Method for assembling a watch crystal with a watch case

Abstract

The method for assembling a table mirror (26) to a table case (24) by means of gluing provides a flange (18) separate from the table case and sized so as to be forcedly inserted into an opening in the table case which delimits on the inside an annular surface (13). The flange is partially inserted into the opening and an adhesive (20a) is applied to the annular surface, then the table mirror is correctly placed on the flange and pressure is exerted on the table mirror so that the insertion of the flange into said opening continues until the adhesive covers the lower peripheral surface (25) of the inner surface (27) of the table mirror facing the annular surface. Finally, the adhesive hardens and thus forms a firm joint between the table mirror and the table case.

Description

Technical Field

[0001] The present invention relates to a method for assembling a watch crystal and a watch case together, and more specifically, to a watch crystal disposed above an analog time display.

[0002] Within the scope of this invention, the watch crystal is intended to be fastened to the watch case by bonding to form a watch. Where the watch case includes a portion forming the bezel, assembly is preferably performed without resilient washers between the sidewall of the watch crystal and the inner wall of the bezel positioned facing that sidewall. Background Technology

[0003] For various watches, especially those without a radially surrounding upper edge of the case (i.e., without a conventional bezel), it has been proposed to secure the watch crystal, particularly a crystalline lens, by bonding. For example, Swiss Patent No. 622 151 describes an embodiment of a watch case formed from an intermediate component having a horizontal upper surface, to which a sapphire crystal is bonded via an outer peripheral region of its inner surface positioned facing the horizontal upper surface of the intermediate component. To conceal the adhesive from the viewer's perspective when observing the finished watch, the crystal may have an opaque, thin metallic coating on the outer peripheral region of the crystal, which adheres highly to the adhesive selected for assembly. This coating may be positioned such that it extends slightly inward beyond the outer peripheral region, thereby obscuring the edge of the dial from an axial view through the crystal.

[0004] This document discloses a technique for improving the aesthetic appearance of the assembled "bezel and crystal" assembly, specifically a technique for machining (including grinding) the side surfaces of the crystal and the top of the outer surface of the center piece. This provides a continuous surface between the side surfaces of the crystal and the center piece, and furthermore, this machining removes any adhesive residue that might flow to the outer side of the horizontal upper surface (which is quite possible). It should be noted that removing excess adhesive on the outer side of the case can also be achieved by other means, such as using chemicals. However, a significant problem arises because adhesive can flow to the inner side of the case, entering the space between the dial and the crystal used for the analog time display, particularly along the vertical inner surface of the center piece that defines this space. This is why a masking metallic coating extending over the area located at the edge of the dial reduces this space.

[0005] Japanese Patent N OS56-27686 U describes various alternative embodiments of the upper portion of a watch case, which is configured to receive the watch crystal and is secured to the upper portion of the case by adhesive. The upper portion defines an annular surface that is bonded to the lower surface of the watch crystal. Adhesive readily overflows from the inside of the annular surface along a side surface defined below the watch crystal and visible through the crystal, such that any adhesive overflow is clearly visible from the central side of the watch, as shown in the first figure.

[0006] French Patent N O .2524992 combined with its Figures 1 to 3 A watch is described, having a crystal bonded to a flange, which is fastened to a central component by claws. Figure 3 In the alternative embodiment shown, the protrusion at the upper edge of the intermediate component forming the case covers the side surface of the crystal. A groove between the vertical outer surface of the flange and the protrusion allows excess adhesive to flow into the groove. This solves the problem of excessive adhesive on the outside of the flange, provided the top of the groove can be evenly covered with adhesive; however, because the flange is thus bonded to the case, it makes it difficult to remove the "flange and crystal" assembly, especially if the crystal needs to be replaced, and if the crystal is potentially cracked. The problem of excessive adhesive flowing along the inner surface of the flange, visible through the crystal, is addressed in French patent N. O The issue remains unresolved in .2524992. Summary of the Invention

[0007] The primary objective of this invention is to solve the aforementioned problems associated with bonding the watch crystal to the annular shoulder of the watch case, particularly the horizontal annular surface, while preventing adhesive from flowing into the enclosed space of the watch's display, particularly an analog display. A second objective is to achieve the primary objective while simultaneously ensuring that the annular surface of the watch case, intended for bonding to the inner surface of the watch crystal, can accommodate sufficient adhesive to ensure that the annular surface is adequately and preferably uniformly covered by the adhesive.

[0008] Therefore, the present invention relates to an assembly method for assembling a watch crystal to a watch case to form a watch, the watch case having an annular surface designed to be bonded to the lower outer peripheral surface of the inner surface of the watch crystal. The watch includes a flange having an upper surface and dimensions defined to allow for forced insertion along an insertion axis along an axial inner surface of the upper portion of the watch case, the axial inner surface defining the annular surface on the central side of the watch case.

[0009] The assembly method includes the following steps:

[0010] - The flange is partially inserted into the opening defined by the axial inner surface;

[0011] - Deposit the adhesive on the annular surface of the case and / or on the lower outer peripheral surface;

[0012] The following steps are next:

[0013] - The watch lens is brought to rest against the upper surface of the flange and into a final horizontal position, in which the lower outer peripheral surface of the watch lens is axially superimposed on the annular surface, and the upper surface of the flange thus comes into contact with a contact surface of the inner surface of the watch lens adjacent to the lower outer peripheral surface, the contact surface and the upper surface of the flange being configured such that there is at least one continuous annular contact area between the two surfaces.

[0014] - An axial pressure is applied to the outer surface of the watch crystal, the intensity of which allows the flange to be gradually inserted into the opening until the upper surface of the flange reaches a final axial position above the annular surface, and until the lower outer peripheral surface of the watch crystal is covered with adhesive to form a continuous adhesive ring between the annular surface of the watch case and the lower outer peripheral surface of the watch crystal.

[0015] - Harden the adhesive to form a strong joint.

[0016] According to an advantageous alternative embodiment, at the end of the step of applying axial pressure to the outer surface of the watch crystal, the upper surface of the flange is axially positioned above the annular surface of the watch case at an axial distance greater than 20 micrometers and less than 100 micrometers. For this purpose, in a particular alternative embodiment, the watch case includes a shoulder that forms an axial stop for the flange. Preferably, this stop defines an annular stop surface that is continuous and parallel to the lower surface of the flange, and at the end of the step of applying axial pressure to the outer surface of the watch crystal, the lower surface of the flange abuts against the entire continuous annular stop surface.

[0017] In another advantageous alternative embodiment, the axial inner surface is parallel to at least one continuous annular region of the outer surface of the flange, the at least one continuous annular region being configured such that once the continuous annular region has been inserted along the axial inner surface, the continuous annular region is in continuous contact with the axial inner surface.

[0018] According to the primary embodiment, the upper portion of the watch case includes a protrusion forming an edge that defines a sidewall extending axially upward from the outer periphery of the annular surface. At the end of the step of applying axial pressure to the outer surface of the watch crystal, the sidewall radially surrounds the watch crystal. In an advantageous alternative embodiment, some of the adhesive rises into a groove between the sidewall of the watch crystal and the edge, forming a strong joint that completely covers the annular surface and at least partially fills the groove. Attached Figure Description

[0019] The invention will now be described in more detail with reference to the accompanying drawings, which are given by way of non-limiting example, wherein:

[0020] - Figure 1 The case and flange are shown in a first intermediate state produced during the assembly method according to the invention.

[0021] - Figure 2 The case, flange, and crystal are shown in a second intermediate state produced during the assembly method according to the invention; and

[0022] - Figure 3 The final state of the watch case, flange, and crystal produced by the assembly method according to the invention is shown. Detailed Implementation

[0023] The main embodiments of the method for assembling a watch crystal into a watch case to form a watch, according to the present invention, will now be described with reference to the accompanying drawings.

[0024] The watch case 4, intended for use in watch 2, is integrally formed, defining the back cover 6 and the central bezel. Other alternative embodiments with separate back covers and / or bezels separate from the central component are also conceivable. It should be noted that, for clarity, the terminology used in the description of the invention distinguishes between the watch case 4, the flange 18, and the crystal 26, thus forming three initially separate distinct elements. The watch case includes an upper portion 5 having a first shoulder defining an annular surface 13, which is horizontal in the described alternative embodiment. "Horizontal surface" is understood to mean a surface perpendicular to the central axis of the watch case 4. This annular surface is intended to be bonded to the lower outer peripheral surface 25 of the inner surface 27 of the crystal 26, which defines a surface parallel to the annular surface. In other alternative embodiments, the lower outer peripheral surface of the watch crystal is generally parallel to the annular surface, or lower outer peripheral surface, except in annular regions, for example, where an annular groove is provided, which is substantially located in the middle of the width of the annular surface to form a hollow portion for receiving adhesive 20a for assembling the watch crystal to the watch case, and thus forming a middle region of a secure joint 20b obtained after the assembly, the secure joint 20b having a large adhesive thickness.

[0025] Subsequently, the upper portion 5 of the case 4 defines an axial inner surface / vertical inner surface 14, which defines the boundary of an annular surface 13 on the inner side of the case, extending downward from the inner periphery of the annular surface. The upper portion 5 includes a protrusion forming an edge 12 that defines a sidewall 28 extending vertically upward from the outer periphery of the annular surface 13. Once the crystal 26 is placed in the upper opening in the bezel of the case 4 to close the case, the vertical sidewall is intended to radially surround the crystal 26 in a conventional manner. It should be noted that the adjective "vertical" and the adverb "vertically" refer to "axial" and "axially," respectively, i.e., along the central axis of the case. The watch 2 also includes a flange 18, which is separate from the upper portion 5 of the case, and the flange is sized such that it can be forcibly inserted into the opening along the axial inner surface 14 defining the opening in the upper portion 5 along an insertion axis coinciding with the central axis of the case. The axial inner surface restricts an annular surface on the central side of the case. The flange 18 has an upper surface 19, which, once the watch crystal is installed in the case, is configured to face the inner surface 27 of the watch crystal as a contact surface 29. This contact surface 29 is adjacent to the lower outer peripheral surface 25. In general, the upper surface 19 and the contact surface 29 are configured such that, once the watch crystal has been inserted into the recess formed by the upper opening in the bezel of the case 4, when the watch crystal 26 is applied to the flange 18, at least one continuous annular contact area exists between these two surfaces. Preferably, the upper surface 19 and the contact surface 29 of the watch crystal are parallel.

[0026] The case also includes a second shoulder that forms a stop 15 for the flange 18. It should be noted that the stop, intended to define the final axial position of the flange 18 or for the lower boundary of the flange, could also be formed by a case bushing for the movement 8, by the movement itself, or by a dial 10 arranged above the movement. However, considering the manufacturing tolerances of each component and the assembly tolerances of the various elements to be assembled in the case, the stop intended for the flange 18 is preferably formed by the case itself. Generally, the annular surface 13 and the stop 15 are advantageously defined by the same component, which allows for precise management of the axial distance between the annular surface 13 and the stop 15. This advantage will become more apparent in the following description of the assembly method according to the invention. The stop 15 defines an annular stop surface parallel to the lower surface 32 of the flange, which is positioned facing the annular stop surface once the flange is inserted along the axial inner surface 14 of the case 4. Preferably, the axial inner surface 14 of the case 4 is parallel to at least one continuous annular region of the outer surface 30 of the flange, the continuous annular region being configured such that once inserted along the axial inner surface, it is in continuous contact with the axial inner surface 14. In an advantageous alternative embodiment, the continuous annular region is formed by the lower portion of the outer surface 30 of the flange. In a particular alternative embodiment, once the flange is in its final position in the case 4, the axial inner surface 14 of the case 4 is parallel to the outer surface of the flange, at least parallel to the portion of the outer surface facing the axial inner surface.

[0027] In order to form the watch 2, the movement 8 with the dial 10 is first introduced into the watch case 4. The movement has a minute hand 22 and an hour hand 23, which together form an analog time display 24.

[0028] The method for assembling the watch crystal 26 into the watch case 4 includes the following two steps:

[0029] - The flange 18 is partially inserted into the opening defined by the axial inner surface 14 at an axial distance less than the height of the flange. Due to this partial insertion, the upper surface 19 of the flange is positioned above the annular surface 13 and above the intended final axial position of the upper surface.

[0030] - Deposit adhesive 20a onto the annular surface 13 of the case and / or onto the lower outer peripheral surface 25 of the crystal;

[0031] The following three steps are next:

[0032] - The watch crystal 26 is placed against the upper surface 19 of the flange 18 and positioned substantially in a final horizontal position, in which the annular surface 13 of the watch case is axially stacked on the lower outer peripheral surface 25 of the watch crystal, and the upper surface of the flange is in contact with the contact surface 29 of the inner surface 27 of the watch crystal; the contact surface and the upper surface of the flange are configured such that there is at least one continuous annular contact area between the two surfaces.

[0033] - An axial pressure is applied to the outer surface of the watch crystal, the strength of which allows the flange 18 to be gradually inserted into the corresponding opening defined by the axial inner surface 14, until the lower outer peripheral surface 25 of the watch crystal is covered by adhesive 20a, so as to form a continuous adhesive ring between the annular surface 13 of the watch case and the lower outer peripheral surface 25 of the watch crystal, and until the upper surface 19 of the flange reaches the final axial position, which is located above the annular surface 13; and

[0034] - Harden the adhesive to form a strong joint 20b.

[0035] Due to the features of the method according to the invention for assembling the watch crystal to the watch case, the adhesive does not flow along the inner surface 34 of the flange 18. It should be noted that, in an alternative embodiment, the introduction of the movement 8 with the dial 10 from above can occur between the deposition of the adhesive mentioned above and the partial insertion of the flange. In an alternative embodiment where the watch case includes a back cover intended for removal from the intermediate components, the introduction of the dial with the analog display and the movement can be made from below, i.e., via an opening intended to be closed by the back cover after the assembly method.

[0036] In an advantageous alternative embodiment, at the end of the step of applying axial pressure to the outer surface of the crystal, the flange 18 abuts against the stop 15. Therefore, the lower surface 32 of the flange rests against the entire annular stop surface defined by the stop. In another alternative embodiment, the stop of the flange can be formed by the dial 10. However, as already mentioned, this latter alternative embodiment has tolerance issues, meaning that it is difficult to correctly manage the final position of the upper surface 19 of the flange at the end of the axial pressure step.

[0037] In another advantageous alternative embodiment, at the end of the step of applying axial pressure to the outer surface of the watch crystal, the upper surface 19 of the flange 18 is axially positioned above the annular surface 13 of the watch case at an axial distance greater than 20 micrometers (20 μm) and less than or equal to 100 micrometers (100 μm). Specifically, taking into account manufacturing tolerances, for example, an axial distance between 60 micrometers and 70 micrometers (60 μm-70 μm) is used as a setpoint value. This ensures that the robust joint 20b formed by the adhesive 20a and obtained after the adhesive curing step has a certain non-zero thickness.

[0038] In a first alternative embodiment of another implementation of the assembly method, a certain thickness of the adhesive joint 20b can be obtained by patterning the annular surface 13 or the corresponding lower outer peripheral surface 25. Specifically, the annular surface has a pattern defining recessed areas and / or recessed paths for the adhesive 20a. In a second alternative embodiment, spacers, particularly small beads (e.g., balls with diameters between 50 and 150 micrometers), are introduced into the adhesive. The spacers are incorporated into the adhesive 20a to ensure a minimum thickness of the secure joint 20b across the entire annular surface 13. This other embodiment of the invention not only ensures that the adhesive forming the secure joint has a certain non-zero thickness, but that this thickness is substantially constant. Therefore, the thickness of the adhesive before curing can be properly managed. It can be seen that in this other embodiment, the presence of the stop 15 for determining the final axial position of the flange is not essential to prevent the flange from eventually reaching the same level as the annular surface 13, because it is precisely the aforementioned pattern or spacers, particularly glass beads or synthetic beads, that ensure that the axial pressure applied to the mirror 26 does not cause the two surfaces to reach the same level, i.e., the same axial position.

[0039] At least during the first stage of the step of hardening adhesive 20a, it is preferable to maintain axial pressure applied to the outer surface of the mirror 26.

[0040] In the alternative embodiment shown in the accompanying drawings, as already noted, the upper portion 5 of the case 4 includes a protrusion forming an edge 12 that defines a sidewall 28 extending axially upward from the outer periphery of the annular surface 13, which radially surrounds the crystal 26 at the end of the step of applying axial pressure to the outer surface of the crystal. Preferably, the amount of adhesive 20a provided in the adhesive deposition step is designed such that, during the step of applying axial pressure to the outer surface of the crystal, some of the adhesive rises into the groove between the side of the crystal and the sidewall 28 of the edge 12. Thus, the secure joint 20b completely covers the annular surface 13 and at least partially fills the groove. This groove thus serves as a reservoir for receiving excess adhesive and also helps to secure the crystal 26 to the case 4 by bonding, ensuring that the resulting adhesive joint 20b is sufficiently strong.

Claims

1. An assembly method for assembling a watch crystal to a watch case to form a watch, the watch case having an annular surface (13) intended to be bonded to the lower outer peripheral surface (25) of the inner surface (27) of the watch crystal; characterized in that, The watch includes a flange (18) having an upper surface (19) and being sized to be forcibly inserted along an insertion axis along an axial inner surface (14) of the upper part (5) of the watch case, the axial inner surface defining the annular surface on the central side of the watch case. The assembly method includes the following steps: - The flange is partially inserted into the opening defined by the axial inner surface; - Deposit adhesive (20a) on the annular surface of the case and / or on the lower outer peripheral surface; The following steps are next: - The mirror is brought to rest against the upper surface of the flange and into the final horizontal position of the mirror, in which the lower outer peripheral surface of the mirror is axially superimposed on the annular surface, and the upper surface of the flange is thus in contact with the contact surface (29) of the inner surface of the mirror adjacent to the lower outer peripheral surface, the contact surface and the upper surface of the flange being configured such that there is at least one continuous annular contact area between the two surfaces; - An axial pressure is applied to the outer surface of the watch crystal, the strength of which allows the flange to be gradually inserted into the opening until the upper surface of the flange reaches a final axial position above the annular surface, and until the lower outer peripheral surface of the watch crystal is covered with adhesive to form a continuous adhesive ring between the annular surface of the watch case and the lower outer peripheral surface of the watch crystal. - Harden the adhesive to form a strong joint (20b).

2. The assembly method according to claim 1, characterized in that, The case (4) includes a shoulder that forms a stop (15) for the flange (18).

3. The assembly method according to claim 2, characterized in that, The stop portion (15) defines an annular stop surface that is continuous and parallel to the lower surface (32) of the flange, at the end of the step of applying axial pressure to the outer surface of the mirror, the lower surface of the flange abuts against the entire continuous annular stop surface.

4. The assembly method according to any one of claims 1 to 3, characterized in that, The axial inner surface is parallel to at least one continuous annular region of the outer surface (30) of the flange, the continuous annular region being configured such that once the continuous annular region has been inserted along the axial inner surface, the continuous annular region is in continuous contact with the axial inner surface.

5. The assembly method according to any one of claims 1 to 3, characterized in that, The axial pressure applied to the outer surface of the watch mirror (26) is maintained at least during the first stage of the step of hardening the adhesive.

6. The assembly method according to any one of claims 1 to 3, characterized in that, At the end of the step of applying axial pressure to the outer surface of the mirror (26), the upper surface (19) is located above the annular surface (13) at an axial distance greater than 20 micrometers and less than 100 micrometers.

7. The assembly method according to any one of claims 1 to 3, characterized in that, The annular surface (13) of the watch case or the lower outer peripheral surface (25) of the watch crystal (26) has a pattern that defines a recessed area and / or recessed path for the adhesive.

8. The assembly method according to any one of claims 1 to 3, characterized in that, The spacer is incorporated into the adhesive (20a) to ensure that the secure joint (20b) has a minimum thickness across the entire annular surface (13).

9. The assembly method according to any one of claims 1 to 3, characterized in that, The upper portion (5) of the case includes a protrusion forming an edge (12) that defines a sidewall (28) that extends axially upward from the outer periphery of the annular surface and radially surrounds the crystal at the end of the step of applying axial pressure to the outer surface of the crystal.

10. The assembly method according to claim 9, characterized in that, The amount of adhesive provided in the adhesive deposition step is designed such that, in the step of applying axial pressure to the outer surface of the watch crystal, some of the adhesive rises into the groove between the sidewalls of the watch crystal and the edge, and the resulting strong joint completely covers the annular surface and at least partially fills the groove.

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