| 摘要 |
A drilling machine has a drill carriage pivotally mounted on the upper end of a jib whose lower end is pivoted to a support structure. To maintain the drill carriage in parallelism as the jib pivots, two hydraulically interconnected hydraulic jacks are provided, namely a slave jack pivotally connected between the jib and support structure to form a first triangle with its corners at the pivot point of the jib and the two pivot connections of the jack; and a follower jack pivotally connected between the jib and the drill carriage to form a second triangle with corners at the drill carriage pivot point and the two pivot connections of the follower jack. These two triangles are similar triangles. The full-bore end of one of the jacks is connected by a closed hydraulic line to the annular end of the other jack, and the other ends of the two jacks are interconnected by a second hydraulic line provided with, for example, a hydraulic accumulator for accommodating any excess fluid displaced by the interlinked movement of the jacks when the jib moves pivotally. To ensure that the carriage maintains strict parallelism as the jib moves, the ratio of the effective cross-sectional areas of the ends of the two jacks between which the first closed hydraulic line is connected is made to equal the ratio of similarity of the two triangles. |
