Hydraulic propulsion system for double traction vehicles

Hydraulic propulsion system for four-wheel-drive vehicles, formed by a main engine or motor (1) powered by combustion, electricity or by any other means, to drive two transmission systems associated with the propulsion means or front and rear wheels (11) of the vehicle;

• it is characterised in that the output power shaft (4) of the main motor (1) is connected to a hydraulic variable-displacement piston pump (5), associated with a hydraulic circuit (6) including an oil filter (27), a pressure control gauge (20), a hydraulic liquid tank (7) and a vacuum valve (26) and pressure control gauge (21) in the tank;
• this circuit (6) has the means for selectively recirculating the fluid driven by the hydraulic pump (5) to a pair of hydraulic variable-displacement piston motors (8) associated with the corresponding differentials (9) of rear and front traction means associated with the wheels (11) of the vehicle, respectively, having arranged for the hydraulic circuit (6) to include valves and solenoid valves (16), (17A), (17B), (18), (19), (29), (29A), (30) and (30A) for the controlled recirculation of the hydraulic fluid driven by the hydraulic pump (5) to either hydraulic motor (8), both hydraulic motors or neither of them, such that it is possible to drive either propulsion system, both propulsion systems simultaneously or neither of them, with the special feature that the circuit (6) has a key (25) to change the forward/reverse circulation direction.