EP4689441A1 - Mechanical transmission - Google Patents

Abstract

Described is a mechanical transmission (T) comprising a first rotary element (200) rotatable about a main axis (X) and a second rotary element (300) rotatable about the main axis (X). The mechanical transmission (T) also comprises a connecting element (400) coupled to the first rotary element (200) by a short-pitch threaded connection (50) and to a containment frame (100) by means of a long- pitch threaded connection (60). The long -pitch threaded connection (60) is located on two angular zones angularly opposite each other relative to the main axis (X) and aligned along a first direction (A) perpendicular to the main axis (X). The two angular zones are separated from each other by zones without the long-pitch threaded connection (60) in such a way that, in a plane (T) perpendicular to the main axis (X), the mechanical transmission (T) has a maximum dimension, along a second direction (B) perpendicular to the first direction (A), which is less than the maximum dimension along the first direction (A).

Description

MECHANICAL TRANSMISSION

This invention relates to a rotary mechanical transmission and is used in particular in the aeronautical field in particular in the control of the surfaces of an aircraft such as, for example, doors or flaps.

Rotary electro-mechanical actuators are known in the prior art comprising an electric motor and a transmission consisting, for example, of a screw and a lead nut or a series of gear wheels designed to vary the angular speed of a transmission output element.

Disadvantageously, these transmission systems have some drawbacks in terms of size and constructional complexity.

In general, the transmission systems known in the sector comprise rotary couplings, generally based on recirculating ball screws, which have radial dimensions which cannot be reduced as required and which therefore result in, in the case of one or more preset design dimensions (for example due to the place of installation), the need to reduce the dimensions of the entire transmission and therefore of the transmittable power. More specifically, the recirculating ball screws are, by their nature, radially bulky due to the presence of the two forward and return branches of the balls.

Moreover, the size of the balls is directly linked to the transmissible torque, since for high loads the balls must have a minimum diameter which cannot be reduced. Moreover, for high torques the recirculating ball screws are positioned in outer zones of the transmission, where the radius is greater, but this has a negative effect on the level of miniaturisation of the transmission.

The technical purpose of the invention is therefore to provide a mechanical transmission which is able to overcome the drawbacks of the prior art.

The aim of the invention is therefore to provide a mechanical transmission which allows the overall size of the entire transmission to be reduced making it suitable for use in aeronautical applications, and in particular in reduced spaces. A further aim of this invention is also to provide a mechanical transmission which has a high transmission torque.

The technical purpose indicated and the aims specified are substantially achieved by a mechanical transmission comprising the technical features described in one or more of the accompanying claims.

In particular, the technical purpose and the aims specified are achieved by a mechanical transmission comprising a containment structure, that is to say, a casing, a first rotary element connected or connectable to a drive unit, for example an electric motor, to define a mechanical power input unit and rotatable about a main axis.

The mechanical transmission “T” also comprises a second rotary element rotatable about the main axis and defining a power output element.

The mechanical transmission also comprises a connecting element, which is roto- translational, extending along the main axis and coupled to the first rotary element by a short-pitch threaded connection and to the containment frame by means of a long-pitch threaded connection in such a way that the connecting element is configured to roto-translate about the main axis.

The long-pitch threaded connection is positioned between an outer surface of the connecting element and an inner surface of the containment frame and comprises a recirculating ball screw.

Advantageously, the long-pitch threaded connection is formed by its sections located on two angular zones angularly opposite each other relative to the main axis and preferably aligned along a first direction perpendicular to the main axis. The two angular zones are separated from each other by zones without the long- pitch threaded connection in such a way that, in a plane perpendicular to the main axis, the mechanical transmission has a maximum dimension, along a second direction perpendicular to the first direction, which is less than the maximum dimension along the first direction.

The connecting element is also coupled to the second rotary element by a linear guide parallel to the main axis. Preferably, the linear guide is also made by recirculating ball screws and is formed by its sections located on two angular zones angularly opposite each other relative to the main axis and preferably aligned along the same first direction perpendicular to the main axis.

The two angular zones of the linear guide are separated from each other by zones without the linear guide, therefore of the respective balls, in such a way that, in a plane perpendicular to the main axis, the mechanical transmission has a maximum dimension, along a second direction perpendicular to the first direction, less than the maximum dimension along the first direction.

According to an aspect of the invention, the embodiment in two sections which are angularly distinct and opposite each other is provided only for the linear guide and not for the long-pitch threaded connection.

Advantageously, the above-mentioned arrangement makes the mechanical transmission according to the invention particularly suitable for being installed on wing flaps of an aircraft or a node door of an aircraft. For example, in an aircraft wing the thickness of the wing is very limited and the installation of the transmission may occur with the alignment of the second direction to the thickness of the wing.

Further features and advantages of the invention are more apparent in the nonlimiting description which follows of a non-exclusive embodiment of a mechanical transmission according to the invention.

The description is set out below with reference to the accompanying drawings which are provided solely for purposes of illustration without restricting the scope of the invention and in which:

Figure 1 shows a perspective view of the mechanical transmission according to the invention;

Figure 2 shows a perspective view of the mechanical transmission of Figure 1 from which a containment frame has been partly removed;

Figures 3A and 3B show respective cross section views of the mechanical transmission of Figure 1;

Figure 4 shows a cross section of the mechanical transmission of Figure 1 along a main axis; Figure 5 shows a further cross section view of the mechanical transmission of Figure 1;

Figure 6 shows a perspective view of a connecting element of the mechanical transmission according to the invention;

Figures 7A and 7B show perspective views of a closing plate provided with recesses for a recirculating ball screw.

With reference to the accompanying drawings, Figure 1 illustrates a rotary actuator, in particular an actuator which transforms a rotary motion having a first angular speed and a first torque entering a rotary motion having a second angular speed less than the first and a greater torque.

The rotary actuator “R” basically comprises an electric motor “M” and a mechanical transmission “T” for achieving a very high reduction ratio.

The mechanical transmission “T” comprises a containment frame 100 and a rotary element 200 connected or connectable to a drive unit to define a mechanical power input unit.

The first rotary element 200 is rotatable about a main axis “X” and is axially locked, therefore, provided only with rotational movement.

The mechanical transmission “T” also comprises a second rotary element 300 which is also rotatable about the main axis “X” and defining a power output element.

As shown in Figures 2 and 4, the mechanical transmission “T” also comprises a connecting element 400 extending along the main axis “X” and positioned for connecting between the first and the second rotary elements 200, 300.

The connecting element 400 is configured for transmitting the motion from the first rotary element 200 to the second rotary element 300, as explained below.

Preferably, the connecting element 400 is made in the form of a hollow body (Figure 6).

The connecting element 400 is coupled to the first rotary element 200 by a shortpitch threaded connection 50, preferably a recirculating ball screw connection.

Preferably, the short-pitch threaded connection 50 is positioned between an outer surface of the first rotary element 200 and an inner surface of the connecting element 400 (Figure 4).

In effect, preferably, the first rotary element 200 comprises a screw inserted inside the connecting element 400.

As shown in Figure 4, the connecting element 400 is also coupled to the containment frame 100 by means of a long-pitch threaded connection 60 in such a way that the connecting element 400 is configured to roto-translate about the main axis “X” at a speed determined as a result of the speed of rotation of the first rotary element 200 and the pitch of the two threaded connections 50, 60.

In particular, the long-pitch threaded connection 60 is positioned between an outer surface of the connecting element 400 and an inner surface of the containment frame 100 and comprises a recirculating ball screw 60a.

According to an aspect of the invention, the long-pitch threaded connection 60 is at least partly superposed, preferably partly superposed, on the short-pitch threaded connection 50.

As shown in Figures 3B and 4, the long-pitch threaded connection 60 is formed by its angular sections located on two angular zones angularly opposite each other relative to the main axis “X” and preferably aligned along a first direction “A” perpendicular to the main axis “X”.

The two angular zones are separated from each other by zones without the long- pitch threaded connection 60. In other words, the angular zones are alternated with the zones without the long-pitch threaded connection 60.

In this situation, in a plane perpendicular to the main axis "X", the mechanical transmission "T" may have a maximum dimension, along a second direction "B" perpendicular to the first direction "A", which is less than the maximum dimension along the first direction "A" (see sections of Figure 4 and Figure 5).

In other words, the positioning of the two angular zones makes it possible to obtain a mechanical transmission “T” having one of the two dimensions, measured on the plane v, which is considerably less than the other. More specifically, according to the embodiment illustrated, the larger dimension is that along the first direction “A” whilst the smaller dimension is that along the second direction “B”. In effect, as shown in Figure 1, the mechanical transmission “T” is “elongate” along the first direction “A” whilst it is “flattened” along the second direction “B”.

The fact that the accompanying drawings show rolling tracks (on the outer surface of the connecting element 400, Figure 6) extending apparently beyond the angular dimensions of the recirculating ball screws is due to the fact that, whilst the balls remain confined in a fixed and deliberately limited angular position for reducing the dimensions of the actuator, in order to obtain a rotation of the connecting element 400 about the main axis “X” it is necessary that the tracks extend as a result of this rotation.

Preferably, as shown by way of example in Figures 7 A and 7B, which shows a plate 60b for closing the recirculating ball screw of the long-pitch threaded connection 60 (provided, for each angular section, with three slots for inversion of the balls), each of the angular zones of the long-pitch threaded connection 60 has an angular extension less than 140°.

Preferably, the angular extension “a” of each above-mentioned angular zone is between 90° (±45°) and 150° (±75°) and more preferably between 100° (±50°) and 130° (±65°). The angle "a" is expressed in a two-way fashion since the closing plate 60b is one of the two closing plates, the other being symmetrical on the opposite side to give a certain degree of screwing of the long-pitch recirculating ball screw along the connecting element 400.

As shown in Figures 2 and in Figure 4, the connecting element 400 is coupled to the second rotary element 300 by a linear guide 70 parallel to the main axis “X”, preferably also of the recirculating ball type.

Again with reference to Figure 4, the connecting element 400 is supported without the use of bearings and is preferably supported only by the long and short-pitch threaded connections 50, 60 and by the above-mentioned linear guide 70. In this situation, the second rotary element 300 has a supporting portion 300c, preferably defining an end section of the second rotary element 300 and more in particular having a reduced diameter, coupled to the containment frame 100 by a rolling bearing, preferably of the roller and/or ball type.

In accordance with the embodiment illustrated, the second rotary element 300 also has a coupling portion 300b, in particular tubular or cup-shaped, positioned outside the connecting element 400 and connected to the connecting element 400 by means of the linear guide 70.

Preferably, the linear guide 70 is formed by two angular sections located on two angular zones separate from each other and preferably angularly opposite each other relative to the main axis “X”.

As shown for example in Figure 4, the angular zones of the linear guide 70 are aligned with each other along the above-mentioned first direction “A”.

It should be noted that the fact that the linear guide 70 is located in two angular zones separate from each other and angularly opposite relative to the main axis “X” can be protected independently from the shape of separate angular zones provided for the long-pitch connection 60.

In accordance with the embodiment illustrated, the linear guide 70 is defined by one or more recirculating ball connections and is positioned between an inner surface of the second rotary element 300 and the outer surface of the connecting element 400. More in detail, in accordance with the embodiment illustrated, the second rotary element 300 comprises a pair of radial expansions 300a wherein the recirculating ball screws of the linear guide 70 are recirculated.

More specifically, the radial expansions 300a extend mainly parallel to the first direction “A” in such a way as to contribute to keeping contained the dimensions of the mechanical transmission “T” along the second direction “B” (Figure 3A).

In this situation, the second rotary element 300 has a limited rotation about the main axis “X”, that is to say, the second rotary element 300 is not able to perform a complete revolution about the main axis “X”.

In more detail, the containment frame 100 has, in a cross-section transversal to the main axis “X” (that is, on the plane T), a shape such as to allow a maximum rotation of the second rotary element 300 of between ±20° and ±40°.

According to the embodiment illustrated in the accompanying drawings, in a transversal cross-section, the containment frame 100 has an elongate shape along the first direction “A”, in particular a pair of rectilinear stretches 100a (more generally first parallel walls) opposite each other relative to the main axis “X” and parallel to the first direction “A” and a pair of curved stretches 100b (more generally second walls), preferably following the profile of the radial expansions 300a, configured to join together the rectilinear stretches 100a. In this situation, the distance between the rectilinear stretches 100a is slightly greater than the diameter of the second rotary element 300, and in particular of its coupling portion 300b (Figure 3A).

Moreover, the amplitude of rotation of the second rotary element 300 is given by the distance between the two rectilinear stretches 100a (see, for example, Figures 3A and 3B) which, due to their shape, determine a limit to the movement of the two radial expansions 300a and therefore to the rotation of the second rotary element 300.

In this way, the second rotary element 300 can perform a limited rotation about the main axis "X", for example, to lift or lower the flaps of an aircraft.

In use, therefore, when the first rotary element 200 is rotated, the rotary motion is transmitted, by the short-pitch connection 50, to the connecting element 400 which is rotated about the main axis “X”. Thanks to the linear guide 70, the connecting element is, however, also constrained to translate along the main axis “X” and is in practice roto-translating. In this situation, the connecting element 400 transmits only the rotational motion to the second rotary element 300 which, thanks to the structural shape of the entire mechanical transmission “T”, may perform a limited rotation about the main axis “X”.

In order for the first rotary element 200 to be rotated, it is possible to connect the latter to an electric motor “M” (for example made by means of permanent magnets), as shown in Figure 4. In this situation, the mechanical transmission “T” may comprise a containment space “V”, integral or separate from the space where the rotary elements 200, 300 and the connecting element 400 are contained, suitable for installation of the electric motor “M” and positioned in a position spaced from the main axis “X”.

Preferably, the containment space “V” is spaced from the main axis “X” along the first direction “A”. This positioning, as shown, for example, in Figure 3, contributes to keeping contained the dimension of the mechanical transmission “T” along the second direction “B”. According to this solution, the motor “M” may be connected to the first rotary element 200 by one or more drive gears.

Alternatively, the motor may be coaxial with the first rotary element 200 and be integral with it or connected by means of a reversible power pick-up (for example, a grooved seat made at the end of the first rotary element 200 or on a further power input unit).

The invention also relates to a rotary actuator “R” comprising a mechanical transmission “T” in accordance with the above-mentioned description and an electric motor “M” connected to the first rotary element 200.

Preferably, the electric motor “M” has the relative axis of rotation parallel to the main axis “X” and spaced from the main axis “X” along the first direction “A”.

The above-mention rotary actuator “R” may be used, by way of a non-limiting example, for actuating wing flaps of an aircraft or a nose door of an aircraft by installation inside a wing or a nose door of said aircraft, in particular by means of a direct and coaxial assembly on a hinge for rotating, respectively, the flap or nose door.

The invention achieves the preset aims eliminating the drawbacks of the prior art. More specifically, the making of the long-pitch connection 60 and/or the linear guide by means of different angular sections and preferably radially opposite each other allows a mechanical transmission “T” to be obtained wherein, in cross section, a first dimension is considerably greater than a second dimension transversal to the first dimension in such a way that the mechanical transmission “T” designed to be inserted in particularly small seats typical of the aircraft sector. Moreover, the making of the recirculating ball screws of the long-pitch connection 60 and/or the linear guide on the outer surface of the connecting element forms an increased structural resistance of the actuator which can withstand very high torques, thanks to the diameter in which the recirculating ball screws are positioned.

Claims

1.A mechanical transmission (T) comprising:

- a containment frame (100);

- a first rotary element (200), connected or connectable to a drive unit to define a mechanical power input unit and rotatable about a main axis (X);

- a second rotary element (300) rotatable about said main axis (X) and defining a power output unit;

- a connecting element (400) extending along said main axis (X) and coupled to said first rotary element (200) by a short-pitch threaded connection (50) and to said containment frame (100) by a long-pitch threaded connection (60) in such a way that said connecting element (400) is configured to roto-translate about said main axis (X), said connecting element (400) being also coupled to said second rotary element (300) by a linear guide (70) parallel to said main axis (X); wherein said long-pitch threaded connection (60) is positioned between an outer surface (400a) of the connecting element (400) and an inner surface (100b) of the containment frame (100) and comprises a recirculating ball screw (60a), characterised in that said long-pitch threaded connection (60) is located on two angular zones angularly opposite each other relative to the main axis (X) and aligned along a first direction (A) perpendicular to the main axis (X), said two angular zones being separated from each other by zones without said long-pitch threaded connection (60) in such a way that, in a plane (T) perpendicular to said main axis (X), the mechanical transmission (T) has a maximum dimension, along a second direction (B) perpendicular to said first direction (A), less than the maximum dimension along said first direction (A).

2. The transmission according to claim 1, wherein each of said angular zones has an angular extension of between 90° and 150°, preferably between 110° and 130°.

3. The transmission according to claim 1 or 2, wherein said linear guide (70) is defined by one or more recirculating ball connections and is located on two angular zones separate from each other and angularly opposite relative to said main axis (X), and wherein said angular zones of the linear guide (70) are aligned with each other along said first direction (A).

4. The transmission according to claim 3, wherein said second rotary element (300) comprises a pair of radial expansions (300a) wherein the recirculating ball screws of the linear guide (70) are recirculated.

5. The transmission according to any one of the preceding claims, wherein said containment frame (100) has, in a cross-section transversal to the main axis (X), a shape such as to allow a maximum rotation of the second rotary element (300) of between ±20° and ±40°.

6. The transmission according to any one of the preceding claims, also comprising a containment space (V) suitable for installing an electric motor (M) and positioned in a position spaced from the main axis (X).

7. The transmission according to claim 6, wherein said containment space (V) is spaced from the main axis (X) along said first direction (A).

8. The transmission according to any one of the preceding claims, wherein said second rotary element (300) has a coupling portion (300b), in particular tubular or cup-shaped, positioned outside the connecting element (400) and connected to the connecting element (400) by means of said linear guide (70).

9. The transmission (T) according to any one of the preceding claims, wherein the first rotary element (200) comprises a screw inserted inside the connecting element (400).

10. The transmission (T) according to claim 10, wherein the long-pitch threaded connection (60) is at least partly superposed, preferably partly superposed, on the short-pitch threaded connection (50).

11. The transmission (T) according to any one of the preceding claims, wherein the connecting element (400) is supported without the use of bearings and is preferably supported only by means of said long-pitch and short-pitch threaded connections (60, 50) and by means of said linear guide (70).

12. The transmission (T) according to claim 11, wherein said second rotary element (300) has a supporting portion (300c), preferably defining an end section of the second rotary element (300) and more in particular having a reduced diameter, coupled to the containment frame (100) by a rolling bearing, preferably of the roller or ball type.

13. A rotary actuator (R), comprising a mechanical transmission (T) according to any one of the preceding claims, and an electric motor (M) connected to, or integral with, said first rotary element (200).

14. The rotary actuator (R) according to claim 13, wherein said electric motor (M) has an axis of rotation parallel to the main axis (X) and spaced from the main axis along said first direction (A).

15. Use of a rotary actuator (R) according to claim 13 or 14 for actuating wing flaps of an aircraft or a nose door of an aircraft by installation inside a wing or a nose door of said aircraft, in particular by means of a direct and coaxial assembly on a hinge for rotating, respectively, said flap or nose door.