EP1531696B1 - Process for manufacturing an automatic clasp for wristwatch strap - Google Patents

Abstract

A clasp and a production method thereof. The inventive clasp includes at least one main element ( 1 ) and at least one element ( 3 ) which pivots in relation to the main element. The clasp is characterised in that each of the aforementioned elements ( 1, 3 ) includes two longitudinal arms which are rolled up to form a hinge ( 7, 15 ) . Moreover, at least one of the ends of one of the elements ( 1, 3 ) includes a flexion spring ( 11 ) which can rest against the other element ( 3, 1 ) for the elastic support thereof and each arm ( 5, 13 ) of the main element ( 1 ) and the pivoting element ( 3 ) is provided with at least one longitudinal stiffening rib ( 20, 22 ).

Description

The present invention relates to a method of manufacturing a clasp type automatic opening / closing, including wristwatch.

Numerous types of clasps are known which consist essentially of two elements pivotally mounted relative to each other at the respective ends of which are connected the two free ends of the strands constituting a wristwatch. The two elements forming such a clasp are thus able to occupy two positions, namely a first position, or closed position, in which the two elements are locked one on the other by mechanical holding means, and a second position, or open position, in which these two elements are released, thereby increasing the overall diameter of the wristwatch so as to allow the user to introduce or extract it easily from his wrist.

A disadvantage inherent in this type of clasp comes from the fact that the locking devices of the two elements that constitute it, either require a significant effort to ensure their locking, or have the risk of not maintaining the bracelet safely.

To avoid this type of inconvenience, it has been proposed in a patent application FR-A-2,710,503 , a clasp in which the two elements are biased, in the closed position, by elastic means which thus permanently ensure a force tending to hold the clasp in position. closing position. Such a clasp limits the risk of inadvertent opening of the bracelet.

A disadvantage of this type of clasp is that, in the open position, the two elements can not rotate beyond an angle of 180 °, which sometimes makes it difficult to introduce the wrist of the user into the wristband . In addition, any opening force exerted on these two elements, which tends to rotate them beyond an aligned position, has the effect of irreparably damaging the clasp.

This is why it was proposed in the patent EP-A-0 867 132 a clasp of the aforementioned type in which the two elements consist respectively of a main element and a tilting element, the main element comprising a bending spring requesting an extension of the tilting element beyond the joint, in two stable equilibrium positions, namely a first position, or closing position, in which it applies the rocking element to the main element, and a second position, or open position, in which it moves the two elements of the other, the rocker element having at least one lumen adjacent to the hinge, the dimensions of which are such that they allow the bending spring, when the tilting element is in the position of opening, to cross this light so as not to solicit said rocking element. Moreover, in certain embodiments, the system is double-fold, that is to say that the clasp is composed of three elements, namely a main element which comprises at each of its ends a joint on which is mounted a rocking element as described above.

The clasps thus made consist of parts machined in the mass and, because their different constituent elements must meet contradictory mechanical requirements they are made of several assembled parts. Thus the bending spring is attached by fastening means, such as riveting or welding, on the main element. These different constraints mean that the clasps thus produced are usually intended to equip very high quality wrist watches, and this because of their particularly high cost.

The object of the present invention is to propose a clasp of the aforementioned type intended to be manufactured, not by mechanical machining methods, but by processes for producing thin pieces such as stamping, folding and cutting. .

The invention also provides a clasp of this type in which the spring which is provided with the main element is an integral part thereof and does not consist of an insert. The present invention thus makes it possible to produce a clasp of high mechanical quality at a particularly attractive cost price.

According to the invention, it is thus proposed to provide a main element and a tilting element which are made from a thin sheet of stainless steel. However, it is known that in the field of the wristwatch, so-called stainless steels are subject to constraints in oxidation materials are particularly high, so that very few of these steels are actually in fact actually stainless.

The professionals of these techniques, however, know stainless steels completely, even in the particularly severe conditions mentioned above. However, such steels also have drawbacks and in particular that of being particularly difficult to control with respect to their hardness and elasticity characteristics. Indeed, these steels are not sensitive to quenching, and their hardness is acquired by successive stamping or rolling operations, which are carried out from a steel sample whose thickness is much greater than that of the final piece. While such constraints have only an incidental importance when it is proposed to make machined parts in the mass, they are particularly troublesome when it comes to pieces made from a steel strip stainless.

Another difficulty lies in the fact that the two components of the clasp, namely the main element and the tilting element, are formed of parts which must imperatively have very different stiffness characteristics, since a zone of these elements must being somewhat elastic and not very hard to be rolled so as to form the hinges of the hinge pins, another area must have sufficient stiffness to form a spring blade to create the elastic force ensuring the maintenance of the clasp position of use, and finally a third zone must be rigid to counterbalance the stiffness of the spring.

The object of the present invention is to propose a manufacturing method making it possible to produce in one piece each of the two constituent elements of a clasp.

• utiliser un feuillard dont la raideur est celle que l'on souhaite pour le ressort,
• réaliser, par découpe, une ébauche de chacun de ces éléments, de façon à former sur chacun d'eux au moins deux branches longitudinales, et sur l'élément principal deux évidements internes aux deux branches formant entre les deux branches un ressort de flexion central,
• faire subir un recuit exclusivement aux extrémités de ces branches, de façon à en permettre le roulage,
• augmenter la raideur de ces branches en réalisant au moins une nervure suivant l'axe longitudinal de celles-ci.

The subject of the present invention is thus a method for manufacturing a clasp, especially for a wristwatch, from a metal strip, of the type comprising a main element and at least one rocking element, which are connected to one of their respective ends by a hinge, a bending spring integral with one of these elements being applied, at least in the closed position on the other element to hold it elastically in this closed position, characterized in that comprises the steps of:

• use a strap whose stiffness is that which one wishes for the spring,
• making, by cutting, a blank of each of these elements, so as to form on each of them at least two longitudinal branches, and on the main element two internal recesses to the two branches forming between the two branches a central bending spring ,
• annealing exclusively at the ends of these branches, so as to allow rolling,
• increase the stiffness of these branches by making at least one rib along the longitudinal axis thereof.

In a first embodiment of the invention, the method comprises a step during which a blank strip is formed from a strip consisting of a wound strip, whose width corresponds to one of the dimensions of the element to be produced, each of the blanks constituting the blank strip being connected to the blanks which are adjacent to it by at least one connecting lug. The blanks may be arranged so that their longitudinal axis is oriented perpendicular to the longitudinal axis of the blank strip.

In one step of the method, the blank strip will move, along its longitudinal axis, in front of heating means located in zones disposed on its transverse edges, so as to perform an annealing operation on at least one longitudinal strip of the blank strip. Preferentially, the localized heating means will consist of a laser beam.

According to the invention will be carried out subsequent to the heating phase, a rolling operation at the ends of the branches of the elements, so as to form hinges.

Also two tabs of the same end of a tilting element will be wound so as to form a double hinge, namely an internal hinge intended to receive an axis of rotation common with the main element and an external hinge intended to receive an axis stop.

Moreover one can, once the end of the branch wound, solder the end of the branch on the element on which it is made.

Although for localized heating operations it is possible to use various methods, it has been found that laser beam welding to obtain particularly remarkable results by its precision.

• chacun de ces éléments comporte à au moins l'une de ses extrémités deux branches longitudinales dont les extrémités sont roulées de façon à constituer un gond de ladite articulation,
• au moins l'une des extrémités de l'un des éléments comporte un ressort de flexion apte à venir, au moins en position d'utilisation, en appui contre l'autre élément de façon à assurer leur maintien élastique.
• chaque branche des éléments principal et basculant est pourvue d'au moins une nervure de rigidité longitudinale.

The present application also relates to a clasp, especially for a wristwatch, of the type comprising at least two elements, namely a main element and a tilting element which is pivotally mounted relative thereto by means of a hinge, characterized in that

• each of these elements comprises at least one of its ends two longitudinal branches whose ends are rolled so as to constitute a hinge of said joint,
• at least one of the ends of one of the elements comprises a bending spring adapted to come, at least in the use position, bearing against the other element so as to ensure their elastic retention.
• each branch of the main and tilting elements is provided with at least one rib of longitudinal rigidity.

Preferably the bending spring will be formed on the main element. Moreover, the rolling of the branches of the two elements which is not provided with the bending spring may be double, so as to form on the one hand a first internal hinge admitting the axis of rotation through the hinges of the joint , and a second outer hinge for supporting an abutment axis disposed beyond the first axis of rotation, outwardly, and on which the bending spring will bear in the position of use of the clasp.

In a particularly advantageous embodiment of the invention, at least the element provided with the bending spring will consist of a stainless steel with a high content of elements such as nickel, chromium, molybdenum, cobalt, sum of the contents in these elements being greater than 80%.

• La figure 1 est une vue en plan des ébauches constituant les éléments principal et basculant d'un exemple de fermoir.
• La figure 2 est une vue en perspective d'un élément principal et d'un élément basculant avant leur assemblage sur un fermoir de type à double déploiement.
• La figure 3 est une vue en perspective du fermoir à double déploiement représenté sur la figure 2, les éléments constitutifs de celui-ci étant assemblés et l'un des éléments basculants étant en position d'ouverture.
• La figure 4 est une vue en perspective du fermoir représenté sur les figures 2 et 3, les deux éléments basculants étant en position de fermeture.
• La figure 5 est une vue schématique en élévation d'un exemple d'installation permettant la fabrication d'un fermoir suivant l'invention.
• La figure 6 est une vue de dessus schématique d'une bande ébauche au cours du processus de fabrication.

One embodiment of the present invention will be described hereinafter by way of nonlimiting example, with reference to the appended drawings in which:

• The figure 1 is a plan view of the blanks constituting the main and tilting elements of an example of a clasp.
• The figure 2 is a perspective view of a main element and a tilting element prior to their assembly on a double deployment type clasp.
• The figure 3 is a perspective view of the double-fold clasp shown on the figure 2 , the constituent elements thereof being assembled and one of the tilting elements being in the open position.
• The figure 4 is a perspective view of the clasp shown on the Figures 2 and 3 both tilting elements being in the closed position.
• The figure 5 is a schematic elevational view of an example of an installation for the manufacture of a clasp according to the invention.
• The figure 6 is a schematic top view of a blank strip during the manufacturing process.

The clasp according to the invention which is represented on the Figures 2 to 4 is of the double deployment type, that is to say that it consists of three essential elements, know of a main element 1 and two tilting elements 3.

The figure 7 is a perspective view of an alternative embodiment of a clasp according to the invention.

The main element 1 is bent and ends at each of its two ends by two branches 5 whose ends are wound so as to form hinges 7. These ends comprise two longitudinal notches 9 which thus define a central tongue which constitutes a spring bending 11.

The tilting element 3 also comprises on one side, two longitudinal branches 13 which terminate in a double hinge 15, formed of an internal hinge 15a and an external hinge 15b, and which are arranged in such a way transverse that they can take place in the longitudinal notches 9 of the main element 1. It comprises at its other end a central lug 6 whose end is rolled so as to form a hinge 8 intended to be connected to one the ends of the wristband of the watch.

The main elements 1 and tilting 3 are connected by an axis of rotation 16 which is force-fitted in the hinges 7 of the main element 1 and the internal hinges 15a of the tilting element 3. A stop axis 18 is force-fitted in the hinges 15b.

When the clasp is in the closed position, that is to say in the position of use, as represented on the figure 4 , the bending springs 11 bear on their respective abutment axes 18, so that they exert on them a force creating a torque of rotation on the tilting elements 3 (due to the shift e between the axis of rotation 15 and the abutment axis 18) tending to apply them elastically against the main element 1, so that they then provide the elastic retention in the closed position of the clasp.

The branches of the main elements 1 and tilting 3 will preferably have respective ribs 20 and 22 which will control their rigidity.

When the user wants to remove the bracelet he rotates the main and tilting elements of the clasp to bring the latter in the position shown on the figure 3 and, as soon as the two main elements 1 and tilting 3 are substantially in the extension of one another, the bending spring 11 stops bearing on the abutment axis 18, so that it then exerts more torque on the tilting element 3.

When, as in the embodiment shown in the figures, the space between the branches 13 of the tilting element 3 extends inwards to form a window 24 whose dimensions are greater than those of the end of the spring 11, it is then possible to further rotate the two elements since, during this movement, the end of the spring 11 has the ability to pass through the window 24.

Each of the main and rocking elements 3 is obtained from a strip of stainless steel which is cut, for example by a punching operation, so as to constitute two respective blanks 1 'and 3', as shown in FIG. figure 1 .

According to the invention the strip has a rigidity which is equal to that which is desired to give the flexion spring 11, so that it is able to perform its functions as previously specified.

The hinges 7 and 15 of the main elements 1 and tilting 3 are formed by winding the ends of the respective branches 5 and 13 and welding the ends thereof on the corresponding elements. Preferably, this welding operation will be performed using means allowing extreme precision and in particular by means of the laser beam type.

However, for such a rolling is possible, it is necessary that at least the parts of the branches 5 and 13 which will be wound, that is to say their ends, have a low stiffness and that is why, previously at the winding operation, the ends of these branches will be heated so as to anneal them. This operation must be very localized so as not to diminish the mechanical qualities of the other parts of the blanks and will be used for this purpose to means of the laser beam type.

Preferably, the manufacture of the main elements 1 and tilting 3 will be carried out by a continuous process in which the blanks are arranged in a continuous strip (or blank strip 12), each blank being connected to the blanks which are adjacent to it by connecting lugs 4.

Hereinafter will be described such an embodiment of the invention of which some of the steps are represented. on the Figures 5 and 6 . In this exemplary embodiment, the blanks 1 'and 3' are arranged transversely with respect to the metal strip, that is to say that their longitudinal axis xx 'is perpendicular to the longitudinal axis yy' of the strip.

We have shown on Figures 5 and 6 the different successive phases of the method for producing the main element 1 of the clasp from a roll sheet 2 which takes place throughout the process and runs past different workstations P ₁ , P ₂ , ... , P ₅ respectively corresponding to machining steps I, II, ..., V.

In the first step I, the strip 2 passes into the cutting station P ₁ where the blank 1 'is formed, this blank being such that the blank is connected to each of the blanks 1' which are adjacent to it by two legs link 4 to form a blank strip 12, so that it is possible to maintain throughout the chain benefits of this type of provision.

During the second step II, the blank strip 12 moves in front of the station P ₂ which consists of a laser beam which performs a very localized heating on the two longitudinal edges of the strip which corresponds to the two ends of the blank 1 and more precisely at the ends of the branches 5. The width 1 of this treatment band 10, (represented in double hatched on the figure 6 ), corresponds to the length 1 of the branches which will then be rolled to make the hinge 7. This length will be limited so as not to reduce the stiffness of the flexion spring 11. The skilled person will know how to adjust the power of the tool as well as the speed of movement of the blank 1 'in front of it so that the metal is brought to the appropriate temperature to achieve effective annealing.

During the third step III is carried rolling the ends of the tabs 5, so as to form the hinges 7 at both ends of the blank 1 '. When the production line will manufacture the tilting elements 3, one of the ends thereof will be realized with double hinges, that is to say they will consist of a slightly flattened rolling in its center which it will allow it to receive on the inner hinge 15a the axis of rotation 16 and on the outer hinge 15b the abutment axis 18.

During the fourth step IV, the station P ₄ carries a rib on each of the legs of the rocking element 3 which will compensate for its loss of rigidity caused by the annealing operation.

By these various operations is thus given to each constituent part of these elements the proper rigidity it is necessary to ensure proper operation and good reliability of the clasp.

During the fifth and last step V, the station P ₅ uses a cutting machine to shear and eliminate the connecting lugs 4 which join together the blanks 1 '.

According to the invention, it would of course be possible to use more or less two connecting tabs 4.

Clasps according to the invention can be made with many types of metals. However, in the field of clasps for products It is preferable to use a stainless steel with a high content of elements such as nickel, chromium, molybdenum and cobalt, the sum of the contents of these elements being preferably greater than 80%, because of its real and recognized qualities. stainless steel in highly oxidizing environments, such as those to which these products are subjected when in contact with the wrists of a user.

Although the example of clasp described is of the double deployment type, the present invention is of course also applicable to a clasp of the simple deployment type which would then comprise only one tilting element 3.

One could, of course, as well as represented on the figure 7 , making a kinematic inversion of the support of the bending spring by making it on a tilting element, and the window 24 on the main element.

Claims (11)

1. A method for making a clasp, notably for a wristwatch, from a metal strip (2) of the type including a main member (1) and at least one pivoting member (3), which are connected to one of their respective ends through a joint, a flexure spring (11) integral with one of the members (1, 3) being applied, at least in the closed position, onto the other member (3, 1) in order to elastically maintain it in this closed position, characterized in that it includes the steps of:

   - using a strip (2), the stiffness of which is that which is desired for the spring (11),

   - making, by cutting out, a blank (1', 3') of each of these members (1, 3) so as to form on each of them at least two longitudinal branches (5), and on the main member (1) two recesses (9) internal to both branches (5) forming between the latter a central flexure spring (11),

   - exclusively submitting the ends of these branches (5, 13) to annealing, so as to allow rolling,

   - increasing the stiffness of these branches (5, 13) by producing at least one rib (20, 22) along the longitudinal axis of the latter.
2. The method according to claim 1, characterized in that it includes a step during which a band blank (12) is formed from a strip consisting of a wound band (2), the width of which corresponds to one of the dimensions of the member to be made, each of the blanks (1', 3') forming the band blank (12) being connected to the blanks which are adjacent to it through at least one connecting tab (4).
3. The method according to claim 2, characterized in that the blanks (1', 3') are positioned so that their longitudinal axis (xx') is oriented perpendicular to the longitudinal axis (yy') of the band blank (12).
4. The method according to any of the preceding claims, characterized in that the band blank (12) moves, along its longitudinal axis (yy') in front of heating means (P₂) localized in areas (10) positioned on its transverse edges, so as to carry out an annealing operation on at least one longitudinal band (10) of the band blank (12).
5. The method according to any of the preceding claims, characterized in that the localized heating means consist of a laser beam generator (P₂).
6. The method according to the preceding claims, characterized in that after the heating phase (II), a rolling operation (III) is performed at the end of the branches of the members, so as to form hinges (5, 7, 15, 8).
7. The method according to claim 6, characterized in that two tabs (13) of a same end of a pivoting member (3) are wound up so as to form a double hinge (15), i.e. an internal hinge (15a) intended to receive an axis of rotation (16) common with the main member (1) and an external hinge (15b) intended to receive an abutment axis (18).
8. The method according to any of claims 6 or 7, characterized in that it includes a step consisting of welding the end of the branch, once the latter is wound on the member on which it is formed.
9. The method according to claim 7, characterized in that this weld is carried out with a laser beam generator.
10. The method according to any of the preceding claims, characterized in that it includes a step (IV) after the annealing operation (II), during which longitudinal stiffening ribs (20, 22) are made on the branches (5, 13) of the main (1) and pivoting (3) members.
11. The method according to any of the preceding claims, characterized in that it includes a last phase (V) during which the connecting tabs (4) of the members are removed.

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