| 摘要 |
A drilling boom 10 is pivoted about a first axis 12 or 14 on a base and is pivoted about that axis by a first hydraulic cylinder 15 or 17. It carries a feeder beam carrier 21 at its forward end. The carrier 21 is pivoted at the forward end of the boom 10 about a second axis 22 or 24 which is parallel to the first axis 12 or 14, and it is moved about the second axis 22 or 24 by a second hydraulic cylinder 25 or 28 in a sense opposite to that in which the boom 10 is moved by the first cylinder 15 or 17. The first and second cylinders are so dimensioned and hydraulically interconnected that fluid which is expelled from the first cylinder 15 or 17 actuates the second cylinder 25 or 28 and vice versa. The angular movements of the boom 10 and carrier 21 are equal in magnitude. <IMAGE> |
