CLOCKWORK COMPONENT OF THE CAM TYPE

Description

Introduction

[0001] The present invention relates to a cam-type watch component made of ceramic or cermet.

[0002] The invention also relates to a watch movement and a timepiece, such as a watch, comprising such a watch component. It also relates to a method for manufacturing such a watch component. State of the Art

[0003] A cam-type watch component is characterized by a lateral surface, which we will call the flank, designed to perform a function within a watch movement by interacting with a neighboring component. Such a lateral surface can also be called a "functional flank." To best fulfill their function, these watch components should ideally have a rigid flank with low roughness and a precisely defined orientation, generally in a plane perpendicular to a main surface of the watch component. These watch components may also need to be quite thick to provide a sufficient flank surface area, which can be difficult to reconcile with the functional criteria listed above.

[0004] In addition to these specific properties of a functional flange, such a watch component must advantageously exhibit the other properties generally expected of a watch component, such as insensitivity to magnetic fields and the ability to be reliably manufactured in large series. Existing processes rely on more or less complex machining steps to obtain an acceptable functional flange. These processes are tedious and often incompatible with high production rates, or even unsuitable for certain geometries or materials. Prior art documents such as EP3260932A1 and the article by Jean-René Gonthier, "New dual laser coupled with water jet," exist. " who are already seeking a solution to the constraints mentioned above, but they are not always suitable for cam-type watch components.

[0005] The combination of all the constraints mentioned above on a cam-type watch component, or in other words a functional flank component, means that the existing solutions are not totally satisfactory, and that they rely on certain compromises that are not totally optimized.

[0006] Thus, a general object of the invention is to define an improved solution for a cam-type or functional flank watch component made of ceramic or cermet.

[0007] More specifically, one object of the invention is to offer a cam-type watch component solution that optimizes the compromise of offering industrial manufacturing while achieving the highest possible functional performance. Brief description of the invention

[0008] To this end, the invention is based on a watch component according to the terms of claim 1 as annexed.

[0009] The invention also relates to a method for manufacturing such a watch component, characterized in that it comprises a laser cutting step of a thick ceramic or cermet strip with a hardness greater than or equal to 600 HV, by combining two different laser beams within a liquid jet or by femtosecond laser cutting, to form at least one functional edge of the watch component, said watch component having a thickness greater than or equal to 200 microns, or even greater than or equal to 350 microns, or even greater than or equal to 400 microns, and in that it comprises a finishing step. This finishing step makes it possible, in particular, to reduce the roughness of said functional edge to a roughness less than or equal to 50 nm.

[0010] The watch component therefore includes at least one functional part, such as a cam, a wheel, a spring, etc.

[0011] The invention is more precisely defined by the claims. Brief description of the figures

[0012] These features, characteristics and advantages of the invention will be described in detail in the following description of a particular embodiment, given by way of non-limiting example, in relation to the accompanying figures, among which: There figure 1 represents a device for manufacturing a cam-type watch component according to an embodiment of the invention. figure 2 is an enlargement of part of the previous figure. The figures 3 and 4 represent perspective views from different angles of a cam-type watch component according to an embodiment of the invention.

[0013] The invention is based on a manufacturing process that includes a first step of providing a wafer 5 of a chosen thickness and made of a chosen material. Alternatively, the wafer could be replaced by any other shape, which we will more generally call a "thick strip". The material of this thick strip is chosen to be very rigid, in particular with a hardness greater than or equal to 600 HV.

[0014] We will now describe a method for manufacturing a cam for a watch movement according to an embodiment of the invention, more particularly represented by the figures 3 and 4 This embodiment can be extended to the manufacture of any cam-type watch component, or any watch component comprising at least one functional side.

[0015] According to this embodiment of the invention, the cam is designed in a very rigid material, in particular with a hardness greater than or equal to 600 HV, and has a significant thickness, greater than or equal to 200 microns, or even greater than or equal to 350 microns, or even greater than or equal to 400 microns.

[0016] According to the invention, the material is a ceramic or a cermet.

[0017] For example, this material can be chosen from silver-based or copper-based cermets, or cermets known by their designations GO312Wrose and Kyocera. It can also be alumina (Al2O3) or zirconia. It is also very rigid, with a hardness of 600 HV or higher.

[0018] This embodiment involves multi-pass cutting, which requires several passes of a laser beam over the same place to cut through the entire thickness, as will be detailed below.

[0019] According to the embodiment of the invention, the manufacturing process then comprises a second step consisting of cutting the thick strip. figure 1 This more precisely represents a manufacturing device 10 that implements this second step according to a first variant. This cutting step uses two laser beams of different and complementary nature. According to the first variant of the embodiment, the process uses a first laser source 11, called MASTER, that is, a green laser with a mean full power (MFP) of up to 50 W, with a pulse duration between 80 and 400 ns and a frequency of 6 to 20 kHz, and a second laser source 12, called SLAVE, more precisely a green laser with a mean full power (MFP) of up to 20 W, with a pulse duration between 7 and 20 ns and a frequency of 80 to 130 kHz. These two laser sources 11 and 12 can be used simultaneously, as illustrated in the figures. figures 1 and 2 , or successively. In addition, depending on the embodiment, these two laser sources respectively generate a beam 21, 22 which is guided within a liquid jet 20, as shown in the enlargement of the figure 2 Such guidance is detailed in document EP1750894. Depending on the type of material and its thickness, the cutting method will preferably be done in multi-passes, as mentioned previously, regardless of the simultaneous or successive use of the two laser sources 11 and 12.

[0020] Depending on the type and thickness of the material, the mean full power at half maximum (MFU) of the laser sources can be reduced, for example, to values ​​between 10 and 12 W for the MASTER laser source or between 2 and 19 W for the SLAVE laser source. Specifically, for alumina strips 200 microns thick, the MFU of the SLAVE laser source can be between 18 and 19 W. Alternatively, other combinations of two laser sources can be implemented.

[0021] Alternatively, according to a second embodiment of the invention, the manufacturing process comprises a second step consisting of cutting the thick strip using a green femtosecond laser with an average power of up to 55 W, with pulse durations ranging from 270 fs to 10 ps and a frequency ranging from 1 kHz to 2000 MHz. Alternatively, other ultrashort pulse laser sources, such as sources emitting in the infrared (1030 nm) or ultraviolet (343 nm), may be used.

[0022] Finally, the manufacturing process advantageously includes a finishing step, which includes all or part of the following additional steps: Polishing the main surface of the cam to reduce roughness and ensure the final thickness; and / or Tribofinishing the functional flank(s) to reduce roughness.

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

[0024] THE figures 3 and 4 illustrate a heart-shaped watch movement cam 1 as claimed, according to an embodiment of the invention. It was obtained by the manufacturing process described above and has a thickness of 440 microns. It was obtained from a strip 480 microns thick and underwent a finishing step of polishing its main flat surface 2, which reduced its thickness. The cam 1 also has functional flanks 3 perpendicular to its main surface 2 as defined below. Furthermore, after a finishing step, in particular after a polishing or tribofinishing step, the functional flanks 3 of the finished cam have a roughness Ra of less than 50 nm.

[0025] More generally, it appears that the invention is based on a new optimum in which a cam-type watch component comprises both a high hardness greater than or equal to 600 HV, a significant thickness greater than or equal to 200, or even greater than or equal to 350 microns, or greater than or equal to 400 microns, or even greater than or equal to 430 microns, a functional flank with controlled orientation, deviating by a maximum of one degree from the desired orientation, and very low roughness Ra, less than or equal to 50 nm. In particular, the functional flank has an angle greater than 89 degrees with respect to the plane of the adjacent main surface. It comprises an angle between 89 and 90 degrees or between 89 and 91 degrees with respect to this plane. The roughness Ra can even be less than or equal to 40 nm, or even less than or equal to 30 nm.The combination of these characteristics is optimal; the invention makes it possible to achieve an ideal result on each parameter, without favoring some at the expense of others, which is remarkable.

[0026] The watch component according to the invention can be any component having at least one functional side. Advantageously, this watch component comprises a substantially two-dimensional shape, including one or more functional sides arranged on its contour between two opposing plane principal surfaces. Its thickness is therefore measured as the distance between these two opposing plane principal surfaces. Alternatively, this concept can be extended to a more complex watch component, including at least one part corresponding to an embodiment of the invention. Alternatively again, the invention also applies to a component that might have a structure closer to a three-dimensional shape, its principal surfaces not being, for example, plane, but substantially plane. The thickness considered will then be the average thickness at the ends of the principal surfaces adjacent to the functional side in question.The invention thus applies to at least one substantially flat portion of a watch component, this portion being defined by two substantially flat and parallel surfaces, called principal surfaces, connected by a narrower surface extending through the thickness of said portion, forming a side of the watch component. This portion of the watch component is advantageously made of a single material, in a monolithic form.

[0027] According to the invention, the timekeeping component may be a cam, such as a heart, a snail, a shuttle, or a column wheel. In a manner not included in the invention, the component may be a date disc. It may comprise one or more functional flanges arranged around its circumference. It may operate by completing a full or partial rotation, for example, by moving back and forth. Naturally, the invention is not limited to the preceding examples.

[0028] Finally, the invention also relates to a watch movement incorporating at least one such functional side-mounted watch component. It also relates to a timepiece incorporating at least one such functional side-mounted watch component.

Claims

1. A cam-type timepiece component (1), comprising at least one part of substantially flat form made of ceramic or of cermet with a hardness greater than or equal to 600 HV, said part having a thickness greater than or equal 350 microns, and characterized in that it comprises at least one functional flank (3) substantially perpendicular to a main surface (2) of said part and with a roughness Ra less than or equal to 50 nm.

2. The cam-type timepiece component as claimed in one of the preceding claims, characterized in that said thickness is greater than or equal to 400 microns.

3. The cam-type timepiece component as claimed in one of the preceding claims, characterized in that it has a flat main surface (2) and in that said at least one substantially perpendicular functional flank (3) extends from this flat main surface and has an angle of between 89 and 91 degrees inclusive with respect to this flat main surface.

4. The cam-type timepiece component as claimed in one of the preceding claims, characterized in that said at least one functional flank (3) has a roughness Ra less than or equal to 40 nm, or even less than or equal to 30 nm.

5. The cam-type timepiece component as claimed in one of the preceding claims, characterized in that it is a cam, such as a heart-shaped cam, a spiral or notched cam snail, a shuttle or a column-wheel.

6. A horological movement, characterized in that it comprises a timepiece component as claimed in one of the preceding claims.

7. A timepiece, characterized in that it comprises a timepiece component as claimed in one of claims 1 to 5 or a horological movement as claimed in the preceding claim.

8. A method for manufacturing a cam-type timepiece component as claimed in one of claims 1 to 5, characterized in that it comprises a step of cutting of a thick strip of ceramic or of cermet with a hardness greater than or equal to 600 HV, by the combination of two different laser beams within a liquid jet or by one laser beam of a femtosecond laser to form at least one functional flank (3) of the timepiece component, said timepiece component having a thickness greater than or equal to 200 microns, or even greater than or equal to 350 microns, or even greater than or equal to 400 microns and in that it comprises a termination step to obtain a roughness Ra of the functional flank (3) less than or equal to 50 nm.

9. The method for manufacturing a cam-type timepiece component as claimed in the preceding claim, characterized in that the cutting step comprises the use of two different laser beams within a liquid jet, originating respectively from a first, MASTER laser source and from a second, different, SLAVE laser source to obtain the at least two different laser beams, alternating or in succession.

10. The method for manufacturing a cam-type timepiece component as claimed in the preceding claim, characterized in that said first, MASTER laser source is a green laser with an average power at mid-height less than or equal to 50 W with a pulse duration of between 80 and 400 ns and a frequency of between 6 and 20 kHz, and in that said second, SLAVE laser source is a green laser with an average power at mid-height less than or equal to 20 W with a pulse duration of between 7 and 20 ns and a frequency of between 80 and 130 kHz.

11. The method for manufacturing a cam-type timepiece component as claimed in claim 8 or 10, characterized in that the cutting step comprises the use of two different laser beams within a liquid jet and is a multi-pass cutting step.

12. The method for manufacturing a cam-type timepiece component as claimed in claim 8, characterized in that the cutting step comprises the use of a femtosecond laser and is a step of multi-pass cutting of said thick strip.

13. The method for manufacturing a cam-type timepiece component as claimed in one of claims 8 to 12, characterized in that the termination step comprises all or part of the following additional steps: - a polishing of the main surface of the cam; and / or - a tribofinishing of the functional flank or flanks so as to reduce the roughness.