The distance of each roller from the rotation axis and the angles between adjacent rollers are predetermined such that, at any time during a rotation cycle, {HEAD ~ two rollers} engage {TAIL ~ at least one currently active tooth} 
engage
The distance of each roller from the rotation axis and the angles between adjacent rollers are predetermined such that , at any time during a rotation cycle , { HEAD ~ two rollers } engage { TAIL ~ at least one currently active tooth }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL