JPS57179406A - Fluid actuator - Google Patents

Abstract

PURPOSE:To achieve a fluid actuator suitable for a pile hammer which functions in accordance to the resonance of the pile for the inherent frequency of the soil by providing a relief valve in a two flow paths conducting with the actuator chambers as the bypass circuit. CONSTITUTION:The pressurized oil from a pump 1 will enter through a rotary direction exchange valve 2 and through the paths 17, 18 alternatively into the liquid chambers 13, 14 of a cylinder 8 to move a piston 52 up and down thus to drive a pile 11. When the pile will resonate with the inherent frequency of the soil, the amount of oil to be fed from the pump to one of the liquid chambers 12, 13 will be insufficient while the other liquid chamber will be excessive, but the pressure difference across the check valves 19, 20 is detected by the relief valves 27, 28 to open the relief path to conduct the liquid chambers 13, 14 thus to compensate the amount of oil thereby the up-down motion of the piston 52 will follow well to the frequency increment due to the resonance resulting in the positive driving utilizing the resonance.