Patent ID: 7669794
Filing Date: 2010-03-02
Classification: B60R

Abstract:
1. A seatbelt retractor comprising: a spool for seatbelt protraction and for seatbelt retraction; an energy absorption mechanism for absorbing rotational twist energy from the spool during seatbelt protraction, the energy absorption mechanism being a torsion bar having a non-circular splined portion, a first diametral portion for a relatively high rate of rotational twist energy absorption, and a second diametral portion sized for a relatively low rate of rotational twist energy absorption, the first diametral portion being of a circular cross section having an external circumferential surface; and an outer sheath with external threads, the outer sheath bonded, conforming to and encircling the non-circular splined portion and a portion of the external circumferential surface of the first diametral portion wherein the bond created external along the circumferential surface can withstand a torque prior to breaking higher than a torque at least the first diametral portion of the underlying torsion bar can support wherein the bond breaks along the weakest attachment location between the sheath and the circular cross section of the first diametral portion such that the rate of rotational twist energy absorption drops quickly making a rapid transition to a second lower desired rate of rotational twist energy absorption while the outer sheath and the non-circular splined portion remain bonded, intact and rotationally locked.