| 摘要 |
a support plate (1) provided with an annular support portion (1a) having a predetermined curvature in contact with the floor; a rotational body (2) having a rotational ball (2a) and a round bar (2b) projecting from the top surface of the rotational ball (2a); a disk-shaped fixed body (3) securely fixed into the screw hole (1b) of the support plate (1) via a bolt (4) and provided with a fixed hole (3a) for the round bar (2b) fitted thereinto; and a fixed plate (5) connected to the jack (6) and coupled with the round bar (2b) via a bolt (7) to support the rotational body (2).
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