| 摘要 |
A safety seat belt arrangement comprises a retractor or spool assembly including a spool (20), carrying the seat belt, rotatable in a frame (18) unless blocked by a blocking mechanism (25), the spool assembly including a head member (22) cooperating with the blocking mechanism. A load limiting torsion bar assembly within the spool and acting between the head member and the spool includes a high level torsion bar portion (24), a low level torsion bar portion (26) and an intermediate torsion element in the form of a torsion pipe (36) fixed at its ends with respect to the ends of the torsion bar portion (26). A torque tube (32) initially provides a direct drive connection between the outer end of the spool (20) and the outer end (24A) of the high level torsion bar portion, so that, in a frontal impact situation, in which the blocking mechanism blocks rotation of the head member, the torque applied to the spool by the belt tension is transferred to the head member principally via the high level torsion bar (24), limiting the belt tension to a relatively high level, until the torque tube is disconnected from the outer end of the spool in a changeover operation effected by a changeover mechanism (28, 40, 42) after which the belt tension is limited by twisting of the bar portion (26) and the torsion pipe (36) together, until the torsion pipe breaks, leaving rotation of the spool restrained only by twisting of the low level torsion bar part (26).
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