| 摘要 |
A hydraulic impact motor in the form of a water-driven in-hole rock drilling machine has a valve spool (40) that has two equally big and opposite directed control surfaces (A1 and A2). The valve has also a third control surface (A3) which is smaller than the other two and which is continuously under pressure. The third control surface (A3) acts in the same direction as the second control surface (A2). When the first control surface (A1) is under pressure but the second control surface (A2) is not, then the valve is moved in one direction, and when the first and second control surfaces (A1 and A2) is under equal pressure (full pressure or no pressure), then the valve is moved in the other direction by the third control surface (A3). |
