| 摘要 |
<p>Conventionally, holes for seismic charges are made by 'pile driven' hollow tubes, the excavated earth being removed by air or water pressure. The disadvantage of this method is that unwanted cavities or compressions can be caused at the bottom of the hole. The alternative method, using 'oil-rig' type drilling equipment is expensive and cumbersome. The present machine uses a hollow tube with cutting teeth, rotated by a hand-held assembly which is clamped around the tube by pneumatic pressure, while three Teflon (RTM)-coated rollers are driven by a pneumatic motor. The loose material drilled out can be blown out using compressed air.</p> |
