SAFARI

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 called since the

pretensioner device is mounted in the

retractor unit. The main function 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

unit essentially consists of a ball 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