SAFARI

10 AIR BAGS SRS 4. WORKING OF RPLL BELTS Retractor Pretensioner and Load Limiter configuration belts (RPLL) should only be used with airbags. The belts essentially comprise of two elements. a) Retractor Pretensioners The pretensioner is so cal led since the pretensioner device is mounted in the ret ractor uni t . The main funct ion of a pretensioner is to remove slack from the belt in the event of an accident to reduce forward movement of the occupant. The pretensioner uni t essent ial ly consists of a bal l cage comprising of a tube of steel balls surrounding a toothed wheel (Refer fig 3). The wheel is mounted on the belt-webbing spool. When the ECU senses a crash, depending on the crash severity, it sends a "fire" signal to the squib in the belt pretensioner. The firing of the squib causes displacement of the balls in the tube. The movement of the balls causes rotation of the toothed wheel, which in turn rotate the webbing spool and removes the slack from the belt. b) Load Limiters Load limiters are to be used only in airbag- equipped vehicles. Load limiters are provided to limit the seat belt loads to a pre-defined value. The load limiter fitted inside the retractor unit is basically a torsion bar (Refer fig 4). Whenever the belt load increases beyond the pre-defined limit, some length of the belt is released due to twisting of the torsion bar. The activation of the load limiter does not depend on signal from the ECU. Note : The inflated Airbag system will not function again and steering wheel with Airbagmodule, steering column, seat belts and control module (ECU) must be replaced immediately. If passenger Air bag is fitted Airbag assembly, Airbag cover seat belts & dash panel must be replaced. Fig.3 Fig.4 Igniter