Land vehicles – Wheeled – Attachment
Reexamination Certificate
2002-05-30
2004-11-02
Ilan, Ruth (Department: 3616)
Land vehicles
Wheeled
Attachment
C280S735000
Reexamination Certificate
active
06811183
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a device for venting an airbag, especially for venting an airbag in an active passenger restraint system of a vehicle.
BACKGROUND OF THE INVENTION
In order to reduce the risks of injury for the vehicle passengers in case of a road accident, modem vehicles are increasingly often equipped with an active passenger restraint system. Such an active passenger restraint system comprises in general one or more airbags which are in a flash inflated in case of an impact of the vehicle and which take up the energy released by the passenger during the impact.
As an airbag, such as a frontal airbag, exits the dashboard or the steering wheel mounted module at very high speeds (200 to 300 km/h), for avoiding injuries of the passenger by the released airbag it is advantageous to interrupt or control the complete inflating or unfolding of the airbag as soon as the passenger has sufficiently immerged in the airbag and a sufficient pressure has built up in the airbag in order to be able to securely take up the energy of the passenger. As the time when the passenger has sufficiently immerged in the airbag very strongly depends on several parameters, such as the seat position of the passenger at the time of the accident, the interruption of the inflating process of the airbag can become necessary in any stadium of its release operation.
As an inflating device functioning on the basis of pyrotechnics, a so-called inflator, cannot be interrupted in its function at any arbitrary time due to the system, a passenger restraint system consequently has to comprise a device for purposefully venting the airbag for interrupting the release operation in a controlled manner. Such a device has to permit to deflate the gas blown into the airbag by the inflator at any arbitrary time and to avoid a further inflation of the airbag.
From WO-A-98/01323, a device is known in which the gas bag comprises a ventilation opening which Is closed at a frangible line or predetermined breaking line. The predetermined breaking line is designed to remain intact below a predetermined nominal pressure within the airbag and to automatically break open above the nominal pressure under the influence of the pressure. Such a predetermined breaking line is generally achieved by a thoroughly and technically precisely dimensioned weakening of the material employed. This weakening of the material can e.g. be effected by a perforation in which small incisions are disposed along the provided predetermined breaking line. In another embodiment, the predetermined breaking line is formed when closing the airbag by means of a seam produced by sewing, the thread used for sewing and the distance between the stitches being exactly mated to the demands of the airbag release. Alternatively, the airbag hull can also be closed by sealing, e.g. by ultrasonic sealing, with exactly adapted sealing patterns. In this case, the sealing seam is the predetermined breaking line.
From the EP-A-638 466, an airbag is known in which certain areas of the airbag material are slightly permeable to gas at a normal working pressure due to a purposeful weakening of the airbag material. These areas, the so-called dynamic vents, are for example formed by perforating the airbag material by means of a laser or by means of a needle punch. At a critical gas pressure above the normal working pressure, the gas escaping from the dynamic vents causes a melting or burning of the airbag material.
The problem with such predetermined breaking lines or dynamic vents, respectively, which automatically break open under the airbag pressure, is that due to the manufacturing tolerances an exact adjustment of the required nominal pressure at which the predetermined breaking line or the dynamic vent, respectively, breaks open is hardly possible.
A solution of this problem is to be found in controlled venting devices.
The document U.S. Pat. No. 5,899,494, for example, describes an airbag device in which the inflating device is connected with the airbag by means of a distributor. The inflating device and the distributor are arranged in a housing which is gas-tightly sealed at one side of the airbag. The distributor as well as the housing are provided with a deflagration device which can burn a vent into the distributor or the housing, respectively, within a very short time after activation by an electrical pulse.
A controlled venting device is also described in the document GB-A-2 306 409. In this device, the airbag comprises a valve which is opened upon control by an electric signal. In a first embodiment, the valve comprises an expanded opening in the airbag material which is sealed by a sealing disc made of a meltable material. The disc comprises a predetermined breaking point with a reduced thickness to which a pyrotechnic charge is assigned at a distance. If the pyrotechnic charge is ignited by an electric signal, the same generates a flame which burns through the disc material in the region of the predetermined breaking point. Subsequently, the sealing disc further cracks open along the predetermined breaking point such that a fairly large vent is formed.
In another embodiment of the device from the GB-A-2 306 409, the airbag has a two-layer design. In the region of the valve, one of the layers comprises an opening which is sealed by a membrane formed by the second layer. A housing mounted at the airbag contains an ignitable pyrotechnic charge and a piston disposed between the pyrotechnic charge and the membrane and being provided with a cutting blade. By igniting the pyrotechnic charge, the piston is driven into the direction of the membrane, the cutting blade cutting the membrane, such that a vent is cut into the airbag.
SUMMARY OF THE INVENTION
Consequently, it is the object of the present invention to propose another device for purposefully venting a gas bag.
This object is solved according to the invention by a device for venting a gas bag made of a textile material, especially an airbag, with at least one ignitable pyrotechnic charge which is associated to the gas bag in a region such that, when the pyrotechnic charge is ignited, at least one thread of the textile material is destroyed in the region of the pyrotechnic charge. The pyrotechnic charge is in this case arranged directly at or in the textile material, so that, when the pyrotechnic charge is ignited, at least one thread of the textile material is directly destroyed by the explosion of the pyrotechnic charge. By the destruction of at least one thread of the textile material, commonly a woven or knitted fabric, the textile material can crack open at the respective site. Under the influence of the gas pressure in the interior of the gas bag, the textile material cracks further open at the respective site, so that a fairly large vent opening is formed through which the gas flowing into the gas bag can escape. Thereby, a further inflation of the airbag is effectively suppressed. It should be noted that the thread to be destroyed by the explosion is a “normal” thread of the textile material, e.g. a weaving or a knitting thread of the airbag, as well as a seam thread of a fastening seam formed by an appropriate production technique in the material of the gas bag, which thread is provided especially for this purpose. As soon as the seam fiber is broken at at least one site, the fastening seam can be opened without any expenditure of force if it is appropriately designed by special weaving or knitting techniques, respectively, and so the vent opening can be uncovered. It should further be noted that in case of a corresponding expansion of the pyrotechnic charge several threads of the textile material can be destroyed simultaneously, so that the vent opening quickly reaches the desired size.
In contrast to the presently known devices, the device according to the invention is actively triggered by igniting the pyrotechnic charge. This means that the venting operation can be triggered at any time in an exactly controlled manner. The triggering of the venting device can, for examp
Meyer Michael
Petri Volker
Rudolf Harald
Serban Bogdan
Witte Michel
I.E.E. International Electronics & Engineering S.ar.l.
Ilan Ruth
McCormick Paulding & Huber LLP
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