A hydraulic jack is provided which comprises a piston cylinder, a piston rod, an oil passage switching valve and an internal cylinder. The oil passage switching valve is provided with an oil outlet; a one-way valve assembly preventing the backflow of the oil outlet passage is disposed between the first oil inlet passage and the oil outlet passage; a return oil inlet passage is disposed at the bottom of the piston head; a return oil chamber in communication with the return oil inlet passage is disposed inside the piston head; a return oil outlet passage communicating the return oil chamber and the piston cylinder oil storage chamber is disposed on the piston head; a one-way return oil assembly is mounted in the return oil chamber, thus the hydraulic oil does not enter the hydraulic area and finally the top plate will not rise continuously along with pressing, providing overload protection.

A hydraulic jack is provided which comprises a piston cylinder, a piston rod, an oil passage switching valve and an internal cylinder. The oil passage switching valve is provided with an oil outlet; a one-way valve assembly preventing the backflow of the oil outlet passage is disposed between the first oil inlet passage and the oil outlet passage; a return oil inlet passage is disposed at the bottom of the piston head; a return oil chamber in communication with the return oil inlet passage is disposed inside the piston head; a return oil outlet passage communicating the return oil chamber and the piston cylinder oil storage chamber is disposed on the piston head; a one-way return oil assembly is mounted in the return oil chamber, thus the hydraulic oil does not enter the hydraulic area and finally the top plate will not rise continuously along with pressing, providing overload protection.

A hydraulic lifting column for medical devices includes a hydraulic cylinder unit, a base element, a carrier element, at least one intermediate element and at least one first engaging member arranged on the carrier element and formed separately from the carrier element. The hydraulic cylinder unit is configured to move the lifting column along a travel axis between a retracted position and an extended position. The at least one intermediate element is disposed between the base element and the carrier element at least in the retracted position. The carrier element and the at least one intermediate element can be moved relative to the base element along the travel axis by the hydraulic cylinder unit acting on the carrier element. The first engaging member abuts against the intermediate element when the lifting column is moved between the retracted position and the extended position and drives the at least one intermediate element.

A hydraulic lifting column for medical devices includes a hydraulic cylinder unit, a base element, a carrier element, at least one intermediate element and at least one first engaging member arranged on the carrier element and formed separately from the carrier element. The hydraulic cylinder unit is configured to move the lifting column along a travel axis between a retracted position and an extended position. The at least one intermediate element is disposed between the base element and the carrier element at least in the retracted position. The carrier element and the at least one intermediate element can be moved relative to the base element along the travel axis by the hydraulic cylinder unit acting on the carrier element. The first engaging member abuts against the intermediate element when the lifting column is moved between the retracted position and the extended position and drives the at least one intermediate element.

A hydraulic jack includes an oil cylinder, an oil tank, and an oil storage barrel. The oil storage barrel includes a front portion and a back portion which are opposite to each other; an oil outlet of the oil cylinder is connected with an oil inlet at the front portion of the oil storage barrel by means of an oil inlet pipe; and an oil inlet of the oil tank is connected with an oil outlet at the front portion of the oil storage barrel by means of an oil outlet pipe, the oil inlet pipe and the oil outlet pipe are provided with switching valves for alternatively turning on the oil inlet pipe and the oil outlet pipe. A partition plate that is capable of moving along a barrel wall and an elastic telescoping member are provided inside the oil storage barrel.

A hydraulic jack includes an oil cylinder, an oil tank, and an oil storage barrel. The oil storage barrel includes a front portion and a back portion which are opposite to each other; an oil outlet of the oil cylinder is connected with an oil inlet at the front portion of the oil storage barrel by means of an oil inlet pipe; and an oil inlet of the oil tank is connected with an oil outlet at the front portion of the oil storage barrel by means of an oil outlet pipe, the oil inlet pipe and the oil outlet pipe are provided with switching valves for alternatively turning on the oil inlet pipe and the oil outlet pipe. A partition plate that is capable of moving along a barrel wall and an elastic telescoping member are provided inside the oil storage barrel.

The lifting mechanism includes a battery, an electric machine, a hydraulic pump, an oil tank, a hydraulic cylinder, a work platform and a proportional valve or switch valve. In the energy-regeneration mode, the hydraulic fluid drives the hydraulic pump to operate as a hydraulic motor, thus in turn driving the electric machine to operate as a generator and charge the battery. In the present application, the hydraulic pump operates to increase a pressure in a hydraulic line between the hydraulic pump and the proportional valve or switch valve before the proportional valve or switch valve is switched from a unidirectional communication position to a bidirectional communication position. When the proportional valve or switch valve is switched from the unidirectional communication position to the bidirectional communication position, by increasing the pressure in the hydraulic line, it could be avoided that the volume of hydraulic fluid has low pressure is compressed because the hydraulic fluid has low pressure is communicated with hydraulic fluid has high pressure; therefore a state of sudden drop of the work platform is avoided, and safety performance and operating experience of the lifting mechanism is improved.

The lifting mechanism includes a battery, an electric machine, a hydraulic pump, an oil tank, a hydraulic cylinder, a work platform and a proportional valve or switch valve. In the energy-regeneration mode, the hydraulic fluid drives the hydraulic pump to operate as a hydraulic motor, thus in turn driving the electric machine to operate as a generator and charge the battery. In the present application, the hydraulic pump operates to increase a pressure in a hydraulic line between the hydraulic pump and the proportional valve or switch valve before the proportional valve or switch valve is switched from a unidirectional communication position to a bidirectional communication position. When the proportional valve or switch valve is switched from the unidirectional communication position to the bidirectional communication position, by increasing the pressure in the hydraulic line, it could be avoided that the volume of hydraulic fluid has low pressure is compressed because the hydraulic fluid has low pressure is communicated with hydraulic fluid has high pressure; therefore a state of sudden drop of the work platform is avoided, and safety performance and operating experience of the lifting mechanism is improved.

A hydraulic jack is provided which comprises a piston cylinder, a piston rod, an oil passage switching valve and an internal cylinder. The oil passage switching valve is provided with an oil outlet; a one-way valve assembly preventing the backflow of the oil outlet passage is disposed between the first oil inlet passage and the oil outlet passage; a return oil inlet passage is disposed at the bottom of the piston head; a return oil chamber in communication with the return oil inlet passage is disposed inside the piston head; a return oil outlet passage communicating the return oil chamber and the piston cylinder oil storage chamber is disposed on the piston head; a one-way return oil assembly is mounted in the return oil chamber, thus the hydraulic oil does not enter the hydraulic area and finally the top plate will not rise continuously along with pressing, providing overload protection.

A hydraulic jack is provided which comprises a piston cylinder, a piston rod, an oil passage switching valve and an internal cylinder. The oil passage switching valve is provided with an oil outlet; a one-way valve assembly preventing the backflow of the oil outlet passage is disposed between the first oil inlet passage and the oil outlet passage; a return oil inlet passage is disposed at the bottom of the piston head; a return oil chamber in communication with the return oil inlet passage is disposed inside the piston head; a return oil outlet passage communicating the return oil chamber and the piston cylinder oil storage chamber is disposed on the piston head; a one-way return oil assembly is mounted in the return oil chamber, thus the hydraulic oil does not enter the hydraulic area and finally the top plate will not rise continuously along with pressing, providing overload protection.