TURBOFAN ENGINE WITH A SECONDARY FLOW DUCT SEALING SYSTEM WITH SAILS

Description

TECHNICAL FIELD

[0001] The present invention relates to a dual-flow turbojet engine which comprises flexible sails and, for each sail, a rotating arm for moving the sail across the secondary flow stream, as well as an aircraft comprising at least one such dual-flow turbojet engine. STATE OF THE PRIOR ART

[0002] An aircraft has a fuselage with a wing attached to each side. At least one turbofan engine is suspended beneath each wing. Each turbofan engine is attached beneath the wing by means of a strut that is fixed between the wing structure and the turbofan engine structure.

[0003] The turbofan engine consists of an engine and a nacelle that is attached around the engine. The turbofan engine has a secondary flow stream between the nacelle and the engine, in which a secondary flow circulates.

[0004] The nacelle comprises a plurality of reversing doors, each of which is rotatable on the nacelle structure between a retracted position in which it is outside the secondary flow path and a deployed position in which it is positioned across the secondary flow path in order to divert the secondary flow towards a window which is in the wall of the nacelle and which is open between the secondary flow path and the exterior of the nacelle.

[0005] Thus, the secondary flow is deflected outwards and more precisely towards the front of the turbojet in order to produce counter-thrust.

[0006] Although reversing doors are completely satisfactory, it is desirable to find different mechanisms, especially less heavy ones.

[0007] Document US-A-2021 / 207557 discloses a dual-flow turbojet engine according to the preamble of claim 1. STATEMENT OF THE INVENTION

[0008] An object of the present invention is to provide a dual-flow turbojet engine which comprises flexible sails and, for each sail, a rotating arm for moving the sail across the secondary flow stream.

[0009] For this purpose, a dual-flow turbojet engine is proposed having a longitudinal direction and comprising an engine and a nacelle surrounding the engine which comprises a fan casing, where a vein of a secondary 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 fixed to the fan casing and comprising a cascade support carrying cascades, a movable cowl which is movable in translation on the fixed structure in a translation direction between an advanced position in which the movable cowl is positioned so that it is close to the fan casing and a retracted position in which the movable cowl is positioned so that it is distant from the fan casing to define between them an open window between the vein and the exterior of the nacelle and facing the cascades, a plurality of transmission systems, where each has at least one arm with a distal end and a proximal end mounted movable in rotation on the transmission system about an axis of rotation generally parallel to the longitudinal direction,where said arm is movable between a retracted position in which it is outside the vein and a deployed position in which it is across the vein, where each transmission system is movable in translation between an advanced position corresponding to the advanced position of the movable cover and a retracted position corresponding to the retracted position of the movable cover, for each arm, a flexible web comprising a first edge integral with said arm, a second edge one end of which is fixed to a neighboring transmission system and a third edge, where the web is movable alternately between a folded position, corresponding to the retracted position of the arm, where the third edge is distant from the engine and an unfolded position, corresponding to the deployed position of the arm, in which the third edge is closer to the engine, and for each transmission system,an actuator arranged to ensure the movements of the movable hood and said transmission system simultaneously between their advanced position and their retracted position, and vice versa, and where the transmission system is arranged to ensure the movement of each arm from its retracted position to its deployed position during the movement of the transmission system from its advanced position to its retracted position and vice versa,

[0010] The dual-flow turbojet being characterized in that the actuator comprises: a fixed shaft fixed to the fixed structure and which has a longitudinal axis parallel to the longitudinal direction, a shaft mounted to rotate inside the fixed shaft around the longitudinal axis and driven in rotation by a motor, a movable shaft mounted inside the fixed shaft and a proximal end of which is mounted outside the shaft, where the movable shaft has with the fixed shaft, a helical connection with a first screw thread around the longitudinal axis and where the movable shaft has with the shaft, a sliding connection along the longitudinal axis, where the transmission system is integral with the movable shaft, and where at a distal end, the movable shaft has a threaded bore coaxial with the longitudinal axis, and a threaded rod of which a proximal end is screwed inside the threaded bore with a second screw thread, and a distal end of which has with the movable cover, a recessed connection.

[0011] Replacing the reversing doors and their drive mechanisms with the flexible web and the set of rotating movable arms allows for a reduction in mass.

[0012] Advantageously, a transmission system carries a pair of arms.

[0013] Advantageously, the second screw pitch is greater than the first screw pitch.

[0014] According to a particular embodiment, the transmission system comprises: a main gear fixed coaxially on the movable shaft, on either side of the main gear, a spacer which is tapped and screwed onto the thread of the movable shaft and resting against a face of the main gear, for each spacer, a first ball bearing in which said spacer is embedded, a base comprising on either side of the main gear, a flank, where the two flanks are integral with each other, where each flank is crossed by a hole in which a first ball bearing is embedded, where the base has locking means which ensure its locking in rotation relative to the longitudinal axis, and for each arm, a secondary gear integral with said arm and mounted mobile in rotation on the base around an axis parallel to the longitudinal axis and driven by the main gear.

[0015] According to a particular embodiment, the transmission system comprises: a main gear fixed coaxially on the movable shaft, on either side of the main gear, a smooth spacer mounted sliding on the thread of the movable shaft and bearing against a face of the main gear, for each spacer, a first ball bearing in which said spacer is embedded, a base comprising on either side of the main gear, a flank, where the two flanks are integral with each other, where each flank is crossed by a hole in which a first ball bearing is embedded, where the base has locking means which ensure its locking in rotation relative to the longitudinal axis, and for each arm, a secondary gear integral with said arm and mounted mobile in rotation on the base around an axis parallel to the longitudinal axis and driven by the main gear.

[0016] The invention also proposes an aircraft comprising at least one dual-flow turbojet according to one of the preceding variants. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The above-mentioned and other features of the invention will become more clearly apparent from the following description of an exemplary embodiment, said description being made in relation to the accompanying drawings, among which: Fig. 1 is a side view of an aircraft comprising a dual-flow turbojet engine according to the invention, Fig. 2 is a perspective view of the dual-flow turbojet according to the invention in the retracted and deployed position, Fig. 3 is a schematic representation of a dual-flow turbojet according to the invention seen in section through a vertical plane, Fig. 4 is a front view of a pair of sails in the folded position, Fig. 5 is a front view of the pair of sails of the Fig. 4 in unfolded position, Fig. 6 is a sectional view of an actuator according to a particular embodiment of the invention, and Fig. 7 is a perspective view of a transmission system implemented between an actuator and a pair of sails. DETAILED PRESENTATION OF IMPLEMENTATION METHODS

[0018] In the following description, terms relating to a position are taken with reference to the direction of forward movement of an aircraft as shown in the Fig. 1 by arrow F.

[0019] There Fig. 1 shows an aircraft 10 which comprises a fuselage 12 on each side of which is fixed a wing 14 which carries at least one dual-flow turbojet engine 100 according to the invention. The dual-flow turbojet engine 100 is fixed under the wing 14 by means of a mast 16.

[0020] There Fig. 2 and the Fig. 3 show the dual-flow turbojet engine 100 which has a nacelle 102 and an engine 20 which is housed inside the nacelle 102. The dual-flow turbojet engine 100 also has a fan casing 202. On the Fig. 2 , the 20 engine is represented by a cylinder in mixed lines.

[0021] In the following description, and by convention, X is the longitudinal direction of the dual-flow turbojet 100 which is parallel to the longitudinal axis of the aircraft 10 oriented positively towards the front of the aircraft 10, Y is the transverse direction which is horizontal when the aircraft is on the ground, and Z is the vertical direction, these three directions X, Y and Z being orthogonal to each other.

[0022] There Fig. 2 shows the 100 turbofan engine and the Fig. 3 shows a schematic cross-sectional representation of the 100 turbofan engine.

[0023] The dual-flow turbojet 100 has, between the nacelle 102 and the engine 20, a vein 204 in which circulates a secondary flow 208 coming from the air intake through a fan 300 and which therefore flows in the direction of flow which goes from front to rear.

[0024] The nacelle 102 has a fixed structure 206 which is fixedly mounted on the fan casing 202. The fixed structure 206 is composed in particular here of a front frame 210 mounted around the fan casing 202 and of exterior panels 212 fixed to the front frame 210 and forming an exterior aerodynamic surface.

[0025] The nacelle 102 has a mobile assembly 214 which has a mobile cover 216 which forms the outer walls of the nozzle.

[0026] The fixed structure 206 also has a cascade support 218 which takes the form of a cylinder with openwork walls between which cascades 221 are arranged. Here, the cascade support 218 is fixed to the front frame 210.

[0027] In the embodiment of the invention shown in the Figs. 2 And 3 , the movable hood 216 has a housing 217 which is cylindrical and in which the cascade support 218 is placed.

[0028] The movable hood 216 is mounted to move in translation in a translation direction generally parallel to the longitudinal direction X on the fixed structure 206 of the nacelle 102.

[0029] The movable hood 216 is movable between an advanced position ( Fig. 3 ) and a backward position ( Fig. 2 ) and vice versa. In the forward position, the movable cowl 216 is positioned as far forward as possible relative to the direction of flow so that the movable cowl 216 is brought closer to the outer panels 212 and the fan casing 202 and thus forms a continuous aerodynamic surface. In the retracted position, the movable cowl 216 is positioned as far back as possible relative to the direction of flow so that the movable cowl 216 is moved away from the outer panels 212 and the fan casing 202 so as to define between them a window 220 which is opposite the cascades 221 and opens between the vein 204 and the outside.

[0030] In the forward position, the movable cowl 216 and the outer panels 212 extend so as to define the outer surface of the nacelle 102, and the movable cowl 216 and the fan casing 202 extend so as to define the outer surface of the vein 204. In the forward position, the movable cowl 216 is positioned opposite the cascades 221 and prevents the passage of the air flow.

[0031] In the retracted position, the movable cowl 216 and the fan casing 202 as well as the external panels 212 are at a distance and define between them the window 220 open between the vein 204 and the exterior of the nacelle 102. That is to say that the air of the secondary flow 208 passes through the window 220 to reach the exterior of the dual-flow turbojet 100 by passing through the cascades 221.

[0032] On the Fig. 2 , the movable hood 216 and the cascade support 218 are made in two parts symmetrical with respect to a vertical plane XZ. These two parts are mounted on beams of the fixed structure 206, in particular here, a 12 o'clock beam and a 6 o'clock beam which fill the spaces between the two parts constituting the movable hood 216 and the cascade support 218. Of course, the number of parts constituting the movable hood 216 and the cascade support 218 may be different.

[0033] The translational guidance of the movable hood 216 is carried out by any appropriate means, such as, for example, slide systems between the beams of the fixed structure 206 and the movable hood 216.

[0034] The cascade support 218 is fixed to the front frame 210 and more generally to the fixed structure 206 and in the forward position, the cascade support 218 is located inside the movable cowl 218, here inside the housing 217 and in the rearward position, the cascade support 218 is located between the movable cowl 216 and the fan casing 202 as well as the exterior panels 212 to be at the level of the window 220.

[0035] The nacelle 102 also comprises a plurality of transmission systems 223, where each has at least one arm 250 with a distal end and a proximal end mounted to rotate on the transmission system 223 around an axis of rotation generally parallel to the longitudinal direction X.

[0036] Each arm 250 is thus movable between a retracted position in which it is outside the vein 204 and is pressed against the outer edges of the vein 204 and a deployed position ( Fig. 2 ) in which it is across the vein 204. Overall, each arm 250 extends in a plane perpendicular to the longitudinal direction X.

[0037] Furthermore, each transmission system 223 is movable in translation between an advanced position corresponding to the advanced position of the movable hood 216 and a retracted position corresponding to the retracted position of the movable hood 216.

[0038] For each arm 250, the nacelle 102 comprises a flexible web 252 comprising a first edge 252a secured to said arm 250, a second edge 252b one end of which is fixed to a neighboring transmission system 223 and a third edge 252c which is here arched. There is thus a plurality of flexible webs 252 seen in transparency (dot-and-dash lines) on the left on the Fig. 2 which is distributed angularly around the engine 20 on the outer edge of the vein 204, that is to say along the movable cowl 216. The number of arms 250 and the number of sails 252 depend on the dimensions of the double-flow turbojet 100 and the dimensions of the sails 252.

[0039] In the rearward position, each sail 252 is located aft of the window 220.

[0040] More specifically, in the embodiment of the invention presented here, each edge 252a-c extends between a first end and a second end. The second end of the first edge 252a joins the second end of the second edge 252b.

[0041] The second edge 252b is positioned along the outer edge of the vein 204 and it is fixed and its fixing is carried out here by a fixed point 253 at its first end which is fixed on the neighboring transmission system 223.

[0042] In the embodiment of the invention presented here, the first edge 252a and the second edge 252b extend generally along radii around the axis of rotation of the arm 250.

[0043] The first end of the third edge 252c joins the first end of the first edge 252a and the second end of the third edge 252c joins the first end of the second edge 252b. In the embodiment of the invention presented here, the third edge 252c is arcuate.

[0044] Each sail 252 here generally takes the form of a quarter of a circle and it is mobile alternately between a folded position ( Fig. 4 ), corresponding to the retracted position of the arm 250, where the third edge 252c is moved away from the motor 20 and brought closer to the outer edge of the vein 204 to leave the vein 204 free and an unfolded position ( Fig. 5 ), corresponding to the deployed position of the arm 250, in which the third edge 252c is brought closer to the motor 20 to close the vein 204 and direct the secondary flow 208 towards the window 220 then the outside through the cascades 221. Thus, in the folded position, the veil 252 is not across the vein 204 and in the unfolded position it is across the vein 204.

[0045] For each transmission system 223, the nacelle 102 comprises an actuator 219 which is arranged to ensure the movements of the movable cowl 216 and said transmission system 223 simultaneously between their advanced position and their retracted position, and vice versa. The transmission system 223 is also arranged to ensure the movement of each arm 250 which it carries from its retracted position to its deployed position during the movement of the transmission system 223 from its advanced position to its retracted position and vice versa, and therefore at the same time, the sail 252 attached to the arm 250 passes from its folded position to its unfolded position and vice versa.

[0046] Each actuator 219 is controlled by a control unit, for example of the processor type, which controls the movements in one direction or the other according to the needs of the aircraft 10.

[0047] An actuator 219 according to a particular embodiment is shown in Fig. 6 and is explained below.

[0048] The fan casing 202 and the outer panels 212 define the window 220 upstream relative to the flow direction and the movable cowl 216 defines the window 220 downstream relative to the flow direction.

[0049] To save weight, there is here a transmission system 223 for a pair of arms 250 and therefore a pair of sails 252 angularly adjacent.

[0050] In the embodiment of the invention presented in the Fig. 2 , there is a transmission system 223 for a single sail 252 at the ends, here at 12 o'clock and at 6 o'clock. For two consecutive sails 252, there is a transmission system 223, one embodiment of which is shown in Fig. 7 and described below.

[0051] The 252 sails overlap in the unfolded position and as shown in the Fig. 5 , they come as close as possible to engine 20 to block vein 204.

[0052] The forward position of the transmission system 223 thus corresponds to the forward position of the movable hood 216 and to the retracted position of the arms 250 and the retracted position of the transmission system 223 corresponds to the retracted position of the movable hood 216 and to the deployed position of the arms 250.

[0053] According to a particular embodiment, the actuator 219, the movable cover 216 and the transmission system 223 are arranged to ensure faster translational movement of the movable cover 216 than that of the transmission system 223 when they are subjected to the action of the actuator 219.

[0054] From the forward position of the movable hood 216, an actuation of the actuator 219 simultaneously moves the movable hood 216 and the transmission system 223 to their retracted position, preferably with a faster movement of the movable hood 216, and at the same time the arms 250 pass from the retracted position to the deployed position driving each sail 252 to its unfolded position. Conversely, from the retracted position of the movable hood 216, a reverse actuation of the actuator 219 simultaneously moves the movable hood 216 and the transmission system 223 to their forward position, preferably with a faster movement of the movable hood 216, and at the same time the arms 250 pass from the deployed position to the retracted position driving each sail 252 to its folded position.

[0055] The use of the arms 250 mounted rotatably on the movable cover 216 and the flexible veil 252 allows the assembly to be lightened compared to the use of reversing doors of the state of the art.

[0056] The flexible veil 252 must have sufficient structural characteristics to withstand the forces generated by the secondary flow 208 and be sufficiently flexible to be able to retract over the edges of the vein 204 in the retracted position. According to a particular embodiment, the flexible veil 252 consists of a flexible mesh structure on which a flexible skin such as a fabric for example is fixed.

[0057] There Fig. 6 shows an example of an actuator 219 which constitutes a dual-stroke actuator.

[0058] The actuator 219 comprises a fixed barrel 602 which is fixed to the fixed structure 206 and, in particular, to the cascade support 218. The fixed barrel 602 has a longitudinal axis A which is parallel to the translation direction and to the longitudinal direction X.

[0059] The actuator 219 also comprises a shaft 604 mounted to rotate inside the fixed barrel 602 around the longitudinal axis A. In the embodiment of the invention presented in the Fig. 6 , the shaft 604 is guided in rotation by a ball bearing 606 mounted between the fixed barrel 602 and the shaft 604.

[0060] The shaft 604 is driven in rotation around the longitudinal axis A by a motor M, for example of the electric motor type, controlled by the control unit.

[0061] The actuator 219 also includes a movable barrel 608 which is mounted inside the fixed barrel 602 and a proximal end of which is mounted outside the shaft 604.

[0062] The movable barrel 608 has, with the fixed barrel 602, a helical connection around the longitudinal axis A. For this purpose, the fixed barrel 602 has a thread on an inner surface and the movable barrel 608 has a thread on an outer surface which cooperates with the thread of the fixed barrel 602.

[0063] The movable barrel 608 has, with the shaft 604, a sliding connection along the longitudinal axis A. For this purpose, the shaft 604 has on an outer surface grooves 604a parallel to the longitudinal axis A and, for each groove 604a, the movable barrel 608 has, on an inner surface, from its proximal end, a groove 608a which slides along the groove 604a.

[0064] Thus, a rotation in one direction of the motor M will drive the shaft 604 in rotation and by effect of the helical connection and the sliding connection, the movable barrel 608 moves in rotation and in translation parallel to the longitudinal axis A, and depending on the direction of rotation of the motor M, the translational movement of the movable barrel 608 will be in one direction or the other.

[0065] The transmission system 223, one embodiment of which is shown in Fig. 7 is integral with the movable barrel 608, thus ensuring the translational movement of said transmission system 223 at a first speed linked to the first screw pitch of the helical connection between the fixed barrel 602 and the movable barrel 608.

[0066] At its distal end opposite the proximal end, the movable barrel 608 has a threaded bore 608b coaxial with the longitudinal axis A.

[0067] The actuator 219 also comprises a threaded rod 610, a proximal end of which is screwed inside the threaded bore 608b. Thus, the threaded rod 610 has, with the movable barrel 608, a helical connection around the longitudinal axis A.

[0068] At its distal end opposite the proximal end, the threaded rod 610 has a built-in connection with the movable cover 216. In the embodiment of the invention presented in Fig. 6 , the embedding connection is achieved by a circular groove made at the distal end of the threaded rod 610 and where the movable cover 216 has a tab which fits and is clamped in the circular groove.

[0069] Thus, because the threaded rod 610 is locked in rotation by the embedding connection, the rotation of the movable barrel 608 causes the threaded rod 610 to move in translation along the longitudinal axis A, and depending on the direction of rotation of the motor M, the translational movement of the threaded rod 610 will be in one direction or the other. The solidarity of the movable cover 216 with the threaded rod 610 ensures the translational movement of the movable cover 216 at a second speed linked to the second screw pitch of the helical connection between the movable barrel 608 and the threaded rod 610.

[0070] The directions of the different threads and tappings are the same so that the movements are made in the same direction for a given direction of rotation of the motor M.

[0071] In order for the movable hood 216 to move faster than the transmission system 223, the second speed must be greater than the first speed, which is made possible by a second screw pitch greater than the first screw pitch.

[0072] The transmission system 223 comprises a main gear 702 which is coaxially fixed on the movable barrel 608 and which therefore rotates and moves with it.

[0073] On either side of the main gear 702, the transmission system 223 comprises a spacer 704a-b which is tapped and screwed onto the thread of the movable barrel 608 and resting against a face of the main gear 702. Each spacer 704a-b is embedded in a first ball bearing 706a-b.

[0074] According to another embodiment, the spacers 704a-b are smooth and slidably mounted on the thread of the movable barrel 608 and bearing against a face of the main gear 702. Each spacer 704a-b is embedded in a first ball bearing 706a-b. When the main gear 702 moves, it pushes on the spacer 7040a-b which is in front of it.

[0075] The transmission system 223 also comprises a base 708 consisting here of two flanks 708a-b arranged on either side of the main gear 702 and made integral with each other by a beam 708c. Each flank 708a-b is crossed by a hole in which a first ball bearing 706a-b is embedded.

[0076] The base 708 has locking means 710 which ensure its locking in rotation relative to the longitudinal axis A. In the embodiment of the invention presented in Fig. 7 , the locking means 710 consist of a groove 710 parallel to the longitudinal axis A and the fixed structure 206 has a rib 206a (in ghost lines) which is parallel to the longitudinal axis A and which is arranged inside the groove 710 to ensure translational guidance parallel to the longitudinal axis A and rotational locking.

[0077] Thus, during the rotation and translation of the movable barrel 608, the main gear 702 follows the same movements, and due to the interaction between the tapping of each spacer 704a-b and the thread of the movable barrel 608, a rotation of the latter causes a rotational and translational movement of each spacer 704a-b which drives the base 708 blocked and guided by the rib 206a.

[0078] For each arm 250 that it carries, the transmission system 223 comprises a secondary gear 712 mounted to rotate on the base 708, here between the two flanks 708a-b, around an axis parallel to the longitudinal axis A and integral with said arm 250. The shaft of each secondary gear 712 is here embedded in a second ball bearing 714 which is itself embedded in a hole in the base 708, here in the corresponding flank 708a-b. Each secondary gear 712 is driven in rotation by the main gear 702 either directly by direct meshing between said secondary gear 712 and the main gear 702, or indirectly, by meshing between said secondary gear 712 and the main gear 702 through another secondary gear 712.

[0079] In order for the two sails 252 to unfold and fold at the same time, it is necessary for the directions of rotation of the secondary gears 712 to be reversed. In the embodiment of the invention shown in the Fig. 7 and the Figs. 4 And 5 , the main gear 702 meshes with a first secondary gear 712 and the second secondary gear 712 meshes with the first secondary gear 712.

[0080] In the case where there is a single arm 250, there is also a single first secondary gear 712.

[0081] The invention has been more particularly described in the case of a nacelle under a wing but it can be applied to a nacelle located at the rear of the fuselage.

Claims

1. Bypass turbofan (100) having a longitudinal direction (X) and including an engine (20) and a nacelle (102) surrounding the engine (20) that includes a fan cowl (202) in which a stream (204) of a secondary flow (208) is delimited between the nacelle (102) and the engine (20) and in which a flow of air circulates in a flow direction, said nacelle (102) including: - a fixed structure (206) fixed to the fan cowl (202) and including a cascade support (218) carrying cascades (221), - a mobile cowl (216) that is mobile in translation on the fixed structure (206) in a translation direction between an advanced position in which the mobile cowl (216) is positioned so that it is close to the fan cowl (202) and a retracted position in which the mobile cowl (216) is positioned so that it is far from the fan cowl (202) to define between them an open window (220) between the stream (204) and the exterior of the nacelle (102) and facing the cascades (221), - a plurality of transmission systems (223) each of which includes at least one arm (250) with a distal end and a proximal end mobile in translation on the transmission system (223) about a rotation axis globally parallel to the longitudinal direction (X), in which said arm (250) is mobile between a retracted position in which it is outside the stream (204) and a deployed position in which it is across the stream (204), in which each transmission system (223) is mobile in translation between an advanced position corresponding to the advanced position of the mobile cowl (216) and a retracted position corresponding to the retracted position of the mobile cowl (216), - for each arm (250), a flexible veil (252) having a first edge (252a) fastened to said arm (250), a second edge (252b) one end of which is fixed to an adjoining transmission system (223), and a third edge (252c), in which the veil (252) is mobile alternately between a folded position corresponding to the retracted position of the arm (250) in which the third edge (252c) is far from the engine (20) and an unfolded position corresponding to the deployed position of the arm (250), in which the third edge (252c) is close to the engine (20), and - for each transmission system (223), an actuator (219) adapted to move the mobile cowl (216) and said transmission system (223) simultaneously between their advanced position and their retracted position and vice versa and in which the transmission system (223) is adapted to move each arm (250) from its retracted position to its deployed position during movement of the transmission system (223) from its advanced position to its retracted position and vice versa, the bypass turbofan (100) being characterised in that the actuator (219) includes: - a fixed tube (602) fixed to the fixed structure (206) and that has a longitudinal axis (A) parallel to the longitudinal direction (X), - a shaft (604) mobile in rotation inside the fixed tube (602) about the longitudinal axis (A) and driven in rotation by a motor (M), - a mobile tube (608) mounted inside the fixed tube (602) and a proximal end of which is mounted outside the shaft (604), the mobile tube (608) having a helical connection with the fixed tube (602) with a first screw pitch about the longitudinal axis (A) and the mobile tube (608) having with the shaft (604) a sliding connection along the longitudinal axis (A), in which the transmission system (223) is fastened to the mobile tube (608) and in which at the level of a distal end the mobile tube (608) has an internally threaded bore (608b) coaxial with the longitudinal axis (A), and - a threaded rod (610) a proximal end of which is screwed into the internally threaded bore (608b) with a second screw pitch and a distal end of which has a pressed-in connection to the mobile cowl (216).

2. Bypass turbofan (100) according to claim 1 characterised in that a transmission system (223) carries a pair of arms (250).

3. Bypass turbofan (100) according to either one of claims 1 or 2, characterised in that the second screw pitch is greater than the first screw pitch.

4. Bypass turbofan (100) according to either one of claims 1 to 3, characterised in that the transmission system (223) includes: - a main gear (702) fixed coaxially onto the mobile tube (608), - on respective opposite sides of the main gear (702) a spacer (704a-b) that is internally threaded and screwed onto the external thread of the mobile tube (608) and bears against a face of the main gear (702), - for each spacer (704a-b), a first ball bearing (706a-b) into which said spacer (704a-b) is pressed, - a base (708) including on respective opposite sides of the main gear (702) a flange (708a-b), in which the two flanges (708a-b) are fastened to one another, in which each flange (708a-b) has a hole through it into which a first ball bearing (706a-b) is pressed, in which the base (708) includes immobilising means for immobilising it in rotation relative to the longitudinal axis (A), and - for each arm (250), a secondary gear (712) fastened to said arm (250) and mobile in rotation on the base (708) about an axis parallel to the longitudinal axis (A) and driven by the main gear (702).

5. Bypass turbofan (100) according to either one of claims 1 to 3, characterised in that the transmission system (223) includes: - a main gear (702) fixed coaxially onto the mobile tube (608), - on respective opposite sides of the main gear (702) a smooth spacer (704a-b) mounted to slide on the external thread of the mobile tube (608) and bearing against a face of the main gear (702), - for each spacer (704a-b), a first ball bearing (706a-b) into which said spacer (704a-b) is pressed, - a base (708) including on respective opposite sides of the main gear (702) a flange (708a-b), in which the two flanges (708a-b) are fastened to one another, in which each flange (708a-b) has a hole through it into which a first ball bearing (706a-b) is pressed, in which the base (708) includes immobilising means that immobilise it in rotation relative to the longitudinal axis (A), and - for each arm (250), a secondary gear (712) fastened to said arm (250) and mobile in rotation on the base (708) about an axis parallel to the longitudinal axis (A) and driven by the main gear (702).

6. Aircraft (10) including at least one bypass turbofan (100) according to any one of the preceding claims.