Land vehicles – Wheeled – Attachment
Reexamination Certificate
1998-09-18
2001-03-20
Swann, J. J. (Department: 3611)
Land vehicles
Wheeled
Attachment
C280S750000
Reexamination Certificate
active
06203055
ABSTRACT:
The present invention relates to a safety device for an airbag-system.
It is known from the Dutch newspaper
De Volkskrant
of Oct. 3, 1995, that a good 25 years ago already an airbag was designed which would instantly pop out from the middle of the steering wheel of a motorcar the moment sensors in the motorcar perceive a collision. Such airbags prevent serious injuries to occupants of the motorcar, especially if they were not wearing a safety belt at the time of the collision. Actually, airbags are still subject to constant development, taking better into account the kind of collision and the situation in which the occupants of the motorcar find themselves at the moment of the collision and inflation of the airbag.
Practical experience has shown, however, that after an accident or collision one may face the problem that the airbag is not yet activated and assistance to the occupants takes place while the risk exists that the airbag will still inflate. This is a danger for both the helpers and occupants needing assistance.
To avoid this problem, an airbag retention device has been proposed in U.S. Pat. No. 5,277,440. From this document, it is known to apply a generally round sheet of flexible material having a diameter slightly larger than the steering wheel or at least approximately the same size as the steering wheel. The device also comprises a plurality of criss-crossed strips, preferably of a reinforced nylon material, each attached to one another at a central point. Each of the strips terminates in a closed loop and a cord or drawstring passes through each of the closed loops of each of the strips. In such a device, the pressure build-up during inflation of the airbag is enormous and no guarantee exists that the cord or drawstring will be able to withstand the pressure build-up.
It is therefore preferred in the known safety device to have the drawstrings pass through each loop twice, i.e. twice around the periphery of the strips to provide additional restraining strength. When the safety device is placed over the steering wheel, the drawstring or cord may be pulled tightly to pull the end loops of each of the strips towards to each other so as to form an opening having a smaller diameter than the diameter of the steering wheel, and in order to provide a tight fit of the restraining fabric around the steering wheel. However, when the drawstring is tightened, the opening is only slightly smaller than the diameter of the steering wheel.
This aspect in combination with the huge pressure build-up during inflation of the airbag renders this system unreliable when repeatedly used or even when used only once in retaining an inflating airbag.
It is the object of the invention therefore to provide a reliable safety device for an airbag-system which can be safely used on any size steering wheel and repeatedly.
To this end, the safety device according to the invention is characterized in that a space of 10 to 15 cm is left between the steering wheel and the fabric fitted around it. Contrary to any teaching in the prior art, every tight fit of the fabric is therewith avoided, and in the case of untimely inflation this leaves the airbag sufficient space for a controlled pressure build-up.
The fabric can be secured particularly effectively around the steering wheel if the cord or the ribbon for gathering the outer edge is connected at a first extremity with the outer edge of the fabric and is provided at a second extremity with a hook means for the detachable connection of the second extremity to a permanent point. The chosen hook means may, for instance, be a securable carabine hook such as the clog screwgate kind, which has a tensile strength of about 2400 kg.
In a first embodiment of the safety device according to the invention at least part of the fabric takes the form of a meshed net. The dimensions of the net may vary. However about 9×9 cm has been shown to be a preferred mesh size. This provides the airbag with enough space to allow it to still extend somewhat through the mesh of the net, so that tensions of too great a force in the cords of the net are avoided.
The net can be made sufficiently strong by using aramide cords having a diameter of about 7 to 8 mm. Of course, other cords providing sufficient tensile strength are also possible, but especially the use of aramide provides a lightweight, yet strong product which is quite suited for the intended safety function. Moreover, this function is maintained over an extensive temperature range.
In another embodiment of the safety device according to the invention at least part of the fabric is closely woven and is provided with one or more openings near the outer edge. In general, using a closely woven fabric affords the advantage of halving the sound pressure produced by an activated airbag. The sound pressure of an exploding airbag ranges from 120-150 dB. In addition, very adequate protection is provided against dust production caused by the exploding airbag, which would otherwise cause irritation of the eyes. One may choose, for instance, to make the fabric from the fire-resistant Nomex III® material made by Ten Cate Protect B.V., Nijverdal, or from metal. Further, when using a fabric, it is desirable to reinforce the openings which serve to limit the pressure build-up when the airbag is activated, by means of, preferably metal rings. A very favourable embodiment is characterized in that at least part of the fabric is formed from closely woven aramide fibres such as, for instance, Kevlar®. Apart from the above-mentioned advantages for using aramide there is the further advantage that the fabric—though closely woven—is gas-permeable, affording better control of the pressure build-up from the airbag.
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patent: 29508472 U (1995-09-01), None
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Dunn David R.
Martimon B.V.
Myers Jeffrey D.
Swann J. J.
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