Tethers with tearseams for air bag cushion

Abstract: A guide device (10) for directing the deployment of an automotive air bag cushion (12) toward the torso of an occupant by means of a tether (16) which is folded and attached to itself at a number of locations by rupturable seams (34). As the air bag cushion deploys the truncated tether or tethers cause the cushion to rotate about a point where the cushion is attached to the canister (14) thereby moving the cushion in a downward direction. The cushion is thereby moved into position in front of the occupant's torso more quickly than an air bag cushion equipped with a tether with our tearseams.

Description: This invention relates generally to inflatable type modular occupant restraint systems for passenger vehicles or, as it is more commonly known, an air bag restraint system. Such a system may be installed in an automobile or other vehicle, at least in part on the steering wheel for the protection of the driver and also in the dashboard or passenger side instrument panel for passenger protection in the event of a collision. More particularly, this invention relates to an improvement in a means for controlling the initial deployment of the air bag cushion. An air bag restraint system module typically includes a canister, which has an open side and encloses an inflator and at least part of an air bag, and a cover which conceals the module from view. When an air bag module is designed for the driver side of a vehicle the module is located in the steering wheel behind a cosmetic cover which is an integral part of the steering wheel design. When the air bag module is designed for the passenger side of a vehicle, the container may be located just behind the vehicle dashboard, cosmetic cover, or passenger side instrument panel (hereinafter referred to as "dashboard") and the cover may form an integral part of the vehicle dashboard. When the vehicle is involved in a collision, a crash signal initiates operation of the inflator to cause the air bag cushion to deploy. The inflator produces an inert gas (e.g., nitrogen) which is directed under pressure into the air bag cushion to force the air bag cushion out of the container and through the opening provided by rupturable tearseams in the steering wheel cover, or tearseams or a hinged cover in the dashboard, and into the passenger compartment of the vehicle. As the air bag cushion is directed into the passenger compartment, it is inflated by the continued flow of gas produced by the inflator. An untethered driver side air bag cushion deploys to fill the space between the steering wheel and the driver's head and upper torso. On the passenger side the air bag cushion is directed between the windshield and the occupant to fill the space between the windshield and the occupant's head and upper body. During the early stages of the air bag cushion's deployment, it is preferable to expand the air bag cushion between the steering wheel or dashboard of the vehicle and the occupant's torso in order that the momentum of the moving occupant can be initially absorbed from the occupant's torso. After the initial contact the air bag cushion still provides protection to the head and upper body of the occupant during a collision. Tethers have been used to guide the deployment of an air bag cushion for motor vehicle occupant protection. Air bag cushions are commercially available with tethered driver side and passenger side air bag cushions wherein the tethers are attached by fastener members to the impact absorbing part of the air bag cushion and to the air bag cushion near the gas inlet opening. During high energy collisions a tethered air bag cushion is positioned to receive the initial impact from the vehicle occupant's head and upper torso. An air bag cushion according to the preamble of claim 1 is known from US-A-5 044 663. The present invention consists in an automotive air bag cushion assembly for use in the passenger compartment of a vehicle comprising: an air bag cushion having a first portion which is disposed opposite an occupant of the vehicle, said first portion having a front surface and a back surface, a second portion attached to said first portion, which terminates in a third portion defining a gas inlet opening for said air bag cushion; and at least one tether having a first end and a second end, and a first edge and a second edge with said first end of each tether attached to the back surface of said first portion and said second end of each tether attached adjacent said third portion of said air bag cushion, wherein each of said tethers are folded upon themselves to form a first tether section and a second tether section and wherein each of said first tether sections are joined to said second tether section at least at a spaced contact point by rupturable attachment means to form a shortened tether, whereby as the air bag cushion is deployed the shortened tether is fully extended before the cushion is fully inflated and causes the cushion to pivot about said second tether end, before said attachment means is ruptured by further inflation of the cushion, allowing the tether to lengthen. The tethers of this invention are folded and attached upon themselves at one or more locations by a rupturable fastener means which will release when a sufficient amount of tension is applied to the tether. With this description of the invention, a detailed description follows with reference being made to the accompanying figures of drawing which form part of the specification, in which like parts are designated by the same reference numbers, and of which: Fig. 1 is a side plan view of a passenger side air bag cushion containing tethers with tearseams illustrating the air bag cushion in a partially deployed condition before the rupturable attachment means have released; Fig. 2 is a side plan view of the air bag cushion and tether illustrating the air bag cushion in a fully deployed condition after the rupturable attachment means of the tether have released; Fig. 3 is a top plan view of the tether of this invention illustrating the stitching arrangement for rupturable fastener means; Fig. 4 is a top plan view of an alternate tether for use with this invention illustrating the stitching arrangement for the rupturable fastener means; Fig. 5 is a top plan view of the air bag cushion illustrating one possible tether arrangement; Fig. 6a, 6b, and 6c are a sequence of side plan views of the air bag cushion illustrating the operation of the tethers of this invention during deployment of the air bag cushion; and Fig. 7 is a side plan view of a tether illustrating an alternate way of attaching the rupturable attachment means. As best seen in Fig. 1, an air bag deployment control device shown generally at 10 is provided for directing the deployment of an air bag cushion 12 from a module canister 14 toward a vehicle occupant. A tether 16 having a first end 18 attached to the back surface 20 of the air bag cushion first portion 22 , and a second end 24 attached adjacent a gas inlet opening 26 provided for receiving a gas from an inflator 28 . The tether 16 is folded upon itself to form at least a first section 30 and a second section 32 . The tether first section 30 is attached to the tether second section 32 at least at one location by rupturable fastener means 34 . Additionally, the folded tether 16 may include a tether third section 36 formed between the tether first end 18 and the first rupturable fastener means 34a , and a tether fourth section 38 between the first rupturable fastener means 34a and the tether second end 24 . Upon deployment of the air bag cushion 12 from the canister 14 the expansion of the cushion 12 is halted momentarily by the shortened tether 16 causing, it is believed, the air bag cushion to pivot around the tether first end 24 . As tension is applied to the tether 16 by the expanding cushion one of the rupturable fastener means 34 releases thereby allowing the cushion first portion 22 to proceed out of the canister 14 until the tether 16 again reaches the maximum length permitted by the rupturable fastener means 34 . The deployment process continues until all of the rupturable fastener means 34 are released thus permitting the tether 16 to extend to its full length. The canister 14 for use with the tether of this invention includes any canister known in the art for use with a passenger side air bag restraint system or air bag module known in the art for use with a driver side air bag restraint system. The tether of this invention was used with a passenger side canister 14 which includes a pair of first walls 40a and 40b (top and bottom respectively when viewed from above) and a pair of second walls 42a and 42b (left and right respectively when viewed from above) that define respectively a top opening 44 and a bottom opening 46 as shown in Fig. 1. An air bag inflator 28 is held between a diffuser 48 and a cap 50 attached to the bottom opening 46 of the canister 14 . Adjacent the inflator 28 and attached thereto is an air bag cushion 12 having a first portion 22 disposed in front of the occupant of the vehicle when the air bag cushion 12 is deployed. An air bag cushion second portion 52 is attached to the first portion 22 and terminates in a third portion 54 defining a gas inlet opening 26 for the air bag cushion. The air bag cushion first portion 22 has a front surface 56 which faces the occupant during deployment of the air bag cushion 12 and a back surface 20 which faces the interior of the air bag cushion 12 . The air bag cushion 12 used with this invention can be any air bag cushion known in the art. The tether 16 of this invention includes a first end 18 , a second end 24 , a first edge 58 , and a second edge 60 , as shown in Fig. 3. The tether 16 first end 18 is attached to the back surface 20 of the air bag cushion 12 by any suitable means such as stitching or the like. Preferably a box stitch 62 , as shown in Fig. 3, is used. The tether second end 24 is attached to the air bag cushion 12 adjacent the air bag cushion third portion 54 , preferably with a box stitch. Also, the tether second end 24 can be attached securely to the canister 14 adjacent the location where the air bag cushion third portion 54 is attached to the canister 14 . Preferably the tether second end 24 is attached to the bottom canister first wall 40b by appropriate fastening means such as rivets, bolts, or the like. The tether 16 is folded upon itself to form at least a first section 30 and a second section 32 . The first section 30 is attached to the second section 32 by rupturable fastener means 34 . The rupturable fastener means 34 of this invention is any suitable attachment means which will release when tension is applied to the tether 16 at the first end 18 and the second end 24 . The rupturable fastener means must be such that it will release without resulting in the tearing of the tether. Further, the rupturable fastener means 34 must be such that it will fail under cold operating conditions (approximately -30°C), while still being able to provide momentary resistance to applied force under hot operating conditions. The preferred rupturable fastener means for use with this invention is a rupturable stitch, preferably a lock stitch. The stitch may span the entire distance from the tether first edge 56 to the tether second edge 58 or any portion of the distance in between the first edge 56 and the second edge 58 . In place of a rupturable stitch a hook and loop type fastener such as a Velcro® fastener may be used. The rupturable fastener means 34 are placed at a number of spaced locations along the length of the tether 16 . Alternatively a rupturable stitch or a hook and loop type fastener such as a Velcro® 64 may be run the length of the tether 16 as shown is Fig. 7. The tether 16 can be made from any suitable flexible material having sufficient strength so as not to fail under the forces of the deploying air bag cushion. Material used in the manufacture of the air bag cushion can be used in the manufacture of the tether. Materials suitable for use in this invention are woven or knit fabrics made from nylon, polyester, polyamide fibers, or other suitable materials. Natural fibers or fibers subject to structural degradation by molds or bacteria should not be used. Further, materials not approved for use in automotive vehicle interiors should not be used. Thread used in the stitching of the rupturable stitch can be made from any suitable fiber made from nylon, polyester, polyamide fibers, or the like. As with the material used for manufacture of the tether, natural fibers or fibers subject to structural degradation by molds or bacteria should not be used for the rupturable fastener means. Reinforcement of the tether where the rupturable fastener means are located may be necessary to provide appropriate structural integrity to the tether material. These reinforcements can be made from any material suitable for providing structural integrity to the tether 16 . A single tether 16 or a single pair of narrow tethers 16 of the type shown in Fig. 3 can be used. Multiple pairs of tethers can be used, however, one pair of tethers is preferred. The number of tethers used is determined by the particular application. Tether panels as shown in Fig. 4 may also be used. Again, as with the narrow tethers single or multiple tether panels may be used. When two pairs of narrow tethers or tether panels are used the tethers are oriented as shown in Fig. 1 with the first set of tethers 16 and the second set of tethers 16b . Each of the tethers are folded about a fold line 66 and multiple rupturable fastener means 34 are used to attach the two sections as shown in Figs. 3 and 4. When a tether panel is used either a rupturable fastener means 34 sewn as a rupturable "V" stitch 35 or straight stitch 35a can be used. When a lock stitch is used as the rupturable fastener means 34 with a single pair of narrow tethers, it is preferable to use two rows of lock stitches for the first stitch 34a and a single row of lock stitches for subsequent rupturable stitches. The number and type of stitches actually used is determined by the particular application. To assemble an air bag cushion with the tethers of this invention the tethers can have the rupturable fastener means attached and the tether can then be installed in the air bag cushion in a manner similar to the installation of a conventional tether. Also, the tether can be installed in the air bag cushion without the rupturable fastener means and then the rupturable fastener means can be affixed to the tether. It is preferable to affix the rupturable fastener means prior to installation of the tether in the air bag cushion. The air bag cushion with the tether of this invention is then installed in a canister or attached to a module housing by means known in the art. When the tether second end is attached to the canister the tether with the rupturable fastener means is attached to the air bag cushion and the tether second end is attached to the canister and the air bag cushion is installed by means known in the art. The air bag restraint system with the tether of this invention can then be installed behind the dashboard of the passenger compartment of a vehicle or in the steering wheel of a passenger vehicle. A signal from a crash sensor (not shown) triggers the generation of gas by the inflator. The gas flows into the air bag cushion from the inflator through the air bag cushion gas inlet. The expanding air bag cushion ruptures the tearseam of the module cover or opens the hinged cover and starts to deploy into the vehicle passenger compartment. The air bag cushion deploys to the maximum amount permitted by the tether truncated due to the rupturable fastener means as shown in Fig 6a. It is believed that the truncated tether causes the air bag cushion to pivot around the tether second end 24 . As tension is applied to the tether by the deploying air bag cushion the first rupturable fastener means releases permitting the deploying air bag cushion to expand to a point shown in Fig. 6b. Again, it is believed that the truncated tether causes the air bag cushion to pivot further about the tether second end 24 . This process continues until all of the rupturable fastener means have released and the air bag cushion is fully deployed as shown in Fig. 6c. Thus, in accordance with the invention, there has been provided a means for quickly moving the air bag cushion into place between the occupant's torso and the instrument panel during deployment. There is also provided a means for deploying the air bag cushion such that the initial contact between the air bag cushion and the occupant is at the occupant's torso. There has also been provided a means for moving the air bag cushion into the proper position to better absorb the momentum of the occupant's torso. There has also been provided a means for reducing the momentum of the deploying air bag cushion. Additionally, there has been provided a means for lowering the deployment angle of the air bag cushion.

Claims: An automotive air bag cushion assembly (10) for use in the passenger compartment of a vehicle comprising: an air bag cushion (12) having a first portion (22) which is disposed opposite an occupant of the vehicle, said first portion (22) having a front surface (56) and a back surface (20), a second portion (52) attached to said first portion, which terminates in a third portion (54) defining a gas inlet opening (26) for said air bag cushion; and at least one tether (16) having a first end (18) and a second end (24), and a first edge (58) and a second edge (60), with said first end of each tether attached to the back surface (20) of said first portion (22) and said second end of each tether attached adjacent said third portion of said air bag cushion, characterized in that each of said tethers are folded upon themselves to form a first tether section (30) and a second tether section (32) and wherein each of said first tether sections are joined to said second tether section at least at a spaced contact point by rupturable attachment means (34) to form a shortened tether, whereby as the air bag cushion is deployed the shortened tether is fully extended before the cushion is fully inflated and causes the cushion to pivot about said second tether end (24), before said attachment means (34) is ruptured by further inflation of the cushion, allowing the tether to lengthen. A device according to claim 1 further comprising a vehicle air bag cushion canister (14) having an inside and an outside including a wall defining a cavity for a gas generator (28) and at least part of a folded inflatable occupant restraint cushion, said wall further defining an opening to said cavity in said canister, the gas generator being actuable to generate a gas under a pressure in said cavity, wherein said second end of said tether is attached securely to said inner wall (40b) of said vehicle air bag canister adjacent said third portion (54) of said air bag cushion. A device according to claim 1 or claim 2 wherein the material of said tether is made from woven fabric selected from nylons, polyesters, and polyamides. A device according to any preceding claim wherein said rupturable fastener means is a hook and loop type fastener. A device according to any one of claims 1 to 3 wherein said rupturable fastener means is a rupturable stitch.

Inventors: KRISKA THOMAS M, PRESCARO KAY H, WARD MICHAEL J, KRISKA, THOMAS M., PRESCARO, KAY H., WARD, MICHAEL J.
Applicants: MORTON INT INC, MORTON INTERNATIONAL, INC.
Application year: 1993
Main classification: B60R21
IPC codes: B60R21