Open centre hydraulic distributor and power transmission system for transmitting to users of an operating machine

An open center hydraulic distributor of a fluid, comprising:

• a supply line for supplying said fluid that is receivable from a pump of the negative control type;
• a free circulation line that connects the supply line to at least one discharge;
• a delivery line that connects the supply line to one or more users downstream of the distributor;
• at least one directional valve so fitted as to intercept the free circulation line and the delivery line, said at least one directional valve comprising an actuator that is movable between at least a first and a second position and so configured that the movement from the first to the second position narrows a transit area of the free circulation line and opens a transit area of the delivery line;
• a slide valve arranged on the free circulation line downstream of said at least one directional valve, wherein said slide valve is configured to follow a linear opening/closing characteristic in an operating interval;
• a valve device configured to be activated when on the free circulation line a threshold value is reached that is given by the difference between a pressure value upstream and a pressure value downstream of said at least one directional valve, and to maintain said pressure difference equal to the threshold value;
• a negative control line to pick up a pressure signal from the free circulation line in a position downstream of said at least one directional valve and upstream of the slide valve, said negative control line being intended to bring a pressure signal to the pump to perform the control of negative type.