The end of the service life of the ground spring is due to oil leakage and weakened elasticity of the axis. If the axis line between the sky axis and the ground spring spindle is not strictly perpendicular to the ground, the movement of the door leaf will bring large torque to the ground spring, increase wear between the spindle and bearings, and cause oil leakage of the axis. Springs inevitably weaken their elasticity after long-term stretching movements. In addition, everyone can also pay attention to this.