Land vehicles – Wheeled – Attachment
Patent
1998-03-30
2000-09-05
English, Peter C.
Land vehicles
Wheeled
Attachment
297480, 60635, B60R 2246
Patent
active
061131458
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to pretensioners for vehicle safety restraint devices and particularly to a locking and sealing means therefor.
BACKGROUND OF THE INVENTION
Pretensioners reduce the slack in a belt restraint system by rapidly drawing in a length of belt webbing in the first milliseconds of a crash situation, to secure the vehicle occupant in the correct position in the seat and reduce the residual forward momentum of the occupant traditionally resulting from slack in the belt webbing due to relatively loose winding on the retractor, to bulky clothing and/or to belt webbing stretch.
One example of a known pretensioner uses pyrotechnic means to generate gas to move a piston attached to a cable to tighten the belt by rapidly rewinding the retractor or by pulling back the buckle attachment.
There is a problem with such a pyrotechnic pretensioner in sealing the space between the moving piston and the walls of the cylinder within which it moves, against the large force of the gas generated. Known sealing systems are bulky and difficult to assemble accurately with attendant higher costs of manufacture.
The present invention provides an improved pretensioner.
SUMMARY OF THE INVENTION
According to the present invention there is provided a pyrotechnic pretensioner for a vehicle safety restrain comprising: cable; cable and tension the webbing; cylinder in a webbing tensioning direction and operates to engage the piston with the cylinder in response to movement of the cable in a webbing loosening direction, the piston locking means and the piston has a circumferential radially extending resilient sealing member for cooperating with the tooth profile to seal the spaces between teeth.
Preferably the piston has two radially extending sealing members, e.g. sealing rings such as O-rings, spaced apart by an odd integral number of half pitches of the cylinder teeth.
According to a preferred embodiment the piston is die cast directly onto the cable, e.g. by a pressure die casting process.
The cylinder teeth are preferably of saw tooth profile but may be semi-circular in profile. The farce reservoir is preferably a pyrotechnic gas generator.
It will thus be seen that a pretensioner can be constructed with a sealing arrangement according to the present invention which has many advantages over known devices.
For a better understanding of the present invention and to snow row the same may be carried into effect, reference will now be made to the accompanying drawings.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a cross-sectional view of a pyrotechnic buckle pretensioner constructed in accordance with the invention.
FIG. 2 is a large scale view of part of FIG. 1.
FIG. 3 is a partial view of the pretensioner showing an alternate embodiment.
DETAILED DESCRIPTION OF DRAWINGS
In FIG. 1 a safety restraint belt buckle 1 is shown at the end of a cable 3 with plastic coating 2. The cable 3, is rivetted at 4 to the buckle housing 1 and passes round a mounting bracket 6 and through a seal 5 into a pretensioner tube 8 where it is die cast to a pretensioner piston 7.
The mounting bracket 6 may be a pulley or a simple channel.
A gas generator housing 9 is attached to the side of the pretensioner tube 8 with which it communicates to enable gas to push the piston along the tube in the direction of arrow A. The gas generator is activated by an associated electrical pulse generating means 9a.
The inside of the tube 8 has a sawtooth form and the piston 7 is associated with an elliptical locking device 10 which moves freely in the pretensioning phase, in the direction of arrow A, since the edges of the elliptical device 10 ride over the long sides of the saw teeth. However, once the pretensioning operation is complete and the vehicle occupant momentum puts force on the buckle and thus on the piston in the opposite direction, then the edges of the elliptical device engage in the teeth in the tube and lock the piston against the reverse movement, i.e. in the direction reverse to arrow A.
The piston 7 has tw
REFERENCES:
patent: 4508287 (1985-04-01), Nilsson
patent: 5480190 (1996-01-01), Fohl
Breed Automotive Technology Inc.
English Peter C.
Seitzman Markell
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