HK1095640B - Watch including means for improving the shock resistance of the crystal - Google Patents

Description

Watch comprising means for increasing the shock resistance of the crystal

Technical Field

The invention relates to a watch comprising a case fitted with an intermediate part and a crystal fixed to the intermediate part by means of a peripheral bezel.

More specifically, the invention relates to a watch comprising a case comprising a middle part, a crystal and a display dial, wherein the crystal comprises an outer radial flange axially abutting against the middle part, the radial flange being axially retained by a peripheral bezel fixed to the middle part to abut against the middle part, the bezel comprising a lower annular radial surface axially abutting against the top face of the flange.

Background

Watches are known in which the bezel is used to fix the crystal to the intermediate part. For example, U.S. patent No.3688492 discloses and illustrates a watch including a flat crystal secured to an intermediate member by pressing a bezel into a groove formed in the top surface of the intermediate member. The bezel includes an internal shoulder that axially abuts the top radial surface of the radial flange of the crystal to hold the crystal against the intermediate member.

With this type of watch, when axial shocks are applied to the crystal, for example when the watch falls from the height of the table, the stresses are mainly axial due to the flat outer surface of the crystal. Thus, the stress may be absorbed axially by the intermediate component at the surface of the crystal that abuts axially against the intermediate component. Thus, the crystal works mainly in an axially compressed state without any bending occurring.

This is not the case when the watch is provided with a convex hemispherical crystal. In fact, at this time, an axial shock is applied to the central portion of the surface glass, causing the surface glass to be severely deformed, the surface glass tends to be bent and collapsed at the central portion thereof, and the flange of the surface glass tends to be moved outward.

These deformations of the surface glass may lead to cracks or even fractures. These cracks are generated in particular by the contact of the central portion of the crystal with the end of the arbour of the display hand of the watch or by internal stresses in the material forming the crystal.

In the above document, if axial stress concentrated on the central portion of the crystal causes the flange to move radially outwards, the crystal will abut against the top end portion of the bezel, which will exert a torsional stress on the bezel that compromises its mechanical resistance. Further, since the bezel is pressed toward the inside of the case via the inner edge of the bezel, a torsional stress acts in a direction in which the bezel is detached, and there is a high possibility that the crystal is detached.

Disclosure of Invention

The object of the present invention is to eliminate these disadvantages in a simple and economical manner.

To this end, the invention proposes a wristwatch of the type described above, characterized in that the flange comprises a convex outer peripheral surface generally complementary to a concave inner surface of the bezel, the inner surface being arranged opposite the outer peripheral surface and below a radial abutment surface of the bezel, the outer peripheral surface radially abutting against said inner surface when the crystal is subjected to axial vibrations.

Due to the arrangement of the invention, the bending stress is reduced when axial vibrations occur, which reduces the risk of cracks. Therefore, the crystal of the watch according to the invention has improved shock resistance.

Furthermore, it is generally necessary to provide pre-centering means on the flange of the crystal in order to position the crystal appropriately with respect to the intermediate part before the bezel is fitted; otherwise, the crystal may be damaged by the bezel or the bezel cannot be fitted. These pre-centering devices can lead to premature breakage of the crystal due to severe deformation caused by axial shock.

To overcome this problem, according to an advantageous feature of the invention, on the side of the inner peripheral edge of the flange, the bottom radial face of the flange comprises at least one downwardly extending positioning lug between the dial and the inner axial wall of the intermediate part, and the radial spacing between this lug and the inner axial wall of the intermediate part is greater than the radial spacing between the outer face of the flange and the inner face of the bezel, so that in the event of an axial shock the outer face of the flange abuts radially against the inner face of the bezel before the lug contacts the inner axial wall of the intermediate part.

According to another feature of the invention, the outer surface of the flange and the inner surface of the bezel have complementary frustoconical shapes.

These shapes enable optimum shock strength to be obtained.

According to another feature of the invention, the intermediate part comprises an outer peripheral edge comprising a concave inner wall of substantially frustoconical shape of increasing diameter downwards, the bezel comprises an annular heel which is pressed axially from above downwards into the intermediate part so that the outer peripheral wall of the heel presses radially against the inner wall of the edge, and the inner surface of the bezel is formed by the inner wall of the heel.

This feature enables the intermediate part to carry the stresses exerted by the crystal on the inner surface of the bezel.

According to another feature of the invention, the outer wall of the heel has a frustoconical shape defining an angle smaller than the angle defined by the inner surface of the bezel.

This feature means that the bezel can be pressed into the intermediate part without any risk of overloading the crystal.

Drawings

Other characteristics and advantages of the invention will become better apparent from a reading of the following detailed description, given by way of non-limiting example with reference to the accompanying drawings, in which:

figure 1 is an axial section view schematically showing a watch according to the teachings of the present invention;

figure 2 is an enlarged view of a detail of figure 1, schematically showing a circumferential portion of the watch in rest condition;

fig. 3 is a view similar to fig. 2, showing a circumferential portion of the watch during an axial shock.

Detailed Description

Fig. 1 shows a watch 10 made in accordance with the teachings of the present invention.

Watch 10 includes a case 12 including a middle part 14, a crystal 16 and a display dial 18. Case 12 is also fitted with a peripheral bezel 20 which is snap-fitted into middle part 14 to axially retain crystal 16 against middle part 14.

Here, the outer surface of the crystal 16 is generally convex hemispherical in shape.

Case 12, here generally cylindrical, houses a watch movement 22, which is arranged below dial 18 and controls an analog display device 24, here formed by hands 24 rotatably mounted about a central vertical axis a 1.

In the following description, the vertical direction along the axis a1 of the hand 24, here corresponding to the axis of the case 12, will be used in a non-limiting manner.

According to the embodiment illustrated herein, the central projection 26 of the analog display device 24 is formed by the end 26 of the second wheel spindle carrying the second hand.

Of course, according to an alternative embodiment (not shown), the projection 26 may be formed by another element, such as a fixed central projection or the central portion of the pointer.

As shown in particular in fig. 2 and 3, the intermediate part 14 comprises an outer circumferential edge 28 defining a concave substantially frustoconical inner wall 30, the diameter of which increases downwards.

Bezel 20 includes a lower annular heel 32 that is pressed axially into middle part 14 from the top down so that an outer circumferential wall 34 of boss 32 is pressed radially against inner wall 30 of rim 28.

The crystal 16 comprises an outer radial flange 36 which, by means of its lower radial face 38, bears axially against an annular radial bearing surface 40 of the intermediate element 14. The radial bearing surface 40 is defined inwardly by an inner axial wall 42 of the intermediate member 14.

Bezel 20 includes a lower annular radial surface 44 that axially abuts a top surface 46 of flange 36, enabling flange 36 to be tightly held between radial surface 44 of bezel 20 and radial bearing surface 40 of intermediate member 14 to hold crystal 16 axially against intermediate member 14.

Radial abutment surface 44 is provided in a portion of bezel 20 above heel 32.

Preferably, the radial bearing surface 40 is substantially axially aligned with the radial abutment surface 44 of the bezel 20.

According to the embodiment shown herein, the intermediate part 14 comprises an annular groove 48 radially interposed between the radial bearing surface 40 and the outer circumferential edge 28, which receives an annular sealing gasket 50 of the "O-ring" type. The sealing gasket 50 is compressed between the intermediate part 14 and the lower radial face 38 of the flange 36.

According to the teachings of the present invention, flange 36 includes a convex outer circumferential surface 52 generally complementary to an opposing concave inner surface 54 of bezel 20 disposed below lower radial abutment surface 44 of bezel 20, which radially abuts against said inner surface 54 when crystal 16 is axially vibrated.

In the rest state, as shown in fig. 2, there is a radial gap D2 between the outer surface 52 of the flange 36 and the inner surface 54 of the bezel 20.

According to another embodiment, this radial gap D2 may be zero, which is the case for axial vibrations as shown in fig. 3.

Advantageously, the lower radial face 38 of the flange 36 comprises, on the side of the inner circumferential edge 56 of the flange 36, at least one positioning lug 58 extending downwards. Further, the radial spacing D1 between the projections 58 and the inner axial wall 42 of the middle member 14 is greater than the radial spacing D2 between the outer surface 52 of the flange 36 and the inner surface 54 of the bezel 20.

Preferably, the crystal 16 comprises a plurality of projections 58 angularly distributed in a regular manner. These projections 58 each have the general shape of a truncated conical pin intended to cooperate by sliding with an adjacent edge of the middle part 14 and/or with an outer peripheral edge 60 of the dial 18, so as to pre-centre the crystal 16 with respect to the middle part 14 when the crystal 16 is mounted on the case 12 before the bezel 20 is fitted.

It should be noted that when the projection 58 is associated with a notch provided in the outer circumferential edge 60 of the dial 18, the projection 58 may also indicate (the position of) the crystal 16 angularly relative to the dial 18.

It is also preferred that the outer surface 52 of the flange 36 and the inner surface 54 of the bezel 20 have complementary frustoconical shapes to better distribute mechanical stresses when the crystal 16 is subjected to axial shock. The diameter of these frustoconical surfaces increases downwardly.

The inner surface 54 of bezel 20 is formed by the inner wall of heel 32.

Advantageously, outer wall 34 of heel 32 has a frustoconical shape defining an angle with respect to axis a1 that is less than the angle defined by inner surface 54 of heel 32. This feature avoids stressing the face glass 16 when pressing the bezel 20 into the middle part 14.

Here, the intermediate part 14 comprises an annular radial surface 62 interposed between the annular groove 48 and the inner wall 30 of the rim 28. Once bezel 20 is pressed into middle part 14, heel 32 abuts axially with its lower free end against this radial surface 62, which also avoids overloading crystal 16 once the pressing operation is completed.

According to the embodiment shown herein, the projection 58 is slightly radially outwardly offset with respect to the inner circumferential edge 56 of the flange 36, which defines an annular interior 64 in the lower radial face 38 of the flange 36 that axially abuts against a top face 66 of the dial 18.

We will now explain the behaviour of the watch 10 when the crystal 16 is subjected to axial vibrations.

In fig. 1 and 2, the watch 10 is at rest, with the crystal 16 not deformed.

In fig. 3, the axial vibration is applied to the crystal 16 from the top down.

The central portion of the crystal 16 deforms downward and tends to move closer to the central protrusion 26. This deformation causes the flange 36 to slide radially outward until the outer surface 52 of the flange radially abuts the inner surface 54 of the bezel 20.

At this stage, the mechanical stresses caused by the vibrations are distributed in the material of the crystal 16 according to the abutment area.

Advantageously, since the crystal 16 abuts radially against the bezel 20, the internal stress in the crystal 16 is minimized by being absorbed by the bezel 20, which firmly abuts the crystal 16 against the intermediate member 14 to limit the bending of the crystal 16 in the central portion thereof.

Thanks to the arrangement according to the invention, the radial sliding of the flange 36 is stopped before the projection 58 contacts the intermediate part 14, which reduces the risk of breakage of the crystal 16. Furthermore, stopping the radial sliding of the flange 36 limits the axial movement of the central portion of the crystal 16 towards the central protrusion 26, which also reduces the risk of breakage of the crystal 16.

Claims (10)

1. Watch (10) comprising a case (12) including a middle part (14), a crystal (16) and a display dial (18), in which the crystal (16) includes an outer radial flange (36) which axially abuts against the middle part (14), the outer radial flange (36) being axially retained by a peripheral bezel (20) fixed to the middle part (14) to abut against the middle part (14), the bezel (20) including a lower annular radial surface (44) and an annular heel (32), the radial surface (44) axially abutting against a top surface (46) of the flange (36), the heel (32) being pressed axially from above downwards into the middle part (14) so as to radially press an outer circumferential wall (34) of the heel (32) against an inner wall (30) of an outer circumferential edge (28) of the middle part (14),

characterized in that the flange (36) comprises a convex outer peripheral surface (52) generally complementary to a concave inner surface (54) of the bezel (20), the inner surface (54) being disposed opposite the outer peripheral surface (52) and below a radial abutment surface (44) of the bezel (20) and radially abutting against said inner surface (54) when the crystal (16) is subjected to axial shock; the inner surface (54) of the bezel (20) is formed by the inner wall of the heel portion (32).

2. Watch according to claim 1, characterised in that the lower radial face (38) of said flange (36) comprises, on the side of the inner peripheral edge (56) of the flange (36), at least one downwardly extending positioning lug (58), the lug (58) being located between the dial (18) and the inner axial wall (42) of the intermediate part (14); and the radial spacing (D1) between the projection (58) and the inner axial wall (42) of the intermediate part (14) is greater than the radial spacing (D2) between the outer circumferential surface (52) of the flange (36) and the inner surface (54) of the bezel (20), so that in the event of an axial shock the outer circumferential surface (52) of the flange (36) radially abuts against the inner surface (54) of the bezel (20) before the projection (58) contacts the inner axial wall (42) of the intermediate part (14).

3. Watch (10) according to any one of the preceding claims, characterised in that the outer peripheral surface (52) of said flange (36) and the inner surface (54) of said bezel (20) have complementary frustoconical shapes.

4. Watch (10) according to claim 1 or 2, characterised in that the inner wall (30) of the outer peripheral edge (28) of the intermediate part (14) is concave and frustoconical with a diameter increasing downwards.

5. A wristwatch (10) according to claim 3, characterized in that the outer peripheral wall (34) of the heel (32) has a frustoconical shape defining an angle smaller than the angle defined by the inner surface (54) of the bezel (20).

6. Watch (10) according to claim 1 or 2, characterised in that the lower free end of said heel (32) axially abuts against an associated bearing surface (62) provided in the intermediate part (14).

7. A wristwatch (10) according to claim 1 or 2, characterized in that said intermediate member (14) comprises an annular radial bearing surface (40), the radial bearing surface (40) being axially aligned with a radial abutment surface (44) of the bezel (20), so that the flange (36) is held axially clamped between said annular radial bearing surface (40) and said radial abutment surface (44); the radial bearing surface (40) is defined inwardly by an inner axial wall (42) of the intermediate member (14).

8. Watch (10) according to claim 7, characterised in that said intermediate part (14) comprises an annular groove (48) interposed between the radial bearing surface (40) and the outer peripheral edge (28), which receives a sealing gasket (50) compressed between the intermediate part (14) and the flange (36).

9. A wristwatch (10) according to claim 1 or 2, characterized in that the outer surface of the crystal (16) is generally convex hemispherical in shape.

10. Watch (10) according to claim 1 or 2, characterised in that said case (12) houses a watch movement (22) equipped with analogue display means (24).