Patent Publication Number: US-2006017268-A1

Title: Set for masking safety airbag with reinforcing members and corresponding methods for making same

Description:
The present invention relates to an assembly for masking an air-bag for a motor vehicle, the assembly being of the type comprising:  
      outer trim presenting a line of weakness which defines: 
          a flap overlying the air-bag; and     a peripheral region surrounding the flap and serving, after the flap has moved, to define an opening for passing the air-bag during its deployment;        

      a first reinforcing member for reinforcing the peripheral region, the first reinforcing member comprising at least one wall for guiding the air-bag upstream from the opening and during deployment thereof;  
      a second reinforcing member for reinforcing the flap; and  
      a hinge connecting together the first reinforcing member and the second reinforcing member so as to allow the flap to tilt and so as to retain it after the masking assembly has been ruptured along the line of weakness.  
      The invention applies in particular to the dashboard of a motor vehicle masking an air-bag for protecting a passenger of a motor vehicle.  
      In general, in such a dashboard, the hinge is formed by a net of rigid wires to which the first and second reinforcing members are secured.  
      When the air-bag deploys, it strikes the second reinforcing member and causes the flap to be separated from the peripheral region of the dashboard along the line of weakness. The hinge serves firstly to allow the flap to pivot to as to let the air-bag pass through, and secondly serves to retain the flap so that it does not injure an occupant of the vehicle.  
      In known dashboards, it has been found that the net constituting the hinge can tear under the forces induced by the air-bag deploying. That leads to risks of injury for the occupants of the motor vehicle, and in particular for the passenger situated facing the air-bag.  
      An object of the invention is to solve the problem by providing an assembly of the above-specified type which serves to limit the risk of the hinge rupturing during deployment of the air-bag, and which is simple to make, and therefore inexpensive.  
      To this end, the invention provides a masking assembly of the above-specified type, characterized in that the second reinforcing member and the hinge are made by molding a plastics material, and in that the hinge is overmolded on the first reinforcing member.  
      In particular embodiments, the assembly may comprise one or more of the following characteristics, taken in isolation or in any technically feasible combination:  
      the plastics material of the second reinforcing member and of the hinge possesses elongation prior to rupture of more than 500%;  
      the first reinforcing member includes portions in relief for connecting the hinge;  
      the hinge includes a retaining lip surrounding an edge of the first reinforcing member;  
      the guide wall(s) extend(s) over at least two sides of the deployment direction of the air-bag so as to form a guide channel;  
      the guide channel extends over substantially the entire perimeter of the through opening for the air-bag;  
      the hinge includes at least one fold;  
      it constitutes at least a dashboard for a motor vehicle.  
      The invention also provides a method of making an assembly as defined above, the method being characterized in that it includes a step of overmolding a plastics material onto the first reinforcing member to form the hinge and the second reinforcing member, and to connect them to the first reinforcing member.  
      In a variant, the method includes a step of fastening the first reinforcing member and the second reinforcing member to the trim that has previously been prepared. 
    
    
      The invention will be better understood on reading the following description given purely by way of example and made with reference to the accompanying drawings, in which:  
       FIG. 1  is a diagrammatic, fragmentary perspective view of a dashboard of the invention; and  
       FIG. 2  is a diagrammatic fragmentary section view on plane II-II of  FIG. 1 . 
    
    
      Below, the directions are the usual directions for a motor vehicle. In particular the terms “front”, “rear”, “right”, and “left” should be understood relative to the position of a driver and to the forward direction of the vehicle.  
       FIG. 1  shows the right side portion of a dashboard  1  for a motor vehicle, which dashboard masks a system  2  having an air-bag  3  that can be seen in  FIG. 2 .  
      The system  2  is of conventional structure and is not described in detail below.  
      The dashboard  1  includes outer trim  4 , itself comprising:  
      an outer skin  5 , e.g. made of thermoplastic polyvinyl chloride (PVC), of thermoplastic polyolefin (TPO), or of thermoplastic polyurethane (TPU), or of any other thermoplastic material enabling a flexible skin to be made; and  
      an inner layer  6  covered by the skin  5  and made, for example, of fiber-filled polypropylene so as to impart structural stiffness to the trim  4 .  
      A line  7  of weakness is formed in the trim  4  and defines a flap  9  covering the air-bag system  2  and a peripheral region  10  surrounding the flap  9 .  
      In plan view, the flap  9  is substantially in the form of a rectangle having rounded corners.  
      In conventional manner, and as described below, when the air-bag  3  deploys in a direction D ( FIG. 2 ), it moves the flap  9  away from the peripheral region  10 . The peripheral region  10  then forms a frame surrounding a through passage where the flap  9  used to be for deployment of the air-bag.  
      The line  7  of weakness is made in conventional manner, e.g. by means of a laser beam.  
      By way of example, the line  7  is constituted by a succession of spaced-apart cutouts passing through the inner layer  6  and made from the inside face of the trim  4  so as not to be visible from outside the dashboard  1 .  
      The line  7  of weakness extends all around the periphery of the flap  9 .  
      The dashboard  1  has a structure  12  for reinforcing the peripheral region  10 , a panel  13  for reinforcing the flap  9 , and a hinge  14  connecting the reinforcing panel  13  to the reinforcing structure  12 .  
      The reinforcing structure  12  comprises in particular a rounded web  16  which fits substantially snugly to the shape of the peripheral region  10  in the vicinity of the line  7  of weakness, and a channel  18  for guiding the air-bag while it is deploying.  
      The channel  18  extends the web  16  inwards from the dashboard  1 , i.e. downwards and forwards in  FIG. 2 .  
      By way of example, when seen from above, the channel  18  presents a quadrangular section, thus possessing four side walls that extend substantially around the entire perimeter of the opening that will be formed in the dashboard  1  when the air-bag  3  deploys. Only the front wall  20  and the rear wall  22  of the channel  18  can be seen in  FIG. 2 . These walls  20  and  22  are situated on opposite sides of the direction D.  
      The housing  24  of the air-bag system  2  may be mounted on the channel  18 , e.g. by engaging hooks of the housing  24  in openings formed in the side walls of the channel  18 .  
      The front wall  20  of the channel  18  possesses portions in relief  26  for connecting the hinge  14 , which portions are in the form of studs provided with enlarged heads  28 . These studs  26  project from the wall  20  towards the inside of the channel  18 .  
      The reinforcing structure  12  is made as a single piece of plastics material, e.g. by injection molding. By way of example, the plastics material may be fiberglass-filled polypropylene.  
      The reinforcing structure  12  is secured to the inside face of the layer  6  of the trim  4 , in the peripheral region  10 . This is achieved, for example, by vibration welding along ribs  30  that are provided on the outside face of the web  16  of the reinforcing structure  12 .  
      The reinforcing panel  13  is of a rounded shape that corresponds substantially to that of the flap  9  and its dimensions are slightly smaller than those of the flap  9 . The panel  13  is extended at its front edge (to the left in  FIG. 2 ) by the hinge  14 .  
      In succession, starting from the panel  13 , the hinge  14  comprises two oppositely-directed folds  32 , a connection wall  34  in which the studs  26  are embedded, and finally a lip  36  surrounding the bottom edge  38  of the front wall  20  of the channel  18 . The reinforcing panel  13  and the hinge  14  are made by molding a plastics material, for example, it may be a styrene/ethylene/butylene/styrene (SEBS) block copolymer.  
      The plastics material is molded onto the front wall  20  of the channel  18  so as to connect the hinge  14  to the reinforcing structure  12 .  
      The reinforcing panel  13  has been welded to the inside face of the flap  9 , e.g. along ribs  40  provided on the outside face of the panel  13 , using a vibration-welding technique.  
      To make the dashboard  1 , the reinforcing structure  12  is molded and then the hinge  14  and the reinforcing panel  13  are molded onto the reinforcing structure  12 . At the end of this overmolding operation, the studs  26  are embedded in the hinge  14  and the lip  36  surrounds the edge  38 . The hinge  14 , and thus the reinforcing panel  13 , are firmly connected to the reinforcing structure  12  by the studs  26  and the lip  36 .  
      Thereafter, the web  16  is welded to the reinforcing structure  12  and the reinforcing panel  13  is welded onto the outer trim  4  which has been made beforehand.  
      When the air-bag  3  deploys along the deployment direction D, it strikes the reinforcing panel  13  which pushes the flap  9  outwards from the dashboard  1 , i.e. rearwards and upwards.  
      The dashboard  2  then splits along the line  7  of weakness and allows the flap  9  to separate from the peripheral region  10 .  
      With the air-bag  3  continuing to push against the flap  9 , the folds  32  of the hinge  14  unfold so as to allow the flap  9  to move away from the peripheral region  9  as shown in dashed lines in  FIG. 2 .  
      Thereafter, still under drive from the air-bag  3 , the flap  9  pivots relative to the peripheral region  10  about the hinge  14  as shown in chain-dotted lines in  FIG. 2 .  
      The air-bag  3  can then deploy through the opening that has been released in this way by the flap  9  in the dashboard  1 .  
      As the air-bag  3  deploys, the channel  18  whose side walls are disposed on four sides around the direction D serve to guide the air-bag  3  upstream from the opening in the dashboard  1 . It should be observed that the front wall  20  guides the air-bag  3  via the wall  34  covering said front wall.  
      During the displacement of the flap  9 , the studs  26  and the covering lip  36  ensure that the flap  9  is well retained relative to the peripheral region  10  of the dashboard, thereby compensating the fact that the material used for making the reinforcing structure  12  and the reinforcing panel  13  do not interact.  
      In addition, using a highly deformable flexible plastics material to constitute the hinge  14  serves to limit the risk of it tearing. The hinge  14  deforms without breaking so as to absorb the forces induced by the air-bag  3  as it deploys. The folds  32  serve to further limit any risk of the hinge  14  tearing.  
      Nevertheless, the dashboard  1 , which comprises a limited number of elements made of distinct materials, turns out to be simple and inexpensive to make.  
      In other variants, the plastics material constituting the hinge  14  and the panel  13  is different from that described above.  
      Preferably, said material presents elongation prior to rupture of more than 500%.  
      In general, the trim  4  may be of a structure other than that described above.  
      The principles described above can be applied to making an element for masking an air-bag other than a dashboard. For example, they can be applied to a door panel.