{HEAD ~ Each sliding frame} is provided with a pair of {TAIL ~ rack gears} with teeth facing each other and cam surfaces facing each other in parallel with a pitch line of the rack gears 
{ HEAD ~ Each sliding frame } is provided with a pair of { TAIL ~ rack gears } with teeth facing each other and cam surfaces facing each other in parallel with a pitch line of the rack gears
HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH