Seat belt retractor with load limiting stop mechanism

Patent metadata

Field	Value
Publication number	US-10315617-B2
Application number	US-201615228056-A
Country	US
Kind code	B2
Filing date	Aug 4, 2016
Priority date	Aug 4, 2016
Publication date	Jun 11, 2019
Grant date	Jun 11, 2019

Abstract

A seat belt retractor comprises a rotatable spool on which seat belt webbing is wound. The spool is rotatable in a webbing withdrawal direction and an opposite webbing retraction direction. The seat belt retractor also comprises a pretensioner actuatable to rotate the spool in the webbing retraction direction and a load-limiting system to limit a load applied to a vehicle occupant by the seat belt webbing. The load-limiting system includes a torsion bar mounted such that the torsion bar is twisted when a load in excess of a predetermined load is applied to the spool in the webbing withdrawal direction by the seat belt webbing. The bad-limiting system also includes a stop assembly actuatable to limit rotation of the spool in the webbing withdrawal direction to a predetermined number of rotations while the torsion bar is being twisted. The stop assembly is actuated upon actuation of the pretensioner.

First claim

Having described the invention, the following is claimed:

1. A seat belt retractor comprising:
(a) a rotatable spool on which seat belt webbing is wound, the spool being rotatable in a webbing withdrawal direction and an opposite webbing retraction direction;
(b) a pretensioner actuatable to rotate the spool in the webbing retraction direction; and
(c) a load-limiting system to limit a load applied to a vehicle occupant by the seat belt webbing, the load-limiting system including
(i) a torsion bar mounted such that the torsion bar is twisted when a load in excess of a predetermined load is applied to the spool in the webbing withdrawal direction by the seat belt webbing, and
(ii) a stop assembly actuatable to limit rotation of the spool in the webbing withdrawal direction to a predetermined number of rotations while the torsion bar is being twisted, the stop assembly being actuated upon actuation of the pretensioner.

2. The seat belt retractor according to claim 1 wherein the stop assembly includes
(A) an actuation mechanism rotatable with the spool, a portion of the actuation mechanism being rotatable relative to the spool upon actuation of the pretensioner, and
(B) a counting mechanism actuatable to count the predetermined number of rotations, the counting mechanism being actuated by rotation of the portion of the actuation mechanism relative to the spool.

3. The seat belt retractor according to claim 2 wherein the actuation mechanism includes
(I) a hub member attached to the spool for rotation with the spool, and
(II) an inertia member releasably connected to the hub member in a first orientation relative to the hub member, the inertia member being released from the hub member for limited rotational movement to a second orientation relative to the hub member upon actuation of the pretensioner, the inertia member being the portion of the actuation mechanism rotatable relative to the spool.

4. The seat belt retractor according to claim 3 wherein the actuation mechanism also includes
(III) at least one actuation pawl pivotally mounted on the hub member, and
(IV) at least one spring resiliently biasing the at least one actuation pawl in a radially outward direction relative to the hub member.

5. The seat belt retractor according to claim 4 wherein the inertia member includes a wall that blocks pivotal movement of the at least one actuation pawl in a radially outward direction relative to the hub member when the inertia member is disposed in the first orientation relative to the hub member, the wall including at least one window through which the at least one actuation pawl can pivot in a radially outward direction when the inertia member is disposed in the second orientation relative to the hub member.

6. The seat belt retractor according to claim 4 wherein the counting mechanism includes
(I) a count actuation member rotatable with the spool in the webbing withdrawal direction to count at least partially the predetermined number of rotations, and
(II) a locking mechanism that blocks rotation of the count actuation member with the spool in the webbing withdrawal direction after the predetermined number of rotations, the locking mechanism also blocking rotation of the spool in the webbing withdrawal direction to stop twisting of the torsion bar.

7. The seat belt retractor according to claim 6 wherein the at least one actuation pawl pivots relative to the hub member to engage the count actuation member when the inertia member is released from the hub member and rotates to the second orientation relative to the hub member upon actuation of the pretensioner, engagement of the at least one actuation pawl with the count actuation member initiating counting of the predetermined number of rotations when the spool is rotated in the webbing withdrawal direction.

8. The seat belt retractor according to claim 2 wherein the counting mechanism of the stop mechanism includes
(I) a count actuation member rotatable with the spool in the webbing withdrawal direction to count at least partially the predetermined number of rotations, and
(II) a locking mechanism that blocks rotation of the count actuation member in the webbing withdrawal direction after the predetermined number of rotations, the locking mechanism also blocking rotation of the spool in the webbing withdrawal direction to stop twisting of the torsion bar.

9. The seat belt retractor according to claim 1 wherein the stop assembly is actuated by actuation of the pretensioner.

10. The seat belt retractor according to claim 1 wherein the stop assembly limits twisting of the torsion bar.

11. A method for limiting a load applied to a vehicle occupant by seat belt webbing in a vehicle crash condition, the method comprising the steps of:
(a) winding seat belt webbing on a rotatable spool of a seat belt retractor;
(b) actuating a pretensioner to rotate the spool in a webbing retraction direction in response to an actual or anticipated crash event involving a vehicle in which the seat belt retractor is mounted;
(c) twisting a torsion bar; and
(d) actuating a stop assembly upon actuation of the pretensioner to limit rotation of the spool in a webbing withdrawal direction to a predetermined number of rotations while the torsion bar is being twisted.

12. The method according to claim 11 wherein the stop assembly includes an actuation mechanism rotatable with the spool and wherein the step of actuating the stop assembly includes rotating a portion of the actuation mechanism relative to the spool upon actuation of the pretensioner.

13. The method according to claim 12 wherein the stop assembly also includes a counting mechanism and wherein the step of actuating the stop assembly includes actuating the counting mechanism to count the predetermined number of rotations.

14. The method according to claim 13 wherein the actuation mechanism includes a hub member attached to the spool for rotation with the spool and an inertia member releasably connected to the hub member in a first orientation relative to the hub member, the inertia member being released from the hub member for limited rotational movement to a second orientation relative to the hub member upon actuation of the pretensioner, the step of actuating the stop assembly including rotating the inertia member relative to the hub member into the second orientation.

15. The method according to claim 11 wherein the stop assembly limits twisting of the torsion bar.

Assignees

• Trw Vehicle Safety Systems

Inventors

• Franz Scott M
• Siev Chhay S

Classifications

• B60R22/4633

  Linear actuators, e.g. comprising a piston moving along reel axis and rotating along its own axis · CPC title

• B60R22/38 Primary

  responsive only to belt movement · CPC title

• B60R22/405

  responsive to belt movement and vehicle movement · CPC title

• B60R2022/287

  of torsion rods or tubes · CPC title

• B60R2022/385

  with adjustable sensitivity · CPC title