Take-up mechanism for safety belts

摘要

A take-up mechanism for safety belts in vehicles comprises an automatic belt winding assembly which is connected to a windup assembly which includes a motor having a piston which rotates relative to an associated cylinder to drive the belt winding assembly in a direction to tighten the belt, for example when an emergency arises such as a potential accident. The drive motor includes a piston having a vane portion rotatably mounted in a cylinder so that either the piston or the cylinder is rotatable for a short rotation period upon the ignition of a pyrotechnical drive charge which when ignited provides a propellent for driving the motor. The construction of the mechanism is such that kinetic energy stored in the rotating masses of a clutch are used to effect a positive coupling of the take-up mechanism with the shaft carrying the wound up seat belt. The drive motor thus has a limited rotational path which is shorter than the length of the belt portion to be retracted. The clutch mechanism is such that it locks during the windup operation and then disengages in the manner of an overrunning clutch.