Three-shift lifting mechanism for jack or the like

Details Three-shift lifting mechanism for jack or the like Three-shift lifting mechanism for jack or the like

2005-06-08

2008-09-09

Lazo, Thomas E (Department: 3745)

Power plants

Pressure fluid source and motor

Ram driven by fluid pumped from reservoir

C254S00800R, C254S0930VA, C254S0930HP

Reexamination Certificate

active

07421841

ABSTRACT:
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.

REFERENCES:
patent: 3806091 (1974-04-01), Wride
patent: 6035635 (2000-03-01), Hung
patent: 6581909 (2003-06-01), Wixey
patent: 6923431 (2005-08-01), Yueh

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