The locking and unlocking characteristics of a seat belt inertial locking system due to acceleration

Abstract

An inertial locking mechanism of a seatbelt is designed to prevent further seatbelt extension when it exceeds an acceleration threshold. The acceleration threshold varies with the orientation of the mechanism and direction of acceleration. A setup and procedure were created to test the acceleration threshold of the inertial locking mechanism of a seatbelt in various orientations. For an example of an inertial locking mechanism a 1984 Ford Mustang seatbelt mechanism was used. During testing, the mechanism was put into an orientation that simulated accelerations that could be seen in normal collisions. The mechanism responded by locking with an average acceleration of 2.535 g. The mechanism was then tested in orientations that would simulate those seen by a vehicle in a rollover situation. In certain orientations, the mechanism was locked while at rest, but became unlocked when accelerated.