| 摘要 |
<p>A mobile drilling apparatus having a support structure, a mast positioned on said support structure, a drill head and a hydraulic assembly vertically operable on and guided by said mast. The hydraulic assembly moves the drill head and includes lower hydraulic cylinders rigidly connected to the mast and upper cylinders, each mounted inside and connected rigidly to a tube. A piston rod with connected upper and lower pistons is movable within the upper and lower hydraulic cylinders. The drill head is connected to the lower portion of the tube.</p> |
