Abstract: A link for rolling steel door link formed of a body and a cover plate covered on the body, the body having two short coupling tubes and a peripheral flange at one side, the cover plate having two coupling holes respectively coupled to the coupling tubes of the body and a peripheral flange abutted against the peripheral flange of the body, the end of each short coupling tube being expanded by a punch press to fixedly secure the cover plate to the body after its insertion through the respective coupling hole on the cover plate.

Abstract: A motor drive for a rolling steel door which includes a motor and a speed reducer driven by the motor to take up/let off the rolling steel door. A brake disk is rotated with the motor shaft of the motor, a sprocket wheel is moved along an axle and forced by a spring into engagement with the brake disk to stop the motor shaft of the motor from rotation. An electromagnet is securely mounted on the axle and magnetized to attract the sprocket wheel for enabling the motor shaft of the motor to rotate freely upon starting of the motor. A lever operated by hand disengages the sprocket wheel from the brake disk. A control box is coupled to the power output shaft of the speed reducer to control the operation of the motor, wherein when the control box is controlled to start the motor, the electromagnet is magnetized to attract the sprocket wheel from the brake disk and enables the motor shaft of the motor to be freely rotated.