Patent ID: 6378302
Filing Date: 2002-04-30
Classification: E02F,F15B

Abstract:
A hydraulic circuit system comprising a hydraulic pump (1), a plurality of hydraulic actuators (3-1, 3-2) driven by a hydraulic fluid delivered from said hydraulic pump, a plurality of control valves (4-1, 4-2) disposed between said hydraulic pump and said plurality of actuators, a signal transmitting hydraulic line (9) to which a signal pressure based on a maximum load pressure among said plurality of hydraulic actuators is introduced, and pump control means (2) for controlling a delivery pressure of said hydraulic pump to be held higher than said signal pressure by a predetermined value,said plurality of control valves comprising respectively main valves (4a-1, 4a-2) including meter-in variable throttles (M/I) for controlling flow rates of the hydraulic fluid supplied to said hydraulic actuators, and flow distribution valves (5-1, 5-2) disposed between a third hydraulic line (35) connected to the outlet side (5b) of said flow distribution valve in a second particular control valve (4-2) of said plurality of control valves, said selector valve (11) having a first position (I) at which a portion of said second hydraulic line (31-1) on the side of said control chamber is connected to only said signal transmitting hydraulic line (9), and a second position (II) at which the portion of said second hydraulic line (31-1) on the side of said control chamber is connected to both said signal transmitting hydraulic line (9) and said third hydraulic line (35).