One or more of such shutters may pivot about their hinges in {HEAD ~ opposite} of the clockwise and {TAIL ~ counterclockwise directions} in moving from radially inner to outer position 
One or more of such shutters may pivot about their hinges in { HEAD ~ opposite } of the clockwise and { TAIL ~ counterclockwise directions } in moving from radially inner to outer position
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD REL OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH