Seat belt retractor

Details Seat belt retractor Seat belt retractor

2000-04-04

2001-11-27

Jillions, John M. (Department: 3653)

Winding, tensioning, or guiding

Reeling device

With spring motor

Reexamination Certificate

active

06322017

ABSTRACT:

FIELD OF INVENTION
The present invention relates to a safety restraint for use in a vehicle and particularly to a retractor for a seat belt.
BACKGROUND OF THE INVENTION
Modern seat belts comprise a length of webbing arranged to pass diagonally across the torso, and generally horizontally across the hip region of the vehicle occupant (so-called lap portion of the belt). This is known as a three-point belt system. One end of the belt webbing is firmly attached to a structural part of the vehicle such as the floor, and the other end is attached to the spool of a retractor which itself is firmly attached to a structural part of the vehicle, usually the side B-pillar. Between the retractor and the fixed point, a fastening element such as a metal tongue is fixed to the belt with which it can be fastened into a buckle which itself is attached to fixed part of the vehicle on the other side of the occupant seat to the retractor.
SUMMARY OF THE INVENTION
The seat belt retractor has a clock spring, which automatically keeps any slack in the belt wound onto the spool and thus keeps a resilient tension in the belt. The clock spring allows payout of webbing under the influence of relatively gentle forwardly directed inertia of the vehicle occupant, for example to allow for normal movement of the vehicle occupant such as occurs when he reaches forward to activate car controls, or access glove compartments or door pockets.
In the event of a crash, the sudden high forward momentum of the vehicle occupant activates a crash sensor which locks the spool against rotation and restricts forward motion of the vehicle occupant to prevent him colliding with and being injured by internal fixtures of the vehicle such as the steering wheel, dashboard or windshield.
However in high velocity crashes, the sudden locking of the seat belt can itself cause injury to the vehicle occupant due to the sudden impact of the torso with the belt webbing.
In recent years, load-limiting effects have been introduced into seat belt systems so as to allow a limited and controlled forward motion of the vehicle occupant after the retractor has locked. This decreases the forces exerted by the belt on the vehicle occupant's torso.
Load limiting proposals are arrangements familiar to those skilled in the art, including arrangements whereby deformable torsion bars are placed within the retractor spool in the force path between the spool locking mechanism and the belt webbing.
However, it has been found that as it twists, the torsion bar lengthens. Thus the locking teeth engaging the spool can move away from the spool causing the teeth to disengage from the lockbar and thus causing the retractor to unlock at high loads. Evidently this is extremely dangerous.
The present invention provides an improved load limiting arrangement for seat belt retractors using torsion bars.
According to the present invention, there is provided a retractor for a seat belt comprising a spool, rotatable about its axis, for receiving seat belt webbing, a locking means for preventing rotation of the spool during a crash to prevent webbing pay-out, and load limiting means comprising a torsion bar extending through the spool and connected in the force path between the locking means and the webbing, one end of the torsion bar being attached to the spool, and the opposite end of the torsion bar being attached to a toothed wheel, wherein said opposite end of the torsion bar is connected to the toothed wheel in an axially adjustable manner.
According to a preferred embodiment, the torsion bar and the wheel are connected by cooperating members in such a way that axial expansion of the bar is automatically compensated. The cooperating member may be teeth and splines.
The splines are preferably spiral formed and may be of screw threaded form or helical.
Preferably the angle of the helix is selected to compensate for friction between the bar and the spool splines.


REFERENCES:
patent: 3970265 (1976-07-01), Kopke et al.
patent: 4323205 (1982-04-01), Tsuge et al.
patent: 0297537 (1989-01-01), None
patent: 2347899 (2000-09-01), None

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