Abstract:
Highly-deformable sealing strips integrating with fabric assemblies (principally of airbags) are detailed. The strips reduce gas leakage from occurring. They also function as mechanical reinforcements of the assemblies.

Description:
REFERENCE TO PROVISIONAL APPLICATION  
       [0001]     This application is based on and hereby refers to U.S. Provisional Patent Application Ser. No. 60/693,725, filed Jun. 24, 2005, entitled “Sealing and Reinforcement Strip for Airbag Assembly Joints,” the entire contents of which are incorporated herein by this reference. 
     
    
     FIELD OF THE INVENTION  
       [0002]     This invention relates to materials for sealing and reinforcing other materials and particularly, although not necessarily exclusively, to highly-deformable strips adapted to seal and reinforce seams and peripheries of vehicle airbags.  
       BACKGROUND OF THE INVENTION  
       [0003]     Conventional airbags frequently comprise multiple panels of fabric cut to particular patterns and assembled at their peripheries by seams. Some such fabric panels are uncoated. Others, including versions provided by the assignee of this application, may be coated with highly-impermeable silicone to reduce leakage of inflation gas through the panels. Reducing gas leakage from an airbag greatly enhances its performance, as pressure within the bag from the gas-generation event may be sustained for longer periods.  
         [0004]     U.S. Pat. No. 6,364,356 to Keshavaraj details methods of forming an exemplary inflatable airbag. Panels may be adhered together by welded seams, with the welding purportedly “reducing air or gas permeability.” See Keshavaraj, Abstract, 11. 5-6. As described in the Keshavaraj patent, “a single stitched (sewn) seam located adjacent” two welded seams may “provide increased tear strength” for the combined seam structure. See id., col. 6, 11. 8-9 (numeral omitted).  
         [0005]     Although utilizing multiple seams for inflatable fabrics may reduce gas permeability of the panels, significant gas leakage may continue to occur. Likewise, although employing multiple seams may provide greater tear strength, as indicated in the Keshavaraj patent, substantial reinforcement of seams may continue to be required. Accordingly, need exists for materials adapted to provide reduced permeability of, and greater strength to, seams of fabric panels.  
       SUMMARY OF THE INVENTION  
       [0006]     The present invention supplies such materials. In particular, the invention provides highly-deformable sealing strips integrating with fabric assemblies to reduce gas leakage from occurring. The strips also function as mechanical reinforcements of the assemblies. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]      FIG. 1  illustrates a fabric strip with straight gain.  
         [0008]      FIG. 2  illustrates a bias strip of fabric.  
         [0009]      FIG. 3  illustrates a textile structure having low extensibility in the warp direction and high deformation in the weft direction.  
         [0010]      FIG. 4  illustrates a sheet of strips.  
         [0011]      FIG. 5  illustrates positioning of a strip between two panels of an airbag.  
         [0012]      FIG. 6  illustrates positioning of a strip of the invention between two panels of an airbag.  
         [0013]      FIG. 7  illustrates an exemplary process for directly extruding a strip of the invention (with silicon on both sides of the strip).  
         [0014]      FIG. 8  illustrates an exemplary process for extrusion lamination of a sheet of strips of the invention and cutting the sheet into strips (with silicon on one side).  
         [0015]      FIG. 9  illustrates a discontinuous (batch) vulcanization process using a flat press.  
         [0016]      FIG. 10  illustrates a continuous vulcanization process using a conveyor belt.  
         [0017]      FIG. 11  illustrates a standard assembly of airbag panels by a seam.  
         [0018]      FIG. 12  illustrates positioning a strip of the invention internal to the airbag, with a seam.  
         [0019]      FIG. 13  illustrates positioning a strip of the invention internal to the airbag, without a seam.  
         [0020]      FIG. 14  illustrates positioning a strip of the invention external to the airbag, straddling a seam.  
         [0021]      FIG. 15  illustrates positioning a strip of the invention external to the cushion, without a seam.  
         [0022]      FIGS. 16-17  illustrate positioning strips of the invention internal to the cushion, without seams. 
     
    
     DETAILED DESCRIPTION  
       [0023]     Depicted in  FIG. 1  is an exemplary sealing strip  10  of the type currently used in textile constructions of airbags. Strip  10  typically is woven and advantageously may resist processing tension in the warp direction. However, strip  10  often is not highly deformable in the weft direction and thus is unable to conform optimally to geometrically-complex assembly joints.  
         [0024]     Presently, therefore, when assembly joints are complex geometrically, strip  20  ( FIG. 2 ) sometimes is used instead. Strip  20  may be cut along the fabric bias to improve deformability in the weft direction. Doing so increases extensibility in the warp direction, however, increasing difficulties when strip  20  is sewn in place. In particular, use of strip  20  at times may cause needle jamming, folds, puckers, or other abnormalities in the associated airbag.  
         [0025]      FIG. 3  shows strip  30  of the present invention. Strip  30  supplies high deformability in the weft direction without significantly increasing extensibility in the warp direction. Strip  30  preferably is comprised of textile structures made by knitting, warp knitting, braiding, or weaving, although other construction processes may be employed instead.  
         [0026]     Structures of strip  30  also may be composites whose length is inextensible so as to limit deformation in the assembly process. Strips  30  additionally may be cut from a sheet  40 , as shown in  FIG. 4 . Regardless, however, strips  30  may be configured and structured (including via the nature of the threads or fibers employed and the density of the weave, for example) as appropriate for the type of assembly joint to be sealed and to facilitate penetration of adhesives.  
         [0027]     Currently, liquid curable silicone polymers sometimes are applied to seams to provide seals. Alternatively, hot (EVC) or cold (EVF) curable elastomeric silicone adhesives may be employed in conventional designs. The former provides no mechanical reinforcement of the sealed joint, while the latter may tend to release toxins, volatile compounds, or odorants over time. As a consequence, the latter may be incompatible for use within, for example, passenger compartments of motor vehicles.  
         [0028]      FIG. 5  illustrates strip  20  intended to seal a joint comprising airbag panels  44  and  48  assembled by seam  52 .  FIG. 6 , by contrast, details strip  30 ′ as coated by silicone adhesives of the present invention. Such adhesives enhance bonding of strip  30 ′ and panels  44  and  48  and decrease gas-permeability of the joint.  
         [0029]     Silicone adhesives of the present invention may be curable (vulcanizable) by polyaddition reactions (catalysis by platinum or other catalytic metals) so as to permit strong bonding and avoid noxious chemical emissions or odors. Blowing agents may be utilized in formulating the adhesives so as to create a cellular structure (such as that shown in  FIG. 6 ) that expands the area occupied by strip  30 ′ during vulcanization of the joint. Chemical coupling agents or adherence accelerants in the form of organic compounds of titanium or silanes, for example, may also be included.  
         [0030]     To counteract existing limitations in coating base fabrics with elastomer adhesives, the direct extrusion process depicted in  FIG. 7  may be used.  FIG. 7  depicts machinery  56 , which comprises extruder  58  into which silicone adhesive  60  of the present invention may be input via feeder  62 . Machinery  56  also may comprise die  64  including slot  66 .  
         [0031]     When machinery  56  operates, adhesive  60  may be extruded into strips having width essentially identical to that of strip  30 . Meanwhile, strip  30  may be unwound from a roll or otherwise fed into slot  66  through die  64 . Within die  64 , extruded adhesive  60  is applied to both upper side  68  and lower side  70  of strip  30  to form composite strip  30 ′. If desired, strip  30 ′ may then be wound into rolls as shown in  FIG. 7 . This process allows for simultaneous coating of both upper and lower sides  68  and  70  of strip  30  but does not permit simultaneous processing of multiple strips  30 .  
         [0032]      FIG. 8  illustrates an alternative process for creating strips  30 ′. Extruder  74  receives adhesive  60  through feeder  78  and extrudes sheets of adhesive  60  onto roller  82 , where it may be applied to one side of a sheet of strips  30  being unwound from a roll. Pressure from rollers  82  and  86  cause the application, with regulation of the gap between rollers  82  and  86  and pressure applied by roller  86  helping control thickness of the result and penetration of adhesive  60  into the textile structure of strip  30 . Coating of the other side of the sheets of strip  30  may occur in a second pass. Thereafter, the sheet may be cut continuously in the warp direction into strips  30 ′, each of which may be wound onto a spool for use directly in an industrial process of airbag wall joint assembly. Either process of  FIG. 7  or  FIG. 8  may permit application of adhesive  60  to reach a thickness of approximately 100 μm with precision of approximately 10 μm onto strips  30  with individual widths of a few millimeters to a few centimeters.  
         [0033]      FIGS. 12-17  illustrate various placements of strip  30 ′. If, for example, reinforcement within an airbag is important, strip  30 ′ may be applied between airbag panels  44  and  48  prior to sewing of seam  52 . Such placement is shown in  FIGS. 12-13 . By contrast, external reinforcement of an airbag may occur by attaching strips  30 ′ during or after sewing of seam  52  into panels  44  and  48  (as depicted in  FIG. 14 ). When assembling a cushion, strip  30 ′ may be applied in an angular fashion (as shown in  FIGS. 15-17 ) either within ( FIGS. 16-17 ) or outside ( FIG. 15 ) the cushion. In each of these cases, vulcanization of adhesive  60 , and thereby bonding of strip  30 ′ to panels  44  and  48 , may be achieved through action of temperature and pressure via either or both processes illustrated in  FIGS. 9-10 .  
         [0034]      FIG. 11  illustrates conventional attachment of panels  44  and  48  by seam  52  (i.e. without strip  30 ′). As shown in  FIG. 12 , strip  30 ′ may provide mechanical reinforcement of the airbag by the strength of the bonds between adhesive  60  and respective interior surfaces  90  and  94  of panels  44  and  48 . Mechanical resistance of the structure of strip  30  from which composite strip  30 ′ is formed additionally may provide reinforcement to the airbag.  
         [0035]     In each of  FIGS. 13 and 15 - 17  is depicted an assembly lacking any seam  52 . In these joints, strip  30 ′ itself adequately attaches panels  44  and  48  so that no seam  52  is necessary. Of course, such a seam  52  may be added if desired, however.  FIG. 14 , finally, details strip  30 ′ straddling seam  52  and bonded both to the seam  52  and external surfaces  98  and  102  of respective panels  44  and  48 . In this configuration, strip  30 ′ well limits gas leaks when the airbag is pressurized.  
         [0036]     The foregoing is provided for purposes of illustrating, explaining, and describing embodiments of the present invention. Modifications and adaptations to these embodiments will be apparent to those skilled in the art and may be made without departing from the scope or spirit of the invention.