Patent ID: 8628036

Claim:
A tub grinder comprising: a frame; a substantially horizontal floor operatively attached to the frame; an opening disposed in the floor; a circular wall operatively rotatably attached to the frame, the circular wall being disposed generally above the floor and encircling the floor so that when the circular all rotates material on the floor is moved in the same direction as the circular wall is moving; a rotor operatively rotatably attached for rotation in a first direction relative to the frame about a longitudinal axis; a plurality of slug bars operatively rigidly attached to the frame and extending across the opening in the floor, each of the slug bars having a top and a bottom, a first end and a second end, the slug bars have a thickness measured between a first side and a second side; a plurality of riser bars rigidly attached to the top of respective slug bars, the riser bars extending vertically higher on the first end of the slug bar than on the second end of each respective slug bar, the riser bars have a thickness measured between a first side and a second side; and a plurality of hammers spaced apart and pivotally attached to the rotor, the hammers passing between adjacent slug bars as the rotor rotates in the first direction about the longitudinal axis, respective hammers entering a space between respective adjacent riser bars on the first end where the riser bars are vertically higher before the respective hammers enter the space on the second end where the respective adjacent riser bars are lower, the hammers extending farther vertically upwardly with respect to each of the respective adjacent riser bars on said second end of the riser bars than on the first end of the riser bars.