EP2107436A2 - Gong for a striking mechanism or an alarm in a timepiece - Google Patents

Abstract

The gong has a determined geometry shape made with material whose ratio-square root of an elasticity module divided by a density of a chosen material is lower than 3300 meter per seconds, where the gong is made of precious metallic wire. The material is precious metals or alloy of precious metals, where the precious metals are chosen from yellow gold, grey gold, red gold, platinum, palladium or silver.

Description

The invention relates to a specific geometry stamp for a bell or alarm of a watch.

In the field of watchmaking, a traditional architecture is used to perform movements, which are provided with striking mechanisms, such as minute repetitions. In these embodiments, the stamp used is a wire, which may be circular. This wire is arranged around the movement, in the watch cage. This stamp is fixed, for example by solder, to a stamp holder, which is itself secured to the watch plate. The vibration of the stamp is produced by the impact generally near the stamp holder of at least one hammer. This vibration is composed of several eigenfrequencies (or partial), whose number and intensity, especially in the audible range, depend on the geometry of the timbre and the physical properties of the material.

Generally for the production of a fixed height musical sound throughout the sound spectrum, there is a fundamental frequency, which is also called first harmonic, and one or more harmonics, which are integer multiples of the fundamental frequency. In other cases where the frequencies above the fundamental are no longer integer multiples of the lowest frequency, they are rather defined by partials. We mainly encounter a partial sound in percussion instruments or certain stringed instruments, or during attack spikes, such as the shock or the impact of a hammer against a timbre of a watch ring as for the present invention.

A certain proportion of partials during the impact of the hammer on the timbre is audible in the frequency range of 1 kHz to 20 kHz (the low limit being given by the radiation capabilities of the watch, while the high limit is the auditory ability of the human ear). In this frequency range, the more the number of partials is important and the more the generated sound can be considered rich. With a type of stamp material used, it is possible to increase this richness of the sound by playing on the geometry of the stamp, that is to say by realizing for example a stamp of the cathedral type. This type of stamp includes two windings instead of a single winding around the movement of the watch, which can cause a problem of size in the case of the watch.

As indicated above, a bell for a ring of a watch may comprise a circular-shaped wire surrounding part of the movement of the watch as shown in part in the patent document. WO 2006/095244 . This wire may be made for example of steel to produce a vibration, which thus comprises several partials in the audible frequency range. However, it can be seen with such a steel stamp of given geometry that the number of partials in the audible frequency range is insufficient to produce a rich sound generated by the vibrating tone, particularly in the low frequencies.

The invention therefore aims to overcome the disadvantages of the state of the art by providing a timbre for a ringtone or watch alarm capable of producing a rich sound having a large number of partials in the audible frequency range.

For this purpose, the invention relates to a bell for a bell or alarm of a watch cited above, which comprises the characteristics defined in the independent claim 1.

Particular embodiments of the timbre for a bell of a watch are defined in the dependent claims 2 to 4.

An advantage of the stamp according to the present invention, which is made in such a material, is that the sound produced is richer for a given size of said stamp compared to previously used materials, such as steel. It is possible to produce a cathedral type sound with this time a single winding of a metal wire in the case of a watch and not two windings as in the state of the art. The acoustic intensity is improved by increasing the transmission coefficient to parts of the watch, located downstream of the stamp. With the type of material chosen, such as a precious metal, the quality of sound produced by the timbre is improved, thanks to the greater number of partials that can spread to the radiating parts of the watch.

• la figure 1 représente un graphique de la densité spectrale du son émis par un timbre en acier en vibration dans la gamme de fréquences audibles, et
• la figure 2 représente un graphique de la densité spectrale du son émis par un timbre en or selon l'invention en vibration dans la gamme de fréquences audibles.

The purposes, advantages and characteristics of the timbre for a bell or alarm of a watch will appear better in the following description especially with regard to the drawings in which:

• the figure 1 represents a graph of the spectral density of the sound emitted by a vibrating steel patch in the audible frequency range, and
• the figure 2 represents a graph of the spectral density of the sound emitted by a gold tone according to the invention in vibration in the audible frequency range.

The stamp of the present invention is made in a type of material, which increases the richness of the sound produced by the vibration of said stamp with a high number of audible partials. This high number of partials is determined in the audible frequency range, i.e. from 1 kHz to 20 kHz.

In addition to the well-defined geometrical shape, the chosen material must therefore make it possible to control and optimize the density of modes η in the audible frequency range. This density of modes is influenced by various parameters, mainly the properties of the selected material. The density of modes η is inversely proportional to the root square of the modulus of elasticity E of the material, divided by the density ρ of said material according to the following formula: $$\mathrm{1}\mathrm{/}\mathrm{\eta \; \alpha }{\left(\mathrm{E}\mathrm{/}\mathrm{<figure-callout\; id="1"\; label="\rho "\; filenames="imgf0002.png"\; state="\{\{state\}\}">\rho </figure-callout>}\right)}^{\mathrm{1}\mathrm{/}\mathrm{2}}\left[\mathrm{m}\mathrm{/}\mathrm{s}\right]$$

On the other hand, the velocity of the sound produced by the patch is directly proportional to the square root of the modulus of elasticity E divided by the density ρ, which is defined in m / s.

The type of material used for producing a watch stamp may advantageously be chosen from precious metals, such as yellow gold, gray gold, red gold, platinum, palladium and silver. example. For yellow gold, the value of the square root of modulus of elasticity E divided by density ρ is 2'222 m / s; with a standard geometry stamp, up to 11 audible partials. For gray gold, this value is 2'606 m / s with about 10 audible partials. For red gold, this value is 2'556 m / s with about 10 audible partials. For the stage, this value is 2'822 m / s with 9 to 10 partial audible. For palladium, this value is 3'172 m / s with about 9 audible. For the money, this value is 2'813 m / s with 9 to 10 partial audible.

As can be noticed by the values stated above, all these precious metals have a value of the square root of the modulus of elasticity E divided by the density ρ lower than 3'300 m / s. For comparison, if the stamp is made traditionally with 20AP steel or piano wire, this value is greater than 5'000 m / s with 7 partials in the audible frequency range. In the case of diamond as another type of stamp material, this value is greater than 16'850 m / s with only 4 audible partials. This shows that the realization of a stamp of geometry standard with a precious metal guarantees the obtaining of a rich sound of the timbre in vibration with a high number of audible partials and without producing a cacophonic sound.

It should also be noted that advantageously the number of partials with a stamp made of a precious metal, such as gold, is even more important in relation to the number of partials of a steel stamp particularly in the range of 1 kHz to 10 kHz, which is the area of maximum sensitivity of the human ear.

The geometry stamp determined for a bell or watch alarm may be a wire of rectangular or circular section with a diameter of less than 1 mm, for example of the order of 0.6 mm. This wire is fixed on a stamp holder connected to the watch plate, and may partially surround the watch movement, which may be of a diameter of the order of 12 '' '½. The metal wire of the stamp thus describes a single winding in the form of a portion of torus angle included for example between 180 ° or less, and 360 °, preferably of the order of 330 °.

The stamp having the form above can therefore advantageously be made of a material whose square root of the modulus of elasticity E divided by the density p is less than 3'300 m / s. This material may be preferably yellow gold, gray gold or red gold, which is easy to work for obtaining said stamp, and has a high number of partials mainly in the range of 1 kHz at 10 kHz. With only one winding of the precious metal wire of the stamp thus produced, it is possible to produce a sound of the "cathedral" type, which makes it possible to gain in the size of such a stamp to be mounted in a watch case. With a steel stamp, it is necessary to make two windings of the wire to have a sound of the same type.

To show the advantage of using a material such as gold compared to traditional steel for the realization of a stamp of form indicated above, the figures 1 and 2 show two graphs of the spectral density of the sound emitted by a vibration tone in the frequency range from 1 kHz to 20 kHz. The figure 1 represents such a stamp made of steel, while the figure 2 represents such a stamp made of gold. In these figures, we can notice peaks corresponding to the audible partials of the sound produced by the vibrating timbre. The more the number of these peaks or partial is large and the sound produced is normally rich for auditory perception by a human ear.

To the figure 1 , we can count 7 audible partials of the steel stamp, which gives a density of modes η = 0.37 kHz ^-1 . On the other hand, figure 2 , we can normally notice at least 9 audible partials of the gold tone, which gives a density of modes η = 0.47 kHz ^-1 . A gain of about 30% can be seen with a gold tone compared to a traditional steel stamp, and a shift towards low frequencies (for a given geometry).

It should be noted that in addition to the chosen material, such as a precious metal, the geometry of said stamp must be taken into account in order not to have two peaks too close to each other in the frequency range audible, because in this case a dissonant sound can be perceived. This geometry of the stamp must therefore be optimized to also avoid these double peaks in the audible frequency range. It can be operated for example a picture near the place where the stamp is fixed.

From the description that has just been given, several other materials, only precious metals, fulfilling the conditions previously stated can be used by those skilled in the art to make a stamp of geometry determined for a ring of a watch without departing from the scope of the invention defined by the claims. These selected materials must be able to perceive at least more than 8 partials in the audible frequency range. The chosen material may be a non-precious alloy fulfilling the stated conditions. It should be noted that other properties, including the intrinsic quality factor, govern the choice of a material for producing a stamp.

Claims (4)

Geometry stamp determined for a bell or alarm of a watch, characterized in that the stamp is made of a material whose square root of the ratio between the modulus of elasticity of the material divided by the density of the selected material is less than 3'300 m / s, to allow the vibrating tone to produce a rich sound consisting of several audible partials in a range of audible frequencies from 1 kHz to 20 kHz. Stamp according to claim 1, characterized in that the material used is a precious metal or an alloy of precious metals. Stamp according to Claim 2, characterized in that the precious metal is chosen from yellow gold, gray gold, red gold, platinum, palladium or silver. A stamp according to one of the preceding claims, said stamp being a precious metal wire, a portion of which defines a portion of a circle angle of between 180 ° and 360 ° to be arranged around a movement of the watch to the inside of the watch case, characterized in that it is designed in such a way that the sound produced by the vibrating tone comprises a number of audible partials greater than or equal to 8.

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