Vehicle with a boom comprising a hydraulic control circuit with a load control valve

1. A working vehicle comprising:

a lifting boom;

a fluid line to deliver hydraulic fluid to a tank when the boom lowers;

a control valve intercepting the fluid line;

a fluid piloting line connected to a user interface for piloting the control valve when the boom lowers; and

a pressure compensator piloted by a first pressure signal branched from the fluid line at the low pressure side of the control valve when lowering the lifting boom and by a second pressure signal from the fluid piloting line so that, upon increasing of the first pressure signal during boom lowering, a branch of the piloting line is progressively connected to the tank for causing the control valve to progressively close, the pressure of the branch being decoupled from the pressure of the second pressure signal.

2. The working vehicle according to claim 1 , wherein a flow restrictor is located along the piloting line to decouple the pressure of the branch and the pressure of the second pressure signal.

3. The working vehicle according to claim 1 , in which a feed branch bypasses the power control valve and joins the fluid line in a first node between an actuator to lift or lower the boom and the power control valve, and a check valve is along the feed branch to block flow from the actuator during boom lowering and to bypass power control valve during boom lifting.

4. The working vehicle according to claim 3 , wherein a further flow restrictor is along the fluid line and the first pressure signal is branched from the fluid line via a second node between the power control valve and the further flow restrictor, and a line pressure signal branches from the fluid line opposite to the second node with respect to the further flow restrictor and acts on the pressure compensator concordantly with the second pressure signal against the first pressure signal.

5. The working vehicle according to claim 4 , wherein the feed branch is connected to the fluid line opposite to the first node with respect to the further flow restrictor.

6. The working vehicle according to claim 1 , wherein the pressure compensator is normally closed by a spring acting against the first pressure signal.

7. The working vehicle according to claim 1 , further comprising a piloting valve for controlling downwards speed of the boom, the piloting valve comprising:

a first piloting duct for connection to cylinder line via the first node;

a piloting input opening to receive the second pressure signal; and

a second piloting duct to control the opening of the control valve and connected to the piloting input opening,

wherein the pressure compensator and the branch are attached between the second piloting duct and a discharge opening of the piloting valve,

wherein the piloting valve further comprises a piloting branch suitable for branching from the second piloting duct upstream of the branch, and

wherein the pressure compensator is connected to the first piloting duct and to the piloting branch such to progressively open and connect the branch to the discharge opening upon increasing of the first pressure signal.

8. The vehicle according to claim 1 , wherein the actuator is linear and a piston side of the actuator is connected to a piston line; a regeneration bridge connects a third node of piston line to the fluid line for flow regeneration; a further power control valve intercepts the regeneration bridge; the first pressure signal branches from the regeneration bridge; and opening of the further control valve is piloted by a regeneration piloting pressure signal branched from the second pressure signal.

9. A method of providing a working vehicle having a hydraulic lifting boom with a circuit to control downwards speed of the boom, the circuit comprising:

a fluid line to deliver hydraulic fluid to a tank when the boom lowers;

a control valve intercepting the fluid line; and

a fluid piloting line connected to a user interface for piloting the control valve when the boom lowers;

the method comprising the steps of:

providing a pressure compensator to discharge the fluid piloting line via a branch; and

connecting the compensator:

a first pressure signal branched from the fluid line at the low pressure side of the control valve when lowering the lifting boom; and

a second pressure signal from the fluid piloting line;

so that the pressure compensator is piloted by the first pressure signal and by the second pressure signal so that, upon increasing of the first pressure signal during boom lowering, the branch is progressively connected to the tank for causing the control valve to progressively close, the pressure of the branch being decoupled from the pressure of the second pressure signal.