Patent Application
20200168199
The invention concerns a resonant member, which includes at least one resonant part, such as one or more gongs, or a vibration plate for a striking mechanism of a watch or of a music box. The gong or gongs or each strip of a vibration plate must be designed with a specific material to take account of the space available inside the watch case while ensuring a rich sound generated when the gong or gongs are struck, or one or more strips are activated.
The invention also concerns a method for making a resonant member.
In the field of horology, a timepiece movement may be provided with a striking mechanism, such as a minute repeater. To this end, the resonant member used includes a gong, which is a metal wire of circular shape, made, for example, of steel. This metal wire is generally disposed around the movement, inside the watch case. The gong is fixed, for example by welding or soldering, to a gong-carrier, which is itself integral with the main plate or the middle part of the watch case. The gong vibration is generated by the impact, generally in proximity to the gong-carrier, of at least one hammer. This vibration is composed of several natural frequencies or partials, the number and intensity of which, especially in the audible range between 1 kHz and 20 kHz, depend on the geometry of the gong and the physical properties of the material used.
The gong in the form of a metal wire can also be made of gold, as defined in European Patent No. EP 2 107 436 B1, in order to have a large number of partials in the sound vibration generated by the hammer strike. Although making a gong from gold provides great richness for the sound generated when the striking mechanism hammer strikes, it may undergo excessive deformation due to its own weight. Since space may be limited inside the watch case where the gong is located, it can easily come into undesired contact with adjacent components. This constitutes a drawback of a gong made of gold or any metal with high density and a low modulus of elasticity.
In such conditions, noise insulators could be placed around the gong or gongs of the mechanism to prevent such inadvertent shocks or ringing. However, space is greatly reduced in conventional watches for noise insulators to also be added between the gong or gongs, while ensuring richness of the sound generated when the gong or gongs are struck at desired times.
Naturally, a timepiece movement can also include a striking mechanism to generate music if the mechanism is activated. To this end, the mechanism may include a resonant member in the form of a musical vibration plate. The strips made of metallic material can be activated by pins disposed on a disc or cylinder driven in rotation during activation of the striking mechanism. The same drawbacks as for an arrangement of one or more gongs made of an aforementioned material can be observed in the case of a vibration plate with metal strips.
It is also to be noted that, in a conventional musical or striking watch, acoustic efficiency, based on the complex vibroacoustic transduction of the external parts, is low. In order to improve and increase the acoustic level of a sound or a note, the geometry and boundary conditions of the external parts must be considered. The configuration of the external parts is also dependent on the aesthetics of the watch and operating constraints, which may limit possibilities of adaptation.
U.S. Pat. No. 1,700,506 A discloses a clock, which includes a striking mechanism with gongs each capable of being struck by a hammer to indicate an alarm time or to strike the passed hours, for example. According to one embodiment, each gong can be made from a copper alloy with at least 60% copper and further containing nickel and zinc. Although it is mentioned that good sound quality is obtained with such a copper alloy, it is not suitable to be placed inside a watch with a striking mechanism in order to generate a rich sound in a reduced space for vibration of the gong or gongs, while preventing any inadvertent impact of the gongs in the rest mode of the striking mechanism, which constitutes a drawback.
U.S. Pat. No. 377,918 A discloses a metal alloy composed of at least 67% copper in order to be used to make a vibrating body for musical instruments. However, it is not suitable for making striking mechanism gongs in a watch in order to generate a rich sound when they vibrate in a reduced space, while preventing any inadvertent impact of the gongs in the rest mode of the striking mechanism, which constitutes a drawback.
It is therefore an object of the invention to overcome the drawbacks of the state of the art by providing a resonant member, which includes one or more gongs or a vibration plate for a striking mechanism of a watch or of a music box, exhibiting less deformation due to its own weight and capable of producing a rich, warm and loud sound once activated in a reduced space inside the watch or music box.
To this end, the invention also concerns a resonant member, which includes the features defined in the independent claim 1.
Specific embodiments of the resonant member are defined in the dependent claims 2 to 14.
One advantage of the resonant member lies in the fact that it is made from a copper alloy containing more than 70% by weight of copper. Further, preferably, a copper alloy is chosen with a ratio E/p of Young's modulus E to density or volume mass p which is close to that of gold. Ratio E/p must, for example, be less than 28·106 (m/s)2. Once activated, this makes it possible to generate a rich loud sound having a large number of partials in the audible range from at least 1 kHz to 10 kHz.
Advantageously, the resonant member can comprise a resonant part connected in one piece to an attachment part. The resonant part may comprise one or more gongs and the attachment part may be defined as a gong-carrier connecting one or more gongs, or one gong-carrier per gong.
Advantageously, the resonant member, which includes one or more gongs, is intended to be made in such a way as to minimise any deformation thereof due to its own weight once mounted inside a watch case and with a reduced space for the positioning of the gong(s). The gong(s) can also be made of a copper alloy with a hardness of more than 150 HV, and preferably more than 300 HV.
Advantageously, the resonant member may be a musical vibration plate formed of several strips connected to a same bar-like portion in one-piece. Each strip or each group of strips can be made to each produce a well-defined note once activated.
To this end, the invention also concerns a method for making a resonant member defined in the independent claims 15 and 16.
The objects, advantages and features of a resonant member, which includes one or more gongs or a vibration plate for a striking mechanism of a watch or of a music box will appear more clearly in the following description, particularly with reference to the drawings, in which:
In the following description, all the parts of a striking mechanism, which includes a resonant member of a striking or musical watch, which are well known in this technical field will be only briefly described. The emphasis is mainly on the resonant member and the making thereof for the striking mechanism in the watch case, or in a music box.
Attachment part 3 may be of the same thickness as the thickness of gong 2 and includes pierced holes for the attachment, for example by means of screws, of gong 2 to a corresponding portion of a middle part of the watch case or of a plate of the timepiece movement. Attachment part 3 may also have a different shape and a different thickness or be integral with a portion of the watch case middle.
Gong 2 of the watch striking mechanism may be disposed inside the watch case, preferably underneath a watch dial and, in one embodiment, partly around a timepiece movement. In these conditions, it may be circular in shape with a diameter corresponding to the diameter of the watch crystal and describing a circular sector with an angle which may be between 150° and 250°, preferably between 185° and 220°. Gong 2 may have a circular or preferably rectangular cross-section in the Figures shown. Exemplary dimensions are described below without limitation to the examples described.
Gong 2, secured by attachment part 3 inside the watch case, generally forms part of a striking mechanism, which also preferably includes a hammer for striking the gong at predetermined times. An impact portion of the hammer (not represented) generally strikes the gong in proximity to the connection thereof to attachment part 3 to generate acoustic resonance.
Depending on the material used to make resonant member 1, there may be a significant deformation of resonant part 2 once resonant member 1 is secured inside the watch case or inside the music box. Once secured, resonant part 2 may bend, i.e. deform as a function of its own weight, even when the watch is at rest. In the case of a resonant part 2 formed of one or more gongs and since the space where the gongs are situated is very limited, any movement or impact of the watch can cause the gong(s) 2 to come into contact with an adjacent gong or a close watch component. This may lead to undesired ringing of the gong(s) independently of the normal activation thereof at determined times, which is not desired.
Thus,
In a rest mode, gong 2, describing a circular sector, is deflected by a distance d seen in elevation from its attachment part 3 at its free end. Depending on the space reserved for the gong or for a set of gongs in the watch case, such a gong 2 with a diameter, for example, on the order of 35 to 40 mm on a circular sector between 185° and 220° for the note G for example, and with a thickness and width greater than or equal to 0.4 mm, preferably close to 0.5 mm, must have a deflection distance d that is less than 20% of its cross-section, i.e. less than 0.1 mm in the case of the present invention.
As indicated above according to the present invention, resonant member 1 with one or more gongs 2 is made from a copper alloy with more than 70% by weight of copper in the alloy and whose ratio E/p is smaller than 28·106 (m/s)2. Further, said copper alloy could also be made with a hardness of more than 150 HV. A list of materials is indicated below.
The table below summarizes the criteria, which correspond to 5N gold and to alternative materials, which comprise, in particular, at least 70% by weight of copper:
Purely by way of non-limiting illustration, a gong 2 can be made that produces a note G when struck by a hammer of the striking mechanism. Gong 2 can be made from a copper-titanium-iron alloy where the proportion of copper is more than 95% by weight. The Young's modulus E is equal to 120 GPa, density p is 8.7 g/cm3 and the hardness is on the order of 280-300 HV. The length of the gong with a diameter of around 35 to 40 mm and a circular sector with an angle of 185.84° and ratio E/p is equal to 13.8·106 (m/s)2. In this case a deformation or deflection of the gong due to its own weight on the order of 0.0734 mm is observed, which is less than 0.1 mm, which is desired.
It is also possible to define the deformation formula of a fixed beam, which deforms under its own weight. The beam deformation formula can be taken as an example to determine the deformation of a gong 2 of a resonant member 1 of more complex shape. Thus, the formula for calculating the deformation of this type of system, for a rectangular beam section, is as follows:
f
l
=p·L
4/(8·E·l)
where L is the length of the beam, p is the weight of the beam per unit of length, E is the Young's modulus, and l=b·h3/12 for a rectangular cross-section where b is the width of the beam and H the height of the beam.
In our case, the gong(s) 2 are curved elements. The gong deformation calculation thus consists in extrapolating the formula initially adapted to an aforementioned fixed beam. This calculation is thus much more complex for gongs and therefore requires one calculation per finished element.
The length of at least one gong 2 is related to the desired resonance frequency:
fn=(½π)·(βn·L)2·(b/L2)·(E/(12·ρ))1/2
where ρ the density of the material, βn·L=((2n−1)/2)·π for n>5, n being the mode number.
This equation is valid for the vibration modes, which are in the striking plane. The ratio E/ρ is specific to the material of the gong. The smaller this ratio, the more partials there are and thus the richer the sound. A rich sound is heard more loudly by the human ear. Thus, with the choice of gong material, ratio E/ρ must be as small as possible and if possible close to that of gold.
It is also to be noted that changing the material for a material that deforms less than gold also makes it possible to optimise space inside the watch case. If the material deforms less, a saving can also be made in the diameter of the watch case and the thickness of the gong(s). It is possible to make resonant member 1 from bronze, which includes more than 70% by weight of copper.
The alloy with more than 70% by weight of copper can also contain one or more of the following elements: tin (Sn), phosphorus (P), iron (Fe) zinc (Zn), titanium (Ti), beryllium (Be), nickel (Ni), aluminium (Al), manganese (Mn), silicon (Si), zirconium (Zr), chromium (Cr). These alloying elements can, for example, augment the mechanical properties and/or resistance to corrosion of the alloy. These elements can also be selected as a function of their phase diagram with the copper element (Cu). It may be advantageous to obtain certain phases for machinability and/or for acoustic properties.
The copper alloy with more than 70% by weight of copper can also contain palladium (Pd), silver (Ag), tellure (Te), sulphur (S), cadmium (Cd), or arsenic (As).
The Young's modulus can be comprised between 80 and 150 GPa and the specific mass or density may be greater than 5 g/cm3.
Resonant member 1, which may consist of one or more gongs 2, 2′, 2″, 2′″ can be made by milling, electroerosion, laser machining, cutting/stamping or another suitable machining method in this technical field. The gong or gongs 2, 2′, 2″, 2′″ can also be produced from cast products or hot pressed products or hot or cold deformed products. This means that gongs 2, 2′, 2″, 2′″ may be anisotropic or isotropic. These features can have an effect on the acoustic properties.
Resonant member 1 can undergo a heat treatment in order to augment its mechanical properties, its resistance to corrosion and/or its acoustic properties, for example. Further, resonant member 1 may enjoy a surface treatment forming a surface layer of the alloy containing more than 70% by weight of copper, which makes it possible to improve corrosion resistance and/or surface hardness, for example. The thickness of this additional layer on the basic element could be comprised between 10 nm and 200 μm. This additional layer can also serve as protection for the basic element particularly against corrosion.
First gong 2 can be located just underneath a watch dial 4, while second gong 2′ is underneath the first gong and above an inner edge 5′ of watch case middle 5. A junction portion 6 connects the dial to case middle 5. A reduced space 10 is provided for the placement of gongs 2, 2′, but does not guarantee that gongs 2, 2′ will not knock against each other or inadvertently come into contact with the edge of vibration space 10. This depends on the material used to make them, such as a copper alloy containing more than 70% by weight of copper.
Each gong 2, 2′ has a width l1 greater than or equal to 0.4 mm. The first gong 2 is separated from dial 4 by a height h1 having approximately the value of its cross-section. The second gong is separated by a height h2 having a value less than twice its cross-section from first gong 2 without deformation. Finally, the second gong is separated by a height h3 having approximately the value of its cross-section from lower and inner edge 5′ of case middle 5. The first and second gongs 2, 2′ are separated from case middle 5 by a distance d1 less than or equal to twice the value of their cross-section.
Naturally other values of the dimensions of the gongs can be applied according to the dimension of the watch provided with the striking mechanism.
Two resonant parts 2 or more could be connected to a single attachment part 3. In the case of a resonant member 1 composed of gongs 2, one or more gongs 2 may be connected to a same attachment part 3, such as a gong-carrier 3, whereas other gongs 2 can each be connected to their specific different attachment part 3, such as to their own gong-carrier 3.
It is also to be noted that resonant member 1 is adapted with the material chosen to accord with the material of the external parts in order to obtain better sound transmission between the vibrating gong(s) and the adjacent external parts.
All that has been described for a resonant member 1 with one or more gongs can be applied in the same manner to a resonant member 1 in the form of a vibration plate in order to play a melody once activated.
From the description that has just been given, several variants of the resonant member for a striking mechanism of a watch or of a music box can be devised by those skilled in the art without departing from the scope of the invention defined by the claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 18207834.5 | Nov 2018 | EP | regional |
