Seat Belt Retractor: Description and Operation

GF91.60-D-4042H Front Emergency Tensioning Retractor, Component Description








Shown on driver-side

10 Emergency tensioning retractor unit
R12/1 Driver GUS squib
R12/2 Front passenger GUS squib

Location

The emergency tensioning retractor units are each located behind the paneling in the B-pillars and, on vehicles with code (S23) Two-seater front passenger seat, in the bench seat.







Design shown on driver emergency tensioning retractor unit

10 Emergency tensioning retractor unit
17 Ball collector
a Drive gear
b Seat belt reel
c Reel shaft (stabilizer bar)
d Clutch plate
e Locking lever
f Spring
g Locking plate
R12/1 Driver GUS squib







A Emergency tensioning retractor not active
B Emergency tensioning retractor activated
C Emergency tensioning retractor active

Function

When the seat belt is buckled and the plausibility check carried out by the control unit that is installed depending on the variant in combination with the driver seat belt buckle switch (S68/1) is positive, an electric ignition pulse for triggering the driver emergency tensioning retractor squib or the front passenger emergency tensioning retractor squib is sent starting at a certain deceleration or acceleration when an accident occurs. After triggering, the respective squib ignites the respective solid fuel in the respective gas generator. When the respective solid fuel is burning off, the respective bursting disk is opened, which then releases the compressed gas from the respective pressure reservoir; the gas is routed via the respective filter into the respective roller tube. The balls located in the respective roller tube are pressed through the respective drive gear, causing the respective seat belt reel to rotate. The respective seat belt reel rolls up the respective seat belt at a defined length thus tensioning the seat belt. The respective balls then fall back into the respective ball collector.

This design is combined with a belt force limiter.

A distinction between the equipment variants is made as follows:
- Lowline airbag control unit (N2/14), except code (SH6) thorax bag for driver (in seat backrest), except code (SH7) Thorax bag for driver and front passenger (in seat backrest) and except code (SH9) Window bag for driver and front passenger
- Highline airbag control unit (N2/15), with code (SH6) Thorax bag for driver (in seat backrest), with code (SH7) Thorax bag for driver and front passenger (in seat backrest) or with code (SH9) Window bag for driver and front passenger

Belt force limiter

The respective emergency tensioning retractor unit is equipped with a force limiter, which consists of the respective reel shaft (stabilizer bar), the respective clutch plate and the respective locking lever. After tensioning of the seat belt, the force limiter reduces the force of the seat belt on the body of the occupant if an accident occurs without impairing the protective effect of the seat belt.

Mechanical locking system

In a further accident, the normal protective function of the seat belt is retained. The respective reel shaft is then locked up by the locking system and assumes the entire load without tensioning and force limitation.

If the ignition stage was not triggered during an accident, the respective emergency tensioning retractor unit must be disposed of properly. In Germany disposal is possible through the Mercedes-Benz Recycling System "MeRSy". In all other countries, please observe applicable regulations.