Multiple level load limiter for primary and secondary collisions

摘要

An energy absorbing seat belt retractor comprising: a frame (22); a spool (24) rotatably mounted relative to the spool including a lock wheel (71) having a plurality of lock teeth associated therewith and adapted to receive a seat belt thereabout; a lock pawl (77) for engaging the spool upon sensing a one of a vehicle deceleration and seat belt extraction above certain determinable levels; and movable nut (90) located in the spool and for prohibiting relative movement between the lock wheel and spool below a threshold input force level generated in part by occupant load on the seat belt and for generating a controlled energy dissipating reaction force on the seat belt after the input force exceeds the threshold level to permit a controlled rotation of the spool and the controlled pay-out of the seat belt from the spool during a first and subsequent accidents.