| 摘要 |
<p>An impact tool for striking a tool (16) such as a chisel includes a piston (18) mounted in a cylinder (15). Upper (25), middle (28) and lower (29) chambers are formed therebetween. Pressure oil is fed into and discharged from the middle and lower chambers to reciprocate the piston in the cylinder under oil pressure. During a downward stroke of the piston, the oil pressure in the lower chamber is kept low. But just before it strikes a tool, the oil pressure is adapted to increase so as to prevent what is called cavitation or prevent air bubbles mixed in the pressure oil in the lower chamber from growing suddenly owing to a sharp drop in the oil pressure which is caused by the rebound of the piston after striking the tool.</p> |
