SEAT BELT RETRACTOR WITH MULTI-LEVEL LOAD LIMITING

摘要

A seat belt retractor has a spool (1) mounted for rotation in the retractor for retraction or pay-out of seat belt webbing depending upon the rotation direction of the spool. A locking ring (8) is attached to one end of the spool. A lock bar locks the locking ring against rotation when a crash is sensed. A load limiter allows further pay-out of the seat belt webbing after the spool has locked under the influence of a vehicle occupant's forward momentum. The load limiter is a torsion bar (2) attached at one end to the locking ring and at the other end to the spool; and a wire releasably coupled in the force path between the spool and the locking ring. The resilient mechanism, i.e. the wire (4) decouples itself after a predetermined number of turns of the torsion bar. The thickness, length and composition of the wire, together with the number of wires may be chosen to suit a vehicle's crash criteria.