Filler spout with leak limitation

A filler spout comprising a tubular body having mounted therein a valve member extending facing a first seat and a secondary shutter arranged in a distribution chamber downstream from the valve member and rigidly connected thereto with a small amount of axial clearance between the valve member and the secondary shutter, and a movable portion of an actuator being coupled to the valve member in order to move the valve member between a transient closure position in which the valve member is in contact with the first seat and the secondary shutter is in contact with a second seat and an extreme opening position in which the valve member is lifted from the first seat and the secondary shutter is lifted from the second seat, wherein the valve member possesses a final closure position between the transient closure position and the opening position and in which the valve member is in contact with the first seat and the secondary shutter is in contact with the second seat, wherein the valve member comprises a portion that is received in a bore opening out into the distribution chamber when the valve member is in either the transient closure position or the final closure position and the valve member has an annular lip having a diameter close to a diameter of the bore in order to create a drop in pressure in said distribution chamber when the valve member is moved from the transient closure position to the final closure position, and wherein the actuator is connected to a metering unit arranged to determine a quantity of liquid delivered by the spout and to control the actuator in order to stop the liquid delivery as a function of the determined quantity by moving the valve member from the opening position to the transient position and therefrom to the final closure position.