US Patent 7144309 Rotational processor with drive rollers

A rotational processor comprises an outer vessel and a plurality of inner vessels having an outer traction surface adapted for rolling contact with an inner surface of the outer vessel. A plurality of drive rollers drive the inner vessels about a center line of the outer vessel in rolling contact with the outer vessel. Each of the drive rollers contacts each of a pair of adjacently located inner vessels when the inner vessels are not being driven about the outer vessel. The outer traction surfaces compress in response to centrifugal forces applied by the rolling contact with the outer vessel such that each of the drive rollers separates from one of the adjacently located pair of the inner vessels.