Multi-level load limiting torsion bar retractor

An energy absorbing retractor (20) having

• a spool,
• torsion means (200, 206, 206a) for generating selected levels of reaction torque on the spool permitting the spool to rotate in a controlled manner in a belt protracting direction including a middle portion (202) and a first torsion member (206a) extending therefrom, the middle portion fixedly coupled to the spool to prevent relative rotation therebetween,
• a frame (22), wherein the spool is rotationally supported relative to the frame,
• a locking mechanism (60, 60a, 56, 66, 66a) comprising a primary mechanical first locking mechanism (66a, 58) adapted to initially stop the spool (30) from rotating in a belt protraction direction while permitting the spool and torsion means to rotate thereafter in the direction of belt protraction, the primary mechanical first locking mechanism including a mechanical vehicle sensor operable to initiate lockup of the primary mechanical first locking mechanism at a first level of vehicle deceleration;
• a seat belt (36) wound about the spool, and
• bias means (80) to retract the seat belt,
• the first torsion member including a first end (208a) operatively coupled to the primary mechanical first locking mechanism (66a, 58), the first locking mechanism when in a locked condition prevents the first end from rotating, whereby when the spool is loaded, the first torsion member (206a) twists and deforms torsionally to generate a controlled, reaction force having a first level,
• wherein the torsion means includes a second torsion member (206) extending from the middle portion opposite to the first torsion member (206a), the second torsion member including a second end (208) operatively coupled to a second locking mechanism (66, 58) to prevent the second end from rotating when the second locking mechanism is in a locked condition, whereby when the spool is loaded, the second torsion member twists and deforms torsionally to generate a controlled reaction force which supplements the first level of reaction force and
• wherein the second locking mechanism includes a mechanical inertial sensor for initiating the lockup of the second locking mechanism at a level of vehicle deceleration greater than or equal to the first level of deceleration.