Electric brake having parking brake function

An electromagnetic braking system comprising:

• a brake stack;
• a ram shiftable in a first linear direction toward and against the brake stack and in a second linear direction opposite the first linear direction;
• a motor having an output shaft mechanically connected to the ram and rotatable in a first rotation direction for moving the ram in the first linear direction and in a second rotation direction for moving the ram in the second linear direction;
• at least one friction member having a friction surface mounted adjacent to the motor output shaft;
• and
• an actuator for moving the friction surface of the at least one friction member against the motor output shaft in a non-locking manner and holding the friction member against the motor output shaft with a predetermined force to perform a park brake function;
• wherein the predetermined force is low enough to allow the output shaft to slip relative to said one friction member when a rotational force on the output shaft exceeds a given level, so that
• said motor is back driven,
• a torque on said shaft is consequently reduced until slipping of said shaft stops, and
• said shaft is again held in position to continue to perform said park brake function.

In an electromagnetic braking system comprising a brake stack, a ram shiftable in a first linear direction toward and against the brake stack and a second linear direction opposite the first linear direction, and a motor having an output shaft mechanically connected to the ram and rotatable in a first rotation direction for moving the ram in the first linear direction and in a second rotation direction for moving the ram in the second linear direction, a method of performing a park brake operation and limiting the braking force applied by the ram to the brake stack as the brake stack cools comprising the steps of:

• a) generating a given output force with the motor;
• b) pressing a friction member against the motor output shaft in a non-locking manner with a predetermined force;
• c) reducing the motor output force;
• d) reapplying the given output force;
• e) moving the friction member away from the output shaft;
• f) moving the friction member against the output shaft;
• g) reducing the motor output force;
• and
• h) holding the friction member against the motor output shaft with the predetermined force while the brake stack cools until after a force applied by the cooling disk stack against the ram causes the output shaft to slip relative to the friction member.