EP4113219A1 - Method for frequency tuning of an assembly of plates of a watch, and watch comprising the assembly of tuned plates - Google Patents

Abstract

The present invention relates to a frequency tuning method for a set of plates (4, 5) of a watch (1). The plates are arranged one above the other forming a watch dial with a space defined between the plates. A mechanical shock is generated on all of the plates, and the vibration frequency of each plate is checked. A vibration frequency adaptation of at least one of the plates is carried out if different from the other plate so as to obtain an identical vibration frequency for each plate to tune the plates at least according to the first natural mode of vibration so as to avoid any contact between the plates following any mechanical shock.

Description

The invention relates to a method for frequency tuning a set of plates of a watch. The plates are preferably watch dial plates. The plates can also be used as acoustic radiation membranes of a striking or musical watch.

The invention also relates to a watch comprising the set of plates tuned according to the tuning method.

Prior art

In the case of a watch fitted with superimposed plates as a watch dial, great care must be taken to avoid any mechanical shock to the watch liable to have contact between the superimposed plates, which could lead to breakage or crack in one of the plates made of a fragile material. Generally, the plates are sufficiently spaced from each other to avoid any contact against each other following a mechanical shock. However, the fact of spacing the plates sufficiently apart is not suitable for assembly in a traditional watch case, since a great deal of space is lost for the assembly of the various components.

In a watch, a striking mechanism may also be provided to generate a sound (note) or music. To do this, the gong of the striking watch or the keyboard of the musical watch are generally arranged in the watch case. Thus the vibrations of the gong or of the blades of the keyboard are transmitted to the various covering parts. These covering parts are for example the middle part, the bezel, the crystal and the back of the watch case, or even a dial with plates superimposed provided with a decoration for an aesthetic aspect of the watch.

In the case of a musical or striking watch, the acoustic efficiency, on the basis of the complex vibro-acoustic transduction of the casing parts, is low. To improve and increase the acoustic level perceived by the user of the striking or musical watch, account must be taken of the material, the geometry and the boundary conditions of the covering parts. The configurations of these casing parts are also dependent on the aesthetics of the watch and the operating constraints, which can limit the possibilities of adaptation.

The frequency content of the sound of a striking or musical watch must be rich in a frequency interval between 0.5 kHz and 5 kHz or even 10 kHz. Traditional trim parts do not allow effective radiation in this frequency band. Thus, in order to be able to further improve the vibro-acoustic performance of the striking mechanism, provision is made for arranging one or more membranes in the watch case, for example one on top of the other with a space separating them. The membranes are sized and configured so that the note or notes generated in the watch case are radiated effectively. The frequencies of the generated notes must be close to the proper modes of vibration of the membranes so that they enter into resonance. On the other hand, nothing is generally provided concerning the frequency tuning of these membranes, in particular so that they do not come into contact with each other, mainly during a mechanical shock of the watch or also during the generation of a note or music.

The constraints relating to the arrangement of acoustic membranes are generally in contrast with the rules of mechanical construction making it possible to guarantee watertightness, as well as the mechanical resistance of the watch to shocks and to significant external pressures.

The patent application EP 1 795 978 A2 describes a watch, which includes a striking device. This striking device comprises two bell-shaped membranes, which are held in the watch case coaxially with one another by central support rods. There is also provided between the two bells and the back of the watch case, another thin membrane stretched and fixed between the middle part and the pierced back of the watch case. Depending on an adjustment of the radial tension of the other membrane, it is possible to adjust the acoustic radiation frequency of this membrane. On the other hand, the two other bell-shaped membranes are not arranged to improve the acoustic level of the sound generated by the ringing device, which constitutes a drawback. Furthermore, no frequency tuning is sought by a frequency tuning process to improve the resistance to mechanical shocks that the watch can undergo.

The patent application EP 3 009 894 A1 describes an acoustic radiation membrane arrangement for a striking or musical watch. The arrangement includes a first membrane disposed overlying a second membrane. Peripheral edges of the two membranes are intended for holding the membranes in a watch case. The first acoustic radiation membrane is configured to effectively radiate frequencies in a first frequency band, while the second acoustic radiation membrane is configured to effectively radiate frequencies in a second frequency band different from the first frequency band. A spacer ring is further disposed between the peripheral edges of the first and second membranes to define an acoustic cavity. Nothing is provided for effecting a frequency tuning of the membranes so that they do not come into contact with one another following activation of the gong or of the blades, or mainly following a mechanical shock.

Summary of the invention

The object of the invention is therefore to overcome the drawbacks of the aforementioned state of the art by proposing a frequency tuning method for a set of plates of a watch, in particular forming a dial of a watch so as to resist the mechanical shocks of the watch, which can be a striking or musical watch.

To this end, the invention relates to a method for frequency tuning a set of plates of a watch, which comprises the characteristics of independent claim 1.

Particular steps of the method for frequency tuning a set of plates of a watch are defined in dependent claims 2 to 10.

An advantage of the frequency tuning method for a set of plates of a watch lies in the fact that at least two plates forming a dial can be tuned to improve their resistance to mechanical shocks. Preferably, each plate forming a dial can also act as an acoustic radiation membrane for a striking or musical watch. Each plate is tuned in frequency, in particular by controlling for example the first natural mode of vibration. The two plates, spaced apart from each other by a relatively small defined distance, are therefore tuned in such a way as not to come into contact against each other following a mechanical shock to the watch. Following the frequency tuning of the plates, one of the plates of which is made of fragile material, such as sapphire, the two plates are likely to vibrate in phase so as not to come into contact against each other during a mechanical shock. It can also be used to improve the acoustic radiation of a note or music generated by the striking or musical watch.

Advantageously, a first dial plate is made of metallic material, while a second dial plate is made of sapphire, which is a brittle and brittle hard material. In the watch case, the sapphire plate can be of a thickness equal to 0.4 mm, or even less.

Advantageously, the sapphire plate can act as a second dial making it possible to introduce new aesthetic codes or it can also act as a vibrating and radiating membrane in cooperation with the first dial plate in the case of a striking watch or musical.

To this end, the invention also relates to a watch comprising the set of plates tuned according to the tuning method, which includes the characteristics of independent claim 11.

Brief description of figures

• la figure 1 représente une coupe transversale d'une montre par exemple à sonnerie ou musicale avec un ensemble de plaques formant cadran et espacées l'une de l'autre et accordées en fréquence pour améliorer la résistance aux chocs mécaniques selon l'invention,
• la figure 2 représente une coupe transversale de la déformée du premier mode propre d'au moins une plaque de l'ensemble de plaques formant cadran selon l'invention,
• les figures 3a et 3b représentent deux graphiques de l'ensemble de plaques formant cadran en vibration suite à un choc mécanique ou lors d'une sonnerie ou d'une musique avant et après l'accordage fréquentiel de l'ensemble de plaques selon l'invention, et
• la figure 4 représente un modèle numérique pour la détermination de fréquences de vibration et l'accordage fréquentiel de l'ensemble de plaques d'une montre selon l'invention.

The aims, advantages and characteristics of the frequency tuning method of a set of plates forming a dial of a watch will appear better in the following description, in particular with regard to the drawings in which:

• the figure 1 represents a cross section of a watch, for example a chiming or musical watch, with a set of plates forming a dial and spaced apart from each other and tuned in frequency to improve the resistance to mechanical shocks according to the invention,
• the picture 2 represents a cross section of the deformation of the first natural mode of at least one plate of the set of plates forming a dial according to the invention,
• them figures 3a and 3b represent two graphs of the set of plates forming a dial in vibration following a mechanical shock or during a ringing or music before and after the frequency tuning of the set of plates according to the invention, and
• the figure 4 represents a digital model for the determination of vibration frequencies and the frequency tuning of the set of plates of a watch according to the invention.

Detailed description of the invention

In the following description, all the well-known parts of a watch, for example a striking or musical watch, will only be briefly described. Reference will be made exclusively to the method of frequency tuning a set of plates of a watch to improve the resistance to mechanical shocks that the watch and the set of plates can withstand.

The figure 1 schematically represents a cross section of a watch 1 provided with a set of plates 4, 5 forming a dial in this embodiment. The watch 1 also comprises a case composed of a middle part 2 closed on an upper side by a glass 3 and on a lower side by a back 8. The watch movement 7 is located between the back 8 and the assembly forming the dial 4, 5. Hands 6 for indicating the time are connected to the watch movement 7 and come out of the set of plates 4, 5 to indicate the time on a dial 5 of the set of plates forming the dial.

Of course, it must be understood that the set of plates can be located in another place in the watch case, necessarily using it as a set of plates forming a dial. It may be two plates spaced apart from each other forming part of the middle part 2 of watch case, or part of the bottom 8 of the watch case, for example, or another part of the watch case.

The set of plates 4, 5 forming a dial comprises a first dial plate 4 for example made of a metallic material and above this first dial plate 4, a second plate 5 of fragile hard material, for example made of sapphire or other brittle material. Preferably, the second plate 5 is substantially transparent so as to be able to view the aesthetic inlays or indexes on the lower surface of the second plate 5, or even also on the upper surface of the first plate 4.

The two plates 4, 5 are mounted spaced from each other by a defined distance. For example, a distance equal to or less than 1 mm can be provided between the two plates 4, 5. Preferably, the distance separating the plates 4, 5 can be much less than 1 mm, for example 0.1 mm for the purpose not to lose too much space in the watch case 1. However, the plates 4, 5 remote from each other must be configured so as not to come into contact with each other during mechanical shocks. A frequency tuning process is therefore carried out in order to be able to adapt the vibration frequency to at least the first natural mode of vibration of one and the other of the plates 4, 5 as discussed in the remainder of the description.

It should be noted that during a mechanical shock, the elements which constitute the casing and the movement of the watch 1 undergo strong accelerations. The set of plates 4, 5 forming the dial, under this acceleration, deforms and can potentially come into contact with the neighboring parts such as for example the hands 6. In the particular case of the construction of the present invention, a sapphire plate 5 can be added spaced to a dial plate 4 for aesthetic codes and can come into contact with the dial plate 4 during a mechanical shock. Depending on the casing drop height, the first dial plate 4 of the assembly can come into contact with the second sapphire plate 5, which can cause this second sapphire plate 5 to break, as it is a fragile material. To guarantee resistance to mechanical shocks of the watches, which include the set of plates 4, 5, it is necessary to correctly dimension all the elements which make up the watch. However, the aesthetics of the watch generates constraints, which are sometimes incompatible with a construction guaranteeing good mechanical resistance during a mechanical shock.

• Augmenter la raideur de la première plaque cadran 4 pour éviter qu'elle se déforme. La première plaque cadran 4 est un élément esthétique, décoré et souvent réalisé avec des matériaux nobles et très denses. Il est donc nécessaire que la première plaque cadran 4 ait une épaisseur conséquente pour éviter qu'elle ne se déforme. Cependant, cela augmenterait l'épaisseur totale de l'habillage ce qui n'est pas souhaité.
• Augmenter l'ébat entre la première plaque cadran 4 et la seconde plaque saphir 5. La première plaque cadran 4 pourrait se déformer lors du choc mécanique sans pour autant rentrer en contact avec l'autre seconde plaque 5 qui vibrerait aussi. L'augmentation de la distance entre la première plaque cadran 4 et la seconde plaque saphir 5 joue directement sur l'épaisseur de l'habillage et sur l'esthétique de la montre. La lisibilité du cadran pourrait aussi être péjoré.
• Accorder les fréquences propres de la première plaque cadran 4 et celles de la seconde plaque 5 en saphir pour que la première plaque cadran 4 et la seconde plaque saphir 5 vibrent en phase et ne s'entrechoquent pas sans augmenter l'ébat entre les deux éléments fixés par le design.

Sapphire being a fragile material, it is preferable to avoid any direct impact on this type of material. In the watch 1 with a set of plates 4, 5, and to avoid any contact between the two plates 4, 5, there are several possibilities, which are:

• Increase the stiffness of the first dial plate 4 to prevent it from deforming. The first dial plate 4 is an aesthetic element, decorated and often made with noble and very dense materials. It is therefore necessary for the first dial plate 4 to have a substantial thickness to prevent it from deforming. However, this would increase the overall thickness of the skin which is not desired.
• Increase the play between the first dial plate 4 and the second sapphire plate 5. The first dial plate 4 could be deformed during the mechanical shock without however coming into contact with the other second plate 5 which would also vibrate. The increase in the distance between the first dial plate 4 and the second sapphire plate 5 has a direct effect on the thickness of the casing and on the aesthetics of the watch. The readability of the dial could also be impaired.
• Tuning the natural frequencies of the first dial plate 4 and those of the second sapphire plate 5 so that the first dial plate 4 and the second sapphire plate 5 vibrate in phase and do not collide without increasing the movement between the two elements set by design.

It should be noted that the present invention is mainly based on the last point of the list cited above. A digital model has therefore been developed to predict the dynamics of the first dial plate 4 and of the second sapphire plate 5 during a shock to the casing. The first dial plate 4 and the second sapphire plate 5 are represented by mass-spring-damper systems as shown in figure 4 described below (modeling the deformation of the first natural mode of the first dial plate 4 and that of the second sapphire plate 5). The two masses are separated from each other by a clearance imposed by the construction ( figure 4 ).

The figures 3a and 3b represent the graphs relating to the frequency tuning process of the plates of the assembly before and after the frequency tuning operations. The picture 3a represents the state before frequency tuning, while the figure 3b represents the state after frequency tuning. The vibration of the first plate is shown in solid lines, while the vibration of the second plate is shown in broken lines.

For the frequency tuning process, the vibration of each plate 4, 5 is checked following a mechanical shock generated by a test device on which the plate or plates 4, 5 are placed superimposed one above the another with a determined space between the two plates. Depending on the vibration of each plate, it can be seen whether one plate comes into contact with the other plate, which is the case shown in picture 3a . The mechanical shock occurs at time T=0. Since the mechanical shock, each plate 4, 5 vibrates or oscillates at a frequency depending the dimensions of the plate, the shape of the plate, the material of which it is made. Note that the first metal plate oscillates at a frequency slightly higher than 1 kHz, while the second sapphire plate oscillates at a frequency higher than the vibration frequency of the first plate and slightly higher, for example above 2 kHz. with vibration attenuation for either plate over time. It can be seen that with these differences in vibration the second plate comes directly into contact with the first plate (darker parts on the picture 3a ) and subsequently by point contacts shown by dots which is likely to cause points of breakage of the second plate made of fragile material. After a frequency analysis of the vibration of each plate by the test device, it is possible to determine the means of correction of each plate or of at least one of the plates so as to arrive at an in-phase vibration of the two plates in vibration. In this case, once the plates vibrate at a substantially equivalent frequency, they are therefore in phase according to at least the first natural mode of vibration without contact against each other as shown in figure 3b .

As a reminder, following this step of the process shown in picture 3a where the plates contact each other, a configuration of at least one of the plates is required. At least one of the plates must be configured or adapted, so that it vibrates at the vibration frequency of at least a first natural mode of vibration of the other plate. Thus, following a mechanical shock imposed on the plates 4, 5, the two plates adapted in vibration frequency in particular according to at least the first natural mode of vibration no longer come into contact against each other, which makes it possible to protect the second plate 5 made of fragile material as shown in figure 3b .

For the adaptation of the vibration frequency of the plates, it can be provided to act on at least one of the plates by adding a mass to it. a determined position, for example in its center, to have the same deformation in phase as the other vibrating plate. The added mass can be driven into the center of the second plate. It can also be imagined to add several small weights at different places of the plate.

It is still conceivable to modify the stiffness or boundary conditions of the set of plates or of at least one of the plates to avoid any contact of each plate against each other following a mechanical shock. Of course, instead of adding a mass or modifying the stiffness, it can also be provided to act on one of the plates by means of a laser to carry out a local engraving or removal of material to modify the vibration frequency up to to have a frequency of vibration at least of the first modes of equal vibration for the two plates. Thanks to this, it is possible to space the two plates by a small defined distance, for example 0.1 mm from each other, while ensuring that they do not come into contact against each other. another following a mechanical shock.

It should be noted that for the configuration of one or other of the plates 4, 5, a developed digital model can be used ( figure 4 ) implemented in the test apparatus and capable of determining the adaptation means for tuning one of the plates in frequency. Of course, several successive steps of controlling the frequency of vibration of each plate can be imagined in order step by step to configure at least one of the plates in order to obtain, at the end of the method, a vibration in phase of the two plates.

It is necessary to characterize the natural frequencies of the dial and those of the sapphire plate (because they depend on the manufacturing tolerances of these components) to adjust the mass added to the center of the sapphire plate on a case-by-case basis.

The frequency test apparatus for the frequency tuning of the method will not be described in more detail, since the elements making up the apparatus are already known for other fields.

As specified above, the set of plates forming a dial can also serve as acoustic radiation membranes of a striking or musical watch and for which it is sought to tune said plates or membranes so that they vibrate in phase without coming into contact with each other.

By way of illustration, the figure 2 represents just a section of the deformation of at least the first eigenmode of the first dial plate 4. Of course it could also have been illustrated the deformation of the first eigenmode of the set of plates 4, 5 or higher eigenmodes .

From the description which has just been given, several variants of the frequency tuning method of a set of plates of a watch can be designed by those skilled in the art without departing from the scope of the invention defined by the claims.

Claims (11)

Method for frequency tuning a set of plates (4, 5) of a watch (1), characterized in that the plates are arranged one above the other with a defined space between the plates, and in that that a mechanical shock is generated on all of the plates, in that a control of the vibration frequency of each plate is carried out, and in that a vibration frequency adaptation of at least one of the plates is carried out if different from the other plate so as to obtain an identical vibration frequency for each plate to tune the plates at least according to the first natural mode of vibration so as to avoid any contact between the plates following any mechanical shock. Method for frequency tuning a set of plates (4, 5) according to claim 1, for which the set of plates forms a watch dial (1), with at least a first dial plate (4) and a second plate (5) above and spaced from the first plate (4), the second plate being made of a fragile and brittle material, such as sapphire, characterized in that the set of plates (4, 5) forming a dial is tested in a test device, which generates a mechanical shock to the set of plates (4, 5), in that the vibration frequency of each plate is determined, in that an adaptation of vibration frequencies of a of the plates is carried out to tune the two plates to the same vibration frequency so as to be in phase to avoid any contact between the plates following any future mechanical shock. Method for frequency tuning a set of plates (4, 5) according to one of the preceding claims, for which the first plate (4) is spaced from the second plate (5) by 0.1 mm or less, characterized in that that the frequency of vibration of the second plate (5) is adapted at least to the first natural mode of vibration of the first plate (4) which is made of a metallic material. Method for frequency tuning a set of plates (4, 5) according to Claim 3, characterized in that several determinations and adaptations of frequencies are carried out until the same vibration frequency relating to at least one first natural mode is obtained. vibration following a mechanical shock of the plates. Method for frequency tuning a set of plates (4, 5) according to one of the preceding claims, characterized in that in order to adapt the frequency of vibration of one of the plates to be in phase with the frequency of vibration of the On the other plate, a mass is added to one of the plates, the vibration frequency of which is greater than that of the other plate. Method of frequency tuning a set of plates (4, 5) according to Claim 5, characterized in that a mass is driven into the center of the second plate. Method for frequency tuning a set of plates (4, 5) according to one of Claims 1 to 4, characterized in that to adapt the frequency of vibration of one of the plates to be in phase with the frequency of vibration of the other plate, a modification of the stiffness or boundary conditions of the set of plates or at least of one of the plates is carried out. Method for frequency tuning a set of plates (4, 5) according to one of Claims 1 to 4, characterized in that to adapt the frequency of vibration of one of the plates to be in phase with the frequency of vibration on the other wafer, a laser is used to perform local etching or material removal with the aim of having the same vibration frequency on at least the first natural mode of vibration of the two wafers. Method for frequency tuning a set of plates (4, 5) according to one of Claims 1 to 4, characterized in that a digital model is used developed in the test apparatus for tuning frequency of the set of plates (4, 5) with a frequency adaptation for each test. Method for frequency tuning a set of plates (4, 5) according to one of the preceding claims, characterized in that the two plates (4, 5) are frequency matched like acoustic radiation membranes of a watch ringtone or musical. Watch (1) comprising the set of plates (4, 5) tuned according to the frequency tuning method according to one of the preceding claims.

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