| 摘要 |
<p>PURPOSE:To make the smooth and heavy duty operation of a hydraulic cylinder possible, by making the front and rear sides of the said cylinder communicate with each other when a piston rod is under no load or a light one. CONSTITUTION:An automatic control valve 'A' with a spool 25 functioning when the delivery pressure of a hydraulic pump 2 has resin up to a fixed pressure and a pilot check valve 'B' closing when a hydraulic cylinder 11 is in its inoperative state are provided between the hydraulic cylinder 11 and a four port and three position type directional control valve 4. Therefore, when the hydraulic cylinder 11 is under no load or a light one, the spool 25 keeps its unchanged over state to make the front and rear sides of a piston 12 communicate with each other. Thus since the said sides become under the same hydraulic pressure, the piston 12 can advance at high speed. When loading has increased, the spool 25 changes over to act the higher hydraulic pressure only on the rear part of the piston 12, and thereby the working force of the piston 12 becomes stronger. Thus the smooth and heavy duty operation of the hydraulic cylinder can be performed.</p> |
