CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]    The present application claims priority to and the benefit of U.S. Provisional Patent Application Ser. No. 60/208,054 filed May 31, 2000. The foregoing provisional application is incorporated by reference herein in its entirety. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    The present invention relates to an air bag device comprising a horn switch, and, more particularly, to an air bag device which is constructed so that, when a module cover is pushed, only a module cover moves so as to turn on the horn switch.  
           [0003]    There is a type of driver-seat air bag device installed at the steering wheel of an automobile, which is constructed so that, when a module cover of the air bag device is pushed, a horn switch is turned on in order to blow a horn. In this case, when the air bag device is constructed so that only the module cover, and not the entire air bag device, moves to turn on the horn switch, only a small amount of pushing force is required to turn on the horn switch.  
           [0004]    An airbag apparatus  100  having such a structure is shown in FIG. 7. The airbag apparatus  100  comprises a retainer  102 , an airbag  106  attached to the retainer  102  with an airbag fitting ring  104 , an inflator  108  for inflating the airbag  106 , and a module cover  110  for covering the folded airbag  106 .  
           [0005]    An integral leg section  112  protrudes from the back side of the module cover  110 , and hooks  116  of a side-wall section  114  which is bent forward from the retainer  102  are inserted through openings  118  in the leg section  112 . Each hook  116  outwardly protrudes from the side-wall section  114  in an L-shape.  
           [0006]    The inflator  108  includes a flange  108   a . Bolts  120  protruding from the ring  104  are inserted through the retainer  102  and the flange  108   a , so that the inflator  108  is fixed to the retainer  102  together with the airbag  106  by tightening nuts  122 .  
           [0007]    The shape of the folded airbag  106  is maintained by a shape holding member  124 . The shape holding member  124  allows the airbag  106  to expand by breaking-off or deforming when the airbag  106  is inflated.  
           [0008]    A bracket  132  protrudes upwardly from a steering wheel  130 , and projecting pieces  134  protruding downward from the backside of the retainer  102 . The pieces  134  are fixed to the bracket  132  with bolts  136  and nuts  138 .  
           [0009]    A predetermined sized gap is formed between the back face of the module cover  110  and the shape holding member  124 . A predetermined sized gap is also formed between the opening  118  formed on the leg section  112  of the module cover  110  and the hook  116 . As a result, the module cover  110  can be moved vertically when viewing FIG. 29. When the module cover  110  is pressed, a horn switch (not shown) is pressed so as to be turned on. The horn switch is integrally formed with the retainer  102  and attached to an extending portion extending from the retainer  102 .  
           [0010]    In the driver-seat air bag device, when the inflator is actuated to inflate the airbag, the module cover is torn along a tear line due to the force applied from the inflating airbag. Then, a large force is exerted on the module cover in the direction in which the module cover is separated from the retainer.  
           [0011]    In a conventional air bag device which has its module cover firmly secured to its retainer, the module cover does not separate away from the retainer. However, in an air bag device which is constructed so that the module cover moves in a direction in which it comes into contact with and separates from the retainer, the hook  116  may get dislodged from the opening  118  of the leg  112  of the module cover.  
         SUMMARY OF THE INVENTION  
         [0012]    The present invention is directed to overcoming or at least reducing the effects of one or more of the problems set forth above.  
           [0013]    Accordingly, it is an object of the present invention to provide an air bag device which makes it possible to reliably retain a module cover by a retainer during the expansion of an air bag (that is, during the operation of an inflator), when the air bag device is of a type whose module cover can move in a direction in which it comes into contact with and separates from the retainer.  
           [0014]    According to the present invention, there is provided an air bag device comprising an air bag; a retainer to which the air bag is mounted; a module cover which covers the air bag, the module cover being movable towards the retainer; a wall projected from the retainer; a leg projected downwardly from an underside of the module cover; an opening formed in the leg; and a hook protruded from the wall, the hook extending into the opening; wherein the opening and the hook are separated by a space which allows movement of the module cover; and wherein a restricting member for restricting the movement of the leg in a direction in which the leg separates away from the wall is provided at the retainer.  
           [0015]    In such an air bag device, in the case where the module cover is torn followed by operating the inflator, even when the leg of the module cover tries to separate away from the wall of the retainer, the restricting member prevents the separation of the module cover away from the wall of the retainer. Therefore, the hook is not dislodged from the opening in the leg at all.  
           [0016]    It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only, and are not restrictive of the invention as claimed. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]    These and other features, aspects, and advantages of the present invention will become apparent from the following description, appended claims, and the accompanying exemplary embodiments shown in the drawings, which are briefly described below.  
         [0018]    [0018]FIG. 1 is a sectional view of an air bag device according to the present invention.  
         [0019]    [0019]FIG. 2 is a perspective view of an air bag device according to the present invention.  
         [0020]    [0020]FIG. 3 is a sectional view of an air bag device according to the present invention taken along line III-III of FIG. 1.  
         [0021]    [0021]FIG. 4 is a perspective view of a horn switch supporting member according to the present invention.  
         [0022]    [0022]FIG. 5 is a perspective view of a restricting member according to the present invention.  
         [0023]    [0023]FIG. 6 is a perspective view of a restricting member according to the present invention as viewed from a direction which is different from the direction from which the restricting member is viewed in FIG. 5.  
         [0024]    [0024]FIG. 7 is a sectional view of a floating module cover type air bag device. 
     
    
     DETAILED DESCRIPTION  
       [0025]    According to the present invention, as shown in FIG. 1, for example, the air bag device  1  comprises a retainer  2 , an air bag  3  which is mounted to the retainer  2  by an air bag mounting ring  4 , an inflator  6  for inflating the air bag  3 , and a module cover  5  which covers the air bag  3  which is folded. The module cover  5  has a tear line  5   t . When the air bag  3  is inflated by the inflator  6 , the module cover  5  is torn along the tear line  5   t . The air bag  3  which is folded has its shape retained by a shape retaining member (not shown).  
         [0026]    A leg  5 L is integrally provided on the underside of the module cover  5  so as to protrude therefrom. A hook  2 F of a side wall  2 S, which is bent forwardly from the retainer  2 , is inserted in an opening  5   a  of the leg  5 L. The hook  2 F is an L-shaped hook which is provided so as to protrude outwardly from the side wall  2 S.  
         [0027]    The leg  5 L is disposed so as to oppose the outer side of the side wall  2 S and so as to be separated by a predetermined space therefrom. A restricting member  10  for restricting the separation of the leg  5 L away from the side wall  2 S is provided along the outer side of the leg  5 L.  
         [0028]    The restricting member  10  comprises a standing wall  10   a  which opposes the outer side of the leg  5 L so as to be separated by a predetermined space therefrom, and a bottom portion  10   b  which extends around the bottom side of the retainer  2 . An opening  10   h  is formed in the standing wall  10   a  in order to receive the hook  2 F. The restricting member  10  and the retainer  2  are connected together at the opening  10   h , as shown in FIG. 1, to form a closed loop around the leg  5 L of the module cover  5 . As shown in FIG. 2, holes for inserting bolts  15  are provided in the bottom portion  10   b  of the restricting member.  
         [0029]    The inflator  6  has a flange  6   a.  The bolts  15  protruding from the ring  4  are passed through the retainer  2  and the flange  6   a,  and are engaged with nuts  16 , thereby securing the inflator  6  to the air bag  3  and the retainer  2 .  
         [0030]    As shown in FIGS. 5 and 6, some of the bolts  15  pass through the bottom portion  10   b  of the restricting member  10 , and the corresponding nuts  16  are engaged thereon in order to secure the restricting member  10  to the retainer  2 .  
         [0031]    As shown in FIG. 2, bases  8   a  of a horn switch supporting member  8  and a protrusion  9  protrude downward from the back surface of the retainer  2  are secured to a bracket (not shown) of a steering wheel by a bolt. As shown in FIG. 4, the horn switch supporting member  8  has a U shape which allows it to surround three sides of the retainer  2 , and a top portion  8   b  thereof faces the back side surface of the peripheral portion of the module cover  5  and extends in a direction perpendicular to the direction in which the module cover  5  advances and retreats.  
         [0032]    Extending portions  8   c  and extending portions  8   d  extend in a protruding manner from the top portion  8   b , with the extending portions  8   c  extending towards the left and right of the steering wheel (that is, towards the left and right relative to the steering wheel in the position where the automobile is advancing straight. This will also be true in the descriptions which follow.), and the extending portions  8   d  extending towards the bottom left and bottom right of the steering wheel. Ends of the extending portions  8   d  in the direction of extension engage a step of the steering wheel.  
         [0033]    As shown in FIG. 1, a horn switch  20  is provided between the extending portions  8   c  (FIG. 4) and the module cover  5  as described below. The horn switch  20  is also provided midway between the extending portions  8   d  (FIG. 4). Reference numerals  8   e  and  8   e  (FIG. 4) denote openings used for mounting the horn switch  20 .  
         [0034]    As shown in FIG. 2, the horn switch supporting member  8  is disposed along the left and right sides and the bottom side of the retainer  2 . The bases  8   a  are provided so as to extend along the left and right sides of the retainer  2 . Openings  8   h  and  9   h  for inserting a bolt are formed in the base portions  8   a  and the protrusion  9 , respectively. This bolt is screwed into an internally threaded hole formed in the bracket.  
         [0035]    The shape retaining member (not shown) for retaining the shape of the air bag  3  and the module cover  5  are separated by a predetermined space. The edge of the opening  5   a  formed in the leg  5 L of the module cover  5  and the hook  2 F are separated by a predetermined space in order to allow the module cover  5  to move upward and downward in FIG. 1. When the module cover  5  is pushed, the horn switch  20  is pushed and turned on.  
         [0036]    The horn switch  20  comprises a contact member  21 , a coil spring  22 , and a spring guide  23  which is externally fitted to the coil spring  22 . The contact member  21  comprises a clip portion  21   a  fitted to a rib protruded from the back surface of the module cover  5 .  
         [0037]    The contact member  21  includes a contact  26  which is a protrusion and engages with a head  23   a  of the guide  23 . When the module cover  5  is pushed, the contact  26  comes into contact with the top portion  8   b  of the horn switch supporting member  8 , causing the horn switch  20  to turn on in order to blow a horn.  
         [0038]    In the spring guide  23 , the head  23   a  is engaged into the contact member  21 , and a pair of resilient legs  23   b  provided at the base end side are engaged into the openings  8   e  of the top portion  8   b  of the horn switch supporting member  8 .  
         [0039]    In the air bag device  1  having such a structure, when the module cover  5  is pushed, only the module cover  5  retreats, causing the horn switch  20  to turn on, so that the horn blows.  
         [0040]    When, for example, an automobile collides, the inflator  6  operates to eject gas in order to inflate the air bag  3 . The module cover  5  is torn along the tear line  5   t,  then the air bag  3  inflates inside the vehicle and protects a passenger.  
         [0041]    During this time, the module cover  5  curves in the directions θ 1  and θ 2  as shown in FIG. 1, resulting in applying a force near the opening  5   a  of the leg  5 L in the direction in which it separates away from the side wall  2 S of the retainer  2 . However, since the standing wall  10   a  of the restricting member  10  is disposed along the outer side of the leg  5 L, the separation of the leg  5 L away from the side wall  2 S is restricted when the module cover  5  rotates in the direction θ 1 . Therefore, the hook  2 F does not separate away from the opening  5   a , whereby the module cover  5  is reliably retained by the retainer  2 .  
         [0042]    The horn switch supporting member  8  is disposed along the outer side of the leg  5 L, at the left side of FIG. 1 in order to prevent the leg  5 L at the left side in FIG. 1 from separating away from the side wall  2 S when the module cover  5  rotates in the direction θ 2 . This prevents the hook  2 F at the left side in FIG. 1 from separating away from the opening  5   a  of the leg  5 L. Therefore, the horn switch supporting member  8  also serves as a restricting member.  
         [0043]    As described above, the air bag device of the present invention which is constructed so that the module cover floats in order to turn on the horn switch makes it possible to reliably retain the module cover by the retainer even during the inflation of the air bag.  
         [0044]    Given the disclosure of the present invention, one versed in the art would appreciate that there may be other embodiments and modifications within the scope and spirit of the invention. Accordingly, all modifications attainable by one versed in the art from the present disclosure within the scope and spirit of the present invention are to be included as further embodiments of the present invention. The scope of the present invention is to be defined as set forth in the following claims.
An air bag device is provided comprising an air bag, a retainer to which the air bag is mounted, a module cover covering the air bag, a protruding member protruding from the module cover towards the retainer, and a restricting member positioned along the outer side of the protruding member. The restricting member restricts displacement of the module cover during air bag inflation.