ACTUATOR WITH NON-REVERSIBLE SCREW-AND-NUT SYSTEM, DRUM BRAKE AND BRAKING DEVICE PROVIDED WITH SAME

摘要

The invention relates to an actuator with a screw-and-nut system, in particular for actuating the brake shoes of a drum brake of a motor vehicle. The invention also relates to a drum brake and a braking device provided with such an actuator. The linear actuator includes a transmission sub-assembly driven by a rotary motor and driving a linear actuator assembly. Said assembly includes a rotary element and a second element engaging with one another by means of respective male and female threads in order to form a screw-and-nut system. The actuator is arranged such as to press the brake shoes selectively against the drum of the brake, separating the first ends of the brake shoes from one another when the rotary element is rotated via the transmission sub-assembly. The helix angle β of the threads of the screw-and-nut system is smaller than the angle of friction φ, with a deviation of no more than 3% of the value of the angle of friction, for example β = 0.98 x φ.