A locking device comprising: first and second flanges; and first and second flange locking structures. The first and second flange locking structures are used for selectively locking the first flange and the second flange. Each flange locking structure comprises: a synchronising ring and a driving assembly. The synchronising ring is able to slide relative to the corresponding flange; and the drive assembly is capable of selectively pushing the synchronising ring to slide along the axial direction of the corresponding flange from an unlocked position to a locked position.