| 摘要 |
<p>PURPOSE:To facilitate piping work in a valve block for single-rod double acting hydraulic cylinder of hydraulic rock drill by combining an extension oil passage and a contraction oil passage connected to a hydraulic cylinder with a check valve, pilot check valve and communication passages, and then forming a circuit which carries out acceleration upon extension while locking upon stoppage. CONSTITUTION:Upon extension of a hydraulic cylinder 9 oil is supplied to an extension oil passage 14 via a direction changeover valve 27 from a hydraulic pump 28. With the cracking pressure of a third check valve 21, then, a second pilot check valve 24 is opened, and oil is flowed in a side oil chamber 13 through a communication passage 22, contraction oil passage 16, second communication passage 25 and first pilot check valve 18, whereby a piston rod 11 is moved leftward. Then, oil in a rod side oil chamber 15 returns to the head side oil chamber 13 from the passage 25 and the check valve 18. Upon contraction, the oil supplied to the passage 16 enters the rod side oil chamber 15 to move the piston rod 10 to thereby return the oil in the head side oil chamber 13 to a tank.</p> |
