WATCH SERIES AND ITS MANUFACTURING METHOD

Description

Field of invention

[0001] The invention relates to a watch assembly comprising two components, in particular a balance wheel and a screw, assembled under stress. It also relates to its manufacturing method. Background of the invention

[0002] Many embodiments of balances with inertia adjustment and / or balancing means are known. In particular, balances with weights, also called screw-type weights, are known, screwed or driven into locations in the rim of a balance. Some embodiments have attempted to ensure the retention of screw-type weights by pinching. Thus, document CH 705 238 is known, which discloses a balance comprising at least one slot for receiving and pinching in position a rod of a screw-type weight, the slot being delimited by, on the one hand, a rigid part of the balance, and on the other hand, an elastic arm permanently biased towards said rigid part of the balance delimiting the slot to retain the screw-type weight. When the screw-type weights are inserted, the elastic arm undergoes significant deformations following its separation. These deformations can then generate defects in the material, such as cracks or the beginnings of cracks.They can also cause defects in the protective layer covering the balance wheel. This layer is designed to give the balance wheels a particular appearance and improve their resistance to tarnishing and corrosion. The layer is usually gold plating with a nickel undercoat to combine aesthetics and corrosion resistance properties. The assembly of the weights on the balance wheel will cause defects in this protective layer in the areas subjected to stress during deformation of the arm as well as in the support or gripping areas where the layer may be locally damaged. The protective layer is then no longer impervious to aggressive agents such as ammonia or chlorine, which can cause stress corrosion of the underlying material.

[0003] A similar assembly, between a balance wheel and a screw, is described in document CH703462A2. Aims of the invention

[0004] The present invention is defined in the set of attached method claims and its object is to overcome the aforementioned drawbacks by proposing a method for manufacturing a watch assembly comprising two components assembled under stress such as the balance / screw couple, including a step of depositing a protective layer subsequent to the step of assembling the two components.

[0005] This layer can consist essentially of SiO 2 , Al 2 O 3 , Rh, Au, Ni or NiP or even a stack of several layers of these materials.

[0006] Adding this layer after assembly reinforces the barrier effect of the layer applied before assembly, particularly in areas potentially damaged during assembly. This protective layer applied after assembly ensures that the finished product will not have any surface defects due to assembly. It fills in any potential cracks or crack initiations, preventing contact between the aggressive environment and the underlying material.

[0007] The protective layer has a thickness between 20 nm and 3 µm, preferably between 100 nm and 500 nm. This thin thickness prevents welding of the screw to the balance, which would have an impact on the adjustment functionality of the screws.

[0008] The present invention is also defined in the appended set of device claims and also relates to the timepiece assembly comprising a first component and a second component assembled under stress, with at least a portion of the surface of the timepiece assembly coated with the protective layer intended to cover defects upon completion of the assembly. Summary description of the drawings

[0009] Other features and advantages will become clear from the description given below, for information purposes only and in no way limiting, with reference to the attached drawings. There figure 1 is a plan view of the watch assembly according to the invention comprising the balance wheel and two screw-heads. The figure 2 is a three-dimensional view of the screw of the watch assembly according to the figure 1 . There figure 3is a schematic sectional view of a component of the watch assembly covered with several layers according to the method of the invention. The Figure 4A is an electron microscopy view of a section taken from the balance wheel of the watch assembly according to the invention. The Figure 4B is a schematic representation of the Figure 4A . Description of the invention

[0010] The invention relates to a watch assembly comprising at least two components assembled under stress. For example, as shown in figure 1 , the first component is a balance 2 comprising an elastic arm 2a delimiting a slot 4 receiving during assembly the second component which is a screw 3 also visible in the figure 2 It could also be a driven element such as a pin in a chainring or a balance wheel on an axle.

[0011] The components may be made of a material selected from the list including copper, copper alloys such as brass or nickel silver, aluminum, aluminum alloys, titanium, titanium alloys, carbon steel and ferritic and austenitic stainless steels.

[0012] According to the invention, the watch assembly is covered at least partially with a protective layer after assembly intended to cover any defects such as cracks, incipient cracks, material tearing, resulting from the assembly or possibly already present before assembly. Figures 4A and 4Brepresent respectively using an electron microscopy view and a schematic view of this same view, the formation of cracks 8 in the base material of one of the components (reference 2) as well as in a protective layer, called the first layer 6, deposited before assembly. According to the invention, a protective layer 7, called the second layer, is deposited on the cracked surface to form a barrier impervious to the external environment after assembly.

[0013] There figure 3schematically represents the layers deposited on the watch assembly 1. Before assembly, one or more layers may optionally be deposited on at least one of the two components of the watch assembly. The base material of the watch assembly may thus be coated with a first layer 6 and always optionally with a sub-layer 5 below the first layer 6. The first layer 6 may comprise rhodium or pure gold or comprising traces of elements such as cobalt or nickel and the sub-layer 5 may comprise nickel such as NiP or pure galvanic Ni, or pure gold or with traces of elements. The first layer has a thickness of between 100 nm and 2 µm and the sub-layer has a thickness of between 100 nm and 2 µm.

[0014] The protective layer 7 which is more particularly the subject of the invention is a barrier layer deposited after assembly. This layer is formed of a single layer or a stack of layers. Each layer respectively comprises SiO 2 , Al 2 O 3 , Rh, Au, Ni or NiP with low (2-4% by weight), medium (5-9% by weight) or high P (10-13% by weight). Preferably, each layer is respectively made of SiO 2 , Al 2 O 3 , Rh, Au, Ni or NiP with low (2-4% by weight), medium (5-9% by weight) or high P (10-13% by weight). The protective layer has a thickness of between 20 nm and 3 µm, preferably between 100 nm and 500 nm. For the variant with a stack of layers, the set of layers has a thickness between 20 nm and 3 µm, preferably between 100 nm and 500 nm.

[0015] According to the invention, at least a portion of the surface of the assembly is coated with the protective layer intended to cover the defects following assembly. Advantageously, at least the surface of the component subjected to deformation during assembly is coated. Preferably, the entire exterior surface of the watch assembly is coated with the protective layer.

[0016] The protective layer 7 deposited after assembly is thus free from defects and more particularly from cracks and the beginnings of cracks.

[0017] The present invention also relates to the method of manufacturing the watch assembly comprising the following steps: a) Provision of the first component and the second component, b) Assembly under stress of the first component and the second component, c) Deposition of the protective layer 7, also called second layer, on at least part of the surface of the assembly comprising the first component and the second component.

[0018] According to the invention, the protective layer is deposited by ALD (for Atomic Layer Deposition in English), PVD (for Physical Vapor Deposition in English), CVD (for Chemical Vapor Deposition in English), chemical or galvanic deposition.

[0019] The method may further comprise a step a') of depositing the first layer 6 on at least part of the first component and / or the second component before the assembly step b).

[0020] The method may also comprise a step a") of depositing the sub-layer 5 on said at least part of the first component and / or the second component before step a').

[0021] The undercoat and first layer can also be deposited by ALD, PVD, CVD, chemical or galvanic deposition.

[0022] The method may also comprise a step a) of heat treatment intended to improve the adhesion of the first layer and the underlayer if the latter are present. This step takes place before step b) of assembly. The heat treatment is carried out between 150 and 300°C for 30 minutes to 5 hours. Alternatively, the method comprises a step d) of this same heat treatment after step c) of depositing the protective layer. According to another variant, the method comprises a step a) of this heat treatment before step b) of assembly and a step d) of this heat treatment after step c) of depositing the protective layer. Legend

[0023] (1) Watch assembly (2) Balance a. Elastic arm (3) Screw a. Stem (4) Slot (5) Undercoat deposited before assembly (6) Layer deposited before assembly, also called first layer (7) Layer deposited after assembly, also called protective layer or second layer (8) Crack or crack initiation (9) Sample embedding material viewed by electron microscopy

Claims

1. Method for manufacturing a timepiece assembly (1) comprising a first component and a second component assembled under mechanical stress, wherein the first component is a balance (2) comprising a resilient arm (2a) delimiting a slot (4) intended to receive the second component which is an inertia screw (3), said method including the following successive steps: a) providing a balance and an inertia screw, b) assembling the inertia screw to the balance under mechanical stress by resilient deformation of the resilient arm and insertion of the inertia screw into the slot, c) depositing a protective layer (7), also referred to as the second layer, on at least one part of the surface of the inertia screw / balance assembly.

2. Method according to claim 1, characterised in that it includes a step a') of depositing a first layer (6) on at least one part of the first component and / or of the second component before assembly step b).

3. Method according to the preceding claim, characterised in that it includes a step a") of depositing a sublayer (5) on said at least one part of the first component and / or of the second component before step a').

4. Method according to claim 2 or 3, characterised in that it includes a heat treatment step a‴) after step a') and before assembly step b), said step a‴) being carried out at between 150 and 300°C for between 30 minutes and 5 hours.

5. Method according to one of the preceding claims, characterised in that it includes a heat treatment step d) after step c), said step d) being carried out at between 150 and 300°C for between 30 minutes and 5 hours.

6. Method according to one of the preceding claims, characterised in that the protective layer (7) is deposited by ALD, PVD, CVD, chemical deposition or galvanic deposition.

7. Method according to claim 3, characterised in that the first layer (6) and the sublayer (5) are deposited by ALD, PVD, CVD, chemical deposition or galvanic deposition.

8. Timepiece assembly (1) comprising a first component and a second component, wherein the first component is a balance (2) comprising a resilient arm (2a) delimiting a slot (4) in which the second component, which is an inertia screw (3) is arranged and held in the slot by mechanical stress, characterised in that the timepiece assembly (1) is coated with a protective layer (7) over at least one part of the surface of the inertia screw / balance assembly comprising the first component and the second component.

9. Timepiece assembly (1) according to claim 8, characterised in that the entire surface of the timepiece assembly (1) is coated with the protective layer (7).

10. Timepiece assembly (1) according to one of claims 8 or 9, characterised in that the protective layer (7) is free of cracks and incipient cracks (8).

11. Timepiece assembly (1) according to one of claims 8 to 10, comprising a first layer (6) on at least one part of the first component and / or of the second component, said first layer (6) being arranged below the protective layer (7).

12. Timepiece assembly (1) according to the preceding claim, comprising a sublayer (5) arranged under the first layer (6).

13. Method for manufacturing a timepiece assembly (1) comprising a first component and a second component assembled under mechanical stress, wherein the first component is an element assembled by being driven onto the second component, and wherein the first component is an impulse pin and the second component is a roller, or wherein the first component is a balance and the second component is a staff, said method including the following successive steps: d) providing the first and second components, e) assembling the first and second components under stress, f) depositing a protective layer (7), also referred to as the second layer, on at least one part of the surface of the assembly comprising the first component and the second component.

14. Method according to one of claims 1 to 7 or according to claim 13, or timepiece assembly (1) according to one of claims 8 to 12, characterised in that the protective layer (7) includes SiO2, Al2O3, Rh, Au, Ni or NiP.

15. Method according to one of claims 1 to 7 or according to claim 13, or timepiece assembly (1) according to one of claims 8 to 12, characterised in that the protective layer (7) is formed from a stack of layers including respectively SiO2, Al2O3, Rh, Au, Ni or NiP.

16. Method according to one of claims 1 to 7 or according to claim 13, or timepiece assembly (1) according to one of claims 8 to 12, characterised in that the protective layer (7) has a thickness of between 20 nm and 3 µm, preferably between 100 nm and 500 nm.

17. Method according to one of claims 2 to 7, or timepiece assembly (1) according to one of claims 11 to 12, characterised in that the first layer (6) includes Au or Rh.

18. Method according to one of claims 2 to 7, or timepiece assembly (1) according to one of claims 11 to 12, characterised in that the first layer (6) has a thickness of between 100 nm and 2 µm.

19. Method according to one of claims 3 to 7, or timepiece assembly (1) according to claim 12, characterised in that the sublayer (5) includes Ni or Au.

20. Method according to one of claims 3 to 7, or timepiece assembly (1) according to claim 12, characterised in that the sublayer (5) has a thickness of between 100 nm and 2 µm.

21. Timepiece assembly (1) comprising a first component and a second component, wherein the first component is an element which is assembled by being driven onto the second component, and wherein the first component is an impulse pin and the second component is a roller, or wherein the first component is a balance and the second component is a staff, characterised in that the timepiece assembly (1) is coated with a protective layer (7) over at least one part of the surface of the assembly of assembled components comprising the first component and the second component.