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Lear Stops Whiplash with Dynamic Head Restraint

Lear uses custom system to meet new U.S. and European standards

Doug Smock, Contributing Editor -- Design News, September 30, 2008

Lear Corp. is using a mechanical system featuring custom assembly equipment to meet brand-new head restraint safety systems required by the Insurance Institute for Highway Safety, European New Car Assessment Program and the new Federal Motor Vehicle Safety Standard (FMVSS 202a).

The U.S. mandate requires automakers to either install in all front-row seats a solution for a dynamic option, such as ProTec PLuS, or for a static option, such as firmer and larger head restraints that are closer to an occupant's head. "Lear's ProTec PLuS dynamic system allows for a more comfortable seating system and greater design flexibility than a static solution," says Don Bernhardt, vice president of seat engineering in a Lear statement. "Additionally, ProTec PLuS, if activated, resets itself automatically."

The riveting assembly system was developed jointly with engineers from Avdel who described the system at the Assembly Technology Expo in Rosemont, IL on Sept. 23. "In rear impact collisions, the passenger's body is forced back into the seat, deploying a mechanism that pivots a mechanism up and forward to cushion the passenger's head," says R.A. Karby, applications engineer at Avdel. "This lightning-quick response significantly reduces the force and movement of the occupant's neck."

One key to the assembly is a highly repeatable process that joins three parts: the head restraint harp frame and two small stamped steel brackets with plastic bushings. The brackets are the core component that pivots the headrest up and forward. The role of the bushings is to prevent noise and rattle during operation of the car.

Five sensors ensure the assembly is accurate, says Karby. Sensors, for example, monitor and balance force and distance of rivet application strokes. "If a hole is too large, if a bracket is missing or if a part isn't quite correct, the system senses these problems and will not cycle," says Karby. Other sensors test for the presence of the plastic bushings. "If all process parameters fall within predetermined limits, the application is date- and time-stamped and can be archived for future reference," says Karby.

The workstation uses Avdel Stavex steel breakstem rivets with a unique crimp design which provides a wide grip range, which provides a smooth bubble formation on the back side of the application. High shear and tensile strength eliminate the need for several grip fasteners.

The assembly process takes about 22 sec. The first car to use the system is the 2009 Cadillac STS.

Three mechanical parts are the backbone of Lear’s new head-restraint system.

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Talkback

• This system looks a lot like the SAHR (SAAB Active HeadRest) That has been around for a number of...
  Eric Thomas - 2008-10-04 09:45:58

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