The invention is a center fed hammer mill having a base plate, one or more intermediate plates having a central opening or hole, the intermediate plates being held together in fixed relative position by pins running through the outer edge of the intermediate plates, one or more hammers attached to the pins and a top plate having a central hole which is coextensive with the central hole of the intermediate plates, as well as a tube affixed to the top plate. The invention also comprises a method of using a center fed hammer mill.

http://www.freepatentsonline.com/5240190.html