EP2015147A2 - Shock-absorbing bearing for a timepiece - Google Patents

Abstract

The bearing (16) has a pivoting unit (30) comprising an elastic arm and a central portion that includes a cylindrical blind hole, where the arm has a spiral structure. A pivot (24) contacts the interior of the blind hole. The pivoting unit and the central portion are formed from a single piece in a pastille made of monocrystalline material. An annular part (31) forming a housing is arranged to be driven out through the hole of a frame of the timepiece, where the annular part receives and fixes ends of the elastic arm.

Description

Technical area

The present invention relates to bearings for timepieces, and more particularly of the type for damping shocks. Such bearings are, most frequently, used to ensure the pivoting of the rockers. Indeed, the latter are provided with small diameter pivots, that is to say, delicate. Since, moreover, the mass of the balance is relatively large, the risk is high that a pivot breaks under the effect of a shock.

State of the art

There are many types of shock absorbing bearings. The most frequently used include a body provided with positioning and sliding surfaces, a pierced stone and a counter-pivot stone together forming a pivot member, these stones being disposed in the body and positioned on the positioning and sliding surfaces. A spring maintains the stones in the rest position, while allowing them to move within a certain limit under the effect of a shock, the axis of the balance then arriving against stops. Such bearings have, for example been sold under the trademark Incabloc ®.

Shock absorbing bearings are also known in which the elastic members and the pivot members form a whole. They have the advantage of being less expensive.

Thus, the document US 3,942,848 describes a shock absorbing bearing comprising an annular body intended to be driven in a bridge or a plate. A spring formed to define a conical housing is attached to the body. This housing forms a truss inside which a conical pivot of the balance comes to engage. In such a construction, the pivoting conditions are unfavorable, metal-to-metal pivoting generating significant friction. Furthermore, a bearing type crapaudine cooperating with a conical pivot is poorly suited for a timepiece quality, the positioning of the balance is not very accurate.

In the document CH 546'975 , the body is cup-shaped pierced in its bottom, and provided with a rim and a conical portion. Organs elastic and pivoting are made in one piece made of self-lubricating plastic. The central portion forms a cylindrical housing in which can engage a pendulum pivot. It is further shaped to cooperate with the conical portion, so as to ensure the centering of the central portion. Arms, forming the elastic member, start from the central part and engage under the rim. In this embodiment, the diameter of the rocker shafts must be relatively large, since the self-lubricating plastics do not support very high specific pressures.

In addition, the documents EP 1'462'879 and EP1'696'286 describe shock-absorbing bearings comprising a central piece provided with a stone and surrounded by a rosette formed in a plate of rigid elastic material. The rosette consists of springs extending radially, their central end cooperating with the central part. Such a solution makes it possible to take advantage of technologies using plates of constant thickness. In such a construction, the central piece must be put in place by removing the springs and the position is not obvious to guarantee.

Disclosure of the invention

The present invention is intended to provide a shock absorbing bearing ensuring a good positioning of the balance and a good protection of the axis. It relates more particularly to a shock absorber bearing for a timepiece which comprises a pivoting member comprising at least one elastic arm and a central portion provided with a hole inside which a pivot is in contact, the pivoting and the central portion being integrally formed in a pellet of monocrystalline material.

Due to the fact that the material used is of monocrystalline type, it is possible to machine it by chemical processes, in particular photo-lithographic methods to ensure substantially vertical walls, which is desirable to ensure good consistency in industrial production.

In order to allow easy mounting and adjustment of its position, the bearing further comprises an annular housing part, arranged to to be driven into a hole in the frame of the timepiece and to receive and fix the ends of the elastic arms.

In a particular embodiment, the annular piece has a truncated cone wall against which the pivot member bears in its outer part. In this way, it is possible to make the elastic arms more rigid and even to define a pre-arming of these arms.

In another embodiment, the bearing further comprises first and second annular pieces arranged to be driven into a hole in the frame of the timepiece, the pivoting member being interposed between the two annular pieces.

Practice has shown that both pivoting and damping conditions are particularly good with a silicon wafer.

The pivoting conditions of a steel-silicon pair make it possible to avoid lubrication. In this way, in a variant, it is possible to produce a pivoting member in which the hole is blind.

In another variant, the bearing comprises two superposed plates, one inner and one outer, each provided with at least one elastic arm and a central portion, the central portion of the inner plate being provided with a hole for receiving a pivot and the central portion of the outer plate forms a counter-pivot.

A simple structure can be obtained with a bearing whose pivoting member comprises a solid annular portion and at least two resilient arms, said arms being secured by their outer end of said solid annular portion.

In order to facilitate its centering during the implementation in particular, the bearing comprises elastic portions with annular orientation, integral with the outer end of said arms.

The elastic arms may have various shapes. However, a spiral structure seems to have advantages of simplicity and homogeneity of the structure, while providing a small footprint.

Brief description of the drawings

• les figures 1 à 4 représentent un premier mode de réalisation de paliers assurant le pivotement d'un axe de balancier, alors que la figure 5 est un diagramme montrant comment réagissent de tels paliers sous l'effet d'une accélération ;
• les figures 6 à 8 et 9 et 10 montrent deux variantes d'un deuxième mode de réalisation de paliers selon l'invention, alors que la figure 11 est un diagramme illustrant comment réagissent de tels paliers sous l'effet d'une accélération ;
• les figures 12 et 13 concernent des troisième et quatrième modes de réalisation de l'invention
• la figure 14 propose une variante supplémentaire d'un mode de réalisation.

Other features of the present invention will emerge more clearly on reading the description which follows, made with reference to the appended drawing, in which:

• the Figures 1 to 4 represent a first embodiment of bearings ensuring the pivoting of a balance shaft, while the figure 5 is a diagram showing how such bearings react under the effect of an acceleration;
• the Figures 6 to 8 and 9 and 10 show two variants of a second embodiment of bearings according to the invention, while the figure 11 is a diagram illustrating how such bearings react under the effect of an acceleration;
• the Figures 12 and 13 relate to third and fourth embodiments of the invention
• the figure 14 proposes a further variant of an embodiment.

Mode (s) of realization of the invention

A first embodiment is shown in Figures 1 to 4 . The figures 1 and 2 illustrate a portion of timepiece provided with bearings according to the invention, respectively seen in section and from above, while the Figures 3 and 4 show a portion of a bearing viewed in perspective, respectively from above and from below.

The timepiece partially represented in figures 1 and 2 comprises a frame comprising a plate 10 and a balance bridge 12, bearings 14 and 16 respectively mounted in holes in the plate 10 and the bridge 12. A rocker 18, having an axis 20 provided at both ends with tigerons 22 carrying pins 24, is pivotally mounted in the bearings 14 and 16.

The bearing 14 comprises two annular pieces 26 and 27, the piece 27 being in the form of a cup pierced at its center with a hole 28, and a pivoting member 30 interposed between the two annular pieces 26 and 27. The pivoting member 30 is thus maintained radially by the walls of the hole formed in the plate 10 and axially on both sides by the annular parts 26 and 27.

The bearing 16 comprises an annular piece 31 in the form of a cup, which defines a housing having an inner cylindrical wall 32 and a flat bearing surface 34 defined in the bottom of the cup. It is pierced with a central hole 35. It further comprises a pivoting member 30 disposed in the housing formed by the cylindrical wall 32 and the bearing surface 34. This member 30 is advantageously bonded to the annular piece. A truncated cone portion 36 forms the free end of the cup. It holds and positions a mobile bolt carrier 38.

It goes without saying that the bearing 16 as described could also be mounted on the plate 10, and the bearing 14 on the cock 12, with some adjustments accessible to the skilled person.

The pivoting members 30, better visible on the Figures 3 and 4 , are in the form of pellets comprising a solid annular portion 30a, a central portion 30b provided with a cylindrical blind hole 30c and three spirally wound elastic arms 30d connecting the central portion 30b to the annular portion 30a. They are mounted one in the annular piece 31, the other in the hole of the plate 10, held radially by the wall of the hole and axially by the annular pieces 26 and 27.

• diamètre 1,50 à 2,50mm, typiquement 1,80 mm ;
• épaisseur 0,20 à 0,30 mm typiquement 0,25mm ;
• épaisseur des bras 0,04 à 0,08 mm typiquement 0,05m ;
• longueur de la spirale 360° à 720°, typiquement 480°.

They are formed in a silicon wafer, and machined according to well-known photolithography techniques. Their dimensions are as follows:

• diameter 1.50 to 2.50 mm, typically 1.80 mm;
• thickness 0.20 to 0.30 mm typically 0.25mm;
• arm thickness 0.04 to 0.08 mm typically 0.05m;
• spiral length 360 ° to 720 °, typically 480 °.

The blind hole 30c extends over approximately half the thickness of the central portion 30b. Its diameter is chosen so that the pivot 24 which is engaged can rotate freely with a minimum of frolicking. The depth of the hole 30c is approximately equal to twice its diameter.

The rocker 18 is pivotally mounted by engagement of the pivots 24 in the blind holes 30c. The tigers 22 are engaged in the holes 28 and 35.

In case of impact, the balance 18 is subjected to a force proportional to the acceleration. This force is transmitted to the bearings by means of the pivots 24. It has the effect of deforming the elastic arms 30d until the axis 20 comes to bear, by the rods 22, against the wall of the holes 28 and 35 The balance is then blocked, but by a part of its axis having dimensions much larger than those of the pivots 24.

The elastic arms 30d are dimensioned so that the axis 20 comes into contact, by its tigger 22, with the annular parts 27 and 31 when the acceleration reaches about 500g.

The diagram of the figure 5 shows how the displacement of the central organ varies according to the acceleration undergone. As shown in this figure, at first, there is proportionality between the acceleration and the displacement, then, for an acceleration of about 500 g, one and / or the other of the tigerons 22 comes into contact with the parts Annular 27 or 31. The balance is then blocked.

The Figures 6, 7 and 8 represent a second embodiment of the invention. The figure 6 shows a part of the timepiece provided with such a bearing seen from above while the Figures 7 and 8 show a part of this bearing seen in perspective, respectively from above and from below. In these figures, the same parts bear the same references as those appearing on the Figures 1 to 4 .

This embodiment differs from that previously described by the structure of the pivot members 30. More specifically, the annular portion 30a is replaced by three annular 30e shoes, each connected to an elastic arm 30d. The sole of these shoes has a diameter greater than the diameter of the hole in which the member 30 must be engaged. In this way, during installation, the elastic arms 30d are radially armed, which has the effect of improving the centering of the hole 30c.

A variant of this embodiment is shown in Figures 9 and 10 . It can be seen a pivot member 30 respectively free and disposed in the annular part 31. The member 30 comprises a central potion 30b in which is formed a blind hole, as explained above, not visible in these figures, three elastic arms 30d extending from the portion 30b to the outside, two fingers 30f with an annular orientation and extending on either side of the end of each of the elastic arms 30d, and three fingers 30g extending radially from the central portion 30b to the outside.

In free position, the distance between the center of the central portion 30b and the free ends of the fingers 30f is greater than the inside diameter of the annular piece 31. Moreover, the distance between the center of the central portion 30b and the end arms 30d is smaller than the inside diameter of the annular part 31. In this way, when the member 30 is put in place, the fingers 30f are armed.

With such a configuration, the displacement is relatively important for small impacts, the fingers 30f participating in the deformation. As soon as the outer end of an arm 30d comes into contact with the annular piece, the active length of the spring is reduced and the restoring force is increased. The displacement is practically blocked when one of the fingers 30g comes into contact with the annular part 31. The variation of the displacement as a function of the accelerations is represented on the figure 11 .

In both embodiments described with reference to Figures 1 to 10 , the lateral displacement (X and Y axes) is defined by the thickness of the elastic arms, while the axial displacement (Z axis) is defined by the height of these arms, while the length of the arms contributes to the definition of the one and the other of these displacements.

In the embodiment illustrated in figure 12 , the two bearings 14 and 16 are identical and very close, in their structure, of the bearing 16 of the figure 1 . We find the same pivoting members 30 as those shown in Figures 7 and 8 , mounted in annular pieces 40, of structure adjacent to the annular piece 31. The only differences reside in the fact that the cylindrical wall 32 is replaced by a truncated cone wall 42, the outside diameter being smaller than the inside diameter, and that the portion forming the bottom of the cup has a drop 44 surrounding the central hole 35.

In this way, by setting up the pivoting members 30 as illustrated on the Figures 7 and 8 , the elastic arms curl and the portion central 30b is adjacent to the drop 44, touching or not according to the desired purpose. Such a construction ensures a pre-arming, insofar as the central portion 30b touches the drop 44. In this way, the bearing has a pre-winding of the springs along the three axes, facilitating the return of the central portion 30b in its rest position. If the central portion 30b does not touch the drop 44, the deformation caused by the engagement of the member 30 against the wall 42 of frustoconical stiffens the elastic arms 30d.

In the embodiment illustrated in figure 13 , the same parts have the same references as in the other embodiments. The pivoting members 30 comprise two plates 301 and 302.

The plates 301 comprise a solid annular portion 301a, a central portion 301b provided with a hole 301c passing right through them and spirally wound elastic arms 301 connecting the central portion 301b to the annular portion 301a. The central portion 301c is thinner than the rest of the plate 301, thus forming a recess 301e.

The plates 302 comprise a solid annular portion 302a, a solid central portion 302b and spirally wound elastic arms 302d connecting the central portion 302b to the annular portion 302a. The central portion 302b comprises a cylindrical protuberance 302e engaged in the recess 301 e.

The pivots 24 are engaged in the holes 301c and in abutment against the central portions 302b, which provide a counter pivot function.

In case of radial acceleration, the rocker 18 moves due to the deformation of the elastic arms 301 d until the protrusion 302e comes into contact with the wall of the recess 301e. At this moment, the elastic arms 302d are also stressed, increasing the resistance force, until the rod 22 comes into contact with the edge of the hole 35.

As regards the axial shocks, only the elastic arms 302d are stressed.

The plates 301 and 302 are mounted on the annular pieces 31 in a manner similar to the pivot member 30 described with reference to the Figures 1 to 4 however, the latter comprising two bearing surfaces and two cylindrical walls one for each of the plates 301 and 302.

It will be noted that, in this embodiment as in those described above, the bearings do not include oiler. This is made possible by the fact that the steel-silicon pair has tribological characteristics such that the presence of oil is not necessary. Under certain conditions, however, it would be possible to maintain oil in the space between the bottom of the hollow 301e and the protrusion 302e.

It is obvious to those skilled in the art that the pre-arming solutions described with reference to the Figures 6 to 10 could also be applied to the embodiments of the Figures 12 and 13 .

The steps that have been described with reference to Figures 1 to 13 represent only particular embodiments of the invention. Many other variants are still possible.

Thus, the pivot members 30 could be attached directly to frame members, without having to use an intermediate annular piece. The latter, however, facilitates the establishment of the bearing on the frame.

Other materials such as diamond could also be used to manufacture the pivot members 30. It is simply necessary that the selected material is machinable by photo-lithographic processes and that they have good tribological conditions.

In order to obtain, for axial shocks also, a reaction as illustrated on the figure 11 , it is possible to use a bearing as illustrated on the figure 12 by adding an additional plate whose central portion does not come into contact with the central portion of the pivot member until it has moved axially. Stacking is similar to that of the figure 13 but with a plate 301 provided with a blind hole, the plate 301 or 302 having a pin to define the connection point between the two plates.

It may, furthermore, be advantageous to provide for the integration of a friction or damping element at the level of the elastic arms, in order to improve the stability of the device and to cut off possible oscillation of the elastic arms. Naturally, the friction generated must affect the mobility of the pivot member only within an acceptable limit for the refocusing the central portion 30b. Advantageously, the friction implies that a minimum force must be applied on the pivot to cause a displacement of the central portion 30b. In other words, a disturbance generating a force less than this minimum force, would not overcome the forces related to friction and the device would not be disturbed.

For example, the figure 14 proposes an example illustrating such a friction element. In this variant, the central portion 30b of the pivot member 30 comprises, around the blind hole 30c, a flange 30h whose walls define a first truncated cone. In addition, the annular piece 27 comprises, around the hole 28 through which the pivot 24 passes, a cup 50 whose walls define a second truncated cone. The walls of the first and second truncated cones are arranged so that, when the resilient arms are in their rest position, they are flush with each other. A slight prestress in the axis of pivoting supports the walls of the flange 30h against that of the cup 50. The walls are substantially parallel, to avoid shocks between the two truncated cone.

Thus, when a disturbing force tending to induce radial displacement is applied to the pivot member, this force must overcome the friction generated between the walls of the first and second truncated cones before the central portion moves. radially. This improves the stability of the pivot members. It will be noted that the prestressing exerted on the central portion 30b causes an identical effect in the axial direction, that is, a disturbing force tending to induce an axial displacement must overcome the prestressing before the central part moves axially. .

The angle of the truncated cones may be relatively open, that is to say between about 120 and 180 degrees. The value of the angle defines the friction generated between the two truncated cone and therefore the minimum force to be applied to cause a displacement of the central portion 30b.

In addition, these friction also allow to quickly stop the oscillations of the elastic arms in case of disturbance.

It should be noted that the addition of an oil or a viscous liquid between the elastic arms can also make it possible to obtain a similar effect.

It thus appears that the bearings described provide effective protection against shocks and good working conditions in a limited volume.

Claims (11)

Shock absorber bearing for a timepiece, characterized in that it comprises a pivoting member (30; 301) comprising at least one elastic arm (30d; 301d, 302d) and a central portion (30b; 301b) comprising a hole (30c; 301c) inside which is intended to be in contact with a pivot (24) formed integrally in a pellet of monocrystalline material. Bearing according to claim 1, characterized in that it comprises, in addition, an annular piece (31, 40) forming a housing, arranged to be driven into a hole in the frame of the timepiece and to receive and fix the ends of said arm (30d; 301d, 302d). Bearing according to claim 2, characterized in that said annular piece (40) has a truncated cone wall (42) against which the pivot member (30) abuts in its outer part. Bearing according to claim 1, characterized in that it comprises, in addition, first (26) and second (27) annular pieces arranged to be driven into a hole of the frame (10, 12) of the timepiece said organ pivoting member (30) being interposed between the two annular pieces (26, 27). Bearing according to one of claims 1 to 4, characterized in that said pivot member (30; 301) is made of silicon. Bearing according to claim 5, characterized in that said hole (30c; 301c) is blind. Bearing according to one of claims 1 to 6, characterized in that it comprises two superposed plates (301, 302), one inner and the other outer, each provided with elastic arms (301d, 302d) and a central portion (301b, 302b) the central portion (301b) of the inner plate (301) being provided with a hole (301c) for receiving said pivot and the outer plate (302) forms a counter-pivot. Bearing according to one of claims 1 to 7, characterized in that said pivot member (30b) comprises a solid annular portion (30a) and at least two resilient arms (30d), said arms being secured by their outer end of said full annular portion (30a). Bearing according to one of claims 1 to 6, characterized in that it comprises at least two resilient arms (30d) and annular-oriented elastic portions (30e, 30f) integral with the outer end of said arms (30d) . Bearing according to one of claims 8 and 9, characterized in that said resilient arms (30d) have a spiral structure. Bearing according to one of the preceding claims, characterized in that it comprises a friction element or damping tending to oppose a disturbing force oriented so as to induce a displacement of the pivoting member.

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