Seat belt pretensioner
View Patent ↗A seat belt pretensioner for a belt retractor includes a member that rotates relative to a frame of the belt retractor in response to a vehicle condition to rotate a spool of the belt retractor relative to the frame. A drive device rotates the member in response to the vehicle condition. The drive device applies a first torque to the member during a first stage of rotation of the member and the spool and applies a second torque greater than the first torque during a second stage of rotation of the member and the spool. A flexible drive member rotates the member relative to the frame. The flexible drive member extends around an axis of the member more than 360° after activation of the pretensioner.
1. A seat belt pretensioner for a belt retractor comprising:
a member that rotates relative to a frame of the belt retractor in response to a vehicle condition to rotate a spool of the belt retractor relative to the frame;
a drive device for rotating the member in response to the vehicle condition, the drive device applying a first torque to the member during a first stage of rotation of the member and the spool and applying a second torque greater than the first torque during a second stage of rotation of the member and the spool.
2. A seat belt pretensioner as set forth in claim 1 wherein the drive device applies the first torque to the member upon activation of the seat belt pretensioner and applies the second torque to the member after the first stage of rotation.
3. A seat belt pretensioner as set forth in claim 2 wherein the drive applies the second torque to the member after approximately 360° of rotation of the member relative to the frame.
4. A seat belt pretensioner as set forth in claim 1 wherein the drive device includes a flexible drive member engaging the member and a device for moving the flexible drive member relative to the frame, the flexible drive member extending around an axis of the member more than 360° after activation of the pretensioner.
5. A seat belt pretensioner as set forth in claim 4 further including a first guide engaging the flexible drive member to cause the flexible drive member to extend around the axis of the member.
6. A seat belt pretensioner as set forth in claim 5 wherein the first guide rotates with the member relative to the frame.
7. A seat belt pretensioner as set forth in claim 5 wherein a second guide guides movement of the flexible drive member into the first guide.
8. A seat belt pretensioner as set forth in claim 7 wherein the second guide moves relative to the first guide and the frame to guide the flexible drive member into first and second portions of the first guide.
9. A seat belt pretensioner as set forth in claim 8 wherein a guide member on the second guide engages the first guide to move the second guide relative to the first guide and the frame.
10. A seat belt pretensioner as set forth in claim 5 wherein the first guide has a first portion into which the flexible drive member extends during the first stage of rotation and a second portion into which the flexible drive member extends during the second stage of rotation.
11. A seat belt pretensioner as set forth in claim 10 wherein the first guide includes a generally helical passage for receiving the flexible drive member.
12. A seat belt pretensioner as set forth in claim 4 wherein a portion of the flexible drive member extends at an angle of between 10° and 30° relative to a line extending perpendicular to an axis about which the member rotates.
13. A seat belt pretensioner for a belt retractor comprising:
a member that rotates relative to a frame of the belt retractor in response to a sensed vehicle condition to rotate a spool of the belt retractor relative to the frame;
a flexible drive member engaging the member to rotate the member relative to the frame, the flexible drive member extending around an axis of the member more than 360° after activation of the pretensioner.
14. A seat belt pretensioner as set forth in claim 13 wherein the flexible drive member applies a first torque to the member upon activation of the seat belt pretensioner during a first stage of rotation of the member and applies a second torque greater than the first torque during a second stage of rotation of the member after the first stage of rotation.
15. A seat belt pretensioner as set forth in claim 14 wherein the drive applies the second torque to the member after approximately 360° of rotation of the member relative to the frame.
16. A seat belt pretensioner as set forth in claim 13 further including a first guide engaging the flexible drive member to cause the flexible drive member to extend around the axis of the member.
17. A seat belt pretensioner as set forth in claim 16 wherein the first guide rotates with the member relative to the frame.
18. A seat belt pretensioner as set forth in claim 16 wherein a second guide guides movement of the flexible drive member into the first guide.
19. A seat belt pretensioner as set forth in claim 18 wherein the second guide moves relative to the first guide and the frame to guide the flexible member into first and second portions of the first guide.
20. A seat belt pretensioner as set forth in claim 19 wherein a guide member on the second guide engages the first guide to move the second guide relative to the first guide and the frame.
21. A seat belt pretensioner as set forth in claim 16 wherein the first guide includes a generally helical passage for receiving the flexible drive member.
22. A seat belt pretensioner as set forth in claim 13 wherein a portion of the flexible member extends at an angle of between 10° and 30° relative to a line extending perpendicular to an axis about which the member rotates.