| 摘要 |
In the present invention, a spring is mounted on a hinge device for opening and closing a manhole cover and is used to lift the manhole cover with a small amount of force by using the elasticity of a spring. When the manhole cover is closed, the present invention can also use the elasticity of the spring to adjust the speed of the manhole cover being closed to prevent the occurrence of safety accidents. Also, the spring is not exposed to the outside from the hinge device to reduce the risk of damage. The present invention also ensures low manufacturing costs and can be easily installed by anyone. |
