Ford Motor Company is the first automaker to bring an “inflatable seat belt” to market. The concept of a folded bag within a belt is so simple it could start a trend in the auto industry.
The new belts combine the functions of seat belts and airbags to provide added protection for rear seat occupants who do not have the benefit of conventional airbags, but rely on seat belts for protection. During a crash, seat belts alone can concentrate pressure severe enough to cause injury, especially to young and very old occupants who can be more susceptible to head, chest and neck injuries.
Developments in airbag inflation technology and seat belt construction methods have made it possible to create inflatable seat belts that deploy over a vehicle occupant’s torso and shoulder in the event of a crash. The belt is a hollow sleeve where an airbag, folded like an accordion bellows, is inserted.
The inflatable belt functions just like a conventional seat belt, except that it feels more comfortable because of the padding provided by the enclosed airbag material and the rolled edges of the belt. The inflatable belt was demonstrated recently to a group of automotive writers and we agreed that the belt was quite comfortable. Ford research shows that the majority of consumers who have worn the inflatable belt under demonstration conditions consider it similar to or more comfortable than a regular seat belt.
Ford’s designers think the comfort factor could help improve the 61 percent rear belt usage rate in the U.S., which compares to 82 percent usage by front seat passengers, according to National Highway Traffic Safety Administration data.
“Ford is pioneering inflatable seat belt technology to help enhance crash safety protection, while encouraging more people to buckle up with a more comfortable belt,” said Paul Mascarenas, Ford vice president, engineering, global product development.
In the event of a crash, the vehicle crash-sensing system determines when the inflatable belt should deploy. During deployment, cold compressed gas, flows through a specially designed buckle from a cylinder housed below the seat into the inflatable belt’s accordion-folded bag. The expanding bag breaks through the belt fabric as it is filled with air, expanding sideways across the occupant’s body.
The use of compressed gas instead of the gas from a chemical reaction eliminates the pyrotechnic aspect of bag deployment. It also allows the belt to fill at a lower pressure and a slower rate than traditional airbags, because the device does not need to close a gap between the belt and the occupant. Full deployment takes place in 40 milliseconds.
“It’s a very simple and logical system, but it required extensive trial and error and testing over several years to prove out the technology and ensure precise reliable performance in a crash situation,” said Srini Sundararajan, safety technical leader for Ford research and advance engineering.
The inflated belt helps distribute crash force energy across five times more of the occupant’s torso than a traditional belt, which expands its range of protection and reduces risk of injury by spreading crash pressure over a larger area, while providing additional support to the head and neck. The inflatable belt is compatible with child safety and booster seats.
The lap portion of the belt is the same as standard seat belt material. It does not inflate, but has its own retracting mechanism. After deployment, the belt remains inflated for several seconds before dispersing its air through the pores of the airbag.
Ford plans to offer inflatable rear seat belts on the next-generation Ford Explorer, which goes into production in 2010, and eventually in its vehicles globally. — by Dave Van Sickle, Motor Matters
Copyright, Motor Matters, 2009