| 摘要 |
<p>A feed beam for a rock drill comprises a box girder (13), a saddle (10) slidable along the box girder, and two power units (20,20a) inserted into the ends of the box girder. Each power unit comprises a pair of fixed pulleys (22,24) located outside the end of the box girder, an hydraulic jack (26) carrying a pair of movable pulleys (28,30) within the box girder, and a cable coupled between the power unit and the saddle and passing over the four pulleys.</p> |
