PURPOSE: To provide a simple and inexpensive device by forming a hydraulic circuit in which one booster is driven into pre-pressurizing, pressurizing, and intake strokes by a hydraulic pump, and another booster is driven similarly by another hydraulic pump.
CONSTITUTION: A booster 1 is driven by a hydralic pump 11 and a hydraulic cylinder 6a to perform the pre-pressurizing, pressurizing, and intake strokes, and a booster 2 is driven similarly by a hydraulic pump 12 and a hydraulic cylinder 6b. Rod-chamber side ports Pr of the boosters 1, 2 are then connected to each other by means of a line 23 provided with a back pressure setting check valve 24 to supply the pressure oil discharged from the advancing side booster to the returning side booster to accelerate the returning action. Thus, even when an accumulater is not provided on the delivery lines 15, 16 of the hydraulic pumps, load fluctuations in the hydraulic pumps 11, 12 can be reduced. As a result, the displacements of the hydraulic pumps can be reduced, manufacturing cost can be reduced, and the device can be miniaturized.
HANEHIRO TAKUICHI
HAYASHI KOICHI
NODA TAKAAKI
