SEAT BELT RETRACTOR

摘要

A seat belt retractor has a rotatable spool (1) for retraction or pay-out of seat belt webbing wound thereon, depending upon the rotation direction of the spool. A locking wheel (6) is attached to one end of the spool (1). The spool (1) to is locked to the locking wheel when a crash is sensed. A force limiter allows further payout of the seat belt webbing after the spool (1) has locked to the locking wheel (6), under the influence of a vehicle occupant's forward momentum. The force limiter includes a torsion bar (3) attached at one end to the locking wheel (6) and at the other end to the spool (1), and a secondary force limiter mechanism (5) releasably coupled in the force path between the spool and the locking wheel (6), and a mechanism for de-coupling the secondary mechanism after a predetermined number of turns of the torsion bar (3). The locking mechanism has a locking element (4) that is resiliently biased to a position wherein it locks the spool (1) to the locking wheel (6) and is held out of locking engagement by the secondary force limiting mechanism (5). The retractor is converted into a standard locking retractor after load limiting ensuring that the vehicle occupant is securely restrained against secondary impacts.