Seat belt retractor

1. A seat belt system for protecting an occupant of a vehicle, the system comprising:

a belt webbing connected to a seat belt retractor;

wherein the retractor includes

a frame;

a spool configured to be fixed to one end of a webbing so that the webbing may be wound around the spool, the spool being rotatably mounted at both ends to the frame and configured to rotate in a webbing extraction direction and a webbing retraction direction;

an energy absorbing device configured to absorb energy when the spool is rotated in the webbing extraction direction after an emergency event has occurred and operation of the energy absorbing device is triggered;

a mechanism for selectively cancelling the operation of the energy absorbing device by preventing motion of the spool in the webbing extraction direction, wherein the mechanism for cancelling the operation of the energy absorbing device is activated after the energy absorbing device is triggered.

2. The seat belt system of claim 1 , wherein the mechanism for cancelling the operation of the energy absorbing device includes a pawl pivotably mounted on the frame, and wherein the pawl is configured to be driven to pivot into a position to engage the spool and prevent further movement of the spool in the webbing extraction direction.

3. The seat belt system of claim 1 , further comprising:

a pre-tensioning device that provides tension to the seat belt webbing.

4. The seat belt system of claim 1 , wherein the energy absorbing device comprises a torsion bar mounted onto the spool along a rotational axis of the spool, and wherein the torsion bar has one end free to rotate unless the free end is inhibited from rotating when the mechanism for cancelling the operation of the energy absorbing device is activated.

5. The seat belt system of claim 1 , wherein the mechanism for cancelling the operation of the energy absorbing device includes a flexible band that wraps around at least a portion of the spool, and wherein the band is configured to be cinched around the spool to thereby prevent further rotation of the spool in the webbing extraction direction.

6. The seat belt system of claim 5 , wherein the flexible band wraps around more than half of the spool.

7. The seat belt system of claim 1 , wherein the retractor is positioned behind a vehicle seat.

8. The seat belt system of claim 7 , wherein the seat belt system is positioned behind a front seat of a vehicle.

9. The seat belt system of claim 1 , wherein the system further comprises:

a sensor to detect vehicle acceleration.

10. The seat belt system of claim 9 , further comprising:

a controller for receiving signals from the sensor and for activating the mechanism for cancelling the operation of the energy absorbing device in response to the signals received from the sensor.

11. The seat belt system of claim 10 , wherein the controller is configured to activate the mechanism for cancelling the operation of the energy absorbing device during a low offset impact event.

12. The seat belt system of claim 1 , wherein the mechanism includes a wedge member that wedges in a position between the spool and the retractor frame to thereby prevent further movement of the spool in the webbing extracting direction.

13. The seat belt system of claim 12 , wherein the wedge member wedges into a position between the spool and the retractor frame has teeth thereon, and the teeth engage with a flange on the spool.

14. The seat belt system of claim 12 , wherein the mechanism for cancelling the operation of the energy absorbing device includes a pyrotechnic device for providing a force to drive the wedge member into the wedged position between the spool and the retractor frame.

15. The seat belt system of claim 12 , wherein the wedge member forces the spool to engage the retractor frame to thereby prevent further movement of the spool in the webbing extraction direction.

16. The seat belt system of claim 12 , wherein the wedge member is drawn along with rotation of the spool and wedges into a final position in a gap between the spool and the frame of the retractor.

17. The seat belt system of claim 16 , wherein the spool has a flange thereon and wherein the frame of the retractor has teeth thereon, and wherein the spool flange is pushed into contact with the teeth of the retractor frame when the wedge member is in the final position in the gap between the spool and the frame of the retractor.

18. The seat belt system of claim 16 , wherein the wedge member prevents rotation of the spool, thereby ceasing the operation of the energy absorption device when the wedge member is in the final position in the gap between the spool and the frame of the retractor.

19. A seat belt system for protecting an occupant of a vehicle, the system comprising:

a belt webbing connected to a seat belt retractor;

wherein the retractor includes

a frame;

a spool configured to be fixed to one end of a webbing so that the webbing may be wound around the spool, the spool being rotatably mounted at both ends to the frame and configured to rotate in a webbing extraction direction and a webbing retraction direction;

an energy absorbing device configured to absorb energy when the spool is rotated in the webbing extraction direction after an emergency event has occurred;

a mechanism for cancelling the operation of the energy absorbing device by preventing motion of the spool in the webbing extraction direction; and

wherein the energy absorbing device comprises a torsion bar mounted onto the spool, and wherein the mechanism prevents the torsion bar from twisting.

20. The seat belt system of claim 19 , wherein the torsion bar is located along a rotational axis of the spool.