CH711914B1 - Method for manufacturing a carbon fiber watch case and carbon fiber watch case obtained by this method. - Google Patents

Abstract

The present invention relates to a method for manufacturing a carbon fiber watch case comprising the steps: a) of forming an upper part, a lower part, two lateral parts and an internal part (15) in molding carbon fiber prepreg components (10) between a forming tool (T5) and a compression counterpart (C5) complementary to a mold, the internal part (15) defining a central bore for the middle part of the case watch comprising a thread, and preferably a bezel, on an internal surface (15) of the internal part during the molding of the latter, and b) assembling the upper part, the lower part and the two parts lateral around an external surface of the internal part (15) with prepregs of additional carbon fibers interfaces with said upper part, lower part, two lateral parts and the internal part (15) and m or bonding these to form a single molded carbon fiber watch case. The invention also relates to a carbon fiber watch case comprising a middle part comprising an internal thread formed in one piece, and preferably a bezel formed in one piece.

Description

Technical area

The present invention relates to the field of watchmaking. In particular, it relates to a method for manufacturing a carbon fiber watch case and a carbon fiber watch case obtained with this method.

State of the art

The use of fiber-reinforced materials to make watch cases and / or other consumer items is very well known in the art. In particular, document JPS 60 125 583 A presents a method for manufacturing parts of a watch case from prepregs of fiber-reinforced polymeric materials and watch cases comprising these reinforced parts. However, this document teaches only the making of watch case parts and says nothing about the making of a watch case made entirely from carbon fiber material.

Document EP 2 805 066 A2 further presents a method for molding articles of polymeric composite material comprising reinforcing fibers in a polymeric matrix material. Surface features are created during hot molding of the polymeric composite material to form the article and surface features include the polymeric matrix material and the reinforcing fibers therein. The molding process involves placing the composite material in a mold and molding the composite material using bladder inflation molding to push the reinforcing fibers into the surface characteristic of a cured part of a mold.

Although bladder inflation molding works very well for molding polymeric materials into articles of simple, regular shapes, it is rather unsuitable for molding articles of complex shapes made entirely of fiber reinforced materials given that it cannot guarantee the simultaneous and uniform application of pressure from the bladder on all sides and all parts of the article to be molded, such as the shoulders, threads and horns in a housing watch, thereby creating parts of lower mechanical strength than the others, which is unacceptable.

An object of the invention is thus to at least partially overcome some of the drawbacks mentioned above of the prior art, in order to obtain the manufacture of watch cases made of carbon fibers having shapes and characteristics identical to those metal-based watch cases, in particular having a thread formed integrally in the middle of the watch case without the need to have any metal insert to guarantee the watertight assembly of a case back on the build.

Presentation of the invention

Therefore, a first object of the invention relates to a method for manufacturing a carbon fiber watch case comprising the steps:

A. for forming an upper part, a lower part, two lateral parts and an internal part by molding carbon fiber prepreg components between a forming tool and a complementary compression counterpart of a mold for each part, the internal part defining a central bore for the middle part of the watch case comprising a thread, and preferably a bezel for supporting a glass, on an internal surface of the internal part during the molding of the latter, and

B. assembly of the upper part, the lower part and the two lateral parts around an external surface of the internal part with prepreg components of additional carbon fibers interfaces with said upper part, lower part, two lateral parts and the internal part and molding thereof to form a single molded carbon fiber watch case.

The two-step process according to the invention is particularly advantageous in that it comprises the molding of each part (or part) of the watch case individually from components prepreg of carbon fibers so that each of these parts has optimum mechanical resistance thanks to the optimal orientation of the reinforcing carbon fibers in each individual part, and also thanks to the relatively simple shape of each individual part, which does not require complex mold shapes and, therefore, does not require the machining of the parts for their assembly in the second step, nor for the subsequent assembly of the watch elements in and on the watch case. Indeed, the geometry of the individual parts of the watch case molded in the first step of the process is essentially their final geometry, with little need, if any, for further improvement when mounting the watch elements in the watch case. watch.

Once the individual parts of the watch case are molded individually, they are even easier to assemble to each other in the second step with additional prepreg components added at the interfaces between the parts to link them together to others in the second stage of molding. Again, the final watch case product obtained after the second molding step requires little machining, only the excess material to be removed at the joints between the individual parts assembled with each other.

A watch case made of integral carbon fiber material is thus obtained using a very simple manufacturing process, although it is efficient and profitable.

According to the invention, in step a) the molds are heated for at least about 30 minutes at a temperature of at least 130 ° C to allow the prepreg components to harden.

According to the invention, in step a) each of the upper part, the lower part, the two lateral parts and the internal part is formed individually in a custom mold by depositing and adjusting the prepreg components on the forming tool and compressing them on said forming tool with the additional compression counterpiece during molding.

According to the invention, in step a) a pressure of at least 5 bars is applied to the prepreg components and the forming tool by the complementary compression counter-piece. This pressure has been found to help ensure proper hardening and shaping of carbon fiber prepreg components while preventing bubbles or wrinkles in individual molded parts, which could affect the mechanical strength of these parts. .

Advantageously, in step a) the forming tool and the complementary compression counter-piece of each mold are constrained by an assembly.

The use of an assembly is particularly preferred to guarantee the application of correct and constant pressure on the prepreg components in the molds during their heating.

According to the invention, the forming tool is made of a heat-resistant material, preferably a metal or a metal alloy and, preferably, the complementary compression counter-piece is made of silicone rubber. .

Advantageously, the pressure is applied to the forming tool and the prepreg components by the thermal expansion of the additional compression counterpart during the heating of the molds.

It has been found that the silicone rubber counterpieces for molding the individual part are particularly advantageous in that they extend homogeneously during heating in all the dimensions of the space, thereby applying uniform pressure to the prepreg components in the mold.

Advantageously, the mold forming tool for forming the internal part comprises a cylindrical shutter comprising a thread on an external surface thereof, and preferably a shoulder to form a bezel in said internal part.

Advantageously, the complementary compression counter-piece is removed from the forming tool between step a) and step b).

According to the invention, step b) comprises the following substeps: fitting a strip of components pre-impregnated with carbon fibers around the internal part held on its forming tool, and inserting prepreg components of additional carbon fibers into the recesses arranged for this purpose in the forming tool for the upper part or in the forming tool for the lower part to form the horns of the watch case, and for positioning and adjusting the forming tools of each mold supporting the upper part, the lower part and the individual lateral parts molded in step a) relative to each other and around the tool for forming the part internal so that said upper part, lower part and lateral parts held on their forming tool interface with the prepreg components of additional carbon fibers on the internal part and in the recesses, and holding all the forming tools together by mounting, and heating the forming tools in the assembly to a temperature of at least 130 ° C for at least 30 min to allow the additional prepreg components to harden and mold the upper part, the lower part and the individual side parts and the part internally together to form a single molded carbon fiber watch case.

Advantageously, the sub-steps consisting in the insertion of prepreg components of additional carbon fibers in the recesses include, for each recess: cutting the individual prepreg components and gluing them on top of each other to form a stack of prepreg components having a first and a second end, and the insertion of a first end of the stack of prepreg components into the recess so that said end is oriented towards the internal part, and folding the stack of prepreg components on itself so that the second end of the latter is also oriented towards the internal part and the fold is oriented towards the outside.

Advantageously, after molding, the assembly and the forming tools are removed from the watch case made of single molded carbon fibers.

Advantageously, after step b) the excess material of the single molded carbon fiber watch case is removed and the horns are drilled to form through holes designed to receive a bar for attaching a bracelet to the case of watch.

A second object of the invention relates to a carbon fiber watch case comprising a middle part comprising an internal thread formed in one piece, and preferably also a bezel.

Advantageously, the carbon fiber watch case according to the invention further comprises horns extending outside from the middle part and in one piece with the latter, the horns comprising through holes designed to receive a bar for attaching a strap to the watch case.

Brief description of the drawings

Other details of the invention will now be described in relation to the figures, in which: <tb> fig. 1 <SEP> illustrates a watch case according to the invention in perspective view; <tb> fig. 2 to 4 <SEP> respectively illustrate a view from the right side, a view from above and a view from below of the watch case according to the invention as shown in FIG. 1; <tb> fig. 5A and 5B <SEP> illustrate a mold for manufacturing the lateral parts of the watch case by the method according to the invention; <tb> fig. 6 <SEP> illustrates a mold for manufacturing an upper part of the watch case by the method according to the invention; <tb> fig. 7 <SEP> illustrates a mold for manufacturing a lower part of the watch case by the method according to the invention; <tb> fig. 8 <SEP> illustrates a mold for manufacturing an internal part of the watch case by the method according to the invention; <tb> fig. 9 <SEP> illustrates the preparation steps before a second step of molding the watch case by the method according to the invention; <tb> fig. 10 and 11 <SEP> respectively illustrate a mold as used for a second step of molding the watch case by the method according to the invention.

Modes of Carrying Out the Invention

The present invention provides a new method for manufacturing a unitary watch case 1 as shown in FIG. 1, which is made entirely of a heat-molded composite material, particularly of sheets prepreg of carbon fibers impregnated with an epoxy resin, commonly called prepreg component (singular) or prepreg components (plural) throughout description.

The watch case 1 according to the invention comprises, as shown in Figs. 1, 3 and 4 in particular, a substantially tubular middle part 2 of circular section comprising, on an upper internal face, a bezel 21, and on a lower internal face, a thread 22, respectively for adjusting and assembling in a substantially sealed manner water and pressure resistant, a glass and a case back of a watch, not shown in the figures. The watch case 1 further comprises, on its external surface and extending outside on the opposite sides, two pairs of horns 3 for fixing a strap by means of bars (not shown) inserted in holes 4 drilled at through the ends of the horns 3 as shown in figs. 1 and 2 in particular.

Finally, as shown in figs. 1 and 2, the middle part 2 of the watch case 1 preferably comprises one or more recesses 5 and through holes 6 machined on at least one side of the middle part 2 between the horns 3 opposite to allow the insertion and positioning of buttons- pushers and other time setting devices for the watch.

According to the invention, the watch case 1 is made entirely of a composite material reinforced with carbon fibers, with the thread 22 and the bezel 21 in the internal lateral face of the middle part 2 formed entirely of the material composite during hot molding of said composite material and without any machining. This integral formation of the bezel 21 and the thread 22 provides a very precise geometry for the middle part 2 in a repeatable manner and at a very low cost due to the absence of machining required after molding. This is also advantageous for the subsequent assembly of a glass and a case back for the construction of a watch using the watch case 1 according to the invention since these can be mounted on the watch case 1 using standard seals and without metal parts or intermediate adjustment rings, thereby ensuring excellent water resistance and pressure resistance.

The watch case 1 according to the invention is manufactured according to a 2-step process described below with reference to figs. 5 to 11.

The method according to the invention essentially comprises the steps:

A. for forming an upper part 11, a lower part 12, two lateral parts 13, 14 and an internal part 15 by molding components prepreg of carbon fibers between a forming tool T1, T2, T3 , T4, T5 and a complementary compression counterpart C1, C2, C3, C4, C5 of a custom mold M1, M2, M3, M4, M5 for each of the individual pieces 11, 12, 13, 14, 15 , the internal part 15 defining a central bore for the middle part of the watch case comprising a thread and preferably a shoulder on an internal surface of the internal part during the molding of the latter, and

B. assembly of the upper part, the lower part and the two lateral parts around an external surface of the internal part with prepreg components of additional carbon fibers interfaces with said upper part, lower part, two lateral parts and the internal part and molding thereof to form a single molded carbon fiber watch case.

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

The prepreg components 7, 8, 9, 10 cut are arranged on the forming tool T1, T2, T3, T4, T5 corresponding to the molds and covered with the compression counterpart C1, C2, C3, C4 , C5 respective to the form complementary to the corresponding forming tool and designed to uniformly press the prepreg components 7, 8, 9, 10 on the forming tool T1, T2, T3, T4, T5 during the first step molding process according to the invention.

The shape of the upper part 11, the lower part 12 and the two side parts 13, 14 is determined by the watch manufacturer according to the design of the watch case 1 chosen. Consequently, the corresponding molds M1, M2, M3 and M4 and in particular the forming tool T1, T2, T3, T4 thereof can vary significantly and must be adapted to the design of watch case 1. Quite in contrast, the dimensions of the internal part 15 can vary, but it must generally remain standard in terms of shape as a substantially tubular part defining a central bore for the middle part 2 of the watch case comprising at at least one thread on a lower internal surface obtained during molding thereof, and at least one shoulder on a substantially upper internal surface to form a bezel 21 of the middle part 2. To allow this formation of the bezel 21 and of the net 22 in the internal part 15, the forming tool T5 comprises a cylindrical obturator comprising a thread on an outer surface thereof and a shoulder around which the strip material of c prepreg components 10 is wound to form the internal part 15.

The forming tools T1, T2, T3, T4, T5 of the molds M1, M2, M3, M4, M5 are preferably made of a hard heat-resistant metallic material such as cast stainless steel and machined so as to include a form of molding in the specific shape of the part 11, 12, 13, 14, 15 of the watch case 1 for the molding of which it is dedicated. The compression counterparts C1, C2, C3, C4, C5 of each mold M1, M2, M3, M4, M5 are made of a substantially soft, deformable and expandable material such as silicone rubber, a preferable material being preferably marketed under the name Neukasil RTV 20, by the German manufacturer Altropol Kunststoff GmbH.

Once the prepreg components 7, 8, 9, 10 are deposited on the forming tool T1, T2, T3, T4, T5 of each of the individual molds M1, M2, M3, M4, M5, they are covered with a flexible protective sheet (not shown in the figures for clarity) and pressed against the forming tool by means of the complementary compression counterpart C1, C2, C3, C4, C5 corresponding. Finally, each of the molds M1, M2, M3, M4, M5 is locked using a mounting, which is not shown either in the figures, designed to constrain the counterpiece C1, C2, C3, C4, C5 on the forming tool T1, T2, T3, T4, T5 of the molds M1, M2, M3, M4, M5 to guarantee correct compression on the prepreg components 7, 8, 9, 10 by the expansion of the material of the counterparts during hot molding.

When all the individual molds M1, M2, M3, M4, M5 are locked in their assembly, 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 bake and harden in the form given by the respective molds M1, M2, M3, M4, M5. Preferably, the baking of the prepreg components / the heating of the molds is carried out using infrared heating, which allows a homogeneous distribution of the heat in the molds, both in the forming tool and in the counter parts of compression.

After cooking, the molds M1, M2, M3, M4, M5 and their assemblies are left to cool to room temperature and then the counterpiece C1, C2, C3, C4, C5 of each mold is removed from the forming tool T1, T2, T3, T4, T5 as well as the protective sheet of the part reinforced with carbon fibers now molded 11, 12, 13, 14, 15 in composite material, which rests on the tool forming.

At this point, the molded parts 11, 12, 13, 14, 15 made of composite material are then prepared for the second and last molding step without removing them from the forming tools T1, T2, T3, T4, T5 of the molds M1, M2, M3, M4, M5 individual and without machining to remove excess material from the molded parts.

The preparation for the second molding step b) comprises several sub-steps, a first of them consisting in the deposition and arrangement of additional prepreg components on parts of the molded parts 11, 12, 13, 14 , 15 so as to provide a bonding material identical to that of the molded parts themselves to allow their assembly in the second molding step of the method according to the invention.

As shown in FIG. 9, at least one additional prepreg 16 is added specifically around the circumference of the internal part 15 molded on the forming tool T5 of the mold M5 in order to allow the assembly of the upper, lower and lateral parts 11, 12, 13, 14 on the internal part 15 in the second molding step to form the middle part 2 of the watch case 1.

In addition, in a second substep, specially prepared prepreg components 17 are inserted into recesses 18 arranged for this purpose on the forming tool T1 for the upper part 11 and / or the forming tool T2 for the lower part 12 for the formation of the horns 3 of the watch case 1 on the middle part 2 in the second molding step. These stacks of prepreg components 17 act to help bond the various parts of the watch case to each other, and also as a filler so as not to leave cavities in the structure. However, if desired, cavities can be left in the structure of the watch case.

The stacks of specially prepared prepreg components 17 advantageously consist of multiple prepreg components stacked on top of each other, preferably between about 5 and 15 pieces of prepreg components depending on the shape of the watch case 1 and its horns. These stacks of layered prepreg components17 have a substantially rectangular shape and are inserted into the recesses 18 so that a first end is brought into abutment against the internal part 15 and the second end is then folded over this first end into abutment against the internal part 15 also so that a fold 19 extends outwards from the internal part 15 between the two ends of the prepregs 17 in layers.

This particular arrangement of stacks of prepreg components 17 in layers aims to produce horns 3 tensile resistant made entirely of a composite material and anchored on the middle part 2 of the watch case 1. More specifically, the stacks of prepreg components 17 are assembled so that the carbon fibers in each layer thereof extend in the longitudinal direction of the components 17. This orientation of the fibers in the stacks of prepreg components 17 results in the fibers forming a loop or a fold along the entire length of the horns 3, starting from the middle at one end of the stacks of prepreg components 17 and back towards the middle at the other end of the stacks of prepreg components 17. This orientation folded fibers in horns 3 contributes significantly to the resistance of horns 3 to tensile forces at their free ends where the bars for attaching a bracelet are inserted into holes 4 as shown in figs. 1 and 2 . In fact, experiments have shown that it is not necessary to provide metal sockets in the holes 4, since the composite material has sufficient mechanical strength to allow direct interaction with the ends of the bars.

As can be seen in FIG. 9 also, the stacks of additional prepreg components 17 are positioned in the recesses 18 of the forming tool T1 when the forming tool T5 of the mold M5 for the internal part 15 with said internal part 15 thereon inserted into a corresponding through hole arranged in said forming tool T1 for this purpose as will be better understood below from the description of the second molding step of the method according to the invention.

With the prepreg components 16, 17 additional in place as described above, the second molding step b) of the method according to the invention then comprises, in a third sub-step, the assembly of the upper part 11 , of the lower part 12 and of the two lateral parts 13, 14 around an external surface of the internal part 15 by means of the prepreg components 16, 17 additional in a modular mold M6.

The modular mold M6 is formed by positioning and adjusting the forming tools T1, T2, T3, T4 used in the first step a) with the corresponding individual parts 11, 12, 13, 14 thereon. relative to the others and around the forming tool T5 of the internal part 15 so that said upper part 11, lower part 12 and lateral parts 13, 14 held on their forming tool T1, T2, T3, T4 s' interface with the prepreg components of carbon fibers 16, 17 additional on the internal part 15 and in the recesses of the forming tool T1.

Once this is done, all the forming tools are held against each other in position by another assembly, shown by arrows F in Figs. 10 and 11.

Then, the mold M6 in the assembly is heated to a temperature of at least 130 ° C for at least 30 min to allow the additional prepreg components 16, 17 to bake and mold the upper part 11, lower part 12 and individual side pieces 13, 14 and the inner piece 15 with each other to form a single molded carbon fiber watch case.

Preferably, this second step of hot molding is carried out using a heating technique different from the infrared heating of the first step a) since the mold M6 is entirely made of the heat-resistant steel of individual forming tools. It is therefore preferred to use induction heating to perform this final molding of the watch case.

After the second molding step b), the assembly and the forming tools T1, T2, T3, T4 and T5 are left to cool to room temperature and are then removed from the single molded carbon fiber watch case obtained. at this stage.

It is only necessary to remove any excess material from the single molded carbon fiber watch case by cutting out this excess material and then finishing the watch case 1 by defining the horns 4 and forming through holes 4 in these and also by machining for example the recesses of push-buttons 5 and the corresponding holes 6. However, these last two finishing steps should not be carried out directly after molding, but can be carried out at any time later, in particular during the assembly and assembly of an entire watch.

The above description has been made with reference to a particular example of a watch case 1 made entirely of a carbon fiber composite material according to the method described here. However, obvious modifications to the shape of the watch case so as to carry out any of the molding steps can be arranged by a person skilled in the art without departing from the scope of the invention defined by the claims.

Claims (16)

1. Method for manufacturing a carbon fiber watch case (1) comprising the steps: a) for forming an upper part (11), a lower part (12), two lateral parts (13, 14) and an internal part (15) by molding components prepreg of carbon fibers ( 7, 8, 9, 10) between a forming tool (T1, T2, T3, T4, T5) and a compression counterpiece (C1, C2, C3, C4, C5) complementary to a mold (M1, M2, M3, M4, M5) for each part, the internal part (15) defining a central bore for the middle part (2) of the watch case comprising a thread (22) for the watertight assembly of a case back on the middle part, and preferably a bezel (21) for supporting a glass, on an internal surface of the internal part during the molding of the latter, and b) assembling the upper part, the lower part and the two lateral parts around an outer surface of the internal part with components prepreg of carbon fibers (16, 17) additional interfaces with said upper part, part lower, two side pieces and the inner piece and molding thereof to form the watch case in single molded carbon fiber. 2. Method according to claim 1, in which, in step a), the molds are heated for at least 30 min at a temperature of at least 130 ° C to allow the prepregs to cook. 3. Method according to claim 1 or 2, wherein, in step a), each of the upper part, the lower part, the two lateral parts and the internal part is individually formed in a custom mold by depositing and by adjusting the prepreg components on the forming tool and compressing them on said forming tool with the complementary compression counterpiece during molding. 4. Method according to one of claims 1 to 3, wherein, in step a), a pressure of at least 5 bars is applied to the prepreg components and the forming tool by the compression workpiece complementary. 5. Method according to one of claims 1 to 4, wherein, in step a), the forming tool and the complementary compression counterpiece of each mold are constrained by an assembly. 6. Method according to one of claims 1 to 5, wherein the forming tool is made of a heat resistant material, preferably a metal or a metal alloy. 7. Method according to one of claims 1 to 6, wherein the additional compression counter-piece consists of silicone rubber. 8. Method according to claims 4 and 7, in which the pressure is applied to the forming tool and the prepreg components by thermal expansion of the additional compression counterpiece during the heating of the molds. 9. Method according to one of claims 1 to 8, wherein the mold forming tool for forming the internal part comprises a cylindrical shutter comprising a thread on an outer surface thereof, to form the thread (22) in the internal room. 10. Method according to one of claims 1 to 9, in which the additional compression counter-piece is removed from the forming tool between step a) and step b). 11. Method according to one of claims 1 to 10, in which step b) comprises the following substeps: - adjusting a strip of components prepreg of carbon fibers (16) around the internal part held on its forming tool, and - insertion of stacks of components pre-impregnated with carbon fibers (17) into recesses (18) arranged for them in the forming tool (T1) for the upper part or in the forming tool (T2 ) for the lower part to form the horns of the watch case, and - positioning and adjusting the forming tools of each mold supporting the upper part, lower part and individual side parts molded in step a) relative to each other (T1, T2, T3, T4) and around the forming tool (T5) of the internal part (15) so that said upper part, lower part and lateral parts held on their forming tool interfere with the components prepreg of additional carbon fibers on the internal part and in the recesses, and - holding all the forming tools together with one another, and - heating the forming tools in the assembly to a temperature of at least 130 ° C for at least 30 min to allow the additional prepreg components to bake and mold the upper part, lower part and individual side parts and the internal part with each other to form the single molded carbon fiber watch case. 12. The method as claimed in claim 11, in which the substep consisting in inserting the stacks of components prepreg of carbon fibers (17) into the recesses (18) comprises, for each recess: - cutting individual prepreg components and stacking them on top of each other to form the stack of prepreg components (17) having first and second ends, and - the insertion of a first end of the stack of prepreg components (17) into the recess (18) so that said end is oriented towards the internal part (15), and - the folding of the stack of prepreg components (17) on itself so that the second end of the latter is also oriented towards the internal part (15) and that the fold is oriented towards the outside. 13. Method according to one of claims 11 and 12, wherein, after molding, the assembly and the forming tools are removed from the single molded carbon fiber watch case. 14. Method according to one of claims 1 to 13, in which, at the end of step b), the excess material of the watch case in molded single carbon fibers is cut and the horns (3) are drilled to form through holes (4) designed to receive a bar for fixing a strap to the watch case. 15. watch case in carbon fibers (1) obtained by the method according to one of claims 1 to 14, comprising a middle part (2) comprising an internal thread (22) formed in one piece, and preferably a bezel (21). 16. Carbon fiber watch case according to claim 15, further comprising horns (3) extending outward from the middle part (2) and in one piece with the latter, the horns comprising through holes (4) designed to receive a bar for fixing a strap to the watch case.