Image Number 2 for United States Patent #7740198.
A straw chopper includes a pair of shafts supported in a chopping chamber for rotation about respective longitudinal axes extending generally in a forward working direction of the chopper. Chopping blades are supported on each shaft, offset in a direction of the longitudinal axes in relation to the chopping blades of the other shaft so that the shafts can be positioned with a sweep area of the blades overlapping one another. The shafts are rotated in a common direction of rotation such that the blades of one of the shafts are displaced in an opposite direction to the blades of the other one of the shafts at the overlap of the sweep areas. Each chopping blade includes an impeller surface sloped forwardly into a direction of rotation so as to generate a rearward thrust of air in the chopping chamber in the longitudinal direction of the axes from the inlet to the outlet of the chamber as the shafts are rotated.