EP2461220A1 - Acoustic membrane for a musical box or an alarm watch - Google Patents

Abstract

The acoustic radiating membrane (1) includes, over a first thickness of the total thickness of the membrane, a certain number of cells (5,6) or a certain number of projecting portions. The shape and dimension of each cell or of each portion are adapted according to the type of material and the note to be radiated by the membrane. An independent claim is also included for a striking or musical watch.

Description

An acoustic radiation membrane for a music box, such as a musical watch, or a bell watch.

The invention also relates to a watch, which comprises an acoustic radiation membrane. The watch comprises a watch case consisting essentially of a middle and a bottom fixed and securely attached to the middle part. An ice is disposed on a side opposite the bottom to seal said box. A watch movement is maintained inside the watch case and provided with a striking mechanism that can be activated in specified periods of time to produce sound or music. The acoustic radiation membrane is connected to the box to radiate the sound produced by the striking mechanism to the outside of the box.

In the field of horology, a watch movement of a traditional architecture may also include a striking mechanism. This striking mechanism can be provided to generate at least one sound via a hammer struck stamp at times determined in a bell watch to signal a programmed alarm or minute repetitions. This stamp is usually a circular wire, which surrounds part of the watch movement in a watch cage. This stamp is attached to a stamp holder attached to a plate or the watch case.

The striking mechanism may also be provided to generate music via a multi-blade keyboard individually activated by pins of a cylinder or disc in a musical watch. The keyboard blades are connected to the same heel, which can be fixed on the plate or the watch case, and the pins of the cylinder or rotating disk can lift the free end of some blades. Following the bending of the blades by the action of the pins, these blades are released by the pins. The activated blades oscillate essentially at their first natural frequency.

The timbre of the bell watch or the keyboard of the musical watch are arranged inside the watch case. Thus the vibrations of the timbre or the keyboard blades are transmitted to the trim parts. These pieces of clothing are for example the middle part, the bezel, the ice and the bottom of the watch case. These large pieces begin to radiate sound in the air under the effect of transmitted vibrations. When a sound is produced either by a stamp struck by a hammer or by one or more blades of the vibrating keyboard, these pieces of clothing are able to radiate the sound produced in the air.

In a traditional bell or musical watch, the acoustic output, based on the complex vibro-acoustic transduction of the trim pieces, is low. To improve and increase the acoustic level perceived by the user of the bell or musical watch, the material, geometry and boundary conditions of the trim pieces must be taken into account. The configurations of these pieces of clothing are also dependent on the aesthetics of the watch and operating constraints, which may limit the possibilities of adaptation.

It is known in the art of horology to use in a particular electronic watch, a membrane of the acoustic type, which is dedicated to vibro-acoustic transduction. To activate such a membrane in an electronic watch, it is placed a piezoelectric element for example on the membrane to make it vibrate as mentioned in the patent CH 581 860 . So that the sound radiation of the membrane is not lost in the watch, which must be sealed, it can be provided a double bottom of the watch case, which is open to the outside. In this case, the bottom of the watch case has one or more openings for transmitting the sound of the vibrating membrane.

With such a construction of an electronic acoustic diaphragm watch, it is often encountered problems of sealing and corrosion of said membrane. This membrane must in principle have its first natural vibration frequency, which is the effective mode of radiation, in the useful acoustic frequency band. On the other hand, its second natural frequency, which is an inefficient mode, must be outside this audible band if possible. The useful acoustic frequency band is generally between 1 kHz and 4 kHz. Depending on the boundary conditions and the fixed geometry of the membrane, the physical properties, such as the density and the Young's modulus, must make it possible to adapt the first and second eigenfrequencies. If this membrane is made of steel, the first and second natural frequencies of vibration do not fulfill the above conditions optimally. In addition, a rapid depreciation is found, which is a disadvantage.

Generally with the use of a traditional acoustic radiation membrane, there remains a problem of frequency bandwidth. In the case where the acoustic membrane is to equip a music box, the frequencies to radiate efficiently must typically range between 1 kHz and 4 kHz. In the case of a minute repeater watch, an alarm clock or a quartz alarm, excellent results can be obtained by amplifying a single dominant frequency, tuned with the exciter.

In a standard bell watch, which is provided for example with an acoustic membrane, this membrane is sandwiched between a portion of the middle part and the bottom of the watch case. In the case of a luxury watch, the bottom can be made of a precious material, such as gold. It can occur in contact with the membrane usually made of steel with the gold bottom, an electrochemical potential difference especially in a humid environment. This is likely to promote the corrosion of said membrane at the contact with the gold background, which is a drawback. It must therefore also be found a stainless material with no potential difference with gold and whose internal damping is low.

The purpose of the invention is therefore to overcome the drawbacks of the state of the art mentioned above by providing an acoustic radiation membrane for a music box or a striking watch, made in such a way as to obtain the most uniform amplification possible on the audible frequency band, essentially in the frequency range between 1 kHz and 4 kHz.

For this purpose, the invention relates to an acoustic radiation membrane comprising the characteristics defined in independent claim 1.

Particular forms of the acoustic radiation membrane are defined in dependent claims 2 to 12.

An advantage of the acoustic radiation membrane according to the present invention lies in the fact that it comprises on at least a first thickness smaller than the total thickness of the membrane a number of cells or protruding portions. These cells or protruding portions are of size and shape, which depend on the type of material of the membrane and the note or notes of music to radiate effectively.

Advantageously, the acoustic radiation membrane consists of at least two sheets, of which one of the sheets at the first thickness, is provided with a number of cells preferably distributed in the form of a honeycomb. Each cell can be shaped and dimension dependent on the musical note to radiate effectively. Thus, the first sheet may comprise a number of cells of different size to efficiently radiate an equivalent number of musical notes. This thus makes it possible to increase the overall acoustic level, which can be perceived by a user of the music box or ringing watch in which said acoustic membrane is placed.

Advantageously, the acoustic radiation membrane comprises a first sheet with honeycomb cells uniformly distributed, which is fixed on a second sheet without cells, and a third sheet with cells including honeycomb, fixed on one side opposite of the second sheet. The second sheet may be a gold leaf, while the first and third sheets may be provided in amorphous metal or metal glass, or also in gold. The arrangement of several cell sheets may also make it possible to increase the number of eigenfrequencies in the useful audible frequency band, namely between 1 kHz and 4 kHz, in order also to increase the overall acoustic level. With such a membrane, there is a very low damping, which allows to obtain a very good sound output.

For this purpose, the invention also relates to a watch provided with an acoustic radiation membrane comprising the characteristics defined in the independent claim 13.

Particular shapes of the watch are defined in the dependent claims 14 to 16.

• la figure 1 représente de manière simplifiée une vue tridimensionnelle en éclaté des diverses feuilles, qui composent la membrane de rayonnement acoustique selon l'invention,
• la figure 2 représente de manière simplifiée une vue tridimensionnelle des diverses feuilles assemblées, qui composent la membrane de rayonnement acoustique selon l'invention, et
• la figure 3 représente de manière simplifiée une coupe partielle d'une montre à sonnerie ou musicale, qui est munie d'une membrane acoustique selon l'invention.

The purposes, advantages and characteristics of the acoustic radiation membrane for a music box or a bell watch will appear better in the following description on the basis of at least one non-limiting embodiment illustrated by the drawings in which:

• the figure 1 represents in simplified manner an exploded three-dimensional view of the various sheets that make up the acoustic radiation membrane according to the invention,
• the figure 2 represents in a simplified manner a three-dimensional view of the various assembled sheets, which make up the acoustic radiation membrane according to the invention, and
• the figure 3 represents in a simplified manner a partial section of a bell or musical watch, which is provided with an acoustic membrane according to the invention.

In the following description, all the parts of a music box, such as a musical watch, or a striking watch, which are well known to those skilled in the art, are only described in detail. simplified way.

The figure 1 represents a simplified and exploded three-dimensional view of an acoustic radiation membrane 1 for a music box, such as a musical watch, or a striking watch. In this embodiment, the membrane 1 firstly comprises a first sheet 2, which comprises several cells 5, which may be of identical or different size. This first sheet 2 may be glued or soldered to a first face of a second sheet 3 without cells so as to ensure a certain seal inside the watch, once the membrane is mounted in the watch case. A third sheet 4 with cells 6 of identical or different size, can still be glued or brazed to a second face of the second sheet 3. The cells 5 of the first sheet 2 can be arranged opposite the cells 6 of identical or different size of the third sheet 4. However it may be conceivable that the membrane 1 comprises only the first sheet 2 at a first thickness and the second sheet 3 at a second thickness. The thickness of each sheet may be less than 0.2 mm, and preferably close to 0.1 mm.

The cells 5, 6 of the first sheet 2 and the third sheet 4 are evenly spaced from each other, and configured in the form of a honeycomb with six identical sides. Although only three cells are represented on the figure 1 it is understood that said membrane 1 may comprise a larger number of cells to occupy most of the surface of the acoustic membrane 1. Other shapes of cells may also be imagined, for example circular or oval, but the honeycomb configuration makes it possible to better fill the surface of the cell membrane.

In the case of the radiation of a particular note with uniform amplification in the audible frequency band, all the cells of the first sheet 2 are of identical shape and size. The size is determined also according to the material of the first sheet 2 and the second sheet 3. The larger the cell size, the higher the corresponding frequency is serious, i.e. low frequency. For the same cell size, it is still to be noted that the greater the total thickness of the membrane 1 is important, and the frequency of the radiated note is high. The total thickness of the membrane is in principle less than or equal to 1 mm.

On the other hand, in the case of the radiation of several musical notes by the acoustic membrane in a musical watch, it can be provided that each cell 5, 6 of the first sheet 2 and / or the third sheet 4 is dimensioned for each note. particular music. Thus it is defined a set of mini-membranes each configured for effective radiation of a particular note of a music with a uniform amplification of the first eigenfrequencies between 1 kHz and 4 kHz. The number of cells in the first and / or third sheets 2, 4 is identical to the number of musical notes that can be generated in the musical watch. To radiate between 10 and 15 notes effectively with said membrane, it is necessary to make between 10 and 15 cells.

The first, second and third sheets 2, 3, 4 of the acoustic membrane 1 are made of a metallic material, which may be different for each sheet or the same, or of metal glass for at least one of the three sheets. Preferably, the second sheet 3 without cavities may be made of gold or titanium, and the first and third sheets 2, 4 are made of amorphous metal or metal glass. It may be conceivable that all sheets are made of gold or titanium to define a membrane of the same material.

For the realization of the acoustic membrane 1, it is preferable to first machine the cells 5, 6 on the first sheet 2 and the third sheet 4 before their attachment by bonding or brazing on the second sheet 3. The cells 5 , 6 in the first and third sheets are machined for example by stamping or etching.

The acoustic radiation membrane 1 may be composed of more than two cell sheets to define a set of cell sheets, and at least one sheet without cells inserted between two of the cell sheets. All leaves are glued or brazed one on the other. Each sheet may have the same thickness, for example of the order of 0.1 mm or a thickness different from one another, but the total thickness of the membrane must in principle be less than or equal to 1 mm depending on the material. selected. Each cell sheet can thus be configured for the radiation of a given note among several notes to be radiated by the membrane with uniform amplification.

The figure 2 represents a simplified three-dimensional view of the acoustic membrane 1 once all the sheets are assembled. This acoustic membrane 1 to be mounted in a ring or musical watch, may be circular in shape with a diameter of between 20 and 40 mm, preferably close to 31 mm. It can be flat or bowl-shaped as shown partly in the figure 3 explained below.

It should also be noted that instead of providing a first sheet 2 provided with cells 5 on a first thickness of the thickness total of the acoustic membrane 1, it may be provided to produce protruding portions on a first thickness of said membrane. These protruding portions not shown come directly from the material with the base of the membrane without cells. The portions may also be configured as honeycombs and each be tuned for the effective radiation of a particular note.

The figure 3 represents a partial section of a bell or musical watch 10. The watch 10 essentially comprises an acoustic radiation membrane 1 according to the invention for improving the acoustic performance of a note or notes produced by a striking mechanism. This acoustic membrane may comprise two or three sheets 2, 3, 4, of which one or two sheets 2, 4 are in cells 5, 6 and an intermediate sheet 3 is without cells. At least the two cell sheets may be made of an amorphous metal or metal glass, which is a stainless material, while the second intermediate sheet 3 may be made of gold or titanium. The thickness of this membrane 1 may be less than or equal to 1 mm.

The ring or musical watch 10 also comprises a watch movement 20, which is generally mounted on a plate 24. An edge piece 22 is fixed to the plate 24, which defines a watch cage. Usually both the plate 24 and the edge piece 22 are made of a metallic material.

The watch movement 20 comprises a striking mechanism, not shown. This striking mechanism may comprise at least one stamp mounted on a stamp holder integral with the plate 24, and at least one hammer rotatably mounted on the plate to strike said stamp in specified periods. The generally circular stamp surrounds the various parts of the watch movement of the ringing watch. Such a striking mechanism is provided to signal a programmed alarm or minute repetitions.

In a more elaborate embodiment of a musical watch, the striking mechanism may comprise a keyboard with a set of blades connected to a heel, which is attached to the deck 24. A note or a succession of musical notes are produced by keyboard blade vibrations. Each blade is normally configured to produce a particular note, but it can be expected to have certain groups of two blades for each group to produce the same particular note. To produce a music for example in programmed periods, the keyboard blades are lifted and released by pins integral with a cylinder or a disc rotating on the plate 24. Each activated blade oscillates mainly at its first natural frequency. The vibrations generated by the activated blades are transmitted to the watch's trim pieces, which must make it possible to radiate acoustically the sound produced by each vibrating blade.

In this embodiment, the acoustic membrane 1 is cup-shaped, the upper edge of which is sealingly mounted by an annular liner 18 on an inner annular flange of the bottom 15 of the box. The diameter of this cuvette, which may be equivalent to the diameter of the watch crystal 12, may be between 20 and 40 mm, preferably close to 31 mm. An annular support 21 supports on one side the plate 24 with the edge piece 22 and rests on the upper edge of the acoustic membrane 1. At the time of attachment of the caseband 14 to the bottom 15 of the watch case, the support 21 and the peripheral edge of the acoustic radiation membrane 1 are clamped between the caseband 14 and the base rim 15.

The bottom 15 is mounted by known means and removably on the middle part 14 with a seal 19. A watch crystal 12 is fixed in particular to the bezel 13 to seal the watch case. A dial 23 is held at the edge on the middle part and arranged beneath the watch crystal 12. In the case of a mechanical bell watch 10, time indication hands, which are not not shown, are provided on the dial, which usually carries hourly indices in the periphery.

The central portion of the acoustic membrane is not in contact with the support 21 and the inner surface of the bottom 15. As a result, sufficient space 17 in the box is provided so that the acoustic membrane can freely vibrate or radiate acoustically. The entire acoustic membrane 1 and the bottom 15 thus constitutes a double bottom. One or more openings 16 are also provided laterally through the bottom 15 to allow the acoustic membrane to radiate the sound produced by the striking mechanism to the outside.

During operation of the striking mechanism, the note or notes generated by said striking mechanism are transmitted directly to the acoustic radiation membrane 1 to vibrate. A vibration transmission to the acoustic membrane 1 is also provided at the edge of the acoustic membrane by the connecting pieces 21, 22 and 24. As the acoustic membrane is composed of sheets made of gold or titanium or partly of amorphous metal, it is likely to vibrate at several first eigenfrequencies functions of the number of notes expected to radiate. These first natural frequencies are preferably located in the useful acoustic band between 1 and 4 kHz. The second natural frequencies of vibration of the notes are however located above 4 kHz. This is very advantageous since the second vibration frequencies are often destructive of sound. These desired natural frequencies of sound vibration of the partially amorphous metal membrane are dependent on the physical properties, such as the density and the Young's modulus. Moreover with such a membrane, it is found a very low damping, which provides a very good sound performance of this acoustic membrane 1.

Due to the fact that this membrane is composed of stainless materials, it can be mounted on a background for example of precious metal, such as gold. No electrochemical potential difference is thus found even in a humid environment, which means that no corrosion occurs in contact with the membrane 1 and the bottom 15.

The metallic glass or amorphous metal used for the production of at least two cellular sheets of the membrane may for example be a metal alloy based on titanium, zirconium and beryllium. Thus, by way of a more specific example, the amorphous metal alloy may comprise 41% of zirconium, 14% of titanium, 12% of copper, 10% of nickel and 23% of beryllium. The Young's modulus of this alloy is 105 GPa and the elastic limit is 1.9 GPa. The amorphous metal alloy may also consist of 57.5% platinum, 14.7% copper, 5.3% nickel and 22.5% phosphorus. The Young's modulus of this alloy is in this case 98 GPa and the elastic limit is 1.4 GPa.

From the description that has just been given, several embodiments of the acoustic radiation membrane for a music box or a striking watch can be designed by those skilled in the art without departing from the scope of the invention defined by the claims. The acoustic membrane may be located in the watch case at the middle of the case with an opening through the caseband for the sound radiation of the acoustic membrane in vibration. The acoustic membrane may possibly be located on an outer portion of the watch case, but disposed at least on an opening of the housing so that the note or notes generated by the striking mechanism can vibrate the membrane. It can be provided several acoustic membranes arranged in several places inside the watch case or superimposed. These acoustic membranes can be made with the same number or a different number of cell sheets.

Claims (16)

Acoustic radiation membrane (1) for a music box or a striking watch (10), characterized in that the membrane comprises on a first thickness (2) of the total thickness of the membrane a number of cells (5) or a number of projecting portions, the shape and size of the cells or portions of which are adapted according to the type of material, as well as the note or notes to be radiated by the membrane with uniform amplification in the audible frequency band. Membrane (1) according to claim 1, characterized in that the membrane comprises a first sheet (2) at the first thickness, in which the cells (5) are formed, and a second sheet (3) without cells, the first sheet being disposed on a first face of the second sheet. Membrane (1) according to claim 2, characterized in that the membrane comprises at least one third sheet (4) provided with a number of cells (6), the third sheet being arranged on a second face of the second sheet (3). Membrane (1) according to one of the preceding claims, characterized in that the cells (5, 6) or the protruding portions are configured in the form of a honeycomb. Membrane (1) according to one of claims 2 and 3, characterized in that the first, second and third sheets (2, 3, 4) are made of a different or identical metallic material, or at least one of the three sheets in amorphous metal or metal glass. Membrane (1) according to claim 5, characterized in that the second sheet (3) is made of gold or titanium, and in that the first and third sheets (2, 4) are made of amorphous metal or metallic glass or in gold or titanium. Membrane (1) according to one of claims 2 to 4, characterized in that the number of cells in the first and / or third sheets (2, 4) is identical to the number of musical notes to be radiated by the membrane in the audible frequency band and mainly for first eigenfrequencies between 1 kHz and 4 kHz. Membrane (1) according to claim 7, characterized in that the number of cells, which are each configured according to the musical note to be radiated by the membrane, is defined between 10 and 15 to allow uniform amplification between 10 and 15 notes generated in a music box or a bell watch. Membrane (1) according to one of claims 7 and 8, characterized in that the cells (5) of the first sheet (2) are arranged opposite identical cells (6) of the third sheet (4). Membrane (1) according to claim 3, characterized in that the cells (5) of the first sheet (2) are configured to radiate with a uniform amplification a first musical note, and in that the cells (6) of the third sheet (4) are configured to radiate with a uniform amplification a second musical note. Membrane (1) according to claim 10, characterized in that it comprises an assembly of several cellular sheets and at least one second sheet without cells inserted between two cellular sheets, all the sheets being bonded or brazed to one another. other, and in that each cell sheet is configured for radiation of a given one of a number of notes to be radiated by the membrane with uniform amplification. Membrane (1) according to one of claims 2, 3, 10 and 11, characterized in that the thickness of each sheet is less than 0.2 mm, preferably close to 0.1 mm, while the total thickness of the membrane is less than or equal to 1 mm, and in that the membrane is circular shape of diameter between 20 and 40 mm, preferably close to 31 mm. A bell or musical watch (10), comprising a watch case, which comprises a middle part (14) and a bottom (15) with at least one lateral opening (16), the bottom being fastened securely and removably to the middle part , an ice (12) sealing the box, a watch movement (20) held inside the watch case and provided with a striking mechanism that can be activated in specified periods to produce a note or several notes, and at least one acoustic radiation membrane (1) according to one of the preceding claims, which is arranged in the watch case. Watch (10) according to claim 13, characterized in that the acoustic membrane (1) is held on an inner rim of the bottom (15) of the box and a part of the middle part (14), and in that the periphery of the acoustic membrane (1) is clamped with the periphery of a support (21) of movement between the middle (14) and the inner rim of the bottom (15) of the box. Watch (10) according to claim 14, characterized in that the acoustic membrane (1) has a bowl-like shape, an upper edge of which is clamped with the annular support between the middle part (14) and an inner annular flange of the bottom (15). ) of the box, an annular seal (18) being placed between the bottom flange (15) and the annular edge of the membrane, and in that a central portion of the acoustic membrane is not in contact with the support (21) and an inner surface of the bottom (15) of the box to define a space (17) in order to be able to oscillate freely. Watch (10) according to claim 13, characterized in that several acoustic radiation membranes (1) are connected to the watch case and spaced from one another or superimposed.

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