Electro-mechanical actuator equipped with a mechanical brake of coil spring type
An actuator having a frame which is fixed to an electric motor; a gear drive for transmitting motion from the motor to a drive shaft between two predetermined positions, and a brake consisting of a coil spring, having, when relaxed, an inside diameter that is smaller than the outside diameter of a support shaft that is fixed relative to the gear drive, and around which the spring is coiled, each of the two free ends of the spring being arranged in a respective slot, formed in the frame.
1. An actuator of an electro-mechanical type comprising:
a frame;
an electric motor fixed to the frame;
a gear drive for transmitting motion from the motor to a drive shaft such that the drive shaft can rotate between two predetermined positions, the gear drive and the drive shaft also being fixed to the frame; and
a brake for braking the drive shaft, the brake consisting of a coil spring having turns and two free ends, having, when relaxed, an inside diameter that is smaller than an outside diameter of a support shaft that is fixed relative to the gear drive, and around which the spring is coiled, each of the two free ends of the coil spring being arranged in a respective slot formed in the said frame transversely to the support shaft, the arrangement of each of the two free ends of the coil spring being such that only one end comes into transverse engagement against an edge of the slot, while the other end is free in the slot in the transverse direction,
wherein the brake has a braking force limited to an opening force needed for opening the turns of the spring and is controlled as a function of the position of the drive shaft in such a way as to be:
activated after the drive shaft has reached a position corresponding to the power supply to the motor being broken; and
released when the drive shaft is in a position between the two said predetermined positions.
2. An actuator according to claim 1 , wherein the mechanical brake is actuated by transverse displacement in one direction of a member which is itself displaced by the gear drive so as to put the one end into transverse engagement against the edge of the slot while leaving the other end free in the slot in the transverse direction.
3. An actuator according to claim 1 , wherein the mechanical brake is disabled between the two predetermined positions of the drive shaft, the brake being disabled by transverse displacement of the said member in a direction opposite to one direction, so as to exert a thrust transversely on at least the free end of the coil spring, to put said free end into transverse engagement against the edge of said slot by fully opening turns of the spring around the support shaft.