Carmakers and their parts suppliers began looking at the potential of an inflatable seat belt in the 1970s, seeing it as a way to decrease injuries in a crash, beyond existing safety systems.
But engineering a belt that would still feel and move like a normal seat belt during normal driving, but inflate in an emergency, proved tricky. Either the belt's webbing was too thick and stiff, or normal movement of the retention mechanism was hampered by placing the inflation system inside the same part.
“When Key Safety approached it, we took a step back and thought about [deploying] the gas from the opposite side, from the buckle,” said Mike Moore, director of seat belt engineering for Sterling Heights, Mich.-based Key Safety Systems Inc.
After working both on its in-house development and with customer Ford Motor Co., Key developed the inflatable seat belt as an option for second-row seats of Ford's 2011 Explorer. The belt won the safety category Nov. 9 at the Society of Plastics Engineers' 2010 Automotive Innovation Awards.
In an emergency, the belt will split open and inflate a tubular air bag that will remain inflated for at least at least six seconds.
The belt helps reduce injuries by cushioning the passenger and spreading the chest compression over a larger area, while also holding the passenger in place in a crash. Sensors within the system trigger inflation whenever the car's air bags are also deployed.
Key had to develop its own proprietary seat-belt webbing, woven in-house at its Knoxville, Tenn., facility, to house the air bag but also split apart when needed.
The company also had to work with Ford to find space under the seat to house the inflator system. Cars have so much technology built into them these days, the space under the seat already houses electronics, wiring, heating and venting systems, in addition to standard structural parts, Moore said.
The inflator then sends the gas up through the plastic seat-belt buckle into the belt when it is in use. Key had to make the buckle slightly larger than a standard system to hold the inflation system.
Ford is looking at expanding the inflatable seat belt into other products, Moore said, and future federal safety regulations may help expand the belt system's use.