PURPOSE: To aim at eliminating the occurrence of speed-change delays due to a backlash by fixing in an eccentric state a tapered shaft on the intermediate shafts of an even number of intermediate gears, and then causing through the rotation of the tapered shaft the intermediate shafts by haploid numbers each to be moved clockwise and counterclockwise for regulation so that the backlash of gears is eliminated before the gears are fixed.

CONSTITUTION: Intermediate gears 8a, 8b... are provided in an even number, and then, on each one end of their intermediate shafts 9a, 9b is fixed a tapered shaft 10 in an eccentric state. Following the rotation of the tapered shaft 10, the intermediate gears 8a... by haploid numbers each are moved clockwise and counterclockwise and regulated so that the backlash of gears is eliminated. In addition, at the then position, with the tapered shaft 10 is engaged firmly a notched annular stator 15 by means of a nut 12 so that the intermediate gears 8a... are fixed. Therefore, the backlash when the direction of rotation in the star-type gearing mechanism is changed over into normal and reverse becomes zero, and an accurate and smooth transmission can be performed accordingly.