Land vehicles – Wheeled – Attachment
Reexamination Certificate
2002-03-08
2003-12-09
Johnson, Brian L. (Department: 3618)
Land vehicles
Wheeled
Attachment
C280S728100
Reexamination Certificate
active
06659501
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a textile formed part that is manufactured by a method comprising fusing a polymer material to a textile fabric material to form a composite which is then thermally formed in a three-dimensional shape. The textile formed part can be used in a gas bag for vehicle applications or in clothing.
Occupant restraint systems with gas bags, frequently also referred to as airbags, which are automatically inflated in the case of a serious accident are nowadays installed in a plurality of passenger cars both on the driver's side and on the passenger's side in order to possibly avoid, in the case of a serious frontal impact of the vehicle, potential head and chest injuries of the vehicle occupants which are seated in the front. Such systems which essentially consist of a mostly pyrotechnical gas generator and a gas bag as well as of the associated control electronics are increasingly employed in the lateral area of passenger cars in order to dampen and distribute the forces acting upon the vehicle in the case of a side impact over a larger area and thus decrease the injury hazard for the vehicle occupant who is seated on the impact side. Such laterally arranged impact protection systems with gas bag, which are also referred to as sidebags, are, for example, accommodated in the vehicle doors or in the backrests.
On the basis of the predominantly positive experience gained with such impact protection systems which comprise a gas bag the trend exists to employ such systems on a wider scale in trucks and buses as well.
Depending on the task which an occupant restraint system of the initially mentioned type is to fulfill, the gas bag in its inflated state must have a precisely defined shape in order to achieve the optimum effect. The so-called driver airbags in their inflated state are, for example, approximately balloon-shaped, while the so-called passenger airbags in their inflated state are approximately cushion-shaped. Side airbags, in turn, frequently still have intricate shapes in order to be able to comply with the requirements imposed on them.
In addition, gas bags must fulfill two contradictory requirements: On the one hand they must be inflatable as rapidly as possible when required; on the other hand they have to provide as large a distance as possible between the vehicle occupant to be protected and the object with which the vehicle occupant must not collide. While the first requirement calls for a small gas bag volume, a relatively large gas bag volume is the result of the second requirement. The existence of impact protection systems with a gas bag, however, is only justified if their protective effect is as good as possible so that nowadays large gas bag volumes are preferred in order to achieve an optimum protective effect.
Conventional gas bags consist of two or more individual textile parts which are cut from textile flat material and subsequently sewn together. Accordingly, two circularly made-up two-dimensional textile parts are generally sewn together for a driver's airbag. Upon inflating these conventionally manufactured gas bags into their three-dimensional state which they must assume in order to achieve the desired protective effect, creases occur in particular in the seam area, which extend perpendicular to the seams. These creases result in high stress peaks in the seam area which is already weakened by the seam. In order to avoid bursting of the gas bag in the seam area under load, very heavy fabrics are used in the manufacture of the gas bag. These heavy fabrics in conjunction with the relatively large gas bag volume selected for achieving a good protective effect result in conventional gas bags being relatively heavy. In order to nevertheless ensure the rapid inflation when necessary, larger gas generators have to be employed which are capable of correspondingly rapidly accelerating the relatively large mass of the gas bag. Large pyrotechnical gas generators in turn are disadvantageous in that during inflation the temperature of the gas developed by the gas generator reaches very high values and that these high temperatures can affect the gas bag and destroy its fabric. In addition, a gas bag with a larger mass unfolds only later due to its higher inertia so that the hot gases developed by the gas generator act longer on the still folded fabric which is located near the gas generator. In order to not destroy the gas bag fabric as a result of this bombardment with the combustion gases great yarn thicknesses (approx. 250 to 700 dtex) are employed which ensure that the fabric does not fail even then when glowing particles impinge on the fabric and individual threads start melting.
SUMMARY OF THE INVENTION
The relatively large mass of conventional gas bags must, of course, not only be accelerated but also stopped again at the end of the inflation process. In this case, too, great loads occur in particular in the rear area which must be compensated by correspondingly reinforced seams or by multiple seams. These measures again result in an increase in the gas bag weight.
The conventionally used heavy fabrics not only have dynamic disadvantages but; in addition, enforce a relatively large packing volume due to the fact that they are also mostly relatively rigid. The seam areas are naturally particularly rigid and can therefore cause undesired injuries such as, for example, skin grazes of the occupant to be protected if the occupant assumes a so-called cut-of-position attitude while the gas bag unfolds. Any attitude which does not correspond to the optimum position relative to the gas bag is technically termed “out-of-position”, for example an occupant who is seated too close to the gas bag or lateral to it. In such out-of-position attitudes the risk to be fully hit by a rigid seam area is particularly high.
In order to fulfill its protective function the gas bag must comply with two additional and also contradictory requirements: As already mentioned it must be inflatable as rapidly as possible. This requirement can generally be met only with a very tight gas bag because only then will it be ensured that the gas developed by the gas generator is completely used for inflating. On the other hand, the gas bag in the inflated state must dampen the impact of an occupant of the vehicle. To this end the gas bag must allow a defined venting of its gas filling because otherwise the colliding occupant would bounce back. Therefore, in the side facing away from the vehicle occupant, conventional gas bags are provided with openings which can have a diameter of up to 50 mm. These openings are also referred to as “vents”. Because these openings are not closed during inflation, a considerable portion of the gas developed by the gas generator escapes so that the gas generator must have a correspondingly more powerful, i.e. larger, design in order to be able to reliably inflate the gas bag. Large gas generators, however, result in the above already explained thermal stresses of the gas bag fabric.
Finally, the conventionally employed heavy fabrics are not particularly tight because of the relatively great yarn thick nesses used so that these fabrics must generally be additionally coated in order to obtain the required tightness. The coatings, however, often have the problem of a poor ageing stability so that the satisfactory function of the gas bag might possibly no longer be ensured after many years.
Although known impact protection systems with gas bags decisively improve the occupants' safety, thus justifying their increasingly large-scale use, these systems still have quite a number of drawbacks which prevent an even better protective effect and moreover increase the manufacturing costs of conventional systems.
The invention is based on the object to improve conventional impact protection systems with gas bags in such a manner that with an increased protective effect as any of the above mentioned problems as possible are solved.
According to the invention this object is solved by an inflatable gas bag for an occupant
Lehmann Wilhelm Karl
Rychter Joseph
Hobbes Laurence P.
Johnson Brian L.
Klebe G B
Roberts Mlotkowski & Hobbes
Rychter Josef
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