Method for manufacturing a cam-type timepiece part

Abstract

The present invention relates to a cam-type timepiece part (1), comprising at least one part of substantially flat shape made of a material with a hardness of 600 HV or more, the part having a thickness of 200 microns or more, or 350 microns or more, or 400 microns or more, and comprising at least one functional side (3) substantially perpendicular to the main surface (2) of the part and having a roughness Ra of 50 nm or less.

Description

Technical Field

[0001] The present invention relates to cam-type watch parts. The present invention also relates to watches such as watch movements and small watches including such watch parts. The present invention also relates to a method for manufacturing such watch parts.

Background Art

[0002] Cam-type watch parts have a specific feature of having a lateral surface, also called a side, which is defined to perform a function within a watch movement by cooperating with an adjacent part. Such a lateral surface is also called a "functional side surface". In order to maximize its functionality, such a watch part ideally should have a robust side surface with low roughness and a completely defined orientation, generally within a plane perpendicular to the main surface of the watch part. These watch parts may also have to have a significant thickness due to having a side surface with sufficient surface area, and in this case, it may prove difficult to meet the above-mentioned functional criteria.

[0003] In addition to these specific features of the functional side surface, such watch parts advantageously must also have other properties generally required for watch parts, such as insensitivity to magnetic fields and the possibility of reliable and mass production. Existing methods rely on complex machining steps, although to varying degrees, to obtain a functional side surface within an acceptable range. These methods are cumbersome, not compatible with high speed, and unsuitable for specific dimensions and specific materials.

[0004] Regarding cam-type watch parts, and in other words, regarding all combinations of the above-mentioned limitations regarding functional side surfaces, existing solutions are not completely satisfactory and are not fully optimized, meaning they rely on specific trade-offs.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] For this reason, one general object of the present invention is to disclose an improved solution for clock parts having a cam type or functional aspect.

[0007] More specifically, one object of the present invention is to provide a cam-type clock part solution that enables optimization of the trade-off consisting of proposing industrial manufacturing and achieving the most efficient functional aspect.

Means for Solving the Problems

[0008] For this reason, the present invention is based on a clock part, the clock part being made of ceramic or cermet, having a hardness of 600 HV or more, and including at least a part of a substantially flat shape, the part having a thickness of 200 microns or more, or 350 microns or more, or 400 microns or more, and including at least one functional side substantially perpendicular to the main surface of the part and having a roughness Ra of 50 nm or less.

[0009] The present invention also relates to a method for manufacturing such a clock part, the manufacturing method including the step of laser cutting a thick strip made of ceramic or cermet having a hardness of 600 HV or more by combining two different laser beams in a jet flow or by femtosecond laser cutting to form at least one functional side of the clock part, the clock part having a thickness of 200 microns or more, or 350 microns or more, or 400 microns or more, and the method including an end step. The end step enables, among other things, reducing the roughness of the functional side to a roughness of 50 nm or less.

[0010] Therefore, the clock parts include at least one functional aspect, such as cams, gears, springs, etc.

[0011] More specifically, the present invention is defined by the claims.

[0012] The objectives, features, and advantages of the present invention will be described in detail in the following description of specific embodiments given as non-limiting examples with respect to the accompanying drawings.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Modes for Carrying Out the Invention

[0014] The present invention relies on a manufacturing method that includes a first step of providing a wafer 5 having a selected significant thickness and made of a selected material. As a variant, the wafer can be replaced by any other shape, more generally by a shape referred to as a "thick strip". The material of the thick strip is selected to have a hardness of at least 600 HV, so as to be very hard.

[0015] The manufacturing method of the cam for the clock movement will be described more specifically in accordance with the embodiments of the present invention illustrated in FIGS. 3 and 4. The embodiments can be extended and applied to the manufacture of any cam-type clock part or any clock part having at least one functional aspect.

[0016] According to this embodiment of the present invention, the cam is designed with a very hard material, especially a material having a hardness of 600 HV or more, and has a significant thickness of 200 microns or more, or 350 microns or more, or 400 microns or more.

[0017] According to this embodiment, this material is a ceramic or a cermet. By way of example, the material can be selected from silver-based or copper-based cermets, or cermets known under the names GO312Wrose and Kyocera. The material may also be Al2O3 alumina or zirconia. This also has a hardness of 600 HV or more and is very hard.

[0018] This embodiment involves multi-pass cutting, which requires several passes of the laser beam at the same point to cut through the entire thickness, as described below.

[0019] According to an embodiment of the present invention, the manufacturing method includes a second step of cutting a thick strip. FIG. 1 more specifically illustrates a manufacturing apparatus 10 for implementing a first modification of the second step. The cutting step uses two laser beams with different and complementary properties. According to the first modification of the present embodiment, the method uses a first laser source 11, which is called a master, that is, a green laser with a medium average output that may reach 50 W, a pulse width between 80 and 400 ns, and a frequency between 6 and 20 kHz, and a second laser source 12, which is called a slave, more specifically a green laser with a medium average output that may reach 20 W, a pulse width between 7 and 20 ns, and a frequency between 80 and 130 kHz. These two laser sources 11 and 12 may be used simultaneously or sequentially as shown in FIGS. 1 and 2. In addition, according to the present embodiment, as shown enlarged in FIG. 2, these two laser sources each generate beams 21 and 22 that are guided within the jet 20. Such guidance is described in detail in Patent Document 1, among others. As described above, regardless of whether the two laser sources 11 and 12 are used simultaneously or sequentially, depending on the type and thickness of the material, the cutting mode is preferably performed in multiple passes.

[0020] Depending on the type and thickness of the material, the medium average output of the laser source can be reduced, for example, to a value between 10 and 12 W for the master laser source or to a value between 2 and 19 W for the slave laser source. More specifically, in the case of an alumina strip with a thickness of 200 microns, the medium average output of the slave laser source can be reduced to between 18 and 19 W. As a modification, other combinations of the two laser sources may be implemented.

[0021] Alternatively, according to a second variant of an embodiment of the invention, the manufacturing method comprises a second step consisting of cutting a thick strip using a green femtosecond laser with an average output that may reach 55 W and a pulse time / width between 270 fs and 10 ps and a frequency in the range from 1 kHz to 2000 MHz. As a variant, other laser sources with ultrashort pulses may be used, such as a source emitting in the infrared (1030 nm) or ultraviolet (343 nm).

[0022] Finally, the manufacturing method advantageously comprises - polishing of the main surface of the cam, and / or - tribo-finishing of the functional side or sides to reduce roughness, an end step comprising all or part of the additional steps of

[0023] In addition, the manufacturing method may include a cleaning step.

[0024] Figures 3 and 4 show a heart-shaped cam 1 of a watch movement according to an embodiment of the invention. The cam is obtained by the manufacturing method described above and has a thickness of 440 microns. The cam is obtained from a thick strip with a thickness of 480 microns and its thickness has been reduced after the polishing finishing stage of its flat main surface 2. The cam 1 also has a functional side 3 perpendicular to its main surface 2 according to the following definition. Furthermore, after the end step, in particular after the polishing or tribo-finishing step, the functional side 3 of the finished cam has a roughness Ra lower than 50 nm.

[0025] More generally, the present invention appears to rely on new optimal conditions in which a cam-type timepiece part simultaneously has a high hardness of 600 HV or more, a significant thickness of 200 microns or more, or 350 microns or more, or 400 microns or more, or 430 microns or more, a controlled orientation with a maximum difference of 1 degree with respect to a desired orientation, and a very low roughness Ra of 50 nm or less. In particular, the functional side has an angle greater than 89 degrees with respect to the plane of the adjacent main surface. The functional side has an angle between 89 and 90 degrees, or between 89 and 91 degrees with respect to the plane. The roughness Ra may be 40 nm or less, or 30 nm or less. The combination of these features is optimal. In fact, the present invention makes it possible to achieve ideal results for each parameter without privileging some and disadvantaging others, which is remarkable.

[0026] The timepiece part according to the present invention may be any part having at least one functional side. Advantageously, the timepiece part has a substantially two-dimensional shape including one or more functional sides arranged in its contour between two opposing flat main surfaces. For this reason, its thickness is measured as the distance between the two opposing main surfaces. As a variant, the concept can be extended to more complex timepiece parts including at least a part corresponding to an embodiment of the present invention. Also as a variant, the present invention is applicable to parts having a structure close to a three-dimensional shape in which the main surfaces are not flat, for example, but substantially flat. In this case, the thickness considered is the average thickness at the end of the main surface adjacent to the functional side considered. Thus, the present invention is applied to at least a part of the substantially flat shape of the timepiece part, and the part is a thinner surface extending in the thickness direction in this part and is defined by two substantially flat and parallel surfaces called main surfaces, which are connected by a surface forming the side of the timepiece part. The part of the timepiece part is advantageously made of a single material and is integrally formed.

[0027] As an example, the timepiece component may be a cam such as a heart-shaped cam, a spiral or notched spiral cam, a shuttle or column wheel. The timepiece component may be a date disk. The timepiece component may include one or more functional sides disposed on its outer periphery. The timepiece component may operate by performing a complete or incomplete rotation, for example by performing a reciprocating motion. Of course, the present invention is not limited to the above examples.

[0028] Finally, the present invention relates to a timepiece movement comprising a timepiece component having at least one such functional side. The present invention also relates to a timepiece comprising a timepiece component having at least one such functional side.

Claims

1. A method for manufacturing a cam-type timepiece part, comprising a step of cutting a thick strip made of ceramic or cermet having a hardness of 600 HV or more by a combination of two different laser beams in a jet stream to form at least one functional aspect (3) of the timepiece part, the timepiece part having a thickness of 200 microns or more, and the method comprising an end step for obtaining a roughness Ra of the functional aspect (3) of 50 nm or less, The cutting step includes the use of two different laser beams in the jet stream resulting from a first, master laser source and a second, different, slave laser source, respectively, to obtain the two different laser beams alternately or continuously, The first, master laser source is a green laser having a medium average output of 50 W or less, a pulse width between 80 and 400 ns, and a frequency between 6 and 20 kHz, and the second, slave laser source is a green laser having a medium average output of 20 W or less, a pulse width between 7 and 20 ns, and a frequency between 80 and 130 kHz, A method for manufacturing a cam-type timepiece part.

2. The end step is, polishing the functional aspect or aspects to reduce the roughness, including an additional step of The method for manufacturing a cam-type timepiece part according to claim 1.

3. The thickness is 400 microns or more, The method for manufacturing a cam-type timepiece part according to claim 1 or 2.

4. The cam-type timepiece part includes a flat main surface (2), and the functional aspect (3) is substantially perpendicular to the main surface, extends from the flat main surface, and has an angle of 89 degrees or more and 91 degrees or less with respect to the flat main surface, The method for manufacturing a cam-type timepiece part according to any one of claims 1 to 3.

5. The at least one functional aspect (3) has a roughness Ra of 40 nm or less. A method for manufacturing a cam-type timepiece part according to any one of claims 1 to 4.

6. The cam-type timepiece part is a cam such as a heart-shaped cam, a spiral or notched spiral cam, a shuttle or column wheel. A method for manufacturing a cam-type timepiece part according to any one of claims 1 to 5.

7. The cutting step includes the use of two different laser beams in the jet stream and is a multi-pass cutting step that requires several passes of the laser beam at the same point to cut through the entire thickness. A method for manufacturing a cam-type timepiece part according to claim 1.

8. The cutting step includes the use of a femtosecond laser and is a step of multi-pass cutting of the thick strip that requires several passes of the laser beam at the same point to cut through the entire thickness. A method for manufacturing a cam-type timepiece part according to claim 1.

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