Method and device for controlling supply of working fluid

A method of controlling supply of working fluid in a construction machine having a plurality of hydraulic actuators that include at least actuators of a revolving system and actuators of a working equipment system, which method calls for:

• feeding working fluid from a pump to a plurality of pilot-operated throttling selector valves adapted to respectively control said plurality of hydraulic actuators in such a manner that the working fluid flows through said throttling selector valves in sequence;
• feeding working fluid from the pump to one of the throttling selector valves located relatively upstream and dedicated to the revolving system, without passing through any other throttling selector valves;
• feeding working fluid from the pump to another one of the throttling selector valves located relatively downstream and dedicated to the working equipment system, without passing through any other throttling selector valves in such a manner that the quantity of the working fluid fed to the throttling selector valve dedicated to the working equipment system is throttle-controlled according to the degree of operation of the throttling selector valve dedicated to the revolving system;
• reducing external pilot signal pressure applied to a priority valve which is located between the pump and the throttling selector valve dedicated to the working equipment system, according to increase in remote control pressure for pilot-operating the throttling selector valve dedicated to the revolving system when the remote control pressure is increased;
• and
• giving priority to the quantity of the hydraulic fluid fed from the pump to the throttling selector valve dedicated to the revolving system over the quantity of the hydraulic fluid fed from the pump to the throttling selector valve dedicated to the working equipment system, by controlling the priority valve according to the reduction of the external pilot signal pressure.

A fluid supply device, comprising:

• at least a first and a second valve respectfully controlling a fluid supply to a plurality of actuators of a type actuated by said fluid;
• a bypass line sequentially supplying said at least first and second valves with said fluid;
• a parallel line independently supplying said at least first and second valves with said fluid;
• a first supply line connecting said parallel line to said first valve;
• a second supply line connecting said bypass line to said parallel line between said first and second valves;
• a priority valve disposed in said second supply line being of a type adjustable to control said fluid to said first valve through said parallel line;
• and
• means for controlling said priority valve wherein said priority valve closes in accordance with a reduction of an external pilot signal pressure, wherein the quantity of said fluid fed to said first valve is given priority over the quantity of said fluid fed to said second valve.

A working fluid supply control device comprising:

• a pump adapted to discharge working fluid;
• a plurality of hydraulic actuators adapted to be operated by the working fluid;
• a plurality of throttling selector valves for respectively controlling the working fluid fed from the pump to said plurality of hydraulic actuators;
• a center bypass line for sequentially supplying said plurality of throttling selector valves with the working fluid discharged from the pump;
• a parallel line for independently supplying said plurality of throttling selector valves in sequence with the working fluid discharged from the pump;
• a supply line branching off from the center bypass line at a point between a first throttling selector valve, which is one of the aforementioned throttling selector valves, and a second throttling selector valve, which is a separate and different one of the throttling selector valves and located downstream from said first throttling selector valve, said supply line connected to a supply port of the second throttling selector valve;
• a separate and different supply line branching off from the parallel line and connected to the supply port of the second throttling selector valve;
• a priority valve disposed in said separate and different supply line and designed such that the degree of opening area of the priority valve is adjusted as to give priority to the quantity of the hydraulic fluid fed to the first throttling selector valve over the quantity of the hydraulic fluid fed to the second throttling selector valve;
• a control means adapted to steadily adjust the priority valve from the fully open state to the fully closed state in accordance with the degree of operation of the first throttling selector valve;
• the priority valve is a pilot operated throttle valve which is adapted to gradually open from the fully closed position in accordance with increase of external pilot signal pressure;
• and the control means is a pilot operated pressure reducing valve adapted to be controlled in such a manner that its outlet pressure, which serves as external pilot signal pressure applied to the priority valve, is reduced according to increase in remote control pressure for pilot operating the first throttling selector valve wherein the priority valve is spring biased to the closed position.