Patent ID: 8001882

Claim:
A double check valve having a floating function, comprising: a hydraulic pump; a hydraulic cylinder connected to the hydraulic pump to operate a working device; a control valve installed in flow paths between the hydraulic pump and the hydraulic cylinder, and shifted to control a start, a stop, and a direction change of the hydraulic cylinder; and a double check valve installed in flow paths between the control valve and the hydraulic cylinder, and including a pair of plungers dividedly formed to be shifted in directions opposite to each other when a signal pressure is applied from an outside to a signal pressure flow path, and having first diaphragms formed thereon to receive an operating pressure being applied to the hydraulic cylinder and second diaphragms formed thereon to receive a signal pressure being applied to the signal pressure flow path in order to perform a floating function of the working device, sectional areas of the first diaphragms and the second diaphragms being different from each other, and a pair of check valves being pressed to remove their check function through shifting of the plungers; wherein, if the signal pressure is applied from the outside to the signal pressure flow path and the operating pressure in the hydraulic cylinder is lower than a predetermined pressure, the check function of the check valves is removed, while if the signal pressure is applied from the outside to the signal pressure flow path and the operating pressure in the hydraulic cylinder is higher than the predetermined pressure, the check function of the check valves is maintained.