An adaptor is provided for a jack assembly having a lifting jack carrying a horizontal plate for raising and lowering a heavy component supported by the jack assembly. The adaptor includes a horizontal support plate fastened to and vertically offset from the horizontal plate of the jack assembly by a height. A plurality of elongated arms is slidably mounted between the two plates to move in a generally horizontal plane. Each of arms includes a holding assembly configured to engage portions of the component supported on the support plate to stabilize the component as it is raised and lowered by the jack assembly. The arms are supported in the height between the two plates at different heights so that the arms are capable of a wide range of rotational and linear movements to adjust the position of the holding assembly of each arm relative to the heavy component.

An adaptor is provided for a jack assembly having a lifting jack carrying a horizontal plate for raising and lowering a heavy component supported by the jack assembly. The adaptor includes a horizontal support plate fastened to and vertically offset from the horizontal plate of the jack assembly by a height. A plurality of elongated arms is slidably mounted between the two plates to move in a generally horizontal plane. Each of arms includes a holding assembly configured to engage portions of the component supported on the support plate to stabilize the component as it is raised and lowered by the jack assembly. The arms are supported in the height between the two plates at different heights so that the arms are capable of a wide range of rotational and linear movements to adjust the position of the holding assembly of each arm relative to the heavy component.

A machine leveling pedestal incorporating a cylinder and piston defining an interior space, having a helically threaded outer surface, and having an upwardly facing land; a hydraulic fluid port opening the interior expansion space; a nut having a downwardly facing land and gear teeth, the nut being threadedly mounted over the helically threaded outer surface; a drive gear connected to the cylinder and piston for vertically slidably engaging the drive gear with the gear teeth, and, upon alternate rotations of the drive gear, rotating the nut about the cylinder and piston so that the nut vertically moves between a mechanical support position and a hydraulic support position, the upwardly and downwardly facing lands contacting each other upon movement to the mechanical support position, and the downwardly facing land displacing upwardly upon movement toward the hydraulic support position; and a motor connected to the drive gear.

A hydraulic oil-circuit system and a hydraulic jack are proposed. The hydraulic oil-circuit system includes a hydraulic cylinder, an oil loading chamber, a storage oil chamber and an oil unloading pipeline; a piston is arranged in the hydraulic cylinder and divides 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, and the second hydraulic oil chamber has a second oil port; the first oil port and the second oil port are both in unidirectional communication with the oil loading chamber and are both in unidirectional communication with the storage oil chamber; and the oil unloading pipeline connects the oil loading chamber and the storage oil chamber.

A hydraulic oil-circuit system and a hydraulic jack are proposed. The hydraulic oil-circuit system includes a hydraulic cylinder, an oil loading chamber, a storage oil chamber and an oil unloading pipeline; a piston is arranged in the hydraulic cylinder and divides 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, and the second hydraulic oil chamber has a second oil port; the first oil port and the second oil port are both in unidirectional communication with the oil loading chamber and are both in unidirectional communication with the storage oil chamber; and the oil unloading pipeline connects the oil loading chamber and the storage oil chamber.

Provided is a jack device easily storable in a storage space of a machine body of a work machine. The jack device includes an arm, a cylinder, a float and a pin. The arm is rotatably connected to the machine body. The cylinder is connected to the arm rotatably about a cylinder rotary axis so as to have an upright posture and a tilt posture. The pin rotatably connects the float to a rod of the cylinder. The jack device is stored in a state where the cylinder is contracted and in the tilt posture and the bottom surface of the float lies along a facing part of the machine body that faces the storage space.

Provided is a jack device easily storable in a storage space of a machine body of a work machine. The jack device includes an arm, a cylinder, a float and a pin. The arm is rotatably connected to the machine body. The cylinder is connected to the arm rotatably about a cylinder rotary axis so as to have an upright posture and a tilt posture. The pin rotatably connects the float to a rod of the cylinder. The jack device is stored in a state where the cylinder is contracted and in the tilt posture and the bottom surface of the float lies along a facing part of the machine body that faces the storage space.