Patent ID: 6799424
Filing Date: 2004-10-05
Classification: E02F

Abstract:
A hydraulic circuit for driving actuators by pressure oil supplied from a first pump, a second pump and a third pump and returned to a tank, the hydraulic circuit comprising:a first circuit including a directional control valve supplied with the pressure oil from said first pump, the directional control valve in said first circuit controlling connection between said first pump or said tank and at least one of said actuators and a flow rate of the pressure oil therebetween; a second circuit including a directional control valve supplied with the pressure oil from said second pump, the directional control valve in said second circuit controlling connection between said second pump or said tank and at least one of said actuators and a flow rate of the pressure oil therebetween; a third circuit including a directional control valve supplied with the pressure oil from said third pump, the directional control valve in said third circuit controlling connection between said third pump or said tank and at least one of said actuators and a flow rate of the pressure oil therebetween; a first merging line disposed to be capable of supplying the pressure oil sent from said third pump under a pressurized state to the directional control valve in said first circuit; a second merging line disposed to be capable of supplying the pressure oil sent from said third pump under a pressurized state to the directional control valve in said second circuit; and a merging valve for selectively communicating or cutting off said first merging line and said second merging line with or from said third pump, said merging valve having a first shift position at which said third pump is connected to said second merging line, and a second shift position at which said third pump is connected to said first merging line and said second merging line, said merging valve being continuously shifted between said first shift position and the second shift position depending on a state of said first circuit or said second circuit.