The tooth shape at around the pitch circle of the outer tooth gear of the pinion to be connected to the prime mover or driven shaft has a tooth surface which is in axial direction at around the central portion of the tooth width and which contacts at around the tooth width end at the allowable displacement angle and the backlash is made small and {HEAD ~ the outer tooth gear} of the pinion is crowned in to {TAIL ~ an exponential function curve} 
The tooth shape at around the pitch circle of the outer tooth gear of the pinion to be connected to the prime mover or driven shaft has a tooth surface which is in axial direction at around the central portion of the tooth width and which contacts at around the tooth width end at the allowable displacement angle and the backlash is made small and { HEAD ~ the outer tooth gear } of the pinion is crowned in to { TAIL ~ an exponential function curve }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH REL REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL