Patent Application
20090278670
This application claims priority from Swiss Patent Application No. 00520/08 filed Apr. 4, 2008, the entire disclosure of which is incorporated herein by reference.
The invention concerns a gong of specific geometry for the striking work or alarm of a watch.
In the field of horology, a conventional architecture is used for making movements, which are fitted with striking mechanisms, such as minute repeaters. In such embodiments, the gong used is a metal wire, which may have a circular shape. This metal wire is arranged around the movement, in the watch frame. The gong is secured, for example by hard soldering, to a gong-carrier, which is itself secured to the watch plate. The gong vibration is produced by the impact of at least one hammer, generally in proximity to the gong-carrier. This vibration is made up of several natural frequencies (or partials), the number and intensity of which, in particular within the audible range, depend upon the geometry of the gong and the physical properties of the gong material.
Generally, to produce a musical sound whose pitch is fixed in the entire sound spectrum, there is a fundamental frequency, which is also called the first harmonic, and one or several harmonics, which are whole number multiples of the fundamental frequency. In other cases, where frequencies higher than the fundamental frequency are no longer whole number multiples of the lowest frequency, such frequencies are termed partials. A sound with several partials is usually encountered in percussion instruments or some string instruments, or during strike transients, such as the shock or impact of a hammer against the gong of a watch striking work, as for the present invention.
A certain proportion of partials is audible within the 1 kHz to 20 kHz frequency range, when the hammer strikes the gong (the lower limit being given by the radiation capacities of the watch, whereas the upper limit is the auditory capacity of the human ear). Within this frequency range, the larger the number of partials, the richer the generated sound will be considered. Using one type of gong material, it is only possible to increase this richness of sound by altering the geometry of the gong, i.e. for example by making a cathedral type gong. This type of gong includes two windings instead of a single winding around the watch movement, which may cause a problem of space within the watch case.
As indicated above, a gong for the striking work of a watch can include a metal wire of circular shape surrounding one part of the watch movement, as shown, in part, in WO Patent No. 2006/095244. This metal wire may be made, for example, of steel, to produce a vibration, which thus includes several partials within the audible frequency range. However, it has been observed that with a steel gong of a given geometry, the number of partials within the audible frequency range is insufficient for the vibrating gong to produce a rich sound, in particular in the low frequencies.
It is thus an object of the invention to overcome the drawbacks of the state of the art by providing a gong for the striking work or alarm of a watch that can produce a rich sound having a large number of partials within the audible frequency range.
The invention therefore concerns the aforecited gong for the striking work or alarm of a watch, which includes the features defined in the independent claim 1.
Particular embodiments of the gong for the striking work of a watch are defined in the dependent claims 2 to 6.
One advantage of the gong according to the present invention, which is made of a material with a specific relation between elasticity module and volumic mass, is that the sound produced is richer for a given size of said gong compared to previously used materials, such as steel. It is possible to produce a cathedral type sound, by using a single metal wire winding in the watch case, and not two windings, as in the state of the art. The acoustic intensity is improved because of the increase in the transmission coefficient to the watch parts located downstream of the gong. By selecting a type of material, such as a precious metal, the quality of the sound produced by the gong is improved, because of the larger number of partials that can propagate towards the radiating parts of the watch.
The objects, advantages and features of the gong for the striking work or alarm of a watch will appear more clearly in the following description, particularly with reference to the drawings, in which:
The gong of the present invention is made of a type of material that increases the richness of the sound produced by the vibration of said gong with a high number of audible partials. This high number of partials is determined within the audible frequency range, i.e. from 1 kHz to 20 kHz. The material may mainly have an amorphous structure, such as a metallic glass.
In addition to the well-defined geometric shape, the selected material must thus enable the mode density η in the audible frequency range to be controlled and optimised. This mode density is influenced by various parameters, including, mainly, the properties of the selected material. Mode density η is inversely proportional to the square root of the elasticity module E of the material, divided by the volumic mass ρ of said material in accordance with the following formula:
1/ηα(E/ρ)1/2[m/s]
However, the speed of the sound produced by the gong is directly proportional to the square root of elasticity module E divided by the volumic mass ρ, which is defined in m/s.
The type of material used for making a watch gong can advantageously be selected from among precious metals, such as yellow gold, grey gold, red gold, platinum, palladium and silver, for example. For yellow gold, the value of the square root of elasticity module E divided by the volumic mass ρ is 2222 m/s; for a gong of standard geometry, with up to 11 audible partials. For grey gold, this value is 2606 m/s with around 10 audible partials. For red gold, this value is 2556 m/s with around 10 audible partials. For platinum, this value is 2822 m/s with 9 to 10 audible partials. For palladium, this value is 3172 m/s with around 9 audible partials. For silver, this value is 2813 m/s with 9 to 10 audible partials.
As can be seen from the values stated above, the value, for all of these precious metals, of the square root of elasticity module E divided by volumic mass ρ is less than 3300 m/s. By way of comparison, if the gong is made, in a conventional manner, of 20AP steel or piano wire, this value is higher than 5000 m/s with 7 partials in the audible frequency range. If diamond is used as gong material, this value is higher than 16850 m/s with only 4 audible partials. This clearly demonstrates that making a gong of standard geometry with a precious metal guarantees that the vibrating gong will produce a rich sound with a high number of audible partials and without producing a cacophonous sound.
It should also be noted that, advantageously, with a gong made of a precious metal, such as gold, the number of partials is even higher relative to the number of partials of a steel gong, in particular within the range of 1 kHz to 10 kHz, which is the zone of maximum sensitivity for the human ear.
In addition to using these precious metals, one could also envisage using a material with an amorphous, rather than a crystalline structure, which could be a metallic glass. The metallic glass may be manufactured from a molten state by rapid quench. The metallic glass may be, for example, zirconium, gold or platinum based, or based on any other metal that can solidify in amorphous form. For technical details relating to the method of making an article using an amorphous metal or alloy, the reader may refer to WO Patent No. 2003/064076, which is incorporated herein by reference. Moreover, the reader may also refer to WO Patent No. 2004/047582, which describes a precious metal alloy for making a piece of jewelery, and to WO Patent No. 2006/045106, which describes an amorphous alloy, including, for example, gold with palladium, platinum and silver, these two Patent documents being incorporated herein by reference.
The gong of specific geometry for the striking work or alarm of a watch may be a metal or metallic glass wire of rectangular or circular section, with a diameter of less than 1 mm, for example of the order of 0.6 mm. This metallic wire is secured to a gong-carrier connected to the watch plate, and may partially surround the watch movement, which may have a diameter of the order of 12′″½. The metal or metallic glass wire of the gong thus describes a single winding in the form of a toroid portion with an angle comprised, for example, between 180° or less, and 360°, and preferably of the order of 330°.
The gong with the above shape may thus advantageously be made of a material, wherein the square root of elasticity module E divided by the volumic mass ρ, is less than 3300 m/s. This material may preferably be yellow gold, grey gold, or red gold, which is easy to work to obtain said gong, and has a high number of partials mainly in the 1 kHz to 10 kHz range. With the gong thus formed of a single winding of precious metal wire, it is possible to produce a “cathedral” type sound, which makes the gong more compact for mounting in a watchcase. With a steel gong, there must be two metal wire windings to achieve the same type of sound.
In order to demonstrate properly the advantage of using a material such as gold instead of the conventional steel for making a gong of the shape indicated above,
In
It should be noted that, in addition to the selected material, such as a precious metal, account must be taken of the geometry of said gong so as to avoid having two peaks that are too close to each other in the audible frequency range, since, in such case, a dissonant sound may be perceived. The gong geometry must thus be optimised, in order to prevent such double peaks in the audible frequency range. For example, filing can be carried out close to the place where the gong is secured.
From the description that has just been given, those skilled in the art can use several materials, other than precious metals, which satisfy the conditions stated above, to make a gong of specific geometry for the striking work of a watch, without departing from the scope of the invention as defined by the claims. These selected materials must allow at least 8 partials to be perceived within the audible frequency range. The selected material may be a non-precious alloy that satisfies the above conditions. It should be noted that other properties, in particular the intrinsic quality factor, govern the choice of a material for making a gong.
| Number | Date | Country | Kind |
|---|---|---|---|
| 00520/08 | Apr 2008 | CH | national |
