The elastic coupling member may be {HEAD ~ a spring member} engaging with both the driving arm and {TAIL ~ the driven arm} 
engaging with
The elastic coupling member may be { HEAD ~ a spring member } engaging with both the driving arm and { TAIL ~ the driven arm }
OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL