Patent attributes
The load dependent, variable displacement, at least three-shift hydraulic mechanism includes a hydraulic device disposed at the front side of a valve block and adapted to move a ram piston oriented such as to raise weight, the hydraulic device defining an oil accumulation chamber, a rapid-lifting oil chamber for rapid extension of the ram piston under no-load conditions, and a high-pressure oil chamber for lifting the ram piston oriented to raise weights, a pump piston apparatus disposed at the back side of the valve block and defining a front working chamber and a rear oil accumulation chamber, and oil passages so arranged that hydraulic oil can be supplied from the oil accumulation chamber and the rear oil accumulation chamber to the front working chamber and then to the rapid-lifting oil chamber or the high-pressure oil chamber to extend the ram piston.
