Field of the Invention

The present invention relates generally to the formation of fabric confinements and more particularly to the formation of a seamless stretchable fabric air restraint bag.

Background of the Invention

Much attention has recently been directed to the formation of fabric confinements requiring special characteristics. For example, the automobile industry has become increasingly concerned with safety of automobile occupants during a crash. It is known to construct a confinement, referred to as an "air bag" in an automobile which is inflated upon detection of a crash. Today, many automobile manufacturers have met consumer concern for safety through the inclusion of air bags in motor vehicles not only as optional equipment but also as standard equipment.

However, manufacturers have encountered difficulty and expense in the formation and production of air bags of specified shapes and dimensions.

A typical air restraint system presently utilized in passenger motor vehicles includes an inflatable confinement, or air bag, an impact detector and an inflating means. Upon detection of an impact greater in magnitude than a threshold impact, the impact detector provides a signal to the inflating means which causes the inflating means to inflate the confinement. The inflating means illustratively comprises pyrotechnic or gas producing means. Thus, the inflated confinement serves to protect the passenger and/or driver from what is often considered

the most serious effect of an automobile collision: a secondary collision, i.e., the collision between an occupant and the interior of the motor vehicle.

Unfortunately, any such air restraint system is effective in preventing personal injury only to the extent that the occupant properly contacts the inflated bag. Thus, the dimensions and shape of an inflated air bag are critical and are often dictated by an exacting specification.

The specific shape and dimensions of any particular air bag are affected by the position in which it is placed in a motor vehicle. Consideration must be given to not only the position of the protected occupant(s) but also to the portion of the vehicle's interior in close proximity to the air bag and against which the air bag will be forced in a collision. Such design considerations, among others, have led to uniquely shaped air bags. For example, U.S. Patent No. 4,262,931 to Strasser et al. discloses an air bag having a plurality of compartments for knee, torso and head restraint, some of which deploy towards one of the passenger seating positions and some of which expand laterally across the vehicle interior in front of the adjacent passenger position. This particular device also utilizes a pressure regulating valve flap between compartments. U.S. Patent No. 3,937,488 to Wilson et al. depicts an elongated air bag of approximately rectangular cross-section and planar end' sections. This particular device utilizes two different materials of different air permeability to form the air bag.

Some known devices have attempted to solve problems associated with providing air bags of precise shapes and dimensions through stitching together separate sheets of fabric so as to form a desired shape. Unfortunately, stitched seams in known air bags have encountered difficulty in maintaining the pressure within

the bag during inflation. Air bags, in order to be effective, must inflate within a fraction of a second. Such a rapid rate of inflation and ultimate pressure leads to the exertion of a tremendous tensile load on the stitching. Such stitching decreases the overall strength of the fabric at the seam due to the perforations in the fabric inherent from the stitching process. Additionally, the strength of the stitching thread must be considered, as well as the additional cost of stitching.

Furthermore, stitching of separate sheets of fabric, whether they are identical or of different air permeability, increases the bulk of the air bag, as the seam will have a thickness which is at very least the sum of the thickness of both separate sheets of fabric. With the current practice of downsizing vehicles, any unnecessary bulk is most undesirable. Excess bulk leads to unwanted excess weight which is undesirable in efforts to reduce weight and which in turn makes rapid deployment more difficult. Stitching is also undesirable since it produces a protrusive stitched surface which may harm an occupant whom it contacts. Illustrative of air bags constructed from stitched together layers of fabrics is that disclosed in U.S. Patent No. 3,892,425 to Sakairi et al.

For the sake of completeness, it has been recognized that air restraint bags which at least partially deflate soon after, or even during, inflation advantageously provide a means to counteract the dangerous effect known as rebound. Such controlled deflation permits the air bag to absorb more energy from the occupant.

Various methods have been proposed for the controlled deflation of air bags. Illustrative of such methods are those disclosed in U.S. Patent Nos. 3,937,488 to Wilson (air bag constructed from at least two materials having different air permeability values) and 3,892,425 to Sakairi et al. (air bag constructed from coated material

wherein expansion of the air bag stretches the stitches of the fabric, creating new openings through the coating in addition to microporous openings) .

Additionally, the exacting specifications to which an air bag manufacturer must adhere include requirements relating to shape, dimension, energy absorption, inflation and deflation time periods, toxicity, flammability, tensile and tear strength, flexibility from -30°C to 90°C, temperature and accelerated aging resistance. Unfortunately, the use of fabrics can present difficulty in meeting such requirements.

Summary of the Invention

The present invention relates to an air bag restraint system for protecting an occupant of a vehicle during a collision comprising an inflatable confinement adapted for attachment to the vehicle and inflatable upon collision of the vehicle. The confinement is constructed from a seamless stretchable fabric such as braided or knitted fabrics. Such a system also includes means for inflating the confinement with a fluid upon the occurrence of a collision. The inflating means inflates the confinement to a predetermined shape upon a collision, the shape being determined by characteristics of the vehicle interior space and relative position of the passenger.

Stretchable fabric provides resistance to tear and may be constructed of a wide variety of materials. Optionally, an elastomer or other curable coating may be applied to the fabric and is preferably cured or cross linked thereon. The coating, when used, illustratively ranges in thickness from 0.5 to 10 mils.

The present invention also relates to a method for manufacturing such inflatable confinements for use in protecting an occupant of a vehicle during a collision. This method comprises providing a mold having an exterior

surface forming the desired shape, and conforming a fabric to the exterior surface of the mold. Optionally, the method further comprises an additional step of applying a coating to the fabric. If required, the coating may be cured by heat or other suitable curing mechanism.

Detailed Description of the Invention

The present invention is a method and apparatus for protecting occupants of vehicles during sudden impact by way of an inflatable confinement comprising a stretchable seamless fabric wherein the inflatable confinement is formed by conforming the fabric to the exterior surface of a mold to form a three dimensional structure. The fabric may be coated, preferably with, an elastomer, which may be cured to form a coated fabric article.

More specifically, a mold is created in the shape of the desired product. The mold may take on a variety of shapes, and may have complex portions such as concave areas. Furthermore, the mold is preferably collapsible, so as to be easily removed from the finished product. Additionally, bladder type inflatable molds may be employed to form products of similar shapes but of different dimensions. Alternatively, molds may be created from plaster of Paris, frangible materials, cardboard, or a wide variety of materials which can easily be made to break, dissolve, disintegrate, melt or the like so as to be separated from the fabric.

Collapsible type molds such as those incorporating a double-umbrella type structure may also be employed in the present invention. Such a double-umbrella type structure illustratively comprises, in collapsed form, a tubular shaped member which has a number of struts connected by suitable fabric, similar to an umbrella. Upon extension of the struts, an open umbrella configuration is

achieved. Advantageously, two such sets of struts are provided in an end to end fashion such that a suitable confinement configuration is created upon expanding the tubular shaped member and extending the struts. In such an embodiment, a stretchable fabric would be applied over the collapsed structure, which is then extended. Alternatively, the fabric is applied over the extended structure to form the confinement. The mold may be collapsed to facilitate removal of the confinement.

It is not necessary, however, for a mold to deform, disintegrate, etc. , depending on its shape and dimensions and the desired shape and dimensions of the finished product. If removal of the finished product from the mold can be accomplished without tearing the product, and without subjecting the product to undue forces, a rigid mold is suitable for use with the present invention.

When applied to an inflatable mold, the fabric may be applied with the mold at least partially deflated, i.e., not in its fully inflated state, so as to facilitate application of the fabric. Once the fabric is applied, the inflatable mold is inflated to the shape of the desired end product. The degree to which the inflatable mold is deflated at the time of application of the fabric is partially determined by the amount of stretch to which the fabric may be subjected to during the inflation of the mold without tearing or otherwise deforming the fabric. After application of the fabric, the mold is preferably inflated so as to be slightly smaller than the desired end product so as to allow for stretch caused by the sudden inrush of fluid during the inflation process. The degree to which the inflated mold is smaller than the desired end product will depend on the specific type and quantity of elastomer and fabric, the velocity, quantity and flow of the fluid entering the confinement during inflation, the type of deflation system employed, as well as other factors. Rigid

mold sizes, and inflated mold sizes for the case of an inflatable mold, of approximately three to twenty-five percent less than the size of the desired end product have been successfully employed. The neck, or collar, area of the confinement is not produced with a reduced size such that it will properly mate with a mechanism used to join the confinement to the pyrotechnic or gas producing means employed to deploy the confinement. Additionally, an inflatable mold may be deflated to facilitate removal of the fabric after the air bag is formed.

If a braided fabric is employed, the fabric may be conformed to the exterior of the mold by braiding the fabric over the mold's exterior surface. Thus, the fabric takes on the shape of the exterior surface of the mold. If an inflatable mold is used, the mold will be inflated to a predetermined size corresponding to the shape of a fully deployed bag. If an elastomer coating is used, it is applied and cured before the mold is deflated.

When an elastomer coating is used, curing by heat also relaxes and sets the fabric so as to permit subsequent stretching of the fabric. The subsequent stretching of the elastomer-coated fabric is approximately from three to twenty-five percent beyond the size of the mold upon which it is heated and is brought about during operation of the device as the fluid rushes in to the confinement.

The term "fabric" as used herein is intended to include all materials suitable for use in making inflatable confinements in accordance with the invention. Stretchable fabric which can be applied over the mold may be any suitable fabric which conforms or may be made to conform to the shape of the mold.

In one embodiment of the stretchable fabric, the fabric is knit on production units such as what is known in the art as "Tricot", "Rashel", "Simplex" or "Weft" machines. These illustrative machines produce a circular

or "stocking-like" product in which bands of increasing or decreasing fabric density may be introduced by increasing or decreasing the number of yarn ends in a tube of the device. Advantageously, desired confinement configurations may be obtained by employing non-uniform fabric density in the stocking-like confinement. Such non-uniform density allows, for example, a high degree of expansion in a body portion of the confinement and a low degree of expansion in a neck and a toe portion of the confinement, i.e., a reinforced neck and toe portion.

Illustrative materials for knitted fabric include natural or synthetic fibers, plastic, metal, fiberglass or any other material which may be made to take on a desired shape. A preferred stretchable fabric is constructed from yarn or thread of natural, synthetic or regenerated fiber that has been knit into a configuration to allow stretch in both the machine direction and the cross-machine direction. Fabric knit to have stretch of at least 150 percent in each such direction has been found to be suitable for a wide variety of molds. The fabric is relaxed and heat set to permit further stretch during inflation.

Knitted fabrics may be preferable over woven fabrics, especially for complex shapes, since knitted fabrics are generally stretchable in the machine direction as well as in the cross-machine direction, unlike woven fabric. Typical knitted fabrics are used in underwear and socks, and their construction is generally known to one skilled in the art.

Stretchable fabric may be knitted from a yarn having a filament or spun configuration which suitably enhances the fabric by elongating under tension and shrinking and/or relaxing when exposed to heat. This configuration is also referred to as "core-spun".

In another embodiment, a braided fabric is employed. Braided fabric is easily formed into three

dimensional shapes of predetermined size and configuration without cutting and sewing together of two dimensional pieces. The fabric strength holds the size and configuration of the shaped confinement and prevents tearing even under the pressures of inflation and impact.

If a braided fabric is used, the yarn to be formed over the mold is intended to include all materials suitable for use in making inflatable confinements in accordance with the invention. Illustratively, such yarns may be constructed from plastic, metal, natural fibers such as wool, silk, or cotton, synthetic fibers such as polyester, nylon, or rayon, fiberglass and the like, however, polyester or nylon yarns are preferred. Braided fabrics may be preferred over knit fabrics, especially for complex shapes, since braided fabrics have high multiaxial strength and low stretchability, unlike knit fabrics.

A preferred braided fabric is constructed from textile yarn or thread of natural, synthetic or regenerated fiber that has been interlocked into a configuration which provides multiaxial strength and low stretchability. Fabric braided to have stretch of 10-50 percent at break has been found to be suitable for a wide variety of molds.

Fabric may be braided into a wide variety of shapes, without cutting and sewing together individual pieces. This advantageously allows the formation of complex shapes without bulky seams. Seamless construction also provides for a higher fabric strength using smaller yarns since there is no compromise in the tensile and tear strength of the material as created by seams. This further reduces the time and material wasted by tailoring a fabric to a complex shape.

Braided fabric includes strands of multiple fibers which are interlocked by diagonally crossing a number of strands in such a way that each strand alternates over and under one or more of the other strands. A three

dimensional structure is formed by braiding yarns over and around the shape of a mold having the desired final shape. The braiding conforms the yarns to the shape of the mold by the intermeshing of the yarns which locks them into the shape of the mold.

A fabric produced by braiding has a structure wherein the paths of the yarns are not parallel to the fabric axis. Therefore, braided fabrics do not have warp and filling yarns in the sense of a woven fabric. Instead, only the warps may be considered to intersect as a plain weave (one over one) or a basket (two over two) . This configuration provides a fabric which combines good physical properties such as flexibility and high bursting strength at relatively low cost.

In addition, the interlocking strand configuration of braided fabrics provides a higher strength than woven fabric having sewn seams. This is so because there is no compromise in the tensile and tear strength of the material which would be created by seams. This in turn allows the braided fabric to utilize smaller yarns. As a result, the bulk of articles using this braided fabric is reduced by both the smaller yarns and the seamless construction which offers a further advantage.

Braided fabric is preferably made from a yarn having a filament or spun configuration which suitably enhances the tensile strength and shrinking and/or relaxing of the fabric when exposed to heat.

Another embodiment of the invention relates to the use of a coating upon the fabric. A wide variety of coating materials may be used, but thermoplastic and elastomer coatings are preferred. The elastomer coating may be used with any type of fabric in accordance with the present invention. The elastomer coating comprises any suitable material which renders the fabric essentially non-porous and non-permeable. Such material preferably has

a sufficiently long shelf life and tends not to become brittle with age or temperature extremes. Additionally, in the event that pyrotechnic means are employed to inflate the confinement, the elastomer must be especially heat resistant to protect the fabric. Illustrative of suitable materials are chloroprene, nitrile, silicone, acrylic, urethane, butyl, ethylene propylene diene monomer elastomers (EPDM) , or a combination of these and/or other suitable materials. Thermoplastics such as polyethylene, polypropylene and polyvinyl chloride can also be used. Additionally, coatings disclosed in U.S. Patent No. 3,807,754 to Rodenbach et al. which is incorporated herein by reference may be employed with the present invention.

The coating is applied in a sufficient amount to render the fabric either essentially non-porous and non- permeable to air or semi-permeable to control air flow under typical operating conditions. Permeability of the air bag may be adjusted by adjusting the amount and the areas of deposited coating. A range of one-half mil to ten mils has been found suitable for coating thickness, with two to seven mils being preferable.

Application of the coating may be effected by any of a number of known means such as spraying onto the fabric, dipping the fabric into the coating, brushing the coating onto the fabric, or slush coating techniques. Additionally, the mold upon which the braided fabric is formed may be rotated as the coating is applied.

Upon application of curable elastomers to the mold-supported fabric, the elastomer may be cured by curing methods such as by the application of heat. Additionally, the elastomer may be cured by radiation curing, in which the elastomer is exposed to a prescribed type and dose of radiation. Radiation curing permits the use of short curing times and also promotes a uniform curing of the elastomer. Aerobic or moisture cure mechanisms may be

employed as required by the coating chemistry.

Advantageously, with a stretchable fabric, the curing operation serves not only to cure the coating, but also to relax and heat set the threads or yarn of the fabric such that the fabric may be stretched to a greater extent than without such curing. In other words, even under circumstances in which it is necessary to stretch the fabric to its limit so as to conform to the mold shape, the fabric, once it has been relaxed and heat set by the curing operation, may be further stretched without tearing the fabric. Thus, when the air bag is inflated by inflating means such as pyrotechnic or gas supply, the air bag will take on the dimensions required by the specification.

Lastly, the air bag is removed from the mold by an appropriate method. If an inflatable mold was employed, the mold is first deflated and then the air bag is removed. Alternatively, a disintegratable or frangible rigid mold can be utilized in which case the mold is first disintegrated,, dissolved, broken, etc. and then the air bag is removed. If a rigid mold is employed with a stretchable fabric, the air bag can be stretched and removed from the mold.

Upon removal of the air bag from the mold, the air bag is preferably reversed such that the untreated side of the fabric is exposed so as to conform to typical specifications in the air bag industry.

Inflating means is provided to quickly inflate the confinement during a collision and illustratively is a pressurized fluid or pyrotechnic system. The fluid utilized is preferably a gas.

The cured air bag is preferably provided with means for deflating such that the air bag may absorb more net energy from the impact of a person. If no such deflating means were provide, the energy absorbed by the air bag from the impact of a person would be momentarily

stored in the air bag as potential energy in the form of increased air bag pressure, and then expended in forcing the person away from the air bag with the same violent force with which he impacted the air bag and hence, rebound.

Consequently, the inflatable confinement is preferably provided with means for deflating same which means is operative during and/or after the inflating process so as to prevent rebound of the occupant engaging the confinement. By providing means for controlling the deflation of the air bag, the energy absorbed by the air bag from the impact of a person is released by the air bag, however, it is not released in a manner harmful to the person.

The deflating means preferably may be ports in the air bag through which the fluid may escape as the person impacts the air bag. Any number of such ports as will properly absorb the energy of impact may be provided. Alternatively, a blowout patch or tear strip such as that disclosed in U.S. Patent No. 3,451,693 to Carey which enlarges as pressure within the air bag increases may be provided.

As a further example, the deflation means may comprise a fabric material having a density or compactness which renders the confinement at least semi-porous. Also, portions of the fabric structure may remain uncoated to achieve this result. In this embodiment, the spaces or gaps between the fibers in the uncoated portion would provide means through which fluid escapes during impact of the person.

While it is apparent that the invention herein disclosed is well calculated to fulfill the objects above stated it will be appreciated that numerous modifications and embodiments may be devised by those skilled in the art, and it is intended that the appended claims cover all such

modifications and embodiments as fall within the true spirit and scope of the present invention.

More specifically, the present invention is not limited to use in automobiles. The fabric may be used as an inflatable confinement for protecting persons in trains, planes, boats or any other application requiring inflation of a confinement having specified shape. Furthermore, the inclusion of and the specific type, percent coverage, and quantity of elastomer applied to the fabric, if any, may depend on the desired shape, size, stretch and placement of the confinement.