A device for delivering fluid, comprising an elongated outer casing (10) provided with a substantially cylindrical inner chamber (11) a plunger (21) movable axially along a longitudinal axis A-A of an inner reservoir (22) towards an outlet (28) an actuator comprising a multi-stage lead-screw with a plurality of coaxial, screwably-interconnected bushings and an output spindle or an output bushing linked to the movable plunger (21), whereby a rotation of the rotating element causes a translation of the bushings relative to each other in telescopic fashion, and a translation of the movable plunger in the cartridge.
