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.

The invention relates to a lifting device using fluid as a damping medium to form a driving force. It has an outer tube, an inner tube, a guiding assembly and a spring using fluid as a damping medium to achieve a lifting effect, one end of the inner tube being inserted in the outer tube from one end of the outer tube and being fixedly connected with the guiding assembly, a portion of the guiding assembly being in contact with the inner wall surface of the outer tube to implement rolling friction or sliding friction, one end of the spring being positioned in the outer tube, the other end of the spring penetrating through the inner tube and being connected with the inner tube

The base section for a lifting jack includes upper and lower plates with complementary curved facing and engaging surfaces which allows the barrel of the lifting jack to pivot relative to the ground in use. In a typical lifting jack, the barrel is perpendicular to the ground in use. In the present invention, the base section allows the lifting assembly to pivot relative to the ground up to an angle of 15 from vertical in any direction from vertical.

The base section for a lifting jack includes upper and lower plates with complementary curved facing and engaging surfaces which allows the barrel of the lifting jack to pivot relative to the ground in use. In a typical lifting jack, the barrel is perpendicular to the ground in use. In the present invention, the base section allows the lifting assembly to pivot relative to the ground up to an angle of 15 from vertical in any direction from vertical.

A heavy vehicle lifting apparatus and a hydraulic lifting unit. Each lifting unit has a housing with a displaceable upper portion which has an application surface being engageable with a lifting point of the heavy vehicle. Two or more hydraulic actuators are disposed within the housing and linked with a common fixed structure. Each actuator has an extendable cylinder attached to the upper portion. The cylinders in operation collectively vertically displace the upper portion and the application surface between a first position wherein the application surface is disengaged from the lifting point, and a second position wherein the application surface engages the lifting point and the heavy vehicle is lifted from a ground surface.

A heavy vehicle lifting apparatus and a hydraulic lifting unit. Each lifting unit has a housing with a displaceable upper portion which has an application surface being engageable with a lifting point of the heavy vehicle. Two or more hydraulic actuators are disposed within the housing and linked with a common fixed structure. Each actuator has an extendable cylinder attached to the upper portion. The cylinders in operation collectively vertically displace the upper portion and the application surface between a first position wherein the application surface is disengaged from the lifting point, and a second position wherein the application surface engages the lifting point and the heavy vehicle is lifted from a ground surface.

A utility pole lifting apparatus and method for raising a utility pole in addition to carried transmission cables away from a foundation, without requiring disconnecting or de-energization of the transmission cables. The utility pole lifting apparatus includes a base mounting structure configured to be coupled to the foundation and an upper lifting structure coupled to the base mounting structure and to the utility pole. The upper lifting structure is configured to elevate the utility pole above the foundation while supporting the utility pole and the transmission cables to allow an extension segment to be inserted between the foundation and the utility pole to permanently raise the height of the utility pole.

A hydraulic jack for providing safety and security is disclosed. The hydraulic jack comprises a hydraulic cylinder storing hydraulic fluid inside, and a piston installed in the hydraulic cylinder that is raised up from the hydraulic cylinder by pressure of the hydraulic fluid stored in the hydraulic cylinder, thereby a heavyweight can be lifted by the piston. The piston has at least one drill hole on its body thereof that has a determined diameter and is perpendicular to the piston. A security piece is attachable on a top portion of the hydraulic cylinder. The security piece comprises a pair of through holes, which align with at least one drill hole of the piston.

A hydraulic jack for providing safety and security is disclosed. The hydraulic jack comprises a hydraulic cylinder storing hydraulic fluid inside, and a piston installed in the hydraulic cylinder that is raised up from the hydraulic cylinder by pressure of the hydraulic fluid stored in the hydraulic cylinder, thereby a heavyweight can be lifted by the piston. The piston has at least one drill hole on its body thereof that has a determined diameter and is perpendicular to the piston. A security piece is attachable on a top portion of the hydraulic cylinder. The security piece comprises a pair of through holes, which align with at least one drill hole of the piston.