To obtain a sufficiently high working speed through a relatively little quantity of generated gas without causing large sizing or an increase of cost.
A pretension device for automatically increasing the tension force of a seat belt in the case of a vehicle collision accident is composed to have a base plate 11 for fixing the whole device to the side of a seat; an arm 12 which is pivoted on the base plate 11 at one end and is connected to the anchor part 8a of a buckle at the other end; a cylinder substantially fixed to the base plate 11; a piston whose working end is connected at a position separated from the pivoting center on a pivoted end side of the arm as far as a proper radial distance; a linear drive actuator 13 having a gas generating agent charged in the cylinder bottom; and a reverse rotation preventing mechanism 15 for prescribing the rotating direction of the arm in only one direction. Thus a rotating arm for giving displacement to the buckle and the piston of the actuator can be substantially directly connected, and at the same time, since it can be driven by force in a direction where a piston rod is pushed out from the cylinder, the pressure receiving area of the piston can be taken larger.
YAMAGUCHI HIRONORI
SHIMIZU EIJI
OI TOMOHARU
| JPH03114948A | 1991-05-16 | |||
| JPH0635061U | 1994-05-10 |