| 摘要 |
PURPOSE:To exactly operate spool by a method in which a spool valve to interrupt or connect the upper and lower chambers of the inside chamber of a cylinder for a drop hammer is forcibly operated by a pressure oil introduced into one end portion of the inside of a sleeve. CONSTITUTION:Under a condition that a cap 33 is covered on the upper end of a pile, a frame 6 is set and a drop hammer is operated. When a pilot valve 4 is switched from neutral position to the position (a) by a timer, an oil-pressure switching valve 3 is switched to the position I, and the pressure oil flows in the upper chamber 10 through a conduit 2, the switching valve 3, a conduit 20, the lower chamber 11, and ports 24 and 25. When the pressure of the upper chamber 10 is raised, a spool 23 goes down, the ports 24 and 25 are interrupted, and the sleeve 22 and a weight 32 go up. When the valves 3 and 4 are further switched to the neutral position, the pressure oil of the lower chamber 11 returns to a tank 5 and flows from the tank 1 to the lower part side 22', the spool 23 goes up, and the pressure oil of the lower chamber 11 flows out to the upper chamber 10. Therefore, the weight 32 drops to strike the pile. |
