METHOD FOR MANUFACTURING A CLOCK DRIVE SPRING AND CLOCK DRIVE SPRING OBTAINED BY THIS METHOD

Description

Technical field of the invention

[0001] The invention belongs to the field of micromechanical components, and more specifically to that of watch movements, in particular escapement mechanisms comprising at least one escape wheel and at least one anchor, of which at least one is non-magnetic.

[0002] The invention relates in particular to a method for manufacturing a micromechanical component, in particular a watch movement. Technological background

[0003] State-of-the-art anchor escapement mechanisms in watches generally include escape wheels made of nickel-plated steel. These escape wheels are sensitive to magnetic fields.

[0004] To resolve the drawbacks resulting from this sensitivity to magnetic fields, escape wheels have been developed with materials having an amagnetic behavior, such as nickel-phosphorus (NiP12) implemented in particular by the so-called "LIGA" process (from the German "Röntgenlithographie, Galvanoformung, Abformung" meaning in French "lithography, galvanization, forming").

[0005] However, the use of such materials can prove sensitive under certain climatic conditions, as they are likely to lead to a degradation of performance, particularly in terms of amplitude regularity, stops, or even aging.

[0006] This performance degradation is all the more significant when two opposing components cooperating with each other to produce a frictional torque are made of similar LIGA materials.

[0007] In particular, it is essential to prevent any contamination of the anchor, especially the anchor fork, and to ensure the presence of lubricant on the contact surfaces of the escape wheel and the anchor, in particular the contact between the ruby ​​lever of the anchor and the tooth of the escape wheel, in order to limit the aging of the escape wheel and the anchor.

[0008] The main problem is the loss of epilame effect on the exhaust wheel board, which causes oil to spread and loss of lubrication at the contact between the wheel tooth and the ruby ​​lift.

[0009] The stability of the lubrication at the contact between the anchor levers and the escape wheel must ensure the consistency of the amplitude.

[0010] Document CH698230 deals with the problem of friction of moving parts in a watch movement, but does not address in particular the problems related to magnetism or the sensitivity of materials in certain climatic conditions. Summary of the invention

[0011] The invention aims to solve the technical problem of the holding of the usual watch lubricant, and more particularly to guarantee an epilame effect, in all climatic conditions, on components made of LIGA NiP12, or similar, non-ferromagnetic, in particular on anchors and Swiss lever escape wheels.

[0012] To this end, the invention relates to a method for manufacturing a watch movement, comprising the successive steps of: deposition of a first thin layer with a first material comprising at least nickel, in a geometric shape whose periphery defines the contour of the geometry of the clockwork mechanism, deposition of an intermediate layer, with a second material comprising at least nickel and phosphorus, so as to cover a face of the first thin layer and so as to present a geometric shape whose periphery corresponds to that of the geometric shape of the first thin layer, deposition of a second thin layer with the first material, so as to cover a face of the intermediate layer and so as to present a geometric shape whose periphery corresponds to that of the geometric shape of the first thin layer.

[0013] The first and second thin layers are poorer in phosphorus than the intermediate layer, or are devoid of phosphorus.

[0014] In particular embodiments, the invention may further comprise one or more of the following features, taken individually or in all technically possible combinations.

[0015] In particular modes of implementation, the intermediate layer is superimposed on the first thin layer and the second thin layer is superimposed on the intermediate layer, respectively at the level of at least one interface face contiguous to at least one friction face of the watch movement intended to be in contact with another watch component.

[0016] In specific implementation modes, the deposition steps of the first thin layer, the intermediate layer and the second thin layer are implemented by LIGA.

[0017] In specific implementation methods, the second material consists solely of nickel and phosphorus.

[0018] In specific implementation methods, the second material has a proportion by mass of phosphorus between 1% and 15%.

[0019] In specific implementation methods, the second material is made of NiP12.

[0020] In specific implementation methods, the first material consists solely of pure nickel, or solely of nickel and phosphorus.

[0021] In specific implementation methods, the first material comprises a proportion by mass of phosphorus less than or equal to 9%.

[0022] In specific implementation methods, the first material comprises a proportion by mass of phosphorus between 6% and 9%.

[0023] In specific implementation methods, the first material comprises a proportion by mass of phosphorus between 1% and 6%.

[0024] In specific implementation methods, the first material comprises a proportion by mass of phosphorus between 0% and 1%.

[0025] In specific implementation methods, the first material includes boron.

[0026] Boron allows the first and second layers to exhibit better tribological and hardness properties.

[0027] In specific implementation methods, the first material consists solely of nickel and boron.

[0028] In specific implementation methods, the first material has a thickness between 0.2 micrometers and 10 micrometers.

[0029] In specific implementation methods, a heat treatment is applied to an assembly consisting of the first thin layer, the intermediate layer and the second thin layer, at a temperature between 100°C and 500°C, for 1 to 8 hours.

[0030] In specific implementation methods, the process is applied to the manufacture of an escapement mechanism, which is an escape wheel or an anchor.

[0031] In particular modes of implementation, the first thin layer, the intermediate layer and the second thin layer are deposited so that the resulting clockwork mechanism has, in the sense and direction of growth of deposition of said layers, a phosphorus concentration gradient defined by a progressive growth through the first thin layer, a stable state through the intermediate layer and a decrease through the second thin layer.

[0032] According to another object, the present invention relates to a clockwork mechanism manufactured by implementing the process described above, and comprising an intermediate layer interposed between a first thin layer and a second thin layer, said thin layers being made of a first material comprising at least nickel, the intermediate layer being made of a second material comprising at least nickel and phosphorus, the first and second thin layers being poorer in phosphorus than the intermediate layer, or being devoid of phosphorus.

[0033] In particular embodiments, the clockwork mechanism constitutes an escape wheel or an anchor. Brief description of the figures

[0034] Other features and advantages of the invention will become apparent from the following detailed description, given by way of non-limiting example, with reference to the accompanying drawings in which: there figure 1 schematically represents a cross-sectional view of a clockwork mechanism obtained by implementing the clockwork mechanism manufacturing process according to the invention; the figure 2 represents a flowchart illustrating the steps in the manufacturing process of a watch movement according to the invention.

[0035] Note that the figures are not to scale. Detailed description of the invention

[0036] The present invention relates in particular to a method for manufacturing a clockwork mechanism 10, the steps of which are represented by the flowchart of the figure 2 .

[0037] The manufacturing process includes the following successive steps: deposition 101 of a first thin layer 11, or of a substrate, with a first material comprising at least nickel, in a geometric shape whose periphery defines the contour of the geometry of the watch movement 10, the thickness of said first thin layer 11 being less than 5 micrometers, deposition 102 of an intermediate layer 12, with a second material comprising at least nickel and phosphorus, so as to cover a face of the first thin layer 11, and so as to present a geometric shape whose periphery corresponds to that of the geometric shape of the first thin layer, deposition 103 of a second thin layer 13 with the first material, so as to cover a face of the intermediate layer 12 and so as to present a geometric shape whose periphery corresponds to that of the geometric shape of the first thin layer 11.

[0038] The thickness of said second thin layer 13 is substantially equal to the thickness of the first thin layer 11, as shown by the clockwork mechanism schematically represented on the figure 1 , the sum of said thicknesses being several times less than that of the intermediate layer 12.

[0039] Preferably, the periphery of the geometric shape of the first thin layer 11 defines the outline of the geometry of an escape wheel or an anchor, so that the clockwork mobile 10 obtained by implementing the process according to the present invention is an escape wheel or an anchor, or even the pallets of an anchor.

[0040] Preferably, the first and second thin layers 11 and 13 and the intermediate layer 12 are deposited according to a LIGA process, according to a predefined deposition growth direction, perpendicular to a plane in which the geometric shape of the first thin layer 11 extends.

[0041] Preferably, the first and second thin layers 11 and 13 and the intermediate layer 12 are configured to exhibit non-magnetic properties.

[0042] It should be noted that the first material and the second material are not necessarily non-magnetic; in this case, it is the thinness of each layer that gives the part its non-magnetic character.

[0043] In one embodiment of the invention, the first and second thin layers 11 and 13 can be made of nickel by electroplating. Alternatively, they can be made of a nickel alloy by electroplating, for example, Ni-Fe, or Ni-W, or other.

[0044] Alternatively, the deposition of the first and second thin layers 11 and 13 can be carried out chemically, according to a chemical nickel application process, for example pure nickel, a phosphorus-poor nickel-phosphorus, for example NiP6-9, with 6% to 9% by mass of phosphorus, with a proportion by mass of phosphorus between 0% and 1% or between 1% and 6%, or even a nickel-boron (NiB).

[0045] The first and second thin layers 11 and 13 are advantageously poorer in phosphorus than the intermediate layer 12, or are devoid of phosphorus.

[0046] Thanks to this feature, the invention makes it possible to increase the stability of the epilame in usual climatic conditions, to increase the grip of the epilame, and therefore the resistance of any usual watch lubricant.

[0047] Thus, the present invention makes it possible to greatly improve the performance of movements.

[0048] Indeed, it has been demonstrated by various tests that these effects on the willowherb are obtained when the amount of phosphorus on the surface is reduced.

[0049] In one embodiment of the invention, the first thin layer 11 and the second thin layer 13 each have a thickness of less than 10 micrometers, and particularly between 0.2 micrometers and 5 micrometers, and preferably between 0.2 micrometers and 2 micrometers.

[0050] In one embodiment of the invention, the intermediate layer 12 is at least 100 micrometers thick.

[0051] In a particular embodiment of the invention, the intermediate layer 12 is made of nickel-phosphorus of NiPx formulation, with x between 1% and 15% by mass, or more particularly with x between 10% and 15% by mass, the latter range making it possible to guarantee the non-magnetic character of the coating.

[0052] Preferably, the intermediate layer 12 is made of NiP12.

[0053] The intermediate layer 12 can consist solely of nickel and phosphorus. Furthermore, it can be produced either electroplated or chemically.

[0054] It is possible to apply a heat treatment to the watch movement 10 formed by all the layers.

[0055] More specifically, the heat treatment may consist of subjecting an assembly formed by the first thin layer 11, the intermediate layer 12, and the second thin layer 13, to a temperature between 100°C and 500°C, for 1 to 8 hours.

[0056] Alternatively or additionally, it is possible to apply a chemical treatment to the surface of the first thin layer 11 and to the surface of the intermediate layer 12 to modify its surface state characteristics in order to facilitate the adhesion of the next layer, i.e. the intermediate layer 12 or the second thin layer 13. This chemical treatment can in particular be carried out by galvanic means.

[0057] The process according to the invention is implemented by LIGA.

[0058] The invention makes it possible to guarantee normal aging conditions for the clockwork mechanism 10, a constant amplitude, and the absence of stopping.

[0059] As shown by figure 1The intermediate layer 12 is superimposed on the first thin layer 11, and the second thin layer 13 is superimposed on the intermediate layer 12, respectively at at least one face, referred to as the "interface face" 14, contiguous to at least one contact face, referred to as the "friction face" 15, of the watch movement 10 intended to be in contact with another movement or watch component. The friction face(s) 15 may also constitute the guiding surfaces of the watch movement 10 for its pivoting or for its guidance along a single degree of freedom.

[0060] In other words, the friction face(s) 15 corresponds to the cross-section of the first and second thin layers 11 and 13 and the intermediate layer 12. Preferably, the clockwork mechanism 10 has several friction faces 15.

[0061] Thus, the friction faces 15 are advantageously made up mostly of the second material insofar as the sum of the thicknesses of the first and second thin layers 11 and 13 is relatively small compared to the thickness of the intermediate layer 12, for example by a factor of at most one tenth.

[0062] This characteristic is advantageous because the friction is carried out on a surface made primarily of nickel-phosphorus, which has good tribological properties.

[0063] The first and second thin layers 11 and 13 also have faces opposite each other constituting end faces 16 of the clockwork mechanism 10.

[0064] Another advantage of the process according to the present invention lies in obtaining a one-piece watch movement, which, compared to possible manufacturing processes of the prior art, makes it possible to do without a step of depositing a coating.

[0065] An example of an embodiment of the invention has been described previously in which the first thin layer 11, the intermediate layer 12 and the second thin layer 13 each have a unique concentration of phosphorus.

[0066] However, it can be envisaged in another embodiment of the invention that the first thin layer 11, the intermediate layer 12 and the second thin layer 13 are deposited so that the clockwork mechanism 10 formed has, in the direction and direction of growth of deposition of said layers, a phosphorus concentration gradient defined for example by a progressive growth through the first thin layer 11, a stable state through the intermediate layer 12 and a progressive decrease through the second thin layer 13.

[0067] The concentration gradient includes the phosphorus concentration values ​​mentioned above in this description.

[0068] As an example, the phosphorus concentration can evolve from a value of zero in the end face 16 of the first thin layer 11 up to a maximum of 12% by mass in the intermediate layer 12, then decrease so as to reach a value of zero in the end face 16 of the second thin layer 13.

Claims

1. Method for manufacturing a horological wheel set (10), which method comprises the successive steps of: - depositing 101 a first thin layer (11) using a first material comprising at least nickel, in a geometric shape whose periphery defines the contour of the geometry of the horological wheel set (10), - depositing 102 an intermediate layer (12) using a second material comprising at least nickel and phosphorus, so as to cover one face of the first thin layer (11) and so as to have a geometric shape whose periphery corresponds to that of the geometric shape of the first thin layer (11), - depositing 103 a second thin layer (13) using the first material, so as to cover one face of the intermediate layer (12) and so as to have a geometric shape whose periphery corresponds to that of the geometric shape of the first thin layer (11), - the first and the second thin layer (11, 13) containing less phosphorus than the intermediate layer (12), or being phosphorus-free.

2. Method according to claim 1, wherein the intermediate layer (12) is superimposed on the first thin layer (11) and wherein the second thin layer (13) is superimposed on the intermediate layer (12), respectively at at least one interface face (14) contiguous with at least one friction face (15) of the horological wheel set (10), which friction face is intended to be in contact with another timepiece component.

3. Method according to claim 2, wherein the steps 101, 102 and 103 of depositing the first thin layer (11), the intermediate layer (12) and the second thin layer (13) are carried out by LIGA.

4. Method according to one of claims 1 to 3, wherein the second material consists solely of nickel and phosphorus.

5. Method according to one of claims 1 to 4, wherein the second material has a percentage by weight of phosphorus of between 1% and 15%.

6. Method according to claim 5, wherein the second material is made of NiP12.

7. Method according to one of claims 1 to 6, wherein the first material comprises only pure nickel, or only nickel and phosphorus.

8. Method according to one of claims 1 to 7, wherein the first material comprises a percentage by weight of phosphorus of less than or equal to 9%.

9. Method according to claim 8, wherein the first material comprises a percentage by weight of phosphorus of between 6% and 9%.

10. Method according to claim 8, wherein the first material comprises a percentage by weight of phosphorus of between 1% and 6%.

11. Method according to claim 8, wherein the first material comprises a percentage by weight of phosphorus of between 0% and 1%.

12. Method according to one of claims 1 to 11, wherein the first material comprises boron.

13. Method according to claim 12, wherein the first material consists solely of nickel and boron.

14. Method according to one of claims 1 to 13, wherein the first material has a thickness of between 0.2 micrometres and 10 micrometres.

15. Method according to one of claims 1 to 14, wherein a heat treatment is applied to an assembly formed by the first thin layer (11), the intermediate layer (12) and the second thin layer (13), at a temperature of between 100°C and 500°C, for 1 to 8 hours.

16. Method according to one of claims 1 to 15, characterised in that it is applied to the manufacture of an escape wheel set which is an escape wheel or pallets.

17. Method according to one of claims 1 to 16, wherein the first thin layer (11), the intermediate layer (12) and the second thin layer (13) are deposited such that the horological wheel set (10) formed has, in the direction and orientation of deposition growth of said layers, a phosphorus concentration gradient defined by progressive increase through the first thin layer (11), a steady state through the intermediate layer (12) and a decrease through the second thin layer (13).

18. Horological wheel set (10) manufactured by carrying out a method according to one of claims 1 to 17, which wheel set comprises an intermediate layer (12) interposed between a first thin layer (11) and a second thin layer (13), said thin layers (11, 13) being made of a first material comprising at least nickel, the intermediate layer (12) being made of a second material comprising at least nickel and phosphorus, the first and second thin layers (11, 13) containing less phosphorus than the intermediate layer (12), or being phosphorus-free.

19. Horological wheel set (10) according to claim 18, constituting an escape wheel or pallets.