SEAT BELT TIGHTENING DEVICE

A seat belt tightening device for removing slack in a seat belt when the seat belt is required to positively restrain a passenger, comprising clamp members for clamping a part of the seat belt paid out from a retractor device; a winding member for winding thereonto a portion of the seat belt that is located ahead of the part clamped by the clamp means by a rotary motion; and a drive source for causing a rotational motion of the winding member. The winding member may be either integral with one of the clamp members or separate from both of them. Since the slack of the seat belt is removed simultaneously as the seat belt is clamped, the passenger is effectively restrained in case of a vehicle collision without being thrown forward due to any slack in the seat belt, and since the seat belt is allowed to pass through the tightening device without being obstructed under normal conditions the comfort of the passenger is assured by the action of the retractor which is typically provided in conjunction with the seat belt tightening device.