Abstract:
An airbag having an array of slits formed therein between its two attachment points, each slit seamed to be impermeable to the inflation medium. The slits are oriented to be perpendicular to a line defined by these two attachment points. The slits may be in offset rows and are each longer than the distance between the rows to allow the airbag to be significantly expanded by pulling in opposite directions on its attachment points. The airbag thus made can, when expanded, be folded to fit into a housing running along the roofline of a vehicle. Upon inflation and forcing itself from the housing, it will contract sharply, increasing its tension between attachment points and serving to both cushion and restrain passengers against lateral impact.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The present invention relates to inflatable protective cushions, and more specifically relates to airbags useful in side protection of occupants in a transportation vehicle, such as an automobile.  
         [0002]     Inflatable protective cushions used in passenger vehicles are a component of relatively complex passive restraint systems. The main elements of these systems are: an impact sensing components, an ignition component, a propellant material or stored gas system, an attachment device, an enclosure, and an inflatable protective cushion. Upon sensing an impact, the stored gas system is ignited causing an explosive release of gases filling the cushion to a deployed state that can absorb the impact of the movement of a body against it and dissipate its energy by means of venting of the gas. The entire sequence of events occurs within about 20 milliseconds.  
         [0003]     This inflation medium is generally nitrogen or helium gas generated from a gas generator or inflator (the term “airbag” will be used for convenience herein regardless of the inflation medium actually used). The inflation medium is conveyed into the cushion at a relatively warm temperature.  
         [0004]     In the un-deployed state, the airbag is most commonly stored in or near the steering column, the dashboard, in a door panel, or in the back of a front seat placing the cushion in close proximity to the person or the object it is to protect.  
         [0005]     A typical construction material for airbags has been a polyester or nylon fabric, coated with an elastomer such as neoprene, or silicone. The fabric used in such bags is typically a woven fabric formed from synthetic yarn by weaving practices that are well known in the art. The use of a coating material has found acceptance because it decreases the rate of permeability of the inflation medium. The coating helps to block the permeation of the fabric by such gas, thereby permitting the cushion to rapidly inflate without undue decompression during a collision event.  
         [0006]     Airbags may also be formed from uncoated fabric that has been woven in a manner that creates a product possessing low permeability or from fabric that has undergone treatment such as calendaring to reduce permeability. Fabrics that reduce air permeability by calendaring or other mechanical treatments after weaving are disclosed in U.S. Pat. No. 4,921,735; U.S. Pat. No. 4,977,016; and U.S. Pat. No. 5,073,418 (all incorporated herein by reference).  
         [0007]     Silicone coatings typically utilize either solvent-based or complex, two-component reaction systems. Dry coating weights for silicone have been in the range of about 3 to 4 ounces per square yard or greater for both the front and back panels of side curtain airbags. Alternatively, the use of a particular type of polyurethane as a coating as disclosed in U.S. Pat. No. 5,110,666 to Menzel et al. (herein incorporated by reference) permits low add on weights reported to be in the range of 0.1 to 1 ounces per square yard but the material itself is relatively expensive and is believed to require relatively complex compounding and application procedures due to the nature of the coating materials.  
         [0008]     The driver-side airbags are typically of a relatively simple configuration in that they function over a fairly small well-defined area between the driver and the steering column. One such configuration is disclosed in U.S. Pat. No. 5,533,755 to Nelsen et al., issued Jul. 9, 1996, the teachings of which are incorporated herein by reference. However, inflatable cushions for use in the protection of passengers against frontal or side impacts must generally have a more complex configuration since the position of a vehicle passenger may not be well defined and greater distance may exist between the passenger and the surface of the vehicle against which that passenger might be thrown in the event of a collision.  
         [0009]     The majority of commercially used restraint cushions are formed of woven fabric materials utilizing multifilament synthetic yarns of materials such as polyester, nylon 6 or nylon 6,6 polymers.  
         [0010]     As will be appreciated, the permeability of the cushion structure is an important factor in determining the rate of inflation and subsequent rapid deflation following the impact event. In order to control the overall permeability of the cushion, it may be desirable to use differing materials in different regions of the cushion. Thus, the use of several fabric panels in construction of the cushion may prove to be a useful design feature. The use of multiple fabric panels in the cushion structure also permits the development of relatively complex three-dimensional geometries that may be of benefit in the formation of cushions for passenger side applications wherein a full bodied cushion is desired. While the use of multiple fabric panels provides several advantages in terms of permeability manipulation and geometric design, the use of multiple fabric panels for use in passenger side restraint cushions has historically required the assembly of panels having multiple different geometries involving multiple curved seams.  
         [0011]     As will be appreciated, an important consideration in cutting panel structures from a base material is the ability to maximize the number of panels which can be cut from a fixed area through close-packed nesting of the panels. It has been found that minimizing the number of different geometries making up panels in the cushion and using geometries with substantially straight line perimeter configurations generally permits an enhanced number of panels to be cut from the base material. The use of panels having generally straight-line profiles has the added benefit of permitting the panels to be attached to one another using substantially straight seams or to be substantially formed during the weaving process using a jacquard or dobby loom. For the purposes of this invention, the term “seam” is to be understood as any point of attachment between different fabric panels or different portions of the same fabric panel. Thus, a seam may be sewn (such as with thread), welded (such as by ultrasonic stitching), woven (such as on a jacquard or dobby loom, as merely examples), and the like. The key issue regarding seam length within this invention pertains to the ability to form a highly available inflation airspace volume cushion with the lowest amount of labor needed. Since sewing, welding, etc., procedures to connect panels or portions of panels greatly increases the time necessary to produce airbag cushions, it is highly desirable to reduce the labor time which can be accomplished through the reduction in the length of seams required. Substantially straight seam configurations thus provide more cost-effective methods of producing such airbags.  
         [0012]     As alluded to above, in addition to driver-side and passenger-side airbags, there are side impact and side curtain airbags. Side impact airbags are linear, tubular structures; side curtain airbags are panel-like and cover a larger area. These both have been designed primarily to protect passengers during side crashes and to provide rollover protection, unfolding from packing housings stored within the roofline along the side windows of an automobile (and thus have a back and front side only). Side curtain airbags not only provide cushioning effects but also provide protection from broken glass and other debris. As such, it is imperative that side curtain airbags, as noted above, retain large amounts of gas, as well as high gas pressures, to remain inflated throughout the longer time periods of the entire potential rollover situation. To accomplish this, these side curtains are generally coated with very large amounts of sealing materials on both the front and back. Since most side curtain airbag fabrics comprise woven blanks that are either sewn, sealed, or integrally woven together, discrete areas of potentially high leakage of gas are prevalent, particularly at and around the seams.  
         [0013]     In addition to the duration of air retention, side impact airbags and side curtain airbags must be able to contract upon inflation to achieve a high degree of tension against the lateral force of the occupants of the vehicle. Ideally, this tension should be as high as possible, and be sufficiently high with relatively low volumes of air in the airbag so that, even while still inflating, they provide restraint against lateral forces.  
       SUMMARY OF THE INVENTION  
       [0014]     In view of the foregoing, it is an object of the invention to provide an airbag that has higher tension upon inflation. Thus, the present airbag, which may be used as side impact airbag in a stand-alone configuration, or may be added to a side curtain airbag along its bottom edge to increase the tension along that edge, achieves this object by its design. Specifically, it is an inflatable tubular structure with a series of sealed slits which sometimes are formed perpendicular to a line between the anchoring points of the airbag. The slits are preferably arranged in staggered rows in a brick pattern with the length of each slit being longer than the distance between rows. These slits allow the uninflated airbag to be stored in its housing along the roof lie. Upon inflation, the present airbag tends to contract to its uninflated length but, because it is restrained at the anchoring points, it cannot. Therefore, its tension increases significantly.  
         [0015]     One feature of the present invention is the series of slits perpendicular to a line between the airbag&#39;s anchoring points. When the slit airbag is stretched along this line for attachment in the uninflated state to the anchors, the airbag expands in the same manner as expanded metal grating. Because of the slits, the airbag can be stretched over a greater distance than covered by its woven shape. Upon inflation, relatively little air causes the airbag to tend to contract to its original un-stretched configuration, resulting in high tension at low air volumes.  
         [0016]     One advantage of the present invention is that it can be adapted for both use in side impact airbags and side curtain airbags, providing tension in either configuration.  
         [0017]     Another advantage of the present invention is that it is a change in configuration of an otherwise standard inflatable tubular structure, readily achievable by making a simple series of sealed slits. Implementing the invention, as a result, is simplified and requires no change in the airbag housing or packing procedures or in the airbag composition.  
         [0018]     Additional features and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The features and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the written description and claims as well as the appended drawings.  
         [0019]     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  
       [0020]     The accompanying drawings which are incorporated in and constitute a part of this specification, serve to illustrate several preferred embodiments and practices according to the present invention and together with the description, serve to explain the principles of the invention wherein:  
         [0021]      FIG. 1  is a view of the interior of a passenger vehicle with a deployed inflatable side impact airbag, according to a preferred embodiment of the present invention.  
         [0022]      FIG. 2  is a view of the interior of a passenger vehicle with a deployed inflatable side cushion airbag, according to a preferred embodiment of the present invention.  
         [0023]      FIGS. 3A, 3B  and  3 C illustrate detailed views of an airbag according to a preferred embodiment of the present invention, with  FIG. 3A  illustrating the uninflated airbag,  FIG. 3B  illustrating the folded stretched airbag, and  FIG. 3C  illustrating the inflated airbag, according to a preferred embodiment of the present invention.  
         [0024]      FIGS. 4A and 4B  illustrate a portion of an inflatable airbag structure before and after expansion, according to a preferred embodiment of the present invention. 
     
    
     DESCRIPTION OF EMBODIMENTS  
       [0025]     Reference will now be made in detail to preferred embodiments and practices. It is, however, to be understood that reference to any such embodiments and practices is in no way intended to limit the invention thereto. On the contrary, it is intended by the applicants to cover all alternatives, modifications and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims.  
         [0026]     An embodiment of an airbag deployment system according to the present invention for use in restraining lateral movement of a passenger seated in the front of a vehicle is illustrated in  FIG. 1 , and an alternative but also preferred embodiment of an airbag system according to the present invention for use in restraining lateral movement of passengers seated in either the front or back seats of a vehicle is illustrated in  FIG. 2 . As depicted in  FIG. 1 , an interior of a vehicle  10  after inflation of a side impact airbag  12  is shown. The vehicle  10  includes a front seat  14 , a front-side window  18 , a roofline  22 , within which is stored an elongated housing  24 . Airbag  12  is stored in elongate housing  24  prior to deployment. Roofline includes at least a portion of “A” pillar  26 . Also present within roofline  22  is an inflator assembly  28  that ignites and forces an inflation medium into the interior of airbag  12  upon the occurrence of a collision event.  
         [0027]     Most side curtain airbag systems include an attachment point that moves along a track. In the undeployed state, the attachment is at the top of the roofrail, in either the A, B, or C pillar. When the bag deploys, the attachment moves to the bottom of the track, approximately even with the bottom of the side windows. This movement may be caused by the inflating bag, by a spring, or other mechanical device. Thus, the invention may apply to a non-fixed or a fixed attachment. Also for side curtains, there may be multiple fixed attachments along the top of the bag. Since the slits allow the bottom of the bag to move independently of the top, these attachments are not affected.  
         [0028]     Airbag  12  is stored in housing  24  until a collision event occurs. Then airbag  12 , at the start of inflation, forces itself out of housing  24  by the sudden increase in its internal pressure, fully inflates, contracting as it does, and then slowly deflates. In  FIG. 1 , airbag  12  is shown deflated after inflation. Airbag  12  is attached to vehicle  10  by attachment points  30 ,  32 , at its opposing ends. These attachment points  30 ,  32 , define a line  34  therebetween. A series of slits  36  is formed in airbag  12  that are oriented approximately perpendicular to line  34  to the inflation medium. Preferably slits  36  are arranged in plural rows; most preferably, slits  36  are staggered, with respect to slits  36  from an adjacent row, in a pattern similar to that used when laying bricks. The length of slits  36  is preferably longer than the distance between rows of slits  36 .  
         [0029]      FIG. 2  illustrates a similar vehicle  40  equipped with a side curtain airbag  42 . Vehicle  40 , much like vehicle  10 , has a front seat  44 , a back seat  46 , a front-side window and a back-side window (not visible through airbag  42 ), a roofline  52 , within which is stored an elongated housing  54 . Airbag  42  is stored in elongated housing  54  running from the “A” pillar  56  to the “C” pillar  58  of vehicle  40 . Side curtain airbag  42  includes a panel  60  with a bottom edge  62  carrying an inflatable structure  64  similar in construction and operation to side impact airbag  12 . As illustrated, Panel  60  is an inflatable panel with several passages  66  for receiving an inflation medium. A nozzle  68  in fluid communication with inflatable structure  64  and panel  66 , is used to fill passages  64  with inflation medium from an inflation assembly  70 . Nozzle  68  may also be carried by inflatable structure  64  or two nozzles  68  may be carried by airbag  42 , one for inflatable structure  64  and one for panel  66 .  
         [0030]     As with airbag  12 , airbag  42  is stored in housing  54  until a collision event occurs, whereupon airbag  42  inflates. Airbag  42  is shown in  FIG. 2  after inflation in the post-collision, deflated condition.  
         [0031]     Airbag  42  has two attachment points  72 ,  74 , at opposing sides of inflatable structure  64 . Attachment points  72 ,  74 , define a line  76  therebetween. Along inflatable structure  64  are slits  78  that are oriented generally perpendicular to line  76 . Each slit  78  is seamed to be impermeable to the inflation medium. Preferably, there are plural rows of slits  78  and most preferably, as in airbag  12 , slits  78  in one row are staggered with respect to slits in an adjacent row in a typical brick pattern. As in airbag  12 , slits  78  in airbag  42  are preferably longer than the distance between adjacent rows of slits  78 .  
         [0032]     The present invention may be used either as a side impact airbag  12  or as the inflatable structure  64  along bottom edge  62  of a side curtain airbag  42  in the same manner as conventional side impact and side curtain airbags. Whether as an airbag  12  or part of airbag  42 , the present invention employs the same types of materials and similar methods of fabrication. The difference between airbags according to the present invention and prior art airbags is in the structure that allows a given length of airbag material to be expanded so that it can be attached to attachment points  72 ,  74 , and stored in housing  54  prior to use so that, when inflated, its tension increases significantly, particular on small volumes of inflation medium.  
         [0033]     Referring now to  FIGS. 3A, 3B  and  3 C, there is shown an airbag  80  according to the present invention prior to storing in a housing, partially folded and expanded for storage in a housing, and inflated, respectively. Airbag  80  has opposing points of attachment  82 ,  84  that define a line  86  therebetween. Airbag  80  has plural slits  88  formed therein and oriented to be perpendicular to line  86 . Slits  88  are arranged in rows and the slits  88  of each row are staggered with respect to an adjacent row, as will be described in more detail below.  
         [0034]     Each slit  88  is surrounded by a seam impermeable to the inflation medium and is preferably longer than the width of the inflatable chamber between each row of slits  88 . Preferably airbag  80  is made on a weaving machine with a jacquard head; however, the present airbag  80  may also be made using flat fabric that is cut and sewn.  
         [0035]     When airbag  80  is stretched along line  86 , slits  88  open so that airbag  80  expands along line  12  by a distance A. Distance A is a function of the number and length of slits  88 . Without slits  88 , airbag  80  would not expand to the same extent. The length of airbag  80  when fully expanded can reach from one attachment point to another along the roofline of vehicle and be folded into housing that houses airbag  80  prior to deployment.  
         [0036]     The effect of expanding an inflatable airbag according to a preferred embodiment of the present invention is seen by comparing the portion of such a structure illustrated in  FIGS. 4A and 4B . An inflatable structure  100  has slits  102  formed therein. Each slit  102  is seamed to be impermeable against leakage of the inflation medium. Slits  102  are arranged in rows. As illustrated, the first row  104  has three slits  102  followed by an adjacent row with two slits  102 , and then a next row  108  with three slits  102  and so on. When inflatable structure  100  is expanded by applying opposing forces to its attachment points (not shown in  FIGS. 4A and 4B ), it expands or stretches as slits  102  change shape, first opening and then closing in an orientation aligned in the direction of the opposing forces.  
         [0037]     In the event of an accident, airbag  80  will begin to inflate, forcing itself from its housing as it expands in width and shortening its length as it does so. On inflation, the pressure in the bag will tend to force the bag to assume its original pre-stretched configuration, significantly reducing its length and increasing its tension. Because it is fixed to the vehicle at attachment points  82 ,  84 , it cannot shorten once it is free of its housing into which it had been stuffed prior to inflation. Rather, from the time shortly after it exits the housing, it can only increase in tension as inflation medium swells the interior of airbag  80 . Furthermore, this tension will have increased significantly and quickly, even at low volumes and pressure. Thus airbag  80  will provide restraint more quickly than airbags that do not achieve the same tension given a flow of inflation medium. Correspondingly, the present invention may provide sufficient tension and corresponding restraint at internal pressures that are lower than conventional airbags so that pressure can be limited. Lower internal pressures provide gentler and safer cushioning.  
         [0038]     Those skilled in the art of airbag design for passenger restraints will appreciate that many substitutions and modifications may be made to the preferred embodiments described herein without departing from the spirit and scope of the present invention, which is defined by the appended claims.