A machine for large-scale size reduction of rocks, ore, or mineral aggragate. Essentially, it comprises a vertical cone-shaped crushing head or mantle that moves in a shell shaped like an inverted cone that is open at the top where the feed enters. The space between the mantle and the shell decreases gradually, being smallest at the bottom where the crushed material is discharged. The lower third of the mantle and shell have concave surfaces to minimize packing of the crushed product. The crushing head functions by executing a gyratory or circular motion, i.e., a rolling action in which the upper portion describes a circle while the lower portion is almost stationary. From 300–500 gyrations per minute are possible. The mechanism is activated by a shaft attached to the crushing head, the bottom of which rests in a gear-driven eccentric. Heavy-duty gyratories have feed openings up to 72 inches; fine-reduction sizes are as small as 12 inches.
