TIMEPIECE ASSEMBLY AND METHOD FOR MANUFACTURING THE SAME

Abstract

A timepiece assembly including a first component and a second component assembled under stress, wherein at least one part of the surface of the assembly is coated with a protective layer intended to cover defects such as cracks or incipient cracks after assembly. It also relates to the method for manufacturing this assembly.

Claims

1. A method for manufacturing a timepiece assembly comprising a first component and a second component assembled under mechanical stress wherein the first component is a balance comprising a resilient arm delimiting a slot intended to receive the second component which is an inertia screw, 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 elastic deformation of the resilient arm and insertion of the inertia screw into the slot, c) depositing a protective layer, also called the second layer, on at least one part of the surface of the inertia screw/second component assembly.

2. The method according to claim 1, wherein the method comprises a step a′) of depositing a first layer on at least one part of the first component and/or of the second component prior to assembly step b).

3. The method according to claim 1, wherein the method comprises a step a″) of depositing a sublayer on said at least one part of the first component and/or of the second component prior to step a′).

4. The method according to claim 2, wherein the method comprises a heat treatment step a′″) after step a′) and before assembly step b), said step a′″) being carried out between 150 and 300° C. for a time comprised between 30 minutes and 5 hours.

5. The method according to claim 1, wherein the method comprises a heat treatment step d) after step c), said step d) being carried out between 150 and 300° C. for a time comprised between 30 minutes and 5 hours.

6. The method according to claim 5, wherein the protective layer is deposited by ALD, PVD, CVD, chemical deposition or electroplating deposition.

7. The method according to claim 3, wherein the first layer and the sublayer are deposited by ALD, PVD, CVD, chemical deposition or electroplating deposition.

8. A timepiece assembly comprising a first component and a second component wherein the first component is a balance comprising a resilient arm delimiting a slot wherein the second component, which is an inertia screw, is arranged and retained in the slot by mechanical stress, wherein the timepiece assembly is coated with a protective layer on at least one part of the surface of the inertia screw/balance assembly.

9. The timepiece assembly according to claim 8, wherein the entire surface of the timepiece assembly is coated with the protective layer.

10. The timepiece assembly according to claim 8, wherein the protective layer is devoid of cracks and incipient cracks.

11. The timepiece assembly according to claim 8, comprising a first layer on at least one part of the first component and/or of the second component, said first layer being arranged underneath the protective layer.

12. The timepiece assembly according to claim 11, comprising a sublayer arranged underneath the first layer.

13. A method for manufacturing a timepiece assembly comprising a first component and a second component assembled under mechanical stress wherein the first component is an element assembled by press fit 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 shaft, said method comprising the following successive steps: d) providing the first component and the second component, e) assembling the first component and the second component under stress, f) depositing a protective layer, also called the second layer, on at least one part of the surface of the assembly comprising the first component and the second component.

14. The method according to claim 1, wherein the protective layer comprises SiO.sub.2, Al.sub.2O.sub.3, Rh, Au, Ni or NiP.

15. The method according to claim 1, wherein the protective layer is formed of a stack of layers respectively comprising SiO.sub.2, Al.sub.2O.sub.3, Rh, Au, Ni or NiP.

16. The method according to claim 1, wherein the protective layer has a thickness comprised between 20 nm and 3 μm.

17. The method according to claim 2, wherein the first layer comprises Au or Rh.

18. The method according to claim 2, wherein the first layer has a thickness comprised between 100 nm and 2 μm.

19. The method according to claim 3, wherein the sublayer comprises Ni or Au.

20. The method according to claim 3, wherein the sub-layer has a thickness comprised between 100 nm and 2 μm.

21. A timepiece assembly comprising a first component and a second component wherein the first component is an element assembled by press fit 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 shaft, wherein the timepiece assembly is coated with a protective layer on at least one part of the surface of the assembly of the assembled components.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Other features and advantages will appear clearly from the following description, given by way of non-limiting illustration, with reference to the annexed drawings.

[0009] FIG. 1 is a plan view of the timepiece assembly according to the invention comprising the balance and two inertia screws.

[0010] FIG. 2 is a three-dimensional view of the inertia screw of the timepiece assembly of FIG. 1.

[0011] FIG. 3 is a schematic cross-sectional view of a component of the timepiece assembly coated with several layers according to the method of the invention.

[0012] FIG. 4A is an electron microscope view of a cross-section of the balance of the timepiece assembly according to the invention.

[0013] FIG. 4B is a schematic diagram of FIG. 4A.

DESCRIPTION OF THE INVENTION

[0014] The invention relates to a timepiece assembly comprising at least two components assembled under stress. By way of example, as represented in FIG. 1, the first component is a balance 2 comprising a resilient arm 2a delimiting a slot 4 which, during assembly, receives the second component which is an inertia screw 3 also visible in FIG. 2. This could also be a pressed-in element, like an impulse pin in a roller or a balance on a staff, etc.

[0015] The components can be made of a material chosen from the list including copper, copper alloys such as brass or nickel silver, aluminium, aluminium alloys, titanium, titanium alloys, carbon steel and ferritic and austenitic stainless steels.

[0016] According to the invention, the timepiece assembly is at least partially coated with a protective layer after assembly, intended to cover any defects such as cracks, incipient cracks, peeling, resulting from the assembly process or possibly already present prior to assembly. FIGS. 4A and 4B respectively represent, in an electron microscope view and a schematic view of said electron microscope view, the formation of cracks 8 in the base material of one of the components (referenced 2) and in a protective layer, called first layer 6, deposited prior to assembly. According to the invention, a protective layer 7, called the second layer, is deposited on the cracked surface to form a barrier impermeable to the external environment after assembly.

[0017] FIG. 3 schematically represents the layers deposited on timepiece assembly 1. Prior to assembly, one or more layers can optionally be deposited on at least one of the two components of the timepiece assembly. The base material of the timepiece assembly can thus be coated with a first layer 6 and, also optionally, with a sublayer 5 underneath first layer 6. First layer 6 may comprise rhodium or pure gold or gold comprising traces of elements such as cobalt or nickel, and sublayer 5 can comprise nickel, such as NiP or pure electroplated Ni, or pure gold or gold with trace elements. The first layer has a thickness comprised between 100 nm and 2 μm, and the sublayer has a thickness comprised between 100 nm and 2 μm.

[0018] 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 of a stack of layers. Each layer respectively comprises SiO.sub.2, Al.sub.2O.sub.3, Rh, Au, Ni or NiP with low P (2-4% by weight), medium P (5-9% by weight) or high P (10-13% weight). Preferably, each layer respectively consists of SiO.sub.2, Al.sub.2O.sub.3, Rh, Au, Ni or NiP with low P (2-4% by weight), medium P (5-9% by weight) or high P (10-13% weight). The protective layer has a thickness comprised between 20 nm and 3 μm, and preferably between 100 nm and 500 nm. For the variant with a stack of layers, all the layers have a thickness comprised between 20 nm and 3 μm, preferably between 100 nm and 500 nm.

[0019] According to the invention, at least one part of the surface of the assembly is coated with the protective layer intended to cover defects at the end of the assembly process. Advantageously, at least the surface of the component subjected to deformation during assembly is coated. Preferably, the entire external surface of the timepiece assembly is coated with the protective layer.

[0020] Protective layer 7 deposited after assembly is thus devoid of defects and more particularly of cracks and incipient cracks.

[0021] The present invention also relates to the method of manufacturing the timepiece assembly including the following steps:

a) Providing the first component and the second component,
b) Assembling the first component and the second component under stress,
c) Depositing protective layer 7, also called the second layer, on at least one part of the surface of the assembly comprising the first component and the second component.

[0022] According to the invention, the protective layer is deposited by ALD (Atomic Layer Deposition), PVD (Physical Vapour Deposition), CVD (Chemical Vapour Deposition), chemical or electroplating deposition.

[0023] The method may also comprise a step a′) of depositing first layer 6 on at least one part of the first component and/or of the second component prior to assembly step b).

[0024] The method may also include a step a″) of depositing sublayer 5 on said at least one part of the first component and/or of the second component prior to step a′).

[0025] The sublayer and the first layer can also be deposited by ALD, PVD, CVD, chemical or electroplating deposition.

[0026] The method may also include a heat treatment step a′″) intended to improve the adherence of the first layer and the sublayer if these latter are present. This step occurs prior to assembly step b). The heat treatment is carried out between 150 and 300° C. for 30 minutes to 5 hours. In a variant, the method includes a step d) of this same heat treatment after step c) of depositing the protective layer. According to another variant, the method includes a step a′″) of this heat treatment prior to assembly step b) and a step d) of this heat treatment after step c) of depositing the protective layer.

KEY

[0027] (1) Timepiece assembly [0028] (2) Balance [0029] a. Resilient arm [0030] (3) Inertia screw [0031] a. Shaft [0032] (4) Slot [0033] (5) Sublayer deposited prior to assembly [0034] (6) Layer deposited prior to assembly, also called the first layer [0035] (7) Layer deposited after assembly, also called the protective layer or second layer [0036] (8) Crack or incipient crack [0037] (9) Coating material of the sample seen in an electron microscope view