Abstract:
A textile material blank is proposed for the manufacture of an air bag for air bag modules to be installed in vehicles as an impact protection device for vehicle occupants. The airbag module has an airbag carrier. The blank has one or more connecting flaps ( 1 ), either formed integrally with the blank ( 2 ) or attached to it, for the purpose of attaching the air bag to the airbag carrier.

Description:
The present invention relates to a textile material blank fox the manufacture of an air bag for air bag modules to be installed in vehicles as impact protection devices for vehicle occupants. 
     BACKGROUND OF THE INVENTION 
     Such impact protection devices serve as improvement of the passive safety of vehicles, air bag modules having been introduced as standard successively for the driver, where they are housed in the steering wheel, for the second front passenger, where they are housed in the instrument panel, as well as side air bags housed in the doors or seats, respectively and now form part of the basic equipment of almost all modern vehicles. For each vehicle there is a requirement for one to four or even more air bag modules so that the number of manufactured air bags exceeds by far the number of the corresponding vehicles produced. It is, therefore, understandable that efforts are being made to improve the air bag modules as regards manufacturing expenditure, weight, disposal, assembling expenditure etc. 
     For large scale manufacture of air bag modules, the air bag is usually made up of two circular material blanks which are joined to each other at their rims, one of them having a central intake throat for the inflation gases, the rim being normally clamped between an air bag holding plate and a carrier component of the air bag module. This way of air bag attachment has proved successful over time, but it is also relatively expensive. The air bag holding plate must be inserted through the intake throat and then fixed in relation to the intake throat within the air bag. It must have no sharp edges, to prevent the material from being torn in case the air bag is activated. Furthermore the clamping action around the inlet throat must be applied with a certain minimum force in all places to prevent the material from slipping out at some points in case the air bag is activated whereby is impaired the functionality of the air bag. In order to achieve a sufficiently strong clamping action, the clamping area must be of a certain width, whereby are implied limitations as to the installation and folding possibilities of the air bag. 
     SUMMARY OF THE INVENTION 
     The invention attempts to meet the requirement to overcome the aforementioned disadvantages of the air bag attachment method and to modify the material blanks for the manufacture of the air bag in such a way that there is no longer a need to rely on a conventional clamping connection, and that other means of attachment can be realized without increasing the manufacturing cost of the air bags as a consequence. 
     According to the invention, a material blank design of the type mentioned above is proposed which is characterized by at least one connecting flap, either formed integrally with the blank or attached to it, and provided for the purpose of attaching the air bag to an airbag carrier component. 
     The invention is based on the reasoning that the conventional clamping of the rim at the inlet throat may be dispensed with if the material blank is provided with one or more connecting flaps which may then be used to fix the air bag within the air bag module. Such connecting flaps may be formed as an integral part of the material blank for the manufacture of the air bag or they may be cut out separately and joined to the material blank for the air bag. For all that the tissue material which forms the air bag is consequently subjected to a stretching strain, whereby the required holding forces can be controlled substantial easier than in the case of a clamped joint which for safety reasons always has to be made oversize on account of inevitable manufacturing tolerances. In addition it also is constructionally easier to realize the air bag attachment by means of connecting flaps. 
     The invention also provides an air bag attachment which makes use of the inventive material blank to the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows a cutaway section of a material blank with a central inlet throat; 
     FIG. 2 shows a one-piece material blank with folding line; 
     FIG. 3 shows an air bag attachment in section; 
     FIG. 4 shows the air bag attachment according to FIG. 3 as a developed projection, and 
     FIG. 5 illustrates an air bag attachment which includes the cover plate. 
    
    
     DETAILED DESCRIPTION OF INVENTION 
     Referring to the cutaway section in FIG. 1 the material blank  2  with central inlet throat  3  shows three connecting flaps  1  radially extending inwards which consist of the material strips  1   a, b, c  and which are connected integrally with the rim of the inlet throat  3 . In the eventuality that the size of the inlet throat  3  does not allow for the provision of sufficiently long connecting flaps  1 , these can be extended by either sewn on or glued on material strips. The flaps  1   a, b, c  are provided with locating holes  7 , the function of which will be explained further on. 
     FIG. 2 illustrates a material blank which consists of two main parts  5 ,  6 , arranged symmetrically with respect to a folding line  4 , which are provided with neck-shaped projection  5   a ,  6   a , to each of which are connected integrally two flaps  1   e  and  1   d . An air bag made from a blank according to this design will have a hose-shaped projection made up of parts  5   a ,  6   a  which is pushed over a tubular projection of the gas generator for the inflation of the air bag and clamped onto it by means of a hose clip or similar. It is, however, not necessary for a clamping attachment of this type to absorb the holding forces on activation of the air bag, because these can be transmitted to a carrier component via the flaps  1   e ,  1   d , the locating holes  7  being pushed over pins or similar of the carrier component. 
     From FIG. 3 it becomes apparent how the flaps  1   a  to  1   e  may be folded around the rear or lower edge  13 , respectively, of a carrier component  10 . The ends provided with locating holes  7  are folded by 180° and fixed by means of their locating holes  7  to locating pins  8  provided on the outside of the carrier component  10  or similar. The width of the flaps can be adapted to the occurring holding forces, and the 180° fold ensures that part of the holding forces is absorbed by friction. The ends of the flaps can be pushed into pockets  18  which are formed at either the carrier component  10  or at the side wall area  14  of the cover plate  11 . 
     FIG. 4 shows the air bag attachment according to FIG. 3 as a view on a developed area of the carrier component  10 . The carrier component  10  can be embodied as a cup-shaped part with a bottom  10   a  and a side wall  10   b , it being only necessary to ensure that the flaps  1   a  to  1   e  can be wrapped around the edge  13  and can be folded by 180° towards the front or upwards, respectively. In the embodiment shown, recesses  10   c  between the bottom  10   a  and the side wall  10   b  have been provided to this effect, through which recesses the flaps  1   a  to  1   e  may be lead through and fixed to the locating pins  8  with their ends provided with locating holes  7 . 
     FIG. 5 illustrates a particularly advantageous air bag attachment, making use of the material blanks according to the invention, a cup-shaped carrier component  10  and a lid-type cover plate  11  being provided which have side wall areas  14 ,  15  which are concentric and in contact with each other when in their assembled state. Interacting lips  16  and recesses  17  in the side wall areas  14 ,  15  act together to make it possible to position the carrier component  10  and the cover plate  11  relative to each other. Both the lips  16  and the recesses  17  can furthermore be shaped in such a way as to form an additional form-locking clip union  12 . 
     The flaps  1   a  to  1   e  of the material blank are lead through from top to bottom through a recess  9  of the carrier component  10 , then folded upwards by 180° and then pined up on the locating pins  8 , provided on the outside of the side wall  14  of the cover plate  11 , by means of the locating holes  7 . The reason why this type of air bag attachment is so advantageous is because the cover plate  11  can be attached at the same time, and because the flaps  1   a  to  1   e , provided according to the Invention, not only replace the otherwise required means for the attachment of the air bag to the carrier component, but also the otherwise required means for the attachment of the cover plate  11  to the carrier component  10 . This method of air bag attachment also offers a very favorable path of lines of force because the opening forces acting from the air bag on the cover plate  11  are directly diverted to the side wall areas  14  of the cover plate  11  on account of the 180°-folded flaps  1   a  to  1   e , and will therefore be compensated. In other words, the explosive forces, acting in the opening direction, which are produced on activation of the air bag, are used to secure the cover plate  11  against the carrier component  10 . No further securing means for the control of the holding forces are required. Here, too, it is of course possible to adapt the width of the flaps to the holding forces to be absorbed and, because of the 180° fold, part of the holding force is absorbed by friction.