WO2017097613A1

WO2017097613A1 - Method for making a carbon fibre watchcase and carbon watchcase obtained therefrom

Info

Publication number: WO2017097613A1
Application number: PCT/EP2016/078917
Authority: WO
Inventors: Beat FISCHLI; Karim GERBER
Original assignee: Oris Sa
Priority date: 2015-12-10
Filing date: 2016-11-25
Publication date: 2017-06-15
Also published as: CH711914B1; CH711914A2

Abstract

Method for making a carbon fibre watchcase comprising the steps of: a. forming an upper piece, a lower piece, two side pieces and an inner piece by moulding of carbon fibre prepregs between a forming tool and a complementary compressing counterpiece of a mould, the inner piece defining a central bore for the middle of the watchcase comprising a thread, and preferably a bezel, on an inner surface of the inner piece upon moulding said inner piece, and b. assembling the upper piece, the lower piece and the two side pieces about an outside surface of the inner piece with additional carbon fibre prepregs interfaced with said upper piece, lower piece, two side pieces and the inner piece and moulding additional carbon fibre prepregs to form a single moulded carbon fibre watchcase assembly. Carbon fibre watchcase comprising a middle having an integrally-formed inner thread, and preferably an integrally formed bezel.

Description

METHOD FOR MAKING A CARBON FIBRE WATCHCASE AND CARBON WATCHCASE OBTAINED THEREFROM Technical Field

[0001] The present invention relates to the field of watchmaking. In particular, it relates to a method for making a carbon fibre watchcase and a carbon watchcase obtained with that method. State of the art

[0002] Use of fibre reinforced materials to make watchcases and/or other consumer articles is very well known in the art. In particular, JP 60125583 A discloses a process for making parts of a watchcase from prepregs of fibre reinforced polymeric materials and watchcases including such reinforced parts. However, that document only teaches making of parts of watchcases and is silent about the making of a watchcase entirely made from carbon fibre material.

[0003] EP2805066 A2 further discloses a process for moulding articles of polymeric composite material having reinforcing fibres in a polymeric matrix material. Surface feature are created during heat moulding of the polymeric composite material to form the article and the surface features include the polymeric matrix material and the reinforcing fibres therein. The moulding process consists in placing the composite material in a mould and moulding the composite material using bladder inflation moulding to push the reinforcing fibres into the surface feature of a hardened part of a mould.

[0004] While bladder inflation moulding works very well for moulding polymeric materials into articles of simple, regular shapes, it is rather inappropriate for the moulding of articles of complex shapes integrally made of fibre reinforced materials as it cannot ensure simultaneous and homogenous application of pressure from the bladder on all sides and parts of the article to be moulded, such as shoulders, threads and horns in a watchcase, thereby creating parts of lesser mechanical resistance than others, which is unacceptable. [0005] An object of the invention is thus to overcome at least partially some of the above-mentioned drawbacks of the prior art, to achieve manufacturing of carbon fibre watchcases having identical shapes and features to metal-based watchcases, in particular having an integrally-formed thread in the middle of the watchcase without the need to have any metal insert to ensure watertight assembly of a case back onto the middle.

Disclosure of the invention

[0006] Accordingly, a first object of the invention relates to a method for manufacturing a carbon fibre watchcase comprising the steps of:

a. forming an upper piece, a lower piece, two side pieces and an inner piece by moulding of carbon fibre prepregs between a forming tool and a complementary compressing counterpiece of a mould for each piece, the inner piece defining a central bore for the middle of the watchcase comprising a thread, and preferably a bezel for supporting a glass, on an inner surface of the inner piece upon moulding thereof, and

b. assembling the upper piece, the lower piece and the two side pieces around an outside surface of the inner piece with additional carbon fibre prepregs interfaced with said upper piece, lower piece, two side pieces and the inner piece and moulding thereof to form a single moulded carbon fibre watchcase assembly.

[0007] The two-steps process of the invention is particularly advantageous in that it comprises moulding each part (or piece) of the watchcase individually from carbon fibre prepregs such that each of those parts has an optimum mechanical resistance thanks to optimal orientation of the reinforcing carbon fibres in each individual part, and also thanks to the relatively simple shape of each individual parts, which does not require complex moulds forms and therefore does not require machining of the parts for their assembly in the second step, neither for the later assembly of the watch elements into and onto the watchcase. Indeed the geometry of the individual pieces of the watchcase moulded in the first step of the process is essentially their final one, with little if any need for further refinement when mounting the watch elements into the watchcase.

[0008] Once the individual pieces of the watchcase are individually moulded they are further easier to assemble together in the second step with additional prepregs added at interfaces between the pieces to bond them together in the second moulding step. Again the final watchcase product obtained after the second moulding step requires little machining, with only the extra material to be trimmed-off at the joints between the individual pieces assembled together.

[0009] An integral carbon fibre material watchcase is hereby obtained using a very simple, yet efficient and cost effective process of manufacture.

[0010] According to the invention, in step a) the moulds are heated for at least about

30 min at a temperature of at least 130°C to allow the prepregs to cure.

[001 1] According to the invention, in step a) each of the upper piece, the lower piece, the two side pieces and the inner piece is formed individually in a bespoke mould by depositing and adjusting the prepregs on the forming tool and compressing it on said forming tool with the complementary compressing counterpiece during moulding.

[0012] According to the invention, in step a) a pressure of at least 5 bars is applied onto the prepregs and the forming tool by the complementary compressing counterpiece. It was found that such pressure helps to ensure proper curing and forming of the carbon fibre prepregs while avoiding formation of bubbles or wrinkles in the moulded individual pieces, which could alter the mechanical resistance of those pieces

[0013] Advantageously, in step a) the forming tool and the complementary compressing counterpiece of each mould is constrained with a jig. The use of a jig is particularly preferred to ensure application of a correct and constant pressure onto the prepregs in the moulds during the heating thereof.

[0014] According to the invention, the forming tool is made of heat-resistant material, preferably a metal or metallic alloy and, preferably, the complementary compressing counterpiece is made of silicon rubber. [0015] Advantageously, the pressure is applied onto the fornning tool and the prepregs by thermal expansion of the complementary compressing counterpiece during heating of the moulds.

[0016] It was found that silicone rubber counterpieces for the moulding of the individual part is particularly advantageous in that it homogenously expands upon heating in all dimensions of space, thereby applying a uniform pressure on the prepregs in the mould.

[0017] Advantageously, the forming tool of the mould for forming the inner piece comprises a cylindrical plug comprising a thread on an outside surface thereof, and preferably a shoulder for forming a bezel in said inner piece.

[0018] Advantageously, the complementary compressing counterpiece is removed from the forming tool between step a) and step b).

[0019] According to the invention, step b) comprises the following sub-steps :

- adjusting additional carbon fibre prepreg tape around the inner piece hold onto its forming tool, and

- inserting additional carbon fibre prepregs in recesses arranged therefor in the forming tool for the upper piece or the forming tool for the lower piece to form horns of the watchcase, and

- positioning and adjusting the forming tool of each mould bearing the individual upper piece, lower piece and side pieces moulded in step a) with respect to each other and around the forming tool of the inner piece such that said upper piece, lower piece and side pieces hold onto their forming tool interface with the additional carbon fibre prepregs on the inner piece and in the recesses, and

- holding all forming tools together with a jig, and

- heating the forming tools in the jig at a temperature of at least 130°C for at least 30 min to allow additional prepregs to cure and mould the individual upper piece, lower piece and side pieces and inner piece together to form a single moulded carbon fibre watchcase assembly.

[0020] Advantageously, the subs-step consisting in inserting additional carbon fibre prepregs in recesses comprises, for each recess: - cutting individual prepreg pieces and adhering it onto each other to form a prepregs stack having a first and a second end, and

- inserting a first end of the prepregs stack into the recess such that said end faces the inner piece, and

- folding the prepregs stack onto itself such that the second end thereof also faces the inner piece and the fold faces outwards.

[0021] Advantageously, after moulding the jig and the forming tools are removed from the single moulded carbon fibre watchcase assembly.

[0022] Advantageously, after step b) excess material from the moulded single carbon fibre watchcase assembly is trimmed off and the horns pierced to form through holes adapted for receiving a bar for fixing a wrist band to the watchcase.

[0023] A second object of the invention relates to a carbon fibre watchcase comprising a middle having an integrally-formed inner thread, and preferably also a bezel.

[0024] Advantageously, the carbon fibre watchcase of the invention further comprises horns extending outwardly from the middle and integral therewith, the horns comprising through holes adapted for receiving a bar for fixing a wrist band to the watchcase.

Brief description of the drawings

[0025] Further details of the invention will now be described with respect to the figures, in which:

Figure 1 illustrates a watchcase according to the invention in a perspective view,

Figures 2 to 4 illustrate respectively a right side view, a top side view and a bottom side view of the watchcase of the invention as represented in Figure 1 ,

Figure 5A and 5B illustrate mould for making side pieces of a watchcase according to the process of the invention;

Figure 6 illustrates a moulds for making an upper piece of a watchcase according to the process of the invention; Figure 7 illustrates a mould for making a bottom piece of a watchcase according to the process of the invention;

Figure 8 illustrates a mould for making an inner piece of a watchcase according to the process of the invention;

- Figure 9 illustrates preparation steps before a second moulding step of a watchcase according to the process of the invention;

Figure 10 and 1 1 illustrate respectively a mould as used for a second moulding step of a watchcase according to the process of the invention.

Embodiments of the invention

[0026] The present invention proposes a new process for manufacturing a unitary watchcase 1 such as represented in Figure 1 , which is made integrally of heat moulded composite material, especially of pre-impregnated sheets of carbon fibres impregnated with epoxy resin, commonly called prepreg (singular) or prepregs (plural) throughout the present specification.

[0027] The watchcase 1 of the invention comprises, as represented in Figures 1 , 3 and 4 in particular, a substantially tubular middle 2 of circular section comprising on a top inner face a bezel 21 and on a bottom inner face a thread 22, respectively for adjusting and assembling in a substantially waterproof and pressure-resistant manner a glass and a case back of a timepiece, not represented in the figures. The watchcase 1 further comprises on its outer surface and extending outwardly on opposite sides two pairs of horns 3 for fixing a wristband by means of bars (not represented) inserted into holes 4 pierced throughout the ends of the horns 3 as seen in Figure 1 and 2 in particular.

[0028] Finally, as seen on Figure 1 and 2, the middle 2 of the watchcase 1 preferably comprises one or several recesses 5 and through holes 6 machined on at least one side of the middle 2 between opposite horns 3 to allow insertion and positioning of push buttons and other time-setting organs for the timepiece.

[0029] According to the invention, the watchcase 1 is integrally formed of carbon fibre reinforced composite material, with the thread 22 and the bezel 21 in the inner side face of the nniddle 2 being integrally formed in the composite material upon heat moulding of said composite material and without any machining. Such integral forming of the bezel 21 and thread 22 provides a very precise geometry for the middle 2 in a repeatable way and at very low cost due to the absence of required machining after moulding. This is further advantageous for the later assembly of a glass and case back for construction of a timepiece using the watchcase 1 of the invention as those can be fitted to the watchcase 1 using standard joints and without any intermediate metallic adjusting pieces or rings, thereby providing excellent waterproofness and pressure resistance.

[0030] The watchcase 1 of the invention is manufactured following a 2-steps process described herein after with reference to figures 5 to 1 1.

[0031] The method according to the invention essentially comprises the steps of:

a. forming an upper piece 1 1 , a lower piece 12, two side pieces 13, 14 and an inner piece 15 by moulding of carbon fibre prepregs between a forming tool T1 , T2, T3, T4, T5 and a complementary compressing counterpiece C1 , C2, C3, C4, C5 of a bespoke mould M1 , M2, M3, M4, M5 for each of the individual pieces 1 1 , 12, 13, 14, 15, the inner piece 15 defining a central bore for the middle of the watchcase comprising a thread and preferably a shoulder on an inner surface of the inner piece upon moulding thereof, and

b. assembling the upper piece, the lower piece and the two side pieces about an outside surface of the inner piece with additional carbon fibre prepregs interfaced with said upper piece, lower piece, two side pieces and the inner piece and moulding thereof to form a single moulded carbon fibre watchcase assembly.

[0032] In the first step a) elementary parts or pieces are made according to the invention from components 7, 8, 9, 10 of composite material made of pre- impregnated carbon fibres impregnated with reactive epoxy resin, commonly called "prepreg(s)", which are cut to an appropriate shape determined by the shape of the watchcase 1 to be manufactured from the sheets and/or strips of prepreg material. Examples of appropriate prepregs for carrying out the invention are available commercially from German manufacturer Krempel- Group under reference KGBX 0909 or from German manufacturer SGL Group under the reference SIGRAPREG® C W200-Tw2/2E323 - 45%.

[0033] The cut prepreg components 7, 8, 9, 10 are arranged on a corresponding forming tool T1 , T2, T3, T4, T5 of the moulds and covered with a respective compressing counterpiece C1 , C2, C3, C4, C5 of complementary shape of the corresponding forming tool and adapted for homogeneously pressing prepreg components 7, 8, 9, 10 onto the forming tool T1 , T2, T3, T4, T5 during the first moulding step of the inventive process.

[0034] The shape of the upper piece 1 1 , the lower piece 12 and the two side pieces 13, 14 is determined by the watch manufacturer depending on the design of the watchcase 1 chosen. Therefore the corresponding moulds M1 , M2 M3 and M4 and in particular the forming tool T1 , T2, T3, T4 thereof may vary significantly and must be adapted to the watchcase 1 design. Quite oppositely the inner piece 15 can vary in dimensions but must generally remain shape-wise standard as a substantially tubular piece defining a central bore for the middle 2 of the watchcase comprising at least a thread on a bottom inner surface obtained upon moulding thereof, and at least a shoulder on a substantially top inner surface for forming a bezel 21 of the middle 2. To allow that formation of bezel 21 and thread 22 in the inner piece 15 the forming tool T5 comprises a cylindrical plug comprising a thread on an outside surface thereof and a shoulder about which prepreg tape material 10 is wound to form the inner piece 15.

[0035] The forming tools T1 , T2, T3, T4, T5 of the moulds M1 , M2, M3, M4, M5 are preferably made of a heat-resistant, hard metallic material such as stainless steel cast and machined to comprise a moulding form to the specific shape of the piece 1 1 , 12, 13, 14, 15 of the watchcase 1 to which moulding it is dedicated. The compressing counterpieces C1 , C2, C3, C4, C5 of each mould M1 , M2, M3, M4, M5 are made of a substantially soft, deformable and expandable material such as silicon rubber, a preferable material being for example marketed under the name Neukasil RTV 20, from German manufacturer Altropol Kunststoff GmbH. [0036] Once the prepregs components 7, 8, 9, 10 are deposited onto the forming tool T1 , 12, T3, T4, T5 of each of the individual moulds M1 , M2, M3, M4, M5 they are covered with a soft protection foil (not represented on the figures for clarity purpose) and pressed against the forming tool by means of the corresponding complementary compressing counterpiece C1 , C2, C3, C4,

C5. Finally, each of the moulds M1 , M2, M3, M4, M5 is locked using a jig, also not represented on the figures, adapted to constrain the counterpiece C1 , C2, C3, C4, C5 onto the forming tool T1 , T2, T3, T4, T5 of the moulds M1 , M2, M3, M4, M5 to ensure proper compression on the prepreg components 7, 8, 9, 10 through expansion of the counterpieces material during heat moulding.

[0037] When all individual moulds M1 , M2, M3, M4, M5 are locked into their jig, they are then baked at a temperature of at least 130° C for at least 30 minutes to allow the resin of the prepreg components to cure and harden to the shape given by the respective moulds M1 , M2, M3, M4, M5. Preferably the baking of the prepregs / heating of the moulds is carried out using infrared heating, which allows an homogenous distribution of heat in the moulds, both in the forming tool and the compressing counterpieces.

[0038] After baking the moulds M1 , M2, M3, M4, M5 and their jig(s) are allowed to cool down to room temperature and then the counterpiece C1 , C2, C3, C4,

C5 of each mould is removed from the forming tool T1 , T2, T3, T4, T5, as well as the protecting foil from the now moulded carbon fibres reinforced piece 1 1 , 12, 13, 14, 15 of composite material, which rests on the forming tool.

[0039] At this stage the moulded pieces 1 1 , 12, 13, 14, 15 of composite material are then prepared for the second and final moulding step without removing them from the forming tools T1 , 12, 13, 14, 15 of the individual moulds M1 , M2, M3, M4, M5 nor machining to trim excess material off from the moulded pieces.

[0040] Preparation for the second moulding step b) comprises several sub-steps, a first one of which consisting in depositing and arranging additional prepreg components over parts of the moulded pieces1 1 , 12, 13, 14, 15 so as to provide bonding and linking material of identical material as the one of the moulded pieces themselves to allow assembly thereof in the second moulding step of the process of the invention.

[0041] As represented in figure 9, at least one additional prepreg 16 is added specifically about the circumference of the inner piece 15 moulded onto the forming tool T5 of mould M5 in order to allow joining the upper, lower and side pieces 1 1 , 12, 13, 14 onto the inner piece 15 in the second moulding step to form the middle 2 of the watchcase 1.

[0042] Further, in a second sub-step specially prepared prepreg components 17 are inserted in recesses 18 arranged to that aim onto the forming tool T1 for the upper piece 1 1 and/or the forming tool T2 for the lower piece 12 for the formation of the horns 3 of the watchcase 1 onto the middle 2 in the second moulding step. These prepreg components 17 act to help bond the various parts of the watchcase together, and also as filler material so as to not leave cavities in the structure. However, if desired, cavities can be left in the structure of the watchcase.

[0043] The specially prepared prepreg components 17 are advantageously formed of multiple prepregs stacked onto each other, preferably between about 5 to 15 pieces of prepregs depending on the shape of the watchcase 1 and its horns. These layered prepreg components 17 have a substantially rectangular shape and they are inserted in the recesses 18 such that a first end is brought into abutment against the inner piece 15 and the second end is then folded over that first end into abutment with the inner piece 15 too such that a fold 19 extends outwardly from the inner piece 15 in between the two ends of the layered prepregs 17.

[0044] This particular arrangement of the layered prepregs 17 aims at providing traction resistant horns 3 integrally made in composite material and anchored on the middle 2 of the watchcase 1. More specifically, the prepreg components 17 are assembled such that the carbon fibres in each layer thereof extend in the longitudinal direction of the components 17. This orientation of the fibres in the prepreg components 17 result in the fibres forming a loop or fold along the whole length of the horns 3, starting from the middle at one end of the prepregs 17 and back to the middle at the other end of the prepregs 17. This folded orientation of the fibres in the horns 3 helps significantly resistance of the horns 3 to traction forces at their free ends where the bars for fixing a wristband are inserted in holes 4 as represented in figures 1 and 2. Indeed, experiments have shown that it is not necessary to provide metal bushings in holes 4, since the composite material has sufficient mechanical resistance to allow direct interaction with the ends of the bars.

[0045] As can be seen from Figure 9 too, the additional prepregs 17 are positioned in the recesses18 of the forming tool T1 when the forming tool T5 of the mould M5 for the inner piece 15 with said inner piece 15 thereon inserted into a corresponding through hole arranged in said forming tool T1 to that effect as will be better understood below from the description of the second moulding step of the process of the invention.

[0046] With the additional prepregs 16, 17 in place as described above the second moulding step b) of the process of the invention then comprises in a third sub-step assembling the upper piece 1 1 , the lower piece 12 and the two side pieces 13, 14 about an outside surface of the inner piece 15 by means of the additional prepregs 16, 17 in a modular mould M6.

[0047] The modular mould M6 is formed by positioning and adjusting the forming tools T1 , T2, T3, T4 used in the first step a) with the corresponding individual pieces 1 1 , 12, 13, 14 thereon with respect to each other and around the forming tool T5 of the inner piece 15 such that said upper piece 1 1 , lower piece 12 and side pieces 13, 14 hold onto their forming tool T1 , T2, T3, T4 interface with the additional carbon fibre prepregs 16, 17 on the inner piece 15 and in the recesses of forming tool T1.

[0048] Once this is done all forming tools are held against each other in position together with a further jig, represented by means of arrows F on figure 10 and 1 1.

[0049] Then the mould M6 in the jig is heated at a temperature of at least 130°C for at least 30 min to allow additional prepregs 16, 17 to cure and mould the individual upper piece1 1 , lower piece 12 and side pieces 13, 14 and inner piece 15 together to form a single moulded carbon fibre watchcase assembly.

[0050] Preferably, this second heat moulding step is carried out using a different heating technique than the infrared heating of the first step a) as the mould M6 is wholly formed of heat resistant steel of the individual forming tools. It is therefore preferred to use induction heating to achieve this final moulding of the watchcase assembly.

[0051] After the second moulding step b) the jig and the forming tools T1 , T2, T3, T4 and T5 are allowed to cool to room temperature and then removed from the single moulded carbon fibre watchcase assembly thereby obtained

[0052] It is only needed to remove any excess material from the moulded single carbon fibre watchcase assembly by trimming off that excess material and then finishing the watchcase 1 by delimiting the horns 3 and forming through holes 4 therein and also machining for instance the pushbutton recesses 5 and corresponding holes 6. However those last two finishing steps do not need being carried out right after moulding but can be completed any time later, in particular upon mounting and assembly of a full watch/timepiece.

[0053] The above description has been made with reference to a particular example of a watchcase 1 integrally made of carbon fibre composite material according to the process herein described. However, obvious amendments to the shape of the watchcase of the way to achieve any of the moulding steps may be arranged by skilled person without departing from the scope of the invention.

Claims

Method for manufacturing a carbon fibre watchcase (1 ) comprising the steps of: a. forming an upper piece (1 1 ), a lower piece (12), two side pieces (13, 14) and an inner piece (15) by moulding of carbon fibre prepregs (7, 8, 9, 10) between a forming tool (T1 , T2, T3, T4, T5) and a complementary compressing counterpiece (C1 , C2, C3, C4, C5) of a mould (M1 , M2, M3, M4, M5) for each piece, the inner piece (15) defining a central bore for the middle (2) of the watchcase comprising a thread (22), and preferably a bezel (21 ) for supporting a glass, on an inner surface of the inner piece upon moulding thereof, and

b. assembling the upper piece, the lower piece and the two side pieces around an outside surface of the inner piece with additional carbon fibre prepregs (16, 17) interfaced with said upper piece, lower piece, two side pieces and the inner piece and moulding thereof to form a single moulded carbon fibre watchcase assembly.

Method according to claim 1 , wherein in step a) the moulds are heated for at least about 30 min at a temperature of at least 130°C to allow the prepregs to cure.

Method according to claim 1 or 2, wherein in step a) each of the upper piece, the lower piece, the two side pieces and the inner piece is formed individually in a bespoke mould by depositing and adjusting the prepregs on the forming tool and compressing it on said forming tool with the complementary compressing counterpiece during moulding.

4. Method according to any of claims 1 to 3, wherein in step a) a pressure of at least 5 bars is applied onto the prepregs and the forming tool by the complementary compressing counterpiece.

5. Method according to any of claims 1 to 4, wherein in step a) the fornning tool and the complementary compressing counterpiece of each mould is constrained with a jig.

6. Method according to any of claims 1 to 5, wherein the forming tool is made of heat-resistant material, preferably a metal or metallic alloy.

7. Method according to any of claims 1 to 6, wherein the complementary compressing counterpiece is made of silicon rubber.

8. Method according to claims 4 and 7, wherein the pressure is applied onto the forming tool and the prepregs by thermal expansion of the complementary compressing counterpiece during heating of the moulds.

9. Method according to any of claims 1 to 8, wherein the forming tool of the mould for forming the inner piece comprises a cylindrical plug comprising a thread on an outside surface thereof.

10. Method according to any of claims 1 to 9, wherein the complementary compressing counterpiece is removed from the forming tool between step a) and step b).

1 1. Method according to any preceding claim, wherein step b) comprises the following sub-steps:

- adjusting additional carbon fibre prepreg tape (16) around the inner piece hold onto its forming tool, and

- inserting additional carbon fibre prepregs (17) in recesses (18) arranged therefor in the forming tool (T1 ) for the upper piece or the forming tool for the lower piece (T2) to form horns of the watchcase, and

- positioning and adjusting the forming tool of each mould bearing the individual upper piece, lower piece and side pieces moulded in step a) with respect to each other (T1 , T2, T3, T4) and around the forming tool (T5) of the inner piece (15) such that said upper piece, lower piece and side pieces hold onto their forming tool interface with the additional carbon fibre prepregs on the inner piece and in the recesses, and

- holding all forming tools together with a jig, and

12. Method according to claim 1 1 , wherein the sub-step consisting in inserting additional carbon fibre prepregs (17) in recesses (18) comprises, for each recess:

- cutting individual prepreg pieces and stacking it onto each other to form a prepregs component (17) having a first and a second end, and

- inserting a first end of the prepregs component (17) into the recess (18) such that said end faces the inner piece (15), and

- folding the prepregs component (17) onto itself such that the second end thereof also faces the inner piece (15) and the fold faces outwards.

13. Method according to any of claims 1 1 or 12, wherein after moulding the jig and the forming tools are removed from the single moulded carbon fibre watchcase assembly.

14. Method according to any of claims 1 to 13, wherein after step b) excess material from the moulded single carbon fibre watchcase assembly is trimmed off and the horns (3) pierced to form through holes (4) adapted for receiving a bar for fixing a wrist band to the watchcase.

15. A carbon fibre watchcase (1 ) comprising a middle (2) having an integrally-formed inner thread (22), and preferably a bezel (21 ).

16. A carbon fibre watchcase according to claim 15, further comprising horns (3) extending outwardly from the middle (2) and integral therewith, the horns comprising through holes (4) adapted for receiving a bar for fixing a wrist band to the watchcase.