To accurately mesh the gears of a rack with a pinion, when the rack and the pinion in a non-engaged state normally are meshed with each other and materialize it by a simple and compact structure.
A pretensioner 20 is so constituted that a pinion 22 is connected to a winder shaft 16 and a rack 30 is provided in the pinion 22 in a non-engaged state normally. A sub-pinion 40 is provided adjacent to the pinion 22, a first engagement tooth 42 is meshed with the rack 30, and a second engagement tooth 44 is engageable with the pinion 22. When the pretensioner 20 is operated to mesh the rack 30 with the pinion 22, the sub-pinion 40 is rotated with the movement of the rack 30 so that the second meshing tooth 44 is engaged with the tooth edge of the pinion 22. Then, a torque is generated in the pinion 22, and the meshing between the teeth of the rack 30 and the pinion 22 is guided so that the both can be appropriately meshed with each other.
HORI SEIJI
TSUKIYAMA HISAHIRO
