Passive air bag with slack creator

An apparatus for helping to protect an occupant of a vehicle includes an inflatable vehicle occupant protection device inflatable between a vehicle surface and the vehicle occupant. The protection device includes a front panel having a portion presented toward the occupant when the protection device is in an inflated condition. A vent includes at least one opening for releasing inflation fluid from the protection device and has an actuated condition and a non-actuated condition. A tether has a first end connected to the vent for actuating the vent and a second end connected to the protection device. A guide member connected to the front panel slidably receives a portion of the tether between the first and second ends. First and second portions of the guide member are releasably connected together to define a slackened portion. The first and second portions remain connected together in response to initial deployment of the protection device below a predetermined degree to prevent the tether from tensioning such that the vent is in the non-actuated condition. Further deployment of the protection device to the predetermined degree releases the connection between the first and second portions to allow the tether to tension and act on the vent to place the vent in the actuated condition based on the position of the occupant in the vehicle.

FIELD OF THE INVENTION

The present invention relates to an apparatus for helping to protect an occupant of a vehicle. More particularly, the present invention relates to an air bag inflatable between an instrument panel and a front seat occupant of a vehicle.

BACKGROUND OF THE INVENTION

It is known to provide an inflatable vehicle occupant protection device, such as an air bag, for helping to protect an occupant of a vehicle. One particular type of air bag is a frontal air bag inflatable between an occupant of a front seat of the vehicle and an instrument panel of the vehicle. Such air bags may be driver air bags or passenger air bags. When inflated, the driver and passenger air bags help protect the occupant from impacts with parts of the vehicle such as the instrument panel and/or a steering wheel of the vehicle.

Driver air bags are typically stored in a deflated condition in a housing that is mounted on the vehicle steering wheel. An air bag cover is connectable with the housing and/or steering wheel to help enclose and conceal the air bag in a stored condition. Upon deployment of the driver air bag, the air bag cover opens to permit the air bag to move to an inflated position. The air bag cover opens as a result of forces exerted on the cover by the inflating driver air bag.

Passenger air bags are typically stored in a deflated condition in a housing that is mounted to the vehicle instrument panel. An air bag door is connectable with the housing and/or instrument panel to help enclose and conceal the air bag in a stored condition. Upon deployment of the passenger air bag, the air bag door opens to permit the air bag to move to an inflated position. The air bag door opens as a result of forces exerted on the door by the inflating air bag.

SUMMARY OF THE INVENTION

The present invention includes an apparatus for helping to protect an occupant of a vehicle having an inflatable vehicle occupant protection device inflatable between a vehicle surface and the vehicle occupant. The protection device includes a front panel having a portion presented toward the occupant when the protection device is in an inflated condition. A vent includes at least one opening for releasing inflation fluid from the protection device and has an actuated condition and a non-actuated condition. A tether has a first end connected to the vent for actuating the vent and a second end connected to the protection device. A guide member connected to the front panel slidably receives a portion of the tether between the first and second ends. First and second portions of the guide member are releasably connected together to define a slackened portion. The first and second portions remain connected together in response to initial deployment of the protection device below a predetermined degree to prevent the tether from tensioning such that the vent is in the non-actuated condition. Further deployment of the protection device to the predetermined degree releases the connection between the first and second portions to allow the tether to tension and act on the vent to place the vent in the actuated condition based on the position of the occupant in the vehicle.

The present invention also relates to an apparatus for helping to protect an occupant of a vehicle. The apparatus includes an inflatable vehicle occupant protection device inflatable between a vehicle surface and the vehicle occupant. The protection device includes a front panel having a portion presented toward the occupant when the protection device is in an inflated condition. A vent includes at least one opening for releasing inflation fluid from the protection device and having an actuated condition and a non-actuated condition. A tether includes a first end connected to the vent for actuating the vent and a second end connected to the protection device. A resilient stop is provided on the first end of the tether for providing slack in the first end of the tether. A first guide member is connected to the front panel. A portion of the tether between the first and second ends extends through the first guide member. A second guide member connected to the protection device. The first end of the tether extends through the second guide member for actuating the vent. The tether is slidable relative to the second guide member. The stop is positioned between the vent and the second guide member in response to initial deployment of the protection device below a predetermined degree to prevent the tether from tensioning such that the vent is in the non-actuated condition. Further deployment of the protection device to the predetermined degree causes the stop to pass through the second guide member to allow the tether to tension and act on the vent to place the vent in the actuated condition based on the position of the occupant in the vehicle.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to an apparatus for helping to protect an occupant of a vehicle. More particularly, the present invention relates to an air bag inflatable between a steering wheel from which the air bag deploys and a front seat occupant of a vehicle. In an embodiment illustrated inFIG. 1-3, an apparatus10for helping to protect an occupant20of a vehicle includes an inflatable vehicle occupant protection device14in the form of an air bag. In one example, the air bag14is a driver frontal air bag for helping to protect an occupant20of a seat (not shown) on a driver side24of the vehicle. It will be appreciated, however, that the air bag14could likewise constitute a passenger frontal air bag for helping to protect an occupant of a seat on a passenger side of the vehicle from striking an instrument panel of the vehicle (not shown).

The air bag14, when deployed in response to an event for which occupant protection is desired, helps protect the occupant20by helping to absorb the force of impact placed on the air bag by the occupant. When the occupant20impacts the air bag14, the occupant penetrates into the air bag, which absorbs and distributes the impact forces throughout the large area and volume of the bag. By “penetrates” into the air bag14, it is meant to refer to the instance where, in the case of a frontal impact to the vehicle12, the occupant20is moved forward, as indicated by the arrow labeled42inFIGS. 1-3, into engagement with the air bag14.

The “penetration” of the occupant into the air bag14is the distance or degree to which the occupant20moves into the fully inflated depth of the air bag. The degree of air bag14penetration could be measured as the distance the penetrating occupant20moves a given point on a front panel74of the air bag14toward a steering wheel36of the vehicle12from which the air bag deploys. For example, penetration could be measured as the distance between a point on the front panel74and a fixed point on the steering wheel36or between a point on the occupant20, e.g. the occupant's chest, and a fixed point on the steering wheel.

The air bag14may be part of an air bag module30that includes an inflator32and a housing, illustrated in phantom at34inFIGS. 1 and 2. The air bag14has a stored condition, indicated by dashed lines inFIG. 1, in which the air bag is folded and placed in the housing34. The module30is mounted to the steering wheel36of the vehicle12. The housing34helps contain and support the air bag14and inflator32in the steering wheel36.

An air bag door40is releasably connected to the steering wheel36and/or the housing34. In a closed condition (not shown), the air bag door40forms a cover for the module30and helps enclose the air bag14in the stored condition in the housing34. The door40is movable to an opened condition illustrated inFIG. 1to uncover an opening in the steering wheel36through which the air bag14may be deployed from the stored condition in the housing34. The door40may be connected to the vehicle12, e.g., connected to the steering wheel36, either directly or through the housing34, by means (not shown), such as a plastic hinge portion, a strap or a tether.

The inflator32is actuatable to provide inflation fluid to an inflatable volume54of the air bag14to deploy the air bag to the inflated condition. The inflator32may be of any known type, such as stored gas, solid propellant, augmented or hybrid. The apparatus10includes a sensor, illustrated schematically at50, for sensing an event for which inflation of the air bag14is desired, such as a collision. The inflator32is operatively connected to the sensor50via lead wires52.

The air bag14can be constructed of any suitable material, such as nylon, e.g., woven nylon 6-6 yarns, and may be constructed in any suitable manner. For example, the air bag14may include one or more pieces or panels of material. If more than one piece or panel is used to construct the air bag14, the pieces or panels may be interconnected by known means, such as stitching, ultrasonic welding, heat bonding or adhesives, to form the air bag. The air bag14may be uncoated, coated with a material, such as a gas impermeable urethane or laminated with a material, such as a gas impermeable film. The air bag14thus may have a gas-tight or substantially gas-tight construction. Those skilled in the art will appreciate that alternative materials, such as polyester yarn, and alternatives coatings, such as silicone, may also be used to construct the air bag14.

The air bag14may have one or more actuatable features for helping to control or tailor inflation of the air bag in response to vehicle conditions, occupant conditions or both. These features may be actuatable actively, for example, in response to conditions determined via active sensors or passively, for example, having a configuration responsive to physical conditions at the time of inflation. For example, the air bag14includes a vent80and a tether112for selectively actuating the vent. The vent80is selectively actuatable to release inflation fluid from the inflatable volume54of the air bag14in response to tension applied to the tether112.

The tether112is a flexible, elongated member extending from a first end114to a second end116. The first end114is secured to a portion of the vent80for actuating the vent. The second end116is secured to a rear portion38of the air bag14adjacent the steering wheel36. The first and second ends114,116are secured to the respective components by known means, such as stitching or welding. The tether112is looped between its ends114,116through a tether guide member130secured to the front panel74within the inflatable volume54of the air bag14. The guide member130bifurcates the tether112into a first segment118extending between the vent80and the guide member and a second segment119extending between the rear portion38and the guide member. In one example, the first and second segments118,119of the tether112are integrally formed together.

The guide member130constitutes a strip of fabric doubled over onto itself and interconnected at spaced-apart portions by releasable tear stitching180to form a slackened portion140in the guide member130through which the tether112extends (seeFIG. 2). The slackened portion140therefore shortens the guide member130.

The guide member130is secured to the front panel74in a manner that also forms a slackened portion76in the front panel. The tear stitching180is configured to rupture and release the slackened portions76,140when forces acting on the tear stitching, such as tension on the guide member130, reach or exceed a predetermined magnitude that corresponds with a desired degree of air bag14inflation and deployment. In one example, the desired degree of air bag14inflation occurs when the air bag becomes fully pressurized, i.e., there is no slack in the air bag fabric. The guide member130therefore has a first, shortened condition (FIG. 2) prior to and during air bag14pressurization when the slackened portion140is held by the tear stitching180. The guide member130also has a second, lengthened condition (FIG. 1or3) when the tear stitching ruptures to release the slackened portion140. Once the slackened portion140is released the air bag14may close the vent80when the occupant is in a normally seated position (seeFIG. 1) or vent inflation fluid in response to the penetrating occupant20(seeFIG. 3).

In the shortened condition (FIG. 2), the guide member130prevents actuation of the vent80during pressurization of the air bag14. More specifically, the tear stitching180retains the guide member130in the shortened condition, which maintains the slackened portion76in the front panel74. Consequently, the tether112is slackened and prevented from tensioning and actuating the vent80when the guide member130is in the shortened condition.

In the lengthened condition (FIG. 1or3), the guide member130releases the slackened portion76to allow the air bag14to adapt to vehicle and/or occupant20conditions. Referring toFIG. 1, the released slackened portion76allows the air bag14to reach the fully deployed, large volume condition. More specifically, the tear stitching180ruptures to allow the guide member130and slackened portion76to lengthen, thereby allowing the air bag14to expand to the fully deployed condition. As a result, the tether112reaches a fully taught condition and actuates the vent80. Referring toFIG. 3, the released slackened portion76allows the fully pressurized air bag14to expand but the air bag does not inflate sufficient to tension the tether112and actuate the vent80due to the presence of the penetrating occupant20.

FIGS. 4A and 4Billustrate an example of the guide member130in accordance with the present invention. The guide member130has a lengthened condition (FIG. 4A) allowing the air bag14to fully deploy, thereby causing the tether112to actuate the vent80. The lengthened condition of the guide member130illustrated inFIG. 4Acorresponds with the vehicle12and/or occupant20conditions illustrated inFIG. 1. The lengthened condition of the guide member130illustrated inFIG. 4Aalso corresponds with the vehicle and/or occupant20conditions illustrated inFIG. 3. The guide member130has a shortened condition (FIG. 4B) prior to fully pressurization of the air bag14and preventing the tether112from actuating the vent80. The shortened condition illustrated inFIG. 4Bcorresponds with the vehicle12and/or occupant20conditions illustrated inFIG. 2.

Referring toFIG. 4B, the guide member130includes first and second ends132,134secured to the front panel74within the inflatable volume54. The ends132,134may be secured to the front panel74by any known means such as stitching, ultrasonic welding, heat bonding or adhesives. The portion of the guide member130between the ends132,134is not secured to the front panel74and forms the slackened portion140. A pair of openings142,144is formed in the slackened portion140of the guide member130for receiving the tether112such that the tether extends entirely through the slackened portion and is slidable relative to the slackened portion.

A pair of spaced-apart portions of material136,138of the guide member130between the ends132,134are releasably secured together in an adjoining, overlying manner by the releasable tear stitching180to form and retain the slackened portion140. One example of tear stitching180for use in the present invention is described and illustrated in U.S. Pat. No. 8,262,130, the entirety of which is incorporated herein by reference. The tear stitching180selectively releases the portions of material136,138in a passive manner to release the slackened portion140and allow the air bag14to reach the fully deployed condition such that the tether112actuates the vent80.

The vent80may have an actuated closed configuration capable of cooperating with the tether112to provide venting of the air bag14in accordance with the description set forth above. Referring toFIGS. 5A and 5B, the vent80is an actuated closed vent100that is actuatable to prevent inflation fluid from exiting the air bag14. The vent100includes one or more vent openings102formed in a side panel104of the air bag14, a vent door106secured to the side panel, and the tether112secured to the vent door for selectively actuating the vent. The vent door106is secured to the side panel104by known means (not shown), such as stitching, ultrasonic welding, heat bonding or adhesives.

The vent100has a closed condition (FIG. 5A) in which the vent door106extends over and covers the vent openings102and thereby prevents inflation fluid from passing through the vent openings. The closed condition illustrated inFIG. 5Acorresponds with the vehicle12and/or occupant20conditions illustrated inFIG. 1. The vent100has an open condition (FIG. 5B) in which the vent door106is positioned away from the vent openings102and thereby permits inflation fluid to vent, i.e., flow, through the vent openings. In the open condition, the vent door106is folded away from the vent openings102and held in place by a releasable tear stitch108. The open condition illustrated inFIG. 5Bcorresponds with the vehicle12and/or occupant20conditions illustrated inFIG. 2(during air bag14pressurization) andFIG. 3(when an out-of-position occupant20penetrates the fully pressurized air bag). The tether112is secured to the vent door106and may apply tension T1to the vent door to selectively actuate the vent100from the open condition to the closed condition.

Referring toFIGS. 1-3, the first end114of the tether112may extend through a guide member200secured to the air bag14in a known manner at a location adjacent the steering wheel36, e.g., on a rear panel38of the air bag14opposite and facing the front panel74. The guide member200has a round or ring shape and is formed of air bag14material, e.g., fabric. The guide member200is sized to allow the tether112to slide therethrough and helps to ensure that the actuation sensitivity of the vent100is maintained. In particular, the guide member200is positioned to guide the tether112in a direction extending substantially parallel to movement of the occupant20into the air bag14such that the tether tensions and slackens in a substantially 1:1 ratio with movement of the front panel74.

Referring toFIGS. 1-3, upon sensing the occurrence of an event for which inflation of the air bag14is desired, such as a vehicle collision, the sensor50provides a signal to the inflator32via the lead wires52. Upon receiving the signal from the sensor50, the inflator32is actuated and provides inflation fluid to the inflatable volume54of the air bag14in a known manner. The inflating air bag14exerts a force on the door40, which moves the door to the opened condition. The air bag14inflates from the stored condition to a deployed condition, such as the fully inflated and deployed condition illustrated inFIG. 1. The air bag14, while inflated, helps protect the vehicle occupant20from impacts with parts of the vehicle12, such as the steering wheel36.

When an event occurs in which inflation of the air bag14is desired, the vent80, tether112, and guide member130respond to vehicle conditions, occupant conditions or both to help control inflation and deployment of the air bag. For example, the vent80may adapt based on the position of the occupant20upon the occurrence of the event for which inflation of the air bag14is desired. Prior to such an event, the vent80is in the open, non-actuated condition while stored in the air bag module30. If, upon the occurrence of an event for which inflation of the air bag14is desired, the occupant20is in the normally seated position ofFIG. 1, the vent80is actuated to the closed condition and the air bag14inflates to the normally deployed condition due to the cooperation of the tether112and vent.

In the normally seated condition, the occupant20is spaced from the air bag14and must move forward in order to engage and penetrate the air bag. This distance can be measured in terms of occupant chest to steering wheel36distance, which is indicated at D1inFIG. 1. The distance that the occupant20must travel before this engagement takes place can vary depending on the occupant/seat position prior to air bag deployment. In this configuration, the air bag14may also be constructed such that the tether112does not actuate the vent80in response to the obstructed deployment of the air bag14when, for example, the occupant20is away from the normally seated position and penetrates the air bag. The degree of penetration inFIG. 3can be calculated as the difference between the inflated depth D1inFIG. 1and the penetrated depth, labeled D2inFIG. 3.

As the air bag14inflates and pressurizes (seeFIG. 2) the front panel74moves away from the steering wheel36, thereby moving the guide member130secured to the front panel away from the steering wheel and lengthening the tether112. Consequently, the guide member130becomes taught and tension is applied to the tear stitching180securing the slackened portion140prior to the tether112becoming taught. Since the first end114of the tether112is not tensioned the vent80remains in the non-actuated condition at this stage of deployment. When the air bag14reaches a threshold or predetermined pressure, e.g., a fully pressurized condition, tension on the guide member130is sufficient to rupture the tear stitching180, thereby releasing the slackened portion140and allowing the front panel74to move further outward with the expanding air bag14toward the fully inflated and deployed condition ofFIG. 1.

Referring toFIG. 4A, once the slackened portion140(shown inFIG. 4B) is released, the portions of material136,138move away from one another as the ends132,134of the guide member130move outward in the direction indicated by the arrows A with the expanding air bag14, i.e., the guide member straightens and lengthens along the contour of the front panel74. The lengthening of the guide member130is possible due to the lengthening of the slackened portion76in the front panel74, which is free to straighten and lengthen in the direction A under the inflation fluid pressure once the tear stitching180ruptures. When both slackened portions76,140lengthen the entire guide member130moves outwardly with the expanding air bag14, which tensions both segments118,119of the tether112.

Tensioning of the tether112occurs until the front panel74reaches a predetermined distance away from the steering wheel36, at which point the entire tether becomes tensioned. Referring toFIG. 5A, further inflation of the air bag14thereafter causes the tether112to pull on the vent door106and ultimately actuate the vent80. More specifically, the tensioning force T1applied to the vent door106by the now taught first segment118breaks or otherwise ruptures the tear stitching108and moves the door portion to the closed condition ofFIG. 5A. The vent door106blocks inflation fluid flow through the vent openings102, allowing the air bag14to inflate to the normally deployed and pressurized condition ofFIG. 1.

Referring toFIG. 3, if, upon the occurrence of the event, the occupant20is positioned away from the normally seated position, the occupant may impede or restrict the air bag14from reaching the fully inflated position. This may occur when the occupant20is leaned forward and/or unbuckled so as to impede inflation of the air bag14. In this case, the air bag14is pressurized sufficient to rupture the tear stitching180, but the first segment118of the tether112is not sufficiently tensioned and, thus, the vent80remains in the open, non-actuated condition (seeFIG. 5B). As a result, pressurization of the air bag14through the open vent80is limited and, thus, the air bag inflates and deploys to the small volume condition ofFIG. 3.

More specifically, when the occupant20is positioned away from the normally seated position the front panel74is only capable of moving the distance D2away from the steering wheel36. The distance D2corresponds with an air bag14that is fully pressurized but the inflation depth or pressure is below the predetermined amount necessary to adequately tension the first segment118of the tether112. Consequently, the tether112applies no tension to the vent80and, thus, the vent remains non-actuated when the occupant20is positioned away from the normally seated position.

One having ordinary skill in the art will readily understand that the tether112and tear stitching180of the present invention help ensure that the vent80is reliably actuated when the occupant20is in the normally seated position. Likewise, the tether112and tear stitching180help ensure the vent80reliably remains non-actuated during pressurization of the air bag14and when the occupant20is positioned away from the normally seated position. More specifically, the first segment118of the tether112does not and cannot fully tension unless the tear stitching180ruptures to release the slackened portion140and allow the slackened portion76of the front panel74to lengthen. The first segment118therefore cannot actuate the vent80unless the tear stitching180on the guide member130ruptures and the front panel74moves a distance away from the steering wheel36sufficient to fully tension the tether112. Since the tear stitching180only ruptures when the air bag14inflates over a predetermined amount it is clear that the vent80does not actuate until the air bag14is sufficiently inflated. Consequently, venting of the air bag14is reliably controlled by the tether112, guide member140, and tear stitching180of the present invention.

Referring toFIG. 1, in a typical air bag construction the vent (shown in phantom at80′) is actuated by a single segment tether (shown in phantom at112′) secured to and between the vent80′ and the air bag14. During inflation and deployment, the initial slack in the single segment tether112′ allows the vent80′ to move or shift positions about the air bag14. Due to this movement, the vent80′ may move to an undesirable position on the air bag14during deployment that prematurely tensions the tether112′. Consequently, the typical tether112′ may apply tension to the vent80′ prior to the air bag14becoming pressurized to the degree to which actuation of the vent is desired.

The slackened portion140and tear stitching180of the present invention help ensure the vent80reaches its desired position on the air bag14during deployment prior to being actuated. The first end114of the tether112does not and cannot apply tension to the vent door106sufficient to actuate the vent80until or unless the front panel74reaches the predetermined distance from the steering wheel36. As noted, however, the front panel74may only reach the predetermined distance from the steering wheel36if the tear stitching180ruptures to release the slackened portion140. Consequently, the vent80of the present invention cannot be actuated until or unless the tear stitching180releases the slackened portion140, thereby allowing the vent to reach the desired position on the air bag14before being actuated.

The air bag14is configured such that the time difference between the onset of air bag inflation and the release of the slackened portion140is sufficient to allow the vent80to reach its proper, predetermined position on the air bag. Subsequent actuation of the vent80will therefore occur only while the vent is properly oriented in the air bag14, thereby ensuring the vent not only actuates at the proper time but also while in the proper position.

According to the present invention, a rupturable tear stitch configuration that promotes predictability, repeatability, and reliability in releasing interconnected fabrics is used to form the tear stitchings108and180. The tear stitchings108and180illustrated inFIGS. 4A-4BandFIGS. 5A-5Bare two examples of potential implementations of the tear stitch configuration of the present invention. Those skilled in the art will appreciate that the tear stitch configuration of the present invention may be implemented to provide a releasable connection between any desired fabric components of a vehicle occupant protection device.

FIGS. 6A and 6Billustrate an example tear stitching201in accordance with the present invention. The tear stitching201may constitute the tearing stitching180and/or the tear stitching108ofFIGS. 1-5B. InFIGS. 6A and 6B, the tear stitching201constitutes the tear stitching180for selectively releasing the slackened portion140of the tether112. The tear stitching201interconnects first and second portions of material220and230positioned in an adjacent and overlying manner.

As representative of the tear stitching180inFIGS. 1-5B, the first and second portions of material220and230may correspond to the overlying portions136,138of the guide member130forming the slackened portion140. In this instance, the first and second portions of material220,230constitute any spaced-apart portions of the guide member130between the ends132,134and may be overlayed with one another in any manner any number of times. As another example, representative of the tear stitching108inFIGS. 5A and 5B, the first portion of material220may correspond to the vent door106and the second portion of material230may correspond to the side panel104of the air bag14(not shown).

The tear stitching201may be constructed using conventional sewing techniques and equipment. The tear stitching201includes a bobbin thread203and a stitch thread205. The stitch thread205extends through the first and second portions220and230and loops around the bobbin thread. As best shown inFIG. 6A, the tear stitching201is a line of stitching having a start point206and an end point208. A break point211is located between, e.g., at the midpoint between, the start point206and the end point208. The break point211is the point along the tear stitching201where it is intended that the tear stitching rupture under tension.

The tear stitching201has an inverted, generally curved V-shaped configuration with outwardly diverging curved segments or legs212that meet at the break point211. The tear stitching201is arranged such that an axis of symmetry214of the tear stitching extends generally perpendicular to the two opposed directions in which tension, indicated generally by the arrows labeled T2inFIGS. 6A and 6B, is applied to the first and second portions220and230. The axis of symmetry214bisects the V-shaped configuration of the tear stitching201.

The tear stitching201is configured to rupture in response to the tension T2applied to the first and second portions of material220and230. This tension T2may correspond, for example, to the tension applied to the overlying portions of the guide member130or to the tension applied to the vent door106and side panel104during deployment of the air bag14. The first and second portions of material220and230are arranged such that the tension T2applied to the portions results in a peeling action or motion between the portions, which acts on the tear stitching201. In the embodiment illustrated inFIGS. 6A and 6B, this peeling action is produced by positioning the break point211closest to the front panel74. When the tension T2is applied to the first and second portions of material220,230as the ends132,134of the guide member140move away from one another relative to the tear stitching201, the resulting peeling action helps focus the tension on the break point211of the tear stitching.

According to the present invention, the predictability, reliability, and repeatability with which the tear stitching201ruptures in response to the tension T2is tailored through the selection of materials and configuration of the tear stitching. The generally inverted V-shaped configuration of the tear stitching201illustrated inFIGS. 6A and 6B, which is oriented generally parallel to the tension T2, focuses the tension T2on the break point211. Thus, it will be appreciated that the tension T2is focused primarily on the few, e.g., 1 or 2, stitches that make up the break point211of the tear stitching201.

Since the tension T2is focused on the break point211, the tear stitching201begins to rupture when the stitch thread205at the break point ruptures and begins to unravel from the material220and230. The stitch thread205, having a known tensile strength, will rupture when the tension T2reaches a known value. Since the break point211comprises only a few stitches of the stitch thread205, the number of variables that could affect the tension T2at which the tear stitching begins to rupture is reduced as opposed to, for example, tear stitching in which the tension is spread over a large number of stitches. Therefore, predictable, reliable, and repeatable rupturing of the tear stitching201can be achieved by selecting a stitch thread205with an appropriate tensile strength based on known vehicle conditions and/or occupant conditions.

To help ensure the tear stitching201ruptures when tension T2reaches a predetermined threshold level, the bobbin thread203may be selected to have a tensile strength greater than the stitch thread205. This will help ensure that the stitch thread205ruptures first under the tension T2and thus helps improve the predictability, reliability, and repeatability with which the entire tear stitching201ruptures. Consequently, the tear stitching201of the present invention helps to increase the reliability of the vent80actuating only when the first segment118of the tether112is fully tensioned upon rupture of the tear stitching201and release of the slackened portion140.

Also, according to the present invention, the leg portions212of the tear stitching201may be designed to be just sufficient to maintain a predetermined strength for the connection between the overlying portions of material220and230. By so designing the leg portions212, the amount of tear stitching201that needs to unravel in order to release the portions220and230is minimized. This helps increase the speed at which the tear stitching201ruptures when the tension T2reaches the desired magnitude, which can further promote the predictability, reliability, and repeatability with which the tear stitching201ruptures. Through testing and evaluation, it was determined that the performance of the tear stitching201can be affected through the stitch configuration, e.g., the shape of the tear stitching. To make this determination, various stitch configurations and thread types were tested to determine the load at which the tear stitching ruptured. The results of these tests are illustrated in the chart ofFIG. 7.

Referring toFIG. 7, various stitch shapes were tested to determine the load at which the tear stitching ruptured. In all of the tests, the tear stitching interconnected overlying portions of material in the same manner as that illustrated inFIGS. 6A and 6B. In each test, the tear stitching was oriented in a manner similar or identical to that shown inFIGS. 6A and 6B. In particular, the tear stitching was oriented such that the axis of symmetry of the tear stitching extended generally perpendicular to the opposite directions in which the tension is applied to the first and second portions of material, thus focusing the tension primarily on the break point for that particular stitch configuration.

As shown inFIG. 7, the generally curved V-shaped configuration shown and described inFIGS. 6A and 6Band along with seven other stitch configurations were tested. In each stitch configuration, the stitch thread was Tex-30 Nylon thread and the bobbin thread was Tex-138 Nylon with a stitch size of about 3 millimeters and a thread tension of about 120 cN (1.2 Newtons). The overlying portions of material were constructed of 700 dtex woven Nylon coated with silicone on one side.

The tests were conducted on eight different tear stitching configurations: square U-shaped tear stitching300, semi-circular tear stitching302, curved U-shaped tear stitching304, O-shaped tear stitching306, skinny square U-shaped tear stitching310, oval-shaped tear stitching312, straight V-shaped tear stitching314, and curved V-shaped tear stitching316. The curved V-shaped tear stitching316was identical to that illustrated inFIGS. 6A and 6B. Each of these tear stitching configurations incorporated ten stitches, except the skinny square U-shaped tear stitching310, which incorporated11stitches. For each stitch configuration, the overlying portions of material were arranged as shown inFIGS. 6A and 6Band interconnected via the tear stitching. For the circular tear stitching306and the oval shaped tear stitching312, the start and end points were located opposite the break point. Tension was applied as shown inFIGS. 6A and 6Buntil the tear stitching ruptured, at which point the magnitude of the tension was recorded.

The testing was performed five to six times per stitch configuration. Based on the results of the tests, known statistical methods were employed to determine the expected performance for each stitch configuration with confidence intervals of 95%. The confidence levels for each stitch configuration are illustrated in the shaded areas associated with each stitch configuration inFIG. 7. By “95% confidence intervals,” it is meant that, for each stitch configuration, the average rupture tension will fall within the range defined by the shaded areas 95% of the time. Thus, for example, for the curved V-shaped stitch configuration316, the average rupture load will fall within the range of about 55-79 Newtons 95% of the time.

From the above, those skilled in the art will appreciate that, according to the present invention, the strength of the rupturable tear stitching201can be tailored through the configuration or shape of the tear stitching itself without altering the thread type and while maintaining a consistent, e.g., minimal, number of stitches. This allows the rupture strength of the tear stitching201to be tailored to performance criteria that may be application specific, even within the same overall application.

For example, referring toFIGS. 1-5B, it may be desirable that the rupture strength of the tear stitching108used to secure the vent door106be less than the rupture strength of the tear stitching180used to secure the slackened portion140of the guide member130. In this instance, the desired performance can be achieved, for example, by using the square U-shaped stitch configuration300(seeFIG. 7) or semi-circular stitch configuration302for the tear stitching180so that the slackened portion140remains secured and the first segment118slackened due to relatively strong tear stitching. In a similar manner, straight V-shaped stitch configuration314or curved V-shaped stitch configuration316can be used for the tear stitching108so that the vent door106is maintained in the open condition by comparatively weaker tear stitching.

Through testing and evaluation, it was determined that the performance of the tear stitching201can also be affected by the type of thread used to construct the tear stitching. To make this determination, threads of various types were used to form three of the stitch configurations described above. These stitch configurations with the various threads were tested to determine the load at which the tear stitching ruptured. The results of these tests are illustrated in the chart ofFIG. 8.

Referring toFIG. 8, the stitch configurations used to perform the tests were the semi-circular tear stitching302, the circular tear stitching306, and the oval-shaped tear stitching312. In all of the tests, the tear stitching interconnected overlying portions of material in the same manner as that illustrated inFIGS. 6A and 6B. In each test, the tear stitching was oriented in a similar or identical manner as that shown inFIGS. 6A and 6B. For the circular tear stitching306and the oval shaped tear stitching312, the start and end points were located opposite the break point. In particular, the tear stitching was oriented such that the axis of symmetry of the tear stitching extended generally perpendicular to the opposite directions in which the tension T2was applied to the first and second portions of material, thus focusing the tension primarily on the break point. Each stitch configuration included ten stitches, the stitch size was about 3 millimeters, and the thread tension was about 120 cN (1.2 Newtons). The overlying portions of material were constructed of 700 dtex woven Nylon with a silicone coating applied on one side.

The tests were conducted on six different thread types for each stitch configuration: Tex-16 polyester thread, Tex-27 Nylon, Tex-30 Nylon, Tex-45 Nylon, Tex-70 Nylon, and Tex-90 Nylon. For each stitch configuration, the overlying portions of material were arranged as shown inFIGS. 6A and 6Band interconnected via the tear stitching. Tension T2was applied, as shown inFIGS. 6A and 6Buntil the tear stitching ruptured, at which point the magnitude of the tension was recorded. For each of the six thread types, the test was repeated 5-6 times on each of the three stitch configurations.

The chart ofFIG. 8illustrates the results of the tests. InFIG. 8, the horizontal axis represents the tensile strength of the six different threads used in the tests. As illustrated inFIG. 8, the Tex-16 polyester thread has a tensile strength of about 1.8 Newtons, the Tex-27 nylon thread has a tensile strength of about 3.4 Newtons, the Tex-30 nylon thread has a tensile strength of about 4.7 Newtons, the Tex-45 nylon thread has a tensile strength of about 7.5 Newtons, the Tex-70 nylon thread has a tensile strength of about 11 Newtons, and the Tex-90 nylon thread has a tensile strength of about 14 Newtons. The vertical axis represents the stitch strength of the three stitch configurations using the different thread types.

InFIG. 8, the dots plotted on the chart represent average rupture strengths of the three stitch configurations using the different threads. For example, for the semi-circular stitch configuration302using the Tex-45 nylon thread, the average rupture strength was about 190 Newtons. As another example, for the circular stitch configuration306using the Tex-45 nylon thread, the average rupture strength was about 135 Newtons. As a further example, for the elliptical stitch configuration312using the Tex-45 nylon thread, the average rupture strength was about 125 Newtons. At this point, it should be noted that average stitch strengths for the semi-circular tear stitch configuration302using the Tex-70 and Tex-90 nylon threads were not recorded because the strength of the tear stitching exceeded 250 Newtons, which was the maximum tension that the device used to measure the tension was capable of measuring.

Based on the results presented inFIG. 8, it will be appreciated that as the thread strength increases, the strength of the tear stitching also increases. The lines plotted on the chart and associated with the stitch configurations approximate the relationship between thread strength and the strength of the tear stitching using a best-fit algorithm. These plotted lines illustrate that this relationship is approximately linear.

From the above, those skilled in the art will appreciate that, according to the present invention, the strength of the rupturable tear stitching201can be tailored through the selection of the thread used to construct the tear stitching without altering the configuration or shape of the tear stitching itself and while maintaining a consistent, e.g., small, number of stitches. This also allows the rupture strength to be tailored to performance criteria that may be application specific, even within the same overall application.

Combining the relationships illustrated inFIGS. 7 and 7, those skilled in the art will further appreciate that, according to the present invention, the strength of the rupturable tear stitching201can be tailored through a combination of selecting the type of thread used to construct the tear stitching and the configuration or shape of the tear stitching while maintaining a consistent, e.g., small, number of stitches.

This also allows the rupture strength to be tailored to performance criteria that may be application specific, even within the same overall application.

For example, referring toFIGS. 1-5B, it may be desirable that the rupture strength of the tear stitching108used to secure the vent door106be less than the rupture strength of the tear stitching180used to secure the guide member130. In this instance, the desired performance can be achieved, for example, by using the Tex-70 or Tex-90 nylon thread with a square U-shaped stitch configuration300or semi-circular stitch configuration302to construct the tear stitching180, and by using Tex-16 polyester or Tex-27 nylon thread with a V-shaped stitch configuration314or curved V-shaped stitch configuration316to construct the tear stitching108.

FIG. 9illustrates by way of example tear stitching201ain accordance with another aspect of the present invention. Similar to the tear stitching201ofFIGS. 6A and 6B, the tear stitching201amay represent the tear stitching108and/or the tear stitching180ofFIGS. 1-5B. As shown inFIG. 9, the tear stitching201aincludes two rupturable stitch lines: a first stitch line400and a second stitch line420. The first and second stitch lines400and420may be constructed using conventional sewing techniques and equipment and include a bobbin thread and a stitch thread (not shown) as described above in regard to the embodiment ofFIGS. 6A and 6B.

The first stitch line400has a start point402, an end point404, and a break point406located between, e.g., at the midpoint between, the start and end points. The break point406is the point along the first stitch line400where it is intended that the stitching begins to rupture under tension. Similarly, the second stitch line420has a start point422, an end point424, and a break point426located between, e.g., at the midpoint between, the start and end points. The break point426is the point along the second stitch line420where it is intended that the stitching begins to rupture under tension.

The first and second stitch lines400and420may have any of the shapes or configurations described above and illustrated inFIG. 7. The first and second stitch lines400and402may also have any of the material constructions described above and illustrated inFIG. 8. According to the present invention, the shape, configuration, and material construction of the first and second stitch lines400and420may be selected to tailor the stitching201ato perform desired functions and to exhibit desired performance characteristics.

The first stitch line400has the inverted, generally curved V-shaped configuration described above and the second stitch line420has the semi-circular configuration described above. The tear stitching201ais arranged such that an axis of symmetry214aof the tear stitching extends generally perpendicular to the opposite directions in which tension (not shown but in the same directions as the tension T2inFIGS. 6A and 6B), is applied to the first and second portions220and230. These configurations, along with their material constructions, are selected to tailor the tear stitching201ato perform desired functions and to exhibit desired performance characteristics.

The tear stitching201ais configured to rupture in response to the tension applied to the first and second portions of material220and230. This tension may correspond, for example, to the tension applied to the vent door106and side panel104during deployment of the air bag14. This tension may also correspond, for example, to the tension applied to the overlying portions136,138of the guide member130.

As shown inFIG. 9, the first and second portions of material220and230are arranged such that the tension applied to the portions results in a peeling action of motion between the portions, which acts on the tear stitching201a. In this embodiment, this peeling action is produced by positioning the break point406closest to the front panel74. When the tension is applied to the first and second portions of material220,230as the ends132,134of the guide member140move away from one another relative to the tear stitching201a, the resulting peeling action helps focus the tension on the break point406of the tear stitching.

Since the tension is focused initially on the break point406, the first stitch line400begins to rupture when the stitch thread at the break point ruptures and begins to unravel from the material220and230. The stitch thread, having a known tensile strength, will rupture when the tension reaches a known value. Since the break point406comprises only a few stitches of the stitch thread, the number of variables that could affect the tension at which the first stitch line400begins to rupture is reduced as opposed to, for example, tear stitching in which the tension is spread over a large number of stitches.

The function of the first stitch line400may, for example, be to help absorb or dampen the forces exerted on the tear stitching201aduring initial deployment of the air bag14. The first stitch line400may thus be configured to rupture in response to tension forces less than those in response to which the second stitch line420is configured to rupture. The first stitch line400may rupture, either partially or completely, under forces exerted on the tear stitching201aduring initial deployment of the air bag14, leaving the second stitch line420intact so that it can respond in the desired manner to the aforementioned vehicle12and occupant20conditions in the vehicle. For example, the second stitch line420can remain intact during initial deployment only to subsequently rupture to release the slackened portion140and allow the first segment118to fully tension and actuate the vent80. Alternatively, the second stitch line420can remain intact throughout inflation of the air bag14such that the vent80is non-actuated.

From the above, those skilled in the art will appreciate that a predictable, reliable, and repeatable rupture of the first and second stitch lines400and420can be achieved by selecting a stitch thread with an appropriate tensile strength and using it in an appropriate configuration. For example, through testing, the magnitude of the tension exerted on the portions of material220and230due to deployment of the air bag14and the tension exerted due to fully inflated conditions can be determined. The shape/configuration and material construction of the first stitch line400could be selected so that its rupture strength is at or about the magnitude of the measured deployment tensions. The shape/configuration and material construction of the second stitch line420could be selected so that its rupture strength is at or about the magnitude of the tensions measured during the fully inflated conditions.

FIG. 10is a chart that illustrates the function of the tear stitching201aof the embodiment ofFIG. 9. As shown inFIG. 10, as the air bag14deploys, the tension applied to the first and second portions of material220and230begins to increase. At time t1, initial air bag14deployment increases the tension on the portions of material220,230to a magnitude at which the first stitch line400ruptures. This causes a brief decrease in the tension due to the force absorbing/damping provided by the first stitch line400. As the event prompting deployment of the air bag14continues, vehicle12and occupant20conditions, such as a normally seated and unbelted occupant, allow continued air bag deployment, which increases the tension on the portions of material220,230to the point at which the second stitch line420ruptures at time t2. This completes rupture of the tear stitching201aand releases the interconnection between the portions of material220and230.

Those skilled in the art will appreciate that the embodiment of the invention illustrated inFIGS. 9 and 10allows for a wide variety of configurations of the tear stitching201a. For example, more than two stitch lines could be used to tailor further the performance characteristics of the tear stitching201a. As another example, the first and second stitch lines400and420may constitute portions of a single stitch line instead of separate stitch lines.

FIGS. 11-13Billustrate an air bag14in accordance with another aspect of the present invention. In this embodiment, the guide member130is omitted and the tether112includes additional structure that cooperates with the guide member200for helping to ensure the vent80does not prematurely actuate during initial inflation of the air bag14. It will be appreciated that the guide member200may be used in combination with the first guide member130ofFIGS. 1-5B(not shown).

Referring toFIGS. 11 and 12, the tether112extends through a guide member500secured to the front panel74of the air bag14in a known manner. The guide member500has a round or ring shape and is formed of air bag14material, e.g., fabric. The guide member500is sized to allow the tether112to slide therethrough. The guide member500replaces the tear stitched guide member130ofFIGS. 1-5B.

FIGS. 13A and 13Billustrate the guide member200in more detail. In particular, the guide member200constitutes a body502secured to the air bag14(not shown) in a known manner at a location adjacent the steering wheel36. The body502has a round or ring shape and is formed of air bag14material, e.g., fabric. An aperture504extends through the body502and is sized and shaped to allow the tether112to slide through the aperture. The aperture504may therefore have a circular or polygonal shape.

A stop510secured to or formed integrally with the first end114of the tether112cooperates with the guide member200for controlling the degree of tension on the tether between the body502and the vent80. The stop510extends radially outward from the tether112and is formed of a resilient material that elastically deforms under compression. The stop510is sized to be larger in cross-section than the aperture504but is deformable under compression to pass through the aperture when a predetermined amount of tension is applied to the first end114of the tether112.

Referring toFIGS. 12 and 13B, the stop510is positioned near or on the first end114of the tether112initially between the body502and the vent80such that the tether is slackened between the body and the vent prior to air bag14deployment. During initial air bag14deployment the first end114of the tether112remains slackened and, thus, the stop510remains between the body502and the vent80. Due to friction between the tether112and the guide member500on the front panel74during initial air bag14deployment, the stop510may move with the tether away from the vent80and into engagement with the body502. The stop510, however, is larger than the aperture504and therefore is initially prevented from passing through the aperture. More specifically, the stop510is configured such that it will not sufficiently deform to pass through the aperture504unless tension T1on the tether112reaches a predetermined level that corresponds with a predetermined degree of air bag14deployment. Due to this configuration, the first end114of the tether112does not and cannot tension when the stop510is located between the body502and the vent80. Consequently, the first end114of the tether112does not and cannot actuate the vent until the air bag14sufficiently deploys.

Referring toFIGS. 11 and 13A, the expanding air bag continues to increase the tension T1on the tether112until the tension reaches the predetermined level necessary to pull the stop510though the aperture504. In particular, when the tension T1reaches this predetermined level the stop510is compressed against the body502sufficient to pass through the aperture504. Once this occurs, the first segment118is free to tension with the expanding air bag14until the first end114of the tether112actuates the vent80.

The guide member200of the present invention helps ensure the vent80reaches its desired position on the air bag14during deployment prior to being actuated. As noted, the first end114of the tether112must be tensioned to actuate the vent80. The stop510of the guide member200, however, does not pass through the aperture504to allow the first end114of the tether112to tension until or unless the front panel74reaches the predetermined distance from the steering wheel36and, thus, the tether remains slackened between the vent80and the guide member200. Consequently, the vent80of the present invention cannot be actuated until or unless the stop510passes through the aperture504, thereby giving the vent sufficient time to reach the desired position on the air bag14.

From the above description of the invention, those skilled in the art will perceive improvements, changes and modifications. Such improvements, changes and modifications within the skill of the art are intended to be covered by the appended claims. For example, it will be appreciated that one or more of the components of each embodiment may be readily incorporated into each of the other embodiments within the spirit of the invention.