Mercedes Benz C-Class (W204) Training Manual: Front Emergency Tensioning Retractors

Restraint/emergency tensioning retractor system

The emergency tensioning retractor in the W204 is a new design of toothed rack retractor tensioner. The functioning principle is based on the fact that an integrated toothed rack, which is fired pyrotechnically, unwinds via a cogwheel connected to the seat belt retractor and thus initiates the belt tensioning.

An integrated, mechanically operating belt force limiter is responsible for generating belt forces which are initially slightly elevated but which then diminish as soon as the airbag has been fully inflated.