Patent Publication Number: US-2005134032-A1

Title: Airbag folding method

Description:
TECHNICAL FIELD  
      The present invention relates generally to inflatable restraint devices for motor vehicles, and more particularly to a method of folding such a device.  
     BACKGROUND OF THE INVENTION  
      In recent years, engineering efforts in automobile safety systems have increasingly focused on inflatable restraint devices and methods/systems for their deployment. Of particular interest to designers are methods of folding the inflatable device or airbag to optimize the manner in which it deploys. Designs differ among the different types of airbags, for example, driver side, passenger side and side-impact airbags offer varying optimal deployment characteristics. Moreover, different vehicle structures as well as size and type of inflatable restraint apparatuses all provide different, sometimes competing considerations when developing airbag fold designs. For example, children or other relatively small occupants may have different requirements than larger occupants when it comes to optimizing vehicle safety systems. Complicating matters further, occupants may be out of a normal riding position during airbag deployment. There are thus continuing challenges to engineering broadly applicable systems that will operate effectively in view of the broad range of vehicle and occupant characteristics.  
      Further concerns relate to the equipment used in the inflatable restraint system other than the airbag itself. For instance, the inflator tends to be the heaviest, most expensive part of the system. Development of increasingly complex airbag structural and folding designs have been accompanied by the need for more powerful, and thus heavier and more complex inflators. Efficiency and production economics continue to drive engineering, however, and designers are therefore continually searching for ways to lighten and simplify restraint systems.  
     SUMMARY OF THE INVENTION  
      The present invention provides an airbag folding method comprising a plurality of steps. The method preferably begins by forming a set of pleats along each of a first and second edge of an airbag, the pleats having substantially equal depths. Next, a first half of the airbag is preferably folded a plurality of times, thereby forming a first fold body, and a second half of the airbag is preferably folded a plurality of times, thereby forming a second fold body. The pleats preferably form a plurality of adjacent layers extending along first and second edges of the airbag that upon supplying an inflation gas to an interior of the airbag resist unfolding, thereby directing the inflation gas initially predominantly into the first and second fold bodies. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a top perspective view of an unfolded airbag suitable for folding by a method according to a preferred embodiment of the present invention;  
       FIG. 2  is a top view of the airbag of claim  1  partially folded according to the present invention;  
       FIG. 3  is an end view of an airbag similar to  FIG. 2 ;  
       FIG. 4  is a top view of an airbag similar to  FIG. 2 ;  
       FIG. 5  is a sectioned view taken through line A-A of  FIG. 4 ;  
       FIG. 6  is a side view of an airbag similar to  FIG. 4 ;  
       FIGS. 7-11  are side views of an airbag sequentially folded according to a preferred embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION  
      Referring to  FIG. 1 , there is shown a top perspective view of an unfolded airbag  10  suitable for folding according to the present invention. The presently disclosed airbag folding method may be utilized with airbags positioned at various points in the automobile, for instance, top-mounts, mid-mounts, and lower-mounts, as well as in side-impact and driver-side systems. Those skilled in the art will appreciate that although rectangular airbags are preferred, round, elongate and other airbags may be folded according to the present invention. In a preferred embodiment, airbag  10  is attached by any known means to an inflator housing (not shown) near a throat  14 . The inflator housing is preferably secured adjacent the throat  14  by inserting a plurality of pegs (not shown) through matching holes  15  in the airbag. It should be appreciated that the various figures referred to herein are merely illustrative of the airbag folding method, as well as the airbag and inflatable restraint system components preferred in the practice of the present invention. Therefore, the various dimensions, proportions and materials illustrated should not be taken to limit the manner in which the invention may be practiced.  
      The method preferably begins by initially laying the subject airbag  10  substantially flat on a work surface such as a table. Although it is generally contemplated that the airbag will be folded manually, an automated system might be used without departing from the scope of the present invention. The various folding steps disclosed herein may be facilitated by substantially flattening each fold on the work surface (and therefore the entire airbag), however, the process can be carried out without flattening the airbag if desired. Referring to  FIG. 2 , a first set of inwardly extending tucks  12   a  and  12   b  are formed at a first or top edge  20  and a second or bottom edge  30  of airbag  10 .  FIG. 3  is an end view of airbag  10  similar to its conformation in  FIG. 2 , illustrating inward tucks  12   a  and  12   b.  Referring to  FIG. 4 , a second set of tucks  16   a  and  16   b  are formed along top edge  20  and bottom edge  30 . In a preferred embodiment, a total of four tucks are made along each of top and bottom edges  20  and  30 .  FIG. 5  is a cross section of  FIG. 4  taken along line A-A. As illustrated in  FIG. 5 , all of the tucking steps of the present method preferably form tuck sets or pleats “X” and “Y” comprising a plurality of substantially equal depth tucked regions extending substantially perpendicular to centerline “C”, illustrated in  FIG. 1 .  
      Upon folding airbag  10  as illustrated in  FIG. 5 , several subsequent steps are taken to prepare airbag  10  for installation into an airbag housing (not shown), and thenceforth in a vehicle. Referring to  FIG. 6 , there is shown an end view of airbag  10 , substantially as it would appear when folded into the conformation illustrated in  FIG. 5  and viewed from top or bottom edge  20  or  30 . Airbag  10  includes first and second halves  31  and  32 .  FIGS. 7-11  illustrate steps whereby the respective halves  31  and  32  are each folded or rolled into relatively compact first and second fold bodies (also denoted  31  and  32 ). In a preferred embodiment, fold bodies  31  and  32  are formed such that a lower fold  31   a  and  32   a  in each fold body hooks outwardly and is doubled back upon itself relative to a center Z of airbag  10 . Stated another way, the lowermost folds in each fold body “open” toward each other, toward center Z. Once folded into the conformation illustrated in  FIG. 11 , airbag  10  may be positioned in an airbag housing, and installed in a vehicle. Airbag  10  may optionally be covered with a protective wrapping prior to positioning in the housing to assist in maintaining the integrity of the folded airbag during storage.  
      Airbag  10  is preferably activated during or just prior to a crash or sudden vehicle deceleration. In a preferred embodiment, the associated vehicle is equipped with a crash sensor (not shown), which sends an electrical activation signal to a gas generator/inflator (also not shown) for supplying inflation gas to airbag  10 . The signal preferably induces the rapid production/release of inflation gas in a manner well known in the art, which is supplied to an interior of airbag  10  via throat  14 . The gas is preferably directed into airbag  10 , causing relatively rapid inflation thereof. Airbag  10  bursts through or displaces the various airbag covers, trim panels, etc. used in housing the airbag system, in a manner also well known in the art. By forming a set of pleats X and Y along top and bottom edges  20  and  30 , the regions of airbag  10  proximate the pleats tend to be more resistant to inflation than untucked regions of airbag  10 .  
      Upon activation of airbag  10 , gas is supplied to the airbag interior. The inflation gas is supplied via throat  14 , and has a tendency to initially flow predominantly toward first and second halves  31  and  32 . This is due to the fact that a relatively unobstructed pathway for the gas to flow exists in the directions of first and second halves  31  and  32  relative to throat  14 , i.e. in a direction substantially perpendicular to centerline “C” . Gas flowing in a direction substantially along centerline C must force unfolding or untucking of the pleats along top and bottom edges  20  and  30 . Thus, the present folding method induces gas to flow initially predominantly toward the folded first and second ends  31  and  32 . As a result, folded first and second ends  31  and  32  initially inflate substantially as two separate side-by-side expanding lobes of airbag  10 . As first and second ends  31  and  32  begin to fill with inflation gas, untucking of pleated regions X and Y begins. Essentially simultaneously, gas pressure induces expansion of airbag  10  proximate center Z. The expanding airbag pushes against first and second fold bodies  31  and  32 , urging them outwardly. Utilizing lower folds  31   a  and  32   a  that hook outwardly relative to center Z increases the tendency for airbag  10  to inflate substantially outwardly relative to center Z.  
      Thus, during initial inflation, frictional interaction among the layers of pleated regions X and Y are resistive to inflation, giving the inflation gas the tendency to flow initially predominantly into fold bodies  31  and  32 . By folding fold bodies  31  and  32  in the prescribed manner, the initial inflation of center Z enhances the tendency for outward expansion of airbag  10 . Upon still further inflation, the inflation of airbag  10  proximate center Z will catch up with inflation of first and second halves  31  and  32 . Eventually, the tucks are all untucked and airbag  10  will reach a fully inflated state. In a preferred embodiment, airbag  10  is mounted in a vehicle dashboard such that folded first and second ends  31  and  32  are positioned substantially left and right, respectively, of the center of the vehicle passenger seat. Thus, activation of airbag  10  preferably provides left and right expanding lobes positioned at left and right positions relative to a vehicle occupant. Accordingly, a center region of the airbag is “softer” than the respective left and right lobes. An occupant that impacts either of the left or right expanding lobes has a tendency to be guided toward the less expanded center region of the airbag. During certain crashes or other sudden vehicle deceleration wherein the occupant is out of a normal riding position, the expanding lobes can “scoop” an occupant toward the center region, reducing the risk of injury in some instances. Further, because the center region of the airbag inflates more slowly than the lateral, first and second regions  31  and  32 , the risk of injury resulting from forceful projection of the center of the airbag toward an occupant&#39;s face, known in the art as “bag slapping,” can be lessened.  
      One preferred embodiment of the present invention has been set forth above, however, it should be appreciated that numerous variations are possible. For example, the number and dimensions of the various folds may be altered. Rather than four tucks along the top and bottom edges  20  and  30 , a lesser or greater number of tucks might be made. Moreover, the number of tucks along top edge  20  and bottom edge  30  need not be the same. In some instances, it may be desirable to provide for relatively more or less rapid inflation of regions of the airbag proximate the top and bottom edges. In such applications, the number of tucks can be increased or decreased to increase or decrease, respectively, the resistance to inflation imparted by the tucks. Further, because of increased overlap of the layers of the airbag, and hence increased frictional interaction, it is believed that deeper tucks impart a greater resistance to inflation than relatively shallower tucks, and the depth of tucked regions may be varied accordingly.  
      The present description is for illustrative purposes only; the description and illustrations herein should not be construed to narrow the scope of the present invention in any way. Thus, those skilled in the art will appreciate that various alterations could be made to the presently disclosed embodiments without departing from the spirit and scope of the present invention. For instance, embodiments are contemplated in which tethers are utilized to assist in optimizing the deployment trajectory of the inflating airbag. The tethers may be attached at varying points in the airbag, and optimal designs depend on the specific vehicle dimensions. Such tethers have also been shown to be useful in volume control of the airbag. When the airbag is maximally expanded under the restraint of the tether(s), excess inflation gas can be discharged through vents in the airbag. Other aspects, features and advantages will be apparent upon an examination of the attached drawing figures and appended claims.