| 摘要 |
A mast base comprises a rigid body (10) and four supporting legs (15), extending laterally from the body (10) in mutually diverging directions. Each supporting leg (15) comprises an upper arm (17) and a lower arm (18). At its inner end, each arm (17, 18) is pivotally connected to the body (10) for pivoting movement relatively to the body around an appurtenant horizontal pivot axis (x1, x2). At their outer ends, the two arms (17, 18) are pivotally connected to each other. At least one arm (18) has a variable length. The upper arm (17) of each one of two supporting legs (15), which are located at mutually opposite sides of the body (10) and extend in mutually opposite directions therefrom, is pivotally connected to the body (10) by means to two separate pivot joints (19), which are located at a substantial horizontal distance from each other. |
