Seat belt retractor

A seat belt retractor comprising:

• (a) a spool mounted for rotation for retraction or pay-out of seat belt webbing depending upon the rotation direction of the spool, the spool having two elongate recesses therein;
• (b) a locking ring attached to one end of the spool;
• means for locking the locking ring against rotation when a crash condition is sensed;
• and
• (c) a force limiting means for allowing further pay-out of the seat belt webbing after the locking ring has locked, under the influence of a vehicle occupant's forward momentum, coupled in a force path between the spool and the locking ring, the force limiting means comprising
• (i) a primary force limiting means comprising a torsion bar;
• and
• (ii) a secondary force limiting means comprising an elongate deformable wire, arranged such that relative rotation between the spool and the locking ring causes a portion of the length of the wire to be deformed during a first stage of load limiting, wherein the cross-sectional area of the wire is uniform over a major portion of the length of the wire and is reduced over two minor portions of the length of the wire, said minor portions each being located a distance from an end of the wire in the region of a bent part of the wire to reduce the initial bending moment of the wire, each end of the wire being disposed in one of the elongate recesses in the spool.

A seat belt retractor comprising:

• (a) a spool mounted for rotation for retraction or pay-out of a seat belt webbing depending upon the rotation direction of the spool, the spool having two elongate recesses therein;
• (b) a locking ring attached to one end of the spool;
• means for locking the locking ring against rotation when a crash condition is sensed, the locking ring having a groove in a substantially flat side of the locking ring;
• and
• (c) a force limiting means for allowing further pay-out of the seat belt webbing after the locking ring has locked, under the influence of a vehicle occupant's forward momentum, coupled in a force path between the spool and the locking ring, the force limiting means comprising
• (i) a primary force limiting means comprising a torsion bar that is coaxial with the spool and that further functions as a spindle;
• and
• (ii) a secondary force limiting means comprising an elongate deformable wire, arranged such that relative rotation between the spool and the locking ring causes a portion of the length of the wire to be deformed during a first stage of load limiting, wherein the cross-sectional area of the wire is uniform over a major portion of the length of the wire and is reduced over two minor portions of the length of the wire, said minor portions each being located a distance from an end of the wire in the region of a bent part of the wire to reduce the initial bending moment of the wire, the wire having a reduced cross-sectional area tapered portion located at each end of the wire with each end of the wire being disposed in one of the elongate recesses in the spool and a central portion of the wire being disposed in the groove in the locking ring.