Patent ID: 8231073

Claim:
A seat belt retractor for a motor vehicle seat belt restraint system for storing seat belt webbing and having a retractor locking device responsive to inertial loads acting on the vehicle, the retractor comprising: a force limiter to permit the restricted paying out of the seat belt webbing with the absorption of energy by deformation of the force limiter, the force limiter having a first section with a relatively high energy absorbing level and a second section with a relatively low energy absorbing level, a control mechanism operable to switch the force limiter from the first energy absorbing level to the second energy absorbing level in response to a crash related electric signal, wherein an initial belt force in excess of a predetermined force causes a deformation of the first section, and the deformation caused by the initial belt force in excess of the predetermined force prior to the electric signal disables the control mechanism, and wherein an initial belt force below the predetermined force does not cause the deformation.