Abstract:
A coated airbag is provided. In another aspect, a method of extrusion coating an air impermeable material onto a one-piece woven airbag fabric is employed. Another aspect preheats a fabric such that the fabric remains hot during a coating application thereon. Furthermore, a machine for making and coating an airbag fabric is also provided.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 61/145,202, filed on Jan. 16, 2009, which is incorporated by reference herein. 
     
    
     BACKGROUND 
       [0002]    The present application pertains generally to coated fabrics and more particularly to coated airbags for automotive vehicles. 
         [0003]    Simple cut and sew airbags have been commonly used for front and side passenger protection in automotive vehicles. Many modern side curtain airbags, however, must protect the passengers during a vehicular rollover situation and thereby must retain the inflation gas within the airbag for an elongated period of time. Traditional cut and sew airbags have a relatively simple to manufacture fabric construction but often require expensive coatings applied in a relatively complex manner in order to overcome undesired inflation gas leakage through the sewn seams when used for side rollover airbags. Examples of such traditional coated, cut and sew airbags can be found in U.S. Patent Publication No. 2001/0049243 entitled “Lightweight, High Strength Coated Fabric” invented by Crouch et al., and PCT Patent Publication No. WO 2007/070465 entitled “Thermoplastic Coated, Heat-Sealed Airbag” listing Sescourka et al. as inventors. Both of these patent publications are incorporated by reference herein. 
         [0004]    One-piece woven (“OPW”) airbags have also been employed for side curtain airbags. Examples of such OPW airbags can be found in the following U.S. patents and patent publications: U.S. Pat. No. 5,685,347 entitled “Circular Air Bag Made of Two Simultaneously Woven Fabric” which issued to Graham et al. on Nov. 11, 1997; 2005/0161919 entitled “Airbag and Method of Producing an Airbag” invented by Berger et al.; and 2002/0140218 entitled “One-Piece Woven Airbag” invented by Beasley, Jr. These patents and publications are all incorporated by reference herein. A knife-over-roll coating process has been used for some conventional OPW airbags, however, this undesirably allows for considerable thickness variations in the coating and can be a costly process. Furthermore, some conventional OPW airbags have used a laminated film approach as an alternative to the knife-over-roll coating process, but this tends to be undesirably expensive and creates difficult to fold stiffness in the final airbag. It is noteworthy, however, that U.S. Pat. No. 7,179,762 entitled “Motor Vehicle Air Bag and Fabric for Use in Same,” invented by Beasley, Jr., states at the top of column 2 that “it is relatively difficult to coat a one-piece curtain” airbag as compared to simpler cut and sew fabric constructions. 
       SUMMARY 
       [0005]    In accordance with the present invention, a coated airbag is provided. In another aspect, a method of extrusion coating an air impermeable material onto a one-piece woven airbag fabric is employed. Another aspect preheats a fabric such that the fabric remains hot during a coating application thereon. Furthermore, a machine for making and coating an airbag fabric is also provided. In yet another aspect, a vehicular airbag has a one-piece woven construction with an outer coating of high molecular weight, thermoplastic material. 
         [0006]    The present coated airbag, machine and methods are advantageous over traditional constructions, machines and processes, since the present airbag employs considerably less expensive coating materials while achieving superior performance. The materials employed for the present coating (and entire airbag) are also recyclable, thereby reducing scrap costs, and the coating is easily applied in a uniformly thick manner that is independent of fabric weaving variations. Additionally, lighter weight coating materials are used in the present system, especially as compared to more expensive silicone materials, but without sacrificing performance. This also allows for a reduced packaging size for the final airbag in the vehicle. Additional advantages and features of the present invention will become apparent from the following description and appended claims, taken in conjunction with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  is a perspective view showing a coated airbag, in an inflated condition, employed in an automotive vehicle; 
           [0008]      FIG. 2  is a diagrammatic perspective view showing the equipment used to make the coated airbag; 
           [0009]      FIG. 3  is a diagrammatic cross-sectional view, taken along line  3 - 3  of  FIG. 1 , showing an exemplary one-piece woven fabric, prior to coating; 
           [0010]      FIG. 4  is a diagrammatic side view showing the equipment used to make the coated airbag; and 
           [0011]      FIG. 5  is a diagrammatic cross-sectional view of the airbag, after coating. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0012]      FIGS. 1 ,  3  and  5  show an exemplary airbag  11  employed in an automotive vehicle  13 . Preferably, this airbag is of a side curtain airbag variety which is suitable for retaining a majority of its inflation gas for at least five seconds from full inflation, to meet suitable vehicular rollover requirements. More particularly, airbag  11  includes a one-piece woven fabric  14 , having a single layer seam  15  integrally woven to multiple fabric layers  17  surrounding a gas inflation chamber  19  therebetween. In the exemplary embodiment, both 3×3 woven baskets  21  and 2×2 woven baskets  23  are employed in the single layer seam  15  between the pair of double layer inflation chambers  19 . 
         [0013]    The OPW fabric fibers are preferably made of nylon 6/6, although it is alternately envisioned that a high tenacity polyester material can be employed. OPW fabric  14  is woven on a programmable jacquard loom  25  (see  FIG. 4 ). Exemplary jacquard looms are disclosed in U.S. Pat. No. 4,440,196 entitled “Double Open-Shed Jacquard Machine for the Lifting of Warp Yarns of a Loom” which issued to Arvai on Apr. 3, 1984, and U.S. Pat. No. 6,945,282 entitled “Method and Device for Forming a Shed in a Weaving Machine” which issued to Gendelman et al. on Sep. 20, 2005; both of which are incorporated by reference herein. 
         [0014]    Referring to  FIGS. 4 and 5 , a coating  31  is located on each outside surface of the fabric portion of airbag  11 . Coating  31  includes an inner adhesive material  33 , penetrating into and bonded with the fabric fibers, and an outer air impermeable and leak-resistant material  35  bonded to adhesive material  33 . Adhesive material  33  is preferably a thermoplastic material such as an ethylene copolymer, exhibiting a molecular weight range that is suitable for molten extrusion. One such adhesive material is the Entira™ Coat 100 material which can be obtained from E.I. du Pont de Nemours and Company, Inc. The preferred air impermeable material is a thermoplastic polyurethane (“TPU”) polymer which has a molecular weight within a range of 100,000-200,000. The ultimate elongation percentage of the preferred air impermeable polymeric material is greater than 300, and more preferably within the range of 500-700. Furthermore, the preferred tensile strength for the air impermeable material is within the range of 30-50 MPa. Suitable air impermeable polymeric materials can be obtained from Lubrizol Advanced Materials, Inc. as Estane® 58300 and 58315 materials. The phrase “air impermeable” indicates that the material resists flow of the inflation gas therethrough after final solidification of the coating materials, however, it does not require absolute impermeability. The air impermeable polymeric material and the adhesive material are preferably neither water-based nor solvent-based given their desired high molecular weights. Solubility of such materials is negligible and the materials are formed into a film type of coating by melting the materials and working with them as a liquid in an approximately 100 percent solids molten condition. 
         [0015]      FIGS. 2-4  show a machine  51  used to make coated airbag  11 . Machine  51  includes a coextruder  53  which has two extruder sections  55  with corresponding feed hoppers  57 . Rotating screws  59  are located within each heated barrel  61 . A pair of pipes or a manifold connects tips of both extruder barrels  61  to a combining block  63 . Another pipe  65  or suitable conduit connects an end of combining block  63  to an elongated die  67 . Die  67  has a laterally elongated exit slot downwardly facing toward fabric  14 . 
         [0016]    Fabric  14  is woven on jacquard loom  25  and then it is rolled up and transported to the coating line. It is then unrolled as it is fed into machine  51 . Fabric  14  initially contacts against a lead-in roll  81 . A pair of infrared heaters  83  and  85  preheat the adjacent outer surface of fabric  14  to a fabric temperature within the range of 100-180° C., and more preferably at about 150° C. The preheating advantageously delays solidification of the coating in order to allow deeper fabric penetration. Moreover, infrared heaters are ideally suited to allow tight packaging in their placement near coating die  67 . 
         [0017]    The hot fabric is then coated with the adhesive and air impermeable materials in a curtain-type coating  31  essentially along the full width of the fabric. The outer surface of fabric  14  is still hot, at a temperature of at least 100° C., where coating  31  is applied onto the fabric&#39;s outer surface, as this preheating will significantly improve adhesion and coverage of the coating. A dwell time between the fabric preheating step and the coating application is 10 seconds or less, and preferably 5 seconds or less, given the disclosed fabric travel speeds in the coating machine. Thus, downstream infrared heater  85  is 3 meters or less from coating die  67 , and more preferably 1.5 meters or less, for 0.3 meters per second fabric speed. For faster fabric speeds, however, the heater to die distance can be greater (but with the same dwell time) as long as the fabric is sufficiently hot when the coating is applied. 
         [0018]    Coating  31  is applied in a generally uniform thickness by die  67  onto fabric  14 , exiting die  67  at about 20 thousandths of an inch thick while still molten. After contacting the surface of fabric  14  and subsequent solidification, the coating preferably has a total thickness within the range of about 1-6 thousandths of an inch and more preferably at about 2 thousandths of an inch, approximately half of which is the adhesive and half of which is the air impermeable material. The final solidified coverage of coating  31  onto fabric  14  is preferably within the range of 30-90 grams per square meter and more preferably at approximately 50 grams per square meter. The thermoplastic material is applied to the fabric at a temperature within the range of about 200-250° C. and preferably within the range of 204-216° C. Furthermore, fabric  14  is moving through machine  51  at about 0.3-1.6 meters per second and preferably 1 meter per second. Coating  31 , however, is being extruded from die  67  onto fabric  14  at a slower speed, at approximately a 10:1 ratio of fabric-to-coating speed, therefore the fabric draws the coating in a thinning manner as it is being applied. Moreover, coating  31  is applied on the fabric such that the adhesive and air permeable materials preferably remain in two generally distinct layers, but with penetration of at least the adhesive into the outer fabric material. 
         [0019]    A steel backing roll  87  controls the temperature of a contacting rubber covered roll  89 . Fabric  14  is then pulled between rubber roll  89  and an adjacent chill roll  91 . Chill roll  91  includes a set of closed loop, recirculating air/liquid cooling lines therein. Coating  31  remains molten when it and the fabric  14  are compressed between rolls  89  and  91 . The elastomeric and cushioned rubber surface of roll  89  is compressible enough to absorb the thickness variations of the OPW weaving pattern of fabric  14  while maintaining the uniformity of the coating thickness against chill roll  91 . Thus, this process is different than traditional calendaring. In other words, this combining station includes rubber roll  89  pressing against the backside of fabric  14  and the relatively large diameter steel, chill roll  91  that presses the molten coating  31  into the other fabric surface and cools the coating to solidify it. The two rolls are independently temperature controlled. Additionally, chill roll  91  imparts the mirror image of its own surface finish or texture into the coating surface (i.e., embossing) before the coating layers are cooled enough to be removed from the cooling roll surface. 
         [0020]    Thereafter, the coated fabric moves around a stripper roll  93 . The resulting one-side coated fabric is rolled up and then fed back into the beginning of machine  51  in an inverted manner, such that the opposite outside surface is upwardly facing for subsequent preheating, coating and solidification. The fully coated fabric is subsequently moved to a cutting station where each individual airbag is laser cut therefrom. 
         [0021]    In greater detail, the process flow for the coextrusion coated fabric of the present application is performed in two simultaneous flows: one for the coating material and one for the fabric itself. The process flow of the coating material is further described as follows:
       1. Plastic pellets of air impermeable TPU material  35  and adhesive material  33  are pneumatically conveyed from shipping containers to their respective feed hoppers  57  mounted above a back of extruders  55 .   2. Pellets are fed into the first flight of rotating screws  59  of extruders  55  which are tightly fitted in the heated steel barrels  61 .   3. The pellets are melted, deaerated and brought to a high pressure by a progressive change in the pitch and depth of the extruder flights of screws  59 .   4. The resulting molten flow exits the tips of the extruders  55  at a rate that is precisely controlled by the speed of the rotating extruder screws  59 .   5. The above process is carried out simultaneously in two extruders; one for adhesive layer  33  of coating  31  and one for the outer exposed, air impermeable TPU layer  35  of the coating.   6. The flow from the two extruders  55  is fed to combining block  63  and then into extrusion die  67  that shapes the molten flow into a wide, thin 2-layer curtain with the adhesive material on one side of the curtain and the topcoat, air impermeable material on the other side of the curtain.   7. Extrusion die  67  and its curtain of extrudate are positioned immediately above the path of moving fabric  14  to allow the application of a film of plastic coating  31  on the upward facing surface of the moving fabric.       
 
         [0029]    The previously disclosed example is employed for a side curtain airbag having an OPW fabric construction. Nevertheless, various features from the present application may be used with front or seat mounted airbags, cut and sew airbags, or even seat belt webbing, although many advantages of the present application may not be realized. Furthermore, it is alternately envisioned that the adhesive and air impermeable materials can be applied in a series rather than previously disclosed parallel manner by separate and spaced apart extrusion machines and dies, however, various advantages of the present application may not be achieved. Moreover, other heaters beyond infrared heaters, may alternately be employed, however, other heaters may be larger and have inferior performance. Additionally, certain aspects of the present application may be used without an adhesive layer if a suitable air impermeable material is otherwise used. While various materials, weaving patterns and exemplary characteristics have been disclosed, it should be appreciated that various other materials, patterns and characteristics can be employed. It is intended by the following claims to cover these and any other departures from the disclosed embodiments which fall within the true spirit of this invention.