Land vehicles – Wheeled – Attachment
Reexamination Certificate
2001-05-29
2002-04-02
Culbreth, Eric (Department: 3611)
Land vehicles
Wheeled
Attachment
C280S729000, C280S730100
Reexamination Certificate
active
06364350
ABSTRACT:
BACKGROUND
The present invention pertains to vehicle safety devices and more particularly pertains to a motor vehicle occupant safety device.
Airbags were phased in to the U.S. motor vehicle fleet beginning in the mid-1980s when the Department of Transportation (DOT) required some form of automatic frontal crash protection for front seat occupants. The requirement was modified by the Congress in 1991 to an air bag mandate. All passenger cars in the U.S. must offer dual front air bags by Model Year 1998, and light trucks the following year.
Present air bag systems consist of four major parts: (1) a set of electronic sensors; (2) microprocessor; (3) polyamid bag; and (4) a gas generator. The sensors, commonly located in the front of the car, and the microprocessor constantly compute impulses of speed, acceleration, shocks, and braking patterns and compare them with data of crash patterns stored in the microprocessor. In the case of an accident, the microprocessor evaluates the severity of the crash and sets off the gas generator only if the car speed exceeds 20 mph. Although analysis shows that air bag systems are working generally as intended, these systems still have some drawbacks.
The first set of problems deals with the gas generator and gas flow control means which air bag manufacturers use for inflating their air bags. To ensure maximum protection it is vital that the air bag inflate in a matter of milliseconds. The fastest air bag systems to date depend on highly reactive substances, including sodium azide, which is toxic. Sodium azide inflators are comprised of aluminum-encased units that contain an igniter (squib), gas generant pellet or wafers of sodium azide, propellant and filters to screen out combustion products.
The sodium azide combustion reaction begins when the vehicle collision sensing means produces an electrical signal upon collision which ignites a few milligrams of initiator pyrotechnic material. That then ignites several grams of booster material which then ignites the sodium azide. Besides extreme heat, the reaction produces free sodium and nitrogen gas.
2 NaN
3
(s)→2Na-3N
2
(g)
The free sodium from the combustion reaction can form sodium hydroxide when it contacts the water in people's noses, mouths, eyes and so forth. To prevent this, manufacturers mix in chemicals that will produce sodium salts on combustion, thus neutralizing the sodium.
Sodium azide inflator units often have a layer of matted material formed of alumina and silica in the particulate filter. This material is supposed to react with any of the remaining free sodium in the generated gas. Corn starch and talcum powder are also used as lubricants in the bag, and if the bag explodes, which is often the case when the structural liner fails because of the heat and force of the blast, these powders, as well as chemical residues from the reaction, contaminate people.
Sodium azide is toxic, and the mixture of chemicals is environmentally hazardous when not totally used up during the deployment of the air bag, or if only partially-combusted. Thus, sodium azide inflators pose a threat to the environment and must be disposed of according to government regulations.
Another set of problems with air bag systems today deals with the fact that present air bags inflate too aggressively. Not only does the rapid rate of the chemical reaction produce an explosive percussion which shatters the vehicle's windows and the occupant's ear drums, out the expanding nitrogen gas blasts the air bag, which is hard or stiff due to its structural liner, toward the occupant at speeds of approximately 200 mph. Thus, the National Highway Traffic Safety Administration (NHTSA) is very concerned that current air bag designs have adverse effects in some situations.
As of June 1996, NHTSA's Special Crash Investigation program had identified 21 crashes in which deployment of the passenger-side air bag resulted in fatal injuries to a child. Six of these deaths were to infants in rear-facing child seats. The other 15 children appear to have been unrestrained or improperly restrained (e.g., wearing only the lap belt with the shoulder belt behind them) at the time of the crash. According to NHTSA, all of these cases involved pre-impact braking. This combination of no, or improper, belt use and pre-impact braking resulted in the forward movement of the children such that they were close to the instrument panel and the air bag system at the time of the crash and the deployment of the air bag. Because of this proximity, the children sustained fatal head or neck injuries from the deployment of the passenger-side air bag. Thus, NHTSA has requested that so called “smart” air bags be developed and introduced into automobile fleets.
As defined by NHTSA, smart air bags are (1) ones which would prevent the air bag from deploying in situations where it might have an adverse effect, based, for example, on the weight, size and or location of the occupant, or (2) ones designed so that they would deploy in a manner that does not create a risk of serious injury to occupants very near the bag.
Vehicle manufacturers and air bag suppliers have produced some alternative designs. Among these are (1) a pressure sensitive mat in the passenger-side seat to deactivate the passenger-side air bag, unless a certain predetermined threshold weight is detected on the mat, (2) a rear-facing child seat detection “tag” which would deactivate the air bag upon detecting a rear-facing child seat equipped with a special tag and (3) a manual cutoff switch for turning off the passenger-side air bag system when, for example, a rear-facing child seat is positioned in the passenger seat. These proposed solutions are impracticable, unreliable and are not ready for production.
First, for the pressure sensitive mat to function the way it is intended, the child must be seated properly. However, as the statistics show, children appear to have been unrestrained, improperly restrained or out-of-position and in close proximity to the air bag at the time of the crash. Thus, it is unlikely the mat would significantly reduce injuries to this class of occupants. Additionally, a pressure sensitive mat and its electronic components are subject to wear and tear and may give no indication when they are worn, defective and in need of replacing.
Second, tag systems are inconvenient and costly. The corroborative efforts necessary between vehicle and/or air bag manufacturers and child seat manufacturers means an increase in the price of a “tagged” rear-facing child seat. Additionally, retrofitting existing rear-facing child seats with tags, as well as compatibility issues with multiple tag technologies, is likely to make these systems lag behind in their introduction into the auto safety restraint industry.
Third, manual switches depend on human operators; one may easily forget to turn on a manual cutoff switch after turning it off.
Finally, it is important that a motor vehicle occupant safety system meet original equipment manufacturer's (OEM) specifications and government standards and be economically feasible to implement into all foreign and domestic fleet automobiles.
Therefore, it is highly desirable to provide a new motor vehicle occupant safety device.
It is also highly desirable to provide a new motor vehicle occupant safety device that is capable of controlling the rate at which the air bag inflates.
It is also highly desirable to provide a new motor vehicle occupant safety device which inflates an air bag faster than prior inflator systems.
It is also highly desirable to provide a new motor vehicle occupant safety device which does not require the use of toxic chemicals, chemicals which generate extreme heat and/or cold or neutralizing or lubricating substances.
It is also highly desirable to provide a new motor vehicle occupant safety device which does not require complicated gas production, separation and flow control means.
It is also highly desirable to provide a new motor vehicle occupant safety device which does not cause a loud explosion.
It is
Culbreth Eric
Unique Technologies, L.P.
Woodard Emhardt Naughton Moriarty & McNett
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