EP4012511B1 - Method for harmonic tuning of at least one gong for a chiming mechanism of a watch - Google Patents

Description

The invention relates to a method for the harmonic tuning of at least one gong of a striking mechanism of a watch. The striking mechanism comprises at least one gong attached to a gong holder, and at least one hammer for striking the gong at predetermined instants.

Prior art

In minute repeater watches, the vibro-acoustic improvements relate essentially to the regulation elements, which make it possible to limit the noise of the mechanism when a chime is triggered. It is also carried out elements of the dressing, which make it possible to increase the acoustic level of the bell. These covering elements can also be acoustic radiation membranes or other radiating parts of the case of the watch.

Generally a sound is generated by an element generating sound vibrations radiated by the casing of the watch case and this generating element is mainly a gong of a striking mechanism. The vibration of the gong is produced by the impact, generally close to the gong holder, of at least one hammer. This vibration is composed of several eigenfrequencies, the number and intensity of which, in particular in the audible domain, depend on the geometry of the gong, the conditions of fixation or support of the gong, the conditions of shock and the physical properties. of the material.

It should be noted that the timbre is rarely optimized. Improvements to the timbre relate essentially to its dimensions in order to target, on the one hand, a desired frequency and, on the other hand, to tune at least one of the partials of the hour and minute timbre together. In this case figure, we speak of tuning the melodic interval. The material constituting the timbres can also be an improvement factor for modifying the frequency richness of the sound emitted. However, it is sometimes difficult to control the overall frequency content of the timbre, which depends on its dimensional shape and the material chosen to produce the timbre.

In this regard, we can cite the patent application EP 3 211 488 A1 , which describes an atypically shaped gong in planar form in an XY plane for a striking mechanism of a watch. The gong is connected at least at one of its ends to a gong holder, which can be fixed to an inner wall of the watch middle. The stamp includes several notches made at defined geometric points over a portion of its length. This makes it possible to adapt natural vibration frequencies in an audible band between 1 kHz and 5 kHz, to obtain a harmonic agreement defined beforehand for each timbre and to make the sound generated harmonious. However, the adaptation of the natural frequencies by the realization of these notches is irreversible. This constitutes a drawback, if it is desired to adapt other frequencies of vibration of the timbre. Moreover, this does not make it possible to avoid any dissonance of a struck stamp generating in-plane and out-of-plane vibration frequencies depending on the proximity of these frequencies.

The patent application EP 2 808 745 A1 describes a striking mechanism of a watch, which comprises means for selecting a vibratory mode of a gong. To do this, the selection means comprise a selector element placed in contact on a part of the gong and held on a vibration node of a vibration mode of the gong to be selected. This makes it possible to block other vibrational modes. This selector element can be moved over a portion of the timbre by a moving means, which makes it possible to select a vibratory mode in a non-irreversible manner. However, no possibility of optimizing the timbre configuration is described in order to adapt a frequency of vibration in a non-irreversible manner to ensure fine tuning with the exterior of the watch. Moreover, any sound dissonance following the striking of the gong by a hammer cannot be avoided depending on the vibration frequencies generated in the plane of the gong and out of the plane of the gong.

The patent application CH 707 078 A1 describes a gong for a striking mechanism. A gong vibration frequency adjustment device is provided. An element in the form of a weight is mounted on the gong to act on a part of the gong to effect local mechanical stress. This makes it possible to adjust a vibration frequency of the stamp struck. However, by acting with such a weight mounted on a portion of the gong, this does not make it possible to precisely adjust a natural frequency of vibration. Moreover, this does not make it possible to avoid any dissonance during the generation of vibration frequencies in the plane of the gong and out of the plane of the gong following the striking of the gong by a hammer.

The patent application CH 708 885 A1 describes a method for sizing and/or tuning one or more gongs for a timepiece

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 method for the harmonic tuning of at least one gong of a striking watch configured to remove certain dissonances from the sound emitted by the watch. when the gong is activated by the strike of the hammer.

To this end, the invention relates to a method for the harmonic tuning of at least one gong of a striking watch, which comprises the characteristics defined in independent claim 1.

Particular steps of the process for the harmonic tuning of at least one gong of a striking watch are defined in dependent claims 2 to 9.

An advantage of the timbre harmonic tuning process is that the vibration frequencies in the XY plane show in a basic eigenmode or for subsequent partials in the audible frequency band between 20 Hz and 5 kHz, are made very close to the watch out-of-plane vibration frequencies Z so as not to be perceived by the human ear. Thus, this makes it possible to avoid any dissonance or beating, which leads to a deterioration in the sound quality by such frequency coupling. The watch plan can correspond to the gong plan.

Advantageously, the method makes it possible to tune the vibration frequencies in the XY plane and outside the Z plane in such a way as to respect the formula or ratio r = |fip - fih|/fip ≤ 0.006 or r' = |fih - fip|/ fih ≤ 0.006, where fip is the vibration frequency in the XY plane of the i _th selected eigenmode, and fih is the out-of-Z plane vibration frequency of the i _th eigenmode. The calculation of the ratio r or r' depends on the direction in which the hammer hits the gong. The desired value of the ratio is always the same for each eigenmode in the audible frequency range. If these vibration frequencies of each eigenmode lead to a ratio r or r′ of the order of 0.006 or even lower, the timbre is considered to be tuned. In this case, it does not generate any dissonance so that the human ear no longer distinguishes between the two frequencies that are too close to each other. The desired value of this ratio can also be set smaller or equal to 0.005 and it depends on a person's perception of sounds.

Advantageously, in order to be able to tune the vibration frequencies of the stamp struck by a hammer either in the XY plane, or outside the Z plane, or also in an oblique direction, an acoustic measuring instrument is used provided with a microphone unit, or with vibration measurement with a laser vibrometer or any other device allowing to measure the dynamic response of the timbre. The gong can be placed on a suitable measuring support to be struck by a hammer outside the watch case or the gong can preferably be mounted directly in the watch case so as to be struck by the hammer of the striking mechanism . The measuring instrument may include a microphone unit at the input to pick up the sound of the struck timbre, or include a vibrometer for vibration measurement. In addition, in a processor or microcontroller unit of the measuring instrument, an FFT analysis of the signal picked up by the microphone or by the laser vibrometer can be performed in order to obtain two frequency peaks which correspond to the vibration frequencies in the plane and off-plan of the stamp. Following this FFT analysis, it is possible to determine what alterations to make on the timbre to have the two vibration frequencies in the plane and out of the plane sufficiently close to each other to avoid any dissonance of the sound generated by the struck stamp.

It should also be noted that retouching of the timbre must be carried out if the ratio is greater than the value of 0.006. This mainly depends on the frequency difference between the vibration frequencies in the analyzed eigenmode.

Brief description of figures

• les figures 1a et 1b représentent une vue de dessus montrant une vue en plan d'un timbre fixé à un porte-timbre et une vue de côté montrant une vue hors plan du timbre avant la frappe d'un marteau,
• les figures 2a et 2b représentent une vue de dessus montrant une vue en plan d'un timbre en vibration et fixé à un porte-timbre et une vue de côté montrant une vue hors plan du timbre en vibration, et
• les figures 3a et 3b représentent un graphique d'une analyse FFT d'un signal capté par exemple par un microphone de l'instrument de mesure pour représenter des pics fréquentiels à deux fréquences de partiels d'une part avant une retouche du timbre à la figure 3a, et d'autre part après une retouche du timbre à la figure 3b avec les deux fréquences de vibration proches l'une de l'autre à deux niveaux de fréquence.

The aims, advantages and characteristics of the process for the harmonic tuning of at least one gong of a striking watch will appear better in the following description, in particular with regard to the drawings in which:

• THE figures 1a and 1b represent a top view showing a plan view of a stamp attached to a stamp holder and a side view showing an out-of-plan view of the stamp before striking a hammer,
• THE figures 2a and 2b show a top view showing a plan view of a vibrating stamp attached to a stamp holder and a side view showing an out-of-plan view of the vibrating stamp, and
• THE figures 3a and 3b represent a graph of an FFT analysis of a signal picked up for example by a microphone of the measuring instrument to represent frequency peaks at two frequencies of partials on the one hand before a retouching of the timbre on the picture 3a , and on the other hand after a retouching of the timbre in the figure 3b with the two vibration frequencies close to each other at two frequency levels.

Detailed description of the invention

In the following description, all the well-known parts of a striking mechanism of a striking watch, fitted with at least one gong will only be briefly described. Exclusive reference will be made to the process of harmonic tuning of at least one gong of a striking watch in such a way that the gong, once tuned, no longer generates dissonance or beat following the striking of a hammer in any direction. , for example in the direction of the plane of the stamp XY or in the direction out of the plane of the stamp Z or in an oblique direction.

THE figures 1a and 1b represent only a gong 1 of a traditional arrangement mainly in the form of an arc of a circle, which can be arranged around a watch movement once mounted in the watch case. The cross-section of the stamp 1 over part of its length or over its entire length can be circular, oval, hexagonal, octagonal, bean-shaped or other shapes. In this case, the gong is in a plane, which is the watch plane. It can also be envisaged that the patch has a cross-section varying from one end to the other end.

As shown at picture 1a , this stamp 1 in the form of an arc of a circle is configured in an XY watch plane, which here is the XY stamp plane with one end fixed to a stamp holder 2, while another end is left free to move . It can also be envisaged to fix the stamp to the stamp holder 2 in an intermediate part between the first end and the second end or also to fix each end of the stamp to a respective stamp holder 2 without free end of movement. There figure 1b only represents stamp 1 in side view. The gong holder 2 is generally intended to be fixed by a fixing means 3, such as screws, on a support such as a plate of the watch movement, or possibly fixed to an inner surface of the middle part of the case watch or on another part of the casing or even on a membrane. The gong 1 can be struck by a hammer (not shown) in a defined direction, for example in the direction of the gong plane XY or the direction out of plane Z, or even also in an oblique direction. This generates a sound with one or more vibration frequencies depending on the number of partials generated in connection with the material constituting the gong and the shock conditions between the hammer and the gong. Said hammer is generally provided to strike the gong 1 close to the gong holder 2 on an interior side of the arrangement of the gong depending on the space available.

By striking gong 1 with the hammer in a direction of the XY gong plane, one expects to generate at least one frequency of vibration in the XY plane. This means that normally only eigenmodes whose deformations lie in the XY plane should be activated. But in practice, depending on the machining tolerances of gong 1, and again the games of the hammer in its pivotings, striking the hammer on gong 1 activates at least two basic natural modes with on the one hand a frequency of vibration in the XY plane and also an out-of-plane vibration frequency in the parasitic Z direction.

By way of non-limiting example shown in figures 2a and 2b of timbre 1 in vibration, the frequency spectrum of the generated sound then contains the two frequencies 1,788 Hz and 1,731 Hz, which are on the one hand the frequency of vibration in the XY plane, and on the other hand the frequency of out-of-plane vibration in the Z direction. The two frequencies generated in the first vibration eigenmode are very close to each other and to a frequency difference likely to be perceived by the human ear in the range of Audible frequencies defined primarily from at least 20 Hz up to 5 kHz. In this range of audible frequencies, the perception of these two vibration frequencies by the human ear causes dissonance or beating, which very clearly deteriorates the quality of the perceived sound.

For the human ear not to be able to perceive the two vibration frequencies, it is necessary to tune them in such a way as to respect the formula or ratio in absolute values r = |fip - fih|/fip ≤ 0.006, where fip is the vibration frequency in the XY plane of the i _th eigenmode, and fih is the parasitic out-of-plane Z vibration frequency of the i _th eigenmode. If these tuned vibration frequencies lead to a ratio of the order of 0.006, which is a target value or a defined threshold, then the sound generated by the striking of the timbre is clear and harmonious and of course without perception of dissonance by the human ear, which is sought after. But as we can calculate with this example of vibration frequencies above, we arrive at a ratio r = 0.032, which is about 5 times higher than the expected value. The frequency difference between these two vibration frequencies must therefore be corrected. This is what the method of the present invention seeks to achieve.

The process also makes it possible to tune the vibration frequencies in the XY plane and outside the Z plane in such a way as to respect the formula or ratio r = |fip - fih|/fip ≤ 0.006 or r' = |fih - fip|/fih ≤ 0.006, where fip is the vibration frequency in the XY plane of the i _th selected eigenmode, and fih is the vibration frequency out of the Z plane of the i _th eigenmode. The ratio r is selected in the case of a strike substantially in the XY stamp plane, while the ratio r' is selected in the case of a strike substantially outside the Z plane, i.e. perpendicular to the plane of the XY stamp.

Of course as shown in figures 1a, 1b, 2a, 2b , 3a, 3b , once gong 1 is struck by the hammer, it generates a first base frequency f1p, f1h and several higher frequency partials at least in the audible frequency range of 20 Hz to 5 kHz. For some At frequencies above 5 kHz, the proximity of two in-plane and out-of-plane vibration frequencies no longer matters much, as they are no longer dissociated by the human ear. Tuning of vibration frequencies should be done primarily for frequencies in the audible frequency range of 20 Hz to 5 kHz. However, it can also be envisaged to perform the tuning of timbre 1 in an audible frequency range of at least 20 Hz to 10 kHz or 20 kHz.

To tune gong 1 of the striking mechanism of the watch, not shown, it can be placed in particular via the gong holder on a suitable support of a measuring instrument to be struck by a hammer outside the watch box. Gong 1 can also be directly part of the striking mechanism of the watch, in order to place the watch case comprising the striking mechanism with gong 1 on a suitable support of the measuring instrument and to control the striking of gong 1 by the hammer of the mechanism at predetermined or programmed instants.

After gong 1 is struck by the hammer, a microphone unit or a vibrometer of the measuring instrument can pick up the sound or vibration signal from the vibrating gong. A filtering of the sound or vibration signal can still be carried out, then an FFT fast Fourier transform operation of the filtered or unfiltered signal coming from the microphone unit or from the laser vibrometer is carried out in a processor unit or in a microcontroller of the 'measuring tool. A storage of the output signals after the FFT can still be carried out in the measuring instrument. A graphical representation of the different frequency peaks of several vibration frequencies in the XY plane and outside the Z plane depending on the different audible modes of the vibrating timbre, can be performed after the FFT as represented for example in figures 3a and 3b described below.

It should be noted that in general, the measuring instrument is suitable for measuring the dynamic response of the gong once struck by the hammer. This means that the dynamic response includes both a sound or audible signal, as well as a vibration signal.

THE figures 3a and 3b show graphs of an FFT analysis of a signal from the microphone unit or vibrometer. The output signals are stored in the measuring instrument. The frequency peaks observed on the figures 3a and 3b , are relative to vibration frequencies in the XY plane and outside the Z plane of the vibrating gong. It is observed on the one hand the vibration frequencies in the XY plane and outside the Z plane before modification of the stamp, that is to say before carrying out a retouching of the said stamp at the picture 3a , and on the other hand after modification of the stamp at the figure 3b . This vibration is composed of several natural or partial frequencies, two of which are represented on the figures 3a and 3b in the audible frequency range. This is a first natural frequency close to 1.7 kHz and a second natural frequency close to 3 kHz.

At the first natural frequency in picture 3a , two frequency peaks are generated, which are a first vibration frequency f1p in the XY plane and a first out-of-plane vibration frequency f1h along the Z axis. At the second natural frequency, two frequency peaks are generated which are a second vibration frequency f2p in the XY plane and a second out-of-plane vibration frequency f2h along the Z axis.

To the figure 3b for the first natural frequency, it is generated after all the retouching steps of the timbre in the end, two frequency peaks which are a first frequency of vibration of the tuned timbre in the XY plane f1pf, and a first frequency of vibration of the tuned timbre out of plane Z f1hf. At the second natural frequency, two frequency peaks are generated which are a second frequency of vibration of the tuned timbre f2pf in the XY plane and a second frequency of vibration of the tuned timbre f2hf out of plane along the Z axis.

Once the check has been carried out automatically by the measuring instrument or by vision on the graphs of the figures 3a and 3b , the ratio r1 = |f1p - f1h|/f1p and ratio r2 = |f2p - f2h|/f2p must be calculated. It must then be determined whether each ratio r1 and r2 is less than or equal to the desired value of 0.006. If so, the gong is considered tuned, but if not, the gong must be tuned and at least one retouching must be carried out, i.e. localized machining on part of the gong and preferably close to the stamp holder. This machining, which is generally carried out by mechanical means, makes it possible to carry out this retouching in particular following knowledge of the frequency difference between the frequency of vibration in the XY plane and the frequency of vibration outside the Z plane of the first frequency natural and/or of the second natural frequency.

Depending on prior knowledge of various previous memorized retouchings and the result obtained, one or more successive retouchings on the timbre can be carried out until the moment when the ratio r1 and/or r2 is equal to or less than the desired value of 0.006. This means that after the first touch-up, the measuring instrument again picks up the sound generated by the vibrating gong. An FFT processing of the signal coming from the microphone is then carried out in order to control at the output the frequency peaks of the vibration frequencies in the XY plane and outside the Z plane of the first natural frequency and of the second natural frequency. A calculation of the ratios r1 and r2 is again performed to determine whether each ratio is less than or equal to the desired value of 0.006. If so, no further correction is made to the stamp, while if not, a new retouching operation must be performed, and so on until the expected ratio is obtained.

This editing operation can be performed manually or automatically. Under these conditions and depending on the various edits made previously and stored, each edit may preferably be carried out automatically by a machining tool of an automatic machining machine. It can be milling or grinding or by crushing (plastic deformation). Several simulations depending on the frequency difference of the vibration frequencies in the XY plane and outside the Z plane make it possible to precisely establish the type of machining and the retouching to be carried out to have the ratio r1 and/or r2 equal to or less than the value desired value of 0.006 after very few successive retouching steps.

As previously indicated, the purpose of this procedure is to bring the two frequency peaks closer together, i.e. the vibration frequency in XY plane mode and the vibration frequency in Z out-of-plane mode so that the described ratio is lower or equal to 0.006. For this, retouching on the timbre is carried out and each acoustic or vibratory recording is analyzed after these retouching to study the frequency content of the measured signal.

By experience, one can know exactly where to do the retouching and the necessary dimension of the retouching in order to be able to correct the two vibration frequencies in the XY plane and out of the Z plane in one operation at best. A database in the measuring instrument is designed in such a way as to know automatically, according to the frequency peaks determined in the measuring instrument following the FFT analysis, what is the retouching to be carried out precisely on the timbre to correct and grant said stamp in one go.

It should also be noted that for all the frequencies in the eigenmode in the audible frequency range (0 to 5 kHz), a control is carried out with the same ratio, which must be less than or equal to 0.006 so that the human ear no longer dissociates these two frequencies of vibration close to each other. In addition, any shape of the stamp can be envisaged, in particular or mainly with a shape lying in a plane so as to be able to control vibration frequencies in the XY plane and outside the Z plane. However, it can also be envisaged to have a stamp describing a three-dimensional shape and not just in one plane, for example the stamp could be in the shape of a corkscrew or the like. Independently of the actual shape of the timbre, a vibration in the XY plane, a vibration outside the Z plane of at least one eigenmode or of all the eigenmodes in the audible frequency range is measured.

From the description which has just been given, several variants of the method for harmonizing a timbre can be devised by those skilled in the art without departing from the scope of the invention defined by the claims. Each retouching of the stamp can be carried out mainly close to the stamp holder manually by a watchmaker, or automatically by a machine controlled by the measuring instrument for example.

Claims (9)

1. A method of harmonic tuning of a gong (1) of a striking watch, the gong (1) being fastened to at least one gong holder (2) by at least one of its ends or by an intermediate portion located between the first end and the second end of the gong (1), and for which a ratio of vibration frequencies generated on the one hand in a watch plane XY, and on the other hand outside the watch plane according to the axis Z following a strike of a hammer against the gong (1),
   the method comprising the following steps:

   - placing the gong (1) by means of its gong holder (2) on an adapted support of a measuring instrument or placing a watch case comprising a striking mechanism with the gong (1) on an adapted support of the measuring instrument,

   - striking the gong (1) in a direction defined by a hammer which is external or forming part of the striking mechanism of the watch,

   - picking up the dynamic response of the gong activated and vibrated by the strike of the hammer, by the measuring instrument,

   the method being characterised in that it comprises the following steps :

   - processing the dynamic response signal of the gong by performing a fast Fourier transform in a processor unit or in a microcontroller of the measuring instrument,

   - determining at least two frequency peaks which correspond, in a selected natural mode, to the vibration frequencies in the plane XY and outside the plane Z of the vibrating gong in an audible frequency band from 20 Hz to 5 kHz,

   - calculating at least one ratio r = |fip - fih|/fip ≤ 0.006 or r' = |fih-fip|/fih ≤ 0.006, where fip is the vibration frequency in the plane XY of the i_th selected natural mode, and fih is the vibration frequency outside the plane Z of the i_th natural mode, the calculation of the ratio r or r' depending on the direction of striking of the hammer against the gong,

   - comparing the ratio r or r' to a desired value equal to 0.006 in such a way that if r or r' is equal to or less than the desired value of 0.006 the gong is considered tuned, on the other hand, if r or r' is greater than the desired value, a gong adjustment operation is carried out before repeating the steps of the method from the striking of the gong by the hammer.
2. The method of harmonic tuning of a gong (1) according to claim 1, characterised in that the dynamic response of the activated and vibrating gong is a sound or audible signal picked up by a microphone unit of the measuring instrument.
3. The method of harmonic tuning of a gong (1) according to claim 1, characterised in that the dynamic response of the activated and vibrating gong is a vibratory signal picked up by a laser vibrometer.
4. The method of harmonic tuning of a gong (1) according to claim 1, characterised in that all the natural frequencies of the gong in the audible frequency band from 20 Hz to 5 kHz are tuned.
5. The method of harmonic tuning of a gong (1) according to claim 1, for which the gong (1) is configured to be disposed in a gong plane which corresponds to the watch plane, characterised in that the gong is struck by the hammer in one direction of the gong plane and in that the ratio r = |fip-fih|/fip ≤ 0.006 is calculated to determine whether gong adjustment operations must be carried out.
6. The method of harmonic tuning of a gong (1) according to claim 1, for which the gong (1) is configured to be disposed in a gong plane which corresponds to the watch plane, characterised in that the gong is struck by the hammer in a direction outside the gong plane Z, perpendicular to the watch plane or in a direction of an oblique strike, and in that the ratio r' = |fih - fip|/fih ≤ 0.006 is calculated to determine whether gong adjustment operations must be carried out.
7. The method of harmonic tuning of a gong (1) according to claim 1, characterised in that several simulations depending on the frequency difference of the vibration frequencies in the plane XY and outside the plane Z allow to precisely establish the type of machining and adjustment to be carried out to have the ratio r and/or r' equal to or less than the desired value of 0.006 after one or two successive adjustment steps.
8. The method of harmonic tuning of a gong (1) according to claim 1, characterised in that a database in the measuring instrument is designed in such a way that it automatically knows, according to the frequency peaks determined in the measuring instrument following the FFT analysis, what adjustment to be carried out precisely on the gong to correct and tune said gong at once.
9. The method of harmonic tuning of a gong (1) according to one of the preceding claims, characterised in that each adjustment of the gong is carried out by milling or grinding or by local crushing of the gong material.

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