| 摘要 |
A hingeable derrick, comprising an upper structure with a first face and a second face opposite the first face; a lower structure with a first face and a second face opposite the first face; a hinge connecting the second face of the upper structure to the second face of the lower structure; and at least one hydraulic cylinder, where each hydraulic cylinder has an upper end attached to the upper structure. The upper structure is located directly above the lower structure in an upright position when the hydraulic cylinder is retracted, and the upper structure may pivot at the hinge in the direction of the second face into a folded position, with the descent controlled by winch lines. |
