Importance

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Abstract

A linear seat belt pretensioner includes a housing with a sealed axial cavity and a piston (52, 152, 232, 352, 452) slidable in the cavity. A gas generator (76, 166, 156, 376, 476) deploys into the axial cavity, thereby propelling the piston outward. Because the axial cavity is well sealed, the arrangement retains the gas pressure upon deployment and is capable of a restart after a partial displacement if additional slack develops. The piston travels by a distance (X) corresponding to the piston travel and shortens the length of seat belt webbing available outside the pretensioner device by twice or thrice the distance (2X). The axial cavity can be sealed with a bladder element, such as a rolling sock (38). Alternatively, the seal may be established by a hollow piston (152) forming a ballistic seal with the wall of the cavity under pressure.

First Claim