HK1219545B - Escapement system for timepiece - Google Patents

Description

Escapement system for a timepiece

The present application is a divisional application of patent application No. 201180031085.4(PCT/EP2011/060511), which was filed 2011, 6 and 22, entitled "escapement system for timepiece".

Technical Field

The present invention relates to an escapement system. The escapement system comprises an anchor equipped with a (munie) fork for cooperating with a pin mounted on a pallet and a lever comprising an arm for receiving a pallet stone for cooperating with at least one escape wheel.

The technical field of the invention is that of precision machines, and more specifically that of watchmaking.

Background

The timepiece comprises an energy source, such as a barrel, which supplies energy to the parts and in particular to the gear train. These gear trains cooperate with the escapement system via an escape wheel. The rotation of the escape wheel is regulated by the anchor of the escapement system, the impulse of which is provided by the sprung balance. The escapement system includes an anchor mounted to pivot on an axis. The anchor pallet comprises a lever fitted at a first end with a fork for cooperating with a pin mounted on the pallet, and fitted at a second end with an arm for receiving a pallet stone for cooperating with the escape wheel. During its operation, the anchor pallet pivots on its axis in such a way that: i.e. bringing the pallet stone of the arm into contact with the tooth of the escape wheel in order to control the rotation of the train.

Currently, escapements are inefficient. In fact, the operation of the escapement system involves friction, taking up impacts and taking up the dissipation of energy in the material forming the wheel and in particular the anchor. One material used is for example 15P or 20AP steel. These materials are crystalline materials. One disadvantage of components made of crystalline materials is that: when high stresses are applied, they have low mechanical strength. In fact, each material is characterized by its young's modulus E, also called the elastic modulus (usually expressed in GPa)) And characterizing the deformation resistance of the alloy. Each material is further defined by its elastic limit σ_eCharacterized (usually expressed in GPa) and the elastic limit represents the stress beyond which the material plastically deforms. Thus, for a given size, one can establish the ratio σ of their elastic limit to their Young's modulus_eCompare materials, the ratio represents the elastic deformation of each material. Therefore, the larger the ratio, the higher the limit of elastic deformation of the material. Typically, for Cu-Be alloys, for example, the Young's modulus E is equal to 130GPa, the elastic limit σ_eIs equal to 1GPa, thus σ_eThe ratio of/E is about 0.007, i.e., a very small ratio. Therefore, parts made of crystalline metals or crystalline alloys have limited elastic deformability.

Furthermore, during impacts, which are impacts between the escape wheel and the pallet stone of the anchor pallet and between the pin and the mouth of the pallet, the efficiency of the escapement is linked to its energy recovery coefficient (facteur derestimator l' nergie).

The kinetic energy accumulated during the movement of the anchor or escape wheel depends on the moment of inertia, which is a function of the mass and of the radius of gyration (and therefore also of the size).

Since the maximum energy that can be elastically stored is calculated as the elastic limit σ_eThe square of and young's modulus E, the low elastic limit of crystalline metals results in low energy storage capability. The density of 15P or 20AP steel is high and therefore the mass of the anchor and escape wheel is large. Therefore, the rotational inertia is high and the kinetic energy accumulated during the movement of the anchor and the escape wheel is large.

However, since crystalline metal cannot store a large amount of energy, energy losses occur during the impact of the lift (levee)/tooth of the escape wheel and during the impact between the pin and the fork of the disc.

Consequently, during the operation of the timepiece, a significant part of the energy output by the barrel is lost, thus reducing its energy reserve.

Furthermore, the watchmaking industry has traditionally used quenched and tempered carbon, sulphur and lead steels which have good machinability and very good mechanical properties, but are magnetic. Non-magnetic alternative materials are rare and generally more difficult to process and have poor mechanical properties.

From patent document EP 1696153, a precision gear train made of amorphous metal is known, in particular for a timepiece. This document relates to gear trains cooperating with each other by interlocking. This means that in the case of two gear trains cooperating with each other, the teeth of each gear train enter the space between the teeth of the other gear train. Thus, there is a process in which the teeth push and slide to cause the gear train to rotate. The sliding process involves materials having a surface that is both hard and strong and has a very smooth surface to prevent friction that leads to reduced efficiency and premature wear.

Since the escape wheel does not work according to the same principle, it differs from the classical gear train. In fact, this escape wheel is driven by a spring and its rotation is controlled by an escapement system which, using a balance spring, an anchor and a pallet stone, sequentially releases and stops the rotation of said escape wheel. Thus, after the release and impulse phases, the escape wheel tooth is heavily resting on the locking face of the pallet stone of the anchor. These heavy impacts are repeated with each impact, which produce very different stresses on the escape wheel compared to the gear train.

Therefore, the escape wheel must be made of a material with a high elastic limit to prevent any plastic deformation during these repeated impacts. Furthermore, during the impulse phase, when the tooth of the escape wheel is located on the impulse plane of the anchor, the escape wheel must transfer the maximum amount of energy to the anchor so that the anchor can return energy to the balance. It is therefore important that the material used for the escape wheel has an energy recovery coefficient as high as possible, in order to reduce the energy losses and therefore increase the efficiency of the system.

It will therefore be understood that the skilled person, trying to construct an escape wheel with improved efficiency, has no motivation to use documents relating to classical gear trains using materials with desired properties different from those of the escape wheel.

Disclosure of Invention

The object of the present invention is to overcome the drawbacks of the prior art by proposing an escapement system with greater efficiency that is easier to form.

On this basis, the invention relates to an escapement system as described above, characterized in that at least one part of the escapement system is made of a metal alloy that is at least partially amorphous.

A first advantage of the invention is that it allows an escapement system with a better energy recovery coefficient than current escapements. In fact, amorphous metals are characterized by the fact that, during their formation, the atoms forming these amorphous materials are not arranged according to a specific structure, as crystalline materials do. Therefore, even if the Young's modulus E of the crystalline material and that of the amorphous metal are substantially the same, their elastic limit σ is_eIs different. The amorphous metal is therefore characterized by: its elastic limit sigma_eAElastic limit sigma of specific crystalline metals_eCTwo or three times higher. Increase of elastic limit sigma_eSo that σ is_ethe/E ratio increases, increasing the stress limit beyond which the material cannot return to the original form, and above all, the maximum energy that can be stored and elastically recovered.

Another advantage of the invention is that it enables very easy shaping to be achieved, allowing parts with complex shapes to be manufactured with higher precision. In fact, amorphous metals have the following special characteristics: within a given temperature range [ Tg-Tx ] specific to each alloy, amorphous metals can soften but remain amorphous for a period of time (Tx: crystallization temperature, Tg: glass transition temperature). They can therefore be shaped at lower compressive stresses and at considerably lower temperatures, thus allowing the use of processes that are more simplified than machining and drawing operations. In the case of shaping by moulding, the use of such materials additionally enables extremely small geometries to be repeatedly produced with high precision, since the viscosity of the alloy drops sharply as a function of temperature in the temperature range [ Tg-Tx ] and the alloy therefore adapts to all details of the cavity (n gatif). It should be understood that a cavity refers to a mold having a profile in the cavity that is complementary to the profile of the desired component. This thus makes it easy to form complex designs in a precise manner.

Advantageous embodiments of the escapement system are subject matter of the dependent claims.

In a first advantageous embodiment, the anchor pallet is made of a metal alloy that is at least partially amorphous.

In a variant of the first advantageous embodiment, only a portion of the anchor, for example the fork, is made of a metal alloy that is at least partially amorphous.

In a second advantageous embodiment, the pallet stones of the anchor pallet are made of a metal alloy that is at least partially amorphous.

In a third advantageous embodiment, the pallet stone of the anchor and the anchor form one and the same piece.

In another advantageous embodiment, the escape wheel is made of a metal alloy that is at least partially amorphous.

In a further advantageous embodiment, the disc is made of an at least partially amorphous metal alloy.

In another advantageous embodiment, at least one part of the escapement system comprises a recess in order to reduce the moment of inertia of this part.

In a further advantageous embodiment, the groove is through-penetrating.

In another advantageous embodiment, at least one portion of the escapement system comprises a narrowing region in order to reduce the moment of inertia of this portion.

In another advantageous embodiment, the anchor, the escape wheel and the pallet are made of a metal alloy that is at least partially amorphous.

In another advantageous embodiment, the material is completely amorphous.

In another advantageous embodiment, the material is a pure metal.

In another advantageous embodiment, the metal alloy is non-magnetic.

Drawings

The objects, advantages and features of the escapement system according to the invention can be more clearly seen from the following detailed description of at least one embodiment of the invention, given purely by way of non-limiting example, illustrated in the accompanying drawings, in which:

fig. 1 and 2 schematically show an escapement system for a timepiece according to the invention.

Detailed Description

Fig. 1 and 2 show an escapement system 1 with a resonator 3, i.e. a balance spring. In general, resonator 3 cooperates with escapement system 1 with the aid of a roller 5 mounted on the balance axis. Escapement system 1 comprises a swiss anchor pallet 7 formed by a projecting main face (see fig. 1). The swiss anchor pallet 7 is mainly formed by a rod 9 connecting a fork 11 and an arm 13. The fork 11 comprises two horns (horns) 15 facing each other, below which horns 15 there are mounted fork pins 17, which fork pins 17 cooperate respectively with a pin fixed to the roller 5 of the balance wheel axis and with the bottom of the roller 5.

Between the two arms 13, the lever 9 receives an arbour 19, the arbour 19 being used to rotatably mount the anchor pallet between the bridge and the bottom plate of the movement. Finally, pallet stones 21 are fitted on the respective arms 13, the pallet stones 21 being intended to come into contact with the escape wheel 23 through the teeth 25 of the escape wheel 23. As an example, the pallet stone may be formed of an artificial ruby. Of course, the invention can also be used for coaxial escapements, for example in the watchmaking industry.

According to the invention, at least one component of escapement system 1, i.e. disk 5 or anchor 7 or escape wheel 23, is preferably made of a metal alloy that is at least partially amorphous. The metal alloy may comprise a noble metal element, such as gold, platinum, palladium, rhenium, ruthenium, rhodium, silver, iridium or osmium. An at least partially amorphous metal alloy is understood to mean that the material is capable of at least partially solidifying into an amorphous phase.

Of course, it should be understood that, in a particular configuration, all the components of escapement system 1 are made of a metal alloy that is at least partially amorphous. However, these components may be made of different amorphous materials. Further, the metal alloy or metal may be completely amorphous.

It is also conceivable that only a part of the anchor 7, for example the fork 11, is made of an at least partially amorphous metal alloy.

Furthermore, it is envisaged that this at least partially amorphous metal alloy is non-magnetic, so that the escapement system 1 is not sensitive to external magnetic disturbances.

The advantages of amorphous metal alloys stem from the fact that: during their formation, the atoms forming these amorphous materials do not align in a particular structure as do crystalline materials. Therefore, even if the young's modulus E of the crystalline material and the young's modulus of the amorphous metal are substantially the same, their elastic limits are different. The amorphous metal is therefore characterized by: its elastic limit sigma_eAElastic limit sigma of specific crystalline metals_eCThe height is substantially twice as high. Therefore, a higher elastic limit σ_eMeaning that a part made of an amorphous metal alloy or an amorphous metal plastically deforms under higher stress than the same part made of a crystalline metal.

In the driving phase, the energy loss of escapement system 1 is related to the friction between pallet stones 21 of anchor 7 and teeth 25 of escape wheel 23; in the fall phase, its energy loss is associated with the impact between the pin and the fork of the plate 5 and between the tooth 25 of the escape wheel 23 and the pallet stone 21 of the anchor 7.

The energy loss associated with the impact between the tooth 25 of the escape wheel 23 and the pallet stone 21 of the anchor 7 during the fall phase depends on the kinetic energy. The kinetic energy accumulated during operation of escapement system 1 depends on the moment of inertia. The moment of inertia is a function of mass and radius of gyration. In the case of an escape wheel, the larger the diameter or the larger the mass of escape wheel 23, the greater will be the increase in the moment of inertia of said wheel 23. The increase in the moment of inertia causes an increase in the kinetic energy of the escape wheel 23. Thus, when an impact is generated between the tooth 25 of the escape wheel 23 and the pallet stone 21 of the anchor 7 in the falling phase, the kinetic energy accumulated is lost, rather than being transmitted. Therefore, reducing the kinetic energy of the wheel 23 is a solution to reduce these energy losses. Thus, reducing the mass or diameter of the escape wheel 23 results in a reduction of the moment of inertia and, consequently, of the kinetic energy of the escape wheel 23.

An important feature of the material used to make such parts is therefore to maximize the specific strength, defined as the ratio of the elastic limit to the density. In the case of crystalline alloys, the maximum specific strength is about 200-³(ii) in terms of/g. In contrast, the specific strength of the amorphous alloy is about 300-400MPa cm³/g。

Thus, for a given part geometry and a given necessary mechanical strength, amorphous alloys with lower densities than crystalline alloys meeting the same criteria can be used. Thus, the moment of inertia of the system is reduced and its operation is improved.

Another solution is to reduce the mass of the part by removing material, preferably in the area that contributes most to the moment of inertia, i.e. in the part that is the furthest away from the axis of rotation of the part. For example, the groove 29, whether through or not, may be formed and/or the thickness 27 of the part may be locally reduced. Amorphous alloys having higher mechanical strength than crystalline alloys are selected to compensate for this reduction in material. Due to the favorable specific strength of the amorphous alloy, the density of the amorphous alloy may be chosen to be equal to or even slightly less than the density of the crystalline alloy and thus reduce the moment of inertia of the system 1.

A third possibility is to reduce the size of the elements of escapement system 1, such as anchor 7 or escape wheel 23 or pallet 5. By choosing an amorphous alloy with a higher mechanical strength than the crystalline alloy used for the current size, the reduction in size and mass does not cause a reduction in the mechanical strength of escapement system 1. However, since amorphous alloys have a higher specific strength than crystalline alloys, the density of the selected amorphous alloy may be equal to or less than the density of the crystalline alloy used for the standard part, and thus may reduce the moment of inertia and space requirements of the system 1.

It is preferable to choose to reduce the mass of the components of escapement system 1 made of amorphous metal or amorphous metal alloy. This makes it possible to maintain the same space requirements as escapement system 1 made of crystalline material and, consequently, to maintain standard dimensions while having better stress resistance.

To form such an escapement system made of amorphous metal, it is advantageous to shape it using the properties of amorphous metal. In fact, amorphous metals allow extremely easy shaping, enabling parts with complex shapes to be manufactured with greater precision. This is because of the special characteristics of amorphous metals: in a given temperature range [ Tg-Tx ] specific to each alloy](for example, for Zr)_41.24Ti_13.75Cu_12.5Ni₁₀Be_22.5Alloys in which the amorphous metal can soften but remain amorphous for a period of time with a Tg of 350 c and Tx of 460 c. They can therefore be shaped with lower stress at moderate temperatures, allowing the use of simple processes, such as thermoforming. In addition, the temperature range [ Tg-Tx ] is within]The viscosity of the inner alloy drops sharply as a function of temperature and the alloy therefore adapts to all the details of the cavity, so the use of such a material enables extremely small geometries to be repeatedly manufactured with high precision. For example, for platinum-based materials, the forming occurs at about 300 ℃, at which temperature the viscosity reaches 10³Pa.s, stress of 1MPa, not viscosity at temperature Tg of 10¹²Pa · s. The use of dies has the advantage of producing three-dimensional high-precision parts, cutting or stamping not allowing the production of three-dimensional high-precision parts.

The process used is the thermoforming of amorphous preforms. The preform is obtained by melting the metallic elements used to form the amorphous alloy in a furnace. Once these elements have melted, they are cast in the form of a semifinished product and then rapidly cooled so as to maintain an at least partially amorphous state. Once the preform is made, thermoforming is carried out in order to obtain the final part. The above thermoforming is carried out by pressing in a temperature range between its glass transition temperature Tg and its crystallization temperature Tx for a predetermined time to maintain a completely or partially amorphous structure. This is done to preserve the elastic performance characteristics of the amorphous metal.

Typically, for alloy Zr_41.2Ti_13.8Cu_12.5Ni₁₀Be_22.5And a temperature of 440 c, the pressing time should not exceed 120 seconds. Thus, thermoforming allows to maintain the initial state of the preform in an at least partially amorphous state. The various steps of the final shaping of the elements of the escapement are therefore:

a) the mould with cavities of the elements of escapement system 1 is heated to a selected temperature,

b) the amorphous metal preform is inserted between hot dies,

c) applying a closing force to the mold to replicate the mold geometry on the amorphous metal preform,

d) waiting for the maximum time to be selected,

e) the mould is opened and the mould is opened,

f) rapidly cooling the elements of the escapement system below Tg so that the material retains its at least partially amorphous state, an

g) The elements of escapement system 1 are removed from the mold.

Therefore, features of easy forming, high precision of the obtained parts and very good reproducibility of repetition are very useful for obtaining variable thicknesses and grooves. The ease of moulding also allows complex parts to be easily formed, such as the disks 5 with pins of the escapement system 1.

Furthermore, the possibility of easy shaping of complex parts allows, inter alia, complex designs to be produced. This can also be used for the shaping of the teeth of the escape wheel and the shaping of the anchor in order to improve the cooperation between the escape wheel and the anchor.

It will be understood that various alterations and/or modifications and/or combinations obvious to those skilled in the art may be made to the various embodiments of the invention discussed above without departing from the scope of the invention as defined by the appended claims.

Of course, it should be understood that the elements of the escapement system can be formed by casting or injection. The process consists in casting an alloy obtained by melting a metallic element in a mould having the shape of the final part. Once the mould has been filled, it is rapidly cooled to a temperature below Tg to prevent the alloy from crystallizing and thus obtain a system 1 made of amorphous or partially amorphous metal.

Of course, it is also possible to envisage that the pallet stones 21 of the anchor pallet 7 are made of amorphous metal or amorphous alloy. These pallet stones 21 can be made integral with said anchor, or moulded on the anchor 7 after it has been made. Therefore, it is conceivable that the pallet stone 21 and the anchor pallet 7 are made of amorphous metals or amorphous alloys different from each other.

Claims (17)

1. Escapement system comprising an anchor (7), the anchor (7) being equipped with a fork (11) and a lever (9), the fork (11) being intended to cooperate with a pin mounted on a pallet (5), the lever (9) comprising an arm (13) intended to receive a pallet stone (21) so as to cooperate with at least one escapement wheel (23), characterized in that at least one portion of said escapement system is made of a metal alloy that is at least partially amorphous, said metal alloy being at least partially amorphous having a young's modulus equal to that of a crystalline metal and having an elastic limit that is two times higher than that of the crystalline metal.

2. Escapement system according to claim 1, characterized in that the anchor (7) is made of a metal alloy that is at least partially amorphous.

3. Escapement system according to claim 1, characterized in that the pallet stones (21) of the anchor (7) are made of a metal alloy that is at least partially amorphous.

4. Escapement system according to claim 2, characterized in that the pallet stones (21) of the anchor (7) are made of a metal alloy that is at least partially amorphous.

5. Escapement system according to claim 1, characterized in that the pallet stone (21) of the anchor (7) and the anchor (7) form one and the same piece.

6. Escapement system according to claim 2, characterized in that the pallet stone (21) of the anchor (7) and the anchor (7) form one and the same piece.

7. Escapement system according to claim 3, characterized in that the pallet stone (21) of the anchor (7) and the anchor (7) form one and the same piece.

8. Escapement system according to claim 4, characterized in that the pallet stone (21) of the anchor (7) and the anchor (7) form one and the same piece.

9. Escapement system according to claim 1, characterized in that the escape wheel (23) is made of a metal alloy that is at least partially amorphous.

10. Escapement system according to claim 1, characterized in that the puck (5) is made of a metal alloy that is at least partially amorphous.

11. Escapement system according to claim 1, characterized in that at least one part of the escapement system comprises a recess (29) in order to reduce the moment of inertia of this part.

12. Escapement system according to claim 11, characterized in that the groove is through-going.

13. Escapement system according to claim 1, characterized in that at least one part of the escapement system comprises a narrowing region (27) in order to reduce the moment of inertia of this part.

14. Escapement system according to claim 1, characterized in that the anchor (7), the escape wheel (23) and the pallet (5) are made of a metal alloy that is at least partially amorphous.

15. The escapement system of claim 1, wherein the metal alloy is fully amorphous.

16. The escapement system of claim 1, wherein the metal is a pure metal.

17. The escapement system of claim 1, wherein the metal alloy is nonmagnetic.