Abstract:
The invention relates to a safety device having an airbag module which has a housing ( 40 ) and which can be mounted in the steering wheel of a motor vehicle, having a cover ( 10 ) fastened to the housing ( 40 ) in a movable manner, on which a first horn contact ( 30 ) is arranged; at least a second horn contact ( 50 ) is arranged on the housing ( 40 ), which, in the initial position, is electrically isolated from the first horn contact ( 30 ), and in the activation position, comes into electrical contact with the first horn contact ( 30 ) in order to trigger a horn signal. The second horn contact ( 50 ) being configured as a separate component which is fixed to the housing ( 40 ) by at least one separate locking element ( 60 ).

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to German Patent Application No. 10 2010 007 569.8, filed Feb. 10, 2010 and PCT/EP2011/000547, filed Feb. 7, 2011. 
     FIELD OF THE INVENTION 
     The invention relates to a safety device having an airbag module, which has a housing and can be mounted in the steering wheel of a motor vehicle having a cover which is fastened in a movable manner, on which a first horn contact is arranged. At least a second horn contact is arranged on the housing and, in an initial position, is isolated electrically from the first horn contact and, in an activation position, comes into electrical contact with the first horn contact in order to trigger a horn signal. 
     BACKGROUND OF THE INVENTION 
     WO 2008/079057 A1 relates to a safety device in the form of an airbag module which can be mounted to the steering wheel of a motor vehicle. The airbag module has a housing and a cover. The cover is mounted on the housing such that it can move. A wire is clipped onto the cover and configured to come into contact with contact parts, which are arranged on the housing, when the cover is displaced relative to the housing. The wire and the contacts work together as a contact arrangement that can be connected to an electrical circuit which controls the horn of the motor vehicle. If the cover is displaced in the direction of the housing, the wire comes into contact with the contact element and closes the electrical circuit. The contact element is an integral part of the housing which is configured from a metallic, electrically conductive material. 
     The object of the present invention is to provide a safety device which can be produced more easily and more cost-effectively. 
     According to the present invention, this object is attained by a safety device having the characteristics described and claimed herein. 
     The safety device according to the present invention has an airbag module which has a housing and can be mounted in the steering wheel of a motor vehicle, having a cover which is fastened to the housing in a movable manner, on which a first horn contact is arranged, at least a second horn contact is arranged on the housing which is isolated electrically from the first horn contact, and in an activation position, comes into contact with the first horn contact in order to trigger a horn signal. The invention provides that the second horn contact is configured as a separate component, which is fixed to the housing by at least one separate locking element. By configuring the second horn contact as a separate component, for example as a sheet metal component or as an electrically conductive molded part, it is possible to produce the housing from a plastic material, whereby the safety device is in general lighter and less expensive. The risk of faulty activation or electrical short circuits due to a metal housing is prevented. The electrical contact is only established at the contact points provided for that purpose. 
     The first horn contact can be configured as an electrically conductive wire which is fixed to the cover. The cover normally has a wall extending in the direction of the housing and facing away from the visible side, where the wire can preferentially be fixed to the external side of the wall. It can be clipped in or snapped in; other fastening methods are likewise possible. The wire can at least partially surround the wall of the cover, a resilient contact of the wire with the cover being preferably available. 
     The housing for accommodating the airbag as well as the gas generator can be made of a plastic material and preferentially completely consists of plastic, so that the housing can be easily and simply produced in a molding process, e.g. by means of injection molding. 
     The second horn contact can be configured as a conductive ribbon or as a conductive strip, for example made of sheet metal, metal fabric or the like. The locking element can at least have one resilient locking latch that fastens the locking element to the housing in a form fitting manner. The locking latch can engage in a recess or in a form fitting element of the housing, locking holders being configured at the housing which accommodate the locking element in a form fitting manner. The locking holders can for example be configured as frames into which the locking elements are inserted. After inserting the locking latch of the locking element through the locking holder, or through the frame, the resilient locking latch springs back to the initial position and form-fittingly locks the locking element on the locking holder. 
     The second horn contact can be guided through the locking holders and be fastened to the housing via the locking element. The locking element is preferentially made of plastic and has a front end against which the second horn contact abuts or rests. By supporting the second horn contact on the front end of the locking element facing the first contact of the locking element, the locking element of the second horn contact is not only fastened to the housing, but at the same time functions as a counter bearing and a bearing surface for the second horn contact in the region of the contact point between the first horn contact and the second horn contact. The contact point of the second horn contact is fixed relative to the first horn contact by the locking element so that no displacement of the second horn contact relative to the first horn contact can occur after establishing the electrical contact. Consequently the activation reliability of the horn signal is increased. 
     In the initial position, the first horn contact preferentially is not separated from the second horn contact by more than 3 mm in the direction of displacement of the cover (for horn actuation), so that only a short displacement path has to be covered relative to the housing in order to trigger a horn signal. By using a separate locking element, it is possible to adjust the contact distance almost arbitrarily without having to consider the requirements when locking and fastening the housing to the cover. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       An exemplary embodiment of the invention will be explained in more detail below with reference to the attached figures. The figures show: 
         FIG. 1  shows an inverted cover; 
         FIG. 2  shows a cover with a mounted first horn contact; 
         FIG. 3  shows a cover with the inserted housing; 
         FIG. 4  shows an embodiment according to  FIG. 3  with a second horn contact in position; 
         FIG. 5  shows a fully mounted safety device; and 
         FIG. 6  shows a detailed view of the safety device. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  shows a cover  10  of a safety device, where the upper side of the cover  10  cannot be seen. Vertical walls  11  extend upward facing away from the visible side. An airbag module, which will be explained later, can be inserted in this wall  11 . Pin-like projections  12  are likewise provided at the rear side of the cover  10  for holding and fixing coil springs  20 . The coil springs  20  are stuck onto the projections  12  and can be fixed to grooves there. The springs  20  are used to press the cover  10  away from the housing. 
     A wire  30  having a U-shape, being basically planar in shape, can likewise be seen in  FIG. 1 . The wire  30  is used as a first horn contact and can be electrically connected to the circuit in which the horn is arranged via connectors or the like. The U-shaped wire  30  can be fastened to the wall  11  of the cover  10 . Moreover, recesses  14  for locking elements of the housing are provided in the wall  11 . The function of these recesses  14  will be explained later. The whole cover  10  can be made of plastic in one piece as an injection molded part. The springs  20  as well as the wire  30  are preferably made of metal; the wire  30  is electrically conductive. 
     In  FIG. 2 , the cover  10 , the springs  20  and the wire  30  are joined together and configured as a modular part which is ready to hold the housing with the airbag. Supporting and holding devices  13  are provided at the housing wall  11  for the wire  30  as shown in  FIGS. 1 and 2 . In  FIG. 2 , wire  30  is placed in these supporting devices and holding devices  13  and clipped in, so that it cannot be displaced along the wall  11  in the displacement direction of the cover  10 , which essentially corresponds to the length of the pin-like holders  12 . In the mounted position, the wire  30  abuts firmly locked against the wall  11 . 
       FIG. 3  shows a housing  40  made of plastic already inserted in the cavity of the rear side of the cover  10  formed by the wall  11 . A folded airbag, which cannot be seen, is arranged inside the housing  40 . A gas generator to fill the airbag with expanding gas is likewise arranged on the housing  40 . The gas generator is not shown for the sake of clarity. 
     The housing  40  is placed on the projections  12  which are used as guides, and pressed downward against the resisting force of the springs  20  until the locking elements  41  engage in the recesses  14 . The locking elements  41  have undercuts which allow for the displacement of the cover  10  relative to the housing. After the assembly and the maximum compression of the springs  20 , they spring back and move the locking elements  41  upward in the drawing, that is, away from the visible side of the cover  10 . The recesses  14  form-fittingly fasten the locking projections  41  in the region of the undercut so that the housing  40  cannot be pressed out of the interior of the cover  10 . The housing has to be pressed out downward by the distance of the reset path, normally by eight to ten millimeters, for the locking to take place which would result in an accordingly long activation path if a second horn contact is integrally configured at the housing. 
     Locking holders  46  in the shape of frames can likewise be seen in  FIG. 3  that are configured or molded on the housing  40 . The working principle of the locking holders  46  will be explained later. 
     Furthermore, two horn contacts  50  are shown in the described embodiment, which are configured as angular, bent sheet metal parts. Alternative embodiments of the second horn contacts  50  are possible and provided. In the described embodiment, the second horn contacts  50  have longitudinal brackets at the ends that extend downward parallel to the wall  11  of the cover  10  and to the wall of the housing  40  with contact areas  53  protruding perpendicular to them. The contact areas  53  are configured to come into contact with the wire  30  when the cover is displaced against the compression force of the springs  20  in the direction of the housing  40 . 
     Locking elements  60  are further shown, by means of which the second horn contacts  50  can be fastened to the housing  40  via the locking holders  46 . 
     The preliminary assembly of the second horn contacts  50  is shown in  FIG. 4 . The brackets with the angled contact areas  53  which extend along the wall of the housing are guided through the frame-like locking holders  46 . They can additionally be fixed by means of projections or the like. The contact areas  53  are now directly located opposite the wire  30 . The locking elements  60  have as yet not been inserted. As can be seen in  FIG. 4 , the locking elements  60  made of plastic have locking latches  64  which are compressed on insertion of the locking holder  46 . After being pushed through, they displace outward and thus form-fittingly lock the locking element at the locking holder  46 . In the mounted state, the contact area  53  can be mechanically supported at the front end  65  of the locking element  60  facing the angled contact area  53  when the locking element  60  is completely inserted into the locking holder  46 . 
     The mounted state of the safety device is shown in  FIG. 5 . The safety device is configured as a ready-to-install module consisting of the cover  10 , the springs  20 , which are not visible, the first horn contact  30 , the housing  40 , the second horn contacts  50  and the locking elements  60 . 
       FIG. 6  shows a detailed mounting situation in the area of the contact points between the first horn contact  30  and the second horn contact  50 . It is likewise visible that each of the locking elements  41  has an undercut which allows the latches to extend over the upper end of the locking recess  14  in the wall  11  of the cover  10 . The locking elements are molded as one-piece on the housing  40 . The locking holder  46  is likewise molded as one-piece on the housing  40 . It is visible in  FIG. 6  that the locking latches  64  abut flush with the bottom side of the locking holders  46  facing the horn contact  30  and thus cause a form fitting locking of the locking element  60  on the one hand, and a form fitting locking of the inserted second horn contact  50  on the other hand. The angled contact surface  53  of the second horn contact  50  abuts against the front end  65  of the locking element  60 , so that the locking element  60  forms a mechanical stop and a mechanical support, or a counter bearing for the contact surface  53 , so that even repeated actuation of the horn contact by the displacement of the cover  10  does not cause the deformation of the relatively thinly and unstably configured second horn contact  50 . An increased functional safety and a light-weight embodiment of the safety device are achieved at the same time by the mechanical fastening and securing by means of the locking element  60 . In the described exemplary embodiment, the distance between the wire  30  as the first horn contact and the contact surface  53  is about 2 mm, so that only a short displacement path has to be provided in order to actuate the electrical contact for the circuit to be closed for activating the horn. 
     While the above description constitutes the preferred embodiment of the present invention, it will be appreciated that the invention is susceptible to modification, variation, and change without departing from the proper scope and fair meaning of the accompanying claims.