{HEAD ~ The internal gear} is made of an elastic resin and is separated from {TAIL ~ the casing} of the system or a metal ring fitted in the casing by a predetermined gap 
{ HEAD ~ The internal gear } is made of an elastic resin and is separated from { TAIL ~ the casing } of the system or a metal ring fitted in the casing by a predetermined gap
HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH