Method for producing chamfered gemstones, in particular for timepiece movements

Abstract

The invention relates to a method for producing a chamfered gemstone (8), in particular for a timepiece, characterized in that it comprises the following steps: producing a precursor from a mixture of at least one material in powder form and a binder; pressing the precursor using a top mold and a bottom mold comprising ribs to form a green body; sintering the green body so as to form a green body (30) of a future gemstone (8) in the at least one material, the green body (30) comprising an outer peripheral surface (37) and a bottom surface (32) provided with a recess (40); and machining the body (30), comprising a sub-step of planing the outer peripheral surface (37) up to the groove (40) such that an inner wall (42) of the groove forms at least an open portion of the outer peripheral surface of the gemstone (8). The invention also relates to a device for manufacturing gemstones using the method.

Description

Technical Field

[0001] The invention relates to a method for producing beveled gemstones, in particular for timepiece movements.

[0002] The invention also relates to a manufacturing system suitable for using the method. Background Art

[0003] In the prior art of horology, gemstones of the ruby ​​or sapphire type are used in particular to form end stones or guide elements known as bearings in timepieces. These end stones and guide elements are intended to come into contact with a pivot in order to enable the pivot to rotate with minimal friction. They thus form, for example, all or part of a bearing block of a rotatably mounted shaft. The guide element generally comprises a through hole in order to insert the pivot therein.

[0004] In principle, synthetic gemstones are used in watch movements. In particular, the Verneuil-type method for making single-crystal gemstones is known. There are also polycrystalline gemstones, which are made by pressing a precursor using a pressing tool to obtain a green body of the future gemstone. The gemstone is then machined to obtain the final shape of the desired size.

[0005] In particular, with regard to polycrystalline gemstone guiding elements, the pressing tool is provided with a wire, for example, which helps to construct the hole blank. The monocrystalline gemstone is first laser-drilled to obtain the hole blank. The final size of the hole is then obtained by mechanical machining.

[0006] The gemstone is usually sized to be positioned in a seat of a bearing block assembly. In particular there are shock-absorbing bearing blocks, which are adapted to absorb shocks.

[0007] Figure 1 The construction of a conventional shock-absorbing bearing block 1 is shown. An olive dome-shaped jewel 2 forms an axial guide element for the pivot, often also referred to as a bearing, and a rugby crown jewel is driven into a bearing block support, often referred to as a base 3, on which an end stone 4 is mounted. The base 3 is held pressed against the bottom of a bearing block 5 by elastic means, often a shock-absorbing spring 6, which is arranged to exert an axial force on the top of the end stone 4. Such a shock-absorbing bearing block enables the absorption of shocks along the longitudinal axis of the pivot, the assembly formed by the base, the dome-shaped jewel and the end stone being adapted to move due to the shock-absorbing spring 6.

[0008] The base 3 also comprises an open outer wall aligned with an open inner wall provided at the periphery of the bottom of the support block 5. There is also an alternative embodiment in which the base comprises an outer wall having a convex (i.e. dome-shaped) surface. Thus, the damping support block makes it possible to absorb radial shocks, thanks to the open wall of the base and the open wall of the bottom of the support block 5. In fact, the assembly can move radially and axially at the same time.

[0009] However, it is sought to have a single jewel capable of forming both the guide element and the seat, in order to simplify the arrangement of the elements and to increase the shock resistance. To this end, it is necessary to obtain a jewel with an at least partially open peripheral wall. However, in order to achieve this, current machining methods are complex to implement. Summary of the invention

[0010] The object of the present invention is to completely or partially remedy the above drawbacks by providing a method for manufacturing a gemstone having an at least partially open peripheral surface so as to be insertable into a shock-absorbing support as described above. In this context, this manufacturing method is reproducible without causing any damage to the gemstone or indeed to the system used to manufacture such a gemstone.

[0011] To this end, the invention relates to a method for producing chamfered gemstones, in particular for timepieces. This method is notable in that it comprises the following steps:

[0012] - producing a precursor from a mixture of at least one material in powder form and a binder;

[0013] - pressing the precursor using a top mold and a bottom mold comprising ribs to form a green body;

[0014] - sintering said green body so as to form in said at least one material a body of a future gemstone, said body comprising a peripheral face and a bottom face provided with recesses; and

[0015] - machining said body, including the sub-step of planing said peripheral surface up to said groove, so that the inner wall of said groove forms at least one flared portion of said peripheral surface of said gemstone,

[0016] This method thus makes it possible to easily manufacture chamfered gemstones, preferably polycrystalline, with an at least partially flared peripheral surface. Such gemstones can thus be inserted into a support block having a shape corresponding to the flared surface, in particular for absorbing transverse shocks.

[0017] According to a particular embodiment of the invention, said machining comprises a sub-step of recessing a recess in said top face of said body.

[0018] According to a particular embodiment of the invention, said machining comprises a sub-step of cutting the top face of said body so as to obtain a top face giving said gemstone a predetermined thickness.

[0019] According to a particular embodiment of the invention, the pressing comprises denting the hole blank by means of a punch of said bottom die.

[0020] According to a particular embodiment of the invention, the recess is embodied in a circular shape and / or is centered on the bottom surface of the body.

[0021] According to a particular embodiment of the invention, said rib and said groove have a substantially triangular cross section, one side of which, after planing, will form the flared portion of said peripheral surface of said gemstone.

[0022] According to a particular embodiment of the invention, the groove comprises an inner surface and an outer surface, the outer surface being removed during planing.

[0023] According to a particular embodiment of the invention, said inner face is maintained during planing so as to form a flared portion of said outer peripheral face.

[0024] According to a particular embodiment of the invention, said pressing step is performed by moving said top mould and said bottom mould closer together in a housing.

[0025] According to a particular embodiment of the invention, the sintering step comprises pyrolysis.

[0026] According to a particular embodiment of the invention, the method comprises a step of finishing the gemstone, such as grinding and / or brushing and / or polishing.

[0027] According to a particular embodiment of the invention, said material in powder form is a ceramic-based material and comprises at least a metal oxide, a metal nitride or a metal carbide.

[0028] According to a particular embodiment of the invention, the ceramic-based material in powder form comprises aluminum oxide.

[0029] According to a particular embodiment of the invention, the ceramic-based material in powder form further comprises chromium oxide.

[0030] The invention also relates to a system for producing gemstones using the method according to the invention. The system is notable in that it comprises:

[0031] - an apparatus for producing a precursor from a mixture of at least one material in powder form and a binder;

[0032] - means for pressing said precursor, said means comprising a top mould and a bottom mould arranged to be movable in a housing to help form the green body of the future gemstone, said bottom mould comprising raised ribs;

[0033] - means for sintering the green body; and

[0034] - Device for machining the body of the future gemstone.

[0035] According to a particular embodiment of the invention, said rib is substantially circular and / or centered on said bottom mould.

[0036] According to a particular embodiment of the invention, the rib has a substantially triangular cross section. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Further features and advantages will emerge clearly from the description given hereinafter, which is given by way of indication and not limitation, with reference to the accompanying drawings, in which:

[0038] - Figure 1 Schematically shows a cross section of a shock-absorbing bearing block according to a known embodiment of the prior art;

[0039] - Figure 2 is a diagrammatic representation of a gemstone obtained using the method according to the invention;

[0040] - Figure 3 is a logic diagram associated with a method for manufacturing a gemstone according to the present invention;

[0041] - Figure 4 is a schematic representation of a portion of a green body obtained after the pressing step of the method according to the invention;

[0042] - Figure 5 is a schematic representation of a portion of a gemstone after a first machining sub-step of the method according to the invention;

[0043] - Figure 6 is a schematic representation of a portion of a gemstone after a second machining sub-step of the method according to the invention;

[0044] - Figure 7 is a schematic representation of a portion of a gemstone after a third machining sub-step of the method according to the invention;

[0045] - Figure 8 is a schematic diagram of a system for manufacturing gemstones according to the present invention;

[0046] - Fig. 9 is a schematic diagram of a pressing device of a system according to the present invention; and

[0047] - Fig.10 is a schematic diagram of a bottom mold of a pressing device of a system according to the present invention. DETAILED DESCRIPTION

[0048] As mentioned above, the invention relates to a method for manufacturing a jewel suitable for forming a guide element of a timepiece. The jewel is intended, for example, to come into contact with a pivot in order to enable the latter to rotate with minimum friction. It will thus be understood that the invention makes it possible in particular to produce a jewel suitable for forming all or part of a bearing block of a rotatably mounted shaft.

[0049] Figure 2is an example of a chamfered gemstone 8 obtained with the method according to the invention. Advantageously, the gemstone 8 is traversed by a hole 9 intended to receive a pivot, also called a trunnion. The gemstone 8 comprises a top face 11 and a bottom face 12, one of which comprises a functional element, here a cone 13, communicating with the through hole 9. In other words, the hole 9 communicates with the top face 6 and also with a substantially conical cavity defined in the bottom face 9, which then forms the engagement cone 13 of the drilled gemstone 8.

[0050] In the specification, the terms top surface and bottom surface are described with reference to the drawings, especially to distinguish them. However, the top surface and bottom surface may be reversed.

[0051] It should also be noted that the inner wall of the body of the stone defined at the level of the hole 19 comprises a rounded area 14 intended to minimize contact with the pivot and also to facilitate any lubrication. It should be noted that minimizing contact with the pivot makes it possible in particular to reduce friction with the pivot.

[0052] The chamfered gemstone 8 also has a partially open peripheral surface 15, and connects the bottom surface 12 of smaller surface area to the top surface 11 of larger surface area. The open portion 16 is intended to contact the inner wall of the support block in order to absorb lateral shocks, and due to the open wall, the gemstone can slide on the wall of the support block, such as Figure 1 As in the example.

[0053] The gemstone 8 is preferably formed from a polymorphic mineral body comprising, for example, polycarbonate of the Al2O3Cr type or zirconium oxide of the ZrO2 type.

[0054] Figure 3 The method 20 for making such a gemstone shown in FIG. 2 comprises six steps.

[0055] The first step 21 consists in producing a precursor from a mixture of at least one material in powder form and a binder. This material can be a ceramic, by way of non-limiting and non-exhaustive example. This step aims at forming a precursor from a ceramic-based powder solidified in a binder.

[0056] In this context, the ceramic-based powder may include at least a metal oxide, a metal nitride or a metal carbide. For example, the ceramic-based powder may include aluminum oxide to form synthetic sapphire, or a mixture of aluminum oxide and chromium oxide to form synthetic ruby, or even zirconium oxide. Furthermore, the binder may be of various types, such as polymeric or organic.

[0057] The method then comprises a second step 22 of using Fig. 9 The top and bottom dies of the pressing device shown are used to press the precursor to form the green body of the future gemstone.

[0058] The method comprises a third step 23 of sintering the green body so as to form a Figure 4 In other words, this step 23 aims at sintering the green body so as to form the ceramic body 30 of the future drilled gemstone. Preferably, according to the invention, the sintering step 23 may comprise pyrolysis.

[0059] According to the present invention, the main body 30 includes an outer peripheral surface 37 and a bottom surface 32 provided with a groove 40 . Figure 4 The main body 30 of the gemstone is shown after the sintering step, and the superimposed final gemstone 8 obtained at the end of the manufacturing method after the different steps of machining the main body. This main body comprises a top face 31 and a bottom face 32. The main body 30 also comprises a hole blank 34 provided with a top face 35 and a bottom face 36 of different shapes. In practice, the bottom 35 of the blank forming the functional element has a conical shape and the top 36 of the blank comprising the hole 34 has a cylindrical shape. This hole 34 also comprises a first opening 37 defined in the main body 30 and opening onto the bottom face 32 of this main body 30.

[0060] It should be noted that this blank in particular makes it possible to form the engagement cone 13 of the jewel 8 so as to make it easier to assemble the pivot, in particular when it is blind-assembled into a drilled jewel forming a guide element in this example. It will therefore be understood that the shape of the through hole 9 is provided by the shape of the punch of the bottom die of the pressing device. Figure 3 This step 22 of pressing the device in the embodiment aims to press the precursor using the top and bottom moulds so as to form the green body of the future gemstone 8 .

[0061] According to the present invention, Figure 4 The body 30 in the embodiment of the present invention comprises a groove 40 on its bottom surface 32. The groove 40 is preferably a circular path centered on the hole blank 34. The groove 40 preferably has a generally triangular cross-section. However, other shapes are also possible and may be, for example, slightly convex or concave. As shown in the figure, the diameter of the circular path of the groove 40 determines the width of the final gemstone.

[0062] The groove 40 is circular and centered on the bottom surface of the gemstone. The groove has a generally triangular cross section. The groove includes an inner surface 41 and an outer surface 42 forming two edges of its triangular cross section, and a third edge 43 opens onto the bottom surface of the body. The inner surface 41 will form a flared portion of the outer circumference, while the outer surface 42 will be removed later. The outer circumference of the final gemstone is defined by the groove 40. The groove 40 is formed by the bottom mold of a pressing device, such as Fig. 9 and 10 As shown, the bottom mold includes a negative shape of the groove 40, such as an annular rib.

[0063] exist Figure 3In the method 20, a fourth step 24 is included, namely, machining Figure 4 The fourth step 24 comprises a first sub-step of cutting a recess 45 in the top surface 31 of the body 30. The recess 45 is preferably substantially hemispherical, such as Figure 5 During this sub-step, an opening 46 is created in the blank of the hole 34, which opening is suitable for connecting the cone of the bottom 35 to the recess 45. The hole blank 34 thus comprises a second opening 46 defined in the body and opening into the top face 31 of this body 30.

[0064] The machining step 24 also includes a second sub-step of turning for planing the peripheral wall 37 of the body 30. Figure 6 As shown, material is removed, preferably up to the apex 47 of the groove, to obtain a peripheral wall 15 that is at least partially flared 16, whereby the outer surface 41 is removed during planing. On the other hand, the inner surface 42 is retained to form the flared portion 16 of the peripheral face 15 of the future gemstone. The flared portion 16 extends from the bottom face 12 of the gemstone 8. Another portion 48 of the peripheral wall 15 is substantially straight and preferably connects to the flared portion 16 of the top face 31 from the apex 47 of the groove 40. This substantially straight portion 48 is formed during planing of the body 30. The dimensions of the bottom face 12 of the gemstone 8 are determined by the groove 40, in particular by the junction 49 of the inner surface 42 of the body 30 with the bottom face 32.

[0065] According to an alternative embodiment not shown, the outer peripheral surface can be completely open. In this case, the open portion extends from the bottom surface of the smaller diameter to the top surface of the larger diameter.

[0066] The machining step 24 also comprises a third sub-step, namely, cutting the top face 31 of the body 30 so as to obtain a top face 11 giving the gemstone 8 a predetermined thickness, for example Figure 7 The thickness of the gemstone 8 is selected according to the configuration of the support block.

[0067] The machining step 24 is preferably carried out using laser-type destructive radiation in order to obtain a very precise etching. However, other types of processes may be used to obtain this step 24, for example mechanical excavation such as mechanical drilling or high-pressure water erosion.

[0068] Finally, a fifth finishing step 25 makes it possible to give the gemstone 8 a surface roughness adapted to its use. This finishing step 25 may therefore comprise grinding and / or brushing and / or polishing, making it possible to adjust the final dimensions and / or remove edges and / or locally modify the roughness. For example, it is sought to obtain a surface roughness Ra=0.025 μm. This finishing step 25 may therefore comprise grinding and / or brushing and / or polishing, making it possible to adjust the final dimensions and / or remove edges and / or locally modify the roughness.

[0069] Reference Figure 8 The present invention also relates to a system 50 for manufacturing gemstones. The system 50 includes the following different devices:

[0070] - means 51 for producing a precursor from a mixture of at least one material in powder form and a binder;

[0071] - means 52 for pressing said precursor, comprising top and bottom moulds 57, 58 arranged movably in a housing 59, to help form the green body of the future gemstone 8;

[0072] - means 53 for sintering the green body; and

[0073] - Means 54 for machining the body 30 of the future jewel 8 obtained by sintering the green body.

[0074] It should be noted that at least two of these devices 51 to 54 may together form a single entity of a system 50. Such a system 50 is suitable for executing a method for transmitting a signal to a user via a processor. Figures 4 to 7 Steps in manufacturing Figure 2 The method shown in Gem 8.

[0075] exist Fig. 9 and 10 In the pressing device 52 shown, each mold 57, 58 is fastened to a double-acting press. According to the present invention, one (or both) of the molds 57, 58 is moved closer to the other in the housing 59 of the pressing device 52 along the direction A so as to form not only the top and bottom surfaces 31, 32 of the body 30 of the future gemstone 8, but also the outer peripheral surface 37 of the body 30. In the pressing device 52, the molds 57, 58 are generally planar, and the bottom mold 58 includes a punch 56 intended to form a single eye cavity 34 in the body 30. The punch 56 includes a main portion having a conical shape and a generally cylindrical distal portion provided with a pointed tip. The main portion and the distal portion are intended to form the bottom 35 and the top 36 of the single eye cavity 34, respectively.

[0076] According to the invention, the bottom die 58 also comprises a rib 60 configured to form the groove 40 on the bottom face 32 of the body 30. The rib 60 is preferably circular and centered on the bottom die 58. The rib 60 has a size and shape corresponding to that of the groove 40, since it forms the groove 40 on the bottom face of the body 30. Thus, the rib 60 also preferably has a substantially triangular cross section. The bottom die 58 comprises a surface 62 delimited by the rib 60 and corresponding to the size of the bottom face 12 of the gemstone 8. During pressing, the bottom die 58 equipped with the punch 56 and the rib 60 impresses its shape on the bottom face 32 of the body 30. Thanks to this system 50, the green body sought is obtained, which is then sintered to form the body 30, which will enable the gemstone 8 to be obtained after machining.

[0077] Obviously, the invention is not limited to the examples shown, but is suitable for various alternative embodiments and modifications, which will be obvious to those skilled in the art. In particular, according to the invention, other types of functional elements formed by other geometric configurations of the ribs and / or the molds 57, 58 can be advantageously envisaged.

Claims

1. A method (20) for producing a chamfered gemstone (8) for a timepiece, characterized in that: The chamfered jewel is a single jewel capable of forming both the guide element and the seat of the shock-absorbing bearing block, the method comprising the following steps: - producing (21) a precursor from a mixture of at least one material in powder form and a binder; - pressing (22) the precursor using a top mold (57) and a bottom mold (58) including ribs (60) to form a green body; - sintering (23) the green body so as to form a body (30) of a future gemstone (8) in said at least one material, said body (30) comprising a peripheral surface (37) and a bottom surface (32) provided with a recess (40); and - machining (24) the body (30), including the sub-step of planing the peripheral surface (37) up to the groove (40), so that the inner wall (42) of the groove forms at least one flared portion (16) of the peripheral surface (15) of the gemstone (8), and the flared portion is configured to be in contact with the inner wall of the support block in order to absorb lateral shocks, the gemstone being able to slide on the inner wall of the support block due to the flared portion; The machining (24) includes a sub-step of recessing a recess (45) in the top surface (31) of the main body (30), and the recess (40) is implemented to be circular on the bottom surface (32) of the main body (30).

2. The method according to claim 1, characterized in that The machining comprises a sub-step of cutting the top surface (31) of the body (30) to obtain a top surface (11) that gives the gemstone (8) a predetermined thickness.

3. The method according to any one of claims 1 to 2, characterized in that: The pressing (22) includes: recessing the hole blank (34) by means of a punch (56) of the bottom die (58).

4. The method according to any one of claims 1 to 2, characterized in that The groove (40) is implemented to be centered on the bottom surface (32) of the main body (30).

5. The method according to any one of claims 1 to 2, characterized in that: The rib (60) and the groove (40) have a substantially triangular cross section, one side of which will form the flared portion (16) of the outer peripheral surface (15) of the gemstone (8) after planing.

6. The method according to any one of claims 1 to 2, characterized in that: The groove (40) comprises an inner surface (42) and an outer surface (41), the outer surface (41) being removed during planing.

7. The method according to claim 6, characterized in that The inner surface (42) is maintained during planing to form a flared portion (16) of the outer peripheral surface (15).

8. The method according to any one of claims 1 to 2, characterized in that: The pressing step (22) is performed by moving the top mold (57) and the bottom mold (58) closer together in a housing (59).

9. The method according to any one of claims 1 to 2, characterized in that: The sintering step (23) includes pyrolysis.

10. The method according to any one of claims 1 to 2, characterized in that: The method comprises a step of finishing (25) the gemstone (8), such as grinding and / or brushing and / or polishing.

11. The method according to any one of claims 1 to 2, characterized in that: The material in powder form is a ceramic-based material and includes at least a metal oxide, a metal nitride or a metal carbide.

12. The method according to claim 11, characterized in that The ceramic-based material in powder form includes alumina.

13. The method according to claim 12, characterized in that The ceramic-based material in powder form also includes chromium oxide.

14. A system (50) for manufacturing gemstones (8) using the method according to any one of claims 1 to 13, characterized in that The system comprises: - a device (51) for producing a precursor from a mixture of at least one material in powder form and a binder; - means (52) for pressing the precursor, comprising top and bottom moulds (57, 58) arranged to be movable in a housing (59) to help form the green body of the future gemstone (8), the bottom mould (58) comprising ribs (60); - means (53) for sintering the green compact; and - Means (54) for machining the body (30) of the future gemstone (8).

15. The system according to claim 14, characterized in that The rib (60) is generally circular and / or centered on the bottom mold (58).

16. The system according to claim 14 or 15, characterized in that The rib (60) has a substantially triangular cross section.

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