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