Patent ID: 9068322
Filing Date: 2015-06-30
Classification: E02F,F15B

Abstract:
1. A double check valve for a construction machine comprising: a hydraulic pump; a hydraulic cylinder connected to the hydraulic pump to drive a working device; a control valve installed in a flow path between the hydraulic pump and the hydraulic cylinder and shifted to control a start, a stop, and a direction change of the hydraulic cylinder; a pair of pistons installed on one side of a piston cylinder to open and close first flow paths and second flow paths provided between the control valve and the hydraulic cylinder, provided with plunger ground portions and notch portions, respectively, and dividedly formed to be shifted in opposite directions to each other when signal pressure that is introduced from any one of the first and second flow paths acts on check hydraulic pressure portions during temporary descending of the working device; a pair of check valves of which checking functions are released when the check valves are pressed through the shifting of the pistons; and a plunger installed inside the piston cylinder to move the pistons in a checking function release direction of the check valves while a flow rate of hydraulic fluid, having passed through the notch portions, forms pressure in the plunger ground portions of the pistons.