| 摘要 |
A seat belt tensioning device for a vehicle comprises a cylinder, a piston which is slidably inserted within the cylinder and a piston operating means. The piston is composed of a first and a second cylindrical piston members which are adjacent to each other. The seat belt tensioning device further comprises a rod which is connected to a seat belt and is contacted with the second piston member by passing a deformable member, which is plastically deformed by a predetermined tension force through the first piston member. The deformable member is disposed adjacent to the second piston member and connected to the rod by passing through the first and second members. The rod and the second piston member form a conical continuously inclined surface of which diameter is enlarged in the piston moving direction near the contact portion thereof. Stopper pieces having a sharp end portion are radially supported by the conical continuously inclined surface. When the tension force of the seat belt exceeds the plastically deforming load of the deformable member at an urgent time, such as upon a vehicle impact, the deformable member is plastically deformed by the second piston member and elongated and the stopper pieces are lifted up by the taper portion of the second piston member to cut into the cylinder. As a result, the piston is locked in the cylinder and the kinetic energy of the passenger can be absorbed. Therefore, the passenger is prevented from the secondary impact and the injury due to the tensioned seat belt.
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