Dynamic brake

A brake mechanism for stopping rotation of a shaft, the brake mechanism comprising:

• a solenoid including a coil and an armature, wherein the armature is attracted in a first direction toward the coil when the coil is energized by current;
• at least one spring biasing the armature in a second direction opposite the first direction;
• an opposing plate spaced from the armature in the second direction;
• a ball carrier rotor arranged between the armature and the opposing plate, the ball carrier rotor having a plurality of ball-receiving recesses angularly spaced about a circumference of the ball carrier rotor, and the ball carrier rotor being mounted on the shaft for rotation with the shaft;
• a plurality of balls received in the plurality of ball-receiving recesses;
• an outer race having a cylindrical internal surface facing the plurality of balls;
• and
• a ramp surface associated the armature or the opposing plate;
• wherein the ramp surface is configured to urge the plurality of balls radially outward against the internal surface of the outer race as the armature moves in the second direction under the biasing of the at least one spring when current to the coil is shut off.

A method of braking a shaft rotating about an axis, the method comprising the steps of:

• providing a plurality of balls arranged about the axis and coupled to the shaft for rotation therewith;
• shutting off current to a solenoid to de-energize a coil of the solenoid;
• applying force to an armature of the solenoid, whereby the armature is displaced along the axis when the solenoid is de-energized;
• converting the axial displacement of the armature into radially directed force applied to the plurality of balls;
• and
• arranging a cylindrical surface about the plurality of balls to oppose the radially directed force.