CH708214B1 - Clasp with folding clasp. - Google Patents

Abstract

The present invention relates to a folding clasp for a bracelet comprising a fixed blade (1), at least a first folding blade (2) hinged to a first end of the fixed blade (1) and locking means of the first folding blade (2) in the folded position on the fixed blade (1). The locking means comprise at least one rigid roller (5) pivotally mounted and sliding on a transversely fixed axis on one of the fixed blade (1) or the first folding blade (2) and a corresponding elastic element binding the roller (5) in a first position on the axis and at least one shoulder (23) corresponding carried by the other of the fixed blade (1) or the first folding blade (2) and intended to cooperate with the roller (5). ). The roller (5) has a conical portion (51). The shoulder (23) and the conical portion (51) of the corresponding roller (5) are shaped so that when the first folding blade (2) is folded over the fixed blade (1), the shoulder (23) comes into abutment against the roller (5) and in particular against the conical portion (51) and so that a force exerted on the first folding blade (2) perpendicular to the axis and directed towards the fixed blade (1) causes the displacement of the roller (5) on the axis against the action of the corresponding elastic element, the roller (5) being constrained by the corresponding shoulder (23) cooperating with the conical portion (51) of the roller (5), in a second position in which the corresponding shoulder (23) is no longer in abutment against the conical portion (51), the first folding blade (2) can be completely folded on the fixed blade (1). The roll (5) is then returned to its first position by the corresponding elastic member to retain the first folding blade (2) and prevent any movement thereof relative to the fixed blade.

Description

Description: [0001] The subject of the present invention is a clasp with a folding clasp for a bracelet and in particular a wristwatch.

A clasp of this type is for example described in document CH 676 415 and comprises a fixed base plate at the ends of which are articulated first and second movable blades. To lock the movable blades in the folded position on the fixed blade, each of said movable blades is provided at its free end with a nose capable of catching on a corresponding transverse bar fixed on the fixed blade. Said bars are capable of pivoting on themselves when the nozzles are hooked. When a movable blade is folded over the fixed blade, the tip of the nose of said movable blade comes into contact with a generatrix of the bar. By pressing on the movable blade and on the spout, a force is exerted on the bar which pivots until it is locked at the bottom of the housing formed by the spout. The movable blades therefore work by elasticity and sliding to close the clasp. This type of closure therefore imposes particular constraints on the movable blades in order to give them the necessary elasticity. In addition, although the wear resistance of such a clasp is good, the tip of the nose and the bars are elements having a certain fragility and a lower resistance to wear.

The object of the present invention is to overcome these disadvantages, and to achieve a clasp folding clasp that is safe, effective, wear resistant, easy to use while remaining aesthetic and can be achieved in a wide variety of materials.

The present invention relates to a clasp according to claim 1, in particular, a folding clasp for a bracelet comprising a fixed blade, at least a first folding blade hinged to a first end of the fixed blade and locking means of the first folding blade in the folded position on the fixed blade, characterized in that the locking means comprise at least one rigid roller pivotally mounted and sliding on an axis fixed essentially transversely on one of the fixed blade or said at least one a first folding blade and a corresponding elastic element constraining said at least one roller in a first position on the axis and at least one corresponding shoulder carried by the other of the fixed blade or of said at least one first folding blade and intended for cooperate with said at least one roller; in that the at least one roller has a conical portion; and in that said at least one shoulder and said conical portion of said at least one corresponding roller are shaped such that when said at least one first folding blade is folded over the fixed blade, said at least one shoulder abuts against said at least one roller and in particular against the conical portion and such that a force exerted on the first folding blade substantially perpendicular to the axis and directed towards said fixed blade causes the displacement of said at least one roller on the axis against the action of the corresponding elastic element, said at least one roller being constrained by said at least one corresponding shoulder cooperating with the conical portion of said at least one roller, in a second position in which said at least one corresponding shoulder is no longer stop against said conical portion, said at least one first folding blade being completely folded on the fixed blade and so that said at least one roller biased into its first position by the corresponding elastic member retains the first folding blade and prevents any movement thereof relative to the fixed blade.

The accompanying drawings illustrate schematically and by way of example several embodiments of a clasp folding clasp according to the present invention.

Fig. 1 illustrates a first embodiment of the clasp according to the invention in the open position, the clasp blades being deployed.

Fig. 2 is a top view of the clasp according to the first embodiment in the closed position.

Figs. 3a, 3b are sectional views along the axes A-A and B-B respectively of the clasp illustrated in FIG. 2.

Figs. 4a, 4b are views in section along the axes A-A and B-B respectively of the clasp illustrated in FIG. 2 in the opening phase.

Figs. 5a, 5b are sectional views along the axes A-A and B-B respectively of the clasp illustrated in FIG. 2 in the open position.

Figs. 6a, 6b are sectional views along the axes A-A and B-B respectively of the clasp illustrated in FIG. 2 in the closing phase.

Fig. 7 illustrates a second embodiment of the clasp according to the invention in the open position, the blades of the clasp being deployed.

Fig. 8 is a top view of the clasp according to the second embodiment in the closed position.

Figs. 9a, 9b are views in section along the axes A-A and B-B, respectively, of the clasp illustrated in FIG. 8.

Figs. 10a, 10b are views in section along the axes A-A and B-B respectively of the clasp illustrated in FIG. 8 in the opening phase.

Figs. 11a, 11b are views in section along the axes A-A and B-B, respectively, of the clasp illustrated in FIG. 8 in the open position.

Figs. 12a, 12b are sectional views along the axes A-A and B-B respectively of the clasp illustrated in FIG. 8 in the closing phase.

A folding clasp according to a first embodiment of the invention and as illustrated in FIG. 1 comprises a fixed blade 1 on which are articulated a first movable blade 2 and a second movable blade 3.

Preferably, the fixed blade 1 has two longitudinal members 10,11, substantially parallel. The first movable blade 2 is articulated at the first ends 10a, 11a, longitudinal members 10, 11 of the fixed blade 1, while the second movable blade 3 is articulated at the second ends 10b, 11b, longitudinal members 10, 11 of the fixed blade 1. The first and second movable blades 2, 3 are articulated to the fixed blade 1 by means for example of fixing bars 41. It is obvious that any other suitable means of articulation and known to those skilled in the art could be used to articulate the movable blades 2, 3 to the fixed blade 1.

Each of the first and second movable blades 2, 3 has a free end 20, 30. These free ends 20, 30 each comprise fixing means 22 for connecting the first and second movable blades 2, 3 to a strand of a bracelet, especially the two strands of a watch strap (not shown). Obviously for the skilled person, this bracelet can be elastic or not, in any material or have any other suitable form. In this first embodiment, said attachment means 22 comprise a fixing ring 22a for receiving a fastening bar 22b of a bracelet strand, said bar 22b being held in the ring by a screw 22c.

Preferably, the fixed blade 1 also has first and second bridges 12, 13 extending transversely between the longitudinal members 10,11 and welded to said longitudinal members 10,11. Alternatively, said bridges 12,13 could have come from a room with the longitudinal members 10,11, screwed or fixed in any other suitable manner to said longitudinal members 10,11. Each of the first and second movable blades 2, 3 has a recess 21,31 shaped to cooperate respectively with the first and second bridges 12, 13 of the fixed blade 1 when said first and second movable blades 2, 3 are in their folded position on the fixed blade 1.

Preferably, the fixed blade 1, in particular, the longitudinal members 10,11, the first and second bridges 12,13 and the first and second movable blades 2, 3 are shaped so that the first and second movable blades 2 , 3 can be folded on the fixed blade 1 between the longitudinal members 10, 11 of said fixed blade 1 so that once folded, the fixed and movable blades 1, 2, 3 are essentially in the same plane and their thickness does not exceed that of the fixed blade 1 (see Fig. 3a).

The clasp according to the invention further comprises locking means for locking the first and second movable blades 2, 3 in their folded position on the fixed blade 1. In the first embodiment, these locking means comprise first and second rigid rollers 5, 6 slidably mounted and pivotable on an axle 7 fixed transversely to the fixed blade 1 between the longitudinal members 10, 11 and between the bridges 12, 13. In this first embodiment, the axle 7 is fixed by its ends in holes 14, 15 of the longitudinal members 10, 11 respectively. The first and second rollers 5, 6 are arranged to pivot freely on the axis 7. The first and second rollers 5, 6 are arranged to slide longitudinally with respect to the axis 7 and are subjected to the action of a force elastic 8 which tends to constrain them in a first position. In the first embodiment, the rollers 5, 6 are pushed out of the axis 7 in the direction of the longitudinal members 10, 11 respectively by a spring element 8 mounted on the axis 7 coaxially with it and forming said elastic force.

Each of the first and second rollers 5,6 has a conical portion 51,61. As illustrated in the figures, in this first embodiment, the rollers 5, 6 are oriented so that the apex of their respective conical portion 51, 61 is directed towards the inside of the longitudinal members 10, 11 of the fixed blade 1. In other words, the conical portions 51, 61 of the first and second rollers 5, 6 do not face each other.

The free end 20 of the first movable blade 2 has a first shoulder 23 and a second shoulder 24. The first and second shoulders 23, 24 of the first movable blade 2 are intended to cooperate with the first and second rollers 5 , 6 and respectively with the conical portions 51,61 of said rollers 5, 6. Similarly, the free end 30 of the second movable blade 3 has a first shoulder 33 and a second shoulder 34. The first and second shoulders 33 , 34 of the second movable blade 3 are also intended to cooperate with the first and second rollers 5, 6 respectively and in particular with the conical portions 51, 61 of said rollers 5, 6. The shoulders 23, 24, 33, 34 of the first and second movable blades 2, 3 can be obtained for example by cutting in said movable blades 2, 3 or by any other appropriate means.

The first and second shoulders 23, 24 (33, 34) of the first (second) movable blade 2 (3), the rollers 5, 6 and in particular their conical portion 51, 61 and the spring 8 are formed of so that when the first (second) movable blade 2 (3) is folded over the fixed blade 1, the first and second shoulders 23, 24 (33, 34) respectively abut against the conical portions 51, 61 of the rollers 5, 6 (Fig. 6a) which are in their first position constrained by the spring 8. When a force (pressure) is exerted on the first (second) movable blade 2 (3) substantially perpendicular to the axis 7 and directed towards the fixed blade 1, the first and second shoulders 23, 24 (33, 34) each cooperate respectively with the conical portions 51, 61 of the rollers 5, 6 to constrain said rollers 5, 6 to move on the axis 7 against the action of spring 8 (Figure 4b). The connection between the shoulders 23, 24 and the rollers 5, 6 is a point connection: during the displacement of the rollers 5, 6 under the pressure exerted on the first (second) movable blade 2 (3), said rollers slide on the axis 7 and can also simultaneously pivot on said axis 7.

Following the displacement of the rollers 5, 6 on the axis 7, they are in a second position in which the first and second shoulders 23, 24 (33, 34) of the first (second) movable blade 2 ( 3) are no longer in abutment with the conical portions 51, 61 of said rollers 5, 6 (FIG 4a). In this position, by maintaining the force exerted on the first (second) movable blade 2 (3), it can be fully folded over the fixed blade 1, in a position where the bridge 12 (13) of the fixed blade 1 is entirely in the recess 21 (31) of the first (second) movable blade 2 (Fig. 3a). In this position, the rollers 5, 6 are then no longer retained by the first and second shoulders 23, 24 (33, 34) of the first (second) movable blade 2 (3) and resume their first position under the action of the 8. Moving on the axis 7 to resume their first position, the rollers 5, 6 and in particular their conical portion 51, 61 respectively cover the first and second shoulders 23, 24 (33, 34) of the first (second) movable blade 2 (3) preventing any movement of said first (second) movable blade 2 (3) relative to the fixed blade 1, said first (second) movable blade 2 (3) is thus locked in its folded position on the fixed blade 1 (Fig. 3a and 3b). The above description and features are also valid for the second movable blade 3 and its first and second shoulders 33, 34.

Closing of the clasp according to the first embodiment will now be described with reference to FIGS. 1 and 5a to 6b.

In the unlocked initial position of the clasp according to the first embodiment illustrated in FIG. 1, the first and second movable blades 2,3 are unfolded relative to the fixed blade 1. From this unlocked position, the first movable blade 2 can be folded over the fixed blade 1 to bring the first and second shoulders 23, 24 in contact with the rollers 5, 6 and in particular their conical portion 51, 61. In this position illustrated in FIGS. 6a and 6b, the first and second shoulders 23, 24 abut against the rollers 5, 6. The user then exerts pressure on the first movable blade 2 perpendicular to the axis 7 and directed towards the fixed blade 1. Under the effect of this force, the rollers 5, 6 constrained by the first and second shoulders 23, 24 slide on the axis 7 against the action of the spring 8 in a position where said first and second shoulders 23, 24 are not more in abutment against the rollers 5, 6 and where the first movable blade 2 can be fully folded between the longitudinal members 10, 11 of the fixed blade 1. In this position, the rollers 5, 6 are no longer constrained by the first and second shoulders 23, 24 and slide again on the axis 7 under the action of the spring 8 to resume their initial position in which they now prevent any movement of the first movable blade 2 relative to the fixed blade 1.

The second movable blade 3 is then folded and locked in the same way on the fixed blade 1. Once the two movable blades 2, 3 fully folded on the fixed blade 1 and held in this position by the rollers 5, 6 retaining the shoulders 23, 24, 33, 34, the clasp according to the first embodiment is in its locked position as illustrated in FIGS. 2, 3a and 3b.

The locking of the first movable blade 2 is independent of the locking of the second movable blade 3 and vice versa. The clasp according to the first embodiment can be locked by folding the movable blades 2,3 successively as described above (first first and then second or vice versa) or simultaneously.

The unlocking of the clasp according to the first embodiment will now be described in detail with reference to FIGS. 4a and 4b.

From the locked position of the clasp illustrated in FIGS. 2, 3a and 3b, the user exerts a traction force on the first movable blade 2 directed perpendicularly to the axis 7 and away from the fixed blade 1 (via, for example, the strand of the bracelet which is connected thereto). In the first embodiment, the rollers 5, 6 and in particular their conical portion 51, 61 are also shaped so that, under the effect of this pulling force, the first and second shoulders 23, 24 of the first blade mobile 2 come into contact with said conical portions 51, 61 and force the rollers 5, 6 to move on the axis 7 against the action of the spring 8. As during the locking, the connection between the shoulders 23, 24 and the rollers 5, 6 is a point link.

Following the displacement of the rollers 5, 6 on the axis 7, they are in a position in which the first and second shoulders 23, 24 of the first movable blade 2 are no longer in abutment against the conical portions 51 , 61 said rollers 5, 6. In this position, maintaining the (pulling) force exerted on the first movable blade 2, it can be fully unfolded relative to the fixed blade 1. It is the same for the deployment of the second movable blade 3. Once the two blades deployed, the clasp is again in its unlocked position shown in FIG. 1.

As when locking, the unlocking of the first movable blade 2 is independent of the unlocking of the second movable blade 3 and vice versa. The clasp according to the first embodiment can be unlocked by deploying the movable blades 2, 3 successively as described above (first first and then second or vice versa) or simultaneously.

Preferably and as illustrated in the figures, the rollers 5, 6 are shaped so that at any time a cylindrical portion 52 of the first roller 5 covers a cylindrical portion 62 of the second roller 6. This allows to completely hide the spring 8 and thus to protect it from dust and wear and to give a more aesthetic appearance to the clasp.

[0025] A second embodiment will now be described in detail with reference to FIGS. 7 to 12b. The elements of this second embodiment similar to those described in relation to the first embodiment are designated by the same references.

In this second embodiment, the rollers 5 ', 6' part of the locking means of the clasp each comprise a conical portion 51 ', 61'. As in the first embodiment, the rollers 5 ', 6' are arranged in this second embodiment so that their conical portion 51 ', 61' do not face each other.

In this second embodiment, the conical portions 51 ', 61' are shaped so that when the first (second) movable blade 2 (3) is folded over the fixed blade 1, the first and second shoulders 23 , 24 (33, 34) of said first (second) movable blade 2 (3) respectively abut against the conical portions 51 ', 61' of the rollers 5 ', 6' which are in the first position under the action spring 8 (Fig. 12a). When a force (pressure) is exerted on the first (second) movable blade 2 (3) substantially perpendicular to the axis 7 'and directed towards the fixed blade 1, the first and second shoulders 23, 24 (33, 34) each cooperate respectively with the conical portions 51 ', 61' of the rollers 5 ', 6' to constrain said rollers 5 ', 6' to move on the axis 7 'against the action of the spring 8. The connection between the shoulders 23, 24 and the rollers 5 ', 6' is a point connection: during the displacement of the rollers 5 ', 6' under the pressure exerted on the first (second) movable blade 2 (3), said rollers slide on the axis 7 'and can also simultaneously pivot on said axis 7.

Following the displacement of the rollers 5 ', 6' on the axis 7 ', they are in a second position in which the first and second shoulders 23, 24 (33, 34) of the first (second) blade mobile 2 (3) are no longer in abutment against the conical portions 51 ', 61' of said rollers 5 ', 6'. In this position, by maintaining the force exerted on the first (second) movable blade 2 (3), it can be fully folded over the fixed blade 1, in a position where the bridge 12 (13) of the fixed blade 1 is entirely in the recess 21 (31) of the first (second) movable blade 2. In this position, the rollers 5 ', 6' are then no longer retained by the first and second shoulders 23, 24 (33, 34 ) of the first (second) movable blade 2 (3) and resume their first position under the action of the spring 8. By moving on the axis 7 'to resume their first position, the rollers 5', 6 'respectively come covering the first and second shoulders 23, 24 (33, 34) of the first (second) movable blade 2, 3 preventing any movement of said first (second) movable blade 2 (3) relative to the fixed blade 1. Said first (Second) movable blade 2 (3) is thus locked in its folded position on the fixed blade 1 (Figures 9a and 9b). The above description and features are also valid for the second movable blade 3 and its first and second shoulders 33, 34.

Thus, in this second embodiment, the locking of the clasp is in all respects similar to the locking of the clasp according to the first embodiment.

It is the unlocking of the clasp that distinguishes the first and second embodiments. Indeed, in this second embodiment, the rollers 5 ', 6' and in particular the conical portions 51 ', 61' are shaped so that, from the locked position of the clasp illustrated in FIG. 9a (the two movable blades 2, 3 locked in their folded position on the fixed blade 1), a force exerted by the user on one or both movable blades 2, 3 and directed perpendicularly to the axis 7 'and away from the fixed blade 1 does not cause the deployment of the movable blades or the opening of the clasp. To do this and as illustrated in the figures, the rollers 5 ', 6' each have a cylindrical portion 52, 62 arranged to cooperate with the shoulders 23, 24, 33, 34 of the first and second movable blades 2, 3 in their folded position. and hold them in this position. The presence of the cylindrical portions 52, 62 causes that the point link which allows closing of the clasp can not take place for its opening. Thus, unlike the first embodiment described above, the clasp according to the second embodiment can not be unlocked by pulling simultaneously or successively on the movable blades 2, 3.

To allow the unlocking of the clasp according to the second embodiment, the locking means further comprise two push buttons 9. Each push button 9 is fixed integrally to the end of a rod 91 slidably mounted on the axis 7 '. In this embodiment, the axis 7 'is itself arranged to pass through the longitudinal members 10, 11 forming the fixed blade 1 via two through holes 92 in which are driven two sleeves 93 respectively. The rods 91 each slide in said sleeves 93. The free end 94 of each of the rods is arranged to cooperate with the rollers 5 ', 6'.

To unlock the clasp according to the second embodiment, from the locked position of the clasp illustrated in Figs. 8, 9a, 9b, the user actuates the two push buttons 9 simultaneously. The push buttons 9 each drive the rods 91 which slide on the axis 7 '. Under the stress of said rods 91, the rollers 5 ', 6' then move on the axis 7 'against the action of the spring 8 in a position where they no longer retain the movable blades 2, 3, in particular in a position where the cylindrical portions 52, 62 no longer cooperate with the shoulders 23, 24, 33, 34 of the first

Claims (10)

and second movable blades 2, 3. Thus, said movable blades 2, 3 can be fully unfolded with respect to the fixed blade 1. [0033] As illustrated in the figures, in this embodiment, the movable blades 2, 3 have preferably notches 25, 35 at their respective shoulders 23, 24, 33, 34 to make them adjustable and thus reduce or eliminate the residual clearance between the components of the clasp when it is locked. In this second embodiment also, the rollers 5 ', 6' are arranged so that in all their positions, they completely cover the spring 8, thus protecting said spring 8 from dust and wear and offering a clasp more aesthetic. The force required for locking and unlocking the clasp according to the invention and as described in the first and second embodiments depends mainly on the elastic force 8. [0036] The two embodiments described below above comprise two movable blades respectively hinged at each end of the fixed blade. It is obvious however that in a variant the clasp according to the invention could comprise a single movable blade. Similarly, alternatively, the locking means of the clasp according to the invention may have only one roller associated with a single pusher in the case of the second embodiment. Also alternatively, the roller (s) may (t) be carried by the blade (s) mobile (s) while the shoulder (s) corresponding will be (in) then worn by the fixed blade. In another variant, the fixed blade of the clasp according to the invention may be in one piece and have any suitable shape. In the two embodiments described above, the two rollers are arranged on their axis so that their respective conical portion do not face and so that the elastic element holding them in their first position is consisting of a single spring acting simultaneously on the two rollers. Alternatively, the rollers could be arranged in such a way that their respective conical portions face each other on the axis 7. In this case, the first position of the rollers corresponds to a position where they are pushed against each other on the axis and the elastic element may consist of two springs respectively acting on one of the rollers to maintain it in said first position. Preferably, the clasp and its components are shaped so that there is no residual clearance when said clasp is in its locked position thus avoiding said components to move and the user the feeling of a clasp no reliable. The clasp according to the present invention offers many advantages: its closure is easy, it is adaptable to any type of bracelet, the arrangement and operation of the locking means guarantee good resistance to wear. In addition, it has a simple construction and an optimized size since it is compact and proportioned once in the locked position while providing sufficient deployment in the unlocked position. Finally, the clasp according to the invention and in particular the fixed and movable blades can be made of a wide variety of materials. The above embodiments have been described by way of example only, variations may be made without departing from the scope of the claims. claims 1. Clasp folding clasp comprising a fixed blade (1), at least a first folding blade (2) articulated at a first end of the fixed blade (1) and locking means of the first leaf blade (2) in position folded on the fixed blade (1), characterized in that the locking means comprise at least one rigid roller (5; 5 ') pivotally mounted and sliding on an axle (7; 7') fixed transversely to one of the fixed blade (1) or of said at least one first folding blade (2), a corresponding elastic element (8) constraining said at least one roller (5; 5 ') in a first position on the axis (7; '), and at least one corresponding shoulder (23) carried by the other of the fixed blade (1) or of said at least one first leaf blade (2) and intended to cooperate with said at least one roller (5; '); in that the at least one roller (5; 5 ') has a conical portion (51; 51'); and in that said at least one shoulder (23) and said conical portion (51; 51 ') of said at least one corresponding roller (5; 5') are shaped such that when said at least one first folding blade (2 ) is folded over the fixed blade (1), said at least one shoulder (23) abuts against said at least one roller (5; 5 ') and in particular against the conical portion (51; 51') so that a force exerted on the first folding blade (2) perpendicular to the axis (7; 7 ') and directed towards said fixed blade (1) causes said at least one roller (5; 5') to move on the axis ( 7; 7 ') against the action of the corresponding elastic element (8), said at least one roller (5; 5') being constrained by said at least one corresponding shoulder (23) cooperating with the conical portion (51; 51 ') of said at least one roller (5; 5'), in a second position in which said at least one corresponding shoulder (23) is no longer abutted against the said conical portion (51; 51 '), said at least one first folding blade (2) being completely folded over the fixed blade (1) and so that said at least one roller (5; 5 ') returned in its first position by the corresponding elastic element (8) retains the first folding blade (2) and prevents any movement thereof relative to the fixed blade. 2. Clasp according to claim 1, characterized in that the shoulder (23) and the conical portion (51) of the at least one roller (5) are further shaped so that when the first folding blade (2) is completely folded over the fixed blade (1) and held in this position by said at least one roller (5) which is in its first position, a force exerted on the first folding blade (2) perpendicular to the axis (7) and moving away from the fixed blade (1) causes said at least one roller (5) to move on the axis (7) against the action of the corresponding elastic element (8), said at least one roller (5) being constrained by said at least one corresponding shoulder (23) cooperating with the conical portion (51) of said at least one roller (5), in its second position in which said at least one shoulder (23) is no longer abutted against said conical portion (51), the first folding blade (2) being complete Unfolded relative to the fixed blade (1). Clasp according to one of the preceding claims, characterized in that the locking means comprise two rigid rollers (5, 6) each intended to cooperate with a corresponding shoulder (23, 24). 4. Clasp according to claim 1, characterized in that said at least one shoulder (23) and the conical portion (51 ') of said at least one roller (5') are further shaped so that when the first folding blade (2) is completely folded over the fixed blade (1) and held in this position by said at least one roll (5 ') which is in its first position, a force exerted on the first folding blade (2) substantially perpendicular to the axis (7 ') and away from the fixed blade (1) does not cause displacement on the axis (7') of the at least one roller (5 ') against the action of the elastic element ( 8) and does not allow the first folding blade (2) to be completely unfolded relative to the fixed blade (1); and in that the locking means further comprise at least one corresponding pusher (9) arranged to cooperate with said at least one roller (5 ') so that pressure on said pusher (9) causes said pusher to move. at least one roller (5 ') on the axis (T) from its first to its second position in which it no longer blocks the first movable blade (2). 5. Clasp according to claim 4, characterized in that the locking means comprises two rigid rollers (5, 6) and two corresponding pushers (9) arranged to each cooperate with a respective roller. 6. Clasp according to claim 5, characterized in that the two rollers (5, 6) are arranged on the axis (7) so that their respective conical portion (51,61) face each other; and in that the elastic element (8) is composed of two springs each acting on a roller (5, 6) respectively to maintain them in their first position on the axis (7). 7. Clasp according to claim 5, characterized in that the two rollers (5,6) are arranged on the axis (7) so that their respective conical portion (51,61) do not face; and in that the elastic element (8) is composed of a single spring acting simultaneously on each of the rollers (5,6) to maintain them in their first position on the axis (7). Clasp according to one of the preceding claims, characterized in that the roller or rollers (5, 6) are carried by the fixed blade (1) while the shoulder (s) (23, 24, 33, 34) is / are present at the free end (20) of the at least one movable blade (2). 9. Clasp according to one of the preceding claims, characterized in that it comprises a second folding blade (3) articulated to a second end of the fixed blade (1) independently of the first leaf blade (2). 10. Clasp according to one of the preceding claims, characterized in that the or folding blades (2, 3) further comprise at least one notch (25,35) at their respective shoulder (23,24,33). , 34) to make them adjustable and decrease the residual clearance between the components of the clasp in the locked position.