Analysis of properties of operation of the supporting equipment for the seat belts

Applying the pretensioners and the belt force limiters in cars had a positive impact on the seat belts effectiveness in protecting the people driving against the effects of collisions. In this way, delayed action of the seat belts, resulting from the flexibility of the belt and the operating time of the retractor locking mechanism, was partially eliminated. The tasks and properties of the pretensioners and force limiters used in cars will be described in the paper. Implementations of the forces acting at the driver's lap belts and shoulder belts during a frontal collision into a rigid barrier, at the speed of 56km/h, will be presented. On this basis the properties of the pretensioners and belt force limiters will be determined. The characteristics of rigidity (force displacement) of the shoulder belts of various designs will be presented, too. On the basis of the results of the crash tests (NHTSA, USA) for several cars the dynamic loads, which act on the driver during a frontal collision into a rigid barrier, will be analysed. The biomechanical indices of the human immune to the effects of shock loads will be taken into account. The analysis will include the passenger cars (sedan) from the years 1995 – 2004, which were fitted with the seat belts of various designs.