PURPOSE: To average and reduce the pulsation of outputted hydraulic pressures of both hydraulic pressure bases by a method wherein the output from one hydraulic base is initiated by the rotation of a rotary valve rotating integrally with a crank shaft when the output of pressure fluid from the other hydraulic base is closed to the terminal end thereof.

CONSTITUTION: When an air cylinder device 2 is in a suction stroke, compressed air flows into an air pipe 22 through the air feeding groove 60 of a valve case 6, the air feeding path of the rotary valve 7 and an air feeding chamber to retreat a piston 21 in a cylinder 20. Accordingly, a plunger 23 is positioned at the most retreated location in the hydraulic pressure base 3 and a hydraulic pressure chamber 31 is filled with the hydraulic pressure fluid through an oil feeding pipe 30, an oil feeding path 31 or the like. In this case, a connecting rod 24, supported by the piston 21 through bearings, pushes the eccentric section 54 of the crank shaft 5 to rotate the crank shaft 5 and the rotary valve 7 and pushes the connecting rod 24 of another air cylinder device 2a at the symmetrical position thereof to advance the piston 21 and the plunger 23 and effect air discharging effect. According to this method, the hydraulic pressure fluids from each hydraulic pressure bases are joined and the pulsation thereof is averaged and reduced.