CH705905B1 - Membrane shockproof bearing for a timepiece. - Google Patents

Abstract

The invention relates to a shock-absorbing bearing for an axle of a moving part of a timepiece, said axle comprising a shank, said bearing comprising a support (101) provided with a housing receiving a pivot system (105) comprising a pivot module (109) into which the rod can be inserted and elastic means (107) arranged so that the pivot module is mounted suspended and to exert on the pivot module at least one axial force. The elastic means comprise a membrane spring.

Description

The present invention relates to a shock bearing for an axis of a mobile of a timepiece. The axis comprises a shank, comprising a support. The support is provided with a housing designed to receive a pivot system in which the shank is inserted. The shockproof system further comprises elastic means arranged to exert on said pivot system at least one axial force.

The technical field of the invention is the field of fine mechanics.

TECHNOLOGICAL BACKGROUND

The present invention relates to bearings for timepieces, more particularly of the type making it possible to absorb shocks. Manufacturers of mechanical watches have long designed many devices allowing an axis to absorb the energy resulting from an impact, in particular from a side impact, by abutment against a wall of the hole in the base block through which it passes. , while allowing momentary movement of the rod before it is returned to its rest position under the action of a spring.

Figure 1 illustrates a so-called inverted double cone device which is currently used in timepieces on the market.

A support 1, the base of which has a hole 2 for the passage of the balance shaft 3 terminated by a shank 3a, makes it possible to position a bezel 20 in which are immobilized a pierced stone 4 crossed by the shank 3a and a counter-pivot stone 5. The bezel 20 is held in a housing 6 of the support 1 by a spring 10 which comprises in this example radial extensions 9 compressing the counter-pivot stone 5. The housing 6 comprises two bearing surfaces 7, 7a in form of inverted cones on which rest additional bearing surfaces 8, 8a of the bezel 20, said bearing surfaces having to be executed with very high precision. In the event of an axial impact, the pierced stone 4, the counter-pivot stone 5 and the balance shaft move and the spring 10 acts alone to bring the balance shaft 3 back to its initial position. The spring 10 is sized to have a limit of movement so that beyond this limit, the balance shaft 3 comes into contact with stops 14 allowing said shaft 3 to absorb the shock, which the rods 3a of axis 3 cannot be done under penalty of breaking. In the event of a radial shock, that is to say when the end of the shank unbalances the bezel 20 outside its plane of rest, the spring 10 cooperates with the complementary inclined planes 7, 7a; 8, 8a to refocus the bezel 20. Such bearings have for example been sold under the Incabloc® brand. These springs can be made of phynox, CuBe or brass and are manufactured by traditional cutting methods.

[0006] However, such an anti-shock system does not provide optimal damping in all circumstances. First, the so-called inverted double cone device and its unsuspended architecture do not offer perfect recentering. Indeed, this architecture leads to the presence of friction between the bezel supporting the pierced stone and the counter-pivot stone, and the support. This friction therefore slows down the refocusing movement of the bezel and can block this movement so that the bezel does not return to its initial position causing a shift in the axis.

[0007] Furthermore, shock-absorbing systems are known comprising a support whose base has a hole for the passage of the balance shaft terminated by a shank, the support making it possible to position a bezel in which are immobilized a pierced stone crossed by the shank and a counter-pivot stone 5. The bezel is held in a housing of the support by an arm spring so as to be suspended

SUMMARY OF THE INVENTION

[0008] The object of the invention is to overcome the drawbacks of the prior art by proposing to provide a more efficient anti-shock bearing for a timepiece which is more resistant to shocks and which is simpler and less expensive to produce.

[0009] To this end, the invention relates to a shock-absorbing bearing for an axis of a mobile of a timepiece, said axis comprising a shank, said bearing comprising a support provided with a housing provided to receive a pivot system comprising a pivot module in which the rod is inserted and elastic means arranged to allow said pivot module to be mounted suspended and to exert on said pivot module at least one axial force, characterized in that the elastic means comprise a diaphragm spring.

A first advantage of the present invention is to obtain a pivot system whose replacement is perfect. Indeed, as the membrane spring is suspended, there is no contact or friction between said membrane spring and the support and thus nothing disturbs the recentering.

Another advantage of the present invention is that a membrane spring has less complex shapes than an arm spring, thus simplifying manufacture.

Advantageous embodiments of this shock bearing are the subject of the dependent claims.

[0013] In a first advantageous embodiment, the shock-absorbing bearing further comprises fastening means for fixing the pivot system to the support.

[0014] In a second advantageous embodiment, the elastic means and the pivot module are in one piece so that the elastic means comprise a disc comprising a lower face and an upper face, the disc comprising at least on its lower face or its upper a central part in extra thickness, the central part of the lower face comprising a recess in which the shank is inserted.

In a third advantageous embodiment, the elastic means comprise a disc comprising a lower face and an upper face, the disc comprising at least on its lower face or its upper face a central part in extra thickness, the central part of the underside comprising a recess in which the pivot module is placed.

In a fourth advantageous embodiment, the elastic means comprise a disc comprising a lower face and an upper face, the disc having a central opening in which the pivot module is fixed, this pivot module comprising a bezel supporting a pierced stone and a counter-pivot stone.

In a fifth advantageous embodiment, the disk comprising, on the periphery of its upper face, a rim extending in a direction tending to move away from said upper face and ending at one end.

In another advantageous embodiment, the attachment means comprise male attachment means arranged on the support and female attachment means arranged at the end of the rim of the disc, said male attachment means and females being arranged to cooperate together.

[0019] In another advantageous embodiment, the attachment means are a weld connecting the rim of the disc to the support.

[0020] In another advantageous embodiment, the membrane spring comprises recesses or openings.

In another advantageous embodiment, the elastic means are made of metal or metal alloy.

In another advantageous embodiment, the elastic means are made of an at least partially amorphous metal alloy.

In another advantageous embodiment, the elastic means are made of polymers.

In another advantageous embodiment, the elastic means are made of filled polymers.

In another advantageous embodiment, the elastic means are made of polycrystalline ceramic.

In another advantageous embodiment, the elastic means are made of monocrystalline ceramic.

BRIEF DESCRIPTION OF FIGURES

The aims, advantages and characteristics of the shock bearing according to the present invention will appear more clearly in the following detailed description of at least one embodiment of the invention given solely by way of non-limiting example and illustrated by the drawings. appended in which: - figure 1, already mentioned, makes it possible to schematically represent a shockproof bearing of a timepiece according to the prior art; - Figure 2 schematically shows a timepiece shock bearing according to the invention; - Figure 3 schematically shows the elastic means according to the present invention; - Figure 4, 5 and 6 schematically represent a timepiece shock bearing according to a first embodiment of the invention and two examples of similar embodiments; - Figures 7 and 7a schematically represent a timepiece shockproof bearing according to a second embodiment of the invention; - Figure 8 schematically shows a timepiece shockproof bearing according to a third embodiment of the invention;

DETAILED DESCRIPTION

The present invention proceeds from the general inventive idea which consists in providing a shock absorber bearing 100 having greater reliability by avoiding contact. The present invention can take different forms.

[0029] Figure 2 illustrates a shock bearing 100 which comprises a support 101 in the form of a disc having a circular vertical wall 101a delimiting a housing 102 whose center is pierced with a hole 103. This hole 103 allows the passage a balance shaft terminated by a shank.

[0030] The support 101 can either be an independent part driven in or fixed by any means in the frame of the watch movement, or be integrated into a part of the movement, such as a bridge or a plate.

In the housing 102 of the support 101 is arranged a pivot system 105 whose purpose is to dampen, at least in part, the shocks suffered by the balance shaft. The pivot system 105 comprises elastic means 107, a pivot module 109 and attachment means 111 for attaching said pivot system 105 to the support 101.

Advantageously, the elastic means 107 are in the form of a membrane. This membrane 107 being made of a first material.

In one embodiment of the elastic means 107 and visible in Figure 3, these elastic means 107 are in the form of a base 200 in the form of a disc comprising a lower face 203 and an upper face 201 and having a central hole 205, the lower face 203 facing the bottom of the support 101 that is to say the hole 103 in which the balance shaft terminated by a shank passes. In the center of this disc 200 is fixed the pivot module 109. This disc 200 comprises, at its periphery, a peripheral rim 207 extending in an axial direction, that is to say in a direction tending to move away from the upper face 201. Preferably, this flange 207 extends in a direction tending to move away from the upper face so that the disc 200 increases when the height of the flange 207 increases. The elastic means 107 are shown mounted to the support 101 in Figure 4.

At the end of this flange 207, the attachment means 111 are arranged to fix this membrane 107 with the pivot module 109 which is fixed there. These attachment means 111 can be a crimping ring. Advantageously, the attachment means 111 are integral with the elastic means 107, that is to say with the membrane. These attachment means 111 then comprise male attachment means 111b and female attachment means 111a. The female attachment means 111a comprise, at the end 209 of the peripheral rim 207, two peripheral circular projections 211 parallel to each other. This arrangement allows the presence of a groove 213 between these two projections 211. The support 101 then comprises, at its circular vertical wall 101a, the male attachment means 111b in the form of a retaining flange 101b extending along the wall 101a as seen in Figure 4. This retaining flange 101b and the groove 213 located between the two circular projections 211 of the flange 207 of the elastic means 107 are arranged to cooperate together so that said flange holding 101b engages in said groove 213. This configuration allows the elastic means 107 to be easily fixed to said support 101. These fastening means 111 can be fixed or mounted with glue or solder or be mounted by force or by screwing.

In a first embodiment visible in Figure 4, the elastic means 107, that is to say a membrane spring, and the pivot module are in one piece. By this is meant that the elastic means 107 and the pivot module 109 are made of the same material. The disc-shaped base 300 comprises, at its upper face 301 and/or its lower face 303, an extra thickness 315 which may have a trapezoidal profile. This extra thickness 315 is preferably placed in the center of the disc 300. The disc 300 comprises on its lower face 303 a recess 317 into which the shank of the balance shaft can be inserted. This recess 317 may have a conical bottom. FIG. 4 shows the example in which the disc 300 comprises, at the center of the upper face 301 and of the lower face 303, an extra thickness 315 which may have a trapezoidal profile. Figures 5 and 6 respectively show the example in which the disc 300 comprises an extra thickness 315 which may have a trapezoidal profile at the level of the lower face 303, and the example in which the disc 300 comprises an extra thickness 315 which may have a trapezoidal profile at the level of the upper face 301. The advantage of this embodiment is to have a pivot system 105 made in a single piece allowing to have a simpler, faster manufacturing process since a single piece must be manufactured . In addition, this embodiment makes it possible to have a method of mounting the shockproof system which is clearly simplified since only the step of fixing the pivot system 105 to the support 101 is necessary. The intermediate stages of assembling the different parts together no longer exist.

In a second embodiment visible in Figures 7 and 7a, the membrane spring 107 and the pivot module 109 are not monobloc but the pivot module 109 is linked or fixed to the elastic means 107. For this, the disk 400 of the membrane spring 107 comprises an extra thickness 413 on its upper face 401 and/or on its lower face 403 at their central part. The lower face 403 then comprises a pivot housing 417. This pivot housing 317 is arranged to receive the pivot module 109 which is preferably in the form of a piece 419 such as a pellet. This pellet 419 is inserted into the pivot housing 417 and includes the recess 420 into which the rod of the balance shaft can be inserted. This configuration makes it possible to separate the materials of the spring and pivot functions. Indeed, it is possible that the first material, that is to say the material which constitutes the membrane spring 107 has good mechanical characteristics for applications relating to springs but that it does not have any for applications. regarding pivots. Spring applications require good elastic deformation capacity, while pivot applications require good wear and friction resistance characteristics. This configuration presenting a dissociation of the spring and pivot functions thus makes it possible to use the most effective materials for each function while maintaining simplicity since said pivot system comprises only two elements: the membrane spring 107 and the pellet 419 acting as a pivot. The embodiments of Figures 4 to 6 of the first embodiment are also possible for this second embodiment so that the extra thickness 413 can be located on one or the other of the lower 403 or upper 401 faces.

In a third embodiment visible in Figure 8, the elastic means 107 and the pivot module 109 are not in one piece. The pivot module 109 comprises a bezel 500 in which are arranged a pierced stone 501 and a counter-pivot stone 503. This bezel 500 is therefore in the form of an annular piece comprising two stones: a pierced stone 501 and a stone against pivot 503 respectively placed one below the other. The whole is then fixed in the central hole 205 of the disc 200 of the elastic means 107 visible in Figure 3.

This arrangement allows the use of a kitten 500 corresponding to those used in the shock absorber systems of the prior art where only the membrane spring 107 is a new element. A pivot system 105 is therefore obtained, the costs of which are lower and the assembly of which requires only small changes.

If the shock absorber system 100 is distinguished by the use of elastic means 107 in the form of a suspended membrane spring, it is also distinguished by the materials used when the lyre-type springs used in anti-shock systems according to the prior art mainly use brass, phynox or CuBe.

Indeed, in a first variant, the elastic means 107, that is to say the membrane spring, are made of a polymer material. This category of material includes polymers charged or not, that is to say a system formed by a set of macromolecules of the same chemical nature in which organic and inorganic elements are added or not. There are two types of fillers for polymers, fillers which are used as mechanical reinforcement in order to have a more resistant material or fillers to obtain a tribological improvement.

[0041]The first advantage of these polymers is that they are inexpensive, which leads to a low cost of the polymer parts. This low cost is associated with the fact that polymer parts are easy to make. Indeed, polymer parts can be manufactured by an injection process, that is to say that the polymer is placed in liquid form and is injected with more or less pressure into a mold comprising the imprint of the part. to achieve. This technique is inexpensive and makes it possible to produce large series parts with high precision and a good surface finish. Thus, in the case of the first embodiment in which the elastic means and the pivot module are monolithic, it is possible to produce the pivot system 105 in a single injection step. This injection method can also be useful for the second embodiment and for the third embodiment. For the second embodiment, this translates into the possibility of directly overmolding the pad 419 acting as a pivot module 109. This pad 419 is placed in a mold whose footprint corresponds to that of the pivot system 105. The pivot system 105 with pad 419 directly fixed in membrane spring 107 making it possible to avoid an additional fixing step.

This possibility of overmolding is also used in the case of the third embodiment. The bezel 500 in which the pierced stone 501 and the stone against pivot 503 are placed is placed in a mold into which a liquid polymer is injected.

In the case of the second embodiment and the third embodiment, it can be provided the presence of reliefs on the pad 419 or on the bezel 500 so as to improve the grip with the membrane spring.

Furthermore, the use of polymers is advantageous because these materials have interesting mechanical characteristics. Indeed, polymers firstly have a high deformation capacity which allows them to easily absorb shocks. Nevertheless, this ability to deform easily can lead to rupture of the membrane. To counter this, the polymer membrane can be made with a greater thickness resulting in greater resistance of said membrane. As polymers have a low density compared to metals (density of Polyoxy-methylene or POM is around 1420 Kg/m<3> while steel has a density of 7500kg/m<3>), this makes it possible to produce parts with larger dimensions without increasing the mass compared to a metal part.

The polymers also have advantageous tribological properties. In particular, certain polymer-metal and polymer-polymer tribological couples are advantageous so that the use of polymers within the framework of the bearing function is possible. Effectively, this function concerns the interaction between the bearing, that is to say, in the prior art, the pierced stone assembly, the stone against the pivot and the shank of the axle. This interaction occurs when the shaft pivots causing friction between the shaft via its shank and the bearing. An advantageous polymer-metal or polymer-polymer tribological couple allows, in the case where the bearing is made of polymer and where the shaft is made of metal or polymer, to have less friction. As this friction leads to wear of the parts that are the rod and the bearing, less friction leads to less wear and therefore a longer service life. This also leads to lower energy losses, which is very important for mechanical watches.

In a second variant, the elastic means 107 are made of a metal. This metal can be pure or be an alloy or be a metallic glass.

[0047] One of the advantages of crystalline or amorphous metals is that they have a high elastic modulus (for example, spring steel has a Young's modulus of 200 GPa whereas polyoxymethylene or POM has a Young's modulus of 3.1GPa). A membrane spring having good rigidity is then obtained and which, compared to less rigid materials requiring a greater thickness to compensate for the lack of rigidity, does not need this artifice.

Metals also have a good elastic limit, that is to say a stress beyond which the material deforms plastically, which is high. However, for amorphous metals, this elastic limit is about twice as high as the equivalent in crystalline metal with an equivalent Young's modulus. Amorphous metals are therefore materials that withstand greater stress before deforming plastically.

Finally, the metals can have tribological properties in terms of coefficient of friction and rate of wear so that a one-piece anti-shock system 100 as defined in the first embodiment can cooperate with an axle rod metal without causing greater wear, a coefficient of friction of 0.15 is a desired value for the shock bearing according to the present invention.

To achieve the shock bearing 100 according to the present invention, several methods can be performed. For example, the membrane spring 107 can be produced by simple and inexpensive techniques such as cutting and folding, making it possible to produce parts in large series.

For amorphous metals or metallic glasses, it is possible to use hot forming and casting in order to take advantage of the properties of metallic glasses. Indeed, casting can be used to produce said membrane. For this, the material used is heated to a temperature above its melting point, said material thus becoming liquid. It is then poured into a mould. The material is then cooled rapidly so that the atoms making up said material cannot arrange themselves to form a structure, the absence of structure allowing said material to be amorphous. The advantage of casting an amorphous metal is to allow greater precision and greater strength of the cast object. Indeed, amorphous metals, when they are cast, have the advantage of exhibiting a solidification shrinkage of less than 1% whereas the casting of their crystalline equivalents exhibits a solidification shrinkage of 5 to 7%. This means that the amorphous material will keep the shape and dimensions of the place in which it is poured whereas a crystalline material will contract. Moreover, even if the solidification shrinkage can be taken into account during the manufacture of the mould, the fact of having an almost zero shrinkage makes it possible to dispense with this step.

Hot forming is also a method which advantageously uses the properties of the amorphous metal. Indeed, this method consists in first making an amorphous metal preform and placing it in two dies. This preform is then heated to a temperature between the glass transition temperature and the crystallization temperature of the first material. In this interval, the amorphous metal therefore sees its viscosity decrease sharply so that it becomes easily manipulated. A low stress of the order of 1 MPa can therefore be applied to said material in order to make it fit into the negative. This viscosity also allows the amorphous metal to fill the negative well, so the precision of this process is important. In the case of the first embodiment, hot forming makes it possible to produce the entire pivot system 105 in a single step.

In a third variant, the elastic means 107 are made of a ceramic. This ceramic can be an oxide, that is to say a polycrystalline material such as aluminum oxide or boron nitride or titanium carbide. This ceramic can also be a monocrystalline material such as silicon.

[0054] Firstly, the use of ceramics to provide the pivot function is made possible because these materials have characteristics such as a very interesting coefficient of friction, hardness and wear resistance. Effectively, for the pivot function, a material is required which supports the friction caused by the rotation of the axle carrying the wheel on said pivot. Preferably, the material constituting the pivot module 109 must cause as little friction as possible.

However, the low coefficient of friction of ceramics such as polycrystalline materials allows them to facilitate the rotation of the axis carrying the wheel by creating less friction between said axis and the pivoting means (coefficient of friction without lubrication of the sapphire on steel = 0.2, coefficient of friction without lubrication of steel on steel = 1.2). This advantage is combined with the high hardness of ceramics and their great resistance to wear, to obtain a pivot resistant to shocks and friction and therefore to have a durable pivot. One can then imagine that the elastic means 107 are made of polymer and the pivot module 109 is of ceramic in the case of the second embodiment.

A process used to produce parts from polycrystalline materials is sintering.

This technique consists in providing ceramic or polycrystalline material in the form of powders. These powders are placed in a matrix then compressed under high pressure that can reach several thousand bars. A preform is then obtained which is placed in an oven to be heated to a temperature below the melting temperature of the main element constituting the powders. This step of increasing the temperature allows the materials to diffuse into each other so that the grains of powder bond solidly.

A variant of this method consists in mixing these powders with a liquid so as to obtain a paste which is molded in a matrix then dried so as to harden. The desired part is then obtained, which is then placed in an oven to be heated to a temperature below the melting point of the main element of the powders. This step of raising the temperature then allows the materials to diffuse into one another so that the grains of powder bond solidly.

In another variant of the embodiments, the elastic means 107 comprise structures. These structures are in the form of openings or recesses. These openings or recesses are arranged on the disc-shaped base 200, 300, 400 or on the flange 207. These internal structures are preferably of circular or oval shapes but other shapes can be envisaged. These internal structures are used in order to be able to adjust the axial and radial rigidity of the elastic means 107. Indeed, these internal structures lead to a reduction in the rigidity and have the consequence of making them more flexible in the areas where they are made. The elastic means 107 can then deform more easily in the areas where these structures are made. At a minimum, at least two openings or recesses diametrically opposed to each other are arranged. This arrangement thus makes it possible to distribute the restoring forces. It will be understood that the number of structures is greater and that these structures are regularly distributed. This makes it possible to locally make the part forming the elastic means 107 more flexible so as to obtain predetermined restoring forces.

It will be understood that various modifications and/or improvements and/or combinations obvious to those skilled in the art can be made to the various embodiments of the invention set out above without departing from the scope of the invention defined by the appended claims.

Claims (15)

1. Shock-absorbing bearing for an axis (3) of a moving part of a timepiece, said axis comprising a shank (3a), said bearing comprising a support (101) provided with a housing (102) receiving a pivot system (105) comprising a pivot module (109) into which the rod can be inserted and elastic means (107) arranged so that the pivot module is mounted suspended and to exert on the pivot module at least one axial force, characterized in that the elastic means comprise a membrane spring. 2. Damper bearing according to claim 1, characterized in that it further comprises fastening means (111) for fixing the pivot system (105) to the support (101). 3. Damper bearing according to claim 1 or 2, characterized in that the elastic means (107) and the pivot module (109) are in one piece so that the elastic means comprise a base (300) comprising a lower face (303) and an upper face (301), the base comprising at least on its lower face or its upper face an extra thickness (315), the lower face comprising a recess (317) in which the stud can be inserted. 4. Damper bearing according to claim 1 or 2, characterized in that the elastic means (107) comprise a base (400) comprising a lower face (403) and an upper face (401), the base comprising at least on its face lower surface or its upper face an extra thickness (413), the lower face comprising a pivot housing (417) in which the pivot module (109) is placed. 5. Damper bearing according to claim 1 or 2, characterized in that the elastic means (107) comprise a base (200) comprising a lower face and an upper face, the base (200) having a central opening (205) in which the pivot module (109) is fixed, this pivot module comprising a bezel (500) supporting a pierced stone (501) and a counter-pivot stone (503). 6. Damper bearing according to one of claims 3 to 5, characterized in that the base is in the form of a disc (200, 300, 400) comprising, at its periphery, a flange (207) extending in a direction tending to move away from said upper face and ending in an end (209). 7. Damper bearing according to claim 6, characterized in that the attachment means (111) comprise male attachment means (111 b) arranged on the support and female attachment means (111 a) arranged on the end of the flange (209) of the disc, said male and female attachment means being arranged to cooperate together. 8. Damper bearing according to claim 6, characterized in that the attachment means (111) are a weld connecting the rim of the disc to the support. 9. Damper bearing according to one of the preceding claims, characterized in that the elastic means (107) comprise recesses or openings making them locally more flexible so as to obtain predetermined restoring forces. 10. Damper bearing according to one of the preceding claims, characterized in that the elastic means (107) are made of metal or metal alloy. 11. Damper bearing according to claim 10, characterized in that the elastic means (107) are made of an at least partially amorphous metal alloy. 12. Damper bearing according to one of claims 1 to 9, characterized in that the elastic means (107) are made of polymers. 13. Damper bearing according to claim 12, characterized in that the elastic means (107) are made of filled polymers. 14. Damper bearing according to one of claims 1 to 9, characterized in that the elastic means (107) are made of polycrystalline ceramic. 15. Damper bearing according to one of claims 1 to 9, characterized in that the elastic means (107) are made of monocrystalline ceramic.