay. When the blades (20) agitate rotated and a particulate material is placed in screen frame (12), the rotating blades (20) agitate and/or crush the material to allow particles of a size equal to or smaller than a gap formed between each of the adjacent blades to fall through the open bottom.

Abstract: A mobile screening apparatus includes a horizontal rotary drum preferably fed by underflow from a prescreening device that is reversible endless belt of screening grizzly bars. The belt reverses for expelling oversize material caught between bars. Force needed to turn the drum is monitored, as a way of controlling drum feeding by the prescreening device, for preventing protracted over-filling of the drum. The screening drum includes an outer peripheral cage of longitudinal bars, at least some of which preferably are movably mounted. A set of wires is circumferentially wrapped about the bar cage, with sufficient flexibility to permit the wires to locally elastically flex away from the bars sufficient to pass slightly oversize material and facilitate cleaning of debris lodged in spaces among the bars and wires. Brushes help dislodge lodged debris.