Method and device for assembling a movement to a watch case

Abstract

The invention relates to a method for attaching a watch movement (3) to a watch case (1), a fastening element of said movement (3) being brought against an axial bearing surface (11) of said case (1). The method comprises a step of thermally deforming tenons (2) integral with said case (1) so as to locally deform the end of each tenon (2) and form an axial retaining surface (21) vertically holding said fastening element of said movement (3) against said axial bearing surface (11).

Description

[0001] The present invention relates to a method and device for fixing a movement to a watch case.

[0002] In traditional watchmaking, the movement is often attached to the case using flanges and screws that are inserted into threads and press a thread of the movement against a shoulder of the case. While this type of attachment has the advantage of being reliable and reversible, it has the disadvantage of being relatively complex to implement due to the various manipulations required for the screws and flanges, which seriously affects productivity and is therefore unsuitable for the manufacture of watches intended for mass production.

[0003] For attaching the movement to the case, intermediate pressed parts such as casing rings are also known, which allow small, calibrated movements to be fitted into larger cases. However, this method still has the drawback of requiring several assembly steps and additional parts for attachment. This type of attachment method thus allows for greater flexibility, but not significant cost savings.

[0004] There is therefore a need for a method and a device for mounting a movement to a case free from these limitations.

[0005] An object of the present invention is to propose a method and a device for fixing a movement to a case that are alternative to known solutions and do not require screws, flanges, or a mounting ring.

[0006] These goals are achieved by means of a method for fixing a watch movement to a watch case, a fixing element of the movement being brought against an axial bearing surface of the case, characterized in that it includes a step of thermoforming tenons attached to the case so as to locally deform the end of each tenon and form an axial retaining surface vertically retaining the fixing element of the movement against the axial bearing surface of the case.

[0007] These objectives are also achieved by means of a device for attaching a watch movement to a watch case, comprising a movement attachment element positioned against an axial bearing surface of the case. The device is characterized in that it comprises thermoformable lugs integral with the case, the movement attachment element being held against said axial bearing surface by means of a deformation of the ends of the lugs forming an axial retaining surface.

[0008] These goals are also achieved through a case and a movement taken separately for the implementation of the assembly method, the case being characterized in that it includes thermoformable fixing tenons, and the movement corresponding to a preferred embodiment in which the fixing element consists of a collar provided with a plurality of holes, or a plurality of ears, the holes in the ears or the collar being provided for the insertion of the tenons.

[0009] One advantage of the proposed solution is that it facilitates assembly operations and minimizes production costs. The thermoforming of the tenons for the final attachment of the movement can be carried out very quickly without requiring tedious handling, thus increasing productivity. Furthermore, the movement can be assembled dial-side down, which avoids the need for a reversing operation as with conventional case-side mounting.

[0010] Another advantage of the proposed solution is that it is compatible with a large number of types of movements, and in particular those both equipped and not equipped with a net.

[0011] Moreover, according to a particularly advantageous preferred embodiment, no additional fixing parts are required, all the fixing elements being directly integrated into the movement and the case.

[0012] Other advantages will become apparent from the examples of implementation of the invention indicated in the detailed description and illustrated by the accompanying figures in which: Fig. 1 illustrates a top view of a movement assembled in a case according to a preferred embodiment of the invention; Fig. 2 illustrates a cross-sectional view along axis AA of the movement and case according to the preferred embodiment of the invention of Fig. 1; Fig. 3 illustrates a detailed view of the movement attachment to the case according to the preferred embodiment of the invention illustrated by Fig. 2; Fig. 4 shows a cross-sectional view along the CC axis corresponding to the 3 o'clock - 9 o'clock axis of the watch of a complete watch comprising a movement assembled to the case according to the preferred embodiment of Fig. 1; Fig. 5 shows a top view of a movement assembled in a case according to an alternative embodiment of the invention; Fig. 6 shows a cross-sectional view of an alternative fixing method for movement in a case according to an alternative embodiment of the invention; Fig. 7 shows a cross-sectional view of an alternative method of fixing movement in a case, using tenons arranged on removable parts.

[0013] In what follows, reference will be made jointly to Figs. 1, 2, and 3, which illustrate different views of a preferred embodiment for the movement assembly device 3 in a case 1 according to the present invention, and to Fig. 4, which shows a complete watch using this assembly device. The movement 3 is not threaded for its attachment, but has, as a fastening element, a collar 32 around its periphery. This collar 32 comprises a plurality of holes 321—ten in total, as shown in Fig. 1—for receiving tenons 2. This preferred number of tenons 2 is intended to receive the mainplate of a movement 3 having a mass of up to 20 grams, when they are made of plastic. Other parameters relating to the retention of the movement, such as their diameter and the surface area of ​​the axial retention surface 21 they provide, are discussed later with reference to Fig. 3.

[0014] According to this preferred embodiment, the collar 32 used for securing the movement 3 is preferably made from the same material as the rest of the movement 3, which allows the entire assembly to be manufactured directly by molding, without requiring any additional dedicated assembly operation for this fastening element. Similarly, the holes 321 can be obtained directly without requiring any specific drilling operation. Likewise, the arrangement of the tenons 2 directly on the case 10 eliminates the need for an additional assembly or machining step for these case fastening elements. In this case, both the movement 3 and the case 10 are preferably made of plastic, the deformation properties of which are suitable for the thermoforming operation, and to allow for a simple molding operation, particularly injection molding, for their manufacture.However, it is also possible to use fixing elements, such as the collar 32, made of a different material such as metal, ceramic, or even wood.

[0015] According to the invention, the thermoforming of the end is intended to perform a function similar to that of riveting, that is, without necessarily bonding the axial retaining surface 21 formed on the end of the tenon 2 to the axial bearing surface 11. However, reference is sometimes also made to a heat-welding operation which, depending on the materials used for the body 1 and the tenons 2, does not necessarily imply their mutual bonding at their contact surfaces. Those skilled in the art will understand, however, that such a possible bonding of the fastening elements is not detrimental to the implementation of the present invention.

[0016] In Fig. 1, the movement 3 is shown from the dial side, although the latter is not yet assembled on its upper face (Fig. 4, described in detail later, illustrates a cross-sectional view of a fully assembled watch with the dial 7 affixed to the movement 3, as well as the components enclosing the case 1, such as the case back 14 and the crystal 9). A date ring 37 can be seen inside the bezel 32, along with two sets of 5 fixing lugs distributed on either side of a diameter on which are parallel alignment guides 13. According to the preferred embodiment illustrated, the alignment guides 13 are male elements also arranged directly on the case middle 10.Their machining is more precise than that of the tenons 2 to ensure the positioning and angular locking of the movement 3 in a given position; the movement 3 is thus introduced from the dial side by threading the tenons 2 into the orifices of the collar 32, and in parallel the keying 13 into corresponding female elements, arranged preferably on the periphery of the movement 3, as here on the collar 32.

[0017] Fig. 2 illustrates a cross-sectional view along axis AA shown in Fig. 1, of two diametrically opposed tenons 2 after the movement has been mounted in the case 1, i.e., after the thermoforming operation. The case 1 is shown here without its case back 14 – visible in Fig. 4 – i.e., only by means of the case middle 10, on a protruding part 100 of which the tenons 2 are arranged. This embodiment is advantageous because it frees up space between the case back 3 and the case back 14 to accommodate other parts, such as, for example, an oscillating weight 36 like the one illustrated in Fig. 1. 4, whereas it is not possible to superimpose parts on the upper face of the movement 3 where only the dial is generally positioned and no visual obstruction to reading the time is conceivable.According to an alternative embodiment, it would also be possible to form the tenons 2 on another part of the case 1, such as directly on the bottom 14 visible in Fig. 4; however, this variant would require positioning the fixing collar 32 lower to minimize the height of the tenons 2 and would be less efficient in terms of centering if the bottom is not formed in one piece with the case 10.

[0018] Fig. 2 shows the tenons 2 after they have already been deformed by the thermoforming operation and thus allow the collar 32 to be held vertically along the axis ZZ of the cannon pinion 30 of the watch hands; the detail of the assembly part surrounded by the circle B is shown in Fig. 3. On the upper face of the movement, the date ring 37 visible in Fig. 1 can still be distinguished, while the external side wall 33 of the movement, as well as a portion of the internal side wall 12 of the case 1, can be seen, against which the external side wall 33 is in contact or not. The bottom of the movement 35 does not come to rest on the bottom 14 of the case 1, not shown in this figure, the movement 3 being brought to rest on the axial bearing surfaces 11 of the case 10 on which the lower surface of the collar 32 comes to rest after the orifices 321 of the latter have been engaged on the fixing tenons 2.

[0019] Fig. 3 shows the detail of the attachment of the movement to the case 1 according to the preferred embodiment of Fig. 2, with the collar 32 resting on the axial bearing surface 11 of the case 10, arranged here on a prominent internal part 100 of the case 10. The tenon 2, engaged in the orifice 321 of the collar 32, is deformed by the thermoforming operation and has a mushroom shape 20 at its upper end, which provides an axial retaining surface 21 on its lower face to vertically retain the collar 32 pressed against the axial bearing surface 11 of the case 10. As can be seen in this figure, there is not necessarily contact between the external side wall 33 of the movement and the internal side wall 12 of the case, which allows for increased machining tolerances at this point, the centering of the plate and the movement 3 being preferably sufficiently achieved by the locating notches 13.The gap between the diameter of the orifice 321 of the collar 32 and the diameter of the tenon 2 is, however, preferably chosen to be less than 0.2mm, in order not to reduce too much the contact area between the lower face of the mushroom 20 and the axial bearing surface 21.

[0020] It can also be noted in this figure that the ratio between the radius of the tenon 2 and that of the mushroom 21 is approximately 1.5, and that the thickness of the mushroom 20 is substantially equal to the radius of the tenon 2. The preferred embodiment of Fig. 1 uses such a mushroom shape 21 for a tenon 2 having a diameter preferably between 1 and 2 mm, which makes it possible to support a movement 3 having a mass greater than 10 grams with a number of plastic tenons greater than or equal to 6. Thanks to the hyperbolic reduction of the stresses exerted on each tenon 2 as a function of their number, it is also possible, for the sake of economy, to limit the number of tenons 2 to a maximum of 15. In order to limit the number of tenons 2 as much as possible, it is also possible to use a more rigid material than the plastic usually used in watch cases.

[0021] Fig. 4 shows a view of an integral watch using the assembly method and device described in Figs. 1 to 3 above, along the cutting axis CC illustrated in Fig. 1 corresponding to the 3h-9h axis which does not pass through the thermoformed tenons 2 unlike the cutting axis of Figs. 2 and 3. The fixing collar 32 is still visible, which, at this angle, takes the form of an annular shoulder, resting on the axial support surface 11 arranged on the upper surface of the internal protruding part 100 of the case 10. On the upper face of the movement on the dial side, the date ring 37 is still visible, but this time it is surmounted by a dial 7 above which the seconds 301, minute 302 and hour 303 hands rotate, driven by the central cannon 30 of the movement 3, and which is also provided with an aperture 71 showing the current date values.The peripheral portion 72 of the dial is held in place by the crystal 9, surmounted by a bezel 91, and which is attached to a bearing 15 of the case 10, for example, by ultrasonic welding. The case 10 is traversed by a stem 6 conventionally including a crown 61 at its distal end for easy manipulation by the user. The case 1 is closed by a case back 14 above which is housed an oscillating weight 36 coupled to the movement 3 for its automatic winding, and whose lateral edges 361 extend up to the lower level of the protruding inner portion 100 of the case 10.

[0022] The proposed device and fixing method are therefore applicable to all types of watches, whether quartz or fully mechanical.

[0023] Other variations for the fastening are possible for producing the fastening element, which may, for example, have fastening lugs 31 instead of the collar 32 with a hole for the tenons 2. Such a variation is illustrated in Fig. 5, which shows a top view similar to Fig. 1 of a watch, where the mushroom shape 20 at their tip and the shape of the lugs 31 closely following the shape of the tenon 2 are more clearly visible. In this case, the lugs 31 are simply designed to have a central fastening hole into which the tenons 2 must be inserted before the thermoforming operation, as well as lower and upper bearing surfaces for their axial retention along the vertical axis corresponding to that of the hands' barrel 30. They thus make it possible to reduce the volume of material required to form the movement's fastening element and thereby optimize costs.According to this alternative embodiment, the locking of the degree of freedom in rotation is preferably always achieved by means of keying 13. Otherwise, one can distinguish on this fig. 5, in addition to the date ring 37 on the periphery of the movement 3, the gripping crown 61 at 3 o'clock on the case 1.

[0024] Fig. 6 illustrates another alternative embodiment for the method and device for fixing a movement, according to which the movement 3 again includes a thread 34, unlike those of the preferred embodiment which lacked it, and a retaining ring 4. The movement thread 34, which is used as a fixing element, the lower surface 341 of the thread being brought against an axial bearing surface 11 of the case 10, then the retaining ring 4, comprising a plurality of holes 41, is threaded onto the tenons 2 which are preferably made of the same material as the case 10. The thermoforming operation of the tenons 2 forms mushrooms 20 above the retaining ring 4 and the axial retaining surface 21 thus generated allows the retaining ring 4 to be pressed against an upper surface 342 of the movement thread 34, which in turn remains pressed against the axial bearing surface 11 of the case 10.The advantage of this alternative variant is that it allows the use of a traditional movement 3 with thread 34; the disadvantage, however, is that it requires the use of an additional part - the retaining ring 4 - so that the fixing elements are no longer directly integrated respectively into the case 1 and the movement 3.

[0025] Fig. 7 illustrates another alternative embodiment of the invention concerning the tenons 2, which are arranged on plugs 5 provided with grooves 51 to facilitate their insertion into holes in the case 1, preferably in the case body 10. Such a modular arrangement of the plugs makes it possible to separate the material chosen for the case body 10 from that chosen for the tenons; it would thus be possible, for example, to choose plastic plugs 5 while the case body 10 is made of metal. It will also be understood that this variant of removable tenons 2 is compatible with all the other embodiments described above with reference to Figs. 1 to 6.

Claims

1. Method for fixing a watch movement (3) to a watch case (1), a fixing element of said movement (3) being brought against an axial support surface (11) of said case (1), characterized in that it comprises a thermoforming step of tenons (2) integral with said case (1) so as to locally deform the end of each tenon (2) and form an axial retaining surface (21) vertically retaining said fixing element of said movement (3) against said axial support surface (11).

2. Method for fixing a watch movement (3) to a watch case (1), said movement (2) being introduced dial side (7).

3. Method for fixing a watch movement (3) to a watch case (1) according to claim 1 or 2, characterized in that it comprises a preliminary step of inserting said tenons (2) into through holes arranged in said fixing element before the thermoforming step.

4. Device for fixing a watch movement (3) to a watch case (1), comprising a fixing element of said movement (3) positioned against an axial bearing surface (11) of said case (1), said device being characterized in that it comprises thermoformable lugs (2) integral with said case (1), said fixing element of the movement (3) being held against said axial bearing surface (11) by means of a deformation of the end of said lugs (2) forming an axial retaining surface (21).

5. Device for fixing a watch movement (3) to a case (1) according to claim 8, characterized in that a keying device (13) is arranged on a case (10) for the angular positioning of said movement (3) in said case (1).

6. Device for fixing a watch movement (3) to a case (1) according to one of claims 4 or 5, characterized in that it comprises a retaining ring (4), said movement (3) further comprising a thread (34), said axial retaining surface (21) of said tenons (2) pressing said retaining ring (4) against an upper surface (342) of said thread (34).

7. Frame (10) for implementing the fixing method according to claims 1 to 3, characterized in that it comprises thermoformable fixing tenons.

8. Carcass (10) according to claim 7, characterized in that said tenons (2) are formed of material with said carcass (10).

9. Case (10) according to claim 7, characterized in that said tenons (2) are arranged on a removable plug (5) driven into said case (1).

10. Movement (3) for implementing the fastening method according to claims 1 to 3, characterized in that said fastening element is formed by a collar (32) provided with a plurality of orifices (321) or a plurality of ears (31).

11. Movement (3) according to claim 10, characterized in that said collar (32) or ears (31) are formed of material with said movement (3).