| 摘要 |
<p>A rock drilling rig comprising a first boom member (12) connected to a carrier (11) by a universal joint (13) and a second boom member (14) being longitudinally displaceable relative to the first boom member by a hydraulic cylinder (18) inside the second boom member. The external surface of the hydraulic cylinder is provided with lands (25) and intervening grooves (26) into which ridges (27) on second boom member (14) extend. A rotary motor (17) at the rear end of first boom member (12) rotates the second boom member by rotating the hydraulic cylinder. <IMAGE></p> |
