Patent ID: 8387376

Claim:
A hydraulic system with an improved complex operation comprising: main hydraulic pumps and a pilot pump operated by an engine; a boom cylinder and an option device which are operated by the main hydraulic pumps; a main control valve including a boom spool and an option device spool which are shifted by a pilot signal pressure from the pilot pump to control hydraulic fluid supplied from the main hydraulic pumps to the boom cylinder and the option device, respectively; an operation lever which controls the boom spool by supplying the pilot signal pressure from the pilot pump to the boom spool through an output of an operation signal corresponding to an amount of operation by an operator; an option operation pedal which controls the option device spool by supplying the pilot signal pressure from the pilot pump to the option device spool through an output of an operation signal corresponding to the amount of operation by the operator; a confluence spool for controlling the option device, which performs the confluence of the hydraulic fluid from the main hydraulic pumps and supplies the confluence hydraulic fluid to the boom cylinder when the boom is operated to ascend by the operation of the operation lever, and which intercepts the confluence hydraulic fluid supplied to the boom cylinder and supplies the hydraulic fluid to the option device when a complex work for simultaneously operating the boom cylinder and the option device is performed; and a controller which outputs an electric control signal to a proportional control valve for the option device so as to delay pilot signal pressure supplied to the confluence spool for controlling the option device during start and end of the pilot signal pressure supply when a complex operation for simultaneously operating the boom cylinder and the option device is performed.