Airbag weaving on a water-jet loom using yarns
FIELD OF THE INVENTION 
     The present invention relates generally to the construction of airbags and airbag fabrics for use in restraining vehicle occupants during collisions and more particularly to airbags formed from water-jet woven fabrics using unsized yarn woven at high densities. An apparatus and process for forming the fabrics for use in such airbags are also provided. 
     BACKGROUND 
     Airbag equipment installed on a fixed portion of an automobile or an airplane body in front of a seated occupant plays an important role in the protection against injury arising due to collision with the fixed portion of the car body or airplane during an accident. Airbags may be produced in a number of manners and from a number of different materials. However, airbags are typically formed, at least in part, from some type of woven textile material. Such textile materials are disclosed in U.S. Pat. Nos. 5,277,230 to Sollars, Jr. issued Jan. 11, 1994; 5,259,645 to Hirabayashi, et al. issued Nov. 9, 1993; 5,110,666 to Menzel, et al. issued May 5, 1992; 5,073,418 to Thornton, et al. issued Dec. 17, 1991; 5,011,183 to Thornton, et al. issued Apr. 30, 1991; 4,921,735 to Bloch issued May 1, 1990; and 3,814,141 to Iribe, et al. issued Jun. 4, 1974. The teachings of all of which are incorporated herein by reference. 
     Historically, fabrics for use in vehicle airbags have typically been formed using conventional Rapier weaving machines wherein the pick yarn is drawn mechanically across the warp. Such weaving practices have been successful in producing the high weave density, i.e. pick count, which is desired for structural stability in the fabric used to withstand inflation and collision forces when the airbag is deployed during an accident. Unfortunately, typical Rapier weaving machines are significantly slower than alternative weaving technology such as water-jet weaving. 
     In water-jet weaving, the pick yarn is drawn through the shed of the warp yarns by means of a stream of water which represents a much faster method of insertion than the mechanical Rapier. Heretofore, airbag fabrics incorporating yarn of approximately 420 denier have been woven on water-jet weaving machines at a maximum weave density of approximately 46×46 (warp×fill). As will be appreciated by those with skill in the art, this construction is lighter than the typical 49×49 fabric woven on conventional Rapier weaving machines. In order to compensate for the lower weave density achievable on water-jet weaving machines, the weaving has been performed using yarns having high breaking tenacities so as to provide improved strength in the final fabric despite the lighter weave construction. 
     As will be appreciated by those of skill in the art, yarns of high tenacity may require slashing with a chemical compound referred to as a sizing compound to enhance the mechanical integrity of the higher tenacity yarns during weaving. When weaving fabric for airbags, the size which is used is typically a polyacrylic acid although other polymers such as polyvinyl alcohol, polystyrene, and polyacetates may likewise be utilized. While the sizing compound is typically effective in enhancing the mechanical integrity of the high tenacity yarn, such sizing also tends to enclose yarn oils which may not be compatible with polymeric compounds used for coating the fabric prior to its formation into an airbag structure. Accordingly, the practice prior to the present invention has been to eliminate the sizing compound as well as the enclosed yarn oils by the scouring and drying of the fabric prior to effecting any coating operation. 
     As will be recognized, the addition of scouring and drying operations may tend to increase the cost for the overall production of fabric. Thus, it is of useful benefit to provide a fabric which may be used in an airbag and which is woven on a water-jet loom at high weave constructions such as are available on conventional Rapier machines while avoiding the need to use high tenacity yarns with sizing compounds applied thereto. Such an improvement permits the complete elimination of scouring the fabric to remove enclosed yarn oils since the oils are removed within the water stream during the weaving process itself. 
     SUMMARY OF THE INVENTION 
     In light of the foregoing, it is a general object of the present invention to provide an airbag and airbag fabric for use in protecting vehicle occupants during a collision, comprising at least a portion of fabric woven by means of water-jet weaving at a weave construction comparable to that available by traditional Rapier weaving machines. 
     In that respect, it is an object of the present invention to provide an airbag and airbag fabric comprising at least a portion of woven fabric formed by means of water-jet weaving wherein such woven fabric has a weave construction of greater than 47 threads per inch in both the warp and the fill directions. 
     It is a related object of the present invention to provide an airbag and airbag fabric comprising at least a portion of woven fabric formed by means of water-jet weaving from yarn of between about 380 denier and about 460 denier wherein such yarn does not include a chemical size coating prior to weaving. 
     It is a further related object of the present invention to provide a process for forming an airbag and fabric comprising at least a portion of a woven fabric wherein such woven fabric is woven by means of water-jet weaving of yarn having no chemical size coating at a weave construction of at least 47×47 threads per inch in a plain weave with no scouring required between weaving such fabric and applying a coating thereto prior to forming such fabric into the airbag. 
     Accordingly, it is a feature of the present invention to provide woven fabric formed by means of water-jet weaving from unsized yarn at a weave density of at least 47 threads per inch and preferably at a plain weave density of between about 49 and about 52 threads per inch for both the warp and the fill. 
     It is a subsidiary feature of the present invention to provide a woven fabric for use in an airbag formed from unsized nylon yarn of between about 380 and 460 denier or greater in a plain weave at a weave density of greater than 47×47 picks per inch. 
     It is yet a further subsidiary feature of the present invention to provide a method for forming an airbag and airbag fabric including at least a portion of woven fabric woven by means of a water-jet weaving apparatus from unsized yarn at a weave density of greater than 47 threads per inch in both the warp and the fill, wherein the process does not require scouring of the woven fabric prior to application of any coating prior to assembly of the airbag. 
     In accordance with one aspect of the present invention, a water-jet woven fabric of high weave density for use in an airbag is provided. The water-jet woven fabric preferably comprises a plurality of warp yarns of between about 380 denier and about 460 denier nylon interwoven in a plain weave with a plurality of fill yarns of between about 380 denier and about 460 denier nylon such that the weave density achieved in the fabric is greater than 47  threads per inch in both the warp and the fill direction. Both the warp and the fill yarns are preferably flat nontextured yarns free of chemical sizing compounds prior to weaving such that no additional scouring step is required to remove yarn oils in the event that a coating is to be applied to the fabric. 
     In accordance with a related aspect of the present invention, an airbag for use in conjunction with airbag equipment in a vehicle is provided comprising an inflatable fabric wherein the inflatable fabric includes at least a portion of woven fabric formed by a plurality of warp yarns of between about 380 denier and about 460 denier nylon interwoven in a plain weave with a plurality of fill yarns of between about 380 denier and about 460 denier nylon by water-jet weaving such that the weave density achieved in the fabric is greater than 47 threads per inch in both the warp and the fill direction. Both the weft and the fill yarns are preferably nontextured yarns free of chemical sizing compounds prior to weaving. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an overview perspective of a water-jet weaving machine illustrating several machine modifications believed to enable the production of fabrics having high weave densities on such machines; 
     FIG. 2 illustrates equipment modifications to the weft cutting and catch selvage take-off for the right selvage waste removal of the water-jet weaving machine illustrated in FIG. 1; 
     FIG. 3 is a side profile schematic of the weaving machine shown in FIGS. 1 and 2 including the off-loom take-up assembly therefor; 
     FIG. 4 is a cut-away side view taken generally along line 4--4 of FIG. 2 and illustrating the high-profile bar temple assembly; 
     FIG. 5 shows a plain weave fabric formed according to the method of the present invention; 
     FIG. 6 is a schematic gross-section view of a typical airbag installation mounted in a steering wheel; and 
     FIG. 7 is a schematic view showing the airbag of FIG. 6 in an expanded condition. 
    
    
     While the invention may be described and disclosed in connection with certain preferred embodiments and procedures, it is in no way intended to limit the invention to any such specific embodiments. Rather, it is specifically intended to cover all embodiments and modifications as may fall within the true spirit and scope of the invention as defined by the claims appended hereto. 
     BRIEF DESCRIPTION OF PREFERRED EMBODIMENTS 
     Now looking to the FIGURES wherein like reference numerals denote like components in the various views, in FIG. 1 there is shown a water jet weaving machine 10 such as a Nissan type LW541  or LW542 available from the textile machinery division of the Nissan Motor Company Ltd. including a base structure 11, for use in delivery of a plurality of warp yarns 12 from a warp beam 14. As illustrated in FIG. 1 and FIG. 3, the warp yarns 12 are passed over a tensioning roll apparatus 18 which is used to adjust the warp tension as described more fully below. 
     As will be appreciated, approximately half of the warp yarns 12 are passed through a first harness mechanism 24 and approximately half of the warp yarns 12 are passed through a second harness mechanism 26. As best illustrated in FIG. 3, the first and second harness mechanisms 24, 26 may be moved up and down with respect to one another so as to adjust the opening or &#34;shed&#34; between the two sets of warp yarns in an alternating manner. By shifting the respective position of each set of warp yarns, a water-jet nozzle 28 may be used to insert a fill yarn 30 on a periodic basis in the shed between the two sets of warp yarns. By coordinating the insertion of the fill yarn 30 with the reciprocating movement of the first and second harness mechanisms 24, 26 a woven structure with the fill yarn overlying and underlying alternating warp yarns may be achieved. 
     It will be appreciated that once the fill yarn 30 is inserted in appropriate orientation with respect to the warp yarns 12, it is necessary to secure these yarns in place in a relatively secure structure by forcing them against the previously inserted fill yarns by means of a beating process as carried out by a reciprocating reed 31 which separates the warp yarns at the point of fill yarn insertion and beats the fill yarns into place at the bar temple 32 as discussed more fully below in relation to FIG. 4. 
     As will be readily appreciated by those of skill in the art, once the fill yarn is inserted, it must be cut off at the boundary of the fabric being produced and removed along with the selvage waste. As best illustrated by reference to FIGS. 1 and 2, the cutting at both the right and the left sides of the fabric is preferably performed by means of hot knife cutters 34 based on electrical resistance as opposed to mechanical scissors which have heretofore been utilized. The yarn cut is entrained in the catch cord 36 by suction produced behind a catch plate 38 through vacuum line 40 by a suction pump (not shown). The catch cord with the entrained fill yarn is thereafter passed through a twister head 42 for selvage waste accumulation. 
     As indicated previously, it is an object of the present invention to provided a water-jet woven fabric with a high pick count. That is, a high density of yarns in both the warp and the weft direction. Specifically, it is desired to obtain a fabric with a weave density of greater than about 47 threads per inch and preferably between about 48 and 52 threads per inch in both the warp and the fill direction while using yarn of between about 360 and about 460 denier. In one important aspect, it has been determined that increased warp tension beyond that previously used on water-jet weaving machines facilitates in the production of such high weave density fabrics. By way of example only, and not limitation, it has been determined that increasing the warp tensioning from the standard level of about 60 grams per inch to a level of between about 80 and 95 grams per inch is successful in increasing the weave density significantly from the previously achievable upper limit of about 46 threads per inch to a level of between about 48 picks per inch and 52 threads per inch. More specifically, it has been found that increasing the warp tension to a level of about 93 grams per inch yields a weave density of about 51.5 threads per inch. As illustrated in FIG. 3, this warp tension is adjusted by adding or removing warp tensioning weights 43 to a tensioning lever arm 44 which, in turn, increases or reduces the tension on the tensioning roll apparatus 18 previously discussed. 
     As will be readily appreciated by those of skill in the art, a substantial increase in the tension of a large number of warp yarns significantly increases the forces necessary to beat the fill yarn into place. Accordingly, it has been found beneficial to incorporate several further modifications to the water-jet weaving machine as illustrated in FIGS. 1, 2 and 4 to accommodate these higher stresses. In particular, it has been found that the use of a so called high profile bar temple 32 utilizing a chrome or anodized aluminum casing 46 and a nylon threaded rod 48 (FIG. 4) provides the best performance and durability in handling the high warp tension stresses. One bar temple which may be particularly preferred is available from the Lewis P. Batson Company whose address is believed to be 1 Club Road, Box 3978, Greenville, S.C. 29608. 
     The high profile bar temple 32 is preferably supported by a plurality of temple support brackets 52 extending between the breast beam 54 of the weaving machine and a rear support arm 53 of the bar temple 32. As shown, the breast beam 54 is preferably connected to the frame 11 of the weaving machine by a high strength breast plate 56 using connecting pins 58. In the potentially preferred embodiment, the connecting pins 58 will be at least 3/8 inch in diameter so as to prevent deflection during machine beat-up. It is to be noted that it has also been found beneficial to increase the width of the catch plate arm 60 from the standard width of 10 millimeters to a width of about 25 millimeters to contain any potential fill deflection due to insertion through a higher tension warp. 
     It is to be understood that following the beating action by the reed 31 at the bar temple 32, a woven fabric 70 is formed having yarns running in both the warp and the fill direction. In a potentially preferred embodiment, the overall pick density as measured in the fill direction may be substantially equivalent to the warp density measured in the warp direction thus yielding a plain weave as shown in FIG. 5. 
     As indicated previously, in the preferred embodiment, both the warp yarns 12 and the fill yarns 30 will be nonsized. By the term &#34;nonsized&#34; is meant that no sizing compound such as polyacrylic acid, polyvinyl alcohol, polystyrene, polyacetates, starch, gelatin, oil or wax is applied to enhance coherency to the filament. By way of example, and not limitation, suitable warp and weft yarns used in the fabric of this invention are multifilament yarns formed from polyamides such as nylon 6 and nylon 6,6 as well as polyesters, and polyacrilonitrile. Nylon 6,6 may be preferred. In the preferred embodiment, the multifilament yarn used in both the warp and the fill direction will be a flat filament, high entanglement yarn using a proprietary finish oil available from E. I. DuPont in Wilmington, Del. under the trade designation K-7389. By the term &#34;flat filament&#34; is meant a nontextured yarn wherein the individual filaments have not undergone any random interlacing thereof such as through the application of an external fluid force. The total denier for the yarn used in both directions will preferably be between about 380 and about 460, more preferably between about  400 and about 440, and most preferably about 420. The total weave density achieved in both the warp and the fill directions will preferably be at least 47 threads per inch in a plain weave and more preferably between 49 and 53 threads per inch immediately after the weaving operation is complete. 
     Looking again to FIG. 3, after the woven fabric 70 is formed it is passed over and around a plurality of take-up rolls 80, 81, 82 and thereafter passed to through an accumulator 84 by conveyor rolls 85-90. Importantly, it has been found beneficial to maximize the weight 92 on the take-up compensator arm up to a level of about 80 pounds. It has also been found beneficial to the reduction of creases to apply a combination of radiant and convective heat to the fabric 70 by means of a heater 94 just prior to placing the fabric on a removal roll 96. One such heater which is believed to be particularly suitable is a 4,000 watt Radiant unit model number PO-370AX26 with a model 965 control unit available from Watlow Industries whose business address is believed to be 12001 Lackland Road, St. Louis, Mo. 63146. 
     While the fabric of the present invention may be useful for a number of applications, this fabric is believed to be particularly useful for incorporation in automobile restraint cushions or airbags. As will be appreciated by those of skill in the art, such airbags oftentimes utilize a fabric coating to control permeability. In order to apply such coatings, however, sizing compounds such as polyacrylic acid as well as yarn oils entrapped by those sizing compounds must first be removed from the fabric by scouring and drying operations. Through the use of nonsized yarn, this scouring operation can now be completely eliminated since yarn oils are no longer entrained but may now be removed in the water-jet weaving process. Accordingly, airbags incorporating such water-jet woven fabrics represent a useful advancement over the prior art. 
     FIGS. 6 and 7 are merely representative of one type of usage and design for an airbag 103 which it will be understood preferably opens in opposing relation to a vehicle occupant 105 in the event of a collision. In the embodiment illustrated, the airbag 103 is fixed at its base to an inflator 107 which in turn is linked to a collision detection sensor (not shown). When the deceleration of the vehicle exceeds a certain level, the collision detection sensor sends a signal to the inflator 107 thereby inducing the chemical reaction of a gas generating agent to inflate the airbag 103 from the stowed position of FIG. 6 to the inflated position illustrated in FIG. 7. In the illustrated embodiment the airbag 103 is stowed in a steering wheel 109 although it is to be appreciated that the airbag 103 could also be positioned in any other location opposing a vehicle occupant including a dash panel, door panel or forward seat. 
     It is to be understood that the herein disclosed fabric construction may be used in various portions of the airbag where it is desired to maintain tear resistance and to control the flow of the inflation gases which enter the airbag during collision. Thus, coated and uncoated variations of the fabric may be used either as a face fabric where it is desired to have low permeability, at the back of the bag where higher permeability may be desired or at the sides of the bag where a preselected controlled degree of permeability may be desired. Moreover, that fabric which is used may be used directly without the need for any scouring operation prior to coating or formation into the airbag. 
     In accordance with the above description, it is seen that the present invention provides a fabric and airbag formed therefrom wherein the fabric is woven on a water-jet weaving machine at weave densities which have previously been achievable only on rapier weaving machines. A process and apparatus for weaving the fabric are also provided. While specific embodiments of the invention have been illustrated and described, it is to be understood that the invention is not limited thereto, since modifications may be made and other embodiments of the principles of this invention will occur to those skilled in the art to which this invention pertains. Therefore, it is intended by the appended claims to cover any modifications and other embodiments as incorporate the features of this invention within the true spirit and scope of such claims.