Coating processes – With post-treatment of coating or coating material – Heating or drying
Reexamination Certificate
2000-03-17
2001-10-23
Cameron, Erma (Department: 1762)
Coating processes
With post-treatment of coating or coating material
Heating or drying
C427S389900
Reexamination Certificate
active
06306462
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to air bags of the type utilized in vehicle occupant restraint systems. More particularly, the present invention relates to fabric suitable for use in such air bags.
For some time, vehicle manufacturers have been equipping their products with air bag systems to supplement the protection offered by seatbelts. These air bag systems utilize at least one folded air bag in fluid communication with a source of inflation gas. When a collision is detected between the vehicle and another object, the source of inflation gas is actuated to inflate the air bag.
Air bags have traditionally been of two types, i.e., driver side and passenger side. More recently, some vehicle manufacturers have also begun providing air bags designed for side-impact protection. Air bags of a particular type will be constructed to satisfy unique operating characteristics of that type. For example, driver side air bags have frequently been made from coated fabric or uncoated fabric of very low permeability. Passenger side air bags have often been made from uncoated fabric of slightly higher permeability.
Several primary fabrics have been utilized in the production of vehicle air bags. An early fabric widely employed for driver side air bags was woven from 840 denier yarn into a thread count of approximately 25×25 and coated with 1-2 ounces per square yard of neoprene rubber. As demand increased for reduced packaging in driver side applications, the industry moved toward smaller denier yarns of a higher thread count. For example, fabrics woven from 420 denier yarn into thread counts of approximately 49×49 or 46×46 were utilized.
As intended, these 420 denier fabrics successfully provided the reduced packaging sought by vehicle manufacturers. Because the denier and tensile strength of the yarn had been reduced, however, the yarn had to be slashed with a suitable sizing compound, such as polyacrylic acid (PAA), prior to rapier weaving. The greige cloth, stiff and boardy due to the sizing compound, then had to be scoured prior to use. Scouring was also necessary to remove residual spin finish which, along with the size, had a tendency to prevent good adhesion of the neoprene coating compound. With the additional processing of slashing and full scouring, the cost of the fabric was increased.
The additional cost of sizing and scouring was also seen in another important fabric. This fabric, which has been used primarily in passenger side applications, was woven into a 32×32 ripstop configuration from 840 denier yarn. Size was used despite the stout nature of 840 denier yarn because the beat-up at the fell of the cloth was very tight, often causing chafing of unsized yarn during the weaving process.
Much of the world market has traditionally been processed using conventional rapier weaving technology because of its versatility and quality. Typical rapier goods were very dense in construction, like the 49×49 420 denier fabric discussed above, as well as 60×60 315 denier or 41×41 630 denier fabrics.
Recently, some fabric makers began using water jet weaving as an alternative method of producing air bag fabric. An advantage of water jet weaving is that some normal process steps can be eliminated or reduced. For example, improvements in the overall quality of the yarns themselves often allow water jet looms to be run without size on the warp yarns. The chilled water holds and protects the unsized warp yarns during cloth formation, whereas these yarns could be bruised and frayed when run dry on a rapier loom machine. The scouring process can be eliminated since size was not used and the spin finish on the yarns is partially broken down during the weaving process and is brought down to previous market levels of acceptability through normal heat setting of the fabric.
Although water jet weaving has certain advantages, it also has various drawbacks. One significant drawback for air bag fabric is a relatively wide variation in air permeability across the fabric web. In particular, water jet weaving has a tendency to blossom the fabric, particularly at the edges. As such, the side-center-side permeability of the fabric will generally not be as consistent as rapier goods.
In addition, greige cloth produced on a water jet loom must be dried to prevent growth of mildew. In addition, water jet looms have traditionally required a more difficult changeover process when it is desired to weave a different type of fabric on a particular loom. Water jet looms also tend to be less flexible with respect to on-loom constructions and the quality of the fabric can be inconsistent.
SUMMARY OF THE INVENTION
The present invention recognizes the foregoing and other disadvantages of prior art constructions and methods. Accordingly, it is an object of the present invention to provide improved air bags for use in a motor vehicle.
It is also an object of the present invention to provide improved fabrics for use in a vehicle air bag.
It is also an object of the present invention to provide improved methods of producing fabric suitable for use in vehicle air bags.
It is a more particular object of the present invention to provide improved methods of producing air bag fabric using a rapier loom machine.
It is also an object of the present invention to provide improved methods of producing coated fabric suitable for use in vehicle air bags.
It is also an object of the present invention to provide improved methods of producing uncoated fabric suitable for use in vehicle air bags.
Some of these objects are achieved by an air bag for use in a motor vehicle. The air bag comprises a plurality of panels connected together about their respective peripheries to define an interior cavity for receipt of an inflation medium therein. At least one of the panels includes an unscoured fabric having an air permeability of less than approximately 5.0 CFM and a circular bend of less than approximately 2.2.
In some exemplary embodiments, the panel is constructed substantially entirely of uncoated fabric. The uncoated fabric may include polyester yarn, such as 650 denier or 440 denier polyester yarn. Alternatively, the uncoated fabric may includes nylon yarn, such as 420 denier nylon yarn.
Other objects of the invention are achieved by fabric suitable for use in a vehicle air bag. The fabric has a plain weave construction of synthetic multifilament yarn of a size no greater than approximately 650 denier. In addition, the fabric is unscoured and has an air permeability of less than approximately 5.0 CFM, as well as a circular bend of less than approximately 2.2. In some exemplary embodiments, the air permeability falls generally within a range of 1-4 CFM and the circular bend falls generally within a range of 1.1-2.2.
Still other objects are achieved by a method of making a fabric constructed of multifilament synthetic yarn and suitable for use in a vehicle air bag. One step of the method involves providing a beam of warp yarns that are unsized throughout substantially their entire length. A cloth is produced from fill yarns and the warp yarns utilizing a rapier loom machine having at least six (6) harnesses for producing an alternating shed through which the fill yarns are inserted. Preferably, the rapier loom machine has a number of harnesses falling in a range of six (6) to ten (10). More than ten (10) harnesses may be used, but will often not be preferred because of a tendency to slow loom operation. For example, the rapier loom machine may be equipped with eight (8) harnesses. The cloth may then heat set without scouring.
According to preferred methodology, the yarn utilized in the fabric may exhibit certain desirable characteristics. For example, at least the warp yarns may have approximately evenly-spaced nodes of entanglement along a predetermined length. Depending on various factors, approximately twelve (12) to twenty-five (25) of such nodes of entanglement per meter of yarn is generally suitable for this purpose.
The multifilament synthetic yarns may be pol
Cameron Erma
Nelson Mullins Riley & Scarborough
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