AIR BAG

For years, the trusty seat belt provided the sole form of passive restraint in our cars.  There were debated about their safety, especially relating to children. But over time, mush of the country adopted mandatory seat-belt laws.  Statistics have shown that the use of seat belts has saved thousands of lives that might have been lost in collisions.

Air Bags have been under development for many years. The attraction of a soft pillow to land against in a crash must be very strong – the first patent on an inflatable crash-landing device for airplanes was filed during World War II.  In the 1980’s the first commercial air bags appeared in automobiles.

Since 1988, all new cars have been required to have air bags on both driver and passenger sides (Light Trucks came under the rule in 1999).  To date, Statistics show that air bags reduce the risk of dying in a direct frontal crash by 30 percent.  Newer than steering Wheel mounted or Dashboard-mounted bags, but not so widely used, are seat-mounted and door mounted side air-bags.  Some experts say that within the nest few years, our cars will go from having dual air bags top having six or even eight air bags.  Having evoked some of the controversy that surrounded seat-belt use in its early years, air bags are the subject of serious government and industry research and tests.

THE BASICS OF AIR BAGS

Before looking at specifics, let’s review our knowledge of the laws of the motion. First, we know that moving objects have momentum (the product of the mass and velocity of an object.  Unless an outside force acts on an object, the object will continue to move its present speed and direction.  Cars consist of several objects, including the vehicle itself, Loose objects in the car and, of course, passengers.  If these objects are not restrained, they will continue moving at whatever speed the car is traveling at, even if the car is stopped by a collision.

Stopping an object’s momentum requires force acting over a period of time.  When a car crashes, the force required to stop an object is very great because the car’s momentum has changed instantly while the passengers’ has not much time to work with.  The goal of any supplemental restraint system is to help stop the passenger while doing as little damage to him or her as possible.

What an air bag wants to do is to slow the passengers’ speed to zero with little or no damage.  The constraints that it has to work within are huge.  The air bag has the space between the passenger and the steering wheel or dashboard and a fraction of a second to work with.  Even that tiny amount of space and time is valuable, however, if the system can slow the passenger evenly rather than forcing an abrupt halt to his or her motion.

The idea of using a rapidly inflating cushion to prevent crash injuries has a long history.  The first patent on an inflatable crash-landing device for airplanes was filed during World War II.

Early efforts to adapt the air bag for use in cars bumped up against prohibitive prices and technical hurdles involving the storage and release of compressed gas.

If there was enough room in a car for a gas canister.

Whether the gas would remain contained at high pressure for the life of the car. 

How the bag could be made to expand quickly and reliably at a variety of operating temperatures and without emitting an ear-splitting bang.

They needed a way to set off a chemical reaction that would produce the nitrogen that would inflate the bag.  Small solid-propellant inflators came to rescue in the 1970’s.In the early days of auto air bags, experts cautioned that the new device was to be used in tandem with the seat belt.  Seat belts were still completely necessary because airbags worked only in front-end collisions occurring at more than 6 Kmph.  Only Seat belts could help in side swipes and crashes (Although side-mounted air bags are becoming more common now), rear end collisions and secondary impacts.  Even as the technology advances, air bags still are only effective when used with a lap/Shoulder seat belt.

WORKING OF AIR BAGS

Air Bags are designed to inflate in frontal or frontal-angle impacts in which the car strikes an immovable object at more than about 16 Kilometers per hour or another car at twice that speed.  After a collision, sensors sense an electric current to an igniter system or, in some cases, to the computerized control unit.  This unit evaluates the situation and then sends an electrical impulse to the igniter system.  The electric current heats a filament (wire), which then ignites a capsule.  The Ignited capsule supplies the heat to ignite gas-generating pellets.  In most systems, the pellets are made of sodium azide and produce nitrogen gas when they burn.  In other systems, pressurized argon gas is used instead.  The gas then expands quickly and inflates the airbag, which then breaks through a plastic cover in the steering wheel or, the dashboard on the passenger side.  The whole process takes about 0.1 second from the exact moment the crash is detected.  The air bag starts to deflate immediately, venting the harmless gas through holes in the back of the bag of the through the fabric itself.

CONCLUSION

The air bags are of greater importance in today’s vehicles since safety of human life is of prior importance.  Since the count of automobiles is increasing tremendously on our roads, the probability of accidents is also more.  So far a safe riding and for saving the precious life the safety bags must be implemented.  Today it is the prevail age of the high class people who own high priced cars.  Lets hope every automobile manufacturers implement the same since safety for life is inevitable.