Land vehicles – Wheeled – Attachment
Reexamination Certificate
1998-11-20
2001-04-17
Johnson, Brian L. (Department: 3618)
Land vehicles
Wheeled
Attachment
Reexamination Certificate
active
06217064
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a gas generator with a housing, an outflow opening in the housing via which gas can emerge, and a bursting membrane which closes the outflow opening in the non-activated state of the gas generator and which is destroyed on activation, the bursting membrane having an outer edge at which it is permanently fastened to a wall which defines at least one axial section of the outflow opening.
Such a gas generator is known from the U.S. Pat. No. 3,721,456 to McDonald. This generic tubular gas generator has a housing constructed in several parts. The housing consists of a tubular section and of an expensively manufactured end wall screwed therein, which has a narrowing outflow opening. On the inner face, a membrane is fastened to the end wall upstream of the outflow opening. The inner face of the end wall continues into the outflow opening in a 90° angle. The membrane is fastened to the inner face of the end wall. When a predefined internal pressure is exceeded in the housing, the bursting membrane tears into individual pieces. Some membrane segments which are formed thereby are entrained with the gas stream and can arrive into the adjoining gas bag, where they can destroy the gas bag wall because of their high temperature. In order to prevent an entrainment of such hot membrane segments into the gas bag, in the prior art filters are always provided after the outflow opening, which hold back the membrane segments.
SUMMARY OF THE INVENTION
The invention provides a more simply constructed gas generator, in which the danger of the formation of membrane segments entrained with the gas stream can be ruled out.
This is achieved in a gas generator of the type initially mentioned in that the wall is rounded or extends inwards and obliquely in the outflow direction downstream immediately after the fastening region. Surprisingly, it has been found that through this step, no membrane segments are produced which are entrained with the gas stream. Rather, even after the destruction of the membrane, the membrane segments are held in the fastening region against the wall. In the prior art, it is obviously principally the notch effect, i.e. a too sharp-edged transition between the inner face of the end wall and the inner face of the outflow opening, which transition leads to the shearing off or to too intensive a bending of the membrane on its destruction. Through this simple step according to the invention, the filters, hitherto always necessary, become superfluous.
According to a further embodiment, the inner face of the wall is shaped in such a manner that the bursting membrane does not come to lie against the wall shortly before reaching the internal pressure in the housing leading to its destruction. Through this feature, the membrane is prevented from tearing in an undefined manner. With the presence of a gas pressure in the housing, the membrane is curved outwards in a calotte shape. The greatest tension in the membrane will occur here at the region which is shaped furthest outwards (crown region). Starting from this region, the destruction of the bursting membrane begins after the bursting pressure has been reached. Hence, a star-shaped tear pattern is produced with relatively short membrane segments of equal length. If the membrane were to be able to come to lie against the inner face of the wall, the tear of the membrane would start from a different point and membrane segments of differing length would result. The destruction of the membrane would thereby be able to be predetermined less exactly than is the case through the provision of the above-mentioned step. In addition, with the membrane lying against the wall, the bursting pressure would increase, which would result in a greater stressing of the housing.
Preferably, the inner face of the wall is shaped in such a manner that the membrane segments come to lie against the wall after destruction. Thereby, a tearing off of segment pieces by the gas stream is to be prevented. The membrane segments come to lie against the inner face of the wall and the force applied onto them by the impinging flow is introduced directly into the wall.
Preferably, the wall is part of a nozzle or throttle immediately adjoining the bursting membrane in the direction of flow. If a throttle is provided, the flow channel which is defined by the outflow opening has a concave section. It has been found that the membrane segments can very well come to lie against a concave section without pieces being torn off from them.
The concave section is, in addition, preferably dome-shaped.
If a bevelled, i.e. conical section follows immediately after the fastening section, then this conical section is inclined at an angle of 30° to 45° with respect to a plane which is defined by the membrane when not acted upon by pressure.
The bevelled section continues from a rounded section into the concave section, so that marked shoulders or bends on the inner face are prevented. Bends or shoulders do not, however, automatically have to lead to the tearing off of the membrane segments and can certainly be provided.
However, continuous transitions between differently shaped sections are preferably to be provided.
A further step, in order to prevent the tearing off of membrane segments or of part of membrane segments consists in that owing to the length of the outflow channel, a protruding of membrane segments out from the channel is ruled out. The protruding section would in fact be greatly stressed by the compressed gas. This would lead to the tearing off of the section of the membrane segments.
If the outflow channel is provided with a cylindrical section which defines the smallest flow cross-section, then it has proved to be advantageous if the membrane segments can not even project into the section with the smallest flow cross-section.
REFERENCES:
patent: 3709239 (1973-01-01), Morck, Jr.
patent: 3721456 (1973-03-01), McDonald
patent: 4505289 (1985-03-01), Wilson
patent: 4913184 (1990-04-01), Fallon
patent: 5462307 (1995-10-01), Webber et al.
patent: 5582426 (1996-12-01), O'Loughlin et al.
patent: 5615912 (1997-04-01), O'Laughlin et al.
patent: 5690357 (1997-11-01), Cuevas
patent: 19644258 (1997-04-01), None
patent: 0733519 (1996-09-01), None
Schwuchow Karsten
Seidl Johann
Tasche Michael
Woitge Wolf-Dieter
Fischmann Bryan
Johnson Brian L.
Tarolli, Sundheim, Covell Tummino & Szabo L.L.P.
TRW Airbag Systems GmbH & Co. KG
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