FR3099971A1 - Magnetic screw-nut system - Google Patents

Abstract

The present invention relates to a magnetic screw-nut system comprising: - a nut (2) capable of rotating or translating about an axis (X); - a screw (1) able to interact magnetically with said nut (2) and to translate or rotate inside said nut (2) along said axis (X), an air gap (3) being formed between said screw (1) ) and said nut (2); said nut (2) carrying two helices (24, 25) made of magnetic material extending helically parallel to one another around said axis (X), said nut (2) carrying at least one magnet (21) ), placed at the outer periphery of said helices (24, 25), the north pole (N) of said magnet (21) being connected to one of said helices (24) and its south pole (S) being connected to the other said helices (25) such that said helices (24, 25) are respectively north and south polarized; said screw (1) carrying two helices (14, 15) made of magnetic material extending helically parallel to one another around said axis (X), said screw (1) carrying at least one magnet (11) ), placed at the inner periphery of said helices (14, 15), the north pole (N) of said lover (11) being connected to one of said helices (14) and its south pole (S) is connected to the other said helices (15) such that said helices (14, 15) are respectively north and south polarized; the pitch of said propellers (24, 25) of said nut (2) being substantially equal to the pitch of said propellers (14, 15) of said screw (1).

Description

Magnetic screw-nut system

1. Field of the invention

The field of the invention is that of the design and production of screw and nut systems interacting by magnetic connection without mechanical contact, in particular to allow the transformation of a rotary movement into a linear (rectilinear) movement, or vice versa.

2. Prior Art

Magnetic screw-nut techniques and devices without mechanical contacts, also called magnetic screw-nut systems, make it possible to transform a rotary movement into a linear movement and, conversely, a linear movement into a rotary movement. These devices consist of a nut and a screw which interact magnetically, and thus allow the conversion of movement and the transmission of forces. These magnetic screws and nuts avoid mechanical contact, such as encountered for example in ball screws or satellite roller screws, and thus:

- free themselves more easily from thermal expansion,

- are less noisy,

- do not require lubrication,

- avoid loss of performance by friction,

- are less sensitive to the environment (dust, etc.).

A magnetic screw and nut system conventionally comprises a nut inside which a screw is housed.

According to a first technique such as that described in document US-A1-2004/0041474, the screw carries a succession of permanent magnets arranged to essentially form a helix, the successive magnets having reversed polarities. The nut carries a succession of electromagnets arranged to essentially form a helix, the successive magnets having reversed polarities.

The pitch of the screw and that of the nut, i.e. the pitch of their helices, are identical.

The supply of the electromagnets of the nut, which is stationary except in rotation, causes the rotation of the screw and its translation inside the nut without mechanical contact.

This technique, which makes it possible to constitute a linear motor to generate a combined movement of rotation and translation of an element along the same axis, has some drawbacks.

In particular, the propellers, which are formed by the juxtaposition of a plurality of magnets, are difficult and expensive to produce.

In addition, the helices thus formed by the juxtaposition of a plurality of magnets actually constitute pseudo-helices having discontinuous profiles and not “perfect” helices, in particular taking into account the geometric tolerances of each magnet and their precision of assembly. This induces negative impacts both in terms of the precision of the movement generated at the level of the screw, and in terms of the forces likely to be transmitted to the screw.

According to a second technique, the propeller carried by the screw no longer consists of a juxtaposition of magnets. It is instead formed by means of a magnet arranged helically on the surface of the screw, also called a helical magnet. The nut carries either a helix formed by means of a magnet arranged helically on the surface of the screw as for the screw, or else formed by the juxtaposition of a plurality of magnets with reversed polarity as in the first technique mentioned above.

In this configuration, the rotational drive of the nut generates by magnetic interaction without mechanical contact a displacement in translation of the screw inside the nut, the screw being locked in rotation.

The implementation of helical magnets at the level of the screw and the nut makes it possible to improve the precision of the displacement of the screw inside the nut.

However, helical magnets are difficult to produce and therefore particularly expensive. The cost of these magnets means that this technique is limited in terms of ability to transmit significant forces to the screw.

The two techniques of the prior art discussed above can therefore be further improved insofar as they lack precision in the movement of rotation and translation, and make it possible to generate only limited forces from the transformation of a rotational motion into linear translational motion, or vice versa.

3. Objects of the invention

The aim of the invention is in particular to provide a solution to one or more of these various problems.

In particular, according to at least one embodiment, an objective of the invention is to provide a magnetic screw-nut system which is simpler to manufacture than the systems according to the prior art.

In particular, the invention aims, according to at least one embodiment, to provide such a system with better precision in terms of controlling the relative movement of the screw and the nut.

Another object of the invention is, according to at least one embodiment, to provide such a system which can allow the transmission of a significant force to that of the screw or the nut which is driven in motion.

Another object of the invention is, according to at least one embodiment, to provide such a system which is modular in terms of capacity to transmit forces, that is to say of which the value of the effort transmitted.

Another object of the invention is, according to at least one embodiment, to provide a magnetic screw-nut system which is economical to manufacture.

4. Presentation of the invention

The invention relates to a magnetic screw-nut system comprising:

- a nut capable of rotating or translating around an axis;

- a screw capable of magnetically interacting with said nut and of translating or rotating inside said nut along said axis, an air gap being provided between said screw and said nut;

said nut carrying two helices made of magnetic material extending parallel to each other in a helical manner around said axis, said nut carrying at least one magnet, placed at the outer periphery of said helices, the north pole of said magnet being connected to one of said helices and its south pole being connected to the other of said helices in such a way that said helices are respectively north and south polarized;

said screw carrying two helices made of magnetic material extending parallel to each other in a helical manner around said axis, said screw carrying at least one magnet, placed at the inner periphery of said helices, the north pole of said lover being connected to one of said helices and its south pole is connected to the other of said helices in such a way that said helices are respectively north and south polarized;

the pitch of said helices of said nut being substantially equal to the pitch of said helices of said screw.

Thus, the invention relates to a magnetic screw-nut system whose helices are not made up of a juxtaposition of magnets or helical magnets.

On the contrary, according to the principle of the invention, the nut and the screw each comprise two helices, one connected to the north pole of a magnet of simple shape and the other connected to the south pole of a magnet of simple.

A magnetic interaction between the nut and the screw is thus obtained in a simple and economical way, the propellers being simple and economical to manufacture, just like the magnets which can have any shape.

The continuous-shaped helices make it possible to ensure good continuity of the relative movement of the screw and the nut and thus, to guarantee good precision and good transmission of forces.

It is also possible to simply change the force transmission capacities by modifying the parameters or properties, in particular the dimensional properties of the magnets, insofar as the magnets are of simple shape. The force transmission capacity could also be modified by changing other intrinsic properties of the magnets such as the material of which they are made, their remanence, etc.

According to one possible characteristic, said nut and said screw comprise a plurality of magnets in an even number, the polarities of the successive magnets being reversed.

According to a possible characteristic, said magnets are distributed essentially uniformly around said axis.

According to a possible characteristic, the numbers of magnets of said screw and of said nut are equal or different.

According to one possible characteristic, said screw and/or said nut comprises studs made of magnetic material of north polarity and studs of magnetic material of south polarity, each stud of north polarity being in contact with the end of north polarity by at least one of said magnets and with the helix of corresponding north polarity, and each pad of south polarity being in contact with the end of south polarity of at least one of said magnets and with the helix of corresponding south polarity.

According to one possible characteristic, each stud is in contact with each winding of the corresponding propeller.

According to one possible characteristic, said magnets of said screw and/or of said nut have ortho-radial magnetization.

According to one possible characteristic, said magnets of said screw and/or of said nut have radial magnetization.

According to one possible characteristic, each pad of north polarity is in contact with the north poles of two consecutive magnets and the windings of the helix of corresponding north polarity, and each pad of south polarity is in contact with the south poles of two consecutive magnets and the corresponding south polarity helix windings.

According to one possible characteristic, each pad of north polarity is in contact with the north pole of a magnet and the windings of the helix of corresponding north polarity, and each pad of south polarity is in contact with the south pole of the magnet and the windings of the helix of corresponding south polarity.

According to one possible characteristic, an air gap is provided between the contiguous components of different polarity of said nut and of said screw.

According to one possible characteristic, each helix and/or each stud comprises recesses shaped respectively at the level of the studs and/or of the corresponding windings of different polarity to at least partially delimit said air gaps.

According to one possible characteristic, the surface of the helices of said nut facing said screw has alternating recesses and projections in the direction of said screw.

According to one possible characteristic, the surface of the helices of said screw oriented towards said nut has an alternation of recesses and projections in the direction of said nut.

According to one possible characteristic, the recesses and protrusions of the helices of north polarity of said nut and/or of said screw are angularly offset along said axis from those of the helices of south polarity of said nut and/or of said screw.

According to one possible characteristic, the recesses and protrusions of the helices of north polarity of said nut and/or of said screw are angularly offset along said axis from those of the propellers of south polarity of said nut and/or of said screw such that the protrusions of north polarity and the south polarity troughs are aligned along said axis while the south polarity prominences and the north polarity troughs are aligned along said axis.

According to one possible characteristic, the recesses and protrusions of the helices of north polarity of said nut and/or of said screw are aligned along said axis with those of the propellers of south polarity of said nut and/or of said screw such that the protrusions of polarity north and the prominences of south polarity are aligned along said axis while the troughs of south polarity and the troughs of north polarity are aligned along said axis.

According to one possible characteristic, the length of the studs along said axis is greater than or equal to that of said magnets along said axis.

According to a possible characteristic, the opposite ends of each stud are located respectively essentially in the plane of the ends of the end windings of the helices of said nut and/or of said screw.

According to one possible characteristic, said propellers are one-piece or consist of several propeller portions.

According to one possible characteristic, the pitch of the helices of said screw is not constant over its entire length.

In this case, the helices of said screw comprise at least two portions of different pitch.

The invention also relates to a device for generating electric current comprising an electric generator provided with a rotor and a stator, and a system according to any one of the above variants, in which said nut or said screw is linked to said rotor, a translation of said nut or of said screw inducing a rotation of said rotor and a generation of electric current by said generator.

The invention also relates to a device for generating a linear displacement comprising an electric motor provided with a stator and a rotor, and a system according to any one of the above variants, in which said nut or said screw is linked to said rotor, a rotation of said screw or of said nut by means of said motor generating a linear displacement of said nut or of said screw.

According to a possible variant, the magnets of said nut constitute the magnets of said rotor.

5. Description of figures

Other characteristics and advantages of the invention will appear on reading the following description of particular embodiments, given by way of simple illustrative and non-limiting example, and the appended drawings, among which:

FIG. 1 illustrates a perspective view of an example of a system according to the invention with ortho-radial magnets;

FIG. 2 illustrates a partial perspective view of a nut of the system of FIG. 1;

FIG. 3 illustrates a perspective view of a helix of the nut of FIG. 2;

FIG. 4 illustrates a perspective view of the assembly of two propellers of the nut of FIG. 2;

Figure 5 illustrates the assembly of Figure 4 with pads;

FIG. 6 illustrates a partial perspective view of a screw of the system of FIG. 1;

FIG. 7 illustrates a perspective view of a screw of the system of FIG. 1;

FIG. 8 illustrates a partial view of the screw of FIG. 7 from which the south polarity helix and the associated stud have been removed;

Figure 9 illustrates a perspective view of a helix of the screw of Figure 7;

FIG. 10 illustrates a perspective view of another helix of the screw of FIG. 7;

FIG. 11 illustrates the assembly of the propellers of FIGS. 9 and 10;

FIG. 12 illustrates the assembly of the propellers of FIGS. 9 and 10 with studs;

Figure 13 illustrates a cross-sectional view of the system of Figure 1;

FIG. 14 illustrates a cross-sectional view of the system of FIG. 1 offset by half a helix pitch along the axis X with respect to that of FIG. 13;

FIG. 15 illustrates the interaction between a helix of the screw and a helix of the nut of the system of FIG. 1;

FIG. 16 illustrates the interaction between the other helix of the screw (than that illustrated in FIG. 15) and the other helix of the nut of the system of FIG. 1;

FIG. 17 illustrates a perspective view of an example of a system according to the invention with radial magnets;

FIG. 18 illustrates a partial perspective view of a nut of the system of FIG. 17;

Figure 19 illustrates a partial assembly of the nut of Figure 18;

Figure 20 illustrates a partial assembly of the nut of Figure 18;

Figure 21 illustrates a partial assembly of a screw of a system of Figure 17;

Figure 22 illustrates a perspective view of a screw of the system of Figure 17;

Figure 23 illustrates a perspective view of a helix of the screw of Figure 22;

Figure 24 illustrates the assembly of two helices of the screw of Figure 22;

Figure 25 illustrates a cross-sectional view of the system of Figure 17;

FIG. 26 illustrates a cross-sectional view of the system of FIG. 17 offset by half a helix pitch along the axis X from that of FIG. 25;

FIG. 27 illustrates a perspective view of a variant of a system according to the invention;

Figure 28 illustrates a partial perspective view of the nut of a system of Figure 27;

Figure 29 illustrates a perspective view of a helix of the nut of Figure 28;

FIG. 30 illustrates a perspective view of the assembly of two helices of the nut of FIG. 28;

FIG. 31 illustrates a perspective view of another assembly of two propellers as a variant of FIG. 28;

Figure 32 illustrates a perspective view of the screw of a system of Figure 27;

Figure 33 illustrates a perspective view of a helix of the screw of Figure 32;

FIG. 34 illustrates an assembly variant of the helices of the screw of FIG. 32;

Figure 35 illustrates a partial view of a screw with an arrangement of helices as shown in Figure 34;

Figure 36 illustrates a cross-sectional view of the system of Figure 27;

FIG. 37 illustrates a cross-sectional view of the system of FIG. 27 offset from that of FIG. 36 along the X axis;

Figure 38 illustrates the interaction between a helix of the screw and a helix of the nut of the system of Figure 27;

figure 39 illustrates the interaction between the other helix of the screw (than that illustrated in figure 38) and the other helix of the nut of the system of figure 27;

FIG. 40 illustrates a perspective view of a linear motor comprising a system according to the invention;

Figure 41 illustrates the stator and rotor of the motor of Figure 40;

Figure 42 illustrates a partial cross-sectional view of the system of Figure 40;

FIG. 43 illustrates a partial cross-sectional view of the system of FIG. 40 offset from that of FIG. 42 along the X axis;

FIG. 44 illustrates the variation as a function of time of the speed of a press and of the force developed by the latter during a shaping operation (for example by stamping or other);

FIG. 45 schematically illustrates a variable-pitch magnetic screw-nut system;

Figure 46 illustrates a perspective view of a variable pitch propeller.

6. Description of particular embodiments

6.1. First embodiment: magnets with ortho-radial magnetization

A first embodiment of a magnetic screw-nut system according to the invention is presented in relation to FIGS. 1 to 16.

As shown in these figures, such a system comprises a screw 1 and a nut 2 designed to interact magnetically without direct mechanical contact. For this, the screw 1 is housed inside the nut 2, one and the other being separated by an air gap 3 for example consisting of air or vacuum. The screw and the nut have pitches of essentially the same value to ensure motion conversion, i.e. their helices have essentially the same pitch within geometrical tolerances.

Screw

The screw 1 comprises a shaft 10 which extends along an axis X. This shaft 10 is made of a non-magnetic material such as, for example, non-magnetic steel or the like.

Screw 1 includes magnets 11. These magnets 11 are permanent. Alternatively, these could be field coils acting as electromagnets. In this case :

- when said screw rotates, so-called "sliding" electrically conductive contacts (for example slip ring collector) can be used to supply these electromagnets;

- when said screw translates, the electromagnets can alternatively be powered by means of electrical conductors whose length will be chosen according to the relative movement of the screw and the nut.

These magnets are for example made of SmCo (Samarium Cobalt) or NdFeB (Neodymium Iron Boron) to maximize performance, but they can be made of other suitable materials.

The magnets 11 have a section in the form of a ring portion, in a plane perpendicular to the longitudinal axis of the shaft 10, and extend longitudinally along the longitudinal axis of the shaft 10. They may alternatively have a different shape. (e.g. parallelepipedic, trapezoid…) rather than the essentially tiled shape depicted.

For questions of manufacture, handling and assembly of the magnets, each magnet can be segmented into a plurality of magnets.

The magnets 11 have an ortho-radial magnetization.

In this embodiment, the polarized ends of the magnets are located in planes passing through the X axis. They could however be oriented differently, in particular be inclined, for example if the pads extend along axes inclined with respect to the X axis and located in planes parallel to the X axis.

The magnets are in this embodiment in an even number and distributed all around the outer periphery of the shaft 10 and this, in an essentially uniform manner. However, this might not be the case, even if such a distribution is preferred. A single magnet could be implemented with a magnet pad in contact with its north polarity end and the north polarity helix and a magnet pad in contact with its south polarity end and the south polarity helix, as this will come out more clearly later.

A stud 12, 13 is interposed between the consecutive magnets 11. Each stud 12, 13 is made of a magnetic material such as machined, molten or sintered metal or the like, for example.

The North (N) and South (S) polarity of the magnets 11 is alternated on either side of each pad 12, 13. Each pad 12, 13 is therefore located at the interface between the ends of the same polarity of two magnets 11 consecutive, and is in contact with them. Thus, the studs 12 in contact with the north polarity ends of the magnets 11 which surround it have a north polarity. Similarly, the studs 13 in contact with the south polarity ends of the magnets 11 which surround it have a south polarity.

The studs extend here along the X axis. They could however extend differently, in particular along axes inclined with respect to the X axis and located in planes parallel to the X axis.

The studs and the magnets are secured on the side of their inner surface to the outer surface of the shaft, preferably by gluing. Any other suitable connection solution can be implemented.

As the shaft is made of non-magnetic material, there is no air gap between the studs and the shaft or between the magnets and the shaft without the risk of a magnetic short-circuit between the magnets. In this way, the magnetic fluxes of the magnets 11 pass through the pads 12, 13 to magnetize them. The shaft could alternatively be made of a magnetic material subject to providing an air gap between the shaft and the studs and magnets.

The screw 1 comprises a north-polarized helix 14 and a south-polarized helix 15 placed at the outer periphery of the studs 12, 13 and magnets 11. Their inner surface is secured to the studs of the same polarity, for example by gluing or the like.

The propellers 14, 15 are made of magnetic material (for example machined, molten or sintered metal, etc.). They extend parallel to each other in a helical manner around the axis X of the shaft 10. They have the same diameter.

Each helix 14, 15 comprises a plurality of windings 140, 150, each winding forming a turn around the shaft 10.

Helices 14 and 15 have identical lengths along the X axis.

The helices 14, 15 are separated from each other by an air gap 16. In other words, the consecutive windings 140, 150 of the helices 14, 15 are separated by an air gap 16. This air gap prevents the looping of the field magnetic between the propellers 14, 15 and must be larger than the air gap 3.

The north polarized helix 14 is in contact with the north polarized pads 12 in contact with the north polarity ends of the magnets 11.

The south polarized helix 15 is in contact with the south polarized studs 13 in contact with the south polarity ends of the magnets 11.

The helices are thus magnetized by the studs. The studs 12, 13 act as magnetic flux distributors produced by the magnets 11 and concentrate these fluxes to distribute them towards the helices 14, 15.

Preferably, each pad 12, 13 is in contact with each winding 140, 150 of identical polarity.

An air gap 17 is provided between each magnet 11 and the inner contour of each helix 14, 15. This allows the magnetic fluxes of the magnets 11 to pass through the studs 12, 13.

An air gap 18 is arranged between each stud 12 of north polarity and each winding 150 of the helix of south polarity 15.

An air gap 19 is provided between each pad 13 of south polarity and each winding 140 of the helix of north polarity 14.

The air gaps prevent magnetic short circuits. They can be made of vacuum, air or non-magnetic material such as a resin or other.

The helices 14 and 15 therefore have different polarities.

The thicknesses of the air gaps 17, 18 and 19 must be greater than that of the air gap 3 so that the magnetic fluxes created by the magnets 11 and conveyed by the magnetic pads 12, 13 then by the propellers 14, 15 cross the air gap 3 and interact with the nut to provide motion conversion.

The gaps 18 and 19 are here constituted by notches 141, 151, or recesses, adapted to the shape of the corresponding propeller. These notches are provided for this purpose on the inner periphery of the helices 14, 15. The air gaps could be formed in any other suitable alternative manner.

More specifically, the notches 141 are provided on the windings 140 of the helix 14 of north polarity to the right, i.e. at the level, of the studs 13 of south polarity. Similarly, the notches 151 are provided on the windings 150 of the helix 15 of south polarity to the right of the studs 12 of north polarity.

The notches 141 and 151 are therefore offset by a polar pitch corresponding to the angular distance between the consecutive pads of different polarity.

Alternatively, the notches could be provided on the studs rather than on the helices or on the studs and the helices.

The length of the studs 12, 13 along the X axis can be less than, equal to or greater than that of the magnets along the X axis. However, it will preferably be greater in order to optimize the creation of magnetic fluxes from the magnets because the air gaps 18 and 19 modify the axial length along axis X of the flux created by magnets 11. In this case, each stud 12, 13 will extend longitudinally on either side beyond the corresponding magnet.

The pads 12, 13 may be offset from each other along the X axis or their end surface inclined so that the opposite ends of each pad are located respectively essentially in the plane of the ends of the windings 140, 150 of end, that is to say those located at the opposite ends of the helices 14, 15. This allows them to better follow the active length of the helices.

The contact surface of a stud 12, 13 with the corresponding helix is preferably greater than its contact surfaces with the magnets 11.

The pitch of screw 1 is equal to the sum of the thickness along the X axis of a winding 140 of north polarity, of that of a winding 150 of south polarity and of two air gaps 16.

The shaft 10 makes it possible to mechanically attach all the magnets 11 and magnetic studs 12, 13, and to transmit the transverse force. As the shaft is non-magnetic, there is no magnetic short circuit between the magnets. The magnetic fluxes of the magnets 11 then pass through the magnetic pads 12, 13 and make it possible to magnetize the helices 14, 15 which respectively constitute north and south magnetic pads. The helices provide alternating polarity.

Nut

The nut 2 comprises a cylindrical casing 20 which extends along the axis X. This casing 20 is made of a non-magnetic material such as, for example, non-magnetic steel or the like.

Nut 2 includes magnets 21. These magnets 21 are permanent. Alternatively, these could be excitation coils acting as electromagnets. In this case :

- when the nut rotates, so-called "sliding" electrically conductive contacts (for example slip ring collector) can be used to power these electromagnets;

- when the nut translates, the electromagnets can alternatively be powered by means of electrical wires, the length of which will be chosen according to the relative movement path of the screw and the nut.

These magnets are for example made of SmCo or NdFeB to maximize performance but can be made of other suitable materials.

The magnets 21 have a section in the form of a ring portion, in a plane perpendicular to the longitudinal axis of the casing 20, and extend longitudinally along the longitudinal axis X of the casing 20. They may alternatively have a different shape (for example parallelepipedal, trapezoid, etc. rather than the essentially tiled shape represented.

For questions of manufacture, handling and assembly of the magnets, each magnet can be segmented into a plurality of magnets.

The magnets 21 have an ortho-radial magnetization.

In this embodiment, the polarized ends of the magnets are located in planes parallel to the longitudinal axis of the casing passing through the axis X. They could however be oriented differently, in particular be inclined, for example if the studs extend along axes inclined with respect to the X axis and located in planes parallel to the X axis.

The magnets are in this embodiment in an even number and distributed all around the inner periphery of the casing 20 and this, in an essentially uniform manner. However, this might not be the case, even if such a distribution is preferred. A single magnet could be implemented with a magnet pad in contact with its north polarity end and the north polarity helix and a magnet pad in contact with its south polarity end and the south polarity helix, as this will come out more clearly later.

A stud 22, 23 is interposed between the consecutive magnets 21. Each stud 22, 23 is made of a magnetic material such as machined, molten or sintered metal or the like.

The polarity of the magnets 21 is alternated on either side of each pad 22, 23. Each pad 22, 23 is therefore located at the interface between the ends of the same polarity of two consecutive magnets 21, and is in contact with these. Thus, the pads 22 in contact with the north polarity ends of the magnets 21 which surround it, have a north polarity. Similarly, the studs 23 in contact with the south polarity ends of the magnets 21 which surround it, have a south polarity.

The studs extend here along the X axis. They could however extend differently, in particular along axes inclined with respect to the X axis and located in planes parallel to the X axis.

The studs and the magnets are secured on the side of their outer surface to the inner surface of the casing 20, preferably by gluing. Any other suitable connection solution can be implemented.

The casing 20 being made of non-magnetic material, no air gap is provided between the studs and the casing or between the magnets and the casing without the risk of a magnetic short-circuit between the magnets. In this way, the magnetic fluxes of the magnets 21 pass through the pads 22, 23 to magnetize them. The casing could alternatively be made of a magnetic material subject to providing an air gap between the casing and the studs and magnets.

The nut 2 comprises a north polarized helix 24 and a south polarized helix 25 placed on the inner periphery of the studs 22, 23 and magnets 21. Their outer surface is secured to the studs of the same polarity, for example by gluing or the like.

The propellers 24, 25 are made of magnetic material (for example machined, molten or sintered metal, etc.). They extend parallel to each other in a helical manner around the axis X of the housing 20.

Each propeller 24, 25 comprises a plurality of windings 240, 250, each winding forming a turn around the longitudinal axis of the housing 20.

Helices 24 and 25 have identical lengths along the X axis.

The helices 24, 25 are separated from each other by an air gap 26. In other words, the consecutive windings 240, 250 of the helices 24, 25 are separated by an air gap 26. This air gap prevents the looping of the field magnetic between the helices 24, 25 and must therefore be larger than the air gap 3.

The north polarized helix 24 is in contact with the north polarized pads 22 in contact with the north polarity ends of the magnets 21.

The south polarized helix 25 is in contact with the south polarized studs 23 in contact with the south polarity ends of the magnets 21.

The helices are thus magnetized by the studs which act as magnetic flux distributors produced by the magnets 21 and concentrate these fluxes to distribute them to the helices 24, 25.

Preferably, each pad 22, 23 is in contact with each winding 240, 250 of identical polarity.

An air gap 27 is provided between each magnet 21 and the outer contour of each helix 24, 25. This allows the magnetic fluxes of the magnets 21 to pass through the studs 22, 23.

An air gap 28 is provided between each stud 22 of north polarity and each winding 250 of the helix of south polarity 25.

An air gap 29 is provided between each pad 23 of south polarity and each winding 240 of the helix of north polarity 24.

The air gaps prevent magnetic short circuits. They can be made of vacuum, air or non-magnetic material such as a resin or other.

The helices 24 and 25 therefore have different polarities.

The thicknesses of the air gaps 27, 28 and 29 must be greater than that of the air gap 3 so that the magnetic fluxes created by the magnets 21 and conveyed by the magnetic pads 22, 23 then by the propellers 24, 25 cross the air gap 3 and interact with the screw to provide motion conversion.

The gaps 28 and 29 are here formed by notches 241, 251, or recesses, adapted to the shape of the corresponding propeller. These notches are provided for this purpose at the outer periphery of the helices 24, 25. The air gaps could be formed in any other suitable alternative manner.

More specifically, the notches 241 are provided on the windings 240 of the helix 24 of north polarity to the right of the studs 23 of south polarity. Similarly, the notches 251 are provided on the windings 250 of the helix 25 of south polarity to the right of the studs 22 of north polarity.

The notches 241 and 251 are therefore offset by a polar pitch corresponding to the angular distance between the consecutive pads of different polarity.

Alternatively, the notches could be provided on the studs rather than on the helices or on the studs and the helices.

The length of the studs 22, 23 along the X axis can be less than, equal to or greater than that of the magnets along the X axis. However, it will preferably be greater in order to optimize the creation of magnetic fluxes from the magnets because the air gaps 28 and 29 modify the axial length along axis X of the flux created by magnets 21. In this case, each pad 22, 23 will extend longitudinally on either side beyond the corresponding magnet.

The studs 22, 23 may be offset from each other along the X axis or their end surfaces may be inclined so that the opposite ends of each stud lie respectively essentially in the plane of the ends of the windings 240, 250 d 'end, that is to say those located at the opposite ends of the helices 24, 25. This allows them to better follow the active length of the helices.

The contact surface of a pad 22, 23 with the corresponding helix is preferably greater than its contact surfaces with the magnets 21.

The pitch of nut 2 is equal to the sum of the thickness along the X axis of a winding 240 with north polarity, that of a winding 250 with south polarity and two air gaps 26.

The casing 20 makes it possible to mechanically attach all the magnets 21 and magnetic studs 22, 23, and to transmit the torque. As the housing is non-magnetic, there is no magnetic short circuit between the magnets. The magnetic fluxes of the magnets 21 then pass through the magnetic pads 22, 23 and make it possible to magnetize the helices 24, 25 which respectively constitute north and south magnetic pads. The helices provide alternating polarity.

6.2. Second embodiment: magnets with radial magnetization

A second embodiment of a magnetic screw-nut system according to the invention is presented in relation to FIGS. 17 to 26.

As shown in these figures, such a system comprises a screw 1 and a nut 2 designed to interact magnetically without direct mechanical contact. For this, the screw 1 is housed inside the nut 2, one and the other being separated by an air gap 3 of air or vacuum for example. The screw and the nut have pitches of essentially the same value to ensure motion conversion, i.e. their helices have pitches of essentially the same value, within geometric tolerances.

Screw

The screw 1 comprises a shaft 10 which extends along an axis X. This shaft 10 is made of a magnetic material such as for example magnetic steel or the like.

Screw 1 includes magnets 11. These magnets 11 are permanent. Alternatively, these could be excitation coils acting as electromagnets. In this case :

- when the screw rotates, so-called "sliding" electrically conductive contacts (for example slip ring collector) can be used to supply these electromagnets;

- when the screw translates, the electromagnets can alternatively be powered by means of electric wires, the length of which will be chosen according to the relative movement of the screw and the nut.

These magnets are for example made of SmCo or NdFeB to maximize performance but can be made of other suitable materials.

The magnets 11 have a section in the form of a ring portion, in a plane perpendicular to the longitudinal axis of the shaft 10, and extend longitudinally along the longitudinal axis of the shaft 10. They may alternatively have a different shape. (e.g. parallelepipedic, trapezoid…) rather than the essentially tiled shape depicted.

For questions of manufacture, handling and assembly of the magnets, each magnet can be segmented into a plurality of magnets.

The magnets 11 have a radial magnetization.

In this embodiment, the opposite surfaces of the magnets taken in a direction orthogonal O to the longitudinal axis X (i.e. along a radius) have different polarities. The magnets could however be oriented differently.

This type of magnet can be preferred to magnets with ortho-radial magnetization, for example, depending on the size and the performance required.

Screw 1 comprises a north polarized helix 14 and a south polarized helix 15.

The propellers 14, 15 are made of magnetic material (for example machined, molten or sintered metal, etc.). They extend parallel to each other in a helical manner around the axis X of the shaft 10. They have the same diameter.

Each helix 14, 15 comprises a plurality of windings 140, 150, each winding forming a turn around the shaft 10.

Helices 14 and 15 have identical lengths along the X axis.

The helices 14, 15 are separated from each other by an air gap 16. In other words, the consecutive windings 140, 150 of the helices 14, 15 are separated by an air gap 16. This air gap prevents looping back of the field magnetic between the helices and must therefore be larger than the air gap 3.

The magnets are in this embodiment in an even number and distributed all around the outer periphery of the shaft 10 and this in an essentially uniform manner. However, this might not be the case, even if such a distribution is preferred. At least two magnets should be implemented with one magnetic pad contacting the north polarity end of one of the magnets and the north polarity helix and one magnetic pad contacting the south polarity end of the other magnet and the south polarity helix, as will become clear later.

The polarity of successive magnets is reversed. Thus, when a magnet has its north polarized face oriented towards the shaft 10 and therefore its south polarized face oriented towards the helices, then the following magnet has its south polarized face oriented towards the shaft 10 and therefore its north polarized face oriented towards the propellers.

Screw 1 includes magnetic studs 12, 13 made of magnetic material. Each magnetic pad is interposed between the outer face of a magnet and the inside of the helices.

The magnetic studs 12 in contact with the north polarity end of the corresponding magnets are of north polarity.

The magnetic pads 13 in contact with the southern polarity end of the corresponding magnets are of southern polarity.

The studs extend here along the X axis. They could however extend differently, in particular along axes inclined with respect to the X axis and located in planes parallel to the X axis.

The magnets are secured on the side of their inner surface to the outer surface of the shaft, preferably by gluing. Any other suitable connection solution can be implemented.

The pads are secured on the side of their inner surface to the outer surface of the magnets, preferably by gluing. Any other suitable connection solution can be implemented.

The north polarized helix 14 is in contact with the north polarized pads 12 in contact with the north polarity ends of the magnets 11.

The south polarized helix 15 is in contact with the south polarized studs 13 in contact with the south polarity ends of the magnets 11.

The helices are thus magnetized by the pads. The pads act as magnetic flux distributors produced by the magnets and concentrate these fluxes to distribute them to the propellers.

The inner surface of the helices is secured to the outer surface of the pads of the same polarity, preferably by gluing or the like.

Preferably, each pad is in contact with each winding of the helix of identical polarity.

An air gap 37 is provided between the consecutive magnets and between the consecutive pads to avoid short circuits between the magnets.

An air gap 38 is provided between each stud 12 of north polarity and each winding 150 of the helix of south polarity 15.

An air gap 39 is provided between each pad 13 of south polarity and each winding 140 of the helix of north polarity 14.

The air gaps prevent magnetic short circuits. They can be made of vacuum, air or non-magnetic material such as a resin or other.

The helices 14 and 15 therefore have different polarities.

The thicknesses of the air gaps 37, 38 and 39 must be greater than that of the air gap 3 so that the magnetic fluxes created by the magnets 11 and conveyed by the magnetic pads 12, 13 then by the propellers 14, 15, cross the air gap. 3 and interact with the nut to provide motion conversion.

The gaps 38 and 39 are here formed by notches 141, 151, or recesses, adapted to the shape of the corresponding propeller. These notches are provided for this purpose on the inner periphery of the helices 14, 15. The air gaps could be formed in any other suitable alternative manner.

More specifically, the notches 141 are provided on the windings 140 of the helix 14 of north polarity to the right of the pads 13 of south polarity. Similarly, the notches 151 are provided on the windings 150 of the helix 15 of south polarity to the right of the studs 12 of north polarity.

The notches 141 and 151 are therefore offset by a polar pitch corresponding to the angular distance between the consecutive pads of different polarity.

Alternatively, the notches could be provided on the studs rather than on the helices or on the studs and the helices.

The length of the studs 12, 13 along the X axis can be less than, equal to or greater than that of the magnets along the X axis. However, it will preferably be greater in order to optimize the creation of magnetic fluxes from the magnets because the air gaps 38 and 39 modify the axial length along axis X of the flux created by magnets 11. In this case, each stud 12, 13 will extend longitudinally on either side beyond the corresponding magnet.

The pads 12, 13 can be offset from each other along the X axis or their end surfaces can be inclined so that the opposite ends of each pad are located respectively essentially in the plane of the ends of the windings 140, 150 d 'end, that is to say those located at the opposite ends of the helices 14, 15. This allows them to better follow the active length of the helices.

The contact surface of a stud 12, 13 with the corresponding helix is preferably greater than its contact surfaces with the magnets 11.

The pitch of screw 1 is equal to the sum of the thickness along the X axis of a winding 140 of north polarity, of that of a winding 150 of south polarity and of two air gaps 16.

The shaft 10 makes it possible to mechanically attach all the magnets 11 and magnetic studs 12, 13, and to transmit the transverse force. Since the shaft is made of magnetic material, it allows the magnetic fields produced by the magnets to be looped back. The magnetic fluxes of the magnets then pass through the pads with which they are in contact and make it possible to magnetize the helices which respectively constitute north and south magnetic pads. The helices ensure the alternation of polarity.

Nut

The nut 2 comprises a cylindrical casing 20 which extends along the axis X. This casing 20 is made of a magnetic material.

Nut 2 includes magnets 21. These magnets 21 are permanent. Alternatively, these could be excitation coils acting as electromagnets. In this case :

- when the nut rotates, so-called "sliding" electrically conductive contacts (for example slip ring collector) can be used to power these electromagnets;

- when the nut translates, the electromagnets can alternatively be powered by means of electrical wires, the length of which will be chosen according to the relative movement path of the screw and the nut.

These magnets are for example made of SmCo or NdFeB to maximize performance but can be made of other suitable materials.

The magnets 21 have a section in the form of a ring portion, in a plane perpendicular to the longitudinal axis of the casing 20, and extend longitudinally along the longitudinal axis of the casing 20. They may alternatively have a different shape (for example parallelepipedic , trapezium…) rather than the essentially tiled shape represented.

For questions of manufacture, handling and assembly of the magnets, each magnet can be segmented into a plurality of magnets.

The magnets 21 have a radial magnetization.

In this embodiment, the opposite surfaces of the magnets taken in a direction orthogonal O to the longitudinal axis X (i.e along a radius) have different polarities. The magnets could however be oriented differently.

This type of magnet may be preferred to magnets with ortho-radial magnetization, for example depending on the size and/or the required performance.

Nut 2 includes a 24 north polarized propeller and a 25 south polarized propeller.

The propellers 24, 25 are made of magnetic material (for example machined, molten or sintered metal, etc.). They extend parallel to each other in a helical manner around the axis X of the housing 20. They have the same diameter.

Each propeller 24, 25 comprises a plurality of windings 240, 250, each winding forming a turn around the axis X of the housing 20.

Helices 24 and 25 have identical lengths along the X axis.

The helices 24, 25 are separated from each other by an air gap 26. In other words, the consecutive windings 240, 250 of the helices 24, 25 are separated by an air gap 26. This air gap prevents looping back of the field magnetic between the helices and must therefore be larger than the air gap 3.

The magnets are in this embodiment in an even number and distributed all around the inner periphery of the casing 20 and this, in an essentially uniform manner. However, this might not be the case, even if such a distribution is preferred. At least two magnets should be implemented with one magnetic pad contacting the north polarity end of one of the magnets and the north polarity helix and one magnetic pad contacting the south polarity end of the other magnet and the south polarity helix, as will become clear later.

The polarity of successive magnets is reversed. Thus, when a magnet has its north polarized face oriented towards the housing 20 and therefore its south polarized face oriented towards the propellers, then the following magnet has its south polarized face oriented towards the housing 20 and therefore its north polarized face oriented towards the propellers.

The nut 2 comprises magnetic studs 22, 23 made of magnetic material. Each magnetic pad is interposed between the inner face of a magnet and the outside of the helices.

The magnetic studs 22 in contact with the north polarity end of the corresponding magnets are of north polarity.

The magnetic pads 23 in contact with the southern polarity end of the corresponding magnets are of southern polarity.

The studs extend here along the X axis. They could however extend differently, in particular along axes inclined with respect to the X axis and located in planes parallel to the X axis.

The magnets are secured on the side of their outer surface to the inner surface of the casing, preferably by gluing. Any other suitable connection solution can be implemented.

The pads are secured on the side of their outer surface to the inner surface of the magnets, preferably by gluing. Any other suitable connection solution can be implemented.

The north polarized helix 24 is in contact with the north polarized pads 22 themselves in contact with the north polarity ends of the magnets 21.

The south polarized helix 25 is in contact with the south polarized pads 23 themselves in contact with the south polarity ends of the magnets 21.

The helices are thus magnetized by the studs. The pads act as magnetic flux distributors produced by the magnets and concentrate these fluxes to distribute them to the propellers.

The outer surface of the helices is secured to the inner surface of the pads of the same polarity, preferably by gluing or the like.

Preferably, each pad is in contact with each winding of the helix of identical polarity.

An air gap 47 is provided between the consecutive magnets and between the consecutive pads to avoid short circuits between the magnets.

An air gap 48 is arranged between each stud 22 of north polarity and each winding 250 of the helix of south polarity 25.

An air gap 49 is provided between each pad 23 of south polarity and each winding 240 of the helix of north polarity 24.

The air gaps prevent magnetic short circuits. They can be made of vacuum, air or non-magnetic material such as a resin or other.

The helices 24 and 25 therefore have different polarities.

The thicknesses of the air gaps 47, 48 and 49 must be greater than that of the air gap 3 so that the magnetic fluxes created by the magnets 21 and conveyed by the magnetic studs 22, 23 then by the propellers 24, 25 cross the air gap 3 and interact with the screw to provide motion conversion.

The gaps 48 and 49 are here constituted by notches 241, 251, or recesses, adapted to the shape of the corresponding propeller. These notches are provided for this purpose at the outer periphery of the helices 24, 25. The air gaps could be formed in any other suitable alternative manner.

More specifically, the notches 241 are provided on the windings 240 of the helix 24 of north polarity to the right of the studs 23 of south polarity. Similarly, the notches 251 are provided on the windings 250 of the helix 25 of south polarity to the right of the studs 22 of north polarity.

The notches 241 and 251 are therefore offset by a polar pitch corresponding to the angular distance between the consecutive pads of different polarity.

Alternatively, the notches could be provided on the studs rather than on the helices or on the studs and the helices.

The length of the studs 22, 23 along the X axis can be less than, equal to or greater than that of the magnets along the X axis. However, it will preferably be greater in order to optimize the creation of magnetic fluxes from the magnets because the air gaps 48 and 49 modify the axial length along axis X of the flux created by magnets 21. In this case, each stud 22, 23 will extend longitudinally on either side beyond the corresponding magnet.

The studs 22, 23 may be offset from each other along the X axis or their end surfaces may be inclined so that the opposite ends of each stud lie respectively essentially in the plane of the ends of the windings 240, 250 d 'end, that is to say those located at the opposite ends of the helices 24, 25. This allows them to better follow the active length of the helices.

The contact surface of a pad 22, 23 with the corresponding helix is preferably greater than its contact surfaces with the magnets 21.

The pitch of nut 2 is equal to the sum of the thickness along the X axis of a winding 240 with north polarity, that of a winding 250 with south polarity and two air gaps 26.

The casing 20 makes it possible to mechanically attach all the magnets 21 and magnetic studs 22, 23, and to transmit the torque. Since the casing 20 is made of magnetic material, it makes it possible to loop back the magnetic fields produced by the magnets. The magnetic fluxes of the magnets then pass through the pads with which they are in contact and make it possible to magnetize the helices which respectively constitute north and south magnetic pads. The helices ensure the alternation of polarity.

6.3. Functioning

The operating principles of a system according to the first and second embodiments are similar.

When the screw 1 is inside the nut 2, the north polarity helix 14 and the south polarity helix 15 of the screw 1 interact, or cooperate magnetically respectively with the south polarity helix 25 and the north polarity helix 24 of the nut 2. In other words, each winding 140 of the north polarity helix 14 of the screw 1 is attracted by the corresponding winding 250 of the south polarity helix 25 of nut 2, and each winding 150 of the south polarity helix 15 of screw 1 is attracted by the corresponding winding 240 of the north polarity helix 24 of nut 2.

The nut and the screw cooperate or interact magnetically. The relative movements of the screw and the nut therefore take place without contact between them and result from the forces of magnetic attraction and repulsion between them.

According to a first configuration, the system comprises means for locking the screw in rotation along the X axis and guiding it in translation along the X axis while the nut is free in rotation along the X axis but not in translation. Such means are known and are not described in detail.

Thus, a rotational movement of the nut 2 around the screw 1 generates a translational movement of the screw 1 along the X axis. Conversely, a translational movement of the screw along the X axis generates a rotation of the nut around the X axis.

According to a second configuration, the system comprises means for locking the nut in rotation along the X axis and guiding it in translation along this axis, while the screw is free in rotation along the X axis but locked in translation. Such means are known per se and are not described in detail.

Thus, a rotational movement of the screw 1 inside the nut 2 generates a translational movement of the nut 2 along the X axis. Conversely, a translational movement of the nut along the X axis generates a rotation of the screw around the X axis.

6.4. Benefits

The technique according to the invention has many advantages, including in particular:

- the magnets have a relatively simple shape regardless of the helical profile and the desired translation and rotation movements: they therefore have a relatively low manufacturing cost, which reduces the cost of a device according to the invention;

- the number of magnets and the volume of magnets can be optimized independently of the desired pitch of the propeller: it is thus possible to easily vary the capacity to supply forces of a system according to the invention;

- the magnetic blocks ensuring the conversion of a rotary movement into a translational movement and vice versa are parts which can be machined and which can have precise dimensions. The helical profile can therefore be precise, and ensure precise translational positioning of the screw when the nut rotates or precise translational positioning of the nut when the screw rotates. A system according to the invention is therefore precise;

- a system according to the invention benefits from better energy efficiency than those of the prior art due to better electromechanical conversion of energy thanks to the absence of mechanical contact between the nut and the screw and optimization of the volume of magnets used . The operating cost of a system according to the invention is consequently lower than that of the systems of the prior art.

6.5. Variants

Each propeller may be formed in one piece and constitute a one-piece assembly. Alternatively, each helix to be formed by the juxtaposition of a plurality of helix portions. Of course, one or more propellers may be one-piece and the other(s) made up of a plurality of propeller portions.

A variant is presented in relation to FIGS. 27 to 39.

The variant described below is related to the first embodiment. However, it can just as easily be implemented in the first and second embodiments.

In this variant, the surface of the helices 24, 25 of the nut 2 oriented towards the screw 1 has an alternation of hollows 242, 252 and projections 243, 253 in the direction of the screw 1.

The surface of the helices 14, 15 of the screw 1 oriented towards the nut 2 has an alternation of hollows 142, 152 and projections 143, 153 in the direction of the nut 2.

The recesses 242 and protrusions 243 of the north polarity helix 24 of the nut 2 can be angularly offset along the axis X from those of the south polarity helix 25 of the nut 2 so that the protrusions of north polarity 243 and the south polarity troughs 252 are aligned along the X axis while the south polarity projections 253 and the north polarity troughs 242 are aligned along the X axis (cf. FIG. 31).

In this case, the recesses 142 and protrusions 143 of the north polarity helix 14 of the screw 1 are angularly offset along the axis from those of the south polarity helix 15 of the screw 1 in such a way that the protrusions of north polarity 143 and the south polarity troughs 152 are aligned along the X axis while the south polarity projections 153 and the north polarity troughs 142 are aligned along the X axis (cf. FIG. 34).

The recesses 242 and projections 243 of the north polarity helix 24 of the nut 2 can be aligned with those of the south polarity helix 25 of the nut 2 so that the north polarity projections 243 and the projections of south polarity 253 are aligned along the X axis while the south polarity troughs 252 and the north polarity troughs 242 are aligned along the X axis (cf. FIGS. 28 and 30).

In this case, the recesses 142 and protrusions 143 of the helix of north polarity 14 of the screw 1 are aligned with those of the helix of south polarity 15 of the screw 1 so that the protrusions of north polarity 143 and the prominences of south polarity 153 are aligned along the X axis whereas the troughs of south polarity 152 and the troughs of north polarity 142 are aligned along the axis X (cf. FIG. 32).

The recesses and protrusions of the north polarity helix of the nut can be angularly offset from those of the south polarity helix of the nut in any intermediate position between the two extreme positions described above.

The hollows and protrusions of the helix of northern polarity of the screw can be angularly offset from those of the helix of southern polarity of the screw in any intermediate position between the two extreme positions described above.

It is possible that the type of offset or alignment of the recesses and protrusions implemented on the nut is different from that implemented on the screw. However, it is preferable that it be the same on the screw and on the nut.

It is also possible for dimples and protrusions to be implemented only on the nut or the screw but this is not preferred.

The patterns of these projections and recesses must preferably be regular along the helical profile to avoid discontinuities in the transmission of movement.

The profiles of the valleys and protrusions on a helix can be different in terms of geometry (shape and dimensions). In the embodiments described, the depressions and protrusions have essentially rectangular sections by way of illustration. Their sections could however be different, for example trapezoidal, with rounded edges…. On a propeller, the shape and/or dimensions of the protrusions may be different from those of the hollows. The shapes and/or dimensions of the recesses and protrusions of the screw may be different from those of the recesses and protrusions of the nut.

These hollows and protrusions are possible and relatively simple to implement because the helices are made of magnetic materials (steel for example) and can be machined.

These notches at the level of the nut and the screw make it possible to vary the reluctance of the magnetic circuit on the one hand between the north helix of the screw and the south helix of the nut and on the other hand between the the south helix of the screw and the north helix of the nut along the helical profile of the screw and the nut. These notches can reduce the average value of the magnetic field in the air gap between the screw and the nut compared to a device without notches, but they make it possible to increase the hooking effect and thus the transmission of forces between the nut 1 and screw 2 for a given volume.

The first and second embodiments can be combined with each other. Thus, a screw can include ortho-radial magnets and the nut can include radial magnets or vice versa.

Taking a radial direction, the inside is oriented towards the screw while the outside is oriented towards the nut.

The means of assembly to connect the various components together will be chosen so as to avoid or limit air gaps when they are not desired.

6.6. Application examples

One of the applications of the invention consists of an electric machine that can operate either as a linear motor (conversion of electrical energy into mechanical energy characterized by a linear movement), or as a generator (conversion of mechanical energy characterized by a linear in electrical energy).

The invention can for example be used in the fields of robotics, machine tools including industrial presses, and the production of electricity from, in particular, the recovery of wave energy.

An example of application is presented in relation to figures 40 to 43. The principle described in relation to these figures, although relating to the second embodiment, can be implemented indiscriminately in any of the embodiments described as well as their variants.

In this example, the magnets of the nut constitute the magnets of the rotor of a rotating electrical machine. It can for example be a stepper motor, a variable reluctance motor, a synchronous motor or other.

More specifically, the casing 20 houses the stator 50 of an electric machine.

The casing 20 notably allows the mechanical connection between the stator 50 and the rest of the electrical machine (not shown), such a casing is commonly encountered in electrical machines.

The stator 50 includes notches 51 in which a winding is present. The winding is not shown. The stator 50 is a conventional stator of a rotating electrical machine, for example that of a so-called “brushless” motor in English.

In the figures, the stator has twenty-four notches 51 but this number is not restrictive to the application of the invention. It may vary in particular according to the desired characteristics of the electrical machine, the number of phases and the number of poles.

The stator 50 could for example be composed of stacked magnetic laminations such as those commonly encountered in rotating electrical machines or of magnetic powder (for example: SMC, Soft Magnetic Composites). However, other suitable materials could be used. It could also still be a machine stator of the so-called "ironless" type in English. In general, the stator 50 may be of any type.

Nut 2 acts as a rotor interacting with stator 50.

An air gap 53 is provided between the face of the magnets 21 facing the stator and the coils of the stator.

The magnetic flux from the north pole of a magnet 21 magnet crosses the air gap 53 to pass into the stator 50 and loop back with the south pole of the next magnet 21. In the configuration according to the second embodiment, this magnetic flux passes through the casing 20 but is ultimately not exploited, while in the application described here, this magnetic flux is exploited by crossing the stator 50.

The flow of the magnets 21 passes through the stator 50 as described above, then passes through the magnetic pads 22, 23, then through the helices 24, 25 (which are therefore magnetized) to loop back with the magnets 11 of the screw 1.

In motor mode, the conversion of electrical energy between the currents of the winding carried by the stator and the magnetic fields of the magnets 21 allows the rotation of the nut 2. Thus, the propellers 24, 25 are driven in a rotational movement .

In motor mode, the magnets 21 act with the winding of the stator to rotate the nut carrying the north 24 and south 25 helices. The south polarity helix 25 of the nut can interact with the helix 14 of north polarity of the screw. At the same time, the 24 north polarity helix of the nut can interact with the 15 south polarity helix of the screw. In fact, the screw 1 follows a linear movement. Thus, there is conversion of electrical energy supplied to the stator into mechanical energy characterized by a linear movement at the screw 1.

In generator mode, the screw 1 which follows a linear movement, drives the nut 2 in rotation. The magnets 21 of the nut 2 in rotation, create a rotating magnetic field in the stator 50. There is therefore a voltage generation electrical at the level of the winding carried by the stator. Thus, there is conversion of mechanical energy characterized by a linear movement of the screw into electrical energy.

The advantage of this structure is to obtain a compact electric machine, a linear motion motor from a conventional rotary electric machine structure, and an electric generator producing electrical energy from a linear motion.

A system according to the invention can be implemented in other applications, in particular the following.

In generator mode:

- a linear movement of the screw can generate a rotary movement of the nut to rotate the rotor of an electric current generator; the drive of a rotor of a generator by the nut can be direct as in the previous application or if the nut cooperates with the hollow rotor of a generator, or indirect by means of transmission elements (chain , belt, sprockets, etc.);

- a linear movement of the nut can generate a rotary movement of the screw to rotate a rotor of an electric current generator; the drive of a rotor of a generator by the screw can be direct if the screw is the shaft of the rotor of the generator or cooperates with the hollow rotor of a generator, or indirect by means of transmission elements (chain , sprockets, belt…) .

The invention relates in this sense to a device for generating electric current.

In engine mode:

• a rotary movement of the screw generated by a motor can generate a translational movement of the nut;
• a rotary movement of the nut generated by a motor can generate a translational movement of the screw.

The invention relates in this sense to a device for generating linear motion, also called a linear motor.

6.7. Variant with variable pitch screw

We present in relation to figures 44 to 46 a variant of a magnetic screw-nut system whose screw has a variable pitch.

Some mechanical systems make it possible to generate a thrust force, such as industrial presses, for example.

In order to optimize the forming operations by means of such a system, such as for example the forming of parts, it may be required that the shaft of the cylinder transmitting the thrust be driven during its stroke by a phase of approach then, through a work phase.

During the approach phase, the speed of the cylinder may be faster than during the work phase, and the force developed during the approach phase may be lower compared to the forces required during the phase of work. This principle is illustrated in figure 44 which illustrates the variation in the speed of the cylinder and the forces deployed by it during a pressing operation.

In the field of presses using hydraulic cylinders, this movement in two phases requires the implementation of two cylinders, i.e. a small fast cylinder for the approach phase and a slower cylinder but developing greater efforts for the phase of work.

In the field of presses using rotary electric motors fitted with mechanical screw-nuts, the two-phase movement is obtained by modulating the speed of the electric motor for this purpose. In this case, the characteristics (mechanical, lubrication) of the screw-nut must therefore be provided over their entire length.

In these cases, the systems are complicated and expensive.

The variant discussed below proposes a solution to make it possible to vary the speed of a screw and the forces transmitted by the latter without modifying the speed of the nut or of the screw depending on whether the nut or the screw is leading.

This variant is applicable to one or other of the magnetic screw-nut variants according to the invention. It can also be implemented in the context of any magnetic screw-nut of the prior art such as those described in the paragraph devoted to the prior art. In general, this variant applies to any type of magnetic screw-nut system comprising a screw and a nut able to interact magnetically with each other.

FIG. 45 schematically illustrates a magnetic screw-nut system whose screw has a variable pitch.

Such a system includes:

- a nut 441 capable of rotating or translating around an axis;

- a screw 440 capable of magnetically interacting with the nut 441 and of translating or rotating inside the nut 441 along the axis.

The nut has a constant pitch along its length. The screw has a variable pitch along its length.

In this configuration, the screw has two portions, namely a portion P1 and a portion P2. The pitch of the propellers of the P1 portion is smaller than that of the propellers of the P2 portion. Portion P1 of the screw has the right amount of magnets to transmit the desired forces. The pitch of the P1 portion corresponds to the pitch of the nut.

The P2 portion includes:

- a larger propeller pitch, different from the pitch of part P1 and therefore of the nut. ;

- no or fewer magnets than part P1 (the manufacturing cost is therefore lower).

For a given speed of rotation of the nut, the screw translates at a faster speed by generating lower forces on the portion P2 and at a slower speed by generating greater forces on the portion P1.

Alternatively, for a given translation speed of the screw, the nut rotates faster on portion P2 by transmitting less torque and rotates slower on portion P1 by transmitting more torque.

This variant of the invention therefore makes it possible to generate a system that can operate with a fast approach speed and a slower working speed at the exit for a given speed of the driving element (nut or screw). Other configurations with more than two portions and/or a different distribution of portions are possible.

The magnetic cooperation between the screw and the nut on the P2 portion is certainly degraded compared to the magnetic cooperation of the screw and the nut on the P1 portion. This is not a problem because there is no blockage unlike a mechanical screw-nut where a significant change in pitch causes jamming.

The fact that there are no magnets or fewer magnets on the portion P2 is not a problem for the transmission of the forces because the value of the latter is lower and of less importance, the speed being privileged on this portion P2 contrary to the portion P1 on which the forces to be transmitted are privileged to the speed. When the nut is the rotor of a rotating electrical machine -as shown in figure 40-, the magnetic flux crossing the stator of the electrical machine is lower at the level of the portion P2 and therefore creates a defluxing of the machine. Thus, the intrinsic characteristics of the machine (reduced excitation flux) are modified and its rotor can therefore rotate faster for the same stator supply voltage.

Figure 46 shows a perspective view of an example of a 442 variable pitch screw propeller. In this figure, the smaller pitch portion P1 is longer than that of the larger pitch portion P2. The opposite situation on the lengths could be possible. Similarly, portions P1 and P2 could be of the same length.

The screw could comprise over its length more than two consecutive portions of different pitches, non-consecutive portions possibly having equal pitches. The screw may for example comprise three consecutive portions numbered 1, 2 and 3, portion no. 1 and no. 3 possibly having an identical pitch but portion no. 2 having a different pitch.

Claims (26)

Magnetic screw-nut system comprising:
- A nut capable of rotating or translating around an axis;
- A screw capable of magnetically interacting with said nut and of translating or rotating inside said nut along said axis, an air gap being provided between said screw and said nut;
said nut carrying two helices made of magnetic material extending parallel to each other in a helical manner around said axis, said nut carrying at least one magnet, placed at the outer periphery of said helices, the north pole of said magnet being connected to one of said helices and its south pole being connected to the other of said helices in such a way that said helices are respectively north and south polarized;
said screw carrying two helices made of magnetic material extending parallel to each other in a helical manner around said axis, said screw carrying at least one magnet, placed at the inner periphery of said helices, the north pole of said magnet being connected to one of said helices and its south pole is connected to the other of said helices in such a way that said helices are respectively north and south polarized;
the pitch of said helices of said nut being substantially equal to the pitch of said helices of said screw. System according to Claim 1, in which the said nut and the said screw comprise a plurality of magnets in an even number, the polarities of the successive magnets being reversed. A system according to claim 2 wherein said magnets are substantially uniformly distributed around said axis. A system according to claim 2 or 3 wherein the numbers of magnets of said screw and said nut are equal. System according to Claim 2 or 3, in which the numbers of magnets of said screw and of said nut are different. System according to any one of Claims 1 to 5, in which the said screw and/or the said nut comprises studs made of magnetic material of north polarity and studs of magnetic material of south polarity, each stud of north polarity being in contact with the north polarity end of at least one of said magnets and with the corresponding north polarity helix, and each south polarity pad being in contact with the south polarity end of at least one of said magnets and with the helix of corresponding south polarity. System according to Claim 6, in which each stud is in contact with each winding of the corresponding helix. System according to any one of Claims 1 to 7, in which the said magnets of the said screw and/or of the said nut have ortho-radial magnetization. System according to any one of Claims 1 to 7, in which the said magnets of the said screw and/or of the said nut have radial magnetization. System according to claims 6 or 7 and 8 in which each pad of north polarity is in contact with the north poles of two consecutive magnets and of the windings of the helix of corresponding north polarity, and each pad of south polarity is in contact with the south poles of two consecutive magnets and windings of the helix of corresponding south polarity. System according to claims 6 or 7 and 9 in which each pad of north polarity is in contact with the north pole of a magnet and the windings of the helix of corresponding north polarity, and each pad of south polarity is in contact with the south pole of the magnet and the windings of the helix of corresponding south polarity. System according to any one of Claims 1 to 11, in which an air gap is provided between the contiguous components of different polarity of said nut and of said screw. System according to Claim 6 alone or in combination with any one of Claims 7 to 12, in which each helix and/or each stud comprises recesses shaped respectively at the level of the studs and/or corresponding windings of different polarity to delimit at least partly said air gaps. System according to any one of Claims 1 to 13, in which the surface of the helices of said nut facing said screw has alternating recesses and projections in the direction of said screw. System according to any one of Claims 1 to 14, in which the surface of the helices of the said screw facing the said nut has an alternation of recesses and projections towards the said nut. System according to Claim 14 or 15, in which the recesses and projections of the helices of north polarity of said nut and/or of said screw are angularly offset along said axis from those of the helices of south polarity of said nut and/or of said screw. System according to Claim 16, in which the hollows and projections of the helices of north polarity of said nut and/or of said screw are angularly offset along said axis from those of the helices of south polarity of said nut and/or of said screw so that the salients of north polarity and the troughs of south polarity are aligned along said axis while the salients of south polarity and the troughs of north polarity are aligned along said axis. System according to Claim 14 or 15, in which the recesses and projections of the helices of north polarity of said nut and/or of said screw are aligned along said axis with those of the helices of south polarity of said nut and/or of said screw so that the north polarity prominences and the south polarity prominences are aligned along said axis while the south polarity troughs and the north polarity troughs are aligned along said axis. System according to Claim 6 alone or in combination with any one of Claims 7 to 18, in which the length of the pads along said axis is greater than or equal to that of said magnets along said axis. System according to Claim 6 alone or in combination with any one of Claims 7 to 19, in which the opposite ends of each stud are located respectively essentially in the plane of the ends of the end windings of the helices of said nut and/or of said screw. System according to any one of Claims 1 to 20, in which the said propellers are one-piece or consist of several propeller portions. System according to any one of Claims 1 to 21, in which the pitch of the helices of the said screw is not constant over its entire length. System according to Claim 22, in which the helices of the said screw comprise at least two portions of different pitch. Device for generating electric current comprising an electric generator provided with a rotor and a stator, and a system according to any one of Claims 1 to 23, in which the said nut or the said screw is linked to the said rotor, a translation of the said nut or of said screw inducing a rotation of said rotor and a generation of electric current by said generator. Device for generating a linear displacement comprising an electric motor provided with a stator and a rotor, and a system according to any one of Claims 1 to 23, in which the said nut or the said screw is linked to the said rotor, a rotation of said screw or said nut by means of said motor causing a linear displacement of said nut or said screw. Device according to any one of Claims 24 or 25, in which the magnets of the said nut constitute the magnets of the said rotor.