| 摘要 |
A rotatable cylinder, a threaded cylinder and a center threaded rod are sequentially inserted in their mutually threadingly engaged states in the inner side of a guiding inner cylinder part which is vertically disposed at the case body through an inner periphery thread and an outer periphery thread. A large bevel gear disposed at a lower end part of the rotatable cylinder is threadingly engaged with a small bevel gear which is borne by the case body, a thrust bearing having a large inside diameter is sandwiched between the large bevel gear and a bottom plate of the case body, and the center threaded rod is provided at its upper end face part with an engagement part for preventing the rotating motion of the center threaded rod when engaged with a jack attachment part of a body to be lifted up such as an automobile. A surrounding cover deformable only in accordance with the motion of upward extension and downward contraction of the threaded cylinder and the center threaded rod is interposed between the upper end part of the center threaded rod and the case body. Moreover, The threaded cylinder and the center threaded rod are such dimensioned in length that in their downward contraction states, the lower end parts are passed through the inside diameter of the thrust bearing having a large inside diameter and abutted with the upper surface of the bottom plate of the case body.
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