70 Occupant protection Tensioning process · 6913 Belt tensioners with belt-force limiters

911 Body equipment, exterior 6 70 Occupant protection Tensioning process 6913 Belt tensioners with belt-force limiters For model year '02, all 911 models are fitted with belt tensioners and belt-force tension- ers. 6_01_02 1 Ball arrester 2 Tube with propellant charge 6_07_02 3 Gas pressure 4 Pistons The pyrotechnic ball belt tensioner is com- 5 Pinion bined with the belt-force limiter in one unit. 6 Mass body (balls) The threshold value for triggering the pyr o- technic belt tensioner is calculated as for the The balls are driven through a pyrotechnic airbag actuation from the sensor signals for propellant charge. vehicle deceleration. The triggering of the This kinetic energy is carried over to the belt belt tensioner during a frontal collision takes reel via a pinion. place together with the triggering of the front Belt slack is taken up by winding in belt. airbags. During a rear collision only the belt tensioner is triggered. Belt-force limiters To avoid bruising and internal injury, the belt's pulling force must be limited to a bear- able level. Further tensioning beyond a dangerous pull- ing force level is prevented. The belt can be balanced up to a certain length via a torsion shaft in the belt mecha- nism. 2002 Service Information 6 - 9