| 摘要 |
PROBLEM TO BE SOLVED: To reduce manufacturing cost, and achieve compactness by simplifying a plunger pump 15, and hydraulic circuit structure, and simplifying operation structure for the plunger pump 15. SOLUTION: In this hydraulic jack device, a hydraulic cylinder 5 for loading/ unloading work is driven by a plunger pump 15. A plunger head 35 is provided on a plunger 19 to be put into/out of a cylinder main body 33 of the plunger pump 15, and a pressure chamber 36 and a back pressure chamber 37 are formed inside the cylinder main body 33 through the plunger head 35. A change-over valve 41 for generating slow lifting action of the hydraulic cylinder 5 by delivery oil from the plunger 19 by short-circuiting the pressure chamber 36 with the back pressure chamber 37, and an operation member 47 to open the change-over valve 41 when working fluid pressure of the hydraulic cylinder 5 is a prescribed value or more are provided. COPYRIGHT: (C)2004,JPO
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