HK1232618B - Component fabrication method including a modified burnishing step - Google Patents

Description

Method for manufacturing a component including an improved grinding step

Technical Field

The present invention relates to a manufacturing method comprising an improved grinding step, more particularly a step of this type providing improved surface flatness.

Background Art

From WO publication No. 2015/185423 it is known how to form a timepiece component from a component comprising a silicon-based or ceramic-based material, which component is directly welded to another component, for example a metal or metal alloy component, by electromagnetic radiation.

In the context of this improvement it is important that the gap between components does not exceed 0.5 microns, otherwise they cannot be welded together.

Summary of the Invention

The object of the present invention is to overcome all or part of the aforementioned drawbacks by proposing a new manufacturing method in which at least one contact surface has an improved flatness so as to enable the components to be assembled by welding.

Therefore, the present invention relates to a method for manufacturing a timepiece component, comprising the following steps:

- obtaining a rod made of metal;

- profile turning the rod to form at least one diameter portion comprising a substantially vertical surface and a substantially horizontal surface;

- grinding the rod to increase its hardness and improve its surface condition, thereby obtaining a first component made of metal;

- mounting the surface of the first component on the surface of the second component;

- welding the surface of the first component mounted on the surface of the second component by laser electromagnetic radiation to fasten the components to each other;

Characterized in that, in the grinding step, the grinder moves along the generally vertical surface until the grinder also comes into contact with the generally horizontal surface to polish the generally horizontal surface as the grinder moves away from the generally vertical surface.

Advantageously, according to the invention, the manufacturing method provides one face with an extremely flat vertical surface to ensure proper welding.

According to other advantageous variants of the invention:

- the turning step further forms an inclined wall between the generally vertical surface and the generally horizontal surface to prevent burr formation when the grinder comes into contact with the generally horizontal surface;

- the turning step further forms a curved wall around the substantially horizontal surface to prevent burrs from forming when the grinder comes into contact with the substantially horizontal surface;

The second component is formed from silicon or from ceramic;

- the second component further comprises at least one partial coating consisting of a metal, silicon oxide, silicon nitride, silicon carbide or an allotrope of carbon;

The first metal-based component comprises an iron alloy, a copper alloy, nickel or a nickel alloy, titanium or a titanium alloy, gold or a gold alloy, silver or a silver alloy, platinum or a platinum alloy, ruthenium or a ruthenium alloy, rhodium or a rhodium alloy, palladium or a palladium alloy.

BRIEF DESCRIPTION OF THE DRAWINGS

Other characteristics and advantages will emerge on reading the following description, given by way of non-limiting example, with reference to the accompanying drawings in which:

- Figure 1 is a perspective view of a sprung balance resonator;

- FIG. 2 is a perspective view of a balance spring according to the invention;

- FIG3 is a perspective view of a balance staff according to the invention;

- FIG. 4 is a cross-sectional view of an assembly according to WO Publication No. 2015/185423;

- Figures 5 and 6 are cross-sectional views of a grinding operation according to a first embodiment of the present invention;

- Figures 7 and 8 are cross-sectional views of a grinding operation according to a second embodiment of the present invention;

- Figure 9 is a cross-sectional view of an assembly according to the invention.

DETAILED DESCRIPTION

The present invention relates to a component formed using a material having no usable plastic range (ie having a very limited plastic range) and a second component comprising the same type of material or a different type of material.

This component is designed for use in the horological field and is necessitated by the addition of a portion formed from a fragile or brittle material, such as a silicon-based or ceramic-based material. It is conceivable, for example, that the case, dial, flange, crystal, bezel, push-pieces, crown, case back, hands, bracelet or strap, balance spring, balance, pallets, bridges or cocks, oscillating weight or even a wheel such as an escape wheel be formed entirely or partially from a fragile or brittle material.

Preferably, the silicon-based material used to manufacture the compensation spring may be single-crystalline silicon (regardless of its crystal orientation), doped single-crystalline silicon (regardless of its crystal orientation), amorphous silicon, porous silicon, polycrystalline silicon, silicon nitride, silicon carbide, quartz (regardless of its crystal orientation), or silicon oxide. Of course, other materials are also conceivable, such as glass, ceramic, cermet, metal, or metal alloy. Furthermore, the first silicon-based component may optionally include at least one partial coating consisting of an allotrope of silicon oxide, silicon nitride, silicon carbide, or carbon, depending on the intended application of the timepiece component.

As described above, the further component may comprise the same type of material or a different type of material. Thus, preferably, the further component is metal-based and may comprise an iron alloy, a copper alloy, nickel or a nickel alloy, titanium or a titanium alloy, gold or a gold alloy, silver or a silver alloy, platinum or a platinum alloy, ruthenium or a ruthenium alloy, rhodium or a rhodium alloy, palladium or a palladium alloy.

For the sake of simplicity, the following description will refer to the assembly between the balance spring and the balance staff. FIG1 shows a resonator 1 in which a balance spring 5 is used for temperature compensation of the entire resonator assembly 1 (i.e., all components and, in particular, the balance wheel 3, which is mounted on the same balance staff 7). Resonator 1 cooperates with a retaining system, such as a Swiss lever escapement (not shown), which cooperates with an impulse pin 9 of a table-roller 11, also mounted on the balance staff 7.

Compensating balance spring 15 is more clearly shown in FIG2 . This balance spring comprises a single strip 16 wound around itself between an inner coil 19 integral with collet 17 and an outer coil 12 including an end 14 intended to be pinned to a collet. As can be seen in FIG2 , to improve the isochronism of the resonator in which balance spring 15 is used, balance spring 15 comprises an inner coil 19 having a Grossmann curve and an outer coil 12 having a portion 13 that is thicker than the rest of balance spring 15. Finally, it can be seen that collet 17 comprises a single strip extending in a generally triangular shape, so that it exhibits elasticity when mounted on a balance staff, and in particular allows it to be centered relative to the staff.

The balance staff 27 is more clearly shown in Figure 3. It comprises in particular several diameters 22, 24, 26 for receiving the balance spring, the balance wheel and the disc respectively. As shown in Figure 3, the diameter 22 comprises a cylindrical shaft 21, the edge of which is provided with a shoulder 23 in its lower part.

As shown in FIG4 , diameter portion 22 serves to receive collet 17 of balance spring 15 between shaft 21 and shoulder 23. More specifically, inner surface 20 of collet 17 is elastically pressed against the outer surface of shaft 21, and lower surface 18 of collet 17 is pressed against shoulder 23. Finally, as indicated at 28, shaft 21 and/or shoulder 23 are welded to collet 17 in accordance with the teachings of WO Publication No. 2015/185423.

However, upon studying the teachings of WO Publication No. 2015/185423, it quickly becomes clear that the gap between components must not exceed 0.5 micrometers, otherwise they cannot be welded together.

The method according to the first embodiment of the invention thus consists in obtaining a bar capable of undergoing profile-turning. As the example concerns the assembly between a balance spring and a balance staff, the bar can be made of metal or of a metal alloy.

The second step aims at profile turning the various diameters required to form balance staff 47, and in particular diameter portion 42 of collet 17 intended to receive balance spring 15. As can be seen in FIG5 , diameter portion 42 comprises a substantially vertical surface 41 of the preform forming the staff and a substantially horizontal surface 43 of the preform forming the shoulder.

The method continues with a third step aimed at grinding the substantially vertical surface 41 to increase its hardness and improve its surface condition and thus form the shaft 41 '. Advantageously and according to the invention, during a first stage of the grinding step, the grinder 30, mounted rotatably about B, is displaced in direction A via its main surface 31 along the length of the substantially vertical surface 41, which is also mounted rotatably about C, as can be seen in FIG5 .

Furthermore, during the second phase of the grinding step, the grinder 30 continues its displacement in the direction A' until the grinder 30 also comes into contact with the substantially horizontal surface 43 via its side surface 32. It will thus be understood that as the grinder 30 moves in the direction D away from the substantially vertical surface formed by the axis 41', the side surface 32 of the grinder 30 will polish the substantially horizontal surface 43, thereby forming a very flat and horizontal shoulder 45, as can be seen in FIG6 .

Thus, after finishing steps including, for example, a deburring step, the balance staff 47' obtained provides an extremely flat welding surface 45 to ensure proper welding with another component, as taught in WO publication No. 2015/185423.

In a fourth step of the method, collet 17 is then mounted to diameter portion 42 ′, i.e. inner surface 20 of collet 17 is elastically pressed against the surface of shaft 41 ′ and lower surface 18 of collet 17 is pressed against the surface of shoulder 45 .

Finally, in a final welding step, at least a portion of inner surface 20 and/or lower surface 18 of collet 17 is laser welded to balance staff 47', so as to ensure that balance spring 15 and balance staff 47' are secured to each other.

The method according to a second embodiment of the invention comprises a first step of obtaining a bar capable of undergoing profile turning. Since the example concerns the assembly between a balance spring and a balance staff, this bar can be made of metal or of a metal alloy.

The second step aims at profile turning the various diameters required to form balance staff 57 and in particular diameter portion 52 of collet 17 intended to receive balance spring 15. As can be seen in FIG7 , diameter portion 52 comprises a substantially vertical surface 51 of the preform forming the staff and a substantially horizontal surface 53 of the preform forming the shoulder.

In contrast to FIG5 , as can be seen in FIG7 , the profile turning step is specifically intended to form an inclined wall 54 which, starting from the cut made by the turning tool, faces a substantially horizontal surface 53 which is also substantially perpendicular to the substantially vertical surface 51 but which has a more limited width than the surface 43 of FIG5 . It will be understood that, in the case of a balance staff, the inclined wall 54 thus forms a cone.

The method continues with a third step aimed at grinding the substantially vertical surface 51 to increase its hardness and improve its surface condition and thus form the shaft 51 '. Advantageously and according to the invention, during a first stage of the grinding step, the grinder 30, mounted rotatably about B, is displaced in direction A via its main surface 31 along the length of the substantially vertical surface 51, which is also mounted rotatably about C, as can be seen in FIG7 .

Furthermore, during the second phase of the grinding step, the grinder 30 continues its displacement in the direction A' until the grinder 30 also comes into contact with the substantially horizontal surface 53 via its side surface 32. It will therefore be understood that as the grinder 30 moves in the direction D away from the substantially vertical surface formed by the axis 51', the side surface 32 of the grinder 30 will polish the substantially horizontal surface 53, thereby forming a very flat and horizontal shoulder 55 as seen in FIG.

Thus, after finishing steps including, for example, a deburring step, the resulting balance staff 57' provides an extremely flat welding surface 55 to ensure proper welding with another component, as taught in WO Patent Publication No. 2015/185423. It can also be seen that, compared to the first embodiment, the second embodiment prevents the formation of burrs between the preform 43 and the final shoulder 45 as seen in FIG6.

In a fourth step of the method, the collet 17 is then mounted to the diameter portion 52', i.e. with its inner surface 20 against the surface of the shaft 51' and with its lower surface 18 against the surface of the shoulder 55.

Finally, in a final welding step, at least a portion of inner surface 20 and/or lower surface 18 of collet 17 is laser welded to balance staff 57′, so as to ensure that balance spring 15 and balance staff 57′ are secured to one another, as shown in FIG9 . It should also be noted that, compared to the first embodiment, the second embodiment makes it possible to provide a welding surface of shoulder 55 reduced to a width L, which, incidentally, makes it less susceptible to flatness problems.

Of course, the present invention is not limited to the examples shown, but is capable of various variations and modifications that will be apparent to a person skilled in the art. In particular, the grinder 30 is not limited to the one presented in this description. In fact, the grinder may have different geometries to obtain different surfaces, depending on the desired application.

Furthermore, as an alternative to the inclined wall 54 of the second embodiment, a profile turning step can be used to intentionally form a curved wall starting from the cut made by the turning tool. It will be understood that in this alternative, the curved wall will thus form a toric surface instead of a flat surface 53 followed by a taper 54 as in the second embodiment.

Claims (6)

1. A method for manufacturing a clock component, comprising the following steps: - Obtain rods made of metal; - The rod is profiled and turned to form at least one diameter portion (42, 52) including a generally vertical surface (41, 51) and a generally horizontal surface (43, 53); - Grind the rod to increase its hardness and improve its surface condition, and thus obtain a first component (47’, 57’) made of metal; - The surfaces (41', 45, 51', 55) of the first component (47', 57') are mounted on the surfaces (18, 20) of the second component (15); - The surfaces (41', 45, 51', 55) of the first component (47', 57') mounted on the surfaces (18, 20) of the second component (15) are fastened together by laser electromagnetic radiation welding. The feature is that, in the polishing step, the polisher (30) is moved along the length of the generally vertical surfaces (41, 51) via the main surface (31) of the polisher (30) until the polisher (30) also comes into contact with the generally horizontal surfaces (43, 53) via the side surface (32) of the polisher (30) to polish the generally horizontal surfaces (43, 53) as the polisher (30) moves away from the generally vertical surfaces (41, 51), wherein the polisher (30) is rotatably mounted about an axis (B) perpendicular to the generally vertical surfaces (41, 51). 2. The method according to claim 1, wherein the contour turning step further forms an inclined wall (54) between the generally vertical surfaces (41, 51) and the generally horizontal surfaces (43, 53) to prevent burrs from forming when the grinder (30) comes into contact with the generally horizontal surfaces (43, 53). 3. The method according to claim 1, wherein the contour turning step further forms an inclined wall around a generally horizontal surface (43, 53) to prevent burrs from forming when the grinder (30) comes into contact with the generally horizontal surface (43, 53). 4. The method according to claim 1, wherein the second component (15) is made of silicon or ceramic. 5. The method according to claim 4, wherein the second component (15) further comprises at least one local coating composed of a metal, silicon oxide, silicon nitride, silicon carbide or an allotrope of carbon. 6. The method according to claim 1, wherein the first component (47’, 57’) made of metal comprises an iron alloy, a copper alloy, a nickel or nickel alloy, a titanium or titanium alloy, a gold or gold alloy, a silver or silver alloy, a platinum or platinum alloy, a ruthenium or ruthenium alloy, a rhodium or rhodium alloy, or a palladium or palladium alloy.