PURPOSE: To reduce the module consisting of a number of pinions and the rack gears of the rack shaft without decreasing transmission torque by engaging each of the pinions with the rack gears and simultaneously driving them by the revolution of a handle shaft.

CONSTITUTION: On a rack shaft 1, the first pinion 3a that is directly driven in turn by a handle is engaged with the second pinion 3b that is driven in turn by the pinion 3a through gears. The first pinion 3a is revolved in the same direction as the handle shaft by the revolution of the handle and moves the rack shaft 1 in one direction. Besides, since the second pinion 3b is engaged with the second rack gear train 5b, it also moves the rack shaft 1 in the same direction. As a result, the torque transmitted by the revolution of the handle shaft is shared by the first and second pinions 3a and 3b and both the moldule of the gear and the rack stroke can be reduced.