Hydraulic oil-circuit system and hydraulic jack

A hydraulic jack, comprising:

• an outer oil barrel, a handle being arranged on the outer oil barrel;
• an inner oil barrel, the outer oil barrel being fitted over the inner oil barrel and movable relative to the inner oil barrel, the outer oil barrel and the inner oil barrel forming a storage oil chamber;
• a hydraulic cylinder arranged in the inner oil barrel and movable along an axial direction of the inner oil barrel in a sealing manner, wherein an oil loading chamber and the storage oil chamber are disposed at two ends of the hydraulic cylinder, respectively, a piston is arranged in the hydraulic cylinder and divides an interior of the hydraulic cylinder into a first hydraulic oil chamber and a second hydraulic oil chamber, the first hydraulic oil chamber has a first oil port, the second hydraulic oil chamber has a second oil port, the first oil port and the second oil port are both configured to be in unidirectional communication with the oil loading chamber to allow unidirectional flow from the first oil port and the second oil port to the oil loading chamber, the first oil port and the second oil port are both configured to be in unidirectional communication with the storage oil chamber to allow unidirectional flow from the storage oil chamber to the first oil port and the second oil port, and the hydraulic cylinder has an oil unloading pipeline connecting the oil loading chamber with the storage oil chamber;
• and
• a piston rod having a first end connected to the piston and a second end connected to the handle, wherein the handle drives the piston to reciprocate through the piston rod to change volumes of the first hydraulic oil chamber and the second hydraulic oil chamber, and one of the first oil port and the second oil port is configured to deliver hydraulic oil to the oil loading chamber, while the other of the first oil port and the second oil port sucks oil from the storage oil chamber.