The device comprises a stationary body which has, defined inside it, a passage for a flow of liquid with at least one inlet opening and one outlet opening for the flow and in which at least one valve seat directed towards the outlet opening is defined in the vicinity of the inlet opening and in a middle portion of which a shaped transverse annular surface is formed. A movable body is arranged in the passage and co-operates in the manner of a flow throttling member with the transverse annular surface so as to define for the liquid flowing from the inlet opening to the outlet opening a flow cross section variable depending on the pressure of the liquid at the inlet of the support body. The movable body co-operates moreover in the manner of a obturator with the seat and a return spring tends to push it against this seat away from said shaped annular surface.