CH671495B5 - - Google Patents

Abstract

Watch case has a frame with a plastic periphery and a radial annular shoulder, a base, a metal ring covering the frame and its outer face, a recess in the ring receiving the shoulder so that the ring and frame are inseparable, and an annular recess between the ring and the frame receiving a seal. The plastic is pref. a copolymer of acrylonitrile, butediene, and styrene, or acrylonitrile, styrene, and acrylic ester, or styrene and acrylonitrile. It may alternatively be of polyamide and glass fibres.

Description

DESCRIPTION The present invention relates to a watch case comprising a middle part of which at least one peripheral portion is made of plastic, a bottom a metal bezel covering the middle part and extending over at least part of the outer edge. presented by the middle part, and sealed assembly means of the middle part and the bezel.

It also relates to an assembly intended to form this watch case as well as to an assembly process using this assembly.

Document JP-B-55-18 958 already describes a watch case meeting the generic definition given above. The plastic case back carries a discoid back made of a piece with a proper middle part. This case back is overmolded inside a metal bezel, the latter comprising hooking teeth making the whole non-removable once the injection of the plastic has been carried out. To ensure the seal between the backband and the bezel, there is, before injection, a seal on a shoulder of the bezel. This seal then comes compressed during the injection of the bottom, which ensures the desired seal.

45 This approach is unsatisfactory for at least three reasons. First, the seal may be damaged by the high temperature of the liquid material which compresses it. One could then choose for the seal a material particularly resistant to temperature, but so this material would not necessarily be the best with regard to the function to be ensured, that is to say the sealing of the box. Then the proposed seal, surrounding only two internal shoulders of the telescope, is not sufficiently localized or guided which can cause its displacement, 55 or even its tearing, at the time of the injection of the plastic material. Finally, the overmolding process, as precise as the mold is made, leaves flows on the parts which should not be covered - here the visible part of the telescope - which requires subsequent cleaning or deburring 60, as many operations which can be considered expensive.

Although regarding the waterproof fixing of an organic glass crystal to a watch case, one could use, to assemble a bezel to a middle part, the method proposed by patent application FR-A-2 491 644. This application proposes to provide the bezel with a groove facing the inside of the bezel. The ice is supported on a shoulder of this bezel and a punch is applied

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annularly heated on the periphery of the glass to plastically deform it and thus penetrate a part of the plastic material inside the groove formed in the telescope. In conjunction with this, a seal is compressed between the telescope and the glass. Such a method certainly makes it possible to obtain a tight fixing of the crystal by dispensing with any mechanical fixing member or any use of glue, but it gives unsatisfactory results from an aesthetic point of view. Indeed, the deformation due to the application of the annular punch occurs on the front face of the glass. In addition, these glass fixing techniques involve significant mechanical forces to obtain the deformation of the material. These forces induce internal tensions in the final product which alter the aging qualities of the box fitted with its glass.

An object of the invention is to provide a waterproof, reliable and inexpensive watch case. This object is achieved by the assembly means described in claim 1.

Another object of the invention is to provide an assembly intended to form a waterproof watch case, an object which is achieved by the assembly defined in claim 9.

Another object of the invention is to provide a method of assembling the assembly defined above, method which is the subject of claim 12.

The invention will now be explained in the description which follows, given by way of example, with the aid of the drawing which illustrates it and in which:

FIG. 1 is a partial section in a watch case assembled according to a first embodiment of the invention,

FIG. 2 is a partial section in a watch case according to the invention before assembly of the elements constituting it,

Figure 3 is an enlargement of what is shown in circle III of Figure 2,

FIG. 4 is a resumption of FIG. 1 further showing the watch completely assembled,

FIG. 5 is a partial section in a watch case assembled according to a second embodiment of the invention,

FIG. 6 is a top view of the plastic bandage fitted to the middle part shown in FIG. 5 and

Figure 7 is a section on Figure VII-VII of Figure 6.

Figure 1 shows a watch case assembled according to a first embodiment of the invention. It essentially comprises a case back 2 made of plastic, ■ a metal bezel 1 and a seal 4.

The backband, made in one piece, includes a first part, discoid, forming the back part 9 and a second, annular part, forming the back part 10. This back part is of the monocoque type where the movement is mounted by the top of the middle 10. This middle is equipped with an enlargement circle 11 and supports 12 to support the movement. An opening (not shown in the drawing) can be made in the bottom 9 to change the battery. This opening will then be closed by a cover. The monocoque backband has the advantage of simplifying the mounting of the watch on automatic transfer machines. Indeed, all the loading operations take place on the same side, the top of the watch, and there is no need to turn the part over to equip it with its constituent components. This embodiment also has the advantage of offering a bottom which takes up little space in thickness.

Making the plastic case back also has the great advantage of offering a much cheaper part than if this back case was made of steel. Indeed, this part, by the complication it presents and by the precision with which it must be executed, is expensive when it is made of metal because it requires numerous and expensive machining operations which must be done on each part taken individually. With the plastic, complications and precision are transferred to the injection mold, which will allow a large number of parts to be produced with the desired finish and without recovery operations after injection. The fact that the enlargement circle can be molded at the same time as the backband also has an obvious advantage since an additional part can be avoided. It will also be noted that allergy phenomena, causing irritation of the skin by a steel bottom, will no longer occur with a plastic bottom.

The fact remains that a plastic case back does not only have advantages if only by the mediocre aesthetic appearance of its visible parts (middle edge and bezel). This gives the watch a cheap impression which it would be desirable to avoid especially for a mid-range watch. On the other hand, it will be understood that these visible parts are very stressed by the external mechanical stresses which make them very sensitive to scratches, hence very rapid degradation of the aesthetic appearance. To avoid this, the watch proposed here comprises a metal bezel 1 covering the middle part 10 and extending over at least part of the outer edge of said middle part. This bezel can be made of steel, whether or not covered with a decorative coating (hard materials, browning, etc.).

To assemble the case back to the bezel, several solutions can be envisaged, in particular those which have been discussed in connection with the documents cited above, but which are not suitable for the reasons mentioned. One could also use a conventional or notched closure of the kind described in document CH-A-230 526 where the bottom is provided on its periphery with a rim having hooking rods cooperating with grooves made in the inside of the middle and this in such a way that the base is maintained in a state of forced tension and tends to crush a seal placed between the base and the middle. This latter way of doing things is not satisfactory in the case where the base is made of plastic. It is found in fact that the seal is not guaranteed, because the anchoring can present irregular forces on the joint which leads to a pinching of this joint which is not constant over its entire periphery. On the other hand, the grooves carried by the metal middle may have cutting edges capable of damaging the hooking strips made of plastic.

Thus, according to the invention and if we refer again to Figure 1, the sealed assembly means of the caseband 2 and the bezel 1 comprise a first annular housing 6 extending radially in the bezel 1 and inside which is housed an annular protuberance 13 made in one piece with the case back 2. Thanks to the shape given to the housing 6 and the protuberance 13 which is housed there, the case back 2 is inseparable from the bezel 1. Still according to the invention, the assembly means also comprise a second annular housing 7 which is defined jointly by the caseband and the bezel and a seal 4 occupying this second housing. This seal seals the case against liquids which could be introduced between the middle part 10 and the bezel 2, then penetrate inside the watch into the region of the dial.

Figure 1 shows in particular that the second annular housing 7 is located between the bezel 2 and the top 14 of the middle part 10 and is formed by a groove made in s

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the bezel 2, throat closed at the top 14 of the middle part 10. Without it being necessary to represent it by a figure, it will be readily understood that it is at the top 14 of the middle part 10 that could be found the groove, the latter then being closed by a flat upper edge presented by the bezel.

The case back is therefore made of plastic. We then have a whole range of materials likely to be suitable for this production. One could use a material chosen from the group comprising acryl butadiene styrene (ABS), acryl sytene acryl-ester (ASA) and styrene acryl nitrile (SAN). It could also be a polyamide loaded with beads or glass fibers.

The box which has just been described is perfectly waterproof and has excellent reliability. In fact, the attachment of the case back to the bezel cannot be dismantled, the seal remains compressed in its housing in a constant manner whatever the stresses which could be exerted on the case such as shocks or variations in temperature for example. In addition to that it is inexpensive, while ensuring tight dimensional tolerances which are well reproducible as already mentioned above.

The watch case which is the subject of the invention is produced from an assembly comprising a case-back 2, a bezel 1 and a gasket 4 which are presented, before assembly, in the manner which will now be described, different components appearing as illustrated in FIGS. 2 and 3, FIG. 3 being an enlargement of what is shown in circle III of FIG. 2.

The outer periphery of the middle part 10 of the back part 2 has a stepped structure which comprises a first lower wall 15, a second upper wall 16 and a bevelled step 17 forming an acute angle a with the second wall 16, this step having thus a point-shaped edge 18. The bezel 1 comprises first 19 and second 20 inner sides adapted respectively to match the shape of the first and second walls of the middle part. The first housing 6 formed in the bezel 1, already described above, is located between the sides 19 and 20. Against a horizontal face 21 of the housing 6 is supported the edge 18 in the form of a point presented by the edge of the middle part 10, when the middle part 2 is introduced into the bezel 1. The assembly defined by FIGS. 2 and 3 also includes the gasket 4 disposed in the second housing 7 of the bezel 1.

The bevelled step 17 can be arranged all around the middle part 10. If the movement introduced into the watch has a time-setting rod, the beveled step 17 can be interrupted in the vicinity of this rod to let a barrel pass through. integral part of the case back 2, said barrel receiving said rod. Similarly the beveled step 17 could be discontinuous and have several segments arranged annularly around the edge of the middle. One could also imagine, without departing from the present invention, that the first housing is not continuous, but arranged in several grooves made in the telescope, each of the grooves receiving a beveled segment 17. This way of doing things could serve to angularly position the caseback 2 relative to the bezel 1.

It now remains to explain how we proceed to assemble the watch case according to the invention.

We start by introducing the backband 2 into the bezel 1 until the point-shaped edge 18 comes to abut against the face 21 of the first housing 6 of the bezel 1 (see this starting position in Figures 2 and 3). By resting the telescope 1 on a fulcrum, pressure is then exerted on the backband 2 by means of an onotrode 22 providing mechanical vibrations at high frequency and this in the direction of the arrow 23. The ultrasound energy thus produced will have the effect of first melting the edge 18 in the form of a point on which all the energy produced by the sonotrode is concentrated, then all the beveled step 17 and even of the material located below. this step, the molten material filling the first housing 6 of the bezel 1. Finally, the pressure is interrupted when the top 14 of the middle part 10 comes into contact with the bezel 1. At this time the seal 4 is compressed in the second housing 7 and the operation is completed which results in a sealed and non-removable assembly. The box then appears i5 as shown in Figure 1.

It will be mentioned that it would also be possible to apply the sonotrode to the bezel, the fulcrum then being made on the backband. This would lead to similar results.

FIG. 4 is a partial sectional representation at 12 o'clock of the fully assembled watch using the case which is the subject of the invention. This figure repeats what is shown in Figure 1 for the single box. Having said box, we start by mounting the movement 24, an outer edge of which rests on the shoulder 12 of the backband 2. We then place the dial 25 and the hands 26. We introduce the flange 27 into the inner periphery of the bezel 1. Finally, the glass 28, sealed by the sealing band 29, is chased onto the flange 27. This gives a watch 30 with a plastic monocoque case-back and covered with a metallic bezel, a watch having an appearance very neat and a very good seal. It will be noted that a metallic bracelet will be attached according to a conventional embodiment and which has not been shown in the drawing. •

Figure 5 shows a watch case assembled according to a second embodiment of the invention. It essentially comprises a middle part 30 of which at least one peripheral portion is made of plastic. Here the middle 40 is no longer made entirely of plastic but is composed of a metal ring 32 surrounded by a bandage 31 made of plastic. In this construction we also see that the bottom 33 of the case is independent of the middle and that it is assembled there by a notch device for example 45.

FIG. 5 shows, however, that here, too, we are dealing with assembly means similar to those described in connection with the first embodiment. There is indeed the same first annular housing 6 extending radially 50 in the bezel 1, the same annular projection 13 made in one piece with the portion 31 of the middle part made of plastic and the same second annular housing 7 in which houses a seal 4.

55 The bandage 31 is shown alone in FIGS. 6 and 7. Here it is a split ring at 35 and which has three zones or bevelled steps 17. The ring is pierced with a hole 36 through which the rod will pass to wind up. As can be clearly seen in FIG. 7, which is a section according to FIG. N0 VII-VII of FIG. 6, the bandage also has an outside circumference in the form of a staircase with its first lower wall 15, its second upper wall 16 and its bevelled step 17 forming an acute angle (a) with the second wall and having a point-shaped edge 18. The first 65 and second walls 15 and 16 are adapted respectively to match the shape of the first 19 and second 20 inner sides of the telescope 1, as shown in Figure 5. The assembly is therefore carried out in the same way as that

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described with reference to FIGS. 1 to 4 and according to the same method which uses ultrasound. There is therefore no reason to return to it here.

Figures 5 to 7 show that the bandage 31 is simply tightened around the ring 32 by the fact of its elasticity. A trapezoidal boss 37, disposed inside the bandage 31, cooperates with a housing of the same shape made in the ring 32. The slot 35 of the bandage allows the latter to be slightly opened and put in place on the ring. This bandage could however be molded directly on the ring.

Contrary to what has been said about the first embodiment, this second embodiment has a more conventional embodiment in the sense that the movement is introduced from below and that the case is closed by a screwed or

notch. The ice rests on a flange which is made in one piece with the ring 32.

This second embodiment is particularly advantageous when it comes to assembling two metal parts of different natures, for example steel for the middle and hard metal for the bezel. We know that hard metal (TiN, WC, for example) has dimensional dimensions which cannot be kept within tight tolerances in the raw state, which generally means that the part must be machined in a subsequent step. . This step is no longer. necessary if the bandage proposed by the invention is used since it is this bandage which will accommodate these tolerances, the middle part being itself sufficiently precise (by bar turning for example) to receive the movement and the bottom.

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2 sheets of drawings

Claims (5)

1. Watch case comprising a middle part (10, 30) of which at least one peripheral portion (10, 31) is made of plastic, a base (9, 33), a metal bezel (1) covering the middle part and s' extending over at least part of the outer edge presented by the middle part, and sealed assembly means of the middle part and of the bezel, characterized in that the said assembly means comprise a first annular housing (6) s' extending radially in the bezel, an annular protuberance (13) made in one piece with the portion of the middle part made of plastic material and extending radially inside the first housing, said protuberance and said first housing being arranged in such a way so that the middle part and the bezel are inseparable, a second annular housing (7) defined jointly by said middle part and said bezel and a seal (4) occupying said second housing. 2. Watch case according to claim 1, characterized in that the middle part (10) is made entirely of plastic material together with the base (9) to form a base-middle part (2) in one piece. 3. Watch case according to claim 1, characterized in that the middle part (30) is a metal ring (32) surrounded by a bandage (31) made of plastic. 3 671,495 G 4. Watch case according to claim 2 or claim 3, characterized in that the plastic is a material chosen from the group comprising acryl butadiene styrene (ABS), acryl styrene acryl-ester (ASA) and styrene acryl nitrile (SAN). 5. Watch case according to claim 2 or claim 3, characterized in that the plastic material is polyamide loaded with beads or glass fibers. 6. Watch case according to claim 1, characterized in that the second housing (7) is located between the bezel (1) and the top (14) of the middle part (10). 7. Watch case according to claim 6, characterized in that the second housing (7) is a groove formed in the bezel (1). 8. Watch case according to claim 6, characterized in that the second housing (7) is a groove made in the top (14) of the middle part (10). 9. Assembly intended to form a watch case comprising a middle part (10, 30) of which at least one peripheral portion (10, 31) is made of plastic, a bezel (1) and a seal (4), characterized by the fact that the peripheral portion made of plastic material has an external circumference in the form of a staircase comprising a first lower wall (15), a second upper wall (16) and a bevelled step (17) forming an acute angle (a ) with the second wall and having an edge (18) in the shape of a point, that the bezel includes first (19) and second (20) interior flanks adapted respectively to match the shape of the first and second walls of the middle part, a first housing (6) being disposed between said flanks and against a face (21) of which bears said edge in the shape of a point when the middle is introduced into the bezel, and the seal is placed inside a second housing (7) formed in the top of the middle or in the part of the bezel facing at the top of the middle. 10. The assembly of claim 9, characterized in that the middle part (10) is made entirely of plastic material together with the base (9) to form a base-middle part (2) in one piece. 11. The assembly of claim 9, characterized in that the middle part (30) is a metal ring (32) surrounded by a bandage (31) made of plastic. 12. Method of assembling a watch case using the assembly defined according to claim 9, characterized in that it comprises the succession of the following operations: - the middle part (10, 30) is introduced into the bezel (1) 5 until the point-shaped edge (18) presented by the middle part abuts against the face (21) of the first housing (6) of the bezel, - A pressure (23) is exerted on the middle part or on the bezel by means of a sonotrode (22) supplying mechanical vibrations at high frequency to produce the fusion of the beveled step (17), the molten material filling the first seat of the telescope and - The pressure is interrupted when the top (14) of the middle part comes into contact with the bezel, the i5 seal (4) then being compressed in the second housing (7), the box finally having a non-removable assembly.