A method of retrofitting a trailer having a crank jack with a jack housing and a jack leg into a hydraulic jack includes removing mechanical components from within the jack housing, the mechanical components comprising gearing of the crank jack, placing a hydraulic cylinder within the jack housing, wherein the hydraulic cylinder comprises a main cylinder and a ram piston extending outwardly therefrom as the main cylinder is filled with pressurized fluid, securing the hydraulic cylinder by fastening a top portion of the hydraulic cylinder to the jack housing using a fastener inserted through a hole in a platform positioned within the jack housing, and further securing the hydraulic cylinder by fastening the ram piston to the jack leg using a bolt extending through a pre-existing hole in the jack leg.

A height adjustment device for adjusting a rotunda of a boarding bridge includes an external column fixed to the ground and having an inner space formed therein; an internal column which fixes a rotunda, and which is coupled so as to be slidable in the inner space such that rising and lowering is enabled; a driving unit which makes the internal column move vertically with respect to external column, and is disposed between the to the outside of the external column and the internal column; and a power unit for controlling the driving unit. The rotunda height adjustment device can be inspected, repaired for a defect thereof, and easily replaced.

A hydraulic jack having a piston, configured to lift at least a portion of a vehicle or trailer, and a housing, where the housing includes a high pressure fluid chamber configured to receive at least a portion of the piston, and where increasing fluid pressure within the high pressure chamber moves the piston further out of the housing. The hydraulic jack also includes a weight gauge attached to the housing and in fluid communication with the high pressure fluid chamber, wherein the weight gauge is configured and calibrated to measure and display the weight of the vehicle or trailer being lifted by the piston.

A hydraulic jack having a piston, configured to lift at least a portion of a vehicle or trailer, and a housing, where the housing includes a high pressure fluid chamber configured to receive at least a portion of the piston, and where increasing fluid pressure within the high pressure chamber moves the piston further out of the housing. The hydraulic jack also includes a weight gauge attached to the housing and in fluid communication with the high pressure fluid chamber, wherein the weight gauge is configured and calibrated to measure and display the weight of the vehicle or trailer being lifted by the piston.

A hydraulic jack having a piston, configured to lift at least a portion of a vehicle or trailer, and a housing, where the housing includes a high pressure fluid chamber configured to receive at least a portion of the piston, and where increasing fluid pressure within the high pressure chamber moves the piston further out of the housing. The hydraulic jack also includes a weight gauge attached to the housing and in fluid communication with the high pressure fluid chamber, wherein the weight gauge is configured and calibrated to measure and display the weight of the vehicle or trailer being lifted by the piston.

A hydraulic jack having a piston, configured to lift at least a portion of a vehicle or trailer, and a housing, where the housing includes a high pressure fluid chamber configured to receive at least a portion of the piston, and where increasing fluid pressure within the high pressure chamber moves the piston further out of the housing. The hydraulic jack also includes a weight gauge attached to the housing and in fluid communication with the high pressure fluid chamber, wherein the weight gauge is configured and calibrated to measure and display the weight of the vehicle or trailer being lifted by the piston.

A transportable jack system includes a jack disposed on a base. The base includes a base plate with a plurality of wheel openings formed therein, and a biasing member disposed between a wheel and the base plate. The biasing member is configured from a single piece of material consisting of a top horizontal portion, a bottom horizontal portion, and an angled middle portion disposed between the top horizontal portion and the bottom horizontal portion. The biasing member biases the base away from a ground surface when a load applied to the jack is below a predetermined threshold and deforms when the load is above the predetermined threshold, wherein the deformation allows the base plate to contact the ground surface.

According to the present invention, a height adjustment device for adjusting a rotunda of a boarding bridge is provided. The rotunda height adjustment device for a boarding bridge comprises: an external column fixed to the ground and having an inner space formed therein; an internal column which fixes a rotunda, and which is coupled so as to be slidable in the inner space such that rising and lowering is enabled; a driving unit which makes the internal column move vertically and translationally with respect to external column, and which is provided so as to be exposed to the outside of the external column and the internal column; and a power unit for controlling the driving unit. Therefore, the rotunda height adjustment device can be inspected, repaired for a defect thereof, and easily replaced.

The present invention relates to a hydraulic height adjusting device for installing a heavy-weight structure to secure stable horizontal bearing power against a horizontal load of a heavy-weight upper structure. The present invention includes a lower frame which is installed on a top surface of the carrier and is provided with a plurality of receiving portions formed in an upwardly opened shape; and a hydraulic cylinder which is disposed in and engaged to the respective receiving portions of the lower frame, the hydraulic cylinder being moved in a vertical direction to adjust the height of the upper structure, in a state in which an upper end thereof supports the upper structure. The receiving portion is provided with a support guide which is interposed between an inner wall of the receiving portion and the hydraulic cylinder to annually enclose the hydraulic cylinder and thus prevent the hydraulic cylinder from being tilted.

The present invention relates to a hydraulic height adjusting device for installing a heavy-weight structure to secure stable horizontal bearing power against a horizontal load of a heavy-weight upper structure. The present invention includes a lower frame which is installed on a top surface of the carrier and is provided with a plurality of receiving portions formed in an upwardly opened shape; and a hydraulic cylinder which is disposed in and engaged to the respective receiving portions of the lower frame, the hydraulic cylinder being moved in a vertical direction to adjust the height of the upper structure, in a state in which an upper end thereof supports the upper structure. The receiving portion is provided with a support guide which is interposed between an inner wall of the receiving portion and the hydraulic cylinder to annually enclose the hydraulic cylinder and thus prevent the hydraulic cylinder from being tilted.