Retractor with multiple level load limiter

A multi-level, energy absorbing or dissipating retractor comprising:

• a spool having a seat belt wound thereon for protraction and retraction;
• a locking mechanism engageable with the spool and operable to initially stop the spool from rotating in a belt protraction direction;
• a first torsion element for absorbing or dissipating energy by turning of the spool due to a passenger's inertia force on the seat belt;
• a second torsion element for absorbing or dissipating energy by turning of the spool due to a passenger's inertia force on the seat belt;
• and
• a coupling for coupling the first and second torsion elements sequentially according to the amount of spool rotation generated by the passenger's inertia force on the belt after operation of the locking mechanism to provide the first and second levels of energy absorption.

A seat belt retractor for energy absorption or dissipation comprising:

• a rotatable spool having a seat belt wound thereon for protraction and retraction and have an internal bore, a first end and a second end;
• a locking mechanism moveable to a locking position to initially lock the spool against belt protraction at the time of an accident;
• a torsion bar in the bore of the spool and having a first end which is held against rotation by the locking mechanism in its locking position, a second end on the torsion bar connected to the spool to be turned thereby when the first end is being locked against rotation by the locking mechanism;
• a first portion on the torsion bar twisted by the spool for energy absorption or dissipation at a first amount after the initial locking of the first end of the torsion bar;
• a second portion on the torsion bar twisted by the spool for energy absorption or dissipation by a second amount different from the first amount;
• and
• coupling elements for selectively coupling the spool for twisting the first portion of the torsion bar to cause the first amount of energy absorption or dissipation with initial rotation of the spool after the locking of the first end of the torsion bar by the locking mechanism and decoupling the first portion from the spool after a predetermined amount of spool rotation with the spool turning the second end of the torsion bar and allowing the second portion to twist for absorbing or dissipating energy at the second different amount.

A method operating a multi-level energy absorption retractor having a seat belt wound on a spool having a spool bore with first and second torsion elements therein selectively coupled to the spool for providing different levels of energy absorption without use of a remotely operated switching device, comprising:

• twisting the first torsion element in the spool bore by inertia force of a passenger when a first end of the retractor is locked to provide a first level of energy absorption;
• operating a coupling to transition to a second level of energy absorption after a predetermined amount of rotation of the spool generated by the passenger's inertia force;
• and
• twisting the second torsion element with continued rotation of the spool by the passenger's inertia force after operating the coupling to provide the second, different level of energy absorption.