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.
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