WATERPROOF WATCH CASE WITH FIXING GASKET

Description

TECHNICAL FIELD

[0001] The present invention relates to a waterproof watch case with a fixing gasket, in particular for a diving watch. TECHNOLOGICAL BACKGROUND

[0002] To provide for the use of a mechanical or electronic watch underwater, the watch case, which includes a watch movement or a time-based watch module, must be closed in a well-sealed manner. To achieve this, the watch case includes a back fixed in a sealed manner to a first side of a caseband and a crystal fixed to a second, opposite side of the caseband. Sealing gaskets are provided at the assembly of the back, the caseband and the watch crystal. A control or adjustment member for functions of the watch is also mounted in a sealed manner through the caseband of the case in the rest position.

[0003] Watch cases are generally not configured or assembled to withstand high water pressures, for example during diving, since the pressure inside the watch case is close to atmospheric pressure. Simple conventional watch gaskets are not sufficient to ensure a good watertightness of the case when diving to very great depths underwater.

[0004] Patent CH 378 792 describes a waterproof watch case. The crystal is a disc of transparent mineral material. A soft or malleable metal gasket is driven into the periphery of the crystal against an upper rim. This crystal and gasket assembly is driven into a cylindrical bore of a support, such as a caseband. The diameter of the cylindrical bore is slightly smaller than the outside diameter of the soft metal gasket to ensure a good seal when the assembly is driven into the cylindrical bore. The crystal includes a conical bearing surface on one inside to come into direct contact with a complementary conical bearing surface of the caseband, but this does not ensure good direct contact between the two conical surfaces.Additionally, although the soft metal gasket can provide a good watertight seal, during a saturation dive the ice can be easily dislodged requiring the replacement of the retaining gasket afterwards, which is a disadvantage.

[0005] Patent application EP 3 736 644 A1, in the name of Omega SA, describes a waterproof watch case for a diving watch, comprising a back mounted on a lower side of a caseband, and a crystal mounted on an upper side of the caseband. The crystal comprises an annular peripheral surface mounted by a first part of an annular gasket made of amorphous metal on a complementary shaped annular inner surface of the upper side of the caseband. A second part of the gasket on the first part of the gasket holds the crystal to the caseband. The annular peripheral surface of the crystal is inclined towards the inside of the watchcase at an angle smaller than 90° relative to a central axis perpendicular to the plane of the watchcase to distribute stresses between the crystal and the caseband due to water pressure during a dive. The annular peripheral surface and the annular inner surface are conical in shape. SUMMARY OF THE INVENTION

[0006] The main aim of the invention is therefore to overcome the drawbacks of the state of the art described above by proposing a waterproof watch case with a fixing seal and adapted to allow diving to great depths underwater.

[0007] To this end, the present invention relates to a waterproof watch case with a fixing gasket, which comprises the features of independent claim 1.

[0008] Particular embodiments of a waterproof watch case with a fixing gasket are defined in dependent claims 2 to 7.

[0009] An advantage of the waterproof watch case is that the crystal is fixed to the caseband by means of a fixing gasket fixed in direct contact over its entire height against an annular outer wall of the crystal and against an annular inner wall of the caseband.

[0010] Advantageously, to facilitate direct contact of the fixing joint over its entire height to fix the crystal to the caseband, the caseband comprises a notch or a support in the extension of the annular inner wall of the caseband and in connection with the annular inner surface of the caseband. The fixing joint therefore bears on the notch or support before fixing to the crystal over its entire height. The fixing joint occupies the majority of the space between the notch or support and the opening of the caseband on the upper side. This also allows for full contact of the fixing joint over its entire height against a middle portion of the annular outer wall of the crystal. BRIEF DESCRIPTION OF THE FIGURES

[0011] The aims, advantages and characteristics of a waterproof watch case with a fixing gasket will appear better in the following description in a non-limiting manner with reference to the drawings in which: THE Figures 1A and 1Brepresent in a simplified manner a cross-section of an embodiment of a waterproof watch case, and a partial section of detail of the attachment of the glass to the caseband according to the invention, the Figure 2 represents an elevation view of a detailed partial section before the glass is fixed to the case by means of the fixing joint according to the invention, and the Figures 3A to 3D represent in top view four shapes of case middle of a watch case to receive a circular or square or rectangular glass on the periphery according to the invention, DETAILED DESCRIPTION OF THE INVENTION

[0012] In the following description, all components of a waterproof watch case, in particular of a diving watch, which are well known to a person skilled in the art in this technical field, are described only in a simplified manner.

[0013] THE Figures 1A and 1Brepresent an embodiment of a watch case 1, which can be used for a diving watch. The watch case 1 essentially comprises a crystal 3, which can be made of sapphire or mineral glass, fixed on a part of an upper side of a caseband 2 (dial side) by means of a fixing gasket 5, and possibly a back 4 mounted on a lower side of the caseband 2. A watch movement or module 10 can be arranged in the watch case 1 in a position indicated by the reference 10. At least one control member 9, such as a stem-crown, can be mounted in a sealed manner in a rest position on or through the caseband 2 for setting the time, the date or other functions of the diving watch.

[0014] For fixing the crystal 3 on the upper side of the caseband 2, the annular fixing gasket 5 is arranged between an annular inner wall 22 of the caseband 2 and an annular outer wall 23 of the crystal 3. The fixing gasket 5 is adapted to be fixed in direct contact over its entire height against the annular outer wall 23 of the crystal 3 and against the annular inner wall 22 of the caseband 2. This makes it possible to avoid any stress on a part on the inner side of the watch case or a part on the outer side of the watch case for this fixing gasket 5 to ensure good sealing and facilitate the assembly operation (driving in) and making it difficult to dismantle (drive out) the crystal 3 on the caseband 2.

[0015] The caseband 2 also includes a notch or support 22p on which the annular fixing joint 5 can come to bear to allow it to be in contact over its entire height with the annular outer wall 23 of the crystal 3. A complementary annular inner wall 22' is provided below the notch or annular support 22p to be in connection with the annular inner surface 12 and with a restricted space with the annular outer wall 23 once fixed to the caseband. In the event of strong external pressures on the crystal 3, a part of the fixing joint 5 in compression can occupy a groove 22r made in the inner angle between the support 22p and the annular inner wall 22. The groove 22r is also useful for ensuring good quality mounting of the crystal 3 on the caseband 2 by means of the fixing joint 5.

[0016] Above the notch or support 22p, the fixing joint 5 occupies the majority of the space between the notch or support 22p and the opening of the caseband 2 on the upper side. This still allows for full contact of the fixing joint 5 over its entire height against a middle portion of the annular outer wall 23 of the crystal 3.

[0017] Depending on the dimension of the attachment joint 5 of the crystal 3 on the caseband 2, the attachment joint 5 must be in full contact with the attachment surface of the crystal 3 on the caseband 2. The advantage sought by this present invention is mainly the fact that the force required to carry out a possible removal (disassembly) of the crystal 3 is greater than what is described in the prior art.

[0018] Divers can spend up to several weeks alternating between dives and resting phases in pressurized spaces. Divers then perform a decompression phase. For this, there is an ISO standard (standard 6425) that describes a sequence of tests to which watches are subjected to ensure that they meet the requirements of saturation diving. To do this, watch heads are subjected to an overpressure of helium gas of up to 40 bars for a period of 15 days. This first test concludes with a decompression of the test chamber. The watch heads then undergo a water-tightness test. The watches must remain functional following the test sequence. A risk of the crystal coming loose appears as soon as decompression occurs (this is when the internal pressure can become greater than the external pressure).

[0019] A back 4 may be provided and fixed in a sealed manner to a lower part of the caseband 2 by means of an annular sealing gasket 6 of toric shape preferably placed in a groove 16 of the lower part of the caseband 2 to hold it in position. An annular bearing surface 24 of the back 4 comes into contact with an annular inner surface 32 of the caseband 2 of a shape complementary to the bearing surface 24 when the back 4 is mounted on the caseband 2. The bearing surfaces 24 and inner surfaces 32 are inclined at a determined angle relative to an axis perpendicular to a plane of the watch case 1.

[0020] In the case of a case middle 2 of generally cylindrical shape, the surfaces 24, 32 may be conical in shape and inclined from the outside towards the inside of the watch case 1 at a determined angle relative to a central axis of the watch case 1. This means that the apex of each cone shape is towards the inside of the watch case 1. For a case middle 2 and a back 4 made of a material, such as titanium or a determined type of steel, the angle may be of the order of 43° ± 5° relative to the central axis.

[0021] Generally, the material preferably used for caseband 2 should be a material with high mechanical strength or high yield strength, i.e. greater than 500 MPa. In addition, since there is direct contact with crystal 3, the friction between the two surfaces should be greatly reduced if possible. Caseband 2 can be made, for example, of high-nitrogen stainless steel or grade 5 titanium (Ti6AI4V). For comparison, a standard stainless steel has an elastic limit between 200 and 250 MPa and a Young's modulus between 180 and 210 GPa, while high-nitrogen stainless steel has an elastic limit between 500 and 700 MPa and a Young's modulus between 180 and 210 GPa. Grade 5 titanium has an elastic limit between 800 and 900 MPa and a Young's modulus between 105 and 115 GPa.

[0022] For any shape of watch case, the crystal 3 comprises an annular peripheral surface 13 below the upper annular outer wall 23, configured to come into direct contact against an annular inner surface 12 below the upper annular inner wall 22 of the caseband 2 and in connection with the complementary annular inner wall 22'. The annular peripheral surface 13 of the crystal 3 is inclined at a defined angle smaller than 90° relative to an axis perpendicular to a plane of the watch case 1. Preferably, the annular inner surface 12 is inclined generally from the outside towards the inside of the watch case 1 at the same angle as the annular peripheral surface 13 relative to a central axis. But the annular inner surface 12 of the caseband 2 is inclined with a regular slope towards the center of the watch case.

[0023] If the caseband 2 is of generally cylindrical shape, the annular inner surface 12 may be of conical shape and inclined at a defined angle from the outside towards the inside of the watch case 1 with a regular slope without variation in the profile of the surface. This means that the apex of the cone shape is towards the inside of the watch case 1. The defined angle of inclination of the surface 12 may be of the order of 43° ± 5° relative to the central axis. The annular peripheral surface 13, which may be of a shape substantially complementary to the annular inner surface 12, comprises a domed contact portion with a convex curvature of a first radius R1 defined for contact on a circular annular contact line against the annular inner surface 12 of the caseband 2 of substantially conical shape inclined towards the centre of the watch case.This circular annular contact line is preferably located at mid-height of the annular peripheral surface 13, i.e. in a centered position. The first radius R1 can be chosen to be of the order of 10.7 mm ± 5 mm. This gives a curved portion of the order of 0.03 mm thick on the surface 13, which is sufficient to establish contact with the other surface 12 in a well-centered manner.

[0024] In this case presented, the convex curvature means a bulging portion on the annular peripheral surface 13 to come into direct contact with the annular inner surface 12. The bulging portion is in annular form. With a concave curvature, this means a recessed portion on the annular peripheral surface 13, which is not able to come into contact with the annular inner surface 12 on a circular annular contact line. Therefore, the convex curvature on the annular peripheral surface 13 is chosen, which is desired.

[0025] It is further provided that an upper portion of the annular peripheral surface 13 of the glass 3 comprises a convex curvature of a second radius R2 in connection with the upper annular outer wall 23 of the glass 3, and preferably following the convex curvature of first radius R1. The second radius R2 is less than the first radius R1 of convex curvature of the curved portions for the contact of the surfaces 12 and 13. Preferably, the second radius R2 is of a value more than 10 times less than the first radius R1, for example 0.75 mm ± 0.2 mm. The curvature of radius R2 of the upper portion of the annular peripheral surface 13 of the crystal 3 makes it easier to mount the crystal 3 on the caseband 2 by means of the fixing joint 5. This fixing joint 5 can be made of polyurethane or even crosslinked polyurethane and be of annular shape, for example with a thickness of the order of 0.65 mm ± 0.2 mm and a height of the order of 2.5 mm ± 0.5 mm.

[0026] The fixing joint 5 can also be made of amorphous metal or ceramic.

[0027] It should also be noted that the annular peripheral surface 13 of the crystal 3 may comprise, on the lower part side, a convex curvature of a third radius R3 to avoid having an edge that is too sharp to avoid any contact with a flat of the lower part of the annular inner surface 12 of the caseband 2. The flat may be nearly 3 mm away from the crystal 3. The third radius R3 is less than or preferably equal to the second radius R2. The third radius curvature R3, which is preferably following the convex curvature of the first radius R1, also makes it possible to avoid the risk of chipping the crystal 3.

[0028] With an alloy of amorphous metals based on zirconium in the gasket, a pressure of the order of 10,000 to 80,000 N is applied from the crystal 3 to the caseband 2 at a temperature of the order of 480 °C for a period of 30 - 250 seconds.

[0029] For purely illustrative purposes, it is presented on the Figures 3A to 3D different simplified shapes of case 2 seen from above, dial side. The outer shape of case 2 may be different from the inner shape of case 2.

[0030] To the Figure 3A , the middle 2 is of generally cylindrical shape on the outside and on the inside, the annular inner wall 22 is of cylindrical shape, while the inclined annular inner surface 12 is of generally conical shape.

[0031] To the Figure 3B, the case 2 is generally cylindrical in shape on the outside, and on the inside, at least four vertical flat walls 22 are provided and arranged one after the other in the form of a ring, while the annular inner surface 12 comprises four generally flat plates joined one after the other and inclined towards the center of the watch case.

[0032] To the Figure 3C , the middle 2 is of general parallelepiped shape with four sides on the outside and inside, the annular inner wall 22 is of cylindrical shape, while the inclined annular inner surface 12 is of general conical shape.

[0033] To the 3D figure, the case 2 is of general parallelepipedal shape with four sides on the outside and on the inside, at least four vertical flat walls 22 are provided and arranged one after the other in the form of a ring, while the annular inner surface 12 comprises four generally flat plates joined one after the other and inclined towards the center of the watch case.

[0034] From the description which has just been given, several variant embodiments of the watch case can be designed by those skilled in the art without departing from the scope of the invention defined by the claims. The watch case, by its middle, can have a general shape different from a cylinder.

Claims

1. A water-resistant watchcase (1) comprising at least one glass (3) fitted on a part of a middle (2), the glass (3) comprising an annular outer wall (23) to be attached by means of a bow-shaped fastening joint (5) on the watchcase (1) to an annular inner wall (22) of the middle (2), and between the annular outer wall (23) and the centre of the watch case (1), the glass (3) comprising an annular peripheral surface (13) inclined at a defined angle smaller than 90° relative to an axis perpendicular to a plane of the watch case (1) and directly contacting an annular inner surface (12) of the middle (2), the annular inner surface (12) being inclined at an angle similar to the angle of inclination of the annular peripheral surface (13) and arranged below the annular inner wall (22) of the middle (2), the fastening joint (5) being designed to be attached in direct contact over its entire height, prior to any external compression, against the annular outer wall (23) of the glass (3) and against the annular inner wall (22) of the middle (2), characterised in that the annular peripheral surface (13) comprises a portion of a domed contact surface having a convex curvature with a first radius (R1) defining an annular line of contact against the annular inner surface (12) of the middle (2).

2. The watchcase (1) according to claim 1, characterised in that the part of the middle receiving the glass comprises a notch or support (22p) on which the bow-shaped fastening joint bears to ensure direct contact of the fastening joint over its entire height against the annular outer wall (23) of the glass and the annular inner wall (22) of the middle (2).

3. The watchcase (1) according to claim 2, characterised in that the fastening joint (5) is positioned in its entirety from the notch or support (22p) and the outer opening of the middle (2).

4. The watchcase (1) according to one of claims 1 and 2, characterised in that the annular inner wall (22) and the annular outer wall (23) are cylindrical or polygonal in shape.

5. The watchcase (1) according to claim 2, characterised in that an annular groove (22r) is made in the inner corner between the support (22p) and the annular inner wall (22) to partially receive the fastening joint on compression.

6. The watchcase (1) according to any of the preceding claims, characterised in that the fastening joint (5) is made of polyurethane or even of cross-linked polyurethane.

7. The watchcase (1) according to any of the preceding claims, characterised in that the fastening joint (5) is made of amorphous metal or of ceramic.