Patent ID: 7434394
Filing Date: 2008-10-14
Classification: E02F

Abstract:
1. A hydraulic drive system provided with: a main hydraulic pump, a first hydraulic cylinder and second hydraulic cylinder driven by pressure oil delivered from said main hydraulic pump, a first directional control valve for controlling a flow of pressure oil to be fed from said main hydraulic pump to said first hydraulic cylinder, a second directional control valve for controlling a flow of pressure oil to be fed from said main hydraulic pump to said second hydraulic cylinder, a first control device for selectively controlling said first directional control valve, and a second control device for selectively controlling said second directional control valve, wherein: said hydraulic drive system is provided with a pressure oil feed means for feeding hold-side pressure oil in said first hydraulic cylinder to an upstream side of said second directional control valve when a drive-side pressure of said second hydraulic cylinder has increased to a high pressure equal to or higher than a predetermined pressure.