Load limiting seat belt retractor with spiral turn limiter

Patent metadata

Field	Value
Publication number	US-9469272-B2
Application number	US-201414199024-A
Country	US
Kind code	B2
Filing date	Mar 6, 2014
Priority date	Mar 15, 2013
Publication date	Oct 18, 2016
Grant date	Oct 18, 2016

Abstract

A motor vehicle seat belt retractor having load limiting features for controlling seat belt restraint loads for a retractor having a spool for storing belt webbing and rotatable with respect to a retractor frame, and a locking mechanism for locking the spool to provide vehicle occupant restraint. A load limiting element coupled with the spool limits restraint loading of the seat belt webbing upon locking of the spool. A rotational displacement limiting mechanism limits the displacement of the load limiting element, the limiting mechanism having a cam forming a spiral flight rotatable with the load limiting element and a cam follower engaging the spiral flight. The cam and the cam follower interengage to reach an end position preventing further relative angular displacement beyond a predetermined angular displacement of the load limiting element. Embodiments provide various configurations for the cam and cam follower elements.

First claim

The invention claimed is:

1. A motor vehicle seat belt retractor having load limiting features for controlling restraint load acting on seat belt webbing stored on the retractor, the retractor of a type having a spool with a first end coupled to a tread head and a second end opposite the tread head, the spool rotatable with respect to a retractor frame, the spool storing the seat belt webbing wrapped thereon, and a locking mechanism for selectively locking the spool via locking of the tread head to provide vehicle occupant restraint, the retractor comprising:
a load limiting element having a first portion and a second portion, the second portion being rigidly coupled to the second end of the spool to prevent relative rotation between the second portion of the load limiting element and the second end of spool such that the spool rotates along with the second portion of the load limiting element when the locking mechanism is locked, the load limiting element limiting restraint loading of the seat belt webbing in response to locking of the locking mechanism, and
a rotational displacement limiting mechanism for limiting the displacement of the second portion of the load limiting element relative to the first portion of the load limiting element, the rotational displacement limiting mechanism being fixed relative to the retractor frame when the locking mechanism is locked, the rotational displacement limiting mechanism having a cam forming a spiral flight and the rotational displacement limiting mechanism further having a cam follower engaging the spiral flight, wherein, in response to the locking of the locking mechanism, the load limiting element undergoes an initial angular displacement greater than 360 degrees of the second portion relative to the first portion along with a corresponding angular displacement of the spool relative to the tread head and the retractor frame, with the cam and the cam follower interengaging such that the cam follower translates along the spiral flight from an initial position toward an end position, wherein the cam follower will reach the end position of the spiral flight preventing further relative angular displacement between the second portion of the load limiting element and the first portion of the load limiting element beyond a predetermined maximum angular displacement.

2. The motor vehicle seat belt retractor in accordance with claim 1 wherein the cam follower further engages a track coupled with the retractor.

3. The motor vehicle seat belt retractor in accordance with claim 1 wherein the load limiting element is in the form of a torsion bar.

4. The motor vehicle seat belt retractor in accordance with claim 1 wherein the spiral flight comprises two or more interlaced grooves.

5. The motor vehicle seat belt retractor in accordance with claim 1 wherein the cam is a tubular load coupler forming the spiral flight in the form of a helical profile on a surface of the tubular load coupler.

6. The motor vehicle seat belt retractor in accordance with claim 5 wherein the helical profile is formed on an outside surface of the tubular load coupler.

7. The motor vehicle seat belt retractor in accordance with claim 5 wherein the tubular load coupler is positioned inside a cylindrical cavity formed by the spool.

8. The motor vehicle seat belt retractor in accordance with claim 7 wherein the cam follower is in the form of a ball, and the spool forms a guide groove defining a channel for movement of the ball along the inside cylindrical cavity of the spool as the spiral flight rotates relative to the spool.

9. The motor vehicle seat belt retractor in accordance with claim 8 wherein the guide groove has a deformable element disposed therein which resists axial movement of the ball.

10. The motor vehicle seat belt retractor in accordance with claim 8 wherein the ball element is restricted from further movement upon reaching an end of the spiral flight thereby locking the coupler to the retractor frame.

11. The motor vehicle seat belt retractor in accordance with claim 5 wherein the tubular load coupler is positioned on an end of the spool and extending therefrom.

12. The motor vehicle seat belt retractor in accordance with claim 1 wherein the cam is in the form of a first plate having the spiral flight disposed thereon, and the cam follower is in the form of a ball element which moves along the spiral flight and radially within a groove formed by a second plate upon angular displacement of the load limiting element.

13. The motor vehicle seat belt retractor in accordance with claim 12 wherein a deformable sheet is disposed between the first plate and the second plate, the deformable sheet being deformed by the ball element as the ball element moves along the spiral flight and the groove.

14. A motor vehicle seat belt retractor having load limiting features for controlling restraint load acting on seat belt webbing stored on the retractor, the retractor of a type having a spool rotatable with respect to a retractor frame, the spool storing the seat belt webbing wrapped thereon, the retractor comprising:
a load limiting element having a first and a second engagement sections, the first engagement section coupled with the spool to rotate with the spool and the second engagement section selectively coupled with the retractor frame via a locking mechanism in response to locking the locking mechanism, the load limiting element undergoing plastic torsional deformation of the first engagement section relative to the second engagement section thereby limiting restraint loading of the seat belt webbing in response to locking of the locking mechanism, and
a rotational displacement limiting mechanism for limiting the maximum torsional deformation of the first engagement section of the load limiting element relative to the second engagement section of the load limiting element, the rotational displacement limiting mechanism having a cam forming a spiral flight rotatable with the load limiting element second engagement section and having a cam follower engaging the spiral flight, wherein, in response to the locking of the locking mechanism, the first engagement section of the load limiting element undergoes an initial angular displacement greater than 360 degrees relative to the second engagement section of the load limiting element, with the cam and the cam follower interengaging, the cam follower translating along the spiral flight from an initial position toward an end position and, in response to reaching the end position of the spiral flight, further relative angular displacement between the first engagement section of the load limiting element and the second engagement section of the load limiting element is prevented beyond a predetermined maximum angular displacement between the load limiting element first and second engagement sections.

15. The motor vehicle seat belt retractor in accordance with claim 14 wherein the cam follower further engages a track coupled with the retractor.

16. The motor vehicle seat belt retractor in accordance with claim 14 wherein the load limiting element is a torsion bar.

17. The motor vehicle seat belt retractor in accordance with claim 16 wherein the torsion bar is positioned inside a cylindrical cavity formed by the spool.

18. The motor vehicle seat belt retractor in accordance with claim 14 wherein the spiral flight comprises two or more interlaced grooves.

19. The motor vehicle seat belt retractor in accordance with claim 14 wherein the cam is a tubular load coupler forming the spiral flight

Assignees

• Autoliv Asp Inc

Inventors

• Kohlndorfer Kenneth
• Schulz Kurt

Classifications

• B60R22/3413 Primary

  operating between belt reel and retractor frame (B60R22/4676 takes precedence) · CPC title

• B60R2022/286

  using deformation of material · CPC title