Abstract: The present creation is focused on providing structural improvements to the locking device by pivotable installing a windlass in the interior body of the lock for winding the steel cable, also installed at one lateral side is a single-direction ratchet gear, with a rotary spring bent at another lateral side to drive the windlass, and a stopper of the locking mechanism controlled by the core of the locking device set at one lateral side of the windlass to cope with a compressed spring; a tenon and mortise are fixed onto the stopper corresponding to the single-direction ratchet gear, and at the end of the steel cable a ring is used to connect it with the locking pin on the steel cable or at the extreme end of the U-shape rod. When the locking pin is locked together with the body of the locking device, the safety helmet and other articles can then be locked firmly.