Abstract:
The present invention relates to air bag tethers formed from multiple bias-cut tether segments. Groups of tether segments are attached to the front and rear air bag panels and are then connected to one another to form a functional tether system. This multiple-segment construction, with its bias-cut segments, decreases the amount of fabric that is used in the manufacture of the air bag and tethers, while providing sufficient elongation for the tether system to be functional.

Description:
REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation-in-part of co-pending U.S. patent application, Ser. No. 09/711,418, filed Nov. 13, 2000, titled “Multi-Segment Air Bag Tether Construction.” 
    
    
     TECHNICAL FIELD 
     This disclosure relates to multi-segment air bag tether systems and to a pattern-wise arrangement of such tether segments in relation to air bag panels on a fabric blank, thus resulting in increased fabric utilization and an overall cost savings per finished air bag. The air bag tether system as described herein is comprised of two multi-segment congruent tether groups that are joined to one another and to a respective air bag panel. The segments that comprise each tether group are cut substantially on the bias with respect to the warp or the fill of the fabric blank. This multi-segment construction decreases the amount of fabric that is used in the manufacture of the air bag and tether systems, while providing sufficient elongation for the tether system to be functional. 
     BACKGROUND 
     Because of the speed with which an air bag inflates, it is necessary for the protection of vehicle occupants to control the volume of space that the air bag occupies in the vehicle cabin. Traditionally, air bag tethers have been used to control the excursion of an air bag as it inflates. As gas is released, causing the air bag to rapidly inflate, it is necessary to keep such inflation from occurring in an uncontrolled manner. Tethers, which are sewn to the interior portions of the front and rear panels of an air bag, keep the inflating air bag from expanding so rapidly as to adversely affect the safety of the vehicle occupant, as the vehicle occupant contacts the air bag. 
     Tethers are conventionally strip-shaped pieces of fabric that are aligned in pattern-wise arrangement on a fabric blank, or that are aligned in relation to air bag panels that may be cut from the same blank. These tethers typically include a circular portion in the center area of the tether strip used for attachment of the tether strip to the air bag panel. It is understood in the industry that such tethers should have a capacity for elongation (that is, the tethers should be able to stretch to accommodate the rapid excursion of the bag). For this reason, conventional strip-shaped tethers have historically been cut on the bias with respect to the warp and fill of the fabric. However, utilizing these one-piece tethers increases the amount of fabric needed to create an appropriate number of tethers for a plurality of air bags, thus resulting in increased production costs. 
     SUMMARY 
     The present air bag tether system, with groups of tether segments attached to each bag panel, addresses the problems of fabric utilization and tether elongation. Using a multi-segment tether system in place of conventional one-piece tethers improves fabric utilization by allowing these bias-cut tether segments to be arranged around air bag panels into spaces that might otherwise be considered fabric waste. The segments that comprise the tether groups are each cut substantially on a bias with respect to the warp and fill of the fabric blank. This multi-segment approach, rather than one-piece tethers, leads to an improved fabric utilization, while providing a tether system that is capable of sustaining the forces exerted by the inflating air bag. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows a side view of an air bag comprised of a front bag panel and a rear bag panel; 
     FIG. 2 shows a cross-sectional view of the air bag of FIG. 1, revealing a tether system incorporated therein; 
     FIG. 3A shows a plan view of a tether segment of the present invention that is cut substantially on the bias with respect to the warp or fill of a fabric blank; 
     FIG. 3B shows a plan view of a circular reinforcement as may be included in the air bag tether system of the present invention; 
     FIG. 3C shows a plan view of a multi-segment tether group, as comprised of two of the tether segments of FIG.  3 A and the circular reinforcement of FIG. 3B; 
     FIG. 3D shows a plan view of a multi-segment tether group, in which two of the tether segments of FIG. 3A are attached to an air bag panel by a circular seam, but without the inclusion of the circular reinforcement of FIG. 3B; 
     FIG. 4 shows a plan view of a multi-segment tether group that is suitable for attachment to an air bag panel and that is comprised of three of the tether segments of FIG.  3 A and the circular reinforcement of FIG. 3B; 
     FIG. 5 shows a plan view of a multi-segment tether group that is suitable for attachment to an air bag panel and that is comprised of four of the tether segments of FIG.  3 A and the circular reinforcement of FIG. 3B; 
     FIG. 6A shows a plan view of an alternate pattern for the tether segment of the present invention, as would be attached to the front panel of an air bag; 
     FIG. 6B shows a plan view of an alternate pattern for the tether segment of the present invention, as would be attached to the rear panel of an air bag; 
     FIG. 6C shows a plan view of a multi-segment tether group, as comprised of two of the tether segments of FIG. 6A, as would be attached to the front panel of an air bag; 
     FIG. 6D shows a plan view of a multi-segment tether group, as comprised of two of the tether segments of FIG. 6B, as would be attached to the rear panel of an air bag; 
     FIG. 7A shows a plan view of yet another alternate pattern for a tether segment of the present invention; 
     FIG. 7B shows a plan view of a circular reinforcement as may be included with the tether segments of FIG. 7A; and 
     FIG. 7C shows a plan view of a multi-segment tether group, as comprised of two of the tether segments of FIG.  7 A and the circular reinforcement of FIG. 7B, as would be attached to an air bag panel. 
    
    
     DETAILED DESCRIPTION 
     In order to describe the invention, it is necessary that certain terms be defined. The term “substantial bias” is intended to refer to a cut made diagonally across the weave of a fabric at an angle of 25 to 65 degrees with respect to the warp and fill. The term “front” shall refer to that portion of an air bag that is nearest a vehicle occupant, while the term “rear” shall refer to those portions of an air bag that are furthest from the vehicle occupant (e.g., in the case of front-seat air bags, nearest the windshield). The term “tether segment” refers to a component of a tether system that is attached to a first air bag panel and to a tether segment that is attached to the second air bag panel (for instance, a tether segment on the front bag panel is attached to a corresponding tether segment on the rear bag panel). Each tether segment is cut on the bias with respect to the warp and fill of a textile fabric. The term “ether group” shall refer to two or more tether segments attached to an air bag panel, with or without the inclusion of a reinforcement between them. The term “tether system” shall refer to a pair of tether groups joined along their respective end portions, which in combination succeed in preventing the uncontrolled excursion of an inflating air bag from adversely affecting a vehicle occupant with whom such a bag comes into contact. 
     Turning now to the Figures, FIG. 1 shows a side view of an air bag  10 . Air bag  10  is comprised of a front bag panel  4  and a rear bag panel  6 , panels  4  and  6  being substantially circular, although other panel geometries could also be used. 
     FIG. 2 shows a cross-sectional view of air bag  10 , revealing the arrangement of a tether system therein. Tether segments  14  (shown in FIG. 3A as being cut substantially on the bias with respect to the warp or the fill of a fabric blank) are attached to front bag panel  4  and rear bag panel  6 . Tether segments  14  are shown in lapped fashion in the interior of air bag  10 . The joining of tether segments  14  is shown as being achieved by means of rectangular seam  18 , but such joining may be accomplished by any other means, such as welding, gluing, or other seaming techniques. Tether segments  14  are substantially rectangular in shape, each having one flared end which is positioned toward the center area of respective bag panels  4 ,  6 . 
     Reinforcement  12  (shown in FIG. 3B) may also be attached to front bag panel  4 , as well as rear bag panel  6 . It is common for reinforcements, having a circular or other shape, to be used in the production of air bags  10 . Reinforcements  12  may be circular in shape or may, for example, be in the shape of an n-sided polygon (where n is in the range of 4 to 12). In one embodiment, reinforcements  12  are included with tether segments  14  to form tether panel  24 . Such reinforcements  12  are particularly important in preventing tears around the mouth of air bag  10 , at the location of the inflation media. 
     Tether segment  14  is part of a multi-segment tether panel  24  that is shown in FIG.  3 C. Tether panel  24  is comprised of two tether segments  14  and at least one reinforcement  12 . Tether segments  14  and reinforcement  12  are secured to one another and to a bag panel  4  or  6  by seam  22 , as indicated by a dotted line in FIG.  3 C. It should be noted that tether segments  14  are cut substantially on the bias with respect to the warp or the fill of a fabric blank. The angle of the bias cut should be in the range of 25 to 65 degrees, and preferably an angle of about 45 degrees. 
     FIG. 3D shows a variation of tether panel  24  of FIG.  3 C. In this embodiment, reinforcement  12  is omitted. Tether segments  14  are attached to bag panel  4  or  6  by means of seam  22 . In this variation, tether segments  14  do not contact one another, but nevertheless act in cooperation with one another and bag panel  4  (not shown) to form tether group  28 . 
     Turning now to FIG. 4, a three-segment tether panel  36  is shown. Three-segment tether  36  is comprised of three tether segments  14  and reinforcement  12 . Tether segments  14  and reinforcement  12  may be secured to bag panel  4  or  6  by means of seam  22 . Three-segment tethers  36  are useful for reducing bag oscillation during deployment. 
     FIG. 5 shows a four-segment tether panel  46 . Four-segment tether panel  46  is comprised of four tether segments  14  and reinforcement  12 . Seam  22  secures tether segments  14  and reinforcement  12  to bag panel  4  or  6 . Four-segment tether panels  46  have an even greater ability to reduce oscillation during bag deployment. 
     FIG. 6A shows a variation of tether segment  14 . Front tether segment  54  has a widened end portion that eliminates the need for reinforcement  12 . An arc  53  in the central portion of the widened end provides half of what will be an opening  55  in front tether  64  (see FIG.  6 C). Opening  55  is useful for alignment of segments  54 . Seam  22  may be used to attach tether segments  54  to front bag panel  4  to create front tether panel  64 . 
     FIG. 6B shows a variation of tether segment  14 , as would be attached to rear bag panel  6 . Rear tether segment  56  has a widened end, similar to that of front tether segment  54 . Rear tether segment  56  is also cut on the bias with respect to the warp and fill of a fabric blank. Tether segment  56  has a small arc  58  in the central portion of the widened end, which provides half of what will be an opening  60  in rear tether panel  66  (see FIG.  6 D). Opening  60  is used to insert inflation media into the air bag. Tether segment  56  also has a ventilation opening  57  that is also present in rear tether panel  66 . Again, seam  22  may be used to secure tether segments  56  to rear bag panel  6 . Reinforcement  12  is not necessary, but may be used for additional support, if desired. FIG. 7A shows yet another variation of tether segment  14 . Tether segment  74  has an arced end portion and is slightly truncated in comparison to tether segment  14 . Like tether segment  14 , tether segment  74  also is cut substantially on the bias with respect to the warp and fill of a fabric blank. 
     FIG. 7B shows a reinforcement  72  as may be used with tether segment  74 . As illustrated in FIG. 7C, tether panel  84  is comprised of two tether segments  74  and reinforcement  72 . Seam  82  may be used to secure tether segments  74  and reinforcement  72  to one another and to bag panel  4  or  6 . Like reinforcement  12 , reinforcement  72  may be circular in shape or may be in the shape of an n-sided polygon (where n is in the range of 4 to 12). 
     The multi-segment tether system of the present invention includes multiple tether segments  14  (or alternately  54  or  74 ) and may or may not include reinforcements  12  (or alternately  72 ). These tether segments  14  are positioned with one end portion secured to the central area of bag panel  4  or  6  and one end portion directed toward the periphery of bag panel  4  or  6 . The tether system is formed by joining the periphery end portions of tether segments  14  that are attached to front bag panel  4  to the periphery end portions of tether segments  14  that are attached to rear bag panel  6 . Although sewing is a preferred means of attaching tether system components (e.g., seams  18 ,  22 , and  82 ), other attachment means can be employed, such as welding, gluing, and the like. 
     By incorporating these various multi-segment tether systems, the present invention represents a useful advancement over the prior art.