EP4495711A1 - System for controlling a clock display device - Google Patents

Abstract

A system for controlling a ferromagnetic element comprising a plurality of magnetizable elements capable of being individually activated and deactivated via an electric current such that the activated magnetizable elements act on the ferromagnetic element to form a desired display, characterized in that the magnetizable elements of the plurality of magnetizable elements are juxtaposed along two axes so as to form a square matrix in which the magnetizable elements are arranged in a checkerboard pattern so as to have alternating polarity along the two axes.

Description

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a device, preferably a timepiece display, using an electrical power supply to create magnetic fields capable of moving a ferromagnetic element, preferably a fluid. The present invention further relates to a system for controlling the ferromagnetic element as well as the magnetizable elements included in the system for controlling the ferromagnetic element and their arrangement therein.

STATE OF THE ART

Watch display devices are well known. The best known are obviously mechanical or quartz watch display devices that display the time, date and sometimes other information. However, the disadvantages of these mechanical devices are their often very high price, the complexity of the movements, their fragility as well as the limit concerning the display options. Indeed, in the era of connected watches, users intend to use their wristwatch, for example, as a multimedia object as much as a watch display device.

Smartwatches, for their part, are today more gadgets that go in all directions than real timepieces and consume enormous resources, requiring almost daily recharging.

Between these two extremes, a new type of technology has emerged in recent years in this industry, which is the use of ferromagnetic components with magnets controlling their movement. This technology allows for varying the type of display as well as using few electrical resources.

Several publications have disclosed examples of watch devices using ferromagnetic technology, including: Koelman et al. "From meaning to liquid matters ", " This ferrofluid clock has a mesmeric, magnetic, magical appeal" by Sarang Seth, 10/08/2019 and " This magnetic ink watch makes the journey of time much more visually interesting" by Sarang Seth, 01/06/2021 .

The first publication describes a clock in which individually activatable electromagnets are arranged in a matrix that allows a ferrofluid to be controlled to indicate the time. A disadvantage of this device is that it requires a continuous power supply to activate the magnets, which poses a problem of autonomy. Another disadvantage is the poor quality of the displays because of the weak magnetic fields and the vertical display, which because of an equal magnetic force makes the pixels at the bottom larger than those at the top - heterogeneity due in particular to the positioning of the ferrofluid reservoirs at the bottom of the device.

In the second and third publications, the clockwork device works with magnetic hands that direct the material. The display is controlled by a movement of permanent magnets. A disadvantage of this type of device is that the display is limited to the movement of the magnets which greatly reduces the range of possibilities in terms of display. Another disadvantage is that it requires a mechanism allowing the movement of the magnets which complicates the device.

In order to improve existing devices a new type of magnet was sought.

For example, documents US10971292 , US10759246 And US11380467 describe permanent electromagnets consisting of cylindrical cores, one surrounding the other, whose materials have different magnetic properties (hard and semi-soft or soft), and surrounded by a coil in which a current changes the magnetization with each pulse, the state remaining unchanged until the next pulse.

One of the drawbacks of these publications is that they do not propose a satisfactory arrangement of these electromagnets to reliably control a ferromagnetic component.

However, the publication Fan et al. (2020-PNAS ), Reconfigurable multifunctional ferrofluid droplet robots describes a network of magnets to drive ferrofluid droplets, describing it variously as an electromagnet network or a permanent magnet network. However, in order to optimize the properties of the network, the authors propose a combination of these two types of magnets.

One of the disadvantages of this type of arrangement is that the proposed arrangement, although reliable, provides a deteriorated and binary global magnetic field without the possibility of modulating its strength.

An aim of the present invention is therefore to solve the problems described above, and more particularly to provide a reliable ferromagnetic element control device making it possible to strengthen the magnetic fields created.

Another object of the present invention is to provide a reliable ferromagnetic element control device capable of creating variable magnetic fields.

Yet another object of the present invention is to provide magnetizable elements capable of being used in a reliable ferromagnetic element control device and capable of enhancing the performance of the magnetic fields created.

Finally, yet another aim of the present invention is to provide a watch or robotic device using this control device in an improved manner.

SUBJECT OF THE INVENTION

To this end, a first aspect of the present invention relates to a system for controlling a ferromagnetic element comprising a plurality of magnetizable elements capable of being individually activated and deactivated via an electric current so that the activated magnetizable elements act on the ferromagnetic element to form a desired display, characterized in that the magnetizable elements of the plurality of magnetizable elements are juxtaposed along two axes so as to form a square matrix in which the magnetizable elements are arranged in a checkerboard pattern so as to present alternating polarity along the two axes.

Preferably, the magnetizable elements are permanent electromagnets.

Another aspect of the invention relates to a well arranged to receive a magnetizable element, which can be arranged in the control system described above.

Advantageously, the well is made of a material having a relative magnetic permeance "µ _r " greater than 1, preferably 400 or more. Thus, the well can more easily absorb the field lines instead of air.

Even more advantageously, the well has the capacity to absorb the magnetic flux produced by the magnetizable element.

More particularly, the capacity to absorb the magnetic flux produced by the magnetizable element is the product of the section and the saturation limit B _sat of the well material. Indeed, the thinner the section of the well walls, i.e. its thickness, the higher the saturation limit of the material must be. We observe materials with B _sat more or less equal to 2.4 T, the present invention can for example use a material with B _sat of 1.9 T. Thus the material can be chosen according to its section or vice versa.

Advantageously, the well 61 is such that it makes it possible to reduce the demagnetization effect of the magnetizable element, and therefore to increase its performance by allowing the magnetizable element to reach a third super-activated state in addition to the two activated/deactivated states, where the power of the magnetizable element is increased, when the ferromagnetic element is located above the magnetizable element.

Preferably, the well has a gap between its vertical walls and the magnetizable element, the dimension of which is a function of the size of the magnetic element and the materials used, preferably in the range of 0 to 500 µm.

Another aspect of the invention includes a carrier having a plurality of wells described above provided therein, which may be arranged in the control system described above.

According to a preferred embodiment of the invention, the support has the shape of a plate.

Preferably, each well has two through holes to allow connection wires to pass through to the rear of the bracket.

Advantageously, the support is made of a material designed to guide the magnetic fluxes so as to provide high magnetic permeability.

Preferably, each magnetizable element of the plurality of magnetizable elements is connected to a coil made of an electrically conductive material and arranged to transfer an electrical pulse thereto.

Alternatively, at least one magnetizable element of the plurality of magnetizable elements is made of a magnetoelectric material.

Another aspect of the invention provides the magnetizable element comprising a first magnetizable material having a first coercivity and a second magnetizable material having a second coercivity lower than the first.

Advantageously, the magnetization axis of the electromagnets is axial and the first material is polarized along this axis in a defined direction and the second material has a magnetization axis aligned with that of the first material and the direction of which is likely to change over time via the electric current transmitted by the coil.

Alternatively, the magnetization axis of the electromagnets is axial and the first material and the second material have aligned magnetization axes whose direction is likely to change over time via the electric current transmitted by the coil. According to this alternative embodiment, the "high coercivity" material 11 can also be controlled and it is possible to achieve at least 3 states (up: both polarities are in the same direction towards the ferromagnetic element, down: both polarities are in the same direction away from the ferromagnetic element, off: both polarities are in an opposite direction).

Preferably, when both materials have an axis of magnetization going in the same direction the magnetizable element is activated, while in the opposite direction it is deactivated.

According to a preferred embodiment of the invention, the magnetizable element can reach intermediate magnetization states, with only the intensity and duration of the electric pulse being modified.

Preferably, the first material is neodymium and the second material is AlNiCo.

Advantageously, the polarity direction of the checkerboard arrangement of the matrix is defined by the first material.

Another aspect of the invention concerns the different shapes of the magnetizable elements.

According to a preferred embodiment of the invention, at least one magnetizable element comprises a portion of first peripheral material comprising a bore in which a portion of second material is housed, the two portions being concentric. Alternatively, it may comprise a portion of second peripheral material comprising a bore in which a portion of first material is housed.

Alternatively, at least one magnetizable element comprises the second material in the lower region and a thin layer of the first material on the upper region.

Preferably, the thin layer of the first material is between 0.1 and 500 µm thick. Preferably, the thin layer has a thickness of approximately 75 µm.

Alternatively, at least one magnetizable element comprises the two materials in alternating and/or concentric slices.

Advantageously, each magnetizable element comprises a first magnetizable material having a first coercivity and a second magnetizable material having a second coercivity lower than the first coercivity and in that the polarizations of the two materials are reversed.

According to another aspect, the present invention relates to a timepiece display device comprising a ferromagnetic element housed in a sealed capsule and a system for controlling the ferromagnetic element according to the first aspect. The aims, advantages and particular characteristics of the bracelet object of the present invention being similar to those of the clasp object of the present invention, they are not recalled here.

Advantageously, the ferromagnetic element is housed in a sealed capsule and the control system of the ferromagnetic element is located in the box housed under said sealed capsule.

Advantageously, the waterproof capsule comprises a transparent portion and a portion of the case of the watch display device, fixed in a waterproof manner to each other.

Preferably, the waterproof capsule is detachably mounted on the box.

According to a preferred embodiment of the invention, the timepiece display device comprises a power supply arranged to generate and transfer at least one electrical pulse to the control system of the ferromagnetic element.

Advantageously, the watch display device further comprises a membrane separating the interior volume of the capsule and the control system from the ferromagnetic element.

Preferably, the membrane is functionalized so as to locally increase its magnetic permeability.

Advantageously, the ferromagnetic element is immersed in a second transparent fluid of different phase.

According to a preferred embodiment of the invention, at least a portion of the inner surface of the capsule comprises a hydrophilic or hydrophobic chemical and/or mechanical surface treatment in order to increase the affinity with the solvent, and reduce that with the ferromagnetic element.

According to a second aspect, the present invention relates to a use of a system for controlling a ferromagnetic element according to the first aspect of the invention in a robotic gripping device.

BRIEF DESCRIPTION OF THE FIGURES

• la figure 1 représente un dispositif d'affichage horloger selon la présente invention,
• la figures 2A représente schématiquement une matrice carrée selon la présente invention, les figures 2B et 2C représentent schématiquement plusieurs types de matrices hexagonales alors que les figures 2D et 2E représentent schématiquement plusieurs types de matrices avec des erreurs de fabrication,

• les figures 3A à 3C représentent schématiquement un élément magnétisable selon trois modes de réalisation préférés de la présente invention,
• les figures 4A à 4D représentent un mode de réalisation particulièrement préféré de la présente invention,
• la figure 5 représente une vue en coupe de profil du dispositif d'affichage horloger selon la présente invention,
• les figures 6A à 6D représentent différentes vues de la structure du support de matrice de la présente invention
• les figures 7A à 7D montrent les lignes de champ magnétique générées à quatre étapes d'activation/désactivation de l'élément magnétisable.
• la figure 8 est un graphique représentant illustration de face du champ magnétique en fonction de la taille de l'électroaimant et de l'état d'activation.

Other particular advantages, aims and characteristics of the invention will emerge from the following non-limiting description of at least one particular embodiment of the devices which are the subject of the present invention, with reference to the appended drawings, in which:

• there figure 1 represents a timepiece display device according to the present invention,
• there Figures 2A schematically represents a square matrix according to the present invention, the Figures 2B and 2C schematically represent several types of hexagonal matrices while the Figures 2D and 2E schematically represent several types of matrices with manufacturing errors,

• THE Figures 3A to 3C schematically represent a magnetizable element according to three preferred embodiments of the present invention,
• THE Figures 4A to 4D represent a particularly preferred embodiment of the present invention,
• there figure 5 represents a profile sectional view of the watch display device according to the present invention,
• THE Figures 6A to 6D represent different views of the structure of the die holder of the present invention.
• THE Figures 7A to 7D show the magnetic field lines generated at four stages of activation/deactivation of the magnetizable element.
• there figure 8 is a graph showing the face-on illustration of the magnetic field as a function of electromagnet size and activation state.

DESCRIPTION OF EMBODIMENTS OF THE INVENTION

This description is given without limitation, each characteristic of an embodiment being able to be combined with any other characteristic of any other embodiment in an advantageous manner. It should be noted from now on that the figures are not necessarily to scale.

In general, the invention relates to a timepiece display device 100 shown in the figure 1 . This device can be, for example, a watch.

As depicted in the figure 1 , the timepiece display device 100 of the present invention comprises a ferromagnetic element 101, preferably housed in a sealed capsule 102, and a control system 10 of the ferromagnetic element, preferably housed under the capsule to leave the ferromagnetic element 101 visible. Also, the device comprises a power supply, preferably electrical, arranged to generate and transfer at least one electrical pulse to the control system 10 of the ferromagnetic element.

According to a preferred embodiment described below, the ferromagnetic element 101 is a ferrofluid.

More particularly, the control system 10 of the ferromagnetic element comprises a plurality of magnetizable elements 1 capable of being individually activated and deactivated, via an electric current, preferably an electric pulse, generated by the power supply, to create a magnetic field consisting of field lines intended to act on the ferromagnetic element 101 so that the activated magnetizable elements 1 attract or act on the ferromagnetic element 101 and move it in the capsule 102 so that it forms a desired display. The ferromagnetic element 101 and the control system 10 are separated by at least one wall 104, called a membrane and arranged to minimize its reluctance to the magnetic field. This membrane 104 can be constituted by a wall of the box 105, by a wall of the capsule 102 itself or both or similar.

Preferably the display includes at least one of a traditional style selected from the group including time, date, digital and analog, chronograph, moon phases, and the like, a smartwatch style selected from the group including pulse, position, sports match results, stock price, weather, and the like, a futuristic style selected from the group including interaction with its environment, reaction to noises, sounds, voice control, movement of ferrofluid by thought, and the like.

First, the control system 1 of the ferromagnetic element will be described in detail with reference to the Figures 2 to 4 .

The magnetizable elements 1 of the plurality of magnetizable elements are preferably placed side by side in a layer in the case 105 of the timepiece device 100, under the capsule 102 enclosing the ferromagnetic element 101. However, a different arrangement can be provided if this allows the control system 10 to act on the position of the ferromagnetic element 101 adequately while allowing the display to appear.

As previously stated, each magnetizable element 1 among the plurality of magnetizable elements can be individually activated/deactivated via an electric current. These magnetizable elements 1 are preferably electromagnets, preferably permanent electromagnets, arranged juxtaposed so as to constitute a matrix 2. As shown in the figure 1 , they are preferably arranged vertically, that is to say oriented towards the ferromagnetic element 101 so as to generate a maximum magnetic field on the ferromagnetic element 101.

Two geometries of juxtaposition, or matrix 2, of magnetizable elements 1 are possible: a so-called square matrix represented in Figure 2A and a so-called hexagonal matrix represented in the Figure 2B and to the Figure 2C .

It is important to note that the term square matrix in this context refers to a matrix having n rows arranged along an X axis and m columns arranged along a Y axis substantially perpendicular to X but that n is not necessarily equal to m for example m or n may be equal to 1 and the other of m or n may be greater than 1. Furthermore it should be noted that depending on the precision of manufacture some elements of the matrix may overflow or be missing this is shown in the Figures 2D and 2E .

Generally speaking, the square matrix structure is defined by an average number of direct neighbors of four, while the hexagonal matrix structure has an average of 6. Alternatively, a square matrix according to the present invention can be understood as a structure that can be constructed by placing the geometric center of the elements in an orthogonal (and not orthonormal) grid, with at most one element per tile. This aspect is shown in Figures 2C to 2E where the Figure 2C shows a hexagonal matrix and the Figures 2D and 2E represent a square matrix, or portion of a matrix, according to the present invention. The hexagonal matrix has magnetizable elements arranged in a staggered pattern.

The hexagonal matrix seems at first sight ideal, since it is more compact. However, with this geometry, it is impossible not to juxtapose two magnetizable elements 1 of similar polarity. In this case, the inventors discovered that the juxtaposition of two magnetizable elements of similar polarity degrades the operation, in aesthetics and especially in performance of the matrix 2 and that it is preferable to arrange the magnetizable elements 1 of so as to alternate their polarity, in particular the polarity of the first material with high coercivity as explained below, and therefore that a square or rectangular geometry allowing an arrangement of the magnetizable elements 1 in a checkerboard pattern according to their polarities is preferable for the operation of the control system 10 and this despite the greater bulk.

It is worth noting that the empty space between the magnetizable elements 1 in the square geometry can subsequently be functionalized by incorporating a material that guides magnetic fluxes so as to provide high magnetic permeability. This will be presented below.

THE Figures 6A to 6D represent a preferred embodiment of a matrix 2 support 6 for use in the control system 10 of the present invention.

There Figure 6A is a sectional view along the AA axis indicated on the Figure 6B . There Figure 6B is a front view. The Figure 6C is an enlargement of zone B of the Figure 6B and the Figure 6D is a perspective view.

As can be seen in these figures, the support 6 has a multitude of wells 61 arranged to receive the magnetic elements 1 and coils. Each well 61 has two through holes 62 allowing the connection wires to pass towards the rear of the support 6.

We can clearly see the arrangement of the wells 61 in a square matrix and not a hexagonal one. It should be noted that this support 6 preferably has the shape of a plate.

Having presented the array 2 of magnetizable elements 1, we will now describe the magnetizable elements 1 themselves. It should be noted that the magnetizable elements 1 below are presented in the context of the display control system but that the present invention also relates to the various embodiments of the magnetizable elements as such.

As briefly described above, the magnetizable elements 1 are magnets, preferably permanent electromagnets with controlled magnetization. individually between an on state and a off state. Each magnetizable element comprises two magnetizable materials.

The first material 11 has a high first coercivity, for example neodymium, and the second material 12 has a lower second coercivity, for example AlNiCo.

Each magnetizable element 1 is connected to a coil made of an electrically conductive material arranged to receive the electric current from the power supply and to activate/deactivate the magnetizable element 1 via the electric current that it transmits to it, for example by contact by surrounding it. A pulse of electric current in a coil is converted by the latter into a magnetic field pulse. This short magnetic pulse is capable of modifying the orientation of the magnetic field of the magnets if it is sufficiently intense. The magnetic field produced by the coil is maximal and relatively constant at its center. Its duration is equal to that of the electric pulse, i.e. approximately 1 µs to 100 µs.

The magnetization axis of the electromagnets 1 is axial and the first material 11 is polarized along this axis in a defined direction which is no longer modified. The second material 12 has a magnetization axis aligned with that of the first material 11, but its direction is likely to change over time via the electric current transmitted by the coil.

Thus, when the two materials have an axis of magnetization going in the same direction, it is said to be activated, while in the opposite direction it is deactivated. Note that it is possible to reach intermediate states of magnetization, with the only modification being the intensity and duration of the electric pulse.

Note, as explained above, that in the checkerboard distribution of electromagnets 1 according to their polarity, it is indeed the magnetization axis of the first material 11 which is taken into account.

According to an alternative embodiment, the "high coercivity" material 11 can also be controlled if the current pulse of the coil is sufficiently strong. In this case it is possible to reach 3 states (up: both polarities are in the same direction towards the ferromagnetic element, down: the two polarities are in the same direction away from the ferromagnetic element, off: the two polarities are in the opposite direction) which allows more flexibility on animations with the ferrofluid, because it becomes possible in particular to push it back for a short moment.

The method for controlling the switching of each magnetizable element 1 preferably comprises a step of determining whether said magnet is magnetized or not followed by a step of determining whether said magnet should be magnetized or not. Based on the results, if the current magnetization is different from the desired magnetization, a switching step is implemented in which an electrical pulse is sent to the coil of the magnetizable element. Preferably, the electrical pulse has a first direction if the magnet is to be activated and therefore switch from the non-magnetized state to the magnetized state and a second direction if the magnet is to be deactivated and therefore switch from the magnetized state to the non-magnetized state and has an intensity greater than a threshold value.

The method of controlling the control system repeats, preferably simultaneously, the steps of the switching method described above for each magnetizable element 1 of the network depending on a selected display. For this purpose, it comprises two previous steps which consist in determining the image to be displayed by the ferromagnetic fluid 101 and choosing which magnetizable elements of the control system of the ferromagnetic element must be activated and which magnetizable elements must be deactivated to move the ferromagnetic fluid to display the determined image.

Three types of magnetizable elements 1 have been designed, but all are based on the characteristic presented above according to which they combine a strong permanent magnet 11, therefore a first material of high coercivity, for example greater than 200kA/m and a semi-hard or soft permanent magnet 12, therefore a second material of medium or low coercivity, respectively for example less than 200kA/m and 1 kA/m.

When the magnet tends towards a flattened shape, which is desired in order to limit the thickness of the watch device, it undergoes an intrinsic demagnetizing field, linked to the bringing the poles of the magnet closer together. The higher its coercivity, the more it is able to resist it, and therefore to produce a high magnetic field despite its disadvantageous flattened shape. Furthermore, a material with a high coercivity tends to orient the field lines in its vicinity more easily. In return, it requires a large amount of energy to allow its polarization to change. The principle of this aspect of the invention is therefore to combine these two materials with different coercivities in order to produce a miniature, low-consumption, high-performance magnetizable element.

The three types of magnets are presented in the Figures 3A to 3C . It should be noted that all have a cylindrical shape which is preferable but is not necessary for the operation of the magnetizable element. Also note that the coil is not shown.

The first assembly represented in Figure 3A is the simplest. It comprises a first peripheral magnet, preferably a semi-hard or soft magnet, comprising a bore in which is housed a second magnet, preferably a hard magnet. The central symmetry is important so the two magnets must be concentric. Their preferred axes of magnetization are aligned and the direction of magnetization is sometimes identical, sometimes opposite depending on the order, thus, the polarization of the semi-hard or soft magnet compensates or increases the field produced by the hard magnet.

The assembly shown in Figure 3B consists of a semi-hard or soft magnet in the lower region and a thin layer of hard magnet on the upper part with a thickness of between 0.1 and 500 µm. Preferably, the thin layer has a thickness of about 75 µm. This layer serves to tighten and reorient the field lines of the semi-hard or soft material.

The 3C assembly is composed of two materials in alternating slices. One is a hard magnet, the other is a semi-hard or soft magnet. It takes advantage of the geometry of the layers, which have the effect of reducing the intensity of the demagnetizing field. Other geometries are therefore also possible, in particular in concentric thin layers.

The assemblies represented in Figures 3B and 3C present a priori numerous advantages compared to assembly in Figure 3A , particularly to be functional over a wider range of dimensions.

In addition to this, it is noted that according to a preferred embodiment of the invention independently of the matrix and the type of magnetizable element, each magnetic circuit, i.e. the magnetizable element 1 and its coil, can be partitioned. That is, referring to the figure 4 which only represents the magnet 1 without the coil as a center element for clarity, that the magnetizable element 1 is taken at the center of a U-shaped element, such as a well 61 preferably a well 61 of the support 6, shown in figures 6 , when viewed in profile section. The well 61, or at least its walls, for example the support 6, is preferably made of a material with high magnetic permeance, which easily conducts magnetic fields.

This well 61 has several effects. On the one hand it allows to reduce the demagnetization effect of the magnetizable element, and thus to increase its performance. On the other hand it allows the magnetizable element to reach a third state in addition to the two activated/deactivated states, where the power of the magnetizable element is increased, like a kind of super activated state. This can be used for various purposes, including to lock the position of the ferromagnetic element.

This feature is presented in the Figures 7A to 7D and in the figure 8 .

There Figures 7A to 7D show the field lines and thus the strength of the magnetic field at different times.

There Figure 7A represents the field created when the magnet is deactivated. We can see that it is not powerful and is confined by the well.

There Figure 7B represents the field created when the magnet is activated. We can see that it has increased so as to attract the ferromagnetic element.

There Figure 7C represents the field created when the magnet is activated and when the ferromagnetic element has come to position itself on it. This is the super-activated state. It is a consequence of the matrix and well 61 which concentrates the magnetic flux.

There Figure 7D represents the field created when the magnet is deactivated when the ferromagnetic element has come to position itself on it. We see in fact that this one is not powerful and confined by the well. This is the end of the super-activated effect.

THE Figures 7A to 7D are in chronological order upon activation.

Returning to the super-activated or super-magnetized state, this phenomenon is generally due to the ratio between the length and the diameter of the magnet. Indeed, when the two poles of a cylindrical magnet are far apart, the super-magnetized effect is almost constant. On the other hand, in the case of a flat or thin magnet as here to limit the thickness of the system, this effect is not automatic and it is the presence of the well 61 (or the support 6 which includes the well 61) which during the interaction with the ferromagnetic element makes it possible to reach this state and therefore to provide a stronger magnet in a reduced volume.

This is also illustrated on the figure 8 , which shows the super activated state versus the activated state.

Finally, well 61 plays a protective role, confining the flow within its enclosure, and reducing the magnetic field under magnetizable element 1 to virtually zero.

Indeed, the challenge is to increase the flux lines R, which have the function of attracting magnetic elements, and reduce the leakage fluxes S, which degrade the performance of the magnetizable element 1 as shown in the Figures 4B to 4D .

Preferably, the well 61 has a gap, between its vertical wall and the magnetizable element located in the center, the dimension of which is a function of the size of the magnetic element 1 and the materials used. Preferably, the dimension is between 0 and 500 µm, preferably between 300 and 400 µm, ideally the dimension corresponds to approximately 1/3 of the diameter of the magnet.

It could also be considered to introduce materials or mechanisms that reduce S-leakage, for example diamagnetic materials that have a repulsive effect on magnetic fields. More simply, this area contains the coil that controls the state of magnetization of the magnetizable element.

Advantageously, the well 61, or at least its walls, therefore for example the support 6, is made of a material having a relative magnetic permeance "µ _r " greater than 1, preferably 400 or more. Thus, the well 61 can more easily absorb the field lines instead of air. Also, the well 61 has a capacity to absorb the magnetic flux produced by the magnetizable element 1. More particularly, the capacity to absorb the magnetic flux produced by the magnetizable element 1 is the product of the section and the saturation limit B _sat of the material of the well 61. Indeed, the thinner the section of the walls of the well 61, that is to say its thickness, the higher the saturation limit of the material must be. Materials with B _sat > 2.5 T are observed, the present invention can for example use a material with B _sat of 1.9 T. Thus, the material can be chosen according to its section or vice versa. Accessing the boost state implies the presence of ferromagnetic element in the vicinity of the magnetizable element, and can be used for measurement purposes.

Regarding the magnetic circuit, comprising magnet 1 and the coil, it should be noted that there is a class of materials called magnetoelectric materials whose electrical and magnetic properties are linked. This implies in particular that it is possible to control their magnetic polarization by means of an electric field. This would have the advantage of being able to do without the copper coil, while preserving the low consumption of the system.

We will now describe the upper portion of the timepiece display device 100, namely the capsule 102 and the ferromagnetic element 101 located inside.

The ferromagnetic element 101 is housed in the capsule 102 which is preferably arranged on the control system 10. This capsule 102 therefore has a sealed housing in which the ferromagnetic element 101 is preferably immersed in a second transparent fluid (solvent) of phase different 103. Indeed, the ferromagnetic element 101 can exist in organic or aqueous form, the solvent is then of the opposite phase and a hydrophilic or hydrophobic chemical and/or mechanical surface treatment is preferably carried out in order to increase the affinity with the solvent, and reduce that with the ferromagnetic element 101 to prevent it from sticking to the capsule 102.

The capsule 102 has a transparent upper portion revealing the ferromagnetic element. According to a first embodiment, this upper portion is fixed in a sealed manner to the case 105 so that the capsule is partly constituted by an external surface of the case, preferably the membrane 104. Alternatively, the capsule may be an element attached to the case which comprises a lower portion in contact with the timepiece device. In this latter embodiment, the capsule is likely to be detachable.

It should be noted that in order to increase the performance of the control system and therefore of the display, it is preferable to reduce as much as possible the distance and/or the reluctance between the ferromagnetic element and the control system. Thus, the membrane which separates the interior of the capsule from the display control system must have a minimum thickness.

It can also be functionalized to improve the system's performance. In this case, it is a question of locally increasing its magnetic permeability, in order to better conduct magnetic fields. A membrane with a high but uniform magnetic permeability on its surface would degrade the system's performance.

In addition to the systems and features described above, it is possible to add different sensors depending on the desired properties. It is also possible to provide for the ability to control each magnetizable element in all intermediate states between 'ON' and 'OFF' using additional information on their polarization.

Although aspects of the invention have been described in conjunction with a number of embodiments, it is apparent that numerous alternatives, modifications and variations would be or are apparent to those skilled in the art. Accordingly, this disclosure is intended to encompass all such alternatives, modifications, equivalents and variations that are within the scope of this disclosure. This is particularly the case, for example, with respect to the different materials used and the production processes of the different parts.

Furthermore, by using the same ferromagnetic element control system in the lower part of the timepiece device, other types of displays can be imagined, to the extent that a magnetic phenomenon governs them, for example balls controlled by the magnetizable element matrix, shutters on a pivot, a fluid that changes color depending on the intensity of the applied magnetic field, a membrane that deforms visually or functionally on the effect of the matrix.

Claims (15)

A control system (10) for a ferromagnetic element (101) comprising a plurality of magnetizable elements (1) capable of being individually activated and deactivated via an electric current such that the activated magnetizable elements (1) act on the ferromagnetic element (101) to form a desired display, characterized in that the magnetizable elements (1) of the plurality of magnetizable elements are juxtaposed along two axes so as to form a square matrix (2) in which the magnetizable elements (1) are arranged in a checkerboard pattern so as to have alternating polarity along the two axes. Control system for a ferromagnetic element according to claim 1, characterized in that the magnetizable elements (1) are permanent electromagnets. Control system for a ferromagnetic element according to any one of claims 1 or 2, characterized in that it further comprises at least one well (61) arranged to receive each magnetizable element (1). Control system for a ferromagnetic element according to claim 3, characterized in that the well (61) is made of a material having a relative magnetic permeance greater than 1. Control system for a ferromagnetic element according to any one of claims 3 or 4, characterized in that the well (61) has a gap between its vertical walls (6) and the magnetizable element (1) of a distance in the range from 0 to 500 µm. Control system for a ferromagnetic element according to any one of claims 3 to 5, characterized in that it comprises a support (6) in which said at least one well (61) is provided. Control system for a ferromagnetic element according to claim 6, characterized in that the support (6) has the form of a plate. Control system for a ferromagnetic element according to any one of claims 6 or 7, characterized in that each well (61) has two through holes (62) allowing connection wires to pass towards the rear of the support (6). Control system for a ferromagnetic element according to any one of claims 6 to 8, characterized in that the support (6) is made of a material arranged to absorb and/or guide the magnetic fluxes so as to provide high magnetic permeability. A system for controlling a ferromagnetic element according to any one of claims 1 to 9, characterized in that each magnetizable element (1) comprises a first magnetizable material (11) having a first coercivity and a second magnetizable material (12) having a second coercivity lower than the first. Control system for a ferromagnetic element according to claim 10, characterized in that the magnetization axis of the electromagnets (1) is axial and the first material (11) is polarized along this axis in a defined direction and in that the second material (12) has a magnetization axis aligned with that of the first material (11) and the direction of which is likely to change over time via the electric current transmitted by a coil. Control system for a ferromagnetic element according to claim 10, characterized in that the magnetization axis of the electromagnets (1) is axial and the first material (11) and the second material (12) have aligned magnetization axes whose direction is likely to change over time via the electric current transmitted by a coil. A system for controlling a ferromagnetic element according to any one of claims 10 to 12, characterized in that when the two materials (11, 12) have a magnetization axis going in the same direction the magnetizable element (1) is activated, while in the opposite direction it is deactivated. Control system for a ferromagnetic element according to any one of claims 10 to 13, characterized in that the direction of polarity of the checkerboard arrangement of the matrix (2) is defined by the first material (1). Clock display device (100) comprising a ferromagnetic element (101) housed in a sealed capsule (102) and a control system (10) of the ferromagnetic element according to any one of claims 1 to 14.

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