Patent ID: 7204438

Claim:
An impact crushing apparatus having an inlet opening for supplying raw material to be milled, a milling cylinder disposed below the inlet opening and having a plurality of blades equally spaced on the outer edge of the milling cylinder, a screen cylinder fixed outward of the outer edge of the milling cylinder, an outlet path disposed outward of the screen cylinder for ejecting milled material, and a driving section for rotating the milling cylinder, wherein: the milling cylinder has an upper ring and a lower ring with a common central axis, the upper ring and the lower ring being separated by a predetermined spacing; each of the plurality of blades includes a columnar main body with a polygonal cross section and cutting tools attached along a plurality of ridges of the columnar main body; and one of a plurality of mounting directions of the blade relative to the upper ring and the lower ring is selected by rotating the blade through a predetermined angle around the central axis of the columnar main body of the blade and by mounting the top of the blade to the upper ring and also mounting the bottom to the lower ring.