Impeller assembly for processing device
 An impeller of an impeller assembly for a processing device has a spiral ove formed in a circumferential side face so that material entering a clearance space between the circumferential side face of the impeller and inner circumferential walls of the processing device is guided out of the clearance space when the impeller assembly is rotated. The spiral groove prevent material from lodging in the space and jamming the impeller assembly. 
The United States of America as represented by the Secretary of the Navy
B D D B
B02C D21B D21B B02C
inventional inventional inventional inventional
John L. John D.
Drake, Jr. Spargo