Range Rover RESTRAINT SYSTEMS Description and Operation - Page 378
RESTRAINT SYSTEMS
75-10
DESCRIPTION AND OPERATION
Pretensioner
1 Seat belt buckle
2 Electrical connector
3 Piston
4 Piston housing
5 Direction of piston travel
6 Expanding gas
7 Squib/Gas generator
8 Steel cable
9 Gaiter
The pretensioners are used to tighten the front seat belts during a collision to ensure the occupants are securely held
in their seats. A pretensioner is integrated into each front seat belt buckle and attached to a bracket on the inboard
side of the seat.
Each pretensioner has a tube containing propellant and a piston. The piston is attached to a steel cable, the opposite
end of which is attached to the seat belt buckle. A squib in the base of the tube provides an ignition source when
triggered by a fire signal from the DCU.
On receipt of a fire signal from the DCU, the squib ignites the propellant. The propellant produces nitrogen gas that
rapidly expands to drive the piston along the tube, pulling the cable and drawing the buckle downwards.