Belt tensioner for a vehicle occupant restraint system

Details Belt tensioner for a vehicle occupant restraint system Belt tensioner for a vehicle occupant restraint system

1998-05-15

2001-06-26

DePumpo, Daniel G. (Department: 3611)

Land vehicles

Wheeled

Attachment

C297S480000

Reexamination Certificate

active

06250682

ABSTRACT:

TECHNICAL FIELD
The invention relates to a belt tensioner, in particular a buckle tensioner for a vehicle occupant restraint system.
BACKGROUND OF THE INVENTION
In the case of restraint, hot compressed gas, released from the gas generator, flows into the working space in order to displace the piston part. The traction transfer means, normally a traction cable, is at the same time exposed to high temperatures through direct contact with the hot compressed gas and can thereby be damaged. In buckle tensioners, in addition to the temperature load there is also a high traction load of the traction transfer means, which is exerted by the vehicle occupant moving forward. The traction transfer means is hitherto overdimensioned in order to be able to withstand the loads, which, however, has a negative influence on the manufacturing costs of the belt tensioner and also its weight.
BRIEF SUMMARY OF THE INVENTION
The invention provides a belt tensioner in which the traction transfer means is subjected to smaller thermal loads than in known belt tensioners. The belt tensioner according to the invention comprises a housing, a gas generator for generating compressed gas in the case of restraint, a working space into which the compressed gas flows, a piston part displaceable by the compressed gas and a belt engaging means. The belt engaging means is in force-transferring relationship with the fastened belt. The tensioner further comprises a traction transfer means extending through the working space, which traction transfer means connects the belt engaging means with the piston part, and a sheathing for the traction transfer means which at least partially covers the traction transfer means within the working space. The sheathing is of a material having a temperature stability with respect to the hot compressed gas.
Although it is known to cover the traction transfer means in the form of a cable by a plastic tube for sealing and visual purposes, this tube, however, does usually not extend into the working space and is not of a material featuring high temperature stability.
Preferably, the traction transfer means is a traction cable. By using a traction cable, there exists the problem that this can only be sealed with difficulty to the opening provided in the end wall of the housing, through which it extends. This is due to the outer surface of the traction cable not being of cylindrical shape. With the use of a sheathing, the outer contour can be adapted exactly to the contour of the opening, so that the sheathing has a dual function, serving also for the better sealing of the working space. The hitherto provided expensive seals can thereby be largely eliminated, whereby the belt tensioner becomes cheaper.
The sheathing can be a shrinkable tube formed of a material having temperature stability, a layer extruded onto the traction cable, or a sleeve. The sleeve can be pressed onto the traction transfer means or can also be connected with the piston part.
For better sealing and for better guidance of the traction transfer means, in a preferred embodiment a guide is provided projecting into the working space, at which guide the outer surface of the casing, constructed as a sliding surface, abuts.


REFERENCES:
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patent: 4767161 (1988-08-01), Sedlmayr et al.
patent: 5350194 (1994-09-01), Fohl
patent: 5667246 (1997-09-01), Miller, III
patent: 5927756 (1999-07-01), Wier
patent: 3407379 (1986-06-01), None
patent: 296 09 054 U (1996-10-01), None
patent: 0093237 (1983-02-01), None
patent: 0186880 (1985-12-01), None
patent: 0558963 (1993-02-01), None

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