Patent ID: 7232089

Claim:
A seat belt retractor including a take-up drum with webbing wound therearound, the take-up drum being rotatably urged in a direction in which the webbing is wound up, a torsion bar fitted by insertion in the take-up drum and having a first end coupled to a first end of the take-up drum non-rotatably relative thereto, a ratchet wheel coupled to a second end of the torsion bar non-rotatably relative thereto, an emergency locking member operative, in the event of a vehicle emergency, to be locked to the ratchet wheel to stop the rotation of the ratchet wheel, thereby stopping the rotation of the take-up drum in a direction in which the webbing is paid out, the torsion bar being twistingly deformed when the webbing is further paid out after the emergency locking member is locked, said seat belt retractor comprising: a cylindrical sun element provided on a second end of said take-up drum and rotating integrally with the take-up drum; an internal tooth element provided near the second end of said torsion bar non-rotatably relative to the torsion bar and having an inner peripheral surface opposed to and spaced apart from an outer peripheral surface of said sun element, one of the outer peripheral surface of the sun element and the inner peripheral surface of the internal tooth element being a gear surface, the other being formed by a deformable member; and at least one planet gear, said planet gear being assembled in mesh with said gear surface and in engagement with said deformable member opposed to said gear surface, wherein the planet gear revolves around the deformable member while biting into the surface of the deformable member to plastically deform the deformable member when the webbing is paid out to cause the sun element and the internal tooth element to rotate relative to each other after said emergency locking member is locked.