Linear actuation device and associated aircraft rotor test bench

Abstract

The present invention relates to a linear actuator (1) comprising a main actuator (11) having a main body (12) and a main rod (13) movable with at least one translational degree of freedom relative to said main body (12). According to the invention, the linear actuator (1) includes a backup system (20) configured to, in a nominal operating mode of the linear actuator (1), allow movement of the main rod (13) relative to the main body (12) and, in a backup operating mode of the linear actuator (1), return and then hold the main rod (13) in a predetermined safe position (PREF). (Shortcut figure: Figure 2)

Description

Title of the invention: Linear actuation device and associated aircraft rotor test bench

[0001] The present invention relates to the technical field of linear actuation devices. Such devices may include, for example, hydraulically, pneumatically or electrically controlled actuators or cylinders and at least two moving elements in translation relative to each other, such as a body and a rod.

[0002] For example, a rotor test bench may include several linear actuation devices to set in motion a set of swashplates of the rotor under test.

[0003] However, a linear actuation device may be subjected during its use to various cases of failure which may cause a malfunction, or even a failure preventing the control of the translation of a moving element.

[0004] Furthermore, for certain applications, such as on an aircraft rotor test bench where several linear actuation devices may be used, such a failure of a linear actuation device can be problematic and cause serious damage to the test bench and / or the system under test.

[0005] The present invention then aims to provide a device to improve the safety level of a linear actuation device.

[0006] The invention therefore relates to a linear actuation device comprising a main actuator equipped with a main body and a main rod movable with at least one degree of freedom in translation relative to the main body.

[0007] According to the invention, such a linear actuation device is remarkable in that it includes a backup system configured to: - in a nominal operating mode of the linear actuation device, allow a displacement of the main rod of the main actuator relative to the main body, and - in a backup operating mode of the linear actuation device, return and then hold the main rod of the main actuator in a predetermined safe position.

[0008] In other words, such a backup system can allow the main rod of the main actuator to be free to move as long as the linear actuation device is in its nominal operating mode.

[0009] Conversely, in the event of a failure of the main actuator or a control system for this main actuator, the backup system is activated to prevent the main rod from moving freely relative to the main body. Depending on From the current position of the main rod, when the emergency operating mode is activated, the emergency system can then move the main rod to place and maintain it in the predetermined safe position relative to the main body. The emergency system then prevents any further movement of the main rod relative to the main body.

[0010] Furthermore, such a main rod can be described as "through-rod" or "non-through-rod" within the main body. In the case of a through-rod, a piston head integral with the main rod and separating two pressure chambers is arranged between two rod segments. Alternatively, in the case of a non-through-rod, a piston head integral with the main rod is arranged at a free end of the main rod.

[0011] Furthermore, such a main rod may form either a monolithic assembly, or have at least two portions fixed together, or have at least two portions movable relative to each other. In the latter case, the main rod may, for example, comprise a first section and a second section movable at least in translation relative to each other along a principal axis of translation along which the main rod moves relative to the main body.

[0012] When such a linear actuation device is used on a rotor test bench, it can then allow, in the event of a malfunction of the main actuator or of the control of this main actuator, the pitch of the blades of this rotor to be controlled towards a predetermined pitch corresponding to the predetermined refuge position of the main rod of the main actuator.

[0013] For example, in this emergency operating mode of the linear actuation device, the predetermined pitch of the blades can correspond to a zero pitch so as not to transmit any vertical thrust on a test bench frame.

[0014] Furthermore, the transition from the nominal operating mode to the backup operating mode of the linear actuator can be performed automatically by the linear actuator using at least one sensor configured to detect a failure or malfunction of the main actuator or its control system. A controller then communicates with the sensor(s) and applies instructions to determine the presence of a malfunction and control the backup system accordingly.

[0015] Alternatively or complementarily, such a switch from the nominal operating mode to the emergency operating mode of the linear actuator can be operated by an operator monitoring the operation of the linear actuator. Such an operator thus activates a human-machine interface, such as a button, an emergency switch, or a touch panel, allowing both to deactivate the nominal operating mode of the linear actuator and activate the backup operating mode of the linear actuator.

[0016] Furthermore, the main actuator can be controlled by means of a hydraulic, pneumatic, or electrical control. For example, the main actuator may comprise a hydraulic cylinder connected to a hydraulic fluid supply system, the supply system comprising at least one hydraulic pump hydraulically connected to the main actuator by hoses.

[0017] The use of a hydraulic cylinder and hydraulic fluid makes it possible, in particular, to rapidly transmit the energy and pressure supplied by a pump to move the main rod. Furthermore, because it is a viscous fluid, the hydraulic fluid can also lubricate the various components such as the hydraulic pump, distributors, and the cylinder. In addition, one or more pressure accumulators can store the hydraulic fluid under pressure before it is distributed to the main actuator.

[0018] In practice, the backup system may include a secondary actuator equipped with a secondary body and a secondary rod movable with one degree of freedom in translation relative to the secondary body, the secondary rod being fixed to the main rod only in the backup operating mode of the linear actuation device.

[0019] Thus, such a secondary actuator can, for example, be mechanically arranged in parallel with the main actuator. The main rod has one degree of freedom in translation about a main axis of translation, and the secondary rod has one degree of freedom in translation about a secondary axis of translation parallel to the main axis of translation.

[0020] In the nominal operating mode of the linear actuation device, the secondary rod remains stationary in a rest position, for example median, predetermined with respect to the secondary body.

[0021] On the other hand, in the emergency operating mode of the linear actuation device, the secondary rod can be moved from the predetermined rest position, together with the main rod, to place and maintain the main rod in its predetermined refuge position.

[0022] According to another aspect, such a secondary actuator can be controlled by means of a hydraulic, pneumatic, or electrical control. For example, the secondary actuator may include an electric motor for rotating a worm screw cooperating with a nut or a ball mechanism capable of converting the rotational movement of the screw into a translational movement of the secondary rod.

[0023] Advantageously, the backup system may include adjustment means configured to axially adjust a relative position between the secondary body and the main body, as well as reversible fastening means configured to fasten the secondary body with the main body.

[0024] Such adjustment means make it possible to adapt the backup system according to a particular use of the linear actuation device and in particular to arrange the secondary rod in its predetermined rest position according to a particular total stroke of the main rod relative to the main body.

[0025] Thus, it is possible to use the same linear actuation device which is compatible with different rotor models and therefore to limit the design and manufacturing costs of the linear actuation devices equipping a test bench.

[0026] According to an advantageous embodiment, the backup system may comprise a hydraulic blocker attached to the secondary rod, the hydraulic blocker comprising a deformable clamping ring configured to: - in nominal operating mode, allow frictionless sliding of the main rod relative to the clamping ring, and - in the emergency operating mode, exert a pressing force on the main rod and make the main rod and the secondary rod fixed in translation.

[0027] In other words, such a locking device can be connected to a hydraulic actuator for controlling a state of the deformable clamping ring. Such a clamping ring may, in particular, have an internal cylindrical surface of revolution cooperating with an external cylindrical surface of revolution of the main rod.

[0028] In a nominal state of the deformable clamping ring implemented during nominal operating mode, the internal cylindrical surface of revolution has a functional clearance with the external cylindrical surface of revolution. Such a functional clearance is then suitable for allowing relative translational guidance between the main rod and the locking mechanism, and therefore with the secondary rod.

[0029] In a tight state of the deformable clamping ring implemented during the emergency operating mode, the internal cylindrical surface of revolution has a tight fit with the external cylindrical surface of revolution.

[0030] Furthermore, the significant deformation capacity of the clamping ring can be achieved by means of a plurality of notches arranged, for example, axially within the thickness of the clamping ring. Two successive notches may also open onto two opposing flat faces, defining an external volume of the clamping ring. Each notch may then have a through end cooperating with an external flat face of the clamping ring and a non-through end open end cooperating with an internal cylindrical face of a radial bore of the clamping ring.

[0031] Furthermore, the coefficient of friction between the clamping ring and the main rod can be improved by depositing a material. A thin layer of material intended to increase the coefficient of friction can thus be applied, at least locally, to the internal cylindrical surface of revolution.

[0032] In practice, the hydraulic blocker may include: - a crankcase, - a plurality of pistons arranged radially in the housing with respect to a main axis of translation of the main rod's displacement, the pistons sliding respectively in chambers hydraulically connected in parallel to a hydraulic supply comprising a pump configured to compress a fluid in the chambers, the fluid enabling a thrust force to be exerted on each piston to place each piston in a first extreme position corresponding to the nominal operating mode, and - elastic return means each exerting a return force on a piston to move each piston from the first extreme position to a second extreme position corresponding to the emergency operating mode.

[0033] In other words, the hydraulic supply makes it possible to position and maintain the pistons in their first extreme position inside the housing to allow the deformable clamping ring to be arranged in its nominal state.

[0034] In addition to a pump, such a hydraulic supply may include other hydraulic elements such as hoses and one or more pressure accumulators.

[0035] Advantageously, the rescue system may include a tracking system configured to generate tracking information based on a current position of the main rod relative to the main body relative to the refuge position.

[0036] Thus, such a tracking system makes it possible at all times to track the current position of the main rod and to know, when the emergency operating mode is implemented, in which direction the main rod must be moved to approach its refuge position and position itself there.

[0037] According to one embodiment of the invention, the tracking system may comprise a sleeve movable with one degree of freedom in translation relative to a support along a tracking translation axis, the sleeve being fixed to the main rod and configured to move in translation jointly with the main rod, the tracking translation axis being parallel to the main translation axis.

[0038] In other words, a connecting arm allows the main rod and the sleeve to be joined together, for example at their respective free ends. Such a connecting arm can extend perpendicularly with respect to the main axis of translation.

[0039] In practice, the sheath may comprise an external cylindrical surface provided with three tracks oriented parallel to each other along the tracking translation axis, the three tracks being respectively offset in azimuth from each other around the tracking translation axis.

[0040] Each track can thus extend longitudinally along the tracking translation axis. The tracks can, for example, be arranged side by side on the external cylindrical surface of the sleeve or be angularly offset by 120° from each other.

[0041] Advantageously, the tracking system may include three sensors attached to the support, each track being arranged opposite a sensor and having at least two colored portions having at least two different colors intended to be identified by the sensor.

[0042] Each sensor can be of a logic or on / off type, that is, providing a change of state digitally with a value of 0 or 1. For example, each sensor can detect a colored portion of a track, and the sensors together allow the determination of the current relative position of the sleeve with respect to the safe position using a Boolean algebra truth table. For example, the safe position can be defined by the simultaneous identification on the three tracks of a combination of three colored portions having the same first color.

[0043] A first track can thus have two colored portions of different colors arranged one after the other in a direction parallel to the tracking translation axis. For example, a first colored portion, arranged in an upper part of the sheath, has the first color and a second colored portion, arranged in a lower part of the sheath, has a second color.

[0044] This first track can indicate a first direction of movement of the main rod relative to its refuge position. According to the example described above, this first direction of movement can thus correspond to an axis oriented from the lower part of the sheath to the upper part of the sheath.

[0045] A second track may, in turn, have two colored portions of different colors arranged one after the other in a direction parallel to the tracking translation axis, the arrangement of the two colored portions of the second track being reversed compared to that of the first track. For example, a first colored portion arranged in the lower part of the sheath has the first color and a second colored portion, arranged in the upper part of the sheath, displays the second color. The refuge position can then be identified at a very localized azimuth overlap of the first colored portions of the first and second tracks.

[0046] This second track can indicate a second direction of movement, opposite to the first direction of movement, of the main rod relative to its refuge position. This second direction of movement can thus correspond to an axis oriented from the upper part of the sheath towards the lower part of the sheath.

[0047] In addition, the main rod can be arranged in its safe position when both a first sensor detects the first color on the first track and a second sensor detects the first color on the second track.

[0048] Finally, a third track may have three colored portions with two different colors arranged one after the other in a direction parallel to the tracking translation axis.

[0049] For example, a first colored portion arranged in a central part of the sleeve displays the first color, a second colored portion, arranged in the upper part of the sleeve, displays the second color, and a third colored portion, arranged in the lower part of the sleeve, displays the second color. When detected by a third sensor, the second and third colored portions then indicate that a limit stop of the main rod has been reached.

[0050] In conjunction with the detection of the second colored portions of the first and second tracks, the truth table makes it possible to identify whether it is an upper or lower limit stop. Indeed, when the second colored portion of the first track is detected simultaneously with the second colored portion of the third track, an upper limit stop can be identified, and when the second colored portion of the second track is detected simultaneously with the third colored portion of the third track, a lower limit stop can be identified.

[0051] According to another embodiment of the invention, the rescue system comprising a secondary actuator equipped with a secondary body and a secondary rod movable with one degree of freedom in translation relative to the secondary body, the tracking system may include a controller connected to the three sensors to generate tracking information based on the current position of the main rod relative to the refuge position and to command the secondary actuator to move the main rod into the refuge position.

[0052] Thus, such a tracking system controller is connected by wire or wireless means to the three sensors and makes it possible to constantly know the relative position of the main rod with respect to its safe position. The controller can also identify from the truth table in Boolean algebra if the main rod has reached one of its end stops.

[0053] When the nominal operating mode is implemented, the controller can send a control command to the main actuator to stop a movement of the main rod when it has reached one of the end stops.

[0054] Furthermore, when the emergency operating mode is implemented, the controller can send a command order to the secondary actuator to recall the main rod to the refuge position.

[0055] In practice, the linear actuation device may include at least one balancing counterweight offset radially with respect to a main translation axis of displacement of the main rod.

[0056] The balancing counterweight(s) are further configured to counteract any imbalance generated by the backup system. Thus, depending on the mass and position of the backup system relative to the main axis of translation, the number and mass of the balancing counterweight(s) can be modified. The balancing counterweight(s) then make it possible to bring the center of gravity of a linear actuation device back onto the main axis of translation.

[0057] The present invention also relates to an aircraft rotor test bench, the rotor being equipped with a hub and blades, the test bench comprising a motor enabling the rotor to be driven in rotation.

[0058] According to the invention, such a test bench is remarkable in that it comprises at least one linear actuation device as described above, and in that, during a rotational movement of the rotor, said at least one linear actuation device is configured to, in the nominal operating mode, vary a pitch of the rotor blades relative to the hub and, in the emergency operating mode, to maintain the pitch of the rotor blades towards a predetermined value.

[0059] In practice, the test bench may include at least three linear actuation devices according to the invention arranged in place of the servo controls that vary the pitch of the rotor blades when the rotor is mounted on an aircraft. The three linear actuation devices may then be arranged, for example, in an evenly distributed manner around the axis of rotation of the rotor.

[0060] A first end of each linear actuation device is arranged in a ball joint or pivot connection with a test bench frame and can thus present at least one degree of rotational freedom relative to this frame.

[0061] Similarly, a second end of each linear actuation device is arranged in a ball joint or pivot connection with a rotor blade pitch control plate system and can thus present at least one degree of rotational freedom relative to this rotor blade pitch control plate system.

[0062] Such a test bench is therefore safe and can limit the level of risk of accident in the event of malfunction of a main actuator during the use of the test bench and during the rotation of a rotor at high rotational speeds.

[0063] The invention and its advantages will become apparent in more detail in the following description, with illustrative examples given by reference to the accompanying figures, which represent:

[0064] [Fig. 1], a perspective view of a test bench according to the invention,

[0065] [Fig. 2], a perspective view of a linear actuation device conforming to the invention,

[0066] [Fig. 3], a perspective view of a secondary actuator of the linear actuation device, according to the invention,

[0067] [Fig. 4], a perspective view of a hydraulic blocker of the linear actuation device, according to the invention,

[0068] [Fig. 5], a perspective cross-sectional view of the hydraulic blocker of the linear actuation device, according to the invention,

[0069] [Fig. 6], a cross-sectional view of the hydraulic blocker of the linear actuation device, according to the invention,

[0070] [Fig. 7], a partial perspective view of the hydraulic blocker of the linear actuation device, according to the invention,

[0071] [Fig. 8], a perspective cross-sectional view of a piston of the hydraulic blocker of the linear actuation device, according to the invention,

[0072] [Fig. 9], a perspective view of a linear actuation device tracking system, according to the invention,

[0073] [Fig. 10], a perspective view of a sleeve of the linear actuation device tracking system, according to the invention,

[0074] [Fig. 1 1], a perspective view of the tracking system of the linear actuation device, according to the invention,

[0075] Elements present in several separate figures are assigned one and the same reference.

[0076] As shown in [Fig. 1], the invention relates, for example, to the field of test benches 2 for testing aircraft rotors 3, such as rotors of a rotary-wing aircraft. Such a rotor 3 to be tested is thus equipped with a hub 4 and variable-pitch blades 5 carried by the hub 4. A conventional system of swashplates can further allow the pitch of the rotor blades to be varied cyclically and collectively, by being connected to the blades by connecting rods.

[0077] In addition, such a test bench 2 includes a motor 6 for driving the rotor 3 in rotation to simulate normal operation on an aircraft.

[0078] Furthermore, to modify the pitch of the rotor 3 blades 5, the test bench 2 includes at least one linear actuator 1 connected on one side to the swashplate system and on the other side to a frame of the test bench. During a rotation of the rotor 3, the linear actuator(s) 1 allow, in a nominal operating mode, the pitch of the rotor 3 blades 5 relative to the hub 4 to be varied and, in a backup operating mode, to maintain the pitch of the rotor 3 blades 5 at a predetermined value.

[0079] Such a test bench 2 can thus include linear actuation devices 1 replacing respective servocontrols equipping an aircraft when the rotor 3 is used under normal conditions on the aircraft.

[0080] Such a linear actuation device 1 is shown in more detail in [Fig.2] and allows the operation and stresses of a rotor 3 to be simulated on the ground.

[0081] This linear actuation device 1 includes, in particular, a main actuator 11 equipped with a main body 12 and a main rod 13 movable with one degree of freedom in translation relative to the main body 12. Thus, the main rod 13 can be moved relative to the main body 12 along a main axis of translation Axl. For example, if the main actuator 11 is a hydraulic cylinder, the main rod 13 is integral with a piston arranged in the main body 12. The piston is then moved with the main rod 13 by means of a pressurized fluid transmitted into a chamber by a main hydraulic supply (not shown). Alternatively, such a main actuator 11 may be an electric or pneumatic cylinder.

[0082] According to a remarkable feature of the invention, this linear actuation device 1 includes a backup system 20 allowing, in a nominal operating mode of the linear actuation device 1, a displacement of the main rod 13 relative to the main body 12.

[0083] On the other hand, in a backup operating mode of the linear actuation device 1, the backup system 20 makes it possible to immobilize the main rod 13 of the main actuator 11 in a predetermined refuge position PREF.

[0084] This backup system 20 can include a secondary actuator 21 equipped with a secondary body 22 which can, for example, be integral with the main body 12 and a secondary rod 23 movable according to a degree of freedom in translation relative to the secondary body 22.

[0085] Thus, the secondary rod 23 can be moved relative to the secondary body 22 along a secondary translation axis Ax2, for example, by means of an electric motor if the secondary actuator 21 is an electric cylinder. Alternatively, the secondary actuator 21 can be a hydraulic or pneumatic cylinder.

[0086] In addition, the secondary rod 23 is secured to the main rod 13 only in the emergency operating mode of the linear actuation device 1.

[0087] To do this, the backup system 20 may include a hydraulic blocker 26 attached to the secondary rod 23.

[0088] Furthermore, the rescue system 20 may also include a tracking system 40 configured to generate tracking information based on a current position of the main rod 13 relative to the main body 12 relative to the refuge position PREF.

[0089] Finally, such a linear actuation device 1 may include at least one balancing counterweight 61 offset radially with respect to the main translation axis Axl.

[0090] Such a balancing counterweight 61 thus makes it possible to counter the imbalance generated by the use of the secondary actuator 21 which is also radially offset with respect to the main translation axis Axl.

[0091] As shown in [Fig.3], the backup system 20 may include adjustment means 24 configured to axially adjust a relative position between the secondary body 22 and the main body 12 as well as reversible fastening means 25 configured to fasten the secondary body 22 with the main body 12.

[0092] The adjustment means 24 may include oblong holes 122 and / or a plurality of holes 122 spaced at the same center distance and allowing adjustment of different fixing positions between the secondary body 22 and the main body 12. In addition, as shown, the holes 122 may be arranged on a bracket 121 fixed to the main body 12.

[0093] The reversible fastening means 25 can, for their part, be formed by screws or studs and complementary nuts.

[0094] Furthermore, the backup system 20 may include a first connecting arm 120 attached on one side to the secondary rod 12 and on the other side to the hydraulic lock 26 by conventional means of screwing, welding, or otherwise. Such a first connecting arm 120 then allows the main rod 13 and the secondary rod 23 to be joined by means of the hydraulic lock 26 in the backup operating mode of the linear actuation device 1. Such a first connecting arm 120 may, for example, extend substantially perpendicularly with respect to the main translation axis Ax1 and the secondary translation axis Ax2.

[0095] Such a secondary actuator 21 may include an electric motor 123 and a belt-driven right-angle transmission system 124 for rotating a worm gear 125 and generating translational movement of the secondary rod 23 by means of a nut fixed to the secondary rod 23 or a ball mechanism 126 capable of converting the rotational movement of the worm gear 125 into a translational movement of the secondary rod 23.

[0096] As shown in more detail in figures 4 to 8, the hydraulic blocker 26 includes a deformable clamping ring 27 configured in the nominal operating mode to allow frictionless sliding of the main rod 13 within it. In the emergency operating mode, the deformable clamping ring 27 is configured to exert a pressing force on the main rod 13 in order to make the main rod 13 and the secondary rod 23 fixed together in translation.

[0097] Furthermore, according to [Fig. 4], the hydraulic blocker 26 also includes a housing 28 within which the clamping ring 27 is arranged. Moreover, such a housing 28 has an internal volume that allows both the clamping ring 27 to be contained and the clamping ring 27 to be deformed radially around the main rod 13.

[0098] As shown in figures 5 to 8, the hydraulic blocker 26 also includes a plurality of pistons 29 arranged in the housing 28 and movable radially with respect to the main translation axis Axl.

[0099] As shown in Figures 6 and 7, such pistons 29 can slide respectively in chambers 37 hydraulically connected in parallel to a hydraulic supply 30 comprising a pump 31. Such a pump 31 is then configured to compress a fluid in the chambers 37 in the nominal operating mode of the linear actuation device 1.

[0100] Such a pressurized fluid then makes it possible to exert a pushing force on each piston 29 to place each piston 29 in a first extreme position during the nominal operating mode.

[0101] Furthermore, the hydraulic blocker 26 also includes elastic return means 32, such as deformable conical washers, jointly exerting a return force on a piston 29 to move each piston 29 from its first extreme position to a second extreme position when the fluid is no longer under pressure in each chamber 37 during the emergency operating mode. Consequently, the pistons 29 exert forces on the clamping ring 27. The pistons 29 deform the clamping ring 27, which then clamps the main rod.

[0102] Advantageously, such a hydraulic blocker 26 may include a plurality of stops 33 and an elastic ring 34 allowing the restoring force generated by the elastic restoring means 32 to be increased on each piston 29.

[0103] Each stop 33 cooperates via a sliding pivot joint with a piston 29 so as to center the stop 33 relative to the piston 29 and allow at least one degree of translational freedom to a stop 33 relative to a piston 29. Each stop 33 cooperates via a plane-support type joint with a means of elastic return 32 to serve as an axial stop and to oppose the thrust force exerted by the piston 29 stressed in the first extreme position by the pressurized fluid.

[0104] As shown in [Fig.7], the hydraulic blocker 26 may comprise nine pistons 29 and nine stops 33 arranged radially between the clamping ring 27 and the elastic ring 34.

[0105] As shown in [Fig.8], the hydraulic blocker 26 may include sealing gaskets 35 allowing the hydraulic fluid supplied by the hydraulic supply system 30 to be contained in a sealed manner in each of the chambers 37 delimited by the housing 28 and the piston 29. The hydraulic fluid can then exert a thrust force on a flat face 38 of the piston 29.

[0106] In addition, the hydraulic blocker 26 may also include guide rings 36 to guide each piston 29 in translation within the housing 28.

[0107] As shown in [Fig. 9], the tracking system 40 may include a sleeve 41 movable with one degree of freedom in translation relative to a support 42 along a tracking translation axis Ax3. Such a sleeve 41 is fixed to the main rod 13 by means of a second connecting arm 140 fixed by a fixed connection to the respective free ends of the main rod 13 and the sleeve 41. Such a second connecting arm 140 may extend perpendicularly with respect to the main translation axis AX1 and to the tracking translation axis Ax3.

[0108] Such a sheath 41 can thus move in translation jointly with the main rod 13, the tracking translation axis Ax3 being parallel to the main translation axis Axl.

[0109] Furthermore, the support 42 can be secured to the main body 12 of the main actuator 11.

[0110] As shown in [Fig. 10], the sleeve 41 may have an external cylindrical surface 43 provided with three tracks 44, 45, 46 oriented parallel to each other along the tracking translation axis Ax3. These three tracks 44, 45, 46 may be arranged against each other or be respectively offset in azimuth from each other around the tracking translation axis Ax3.

[0111] Each of the three tracks 44, 45, 46 may have at least two colored portions 50, 51 intended to cooperate with three sensors 47, 48, 49 of the tracking system 40.

[0112] As shown in [Fig. 11], the three sensors 47, 48, 49 are fixed to the support 42 and allow identification of which colored portion 50, 51 is arranged opposite the sensors 47, 48, 49 in order to determine the relative position of the main rod 13 with respect to its safe position PREF. In practice, each sensor 47, 48, 49 can provide a binary digital signal such that 0 when a first colored portion 50 is arranged opposite and alternately 1 when a second colored portion 51 is arranged opposite.

[0113] Thus, each track 44, 45, 46 is arranged opposite a sensor 47, 48, 49 and comprises at least two colored portions 50, 51 having at least two different colors intended to be identified by the sensor 47, 48, 49.

[0114] Each sensor 47, 48, 49 thus detects a colored portion 50, 51, and the sensors together determine the current relative position of the sheath 41 with respect to the safe position PREF using a Boolean algebra truth table. For example, the safe position can be defined by the simultaneous identification on the three tracks 44, 45, 46 of a combination of three colored portions 50 having the same first color. According to the truth table, each colored portion 50 is then assigned the value 0 and each colored portion 51 is assigned the value 1.

[0115] A first track 44 can thus have two colored portions 50, 51 of different colors arranged one after the other along a direction parallel to the tracking translation axis Ax3. For example, a first colored portion 50, arranged in an upper part of the sleeve 41, has the first color and a second colored portion 51, arranged in a lower part of the sleeve 41, has a second color.

[0116] This first track 44 can indicate a first direction of movement of the main rod 13 relative to its refuge position PREF. According to the example described above, this first direction of movement can thus correspond to an axis oriented from the lower part of the sheath 41 towards the upper part of the sheath 41.

[0117] A second track 45 may, in turn, have two colored portions 50, 51 of different colors arranged one after the other along a direction parallel to the tracking translation axis Ax3, the arrangement of the two colored portions 50, 51 of the second track 45 being reversed with respect to that of the first track 44. For example, a first colored portion 50 arranged in the lower part of the sleeve 41 displays the first color and a second colored portion 51, arranged in the upper part of the sleeve 41, displays the second color. The refuge position PREF can then be identified at a very localized azimuth overlap of the first colored portions 50 of the first and second tracks 44, 45.

[0118] This second track 45 can indicate a second direction of movement, opposite to the first direction of movement, of the main rod 13 relative to its safe position PREF. This second direction of movement can thus correspond to an axis oriented from the upper part of the sleeve 41 towards the lower part of the sleeve 41.

[0119] Finally, a third track 46 may have three colored portions 50, 51 with two different colors arranged one after the other in a direction parallel to the tracking translation axis Ax3.

[0120] For example, a first coloured portion 50 arranged in a central part of the sheath 41 has the first colour, a second coloured portion 51, arranged in the upper part of the sheath 41, has the second colour and a third coloured portion 51, arranged in the lower part of the sheath 41, also has the second colour.

[0121] In addition, the main rod 13 can be arranged in its safe position PREF when both a first sensor 47 detects the first color on the first track 44, a second sensor 48 detects the first color on the second track 45 and a third sensor 49 detects the first color on the third track 46.

[0122] The second and third colored portions 51, when detected by the third sensor 49, then make it possible to identify that a stop at the end of the stroke of the main rod 13 has been reached.

[0123] In conjunction with the detection of the second colored portions 51 of the first and second tracks 44, 45, the truth table makes it possible to identify whether it is an upper or lower limit stop. Indeed, when the second colored portion 51 of the first track 44 is simultaneously detected with the second colored portion 51 of the third track 46, an upper limit stop can be identified, and when the second colored portion 51 of the second track 45 is simultaneously detected with the third colored portion 51 of the third track 46, a lower limit stop of the main rod 13 can be identified.

[0124] In addition, the tracking system 40 may include a controller 60 connected to the three sensors 47, 48, 49 to generate tracking information based on the current position of the main rod 13 relative to the refuge position PREF.

[0125] Based on the tracking information, the controller 60 can command the secondary actuator 21 to move and hold the main rod 13 in the PREF refuge position.

[0126] The controller 60 can use the Boolean algebra truth table stored in memory. For example, the safe position PREF can be defined by a combination of three first colored portions 50 with an identical first color corresponding to a median area of ​​the sheath 4L

[0127] A first direction of movement of the main rod 13 can be controlled when a second colored portion 51 having a second color is detected on the first track 44 by the first sensor 47.

[0128] A second direction of movement of the main rod 13 can be controlled when a second colored portion 51 exhibiting a second color is detected on the second track 45 by the second sensor 48.

[0129] A high stop of the main rod 13 can be identified when both a second colored portion 51 exhibiting a second color is detected on the first track 44 by the first sensor 47 and a second colored portion 51 exhibiting a second color is detected on the third track 46 by the third sensor 49.

[0130] Finally, a lower stop of the main rod 13 can be identified when both a second colored portion 51 exhibiting a second color is detected on the second track 45 by the second sensor 48 and a second colored portion 51 exhibiting a second color is detected on the third track 46 by the third sensor 49.

[0131] Naturally, the present invention is subject to numerous variations in its implementation. Although several embodiments have been described, it is understood that it is not conceivable to exhaustively identify all possible embodiments. It is, of course, conceivable to replace a described means with an equivalent means without departing from the scope of the present invention as defined by the claims.

Claims

Demands

1. A linear actuation device (1) comprising a main actuator (11) having a main body (12) and a main rod (13) movable with at least one translational degree of freedom relative to said main body (12), said linear actuation device (1) comprising a backup system (20) configured to: - in a nominal operating mode of said linear actuation device (1), allow a displacement of said main rod (13) of said main actuator (11) relative to said main body (12), and - in a backup operating mode of said linear actuation device (1), return and then hold said main rod (13) of said main actuator (11) in a predetermined safe position (PREF), said backup system (20) comprising a secondary actuator (21) provided with a secondary body (22) and a secondary rod (23) movable with one degree of freedom in translation relative to said secondary body (22), said secondary rod (23) being fixed with said main rod (13) only in said backup operating mode of said linear actuation device (1), characterized in that said emergency system (20) comprises a hydraulic blocker (26) secured to the secondary rod (23), said hydraulic blocker (26) comprising a deformable clamping ring (27) configured for: - in said nominal operating mode, to allow frictionless sliding of said main rod (13) relative to said clamping ring (27), and - in said emergency operating mode, exert a pressing force on said main rod (13) and make said main rod (13) and said secondary rod (23) fixed in translation.

2. Device according to claim 1, characterized in that said backup system (20) comprises adjustment means (24) configured to axially adjust a relative position between said secondary body (22) and said main body (12) and reversible fastening means (25) configured to fasten said secondary body (22) with said main body (12).

3. Device according to any one of claims 1 to 2, characterized in that said hydraulic blocker (26) comprises: - a housing (28), - a plurality of pistons (29) arranged in said housing (28) radially with respect to a main axis of translation (Axl) of displacement of said main rod (13), said pistons (29) sliding respectively in chambers (37) hydraulically connected in parallel to a hydraulic supply (30) comprising a pump (31) configured to compress a fluid in said chambers (37), said fluid enabling a thrust force to be exerted on each piston (29) to place each piston (29) in a first extreme position corresponding to said nominal operating mode,and - elastic return means (32) each exerting a return force on a piston (29) to move each piston (29) from said first extreme position to a second extreme position corresponding to said emergency operating mode.

4. Device according to any one of claims 1 to 3, characterized in that said backup system (20) comprises a tracking system (40) configured to generate tracking information as a function of a current position of said main rod (13) relative to said main body (12) relative to said refuge position (PREF).

5. Device according to claim 4, characterized in that said tracking system (40) comprises a sleeve (41) movable with one degree of freedom in translation relative to a support (42) along a tracking translation axis (Ax3), said sleeve (41) being integral with said main rod (13) and configured to move in translation jointly with said main rod (13), said tracking translation axis (Ax3) being parallel to said main translation axis (Axl).

6. Device according to claim 5, characterized in that said sleeve (41) comprises an external cylindrical surface (43) provided with three tracks (44, 45, 46) oriented parallel to said tracking translation axis (Ax3), said three tracks (44, 45, 46) being respectively offset in azimuth from one another around said tracking translation axis (Ax3).

7. Device according to claim 6, characterized in that said tracking system (40) comprises three sensors (47, 48, 49) attached to said support (42), each track (44, 45, 46) being arranged opposite a sensor (47, 48, 49) and having at least two colored portions (50, 51) having at least two different colors intended to be identified by said sensor (47, 48, 49).

8. Device according to claim 7, characterized in that, said backup system (20) comprising a secondary actuator (21) provided with a secondary body (22) and a secondary rod (23) movable with one degree of freedom in translation relative to said secondary body (22), said tracking system (40) comprises a controller (60) connected to the three sensors (47, 48, 49) to generate said tracking information as a function of said current position of said main rod (13) relative to said refuge position (PREF) and to command said secondary actuator (21) to move said main rod (13) into said refuge position (PREF).

9. Device according to any one of claims 1 to 8, characterized in that said linear actuation device (1) comprises at least one balancing counterweight (61) offset radially with respect to a principal translation axis (Axl) of displacement of said main rod (13).

10. Aircraft rotor (3) test bench (2), said rotor (3) being provided with a hub (4) and blades (5), said test bench (2) comprising a motor (6) for driving said rotor (3) in rotation, characterized in that said test bench (2) comprises at least one linear actuation device (1) according to any one of claims 1 to 9, and in that, during a rotational movement of said rotor (3), said at least one linear actuation device (1) is configured to, in said nominal operating mode, vary a pitch of the blades (5) of said rotor (3) relative to said hub (4) and, in said emergency operating mode, to maintain said pitch of said blades (5) of said rotor (3) towards a predetermined value.

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