Seat belt pretensioner

Details Seat belt pretensioner Seat belt pretensioner

2001-02-15

2002-09-17

Jillions, John M. (Department: 3654)

Winding, tensioning, or guiding

Reeling device

With spring motor

C280S806000, C060S632000

Reexamination Certificate

active

06450435

ABSTRACT:

FIELD OF THE INVENTION
The invention relates to a seat belt pretensioner.
DISCUSSION OF THE PRIOR ART
U.S. Pat. No. 5,842,344 teaches a seat belt pretensioner with a piston activated by a pyrotechnic generated propellant gas in a linear direction in a guide arrangement. In this device the propellant gas acts upon the piston in a pressure chamber. To avoid excess pressure in the pressure chamber, the known device has a blowout patch on a front wall of the piston. The blowout patch has points of intended weakness, via which an evacuation passageway is created under excess pressure in the pressure chamber. In a second embodiment, the front wall of the piston has a small calibrated discharge opening to facilitate the desired pressure reduction. In a third embodiment, the front wall of the piston has a tear-off part which, during the return stroke of the piston at the moment of load limitation, is removed from an evacuation passageway.
SUMMARY OF THE INVENTION
There is provided by the present invention a seat belt pretensioner activated by opening a gas flow port with a controlled time delay, such that after the tensioning stroke of the piston sufficient time remains for a blocking pawl to engage with a belt reel in a blocking position. A weak point, in the form of a plastic deformable membrane, provides for pressure reduction in the pressure chamber via the gas flow port. Deformation of the membrane to such an extent that a gas flow port is created takes time. During this time a main blocking device, in particular a pawl supported on the retractor frame, can engage the belt reel in a blocking position, in particular with blocking teeth on the belt reel. This ensures a secure blocking of the belt reel. In addition it ensures that a load-limiter can come into effect. As a result, excess forces exerted by the secured seat belt on the vehicle occupant are avoided during the forward displacement of the vehicle occupant.


REFERENCES:
patent: 4372501 (1983-02-01), Inukai
patent: 5842344 (1998-12-01), Schmid
patent: 6155512 (2000-12-01), Specht et al.
patent: 6299090 (2001-10-01), Specht et al.
patent: 29520307 (1996-04-01), None
patent: 19837927 (2000-03-01), None
patent: 19927270 (2001-01-01), None
patent: 19939499 (2001-02-01), None

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