Scientific Frontiers in Research on Extrasolar Planets

A rotary comminuting apparatus adjustable to reduce either hard or soft materials includes a segmented perforated semi-cylindrical grate partially surrounding the lower portion of the rotor. The grate segments are pivotally supported on a common axle parallel to the axis of the rotor. The opposite ends of the segments are each supported by a hydraulic jack and the jacks have a common connection to a motor pump unit to pivot the grates from a lower position concentric with the rotor to an upper position in which the outer edge is closer to the rotor surface than the pivot edge.