The drive mechanism may also include either a set of timing gears or {HEAD ~ a spring coupling} to achieve {TAIL ~ the desired intermittent rotation} 
to achieve
The drive mechanism may also include either a set of timing gears or { HEAD ~ a spring coupling } to achieve { TAIL ~ the desired intermittent rotation }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL