CONSTRUCTION MACHINE DUAL-DUMP HYDRAULIC CIRCUIT WITH PILOTED ARM-BOOM CYLINDER SUPPLY PRIORITY SWITCHING VALVES

摘要

A hydraulic circuit for a construction machine for operating an actuator for a working machine (107) simultaneously with an actuator for a working element (107). The hydraulic circuit comprises a first hydraulic pump (50), a first directional control valve (1, 100) connected to the first hydraulic pump (50) and controlling an operation of the working machine actuator (107), a third directional control valve (306) controlling an operation of the working element actuator (302), a second directional control valve (2) connected to a second hydraulic pump (52), a first pilot operating device (111, 201) for controlling an operation of the first directional control valve (1, 100) and a second pilot operating device (304, 303) for controlling an operation of the third directional control valve (306). The hydraulic circuit further comprises a first hydraulic fluid joining device (323; 324, 325) for providing hydraulic fluid of the second hydraulic pump(52)to the input side of third directional control valve (306), a second hydraulic fluid joining device (10, 40, 41, 43) for supplying the hydraulic fluid of the second hydraulic pump (52) to the input side of the first directional control valve (1, 100), and a priority switching device (320, 328; 326, 329) for preventing, in response to a signal of the first pilot operating device (111, 201), the signal of the second pilot operating device (304, 303) from being applied to the second directional control valve (2).