Patent ID: 7124974

Claim:
A seat belt retractor comprising: a spool for winding up a seat belt rotatably held in a frame; a bearing attached to a portion of said spool held by said frame; a clutch mechanism arranged on one end of said spool; a pretensioner disposed adjacent to said clutch mechanism; and wherein said spool is made of light alloy, and said bearing is made of steel, wherein said pretensioner comprises: a gas generator; a plurality of serial driving members positioned to be accelerated by gas generated from said gas generator; a path for guiding said driving members; a first rotational member having a plurality of levers, wherein said driving members collide with said levers so as to apply rotational torque to said first rotatable member; a second rotational member fixed to said spool; and a clutch mechanism formed by said first rotational member and said second rotational member, wherein said second rotational member being a pinion having external teeth; said first rotational member being a ring gear having internal teeth capable of meshed with the external teeth of said pinion and the levers around the outer periphery thereof; said clutch mechanism becomes in its coupled state where the internal teeth of said ring gear are meshed with the external teeth of said pinion thereby allowing said accelerated driving members to push the levers of said ring gear so as to move said ring gear; and said clutch mechanism being in its decoupled state before the activation of pretensioner and switching into its coupled state by the rotation of said first rotational member when the pretensioner is activated.