In a seat belt pretensioner device, comprising a seat belt buckle which is supported in a moveable manner, a power generator for moving the buckle in a direction to increase a tension of the seat belt, and a reverse preventing device for preventing the reversal of the movement of the buckle, the reverse preventing device consists of a ball-type one-way clutch defining a plurality of chambers between an inner race and an outer race, each of said chambers narrowing in a rotational direction and receiving a ball and a spring urging the ball toward a narrower part of the corresponding chamber, and the springs are formed by bending a plurality of projections integrally formed in a peripheral part of a single disk shaped plate member into a wavy form. Thus, the multitude of springs are formed by a single member, and not only the management of component parts is simplified but also the assembly work for the one-way clutch is facilitated even when the one-way clutch is not adapted to be formed as a subassembly.
A seat belt pretensioner mechanism (40) includes a part (36) for attachment to the seat belt (20). A strap (50) is connected to the part (36). A piston (78) and piston rod (58) are movable in a first direction to move the strap (50) and the part (36) to tension the seat belt (20). A pivot connection (59, 62) between the piston rod (58) and the strap (50) causes the strap to move with the piston rod. A cam (70) pivots the strap (50) about the pivot connection (59, 62) and effects movement of the part (36) toward the piston rod (58) as the piston (78) and the piston rod move in the first direction.
A buckle pretensioner system includes a substantially L-shaped rail for guiding a buckle body of a buckle from a position where the buckle body engages with a tongue plate to a position corresponding to a lumbar region of a vehicle occupant. When a vehicle disposed with the buckle pretensioner system undergoes a sudden deceleration, a piston inside a cylinder is moved in a frontward direction of the vehicle by gas generated by the actuation of a gas generator, a buckle stay is pulled by a wire coupled to the piston, and the buckle stay is moved along the shape of the rail. As a result, the buckle body supported by the buckle stay pivots from the position where the buckle body engages with the tongue plate to a vehicle occupant restraining position of a webbing belt, and then is pulled to the lumbar region-corresponding position.
