Rotary electro-mechanical actuator and a method for operating the same

Abstract

Rotary electro-mechanical actuator, comprising an actuator member (7), moved to adopt a first component of rotary movement about a main axis (X) and a second component of axial movement along said main axis (X), said first and second components being individually adjustable between a zero speed value and a maximum speed value and preferably adjustable independently of each other; a transmission element (8), having roto-translational movement about the main axis (X) by means of a base thread (9) and connected to the actuator member (7) in an axially integral fashion with said actuator member (7); and a rotary outlet element (6) rotatable about the main axis (X) and connected to the transmission element (8) in such a way as to have a rotational movement integral with the rotary component of the movement of the transmission element (8).

Description

[0001] ROTARY ELECTRO-MECHANICAL ACTUATOR AND A METHOD FOR OPERATING THE SAME

[0002] DESCRIPTION

[0003] The present invention relates to a rotary electro-mechanical actuator and is used in particular in the aeronautical field in particular landing carriages, flight surfaces, motor rotation systems (thrust conversion) and more generally where electrical and electronic redundancy is requested.

[0004] Rotary electro-mechanical actuators are known in the prior art comprising an electric motor and a two-state transmission with different pitches, in such a way as to obtain an optimised reduction ratio and with a compact structure. A similar actuator is described in patent EP4042039 in the name of the Applicant.

[0005] The Applicant has found that these actuators can be further improved in order to guarantee the versatility of utilisation, in particular according to different uses or with use in different operating conditions. The prior art architecture allows, in effect, optimisation for a specific situation but does not allow adaptation to different situations of use.

[0006] Moreover, particularly in the aeronautical field, there is the need for actuators which are increasingly reliable and which are therefore able to operate with a high safety margin.

[0007] In this context, the Applicant has found that by adopting a technical solution using a roto-translational actuator member, which is able to have a controllable rotation and / or translation movement, it is possible to have a wide range of conditions of use, in particular both for high loads and for high movements.

[0008] In particular, by adopting a power inlet component of the roto-translational type, with adjustable balance between the rotary and translational components, it is possible to insert a predetermined power in the mechanical transmission transforming the axial movement component of the actuator member into a roto- translational movement of a connecting element connected to the actuator member. The rotary component of the roto-translational movement may therefore be derived by means of a purely rotary outlet element. In other words, under equal conditions of power transmitted, the adjustment of the balance between the rotary and translational components allows the actuator to be operated in accordance with different performance levels, giving the actuator a vast possibility of applications or, within the same application, different operating conditions.

[0009] Moreover, the Applicant has found that the roto-translational movement of the actuator member may be performed by means of two distinct motors, which can be independently controlled. This allows greater degree of freedom in adjustment as well as greater reliability since one of the two motors can, in emergency conditions, operate as redundant in relation to the other motor.

[0010] In this context, the invention relates to a rotary electro-mechanical actuator comprising:

[0011] - a containment frame, preferably box-shaped defining an inner space;

[0012] - a movement unit, in particular motor-driven, positioned in the containment space;

[0013] - an actuator member, moved by the movement unit;

[0014] - a transmission element, connected to the frame by a base thread in such a way as to adopt a roto-translational movement about a main axis;

[0015] - a rotary outlet element connected to the transmission element and rotatable about the main axis, where the rotary element has a rotational movement integral (that is to say, synchronous and integrated) with the rotary component of the transmission element’ s movement.

[0016] The actuator member, which extends about the main axis, is configured to adopt a first component of rotary movement about the main axis and a second component of axial movement along said main axis.

[0017] The expression “configured to adopt” means that the actuator member has the possibility of adopting both movement components or, alternatively, can be moved only with the rotation component or only with the translation component, depending on the adjustment action used. In particular, the first and second components of movement of the actuator member are individually adjustable between a zero speed value and a maximum speed value and preferably adjustable independently of each other.

[0018] The term “maximum value” means a maximum speed value irrespective of the direction of rotation. In particular, this means that the actuator member may be actuated, in rotation and / or in translation, in both directions and, moreover, each of the movement components may be stopped independently.

[0019] Moreover, the actuator member is connected to the transmission element in a fashion that is axially integral to it. This may be obtained, for example, by means of a circular guide and / or one or more rolling bearings (rollers, balls). In this way, the rotary component of the movement of the actuator member is absorbed by the circular guide and / or by the bearings and not transmitted to the transmission element, which, on the other hand, receives the entire component of axial movement of the actuator member.

[0020] In turn, the transmission element, being connected to the frame by the base thread, due to the axial thrust exerted by the actuator member is constrained to follow a roto-translational movement, whose rotary component about the main axis is independent from the rotary component of the actuator member due to the above- mentioned circular guide and / or the above-mentioned bearings.

[0021] The rotary component of that roto-translational movement of the transmission element is therefore transmitted to the rotary outlet element. This is preferably obtained by connecting the transmission element to the rotary outlet element in a fashion that is rotationally integral with it, for example by means of a linear guide (grooved or recirculating ball screw). In that way, the axial component of the roto- translational movement of the transmission element is absorbed by the linear guide and not transmitted to the rotary outlet element, which, on the other hand, receives the entire component of rotary movement of the transmission element. Preferably, the movement unit comprises a first and a second motor, in particular rotary, which can be controlled independently from each other. The adjustment of the two motors makes it possible to control, independently of each other, the two components (rotary / translational) of the movement of the actuator member.

[0022] Preferably, the respective axes of rotation of the two motors are parallel to the main axis and angularly spaced from each other about the main axis, preferably at the same distance from the main axis.

[0023] The two motors are also preferably mounted on the containment frame, in particular inside the containment space and preferably inside respective dedicated compartments.

[0024] According to an embodiment, the movement unit comprises a first rotary inlet element and a second rotary inlet element, engaged with the actuator member by means of a first inlet thread and a second inlet thread respectively. Each rotary element is rotated by one of the above-mentioned motors respectively in such a way that the two rotary inlet elements can be selectively rotated and driven independently. It follows that, by varying the speed of rotation of one rotary inlet element or of both rotary inlet elements, the movement of the actuator member is consequently varied, and in particular the distribution of the rotary component and of the translational component is varied. It is in fact possible to cancel the translational component by stopping the rotation of the rotary outlet element, or to cancel the rotary component by maximising the rotary outlet. Obviously, continuous adjustment of the motors allows the reaching of intermediate movement conditions of the actuator member, with the balance of the rotary component and the translational component variable between zero value and a corresponding maximum value.

[0025] Preferably, the first inlet thread and the second inlet thread are positioned on respective separate zones of the actuator member.

[0026] According to an embodiment, the first inlet thread and the second inlet thread are positioned on surfaces opposite each other, for example on an outer cylindrical surface and on an inner cylindrical surface.

[0027] In this situation, the actuator member has a central hole, for example made by means of a tubular shape, and the first rotary inlet element is inserted in the hole whilst the second rotary inlet element is positioned outside the actuator member. The first inlet thread and the second inlet thread may be positioned in an axially superposed or partly superposed position or occupy respective regions axially offset from each other.

[0028] Alternatively, the first inlet thread and the second inlet thread may be positioned on the same side, in particular on a same outer or inner cylindrical surface or on outer / inner cylindrical surfaces facing each other on the same side and adjacent to each other.

[0029] Preferably, each rotary inlet element is supported in at least two axial regions separate from each other, preferably corresponding to end regions of the rotary inlet element. According to an embodiment, each rotary element is supported at a first point by at least one rolling bearing, in particular a roller bearing, and at a second point by at least one further rolling bearing, in particular a ball bearing or a pair of adjacent ball bearings.

[0030] According to an embodiment, the actuator member has a cylindrical outer wall, facing the first rotary inlet element and connected to the first rotary inlet element by means of the first inlet thread, and a cylindrical inner wall, facing the second rotary inlet element and connected to the second rotary inlet element by means of the second inlet thread, the walls being separate from each other and positioned radially offset from each other.

[0031] Preferably, said inner and outer cylindrical walls are fixed to each other by an annular wall transversal, preferably perpendicular, to the main axis in such a way as to define a cavity between the outer and inner cylindrical walls. The cylindrical walls and the annular wall may be made integrally from a single piece or they may be obtained by joining together separate parts.

[0032] Preferably, in this situation the cavity houses at least partly at least one rolling bearing, for example ball bearing, intended for the connection between the actuator member and the transmission element, defining an axial connection but free rotation between the actuator member and the transmission element.

[0033] In this way, the actuator member is connected exclusively to the first and second rotary inlet elements by means of the first and second inlet threads respectively, and to the transmission element by means of at least one rolling bearing. In other words, the actuator member may be not directly mounted on the frame but be supported exclusively by the above-mentioned components.

[0034] In fact, in order to obtain a compact solution, the first and the second rotary inlet elements have axial lengths greater than the actuator member and are positioned in a nested configuration, that is to say, in a configuration such that one of the two rotary inlet elements has an axial dimension substantially included in the axial dimension of the other rotary inlet element. In this configuration, the actuator member (axially shorter) is inserted between the two rotary inlet elements and axially contained entirely in the axial dimensions of the two rotary inlet elements. This indirect support of the actuator member is therefore optimum for assembly in this configuration where the actuator element does not have cylindrical surfaces facing portions of the frame.

[0035] Preferably, the two rotary inlet elements have an axial end, opposite the rotary outlet element, facing a transversal wall of the frame defining an end wall (cover) (transversal / perpendicular to the main axis), at a distance from the transversal wall such as to define a hollow space.

[0036] Preferably, the first rotary inlet element is integral with a respective first gear wheel and the second rotary inlet element is integral with a respective second gear wheel, where the two gear wheels perform a function of mechanical transmission between each rotary inlet element and the respective motor.

[0037] According to an embodiment, the first rotary inlet element is coaxial with a respective first motor and integral with the rotor of said first motor, whilst the second rotary inlet element is coaxial with a respective second motor and integral with the rotor of said second motor. According to an embodiment presenting these coaxialities, the first rotary inlet element (innermost) is axially adjacent to the shaft of the first motor, in particular integral with it or forming part of it, whilst the second rotary inlet element (outermost) is nested inside the rotor of the second motor, preferably directly inserted in the rotor of the second motor and / or integral with it.

[0038] Preferably, the two gear wheels are coaxial and adjacent to each other. More preferably, the two gear wheels are positioned in the above-mentioned hollow space.

[0039] Preferably, each motor is connected to one of the respective gear wheels by an idle wheel, mounted on a fixed pin integral with the frame and positioned according to a respective axis of rotation positioned in an intermediate radial position between the main axis and the axis of rotation of the motor. The idle wheel is engaged with the respective gear wheel and with a pinion rotationally integral with the motor.

[0040] Preferably, each motor is a rotary servomotor.

[0041] Preferably, the above-mentioned hollow space has an annular shape which extends about a fixed central pin, integral with the frame and in particular with the above-mentioned end wall (cover), where one of the two rotary inlet elements, in particular the radially innermost one, is rotatably mounted on the central pin. Preferably, each inlet thread is made by recirculating ball screw.

[0042] Preferably, the base thread is made by recirculating ball screw.

[0043] Preferably, moreover, the linear guide positioned for connecting between the transmission element and the rotary outlet element is also formed by recirculating ball screw.

[0044] Preferably, the first and second inlet threads have a smaller pitch than the base thread. The pitch of the first and second inlet threads 7a, 7b is preferably between 1 and 30 mm.

[0045] Preferably, the first and second inlet threads have a “short” pitch whilst the base thread has a “long” pitch. The long pitch is preferably between 50 and 3000 mm. These pitch values can be increased in other applications outside the aerospace field.

[0046] Preferably, the first and the second inlet threads have identical pitch values. This is preferably provided in the case of inlet threads having opposite thread directions.

[0047] According to an embodiment, the first and second inlet threads can have different pitch values. This is preferably provided in the case of inlet threads with the same thread direction. Preferably, each motor or the respective rotation shaft is associated with a braking device for locking the rotation of the motor. In this way, the braking action exerts a locking action on the rotary inlet element associated with the motor in such a way that the respective inlet thread is stationary like a fixed thread. This brings about a possible operating condition of the actuator, which can be operated in a similar fashion to a traditional double-thread actuator (short pitch and long pitch). The motor braked is therefore like an electro-mechanical redundancy, which increases the overall reliability of the actuator.

[0048] By unlocking both motors, on the other hand, it is possible, by individually setting the speed of rotation of the two motors, to obtain different speeds of rotation and / or translation for the actuator member, which results in different values of angular speed and / or output torque.

[0049] In a variant embodiment, the invention may also be performed by means of a mechanical transmission wherein the two motors are absent and wherein they are replaced by respective power sockets (inlet shafts) which can be engaged by respective external motors and in particular protruding from the frame, for example axially protruding from the above-mentioned end wall (cover). In this configuration the actuator adopts more precisely the structure of a mechanical transmission which can be coupled to respective motors by means of corresponding power couplings, for example splined receiving shafts or seats.

[0050] Alternatively, according to a further variant embodiment, the invention may also be performed by means of a mechanical transmission or an electro-mechanical actuator wherein the actuator member, equipped with movement with a rotary and / or translational component, is directly connected to the rotary outlet element by a linear guide parallel to the main axis. In that case, preferably, the movement unit comprises the above-mentioned rotary inlet elements, each connected to its respective motor.

[0051] Moreover, the invention may also be performed using a system for moving an undercarriage in an aircraft, in particular an aeroplane or a helicopter, comprising an actuator according to the invention mounted and configured for making a movement for extracting and inserting the undercarriage by rotating the undercarriage about an axis of rotation.

[0052] Moreover, the invention may also be performed using a system for adjusting the flight surfaces of an aircraft, in particular flaps, comprising an actuator according to the invention mounted and configured for rotating one or more flight surfaces (flaps) about an axis of rotation.

[0053] Moreover, the invention may also be performed through a system for rotating a propulsion system in an aircraft, in particular an aeroplane or a helicopter, comprising an actuator according to the invention mounted and configured for making a rotational movement of a propulsion system of the aircraft about an axis of rotation.

[0054] Further features and advantages of the present invention are more apparent in the illustrative and therefore non-limiting description of an embodiment of a rotary electro-mechanical actuator according to the invention.

[0055] This description is set out below with reference to the accompanying drawings which are provided solely for illustrative and therefore non-limiting purposes, in which:

[0056] Figure 1 shows a first longitudinal cross section, in accordance with a first section plane, of an actuator according to the present invention;

[0057] Figure 1A is an enlargement of a part of the cross section of Figure 1;

[0058] Figure 2 shows a second longitudinal cross section of the actuator of Figure 1, according to a second section plane perpendicular to the first section plane;

[0059] Figure 2A shows an enlargement of a part of the cross section of Figure 2.

[0060] With reference to the accompanying drawings, the numeral 1 denotes in its entirety a linear electro-mechanical actuator according to the invention.

[0061] The actuator 1 comprises a containment frame 2, preferably box-shaped defining an inner space, a movement unit 3, in particular motor-driven, positioned in the containment space.

[0062] The movement unit 3 comprises a first motor 4 and a second motor 5, positioned with the relative axes of rotation "Yl", "Y2" parallel to each other and preferably housed in the containment space, in particular in a dedicated compartment or in respective dedicated compartments. Preferably, the above-mentioned motors 4, 5 are rotary motors, more preferably servomotors and even more preferably brushless servomotors.

[0063] Each motor 4, 5 comprises a respective shaft 4a, 5a rotatable about the respective axis of rotation “Yl”, “Y2”.

[0064] The above-mentioned axes of rotation “Yl”, “Y2” are also parallel to a main axis “X” of the actuator about which is rotatably mounted a rotary outlet element 6, defining the power outlet of the actuator and preferably having a portion protruding from the frame 2. The above-mentioned axes of rotation “Yl”, “Y2” are positioned in respective positions spaced from the main axis “X” and angularly spaced from each other, in particular by an angle equal to 90° in the embodiment illustrated (but this angle could be different, for example 180°; in this case the motors would be opposite each other relative to the main axis “X”).

[0065] The movement unit 3 also comprises a gear transmission which, in the embodiment illustrated, comprises for each motor 4 a respective pinion 4b, 5b, keyed on the respective shaft 4a, 5a or made in one piece with it, an idle wheel 4c, 5c (optional) meshing with the pinion 4b, 5b and a gear wheel 4d, 5d meshing with the respective idle wheel 4c, 5c. The two gear wheels 4d, 5d are coaxial with each other and rotatable about the main axis “X”. Moreover, preferably, the two gear wheels 4d, 5d are axially side by side and directly adjacent to each other.

[0066] The movement unit 3 also comprises a first rotary inlet element 4e and a second rotary inlet element 5e coaxial to and rotatable about the main axis “X”. The first rotary inlet element 4e is rotationally connected to the first gear wheel 4a whilst the second rotary inlet element 5e is rotationally connected to the second gear wheel 5 a.

[0067] In this configuration, each motor 4, 5 rotates the respective rotary inlet element 4e, 5e about the main axis “X”.

[0068] Preferably, the motors 4, 5 are independent of each other and / or independently controllable.

[0069] Preferably, moreover, each rotary inlet element 4e, 5e is supported in at least two axial regions separate from each other, preferably corresponding to end regions of the rotary inlet element 4e, 5e. According to the embodiment illustrated, each rotary inlet element 4e, 5e is supported at a first point by at least one rolling bearing 4f, 5f, in particular a roller bearing, and at a second point by at least one further rolling bearing 4g, 5g in particular a ball bearing or a pair of adjacent ball bearings.

[0070] According to the invention, the actuator 1 also comprises an actuator member 7, moved by the movement unit 3 and positioned coaxially to the above-mentioned main axis “X”.

[0071] The actuator member 7, which extends about the main axis, is configured to adopt a first component of rotary movement about the main axis “X” and a second component of axial movement along the main axis “X”.

[0072] The actuator member 7 is connected to the first rotary inlet element 4e and to the second rotary inlet element 5e, respectively, by a first inlet thread 7a and a second inlet thread 7b.

[0073] Since each rotary inlet element 4e, 5e is rotated by a respective motor 4, 5, the two rotary inlet elements 4e, 5e can be selectively rotated and driven independently. It follows that, by varying the speed of rotation of the motors 4, 5 and therefore of a rotary inlet element or both the rotary inlet elements 4e, 5e, the movement of the actuator member 7 is consequently varied, and in particular the distribution of the rotary component and of the translational component is varied. It is in fact possible to cancel the translational component, or cancel the rotary component. Obviously, continuous adjustment of the motors 4, 5 allows the reaching of intermediate movement conditions of the actuator member 7, with the balance of the rotary component and the translational component variable between zero value and a corresponding maximum value.

[0074] The two inlet threads 7a, 7b preferably have the same pitch value (but they might also have different pitch values).

[0075] In this situation, the two inlet threads 7a, 7b have opposite thread directions.

[0076] More specifically, with the same pitch value and opposite directions it is possible to obtain that with the same speed of rotation of the motors 4, 5, it is possible to obtain the cancellation of the rotary movement component of the actuator member 7 or the translational movement component of the actuator member 7 depending on whether the motors 4, 5 rotate in the same or opposite directions. All the other intermediate conditions of different speeds between the two motors 4, 5 lead to a roto-translational movement of the actuator member 7, with the balance between the rotary component and the translational component varying in relation to the specific ratio between the speeds of rotation of the motors 4, 5.

[0077] Preferably, the first inlet thread 7a and the second inlet thread 7b are positioned on respective separate zones of the actuator member 7.

[0078] According to an embodiment, the first inlet thread and the second inlet thread 7a, 7b are positioned on surfaces opposite each other, for example on an inner cylindrical surface and on an outer cylindrical surface.

[0079] In this situation, the actuator member 7 has a central hole, for example made by a tubular shape, and the first rotary inlet element 4e is inserted in the hole whilst the second rotary inlet element 5e is positioned outside the actuator member.

[0080] The first inlet thread and the second inlet thread 7a, 7b are positioned axially superposed or partly superposed, in other words they are at least partly nested one inside the other.

[0081] Preferably, the two rotary inlet elements 4e, 5e have an axial end, opposite the rotary outlet element 6, facing a transversal wall 2a of the frame 2 which defines an end wall or cover of the frame 2, which is positioned perpendicularly to the main axis “X”. That axial end of the rotary inlet elements 4e, 5e is positioned at a distance from the transversal wall 2a such as to define a hollow space “G”.

[0082] More preferably, the two gear wheels 4d, 5d are positioned in the above- mentioned hollow space “G”.

[0083] Even more preferably, the hollow space ‘G’ has an annular shape, and in particular extends about a fixed central pin 2b2, integral with the frame 2 and in particular with the above-mentioned transversal wall 2a, where on the central pin 2b there is rotatably mounted (by means of a roller bearing 4f) the first rotary inlet element 4e, radially innermost.

[0084] The actuator 1 also comprises a transmission element 8, connected to the frame 2 by a base thread 9 in such a way as to adopt a roto-translational movement about the main axis “X”.

[0085] The transmission element 8 is also connected to the actuator member 7 in an axially integral fashion to it, that is to say, in such a way that they cannot present reciprocal axial sliding. Preferably, this is obtained by connecting together the transmission element 8 and the actuator member 7 by means of a circular guide and / or one or more rolling bearings 10 (rollers, balls). In that way, the rotary component of the movement of the actuator member 7 is absorbed by the circular guide and / or by the bearings 10 and not transmitted to the transmission element 8, which, on the other hand, receives the entire component of axial movement of the actuator member 7.

[0086] In turn, the transmission element 8, being connected to the frame 2 by the base thread 9, due to the axial thrust exerted by the actuator member 7 is constrained to follow a roto-translational movement, the rotary component of which about the main axis “X” is independent from the rotary component of the actuator member 7 due to the above-mentioned circular guide and / or the above-mentioned bearings 10.

[0087] With reference to the rotary outlet element 6, it is rotatable about the main axis “X” and is connected to the transmission element 8 in such a way as to have a rotational movement integral (that is to say, synchronous and integrated) with the rotary component of the movement of the transmission element 8.

[0088] In other words, the rotary component (and only the rotary component) of the roto- translational movement of the transmission element 8 is therefore transmitted to the rotary outlet element 6. This is preferably obtained by connecting the transmission element 8 to the rotary outlet element 6 in a fashion that is rotationally combined with it, for example by means of a linear guide 11 (grooved or recirculating ball screw). In that way, the axial component of the roto- translational movement of the transmission element 8 is absorbed by the linear guide 11 and not transmitted to the rotary outlet element 6, which, on the other hand, receives the entire component of rotary movement of the transmission element 8. The rotary outlet element 6 is mounted rotatably on the frame 2 by means of one or more rolling supports, in particular one or more bearings 12.

[0089] Preferably, moreover, the first rotary inlet element 4e, radially innermost, is connected to the rotary outlet element 6 by one of its own bearings 4g. The bearing 4g therefore operates in a “suspended” fashion relative to the frame 2.

[0090] The actuator 1 according to the invention also has some structural measures which optimize its compactness and robustness.

[0091] Preferably, the actuator member 7 has an inner cylindrical wall 7c, facing the first rotary inlet element 4e and connected to it by the first inlet thread 7a, and an outer cylindrical wall 7d, facing the second rotary inlet element 5e and connected to it by the second inlet thread 7b, the walls 7c, 7c being separate from each other and positioned radially offset from each other.

[0092] Preferably, the above-mentioned inner and outer cylindrical walls 7c, 7d are fixed to each other by an annular wall 7e perpendicular to the main axis “X” in such a way as to define a cavity between the inner 7c and outer 7d cylindrical walls. The cylindrical walls 7c, 7d and the annular wall 7e may be made integrally from a single piece or they may be obtained by joining together separate parts.

[0093] Preferably, in this situation the cavity houses at least partly the at least one rolling bearing 10, for example ball bearing, and / or the circular guide, designed for the connection between the actuator member 7 and the transmission element 8.

[0094] In this way, the actuator member 7 is connected exclusively to the first and the second rotary inlet elements 4e, 5e, respectively by means of the first and second inlet threads 7a, 7b, and to the transmission element 8, by means of at least one rolling bearing 10. In other words, the actuator member 7 may be not directly mounted on the frame 2 but be supported exclusively by the above-mentioned components (with a “suspended” assembly).

[0095] In order to obtain a compact solution, the first and the second rotary inlet elements 4e, 5e preferably have axial lengths greater than the actuator member 7 and are positioned in a nested configuration, that is to say, in a configuration such that one of the two rotary inlet elements 4e, 5e has an axial dimension substantially included in the axial dimension of the other rotary inlet element 4e, 5e. In this configuration, the actuator member 7 (axially shorter) is inserted between the two rotary inlet elements 4e, 5e and axially contained entirely in their dimensions. This indirect support of the actuator member 7 is therefore optimum for assembly in this configuration where the actuator member 7 does not have cylindrical surfaces facing portions of the frame 2.

[0096] Preferably, each inlet thread 7a, 7b is made by recirculating ball screw.

[0097] Preferably, the base thread 9 is made by recirculating ball screw.

[0098] Preferably, moreover, the linear guide 11 positioned for connecting between the transmission element 8 and the rotary outlet element 6 is also formed by recirculating ball screw.

[0099] Preferably, the first and the second inlet threads 7a, 7b have a smaller pitch than the base thread 9. The pitch of the first and the second inlet threads 7a, 7b is preferably between 1 and 10 mm.

[0100] Preferably, the first and second inlet threads 7a, 7b have a “short” pitch whilst the base thread 9 has a “long” pitch. The long spacing is preferably between 5 and 3000 mm (these pitch values, both short and long, may be increased in applications outside the aerospace field, in particular for applications with high loads).

[0101] Preferably, also, each motor 4, 5 or the respective rotation shaft 4a, 5a is associated with a braking device (not illustrated) for locking the rotation of the motor 4, 5. In this way, the braking action performs a locking action on the respective rotary inlet element 4e, 5e in such a way that the respective inlet thread 7a, 7b is stationary like a fixed thread. This brings about a possible operating condition of the actuator, which can be operated in a similar fashion to a traditional double-thread actuator (short pitch and long pitch). The motor braked is therefore like an electro-mechanical redundancy, which increases the overall reliability of the actuator.

[0102] By unlocking both motors, on the other hand, it is possible, by individually setting the rotation speeds of the two motors, to obtain different rotation and / or translation speeds for the actuator member, which achieves different angular speed values at the outlet. The present invention achieves the preset aims, overcoming the drawbacks of the prior art.

[0103] The actuator is in effect extremely versatile, allowing a wide selection of transmission ratios simply by varying the speed of rotation of the two motors (robust and immediate adjustment). Moreover, the particular embodiment allows mechanical redundancy which increases the reliability.

Claims

CLAIMS1.A rotary electro-mechanical actuator, comprising:- a containment frame (2);- a movement unit (3);- an actuator member (7), moved by said movement unit (3) and configured to adopt a first component of rotary movement about a main axis (X) and a second component of axial movement along said main axis (X), said first and second components being individually adjustable between a zero speed value and a maximum speed value and preferably adjustable independently of each other;- a transmission element (8), connected to the frame (2) by a base thread (9) in such a way as to adopt a roto-translational movement about the main axis (X) and also connected to said actuator member (7) in an axially integral fashion with said actuator member (7);- a rotary outlet element (6) rotatable about said main axis (X) and connected to the transmission element (8) in such a way as to have a rotational movement integral with the rotary component of the movement of the transmission element (8).

2. The actuator according to claim 1, wherein said movement unit (3) comprises a first and a second motor (4, 5), which can be controlled independently from each other.

3. The actuator according to claim 2, wherein said motors (4, 5) have respective axes of rotation (Yl, Y2) parallel to the main axis (X) and angularly spaced from each other about the main axis (X), preferably at a same distance from the main axis (X).

4. The actuator according to claim 2 or 3, wherein said movement unit (3) comprises a first rotary inlet element (4e) and a second rotary inlet element (5e), engaged with the actuator member (7), respectively, by a first inlet thread (7a) anda second inlet thread (7b), preferably positioned on respective separate zones of the actuator member (7), and wherein said first motor (4) is connected to the first rotary inlet element (4e) whilst the second motor (5) is connected to the second rotary inlet element (5e).

5. The actuator according to claim 4, wherein the actuator member (7) has a central hole and wherein the first rotary inlet element (4e) is inserted in said hole and the second rotary inlet element (5e) is positioned outside the actuator member(7).

6. The actuator according to claim 5, wherein said actuator member (7) has an inner cylindrical wall (7c), facing the first rotary inlet element (4e) and connected to the first rotary inlet element (4e) by the first inlet thread (7a), and an outer cylindrical wall (7d), facing the second rotary inlet element (5e) and connected to the second rotary inlet element (5e) by the second inlet thread (7b), said inner and outer cylindrical walls (7c, 7f) being fixed to each other by an annular wall (7e) transversal, preferably perpendicular, to the main axis (X) in such a way as to define a cavity between the outer and inner cylindrical walls (7c, 7d).

7. The actuator according to any one of the preceding claims, wherein the actuator member (7) and the transmission element (8) are connected to each other by at least one roller bearing (10), preferably ball bearing, defining an axial connection but a free rotation between the actuator member (7) and the transmission element(8).

8. The actuator according to claim 6 or 7, wherein said at least one roller bearing (10) is at least partly inserted in said cavity.

9. The actuator according to claim 7 or 8, wherein the actuator member (7) is connected exclusively to the first and the second rotary inlet elements (4e, 5e), respectively by means of said first and second inlet threads (7a, 7b), and to thetransmission element (8), by means of said at least one roller bearing (10).

10. The actuator according to any one of claims 4 to 9, wherein the first rotary inlet element (4e) is integral with a respective first gear wheel (4d) and the second rotary inlet element (5e) is integral with a respective second gear wheel (5d), and wherein the two gear wheels (4d, 5d) are coaxial and adjacent to each other.

11. The actuator according to any one of claims 4 to 10, wherein the first and the second inlet threads (7a, 7b) have a smaller pitch than the base thread (9).

12. The actuator according to claim 11, wherein the first and the second inlet threads (7a, 7b) have identical pitch values.

13. The actuator according to any one of the preceding claims, wherein the rotary outlet element (6) is connected to the transmission element (8) by a linear guide (11) parallel to the main axis (X), preferably by recirculating ball screw.

14. The actuator according to any one of claims 2 to 13, wherein each motor (4, 5) or the respective rotation shaft (4a, 4b) is associated with a braking device for locking the rotation of said motor (4, 5).

15. A method for operating the actuator according to any one of the preceding claims, comprising the step of actuating at least one of said motors (4, 5) for setting the actuator member (7) in translational or roto-translational movement such that it moves the connecting element (8) in roto-translation and, consequently, rotates the rotary outlet element (6).

16. The method according to claim 15, also comprising the step of varying the speed of rotation of at least one of said motors (4, 5) for varying the speed of rotation of the rotary outlet element (6).

17. The method according to claim 15 or 16, further comprising a step of stopping one of said motors (4, 5) from rotating when said motor (4, 5) is not in operation.

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