ln time of locking,locking sheet rotates anticlockwise under the action of its torsion spring,form an internally side-spinning torque M to pop up lock blade and prevent rotation of lock blade,and compensate the gap between lock blade and lock latch to make lock latch contact plastic base.Under the action external force,lock body has upward trend and Iock blade has downward moving trend.When external force reaches certain value,lock latch will bounce off locking sheet.Stop hook restricts rotation of lock blade to ensure safe action.After external force disappears,driven by torsion spring,locking sheet makes lock blade return to original position and make lock latch contact plastic base.