The invention relates to the technical watchmaking field.
It relates to a timepiece component in a composite material.
It also relates to a method for manufacturing a timepiece component in a composite material.
Timepiece components are conventionally made up of metallic materials such as stainless steel, titanium, or precious materials such as gold, platinum or silver.
Increasingly, metallic materials are replaced with composite materials for the manufacture of some timepiece components, due to their light weight and aesthetic properties.
According to a first aspect, the invention relates to a method for manufacturing timepiece components from a carbon-carbon composite material part.
More specifically, the method for manufacturing a timepiece component comprises a step for processing a carbon-carbon composite material part.
The carbon-carbon composite material is appreciated for its properties that include very good heat resistance, very good resistance to heat shocks and very good resistance to wear during friction at high temperature. Therefore, it is used to manufacture:
The article “Carbon-carbon composite materials” by Jacques Thébault and Pierre Olry, published in the magazine “L′actualité chimique”-March-April 2006-no. 295-296 describes the carbon-carbon composite material as resulting from the fusion between a fibrous stiffener and a binding matrix that both have the same chemical nature.
The fibrous stiffener is made up of a carbon fibre texture, produced via mechanical means used in the textile industry. The binding matrix is a carbonaceous matrix whose role is to fill the pores in the fibrous structure.
According to a first aspect of the invention, the method for manufacturing a timepiece component comprises a processing step of a carbon-carbon composite material part.
According to a first variant of the first aspect of the invention, the manufacturing method comprises steps for machining and a step for processing said part.
According to a characteristic of the method according to the first variant, the processing step is preceded by a first step for machining the carbon-carbon composite part and followed by a second step for machining said part.
The first machining step is a pre-machining step by milling, for the preparation of a face of the part before the processing step. In particular, areas having a predetermined raised section are created on said face. According to the required timepiece component, areas having a predetermined hollow section can also be created on said face.
The second machining step is an actual machining step by milling of the same face of said part after the processing step.
According to another characteristic, the method according to the first variant comprises at least one additional machining step, subsequent to the second machining step. Said at least one additional machining step can be a part trimming step, a milling step of the other face of the part, a finishing step.
The processing step comprises a resin casting operation that consists of pouring liquid resin onto the face of the part that has undergone the pre-machining operation. The resin may be a thermosetting resin, such as an epoxy resin or a phenolic resin. The resin may be a thermoplastic resin.
The processing step then comprises a vacuum process operation that occurs simultaneously with a curing operation. Finally, it comprises a post-curing operation. The vacuum process supports the penetration of the resin in the material's pores. The curing process initiates the resin's polymerisation process. The post-curing process brings the resin to its maximum hardness.
Therefore, according to the first variant of the method, the initial part in a carbon-carbon composite material is first prepared by a pre-machining process, before being subjected to a process during which the carbon-carbon composite material is impregnated with a resin. Then the timepiece component is produced by machining the processed part to the required shapes.
The penetration of the resin in the carbon-carbon composite material increases the part's mechanical strength and sealing. It also improves its aesthetic aspect.
According to a second variant of the first aspect of the invention, the manufacturing method comprises a fine crushing step of said carbon-carbon composite material part, then a processing step of the resulting homogenate, and finally a moulding step of the homogenate subjected to the processing step.
The processing step comprises a resin casting operation that consists of pouring resin onto the carbon-carbon material homogenate and mixing them together. It also comprises an operation for heating up the mixture comprising the homogenate and the resin.
The moulding step comprises a filling operation of a mould having the definite shape of the required part with the mixture made up of the homogenate and resin, then a pressing operation, and finally a demoulding operation.
According to a characteristic of the second variant of the method, the heating up operation of the processing step and the pressing operation of the moulding step occur simultaneously and result in the polymerisation of the resin.
According to a characteristic of the second variant, the method comprises an optional operation of washing the homogenate fines, which precedes the processing step.
According to another characteristic of the second variant, the method comprises an optional operation of screening the homogenate fines, which precedes the processing step.
Therefore, according to the second variant of the method, the initial part in a carbon-carbon composite material is first prepared by crushing into fines, which are then subjected to a process during which the carbon-carbon composite material is impregnated with a resin. Then the timepiece component is produced by moulding the processed fines to the required shapes.
Whether it is for the first variant of the method or for the second variant of the method, the processing step comprises a resin casting step during which the carbon-carbon composite material is impregnated with a resin. With the first variant of the method, the carbon-carbon material is impregnated by penetration of the resin from a pre-machined face. With the second variant of the method, the carbon-carbon material is impregnated by mixing the resin with a carbon-carbon material homogenate. This impregnation advantageously improves the carbon-carbon material's properties, including its mechanical strength, its sealing, its resistance to UV rays, its aesthetics, its dermatological compatibility.
Preferably, the carbon-carbon composite part stems from a brake pad or disk of a racing vehicle or a brake disk of an airplane or a space shuttle tile.
The carbon-carbon composite material part may be a new part. Advantageously, the carbon-carbon composite material part is a used part. In this case, the method according to the invention contributes to meeting the ninth of the UN's seventeen sustainable development objectives.
According to a second aspect, the invention relates to a timepiece component produced by the method according to the first aspect of the invention.
The timepiece components according to the invention may be, in particular, cases, backs, middle cases, bezels, as well as dials, hands, strap links, whole straps, plates, bridges, including barrel bridges, gear train bridges, escapement bridges, pallet bridges, balance bridges, crowns.
The invention will be better understood upon reading the following detailed description of two special embodiments, provided for illustration purposes only and not restrictive, of a method according to the invention for manufacturing a timepiece component comprising a one-piece middle case and dial assembly, wherein:
The embodiment of the first variant of the method will be described in reference to
By first referring to
According to the invention, said initial part 100 is made up of carbon-carbon composite material.
In the example shown in the figures, said initial part 100 is a brake pad of a racing vehicle, comprising an active part 102 intended to be subjected to friction when the vehicle brakes, and a fastening part 104 intended to hold the brake pad in a calliper of the vehicle. Said active 102 and fastening 104 parts of part 100 were produced in one piece by milling a rough block in a carbon-carbon composite material.
As shown more specifically in
Machine tool 10 also comprises a plate 18 which will successively accommodate a base 24 of a first machining fixture 20 (
Said machining fixtures 20, 30, 40 are not only designed for the various machining steps, but also for the shape and dimensions of the parts machined during the various steps of the method, as well as for the shape and dimensions of the final timepiece component required.
First machining fixture 20, shown in
Base 24 is attached to plate 18 (
In operation, frame 22 is positioned on base 24 with a positioning cavity 26 materialised on said base 24 (
Frame 22 and base 24 are assembled to one another with cap screws 50, which cooperate with holes 60 of frame 22 and with bores 62 of base 24.
Frame 22 and base 24 are machined metal parts. For example frame 22 is made of steel and base 24 is made of aluminium. They are specially designed and sized to hold the part to be machined during the first machining step, second machining step and third machining step that will be described below.
The assembly comprising frame 22 and initial part 100 is then nested on base 24 and secured to it with screws 50, of which there are four in the illustrated example and are of the CHC M5 type for example.
Initial part 100 is fitted to first machining fixture 20. In the example illustrated, it is fitted so that, when machining on machine tool 10 (
Initial part 100 then undergoes a first machining step, shown in
The displacement settings of machining tool 16 are also configured to create on said blank 110:
Preferably, the raised section is between 0 millimetre and 1 millimetre. Even more preferably, said raised section measures 0.3 millimetre.
Preferably, the hollow section is between 0 millimetre and 0.2 millimetre. Even more preferably, said hollow section measures 0.1 millimetre.
Initial part 100 on which blank 110 was formed is now a first intermediate part 120 resulting from the first machining step, with pre-machined surfaces comprising many rough surfaces.
Said first intermediate part 120 is still secured to frame 22 of machining fixture 20 with set screws 52. Said frame 22 is disassembled from base 24 of machining fixture 20, said base 24 remaining attached to plate 18 of machine tool 10 with centring cavity 2.
First intermediate part 120 then undergoes a processing step, comprising a resin casting operation, then a vacuum process operation simultaneous with a curing operation, then a post-curing operation.
The resin casting operation is shown in
Resin 122 is an epoxy, thermosetting resin. In fact, epoxy resins have a good mechanical strength, compatible with the stresses that will be applied to the final timepiece component when in use. Epoxy resins also have a low shrinking level compared with other resins. Epoxy resins are also known for producing a better visual aspect of the final timepiece component, as they have a good resistance to UV rays, and because transparent epoxy resins are readily available.
Optionally, a coloured additive may be added to the thermosetting resin for decorative purposes.
The vacuum process operation is not shown in the figures. It involves installing frame 22, which holds first intermediate part 120 wherein resin 122 has been poured, in a sealed container and vacuumising said container. This process can last up to 24 hours, with a temperature between 20 and 25 degrees Celsius inside the container.
The vacuum process operation facilitates the penetration of resin 122 inside the carbon-carbon material, while eliminating any residual air bubbles inside said resin 122 after blank 110 has been filled.
The vacuum process operation is complemented with a curing operation, not shown in the figures, which can be performed in the open, with frame 22 being removed from the sealed container, or which can be performed under vacuum, with frame 22 remaining in the sealed container. According to the resin used and the hardness required for the final timepiece component to be produced, the curing operation can last between 3 and 24 hours, with a temperature of up to 150 degrees Celsius. The curing operation initiates the polymerisation of the resin.
The curing operation is followed by a post-curing operation, which brings resin 122 to its maximum hardness.
First intermediate part 120, wherein resin 122 was poured and then set during the processing step now makes up a second intermediate part 130.
Resin 122 has penetrated inside the carbon-carbon composite material. The penetration distance is at least 0.5 millimetre. The presence of resin 122 eliminates the rough surfaces generated by the first machining step and results in smoother surfaces, in particular at the second areas 114 and third areas 116 having a hollow section.
Frame 22 holding second intermediate part 130 is reassembled onto base 24, which has remained secured to plate 18 of machine tool 10. Frame 22 returns to its initial position on base 24 via positioning cavity 26.
A second machining step, similar to the first machining step, is then performed on second intermediate part 130.
Said second machining step comprises an actual machining process, by milling. It results in the removal of resin 122, poured into blank 110 and which has set during the processing step.
Machining tool 16 is now set up in order to eliminate first raised section areas 112, which had been left on blank 110 during the first machining step.
Machining tool 16 is also set up in order to make second hollow section areas 114 and third hollow section areas 116 level with the reference surface.
The second machining step leaves a residual coat of resin 122, which fills said second hollow section areas 114 and said third hollow section areas 116. Blank 110 now has an overall uniform surface, with some resin-coated zones 134, 136. These zones 134, 136 can be intended to come in contact with other parts, such as gasket surface zones 134 of the final timepiece component, for example. These zones can also be intended to become decorative zones 136 of the final timepiece component. In decorative zones 136, the thickness of the resin affects the opacity of the decoration. Coloured additives may also be added previously to resin 122 to contribute to the decorative effect.
The part produced during the second machining step is a third intermediate part 140, shown in
Third intermediate part 140 resulting from the second machining phase has the final dimensions and appearance of the upper face of a one-piece middle case and dial assembly.
It is still held on first machining fixture 20 fitted to plate 18 of machine tool 10, to undergo a third machining step involving a trimming operation, resulting in a fourth intermediate part 150, shown in
Fourth intermediate part 150 is then fitted to second machining fixture 30 for a fourth machining step intended to shape the underside of the final timepiece component.
Second machining fixture 30 is shown as an exploded view in
Second machining fixture 30 is part of a roughly parallelepiped block, one surface of which is hollowed out to define a counter-form 32 of fourth intermediate part 150, said counter-form 32 meeting very fine tolerances, of the order of a hundredth of a millimetre.
Second machining fixture 30 comprises two lateral blocks 36 separated by a longitudinal aperture 38 open on the face housing counter-form 32 and closed on the opposite face.
Second machining fixture 30 also comprises through holes 34, which run transversally through each one of the two lateral blocks 36. Said through holes 34 are designed to accommodate clamping devices 80, 82, 84 whose purpose, when in service, is to bring the two lateral blocks 36 noticeably closer to one another.
In the illustrated example, clamping devices 80, 82, 84 comprise clamping bolts 84, which cooperate with metal inserts 80, 82.
Preferably, second machining fixture 30 is made of a material that will not damage fourth intermediate part 150 during the clamping operation, in particular plastic material that can be, for example, plastic sold under the brand name Delrain®.
Second machining fixture 30 is secured to plate 18 (
Fourth intermediate part 150 is fitted to second machining fixture 30 being positioned in counter-form 32 of said second machining fixture 30, and being held with the highest precision between the two lateral blocks 36 of said second machining fixture 30, which are brought closer to one another with clamping devices 80, 82, 84 and thanks to the elasticity of the component material of said lateral blocks 36.
A fourth machining step is then carried out on fourth intermediate part 150, involving milling its second end face 154, which will become the underside of the final timepiece component.
Fourth intermediate part 150 whose second end face was machined is now a fifth intermediate part 160, fitted to third machining fixture 40 to undergo a fifth machining step, as shown in
Said third machining fixture 40 is secured to plate 18 of machine tool 10 with chassis elements 42, 44 (
Fifth intermediate part 160 is positioned on third machining fixture 40 thanks to the presence, on said third machining fixture 40, of a counter-form (not shown in the figures) of the lateral face of said fifth intermediate part 160 and by the actuation of a central screw, which opens said counter-form thanks to the elasticity of the material which the third machining fixture 40 is made of, namely aluminium in the illustrated example.
The fifth machining step involves performing finishings on fifth intermediate part 160, in order to obtain a final timepiece component 170. The finishings involve making decorations as well as cavities and other embossments intended to enable said timepiece component 170 to cooperate with other timepiece components at the time of their final assembly to form a watch.
In the example illustrated in
The method according to the first variant, shown in
The embodiment of the second variant of the method will now be described in reference to
According to this second variant, the manufacturing method according to the invention comprises a step for crushing an initial part in a carbon-carbon composite material.
The crushing step is shown in
Preferably, crushing machine 210 is set up so that the fines 220 produced by crushing have a predetermined maximum length, for example 2 millimetres. The size of the fines affects the quality of detail of the final timepiece component resulting from the second variant of the method.
The processing step comprises a resin casting operation and a heating up operation.
It is complemented by a moulding step comprising a pouring operation, a pressing operation and a demoulding operation.
The two processing and moulding steps are interlinked with the operations carried out in the following sequence:
The resin casting operation (not shown in the figures) involves mixing fines 220 resulting from crushing with a thermosetting resin. The selection criteria of said resin are the same as for the first variant of the method and will not be described a second time. An epoxy resin is preferred.
Optionally, the resulting mixture 240 can be enhanced with additives, for example precious metals or colourings.
The pouring operation, shown in
Mould 260 is shown as an exploded view in
Mould 260 comprises several elements 262, 264, 266, 268, of which there are four in the illustrated example. Each element 262, 264, 266, 268 is hollowed out with cavity sections 272, 274, 276, 278. More specifically, a lower element 262 bears a lower cavity section 272, an upper element 264 bears an upper cavity section 274, and two lateral elements 266, 268 each bear a lateral cavity section 276, 278.
Lower element 262 is assembled with the two lateral elements 266, 268, with cap screws 254, which enables the creation of cavity 250 wherein mixture 240 is poured (
In a manner which is per se known, upper element 268 has an air outlet 280 during the pressing operation, with a diameter defined so that the resin is not discharged along with the air.
The assembly of cavity sections 272, 274, 276, 278 makes up an entire mould cavity (not shown in the figures) having the definite design and dimensions of the required timepiece component.
Optionally, a stiffening insert (not shown in the figures) can be incorporated into cavity 250 of mould 260, to increase the strength and sealing of the final timepiece component produced by moulding. The stiffening insert may be made of metal, a composite, or any other appropriate material within the reach of the person skilled in the art.
Mixture 240 contained in the entire cavity then undergoes the pressing operation, during which it is compressed inside the closed mould (
Simultaneously with the pressing operation, the heating up operation is applied, which results in the polymerisation of the resin. It is performed by means of heating resistors (not shown in figures), which are inside holes 282 of lower element 262 of mould 260 (
The demoulding operation is shown in
The method according to the second variant comprises an optional fines washing step, not shown in the figures, which follows the fine crushing step of initial part 200, and which precedes the processing step. Washing can be done, for example, by spraying a detergent or by soaking the fines in a washing bath.
The washing step removes residue from the homogenate which could adversely affect the moulding, and which can come for example from grease coming into contact with the fines during the crushing operation. The detergent is selected for its ability to dissolve greases, and its evaporation ability. Acetone is preferred.
The method according to the second variant comprises an optional fines screening step, not shown in the figures, which follows the fine crushing step of the carbon-carbon composite part, and which precedes the processing step. The screening process can be done, for example by means of an AS 200 BASIC SIEVE machine.
The screening step results in removing the fines having a size greater than 2 millimetres, which could be present in the homogenate as well as impurities, which could potentially be in initial part 200, when said part is a used part.
In the example illustrated, final timepiece component 270, produced by the second variant of the method according to the invention, is a one-piece middle case and dial assembly.
According to the nature of the final timepiece component obtained after demoulding, a finishing step can be planned as an option. It may be manual if it involves removing resin residue or polishing or deburring the final timepiece component. It may consist of machining, similar to that of the fifth step of the first embodiment of the first variant of the method, if it involves creating decorations as well as cavities and other embossments intended to enable said timepiece component 170 to cooperate with other timepiece components at the time of their final assembly to form a watch.
The method according to the second variant, shown in
Number | Date | Country | Kind |
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1872697 | Dec 2018 | FR | national |
Filing Document | Filing Date | Country | Kind |
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PCT/FR2019/000207 | 12/10/2019 | WO | 00 |