HK1172958B - Acoustic radiating membrane for a music box or striking watch - Google Patents

Description

Acoustic radiating membrane for music box or chronometer

Technical Field

The present invention relates to an acoustic radiating membrane (acoustic radiating membrane) for a music box such as a music watch or a time-telling watch.

The invention also relates to a watch comprising an acoustic radiating membrane. The watch comprises a case essentially formed by a middle part and a back cover detachably fixed in a sealed manner to the middle part. A crystal is provided on the opposite side of the back cover to close the watch case in a sealed manner. The timepiece movement is held inside the case and is provided with a striking mechanism that can be actuated at determined times to produce a sound or music. At least one sound radiating membrane is connected to the case so as to radiate sound generated by the striking mechanism toward the outside of the case.

Background

In the field of horology, a timepiece movement of conventional construction may also incorporate a striking mechanism. Such striking mechanism may be used to generate at least one sound via a gong (gong) which is struck by a hammer at a determined time in a striking watch to indicate a programmed alarm or minute repeater. The gong is typically a round wire that surrounds a portion of the watch movement inside the bezel. The gong is fixed to a gong-carrier, which is integral with the bottom plate or with the watch case.

The striking mechanism can also be used to produce music via a pin-barrel (pin-barrel) with several tongues, which are actuated by the pins of a cylinder or disc, respectively, in a music watch. The tongues of the pin cylinder are connected to the same heel, which can be fixed to the bottom plate or to the watch case, and the pins of the rotating cylinder or disc allow the free ends of some tongues to be lifted. After the tongue is bent by the action of the pin, the tongue is then released by the pin. The actuated tongues start to oscillate substantially at their first natural frequency.

The gong of the striking watch or the pin barrel of the music watch are arranged inside the watch case. Thus, the vibration of the gong or the pin barrel tongue is transmitted to the external part of the watch. These external parts are, for example, the middle part, the bezel, the crystal and the back cover of the watch case. These large components begin to radiate sound into the air under the influence of the transmitted vibrations. When sound is generated by a gong struck by a hammer or by one or more vibrating pin barrel tongues, these external parts are able to radiate the generated sound into the air.

In a conventional striking watch or musical watch, the acoustic efficiency of the complex vibration-sound conversion based on the external parts is low. In order to increase and augment the sound level perceived by a user of a striking or musical watch, the materials, geometry and boundary conditions of the external components must be considered. The construction of these external parts also depends on the aesthetic appearance of the watch and on the working stresses, which may limit the possibilities of adaptation modifications.

It is known in the art of watchmaking to use, in watches (in particular electronic watches), a membrane of the acoustic type, which is dedicated to the vibration-to-sound conversion. To trigger a membrane of this type in an electronic watch, for example, a piezoelectric element is placed on the membrane to cause the membrane to vibrate, as described in swiss patent No. 581860. In order to prevent the sound radiation from the membrane from disappearing in the watch that must be sealed, the case may be provided with a double back cover that must be open towards the outside. In this case, the back cover of the watch case has one or more holes for transmitting sound from the diaphragm.

With this type of design of electronic watch with acoustic membrane, problems often arise related to the sealing and corrosion of the membrane. The first natural frequency of the membrane, which is the effective radiation mode, must in principle be within the useful sound band. However, the second natural frequency, which is a non-active mode, must be outside the vocal cords if possible. The useful audio band is typically between 1kHz and 4 kHz. Depending on the boundary conditions and the geometry provided for the membrane, physical properties such as density and young's modulus must allow the first and second natural frequencies to be adapted. If the membrane is made of steel, the first and second natural frequencies of vibration cannot satisfy the above conditions in an optimum manner. Furthermore, a fast decay can be observed, which is a drawback.

In general, there is a problem of frequency bandwidth for using a conventional acoustic radiating membrane. If the acoustic membrane has to be mounted on a music box, the frequency to be radiated effectively has to be typically in the range of 1kHz and 4 kHz. In the case of a striking watch with minute questions, an alarm or even a quartz alarm, good results can be obtained by amplifying a single dominant frequency tuned using an exciter.

In a standard striking watch, for example fitted with an acoustic membrane, said membrane is sandwiched between a portion of the middle case and the back cover of the watch. In the case of a luxury watch, the rear cover may be made of a valuable material such as gold. The electrochemical potential difference between the membrane, usually made of steel, and the gold rear cover can occur upon contact, especially in a humid environment. This is liable to cause corrosion of the film where the film comes into contact with the gold rear cover, which is another drawback. Therefore, a corrosion resistant material that has no potential difference from gold and has low internal damping must be found.

Disclosure of Invention

It is therefore an object of the present invention to overcome the drawbacks of the prior art mentioned above by providing an acoustic radiating membrane for a music box or a watch, which is made to provide the most uniform possible amplification over the audible frequency band, mainly in the frequency range of 1kHz to 4 kHz.

The invention therefore relates to an acoustic radiating membrane comprising the features defined in independent claim 1.

Particular embodiments of the acoustic radiating membrane are defined in the dependent claims 2 to 12.

One advantage of the sound radiating membrane according to the invention lies in the fact that it comprises a protrusion or a number of recesses, which are located over at least a first thickness which is smaller than the overall thickness of the membrane. The size and shape of these pockets or protrusions depends on the type of material of the membrane and the note or notes (note) that require effective radiation.

Advantageously, the acoustic radiating membrane is formed by at least two layers, wherein one of the layers having a first thickness is provided with a number of pockets, preferably distributed in a honeycomb-shaped arrangement. The shape and size of each pocket may depend on the note to be effectively radiated. Thus, the first layer may include a number of pockets having different sizes for effectively radiating an equal number of notes. This also increases the overall sound level, which can be perceived in this connection by a user of a music box or watch in which the sound membrane is provided.

Advantageously, the sound radiating membrane comprises a first layer with uniformly distributed hollows in a honeycomb arrangement, the first layer being fixed to a second layer without any hollows, and a third layer with honeycombed arrangement of hollows being fixed to the opposite side of the second layer. The second layer may be a layer made of gold, and the first and third layers may be made of amorphous metal or metallic glass, or may also be made of gold. Providing several layers with cavities may also increase the number of natural frequencies (i.e. between 1kHz and 4 kHz) in the useful audible band in order to increase the overall sound level. For this type of membrane, very low attenuation can be observed, which provides very good acoustic efficiency.

The invention therefore relates to a watch having an acoustic radiating membrane comprising the features defined in independent claim 13.

Dependent claims 14 to 16 define specific embodiments of the table.

Drawings

The objects, advantages and features of the acoustic radiating membrane for a music box or watch can be seen more clearly from the description given below on the basis of at least one non-limiting embodiment illustrated by the accompanying drawings, in which:

figure 1 shows a simplified and exploded three-dimensional view of the various layers forming the acoustic radiating membrane according to the present invention,

figure 2 shows a simplified three-dimensional view of the assembled individual layers forming the sound-radiating membrane according to the invention,

FIG. 3 shows a simplified partial cross-sectional view of a striking or musical watch having an acoustic membrane according to the present invention.

Detailed Description

In the following description, all those components of a music box such as a music watch or a striking watch that are well known to those skilled in the art will be described only in a simplified manner.

Fig. 1 shows a simplified three-dimensional exploded view of an acoustic radiating membrane 1 for a music box, such as a music watch or a striking watch. In this embodiment, the membrane 1 first comprises a first layer 2, said first layer 2 comprising a number of cavities 5, said cavities 5 may have the same or different dimensions. The first layer 2 may be bonded or welded to the first face of the second layer 3 without the indentation to ensure a level of sealing inside the watch when the membrane is mounted in the watch case. The third layer 4 with pockets 6 of the same or different sizes may also be bonded or welded to the second face of the second layer 3. The recesses 5 of the first layer 2 may be arranged opposite recesses 6 of the third layer 4 having the same or different dimensions. However, it is conceivable that the membrane 1 only comprises a first layer 2 having a first thickness and a second layer 3 having a second thickness. The thickness of each layer may be less than 0.2mm, preferably close to 0.1 mm.

The pockets 5,6 of the first and third layers 2, 4 are evenly spaced from each other and are configured in a honeycomb arrangement having six equal sides. Although only three cavities are shown in fig. 1, it is clear that the membrane 1 may comprise a larger number of cavities to occupy most of the surface of the acoustic membrane 1. Other pocket shapes, such as circular or oval, are also contemplated, but the honeycomb arrangement enables the surface of the membrane to optimally fill the pockets.

In order to radiate a particular note with uniform amplification in the audible band, the cavities of the first layer 2 are all of the same shape and size. The dimensions are also determined according to the materials of the first layer 2 and the second layer 3. The larger the size of the recess, the lower the corresponding frequency will be, i.e. the lower the frequency. For the same size cavity, it should also be noted that the greater the overall thickness of the membrane 1, the higher the note radiated will be. The overall thickness of the membrane 1 is in principle less than or equal to 1 mm.

However, if several notes are radiated by the acoustic membrane in a musical watch, each cavity 5,6 of the first layer 2 and/or the third layer 4 may be sized for each specific note. Thus, a set of mini-membranes is defined, each configured for effectively radiating a specific note and having a uniform amplification of the first natural frequency between 1kHz and 4 kHz. The number of cavities in the first layer 2 and/or the third layer 4 is therefore equal to the number of notes that can be produced in a musical watch. In order to effectively radiate 10 to 15 notes with the membrane, 10 to 15 cavities must be made.

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

To produce the acoustic membrane 1, it is preferred to first machine the recesses 5,6 in the first and third layers 2, 4 and then to fix said layers to the second layer 3 by gluing or welding. Recesses 5,6 are machined in the first and third layers, for example by stamping or etching.

The sound-radiating membrane 1 may be formed of more than two layers with recesses for defining a set of layers with recesses, and at least one layer without recesses interposed between two of the layers with recesses. All of these layers are bonded or welded to each other. Each layer may have the same thickness, for example in the order of 0.1mm, or different thicknesses from one another, but the total thickness of the film must in principle be less than or equal to 1mm, depending on the material chosen. Each layer having a cavity may thus be configured to radiate a certain note among several notes to be radiated by the membrane with a uniform amplification.

Fig. 2 shows a simplified three-dimensional view of the acoustic membrane 1 after all layers have been assembled. This acoustic membrane 1, for assembly in a striking watch or a musical watch, can be of circular shape with a diameter comprised between 20-40mm, and preferably close to 31 mm. It may be flat or dome shaped as shown in part in fig. 3 described below.

It should also be noted that instead of providing the first layer 2 with recesses 5 over a first thickness of the total thickness of the acoustic membrane 1, protrusions may be made over the first thickness of the membrane. These protrusions (not shown) are integral with the base of the membrane without the recess. The protrusions may also be configured in a honeycomb shape and each tuned to effectively radiate a particular note.

Fig. 3 thus shows a partial cross-section of a striking or musical watch 10. The watch 10 mainly comprises an acoustic radiating membrane 1 according to the invention for improving the acoustic efficiency of one or more notes produced by a striking mechanism. The acoustic membrane may comprise two or three layers 2, 3, 4, wherein one or both layers 2, 4 have recesses 5,6 and the intermediate layer 3 has no recesses. At least the two layers having the recesses may be made of amorphous metal or metallic glass, which is a corrosion-resistant material, while the second intermediate layer 3 may be made of gold or titanium. The thickness of the film 1 may be less than or equal to 1 mm.

Striking or musical watch 10 also includes a timepiece movement 20, which movement 20 is typically mounted on a plate 24. The edge portion 22 is fastened to a bezel 24, which defines a bezel. Typically, both the deck 24 and the rim portion 22 are made of a metallic material.

Watch movement 20 includes a striking mechanism, not shown. This striking mechanism may comprise at least one gong mounted on a gong-carrier integral with plate 24, and at least one hammer rotatably mounted on the plate for striking said gong at a determined time. A substantially circular gong surrounds the various parts of the movement of the striking watch. The setting of this striking mechanism is used to indicate the programmed alarm time or three minutes.

In a more elaborate musical watch embodiment, the striking mechanism may include a pin barrel having a set of tongues attached to a heel that is fastened to the plate 24. The vibrating tongue of the pin barrel produces a note or a series of notes. Each tongue is typically configured to produce a particular note, but there may be some set of two tongues so that each set produces the same particular note. To produce music, for example, at a programmed time, the pin barrel tabs are raised by pins integral with a rotating disk or cylinder on the plate 24 and then released. Each actuated tongue oscillates predominantly at its first natural frequency. The vibrations generated by the actuated tongues are transmitted to the external parts of the watch, which must allow the sound generated by each vibrating tongue to radiate in an acoustic sense.

In this embodiment, the acoustic membrane 1 takes the shape of a dome, the top edge of which is mounted in a sealed manner via an annular gasket 18 on the inner annular edge of the back cover 15 of the watch case. The diameter of this dome may be the same as the diameter of the crystal 12 and may be between 20-40mm, preferably approximately 31 mm. An annular support 21 supports the backplate 24 on the side having the edge portion 22 and rests on the top edge of the acoustic membrane 1. When the middle part 14 is fastened to the back cover 15 of the watch case, the support 21 and the peripheral edge of the sound-radiating membrane 1 are clamped between the middle part 14 and the edge of the back cover 15.

The rear cover 15 is removably mounted on the intermediate member 14 by known means with a sealing gasket 19. The crystal 12 is in particular fixed to the bezel 13 so as to close the case in a sealed manner. The dial 23 is held on the edge of the intermediate member and is disposed below the crystal 12. In the case of striking watch 10, the time indicating hands (not shown) are provided on a dial, which usually carries hour symbols on its periphery.

The center portion of the acoustic membrane is not in contact with the support portion 21 and the inner surface of the rear cover 15. Thus, sufficient space 17 is provided in the case to enable the acoustic membrane to vibrate freely or radiate acoustically. The acoustic membrane 1 and the back cover 15 thus together form a double back cover. One or more holes 16 are also provided laterally through the rear cover 15 to allow the acoustic membrane to radiate sound generated by the striking mechanism towards the outside.

During operation of the striking mechanism, one or more notes produced by the striking mechanism are transmitted directly to the acoustic membrane to vibrate it. The connecting portions 21, 22 and 24 also transmit vibrations to the acoustic membrane 1 at the edge of the acoustic membrane 1. Since the acoustic membrane is formed of layers made of gold or titanium or partly of amorphous metal, it is capable of vibrating at several first natural frequencies depending on the number of notes to be radiated. These first natural frequencies are preferably within the useful acoustic band between 1kHz and 4 kHz. However, the second natural frequency of vibration of the note is above 4 kHz. This is very advantageous in view of the fact that the second vibration frequency is usually acoustically harmful. These desired natural acoustic vibration frequencies of a membrane made of a partially amorphous metal depend on physical properties such as density and young's modulus. Furthermore, for this type of membrane, a very low attenuation can be observed, which provides a very good acoustic efficiency for the acoustic membrane 1.

Due to the fact that the membrane is made of a corrosion resistant material, the membrane can be mounted on a back cover, for example made of a noble metal such as gold. No electrochemical potential difference was observed even in a humid environment, which means that no corrosion occurred at the contact between the membrane 1 and the back cover 15.

The metallic glass or amorphous metal used to make the at least two layers with recesses of the membrane may be, for example, a metal alloy based on titanium, zirconium and beryllium. Thus, as a more specific example, the amorphous metal alloy may include 41% zirconium, 14% titanium, 12% copper, 10% nickel, and 23% beryllium. The Young's modulus of the alloy was 105GPa, and the elastic limit was 1.9 GPa. The amorphous metal alloy may also be formed from 57.5% platinum, 14.7% copper, 5.3% nickel, and 22.5% phosphorus. In this case the Young's modulus of the alloy was 98GPa, and the elastic limit was 1.4 GPa.

Starting from the description just given, a person skilled in the art can envisage several variants of acoustic radiating membrane for musical boxes or timepieces, without departing from the scope of the invention defined by the claims. The acoustic membrane may be located in a middle part of the watch case through which a hole is formed for sound radiation of the vibrating acoustic membrane. The acoustic membrane may also be located on an external part of the watch case but is provided in at least one aperture in the watch case so that one or more notes produced by the striking mechanism can cause the membrane to vibrate. Several acoustic membranes may be provided, which are arranged in several positions within the watch case or overlap each other. These acoustic membranes can be made with the same number or different number of pocketed layers.

Claims (15)

1. An acoustic radiating membrane (1) for a music box or striking watch (10), characterised in that it comprises a number of cavities (5) on a first thickness (2) of the total thickness of the membrane, wherein the shape and dimensions of each cavity are adapted according to the type of material and the note radiated by the membrane, the membrane comprising a first layer (2) having a first thickness and in which the cavities (5) are formed, and a second layer (3) without cavities, wherein the first layer is arranged on a first face of the second layer.

2. Membrane (1) according to claim 1, characterized in that it comprises at least one third layer (4) having a number of cavities (6), wherein said third layer is arranged on the second side of said second layer (3).

3. Membrane (1) according to claim 2, characterized in that the pockets (5, 6) are configured in a honeycomb arrangement.

4. Membrane (1) according to claim 2, characterized in that said first (2), second (3) and third (4) layers are made of different or identical metallic materials, or at least one of these three layers is made of metallic glass.

5. Membrane (1) according to claim 4, characterized in that said second layer (3) is made of gold or titanium and said first (2) and third (4) layers are made of metallic glass or gold or titanium.

6. Membrane (1) according to claim 2, characterized in that the number of cavities in said first layer (2) and/or third layer (4) is the same as the number of notes radiated by said acoustic radiating membrane in the audible frequency band and mainly for a first natural frequency between 1kHz and 4 kHz.

7. Membrane (1) according to claim 6, characterised in that the number of cavities respectively configured according to the notes radiated by said membrane is set between 10 and 15, so as to amplify in a uniform manner the 10 to 15 notes produced in a musical box or watch.

8. Membrane (1) according to claim 6, characterised in that the recesses (5) of the first layer (2) are arranged opposite identical recesses (6) of the third layer (4).

9. Membrane (1) according to claim 2, characterized in that the cavities (5) of the first layer (2) are configured to radiate a first note and the cavities (6) of the third layer (4) are configured to radiate a second note with a uniform amplification.

10. Membrane (1) according to claim 9, characterized in that it comprises a set of a plurality of layers with hollows, and at least one second layer without hollows interposed between two layers with hollows, wherein all these layers are bonded or welded together superimposed on each other, and each layer with hollows is configured to irradiate a note determined among a plurality of notes irradiated by said membrane.

11. Membrane (1) according to claim 1, characterized in that the thickness of each layer is less than 0.2mm, while the total thickness of the membrane is less than or equal to 1mm, and the membrane is circular with a diameter comprised between 20 and 40 mm.

12. A striking or musical watch (10) comprising: a watch case having a middle part (14) and a back cover (15) provided with at least one lateral hole (16), wherein the back cover is fastened to the middle part in a sealed and removable manner; a crystal (12) for closing the case in a sealed manner; a watch movement (20) held inside the watch case and having a striking mechanism that can be actuated at a determined time to produce one or more notes; and at least one sound-radiating membrane (1) according to claim 1 arranged in the watch case.

13. Watch (10) according to claim 12, characterised in that the sound radiating membrane (1) is held on the inner edge of the back cover (15) of the watch case and on one part of the middle part (14) and in that the periphery of the sound radiating membrane (1) is clamped, together with the periphery of the support (21) of the movement, between the middle part (14) and the inner edge of the back cover (15) of the watch case.

14. Watch (10) according to claim 13, characterised in that said sound-radiating membrane (1) has the shape of a dome, the top edge of which is clamped, together with the annular support, between the middle part (14) and the annular inner edge of the back cover (15) of the case, an annular sealing gasket (18) being provided between the edge of the back cover (15) and the annular edge of said membrane, and the central part of said sound-radiating membrane is not in contact with the support (21) and the inner surface of the back cover (15) of the case, so as to define a space (17) that allows the free vibration of said membrane.

15. Watch (10) according to claim 12, characterised in that a plurality of sound-radiating membranes (1) are connected to the watch case and are arranged either separately from each other or overlapping each other.