Seat belt retractor

Details Seat belt retractor Seat belt retractor

1999-09-02

2001-05-01

Nguyen, John Q. (Department: 3653)

Winding, tensioning, or guiding

Reeling device

With spring motor

C280S806000, C280S807000

Reexamination Certificate

active

06224008

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a retractor for a seat belt retractor, and particularly to a seat belt retractor having a pretensioner.
BACKGROUND OF THE INVENTION
Pretensioners are used in modern vehicle seat belt systems to rapidly draw in a length of belt webbing in the event of a crash and take up slack in the belt. This pretensioning action minimizes forward movement of the restrained vehicle occupant and more correctly positions the vehicle occupant in the vehicle seat to maximize the effect of a secondary safety restraint, such as an airbag.
Vehicle manufacturers prefer pretensioners to be as small as possible and this has led, in recent years, to the development of various forms of so-called compact pretensioners. In general a compact pretensioner works without the need for a clutch mechanism to connect it to the retractor.
In addition, modern seat belt systems often incorporate load limiting features to reduce the detrimental effect of the force exerted on the vehicle occupant by the restraining seat belt itself. It is desirable to lock the seat belt and pretension it at the very beginning of a crash, as the crash force is rising, but to then allow a small amount of payout of the seat belt, at a particular controlled load at the peak of the crash force, to reduce the peak load felt by the vehicle occupant.
SUMMARY OF THE INVENTION
The present invention provides an improved pretensioner for a seat belt retractor, which is suitable for seat belt retractors with load limiting features.
More particularly, the present invention can provide a venting system for a compact pretensioner.
According to the present invention there is provided a seat belt retractor comprising: a spool having seat belt webbing wound thereupon and being mounted for rotation in a frame; a toothed ratchet wheel connected to the spool to rotate therewith; a crash sensor; a locking pawl arranged to be pivotable from a first position in which it is spaced from the ratchet wheel to a second position in which it engages with the ratchet wheel to lock the spool against rotation, in response to activation of the crash sensor; a pretensioner arranged to be responsive to the crash sensor to rapidly rewind webbing onto the spool; a venting arrangement for the pretensioner, the venting arrangement comprising: a chamber having an inside side wall and an inside wall; a vent hole formed in the side of the chamber; a seal for the vent hole; an axially slidable member mounted in the chamber and biased away from one end of the chamber by a resilient member; the slidable member being operatively connected to the locking pawl, so that the member slides in the chamber, against the resilient bias, when the locking pawl pivots from the first to the second position and; at least two spaced seals between the slidable member and the inside wall of the chamber arranged during normal operation of the retractor, when the locking pawl is in the first position to lie one on each side of the vent hole and to lie both on the same side of the vent hole when the locking pawl is in the second position.
Preferably the chamber takes a cylindrical form as the slidable member is a piston. The vent hole seal may be pressure or heat rupturable. The resilient member may be a compression coil spring connected between an end wall of the chamber and fitting in a recess in one end of the piston.
The chamber may be located within housing and seals provided between the outside walls of the chamber and the inside walls of the housing. An opening in the side wall of the housing is preferably aligned with the vent hole in the chamber wall and is connected to receive gas under pressure, from the pretensioner. In one embodiment this opening in the housing tapers in an inward direction so as to concentrate the pressure on the vent hole seal.
In one embodiment the slidable piston is connected mechanically, e.g. by a rigid shaft, but this connection could be electrical or electronic.


REFERENCES:
patent: 4372501 (1983-02-01), Inukai
patent: 5397075 (1995-03-01), Behr
patent: 0673811A (1995-09-01), None
patent: 2332397A (1999-06-01), None
patent: 10067300 (1998-03-01), None

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