Patent Publication Number: US-2004041373-A1

Title: Gas bag module and method for assembly of a gas bag module

Description:
TECHNICAL FIELD  
       [0001] The invention relates to a gas bag module and to a method for mounting and disassembling a gas bag module.  
       BACKGROUND OF THE INVENTION  
       [0002] Gas bag modules for drivers and passengers are now part of the regular equipment in many vehicles. Therefore, a need exists to manufacture such gas bag modules at as favourable a cost as possible. A time-consuming operating step is the assembling of the module and here, inter alia, the installation step in which the gas bag is connected by means of a gas bag holding element with a gas generator and/or with a generator holder or a module housing. This connection must be able to withstand high forces, so that the gas bag can not detach itself from the module during unfolding. A known, but work-intensive way consists in providing the gas bag holding element with threaded pins which are secured by nuts.  
       BRIEF SUMMARY OF THE INVENTION  
       [0003] It is an object of the invention to provide a simple, quick and favourably-priced connection between a gas bag holding element and a generator holder or a module housing.  
       [0004] This is achieved in a gas bag module comprising a gas bag, a gas bag holding element and a generator holder. The gas bag holding element is fastened to the generator holder by means of at least one drive screw.  
       [0005] Drive screws are fastening means known from structural housing engineering. Drive screws unit features from nails and screws. A drive screw is formed in a way that it can be driven into a component with a purely translational force like a nail. Owing to the integrated thread, the drive screw can be detached by a rotational movement like a conventional screw. This offers the advantage that on the one hand the drive screw can be fastened quickly and securely by a brief, purely axial action of force, but on the other hand can be detached again like a conventional screw. The installation time is distinctly shorter than with a conventional screw connection. As no thread has to be provided on the gas bag holding element, the manufacturing costs of this component are reduced.  
       [0006] In this connection the term “drive screw” is meant to include also screw nails, in particular a screw nail according to DIN 68 163-A.  
       [0007] In the sense used here, the generator holder is the component on which the gas bag is secured by means of the gas bag holding element. The generator holder can also be constructed as a module housing and can thus at the same time hold the gas generator and the gas bag. In addition, the generator holder can be fastened directly to the vehicle or connected with the vehicle by means of further components.  
       [0008] Preferably, the gas bag holding element and the gas generator holder consist of plastic. The drive screw can likewise be made of plastic or metal.  
       [0009] Advantageously a drive screw is used which has a sawtooth profile which prevents the fastening being detachable by a traction in axial direction. In addition, the drive screw advantageously has a worked-in thread, so that it can be undone in the manner of a conventional screw.  
       [0010] In a preferred embodiment of the invention, the gas bag holding element has at least one expandable, sleeve-like extension to receive the drive screw, the sleeve-like extension being able to be expanded for example by at least one axial slit. The sleeve-like extension is advantageously spread apart radially by the drive screw, whereby a secure clamping of the sleeve-like extension in the generator holder can be achieved.  
       [0011] Advantageously, the sleeve-like extension has in addition a detent shoulder which comes into abutment against the generator holder. Especially in connection with the radial spreading of the sleeve-like extension, an axially-acting form-fitting connection with the generator holder can thus be achieved in a simple manner.  
       [0012] Preferably, an inner wall of the extension has at least one bead which is in engagement with the drive screw. This bead prevents the drive screw from being able to detach itself in the case of axial traction.  
       [0013] The proposed method for connecting the gas bag holding element with the generator holder can also be transferred to other connections, e.g. to installation of the gas generator holder on a vehicle. Here, also, the advantage of the drive screw can be used, namely that in a short time a secure connection is able to be produced which is detachable again in a simple manner.  
       [0014] It is a further object of the invention to provide a method with which a gas bag module can be easily assembled or mounted and disassembled. The method can be used for assembly of the single parts of a gas bag module as well as for mounting the complete gas bag module to the vehicle.  
       [0015] This object is achieved in that for assembling or mounting the gas bag module at least one drive screw provided with a thread is used. The drive screw is driven into two parts to be fixed at each other by a purely translational force. On disassembling the module the drive screw is detached from the parts by a rotational movement. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0016]FIG. 1 shows a diagrammatic partial view, in section, of a gas bag module according to the invention, in which the parts are attached to each other by the method according to the invention;  
     [0017]FIG. 2 shows a diagrammatic perspective view of a gas bag holding element to use in a gas bag module according to the invention;  
     [0018]FIG. 3 shows the gas bag holding element of FIG. 2 viewed from its upper side;  
     [0019]FIG. 4 shows a top view onto the gas bag holding element of FIG. 3;  
     [0020]FIG. 5 shows a section along the line V-V in FIG. 4;  
     [0021]FIG. 6 shows an enlarged cut-out X from FIG. 5, which corresponds to a section along the line VI-VI in FIG. 4;  
     [0022]FIG. 7 shows a section along the line VII-VII in FIG. 6;  
     [0023]FIG. 8 shows an enlarged diagrammatic partial view of FIG. 1;  
     [0024]FIG. 9 shows a diagrammatic sectional view along the line IX-IX in FIG. 8;  
     [0025]FIG. 10 shows a part of a gas bag holding element of a gas bag module according to a further embodiment;  
     [0026]FIG. 11 shows a section along the line XI-XI of FIG. 10; and  
     [0027]FIG. 12 shows a section along the line XII-XII of FIG. 10. 
    
    
     DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT  
     [0028] The gas bag module  10  illustrated in FIG. 1 has a generator holder  12  which in the example shown here is constructed as a module housing. A gas generator  14  and a gas bag  16  are fastened to the generator holder  12  by means of a gas bag holding element  18 .  
     [0029] The gas bag holding element  18  is constructed in a ring shape and is inserted into an inflation opening of the gas bag  16 . The gas bag holding element  18  has several sleeve-like extensions  20  formed on in one piece (see also FIGS.  2  to  7 ), which extend through openings in the gas bag  16  and in the generator holder  12 . Drive screws  22  are introduced into these sleeve-like extensions  20 , via which the gas bag holding element  18 , the gas generator  14 , the gas bag  16  and the generator holder  12  are firmly connected with each other.  
     [0030] In the head region, each drive screw  22  has an engagement structure formed e.g. as a protrusion or a depression. The engagement structure allows a transfer of a rotational movement to the drive screw  22  to disengage the drive screw  22  from the gas bag module  10 , for instance with a tool like an Allan key or a crosstip screwdriver.  
     [0031] The gas bag holding element  18  is described in detail below. At the end directed away from the gas bag holding element  18 , each sleeve-like extension  20  has axial slits  24 . The slits  24  can extend up to the ring-shaped base body  25  of the gas bag holding element  18 , so that the extension  20  is composed of several curved segments  26 , four segments in the example shown here. On each segment  26  in addition a detent shoulder  27  is constructed, which comes into abutment against the generator holder  12  when the gas bag module  10  is assembled. Owing to the slits  24 , the radial expansion of the sleeve-like extensions  20  can be reduced, so that in spite of the detent shoulders  27 , a penetration of the extensions  20  through the openings of the generator holder  12  is possible. The detent shoulders  27  have chamfers  30  acting in the insertion direction, which facilitate the passage of the sleeve-like extensions  20  through the openings in the generator holder  12 .  
     [0032] On introduction of the drive screw  22 , the sleeve-like extension  20  is slightly widened in radial direction, so that the detent shoulders  27  engage behind the generator holder  12  and lie firmly against the generator holder  12 , from which a form-fitting connection results in axial direction and, in addition, a secure clamping connection between the extensions  20  and the generator holder  12 . During assembly the drive screw  22  is driven into the generator holder  12  and the extension  20  by a purely translational axial force.  
     [0033] On the inner wall of the sleeve-like extensions  20 , beads  28  are constructed, which can run in axial or peripheral direction (FIG. 9). The drive screw  22  has a thread with sawtooth profile, as can be seen in FIG. 8. The beads  28  engage into the sawtooth profile, whereby the drive screw  22  is additionally secured against detachment by axial traction.  
     [0034] The beads  28  act as a counter thread, so that the drive screw  22  can be detached like a normal screw.  
     [0035] The gas bag holding element  18  preferably consists of plastic and can advantageously be produced in one piece by injection moulding. Also, the generator holder  12  and the drive screw  22  can be produced from a suitable plastic, but can also consist of metal.  
     [0036] The installation of the gas bag module  10  takes place in a simple manner. The gas generator  14  is inserted into the generator holder  12  and the gas bag holding element  18  is inserted into the gas bag  16 , and the sleeve-like extensions  20  of the gas bag holding element are inserted through the openings in the gas bag  16  and in the generator holder  12 . Then the drive screws  22  are driven into the sleeve-like extensions  20  by a brief axial force action. For dismantling, the drive screws  22  merely have to be unscrewed from the sleeve-like extensions  20 .  
     [0037] In the embodiment shown in FIGS.  10  to  12 , the gas bag holding element  18  includes pins  60  formed integrally therewith, the pins  60  being provided additionally to the extensions  20  and arranged in the vicinity thereof. The pins  60  extend in the same direction as the extensions  20 . On assembly of the gas bag module  10  the pins project through corresponding openings in the gas bag holding element  18  (not shown) and are engaged by an appropriate device (also not shown). To this account, each pin  60  is provided with a groove  62 . By this arrangement, the axial force used for driving in the drive screw can be counteracted, so that the parts to be connected are not pressed apart. The pins  60  do not form a clip connection with the gas bag holding element  18 . On disengagement of the drive screw  22  the pins  60  are simply pulled out of the gas bag holding element  18 .  
     [0038] The gas bag module  10  can also be fastened to a vehicle by similarly constructed connections (not shown).  
     [0039] It is also to be stressed that the gas bag holding element  18  can be formed by the flange  50  of the gas generator  14 , the flange  50  replacing the ring-shaped base body  25  of the gas bag holding element  18 . In this embodiment, it would be possible to construct the sleeve-like extensions  20  as individual plastic pegs which engage into holes on the flange and project through the openings in the gas generator holder.  
     [0040] Instead of being provided on the gas bag holding element, the sleeve-like extensions  20  could also be provided on the generator holder  12  and project through openings in the flange  50  or in a separate gas bag holding element  18 , the fastening taking place in an analogous manner to the embodiment described above.