Shock-absorbing bearing for timepiece

This shock-absorbing bearing comprises a bearing block (1), a pierced jewel (3), an endstone (4) and a shock-absorbing spring (5) connected to said bearing block (1) by four linking arms (5a1, 5a2, 5a3, 5a4), parallel to a plane containing the pivot axis (X) of said bearing and forming two suspension elements (5a1, 5c1, 5a2; 5a3, 5c2, 5a4), each having two of said linking arms connected to each other by a branch in the form of an arc (5c1, 5c2) centered on said pivot axis (X) and having a radius greater than that of said endstone (4), these suspension elements being connected to each other by two diametric arms (5e) located on either side of a central support element (5d). The outer ends of said diametric arms (5e) are connected to two of said linking arms (5a2, 5a4) belonging to said respective suspension elements (5a1, 5c1, 5a2; 5a3, 5c2, 5a4).

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority of European Application No. 05405263.4 filed Mar. 23, 2005, which is included in its entirety by reference made hereto.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a shock-absorbing bearing for a timepiece, comprising a bearing block, a pierced bearing jewel, a seat for positioning this bearing jewel in this bearing block, an endstone, a seat for positioning this endstone in this bearing block, and a shock-absorbing spring to hold said endstone against said positioning seat, this shock-absorbing spring being connected to said bearing block by four linking arms, parallel to a plane containing the pivot axis of said bearing, and forming, on each side of this plane, a suspension element having two of said linking arms connected to each other by a branch in the form of an arc centered on said pivot axis and having a radius different from that of said endstone, these suspension elements being connected to each other by two diametric arms located on either side of a central support element.

2. Description of the Related Art

Shock-absorbing bearings, designed in particular for the balance staff, have been the subject of a large amount of research work which culminated between the early 1930s and the end of the 1950s. There are approximately 400 patents in this field, including 250 in the aforementioned period. The solutions used at the present time are satisfactory on the whole, which doubtless explains why this subject has seen practically no recent development.

One of the essential elements of this kind of bearing is the shock-absorbing spring. It must be remembered that the dimensions of such a spring are less than 2 mm and are generally in the region of 1.5 mm. These dimensions give rise to design problems as regards both the elastic limits and plastic deformation, particularly during the fixing of the spring, the retention of the spring in case of shock, the mounting of the spring, and the mounting and dismantling of the bearing.

With most shock-absorbing springs, it is found that either the shock-absorbing spring must be positioned before the bearing support is pressed into the bridge or plate, making it necessary to extract the bearing support in order to dismantle the bearing, or, if the extraction of the support is not necessary, the hinge of the shock-absorbing spring fails to remain in place when the spring is disengaged from the support, creating a risk of losing the spring which measures less than 2 mm. It should also be added that the springs having a hinge on one end and fastening means on the other cannot be mounted on the support unless the hinge is placed in the part of the support shaped to receive it. The watchmaker must therefore identify the side of the spring acting as a hinge and the site of the bearing support shaped to receive this hinge, which, because of the dimensions, makes handling even more complicated, with the constant risk of losing the spring.

A shock-absorbing bearing of the aforementioned type to which the invention relates, particularly in respect of the shock-absorbing spring, was previously proposed in U.S. Pat. No. 3,306,028. The principal drawback of this bearing arises from the fact that the central support element of the shock-absorbing spring is connected to the bearing support by four arms, each of which has a length which is reduced by half compared with the total dimension of each of the two suspension elements linking the central support element to the bearing support.

In view of the very small dimensions of such a shock-absorbing spring, the halving of the length of the arms linking this central support element to the bearing support gives rise to a problem with respect to the consequent reduction of the elastic limit, so that this limit can easily be exceeded during the fastening of the arms for linking the shock-absorbing spring to the bearing support.

In case of shock, such a shock-absorbing spring can become disengaged more easily, especially if it has undergone plastic deformation during its fitting.

BRIEF SUMMARY OF THE INVENTION

The object of the present invention is to overcome, at least partially, the aforementioned drawbacks.

For this purpose, the invention proposes a shock-absorbing bearing for a timepiece as claimed in claim1.

The principal advantage of the shock-absorbing bearing according to the present invention is due to the fact that the fastening of the two diametric arms of the central support element to two of the four arms for linking to the bearing support makes it possible to form, on either side of the diametric arms connecting the central support element to the two suspension elements, two resilient elements which facilitate the positioning of the spring because of the significant increase in the range of elastic deformation, while the diametric arms, attached on the one hand to the central support part and on the other hand to two linking arms, form a more rigid element passing through the pivot centre. This greater rigidity enables the shock resistance to be improved. The spring of the bearing proposed by the present invention is thus shaped to provide a division of functions between its different parts.

Preferably, the free ends of the linking arms terminate in fastening elements, the fastening elements of each pair of linking arms located opposite each other being turned towards the outer side of each pair of linking arms.

Advantageously, the two pairs of linking arms of the suspension spring, formed by the opposing linking arms of the two suspension elements, have a central symmetry with respect to the pivot axis of the bearing.

This characteristic has the advantage that it is possible to fix the spring to the bearing support in either of two possible positions, at 180° to each other about the pivot axis of the bearing, thus considerably facilitating the fitting operations. Furthermore, owing to this characteristic, either of the pairs of linking arms of the suspension spring, formed by the opposing linking arms of the two suspension elements, can be used equally well for opening the bearing or for acting as the spring hinge on the support. Thus, even if the different parts of the shock-absorbing spring have different functions, this spring has no direction of fitting to the bearing support, and this considerably simplifies the fitting operation.

Preferably, the shock-absorbing spring has a constant thickness and is flat in the rest state. Because of this characteristic, either of the faces of the spring can be placed above or below. In combination with the characteristic relating to the central symmetry, the spring can be placed in the bearing support without the previous choice of a face which is to be oriented above or below, or of a side which is to be used for opening or to act as a hinge.

The latter advantageous characteristic of flatness of the shock-absorbing spring facilitates the manufacture of the spring by a number of methods, the following examples of which can be mentioned without restrictive intent: the lithographic method known by the abbreviation LIGA (Lithographie Galvano-Abformung), electroforming, stamping, chemical milling and wire erosion.

In a preferred embodiment of the invention, the profile of the central support part of the shock-absorbing spring is chosen to act as a gauge for the quantity of oil in the bearing, and for this purpose it has at least two radial reference marks having different radii, one for determining the maximum quantity of oil and the other for determining the minimum quantity, and for determining the centering of this oil with respect to said pivot axis.

This profile makes it possible to ensure the presence of a drop of oil, to check the position of this drop and to measure its size with respect to the radial reference marks. This inspection operation can be carried out in a precise way, particularly with the aid of a camera.

In another advantageous variant of the invention, the fastening elements of the two linking arms which are not connected to the outer ends of the two diametric arms are longer than the fastening elements of the other two linking arms.

These fastening elements are therefore associated with the most elastic parts of the springs, thus reducing the risks of disengagement of the spring in case of shock.

Preferably the bearing support has a diametric passage extending on both sides of the seat of said endstone, to receive the linking arms of the shock-absorbing spring, and is shaped symmetrically with respect to any plane passing through said pivot axis.

The bearing with its diametric passage is designed to receive the spring with central symmetry in this diametric passage in either of the two possible positions. The fitting of the shock-absorbing spring does not have to be carried out in any particular sequence. This symmetry thus considerably simplifies the manufacture of the bearing support and does not require any block for hinging the spring, such a block always being, because of its size, a fragile element which is difficult to manufacture.

It is also possible to form chamfers along the edges of the diametric passage of the bearing support, so as to enable the shock-absorbing spring to be placed by simple translation parallel to the pivot axis. When a pressure parallel to the pivot axis is exerted on the linking arms of the shock-absorbing spring, the chamfers exert a force which brings the two opposing linking arms towards each other.

Shock tests conducted on shock-absorbing bearings as proposed by the present invention have shown that the shock-absorbing spring withstands even the most severe shocks without becoming disengaged from the bearing support. In extreme cases, abnormal shocks can cause a plastic deformation of the shock-absorbing spring. However, this has no troublesome effects on the movement of the watch, which can continue to operate normally since the shock-absorbing bearing retains its integrity, even if its shock-absorbing properties have been decreased.

The attached drawings show, schematically and by way of example, some variants of the shock-absorbing bearing proposed by the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The bearing shown inFIGS. 1 and 2has a bearing block1comprising a seat in the form of a truncated conical cup1afor positioning a chaton2which has a cylindrical part into which a pierced jewel3is pressed and which has a seat2afor an endstone4. A shock-absorbing spring5is fixed to the bearing block1to retain the chaton2and the endstone4in an elastic way in their respective seats1a,2a.

The bearing block1has the characteristic of being entirely symmetrical with respect to all the planes containing the pivot axis X of the bearing. A diametric milled area1bis formed on the upper part of this bearing block and two parallel milled areas1c, perpendicular to the diametric milled area1b, are formed on the outside of the bearing block1, in its thickness, at a certain distance from its upper face.

These three milled areas1b,1care designed for the fixing of the four linking arms5a1,5a2,5a3,5a4of the shock-absorbing spring5, the two arms5a1,5a4and5a2,5a3respectively, located opposite each other, being parallel. The width of the diametric milled area1bmatches that of each pair of parallel arms5a1,5a4and 5a2,5a3respectively, located opposite each other. The two parallel milled areas1care designed to receive the respective fastening ends5b1,5b2,5b3,5b4, turned toward the outside of each pair of parallel arms, of the four linking arms5a1,5a2,5a3,5a4, thus enabling the shock-absorbing spring5to be fixed to the bearing block1. Clearly, since the linking arms5a1,5a2,5a3,5a4are parallel in pairs and since the gaps between the two pairs of arms5a1,5a4and 5a2,5a3respectively are equal, the shock-absorbing spring5can be positioned for fixing in the milled area1bin either of two symmetrical positions at 180° to each other.

The two linking arms5a1,5a2and 5a3,5a4respectively, each located in the extension of the other, are connected to each other by two branches in the form of arcs5c1and 5c2respectively, which are centered on the pivot axis X and whose radii are greater than that of the endstone4. These two branches in the form of arcs, in combination with the linking arms5a1,5a2and 5a3,5a4respectively, form two suspension elements, one on each side of a plane passing through the pivot axis X of the bearing and through the middle of the diametric milled area1b.

The shock-absorbing spring5also has a central support element5dconnected to each of the two suspension elements5a1,5c1,5a2and 5a3,5c2,5a4respectively by two arms5ealigned diametrically but connected, in this example, to the junctions between the arm5a4and the branch in the form of an arc5c2, and between the arm5a2and the branch in the form of an arc5c1, respectively. This specific arrangement provides two branches5a1,5c1and 5a3,5c2respectively, having considerably greater elasticity than that of the arms5a2,5a4, and designed to facilitate the placing of the spring and particularly to avoid the risks of plastic deformation of the arms during this manipulation. The arms5a2,5a4, connected to the diametric arms5eand to the central support element5d, form a significantly more rigid assembly designed to withstand shocks.

It can also be seen that the shock-absorbing spring5in its non-deformed state is flat, so that there is no top side or underside, and thus that either of its faces can be placed above or below for its fixing. This characteristic also facilitates its manufacture, which can be carried out, for example, by the LIGA method, by electroforming, by stamping, by chemical milling or by wire erosion.

The supporting element5dof the spring can advantageously act as an oil gauge, for measuring the quantity of oil and the centering of the drop of oil between the pierced jewel3and the endstone4. For this purpose, the shape imparted to the central supporting element is preferably chosen to enable the presence of oil, its centering and the quantity of oil to be determined by viewing through the transparent endstone4. The first condition consists in the disengagement of the central part of the endstone4. The shape of this supporting element5d, similar to a rectangle, but with its two shorter sides in the form of arcs centered on the pivot axis X of the bearing, according toFIG. 2, makes it possible, for example, to choose the gap between the two long sides of this near-rectangle to match the minimum diameter of the oil drop, while its two opposing faces in the form of arcs can delimit the maximum diameter of the oil drop.

In the variant ofFIG. 3, a shock-absorbing spring15has a central supporting element15dwhose central opening is formed by the alternation of eight convex and concave arcs, the four convex arcs being coaxial with the pivot axis X of the bearing and having the same radii, while the four concave arcs have the same radii, their centers being located on the same circle concentric with the pivot axis X of the bearing and spaced at 90° from each other around the pivot axis X of the bearing. The two diametric arms15eare connected to the central support element15dby two opposing concave arcs. The other two parts with a concave profile of the central support element15dare delimited externally by two arcs which are concentric with these other two parts with a concave profile but which have smaller radii, and which can also be used to measure the quantity of oil.

As shown in broken lines inFIG. 3, the fastening ends15b1,15b2,15b3,15b4of the linking arms15a1,15a2,15a3,15a4can be elongated with respect to those ofFIG. 2. It would also be possible to elongate only the ends15b1,15b3of the more elastic linking arms, since they are more likely than the other two to become disengaged in case of shock.

FIG. 4shows yet another variant of the shape of the supporting element25dof the spring25, which has, on one side of the diametric arms25e, a part in the form of an arc concentric with the pivot axis X of the bearing, and, on the other side of these diametric arms25e, two portions of the arc extending beyond these diametric arms25eby the same angular quantity and having their ends connected to each other by a segment in the form of a concave arc whose radius is significantly greater than that of the part in the form of an arc centered on the pivot axis X, or by a straight segment.

In the variant shown inFIG. 5, the central supporting element35dis annular. Given that this shape has the drawback that the presence or absence of oil cannot be detected if the edge of the meniscus formed by the oil drop is located in the width of the ring, the ring has a radial cut-out35fwhich enables the meniscus to be seen.

Referring toFIGS. 1 and 2again, it will be seen that chamfers are formed, particularly on the two sides of the diametric milled area1bof the bearing block1. These chamfers can be used to convert a pressure exerted on the linking arms5a1,5a2,5a3,5a4of the shock-absorbing spring into forces which tend to bring together the two opposing parallel arms5a1,5a4and 5a2,5a3respectively, in such a way that it is possible to place the shock-absorbing spring by simple translation with a simultaneous exertion of pressure on the four linking arms5a1,5a2,5a3,5a4.

Recesses1eare formed in the upper face of the bearing block1in the locations where the parallel edges of the diametric milled area1bopen into the truncated conical seat1aof the chaton2. These recesses1emake it possible to introduce the points of tweezers or pins to disengage the fastening ends5b1,5b2,5b3,5b4of the linking arms5a1,5a2,5a3,5a4from the bearing block1. It should be noted that it is possible to disengage only one pair of opposing parallel linking arms5a1,5a4or5a2,5a3, the other pair being used as a hinge to release the endstone4.

The variant of the shock-absorbing spring45shown inFIG. 6differs from the other springs described above essentially in that the diametric arms45eare not connected to the junctions between two linking arms5a2,5a4and the branches in the form of arcs5c1and5c2respectively, as in the case ofFIG. 2for example, but these diametric arms45eare connected to the outer ends of the linking arms45a2and45a4respectively by a connecting segment45f1and45f2respectively. By being connected to the outer ends of the linking arms45a2and45a4respectively, the diametric arms45eare effectively connected to the respective fastening ends45b2,45b4of these linking arms45a2,45a4. In this variant, the elastic branches are elongated further, since each one has the set of the two suspension elements45a1,45c1,45a2or45a3,45c2,45a4respectively.