Patent ID: 8702061
Filing Date: 2014-04-22
Classification: E02F,F15B

Abstract:
1. A hydraulic circuit for a counterweight attaching/detaching device, comprising: a work machine body at which a hydraulic source is disposed, a counterweight detachably mounted at said work machine body, an up/down hydraulic cylinder attached to said work machine body, which raises/lowers said counterweight so as to attach/detach said counterweight to/from said work machine body by delivering/discharging a hydraulic fluid, originating from said hydraulic source, to/from a bottom chamber and a rod chamber; and a control valve disposed between said hydraulic source and said up/down hydraulic cylinder, further comprising: a first cutoff valve configured with a sequence valve to which a hydraulic pressure in said rod chamber is applied as an external pilot pressure, disposed in a first main duct located between said control valve and said bottom chamber of said up/down hydraulic cylinder, along such a direction as to control outflow of hydraulic fluid from said bottom chamber, and a check valve connected in parallel to said sequence valve; and a second cutoff valve configured with a sequence valve that achieves continuity with the hydraulic pressure in said rod chamber applied thereto as an internal pilot pressure higher than said external pilot pressure at which said sequence valve in said first cutoff valve achieves continuity, disposed in a second main duct, located between said control valve and said rod chamber of said up/down hydraulic cylinder, along such a direction as to control outflow of hydraulic fluid from said rod chamber, and a check valve connected in parallel to said sequence valve.