Land vehicles – Wheeled – Attachment
Patent
1995-04-13
1997-09-02
Culbreth, Eric D.
Land vehicles
Wheeled
Attachment
280739, B60R 2116, B60R 2128
Patent
active
056623542
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a gas bag for a restraining system in vehicles, comprising a wall of a plurality of sewn together parts of uncoated fabric, of which the fabric part facing a vehicle occupant possesses a substantially lower permeability to gas than at least one fabric part facing away from the vehicle occupant. Furthermore, the invention relates to a fabric for the production of such a gas bag.
The protective action able to be produced by a gas bag is particularly dependent on its hardness in the inflated state. A soft gas bag will minimize the risk of injury as long as it is not hit through in a hard front-on collision or on the impact of a heavy passenger. Since when a passenger plunges into a gas bag the volume thereof will be reduced, there is also an increase in the interior pressure with the result that simultaneously there is an increase in the hardness of the gas bag. The desired effect is however largely overridden in the case of a conventional gas bag because the increased interior gage pressure involves the flow of gas through the escape holes or the gas-permeable wall parts of the gas bag. In accordance with ruling ideas in the art, the flow of gas through an escape opening or through a gas-permeable fabric is essentially a linear function of the internal gage pressure.
The invention is intended to provide a gas bag for a restraining system in vehicle, whose hardness is automatically regulated and within a wide range of relevant parameters, such as intensity of impact, weight of the vehicle occupant or the temperature-dependent generator performance, possesses the necessary value for an optimum protective action. This self-regulating property of the gas bag is achieved by control of the gas permeability of the wall thereof in a manner dependent on the internal gage pressure. The gas permeability curve, which represents the gas flow through the overall wall of the gas bag as a function of the internal gage pressure, must substantially depart from conventional notions, in accordance with which gas permeability increases approximately linearly with the internal gage pressure. In fact gas permeability must even decrease after reaching a maximum at a level of about 20 kPa. In accordance with the invention gas permeability of the overall wall of the gas bag has to increase, as far as a gage pressure of approximately 10 kPa with an increasing pressure, to a value between approximately 0.4 and approximately 1.0 m.sup.3 /s. Between gage pressure levels of approximately 10 kPa and approximately 20 kPa gas permeability will further increase, will reach a maximum and will then decrease again. Above a gage pressure of approximately 20 kPa to at least approximately 40 kPa gas permeability should not substantially increase, and should even preferably exhibit a clearly decreasing tendency. Owing to this form of the gas permeability curve the gas bag will be relatively soft in the initial phase of the build up of a gage pressure so that in the case of a light impact the danger of injury will be minimized. At high gage pressure levels, for example when a vehicle occupant does not have his seat belt fastened, there will be a hard impact. Since in this range the gas permeability of the gas bag wall will not further increase but will even preferably decrease, the gas bag will now possess the necessary substantial hardness.
In accordance with an advantageous further development of the invention all fabric parts of the gas bag wall consist of a fabric type which is the same as regards fiber density and filament yarn. The use of the same type of fabric for the fabric parts with different gas permeability is a great advantage, because all fabric parts will possess the same structural strength and the seam connections between the fabric part will be free of problems. The fact that for fabric parts with substantially different gas permeability values the same type of fabric may be suitable is a further notion of the invention. On the one hand it has been discovered that the gas permeability of a given fabric can
REFERENCES:
patent: 3937488 (1976-02-01), Wilson et al.
patent: 5093163 (1992-03-01), Krummheuer et al.
patent: 5518269 (1996-05-01), Storey et al.
Culbreth Eric D.
TRW (Repa) GmbH
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