It is a further object of the invention to provide {HEAD ~ a change gear system} capable of preventing teeth of a rack gear and {TAIL ~ a pinion} to be broken 
capable of preventing
It is a further object of the invention to provide { HEAD ~ a change gear system } capable of preventing teeth of a rack gear and { TAIL ~ a pinion } to be broken
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH