Center fed mill with arcuate discharge screens

Claim 1

Apparatus for size reduction of material which comprises: a. an impeller, means for rotating the impeller, said impeller having impeller blades, said means for rotating the impeller moving the blades through a path, said impeller blades being for projecting particles of the material to be size reduced outwardly of the path of the impeller blades as a dispersion of the particles; b. a housing for the impeller, said housing having an internal surface and an inlet for center feeding of the material to the mill; c. a plurality of stationary cutters each having a substantially flat working surface with cutting teeth formed therein, disposed at spaced intervals about the impeller path; d. a smooth surfaced screen forming an axially extending portion of a cylinder coaxial with the impeller, mounted in the housing for screening of the dispersion; e. the cutters being disposed tangentially at a locus of tangency with respect to the path of the impeller blades terminating in circumferentially spaced ends each spaced a substantial distance from the locus of tangency and connecting with the internal surface of the housing, the cutters being chords of said screen cylinder; and f. the contour of the internal surface of the housing where it connects with said cutter ends being concave so that movement of the dispersion to and from the cutter occurs without deposit of material from the dispersion.