The invention provides a connector which comprises a cylindrical body which can be sleeved in a ratchet wheel hollow shaft and a limit step which is fixed at one end of the body, wherein the diameterof the limit step is larger than the diameter of the outer wall of the body; the center of the limit step is provided with a through hole which can be circumferentially limited with an output shaft ofa motor; the outer wall of the body is provided with at least two grooves which are extended along the axial direction of the body and uniformly distributed along the outer wall of the body; each groove is internally provided with a steel spring piece and a plastic friction pad from the inside out sequentially; and the addition of the thickness of the steel spring piece and the thickness of the plastic friction pad is larger than the depth of the grooves, thus the output shaft of the motor cannot have locked rotation, thereby avoiding generating high current and better protecting the motor.