Turbofan comprising a series of rotatable blades for blocking off the bypass flow duct

1. A turbofan having a longitudinal axis and comprising an engine and a nacelle surrounding the engine which comprises a fan casing, where a duct of a bypass flow is delimited between the nacelle and the engine and in which an air flow circulates in a flow direction, said nacelle comprising:

a fixed structure fastened to the fan casing,

a movable assembly having a movable cowl and a slide, the movable cowl being fastened to the slide downstream thereof with respect to the flow direction, the slide being translationally movable on the fixed structure in a direction of translation between an advanced position in which the slide is positioned in such a way that the movable cowl is moved towards the fan casing and a retreated position in which the slide is positioned in such a way that the movable cowl is moved away from the fan casing in order to define between them a window open between the duct and the outside of the nacelle,

a plurality of blades, each blade comprising a first end mounted rotatably on the slide about an axis of rotation globally parallel to the longitudinal axis, where each blade is movable between a retracted position in which the blade is outside of the duct and a deployed position in which the blade is across the duct,

a set of actuators for moving the slide between the advanced position and the retreated position, and vice versa, and

an operating system configured to move each blade from the retracted position to the deployed position, and vice versa,

wherein the plurality of blades are arranged in a plurality of stages along the flow direction, the plurality of stages comprising a first stage, which is furthest downstream with respect to the flow direction, where the blades of the first stage are positioned in one and the same plane perpendicular to the longitudinal axis, each one blade of the first stage following a next other blade of the first stage over a periphery of the slide, and

wherein, for each one of the other stages than the first stage, the blades of each of the stage are positioned in a common plane different from the planes of other stages and perpendicular to the longitudinal axis and the blades are angularly offset about the longitudinal axis with respect to the blades of a stage which is arranged downstream with respect to the flow direction.

2. The turbofan according to claim 1 , wherein the nacelle comprises a cage having an outer wall concentric with the longitudinal axis and constituting the wall oriented towards the outside of the nacelle, wherein, for each stage of blades, the cage has a slot arranged between an upstream wall and a downstream wall, wherein, when they are in the retracted position, the blades of a same stage are housed in the slot associated with the stage, and wherein, for each blade, a shaft secured to the blade is mounted rotatably at the first end between the upstream wall and the downstream wall of the stage corresponding to the blade and forms the axis of rotation of the blade.

3. The turbofan according to claim 2 , wherein, for each blade of a stage, the outer wall has a window, wherein the operating system comprises, for each blade of a stage, a pinion secured to the blade and concentric to the axis of rotation of the blade and of which the teeth protrude from the outer wall through the window, a rack mounted movably against the outer wall and having its teeth towards the outer wall in order to engage with the teeth of the pinions, and a motor configured to move the rack along the outer wall.

4. The turbofan according to claim 1 , wherein the nacelle comprises a cage having an outer wall concentric with the longitudinal axis and constituting the wall oriented towards the outside of the nacelle, wherein, for each stage of blades, the cage has a slot arranged between an upstream wall and a downstream wall, wherein, when they are in the retracted position, the blades of a same stage are housed in the slot associated with the stage, wherein, for each blade of the same stage, a shaft is mounted fixedly between the upstream wall and the downstream wall of the stage corresponding to the blade, and wherein the blade is mounted rotatably about the shaft by a close fit at the first end.

5. An aircraft comprising at least one turbofan according to claim 1 .