HK1193551B - Magnetic clasp - Google Patents

Description

Magnetic button

Technical Field

The present invention relates to a bracelet or wristband with a magnetic clasp comprising permanent magnets, and in particular to a watch bracelet comprising a magnetic clasp of this type.

Background

Figure 10d of the french patent with patent number 2834622 shows a bracelet with magnetic clasp comprising a first and a second flexible strip, the two strips being separable and arranged to overlap each other in the closed position of the bracelet. The bracelet further comprises two magnetic elements; the first bracelet strand comprises a fixed first magnetic element, while the second strand in the form of a hollow shaft comprises a second magnetic element (called "movable element") arranged to slide longitudinally as a friction tight fit within the hollow shaft. When the bands are in the closed position, the two magnetic elements oppose each other and attract each other. The two magnetic elements thus enable the two bands to be fastened to each other in the closed position of the bracelet. Furthermore, the length of the bracelet can be adjusted by sliding the movable magnetic element inside its hollow shaft. In addition, this patent document teaches that the bracelet length can be adjusted by sliding one strap longitudinally with respect to the other in the closed position of the bracelet. Even more, if the attraction exerted by the fixed magnetic element on the movable magnetic element is sufficient to overcome the friction, the sliding of one band on the other band causes the movable magnetic element to slide within its hollow sheath.

However, this known solution has certain drawbacks. Even if the attraction between the magnetic elements is not sufficient to overcome the friction, it will not be possible to adjust the bracelet length. Conversely, if the movable magnetic element slides too easily inside the hollow shaft, the bracelet may not be sufficiently tightened.

Disclosure of Invention

The object of the present invention is to overcome the drawbacks of the prior art just described. The present invention achieves this object by providing a bracelet with a magnetic clasp in accordance with the appended claim 1.

One advantage of the present invention is that the length of the bracelet can be selected simply by selecting to place any one of a plurality of second magnetic circuit portions in an overlapping position with the first magnetic circuit portion. In addition, if none of the second magnetic circuit portions is directly superposed on the first magnetic circuit portion, the mutual attraction existing between the first magnetic circuit portion and the nearest second magnetic circuit portion is generally sufficient to bring said second portion into the superposed position.

Another advantage of the invention is that the use of a full row of bipolar magnets instead of a single magnet enables the contact surfaces of the two ends to be better fastened to each other in the closed position of the bracelet. In addition, the presence of a yoke made of a soft ferromagnetic alloy in each magnetic circuit portion has the advantage of properly guiding the magnetic field and thus further increasing the mutual attraction force between the first and second magnetic circuit portions.

According to an advantageous variant of the invention, the length of the ferromagnetic yoke is greater than half the length of the end of the bracelet. Due to this feature, the strip-shaped end portion may be flexible in the length direction and relatively rigid in the width direction. This feature has the advantage of enabling the bracelet to adopt the shape of the wrist and to ensure proper adhesion between the contact surfaces in the closed position of the bracelet.

According to another advantageous variant of the invention, the space between two second magnetic circuit portions is at least equal to three quarters of the width of one of the second magnetic circuit portions. This feature has the advantage of enabling the bracelet to adopt the shape of the wrist of the person wearing it.

According to an advantageous embodiment of the invention, several first magnetic circuit portions are integrally formed in the first end portion, said first portions being arranged parallel to each other and spaced apart from each other. This multiplication of the magnetic circuit portions proportionally increases the magnetic attraction force that joins the contact surfaces of the two end portions together in the closed position of the bracelet.

According to an advantageous variant of the latter embodiment, the first magnetic circuit portions integrally formed in the first end portion are spaced further apart from each other than the second magnetic portions integrally formed in the second end portion. Even more, in the closed position, the first end is located on the outside of the loop formed by the bracelet and the second end is located on the inside. In these cases, it will be clear that the same given angle subtends a longer arc on the outer end than on the inner end. The feature that the first magnetic circuit portions are spaced further from each other than the second magnetic portions thus corrects the overlapping effect of the ends and ensures that the first and second magnetic circuit portions are properly aligned in the closed position of the bracelet.

According to a preferred embodiment of the latter variant above, the space between the second magnetic circuit portions gradually decreases away from the extremity of the second end of the bracelet. Even further, the further the second magnetic circuit portion (on which the first magnetic circuit portion is superposed) is from the end of the bracelet, the tighter the bracelet will be, or in other words, the smaller the diameter of the bracelet will be. In these cases, it will be clear that the tighter the bracelet, the more necessary it will be to reduce the space between the second magnetic circuit portions in order to correct the overlapping effect of the ends and to ensure that the first and second magnetic circuit portions are properly aligned in the closed position of the bracelet.

According to another advantageous variant of the above embodiment, the second magnetic circuit portions each comprise a row of bipolar magnets arranged between the ferromagnetic yoke of the second portion and the contact face of the second end portion; the polarization directions of the rows of magnets are parallel to each other and perpendicular to the contact face of the second end portion. In addition, the rows of magnets of the first and second magnetic circuit portions each have the same number of magnets; the magnets are arranged such that in the closed position of the bracelet the magnets of the first part each match the magnets of the second part, the two matching magnets overlapping and being polarised in the same direction. In the above configuration, the feature that the first and second magnetic circuit portions each include a magnet further increases the magnetic attraction force between the contact surfaces.

According to another advantageous embodiment of the invention, the direction of polarization of some of the magnets in a row of magnets is in the opposite direction to the direction of polarization of other magnets in the same row of magnets. This feature has the advantage of better guiding the magnetic field in the magnetic circuit portion. According to an advantageous variant of the latter embodiment, each magnet of a row of magnets is polarized in the opposite direction of its nearest neighbour. The latter feature has the effect of shortening the path travelled by the magnetic field and thus enhancing the magnetic field in close proximity to the contact surface.

Drawings

Further characteristics and advantages of the invention will appear when reading the following description, given purely by way of non-limiting example, with reference to the accompanying drawings, in which:

figure 1 combines a top plan view and a partial side section view of a watch corresponding to an embodiment of a bracelet with magnetic clasp according to the invention, the two bracelet strands being shown in the open position to clearly show their ends.

Figure 2a shows a schematic perspective view of the watch of figure 1 in the closed position. The table itself is omitted for simplicity.

Figure 2b is a partial section view showing in more detail the magnetic clasp of the bracelet of figure 2a and in particular the overlapping of the two ends of the bracelet in the overlapping region.

Figure 3a is a schematic view of a magnetic clasp of a bracelet according to a second embodiment of the invention and showing in perspective the arrangement of the first and second magnetic circuit portions in the closed position of the bracelet.

Figure 3b is a partial front view of the embodiment of figure 3a showing in more detail the cooperation between the magnet of one of the first magnetic circuit portions and the magnet of one of the second magnetic circuit portions in the closed position of the bracelet.

Figure 4 is a schematic view of the magnetic clasp of the bracelet according to a third embodiment of the invention and showing a front view of the cooperation between the first and second magnetic circuit portions in the closed position of the bracelet.

Detailed Description

Referring to fig. 1, a watch according to a first embodiment of the invention is shown. The watch comprises a watch case 1 having two pairs of end lugs 3 to which two bracelet strands 5 and 6 are attached. In the described embodiment, the bands are made of an elastomer, which provides them with the flexibility required to wrap around the wrist of the person wearing the watch. The belts 5, 6 each comprise an end portion and these two end portions are referenced 8 and 9 in figures 1, 2a and 2b respectively. It will also be noted that in the closed position, as shown in the schematic views of fig. 2a and 2b, the ends overlap one another, thereby defining an overlap region. The end portions thus each have a contact surface arranged to abut the contact surface of the other end portion in the closed position of the bracelet. It will also be noted that in the overlapping area, the end 8 of the first strap (reference number 5) is located on the outside of the loop formed by the bracelet in the closed position, while the end 9 of the second strap (reference number 6) is located on the inside of this loop.

Considering now both fig. 1 and 2a, it is clear that when opening the bracelet strand, as shown in the top view of fig. 1, the contact surface of the first strand 5 is below the end 8, while the contact surface of the second strand 6 is on top of the second end 9. According to the present invention, the bracelet further comprises a first magnetic circuit portion integrally formed in the first end portion 8 and a plurality of second magnetic circuit portions integrally formed in the second end portion 9. Referring again to fig. 1, it can be seen that in the embodiment shown, the first end portion 8 has two first magnetic circuit portions (referenced 11a, 11b respectively), while the second end portion 9 comprises six second magnetic circuit portions 12a, 12b, 12c, 12d, 12e and 12 f. In general, any number of portions may be present, as will be appreciated by those skilled in the art. It may be noted, however, that the number of second magnetic circuit portions must be at least equal to two. In addition, the number of first magnetic circuit portions is preferably smaller than or equal to the number of second magnetic circuit portions. In general, a larger number of first and second magnetic circuit portions results in a larger attraction force and improved reliability. By way of example, a more reliable embodiment than the embodiment of fig. 1 may comprise 8 first magnetic circuit portions and sixteen second magnetic circuit portions. This latter embodiment would have the disadvantage of being somewhat more expensive.

Referring now to fig. 1, it can be seen that in the present example, the first magnetic circuit portions 11a, 11b are arranged parallel to and spaced apart from each other as are the second portions 12a, 12b, 12c, 12d, 12e, 12 f. It can also be seen that the magnetic circuit portions each extend over a length substantially equal to the width of the bracelet. Even more advantageously, the length of the magnetic circuit portion exceeds half the width of the bracelet. In addition, it can also be seen that in the example shown, the space separating the two second magnetic circuit portions 12a, 12b, 12c, 12d, 12e, 12f is at least equal to three quarters of the width of one of the second magnetic circuit portions. It will finally be noted that fig. 1 also indicates, by way of example, possible values of the size of the space separating the first or second magnetic circuit portion from its nearest neighbour. The figure shows the first magnetic circuit portions 11a and 11b separated by 4 mm. Furthermore, the second magnetic circuit portions 12a and 12b are separated by 3.405 mm, the second portions 12b and 12c are separated by 3.375 mm, the portions 12c and 12d are separated by 3.36 mm, the portions 12d and 12e are separated by 3.34 mm, and the last portions 12e and 12f are separated by 3.32 mm. These values illustrate the fact that the space between the second portions is preferably smaller than the space between the first portions 11a, 11 b. This advantageous feature compensates for the smaller radius of curvature of the second end in the closed position of the bracelet.

The values given above for the size of the space separating the two second magnetic circuit portions also illustrate the fact that the space between the second magnetic circuit portions preferably decreases progressively further away from the second end 9 of the bracelet. Even further, the further the second magnetic circuit portion (on which the first magnetic circuit portion is superposed) is from the end of the bracelet, the tighter the bracelet will be, or in other words, the smaller the diameter of the bracelet will be. In these cases, it will be clear that the tighter the bracelet, the more necessary it will be to reduce the space between the second magnetic circuit portions in order to correct the overlapping effect of the ends and to ensure that the first and second magnetic circuit portions are properly aligned in the closed position of the bracelet.

According to the invention, the magnetic circuit portions 11a, 11b, 12a, 12b, 12c, 12d, 12e, 12f all comprise soft ferromagnetic alloy yokes (in fig. 2b, reference numerals 14, 14b, 16a, 16b, 16c, 16d, 16e and 16f, respectively). As will be seen in more detail below, in the present example the yoke takes the form of a small rectangular plate arranged in the thickness of the bracelet, transverse to the longitudinal axis of the bracelet and parallel to the contact face with the other bracelet strand. According to the present invention, the first magnetic circuit portions 11a and 11b integrally formed in the first end portion of the bracelet each include a row of magnets. Further, in this example, the second magnetic circuit portion in the end portion of the bracelet is also provided with a magnet. As seen in more detail with respect to fig. 3a and 3b, each row of dipole magnets is arranged between one yoke and the contact surface with the other bracelet strand.

Considering now both fig. 1 and 2b, it can be appreciated that by longitudinally shifting one of the ends relative to the other, the bracelet can be made to have seven possible different lengths in the closed position. Fig. 2b shows that the first magnetic circuit portions 11a and 11b have been shown superposed on the second magnetic circuit portions 12e and 12 d. However, it can be seen that in order to obtain the shortest possible bracelet length, the first magnetic circuit portion 11b must be superposed on the second magnetic circuit portion 12 f. On the contrary, it can also be seen that the longest bracelet length can be obtained by superimposing the first magnetic circuit portion 11a on the second magnetic circuit portion 12 a. It may be noted that in the two positions just mentioned, only one of the first magnetic circuit portions cooperates with the second magnetic circuit portion, since the other first magnetic circuit portion is not located opposite the second magnetic circuit portion. Thus, it will be clear from the above that the magnetic clasp will be stronger at five positions corresponding to the length of the intermediate bracelet than at two end positions corresponding to the shortest length and the longest length, respectively.

Since the magnetic attraction force decreases with distance, this force is mainly exerted between the first and second magnetic circuit portions that are closest to each other. When these closest parts are usually sufficiently superposed, the magnetic force is first applied perpendicularly to the contact surface. Therefore, the attraction between the magnetic circuit portions has an effect of making the contact surfaces firmly adhere to each other. Furthermore, it will be clear that the magnetic attraction also resists any longitudinal sliding of the contact faces towards each other. This latter feature has the advantage of allowing the use of a flat contact surface between the bracelet strands and therefore the omission of notches or any other mechanical fixing means. It can therefore be said that the first and second magnetic circuit portions perform the function of a "magnetic slot".

Figures 3a and 3b are two partial schematic views of the arrangement of the first and second magnetic circuit portions forming the clasp of a bracelet according to a second embodiment of the invention. The first and second magnetic circuit portions used in this second embodiment may be the same as those used in the first embodiment described above. The difference between the first and second embodiments is mainly that for the second embodiment a larger number of first and second magnetic circuit portions are used. As shown in fig. 3a, the first magnetic circuit portions 111 are arranged parallel to each other and regularly spaced apart from each other. The same is true of the second magnetic circuit portion 112.

According to the invention, the first and second magnetic circuit portions 111, 112 each comprise a soft ferromagnetic alloy yoke (first portion reference 114 and second portion reference 116). In the described embodiment, the yoke takes the form of a small rectangular plate, as in the previous embodiments. They may be made, for example, by cutting laminated iron-cobalt alloy strips, such as those supplied by Arcelor Mittal @, under the name AFK 502. In the example described, the yoke has a length of 25.75 mm, a width of 4 mm and a thickness of 0.5 mm. As also shown in fig. 3a and 3b, in each magnetic circuit portion, a yoke is associated with a row of six magnets (magnet common reference 118). In this example, the magnet has a length of 4 mm, a width of 3.25 mm and a height of 1 mm. By way of example, the magnets used may be standard magnets made of neodymium iron boron.

Fig. 3a and 3b also show that the magnet 118 is arranged between the yoke 14 or 16 and the contact surface between the two bracelet strands (indicated by a dash-dot line in fig. 3 b). The magnets are regularly spaced on the yoke with a space of 1.25 mm between adjacent magnets. It can also be seen that the magnets of the first magnetic circuit portion 111 are shown in an overlapping position on the magnets of the second magnetic circuit portion 112. Thus, according to the illustrated embodiment, in the closed position of the bracelet, the magnets 118 of the first part each mate with the magnets 118 of the second part.

According to the invention, the magnets are all polarized perpendicular to the contact plane between the ends of the bracelet strand. In this connection, it can be seen that the perpendicular to the contact face is vertical in fig. 3a and 3 b. On the other hand, it will be clear that although magnets 118 are all vertically polarized, some of the magnets in a row of magnets are preferably polarized in the opposite direction to the other magnets in the row of magnets. Thus, some of the magnets 118 are also shown in fig. 3b as being polarized upward, while others are polarized downward (as indicated by the arrows). However, it will also be noted that two superposed magnets (or in other words, two matching magnets) are always polarised in the same direction. Finally, it will also be noted that in the example shown, each magnet 118 is polarized in the opposite direction to its nearest neighbor in the row of magnets. Referring again to fig. 3b, it can be seen that the direction of magnetization in the yoke is indicated by the arrow. As can be seen from the arrows, the just described arrangement of the magnet 118 and yokes 114, 116 reduces the magnetic path, thereby improving coupling while limiting magnetic contamination.

It is also clear that various changes and/or modifications apparent to those skilled in the art may be made to the embodiment forming the subject of the present description without departing from the scope of the invention as defined in the annexed claims. In particular, those skilled in the art will appreciate that second magnetic circuit portion 216 may not include any magnets. Even further, referring now to fig. 4, it can be seen that only the first magnetic circuit portion 214 includes a magnet 218.

Claims (10)

1. Bracelet or wristband with a magnetic clasp comprising first and second flexible end portions (8, 9) in the form of strap portions, the end portions being separable and arranged to overlap in a closed position of the bracelet such that the bracelet substantially forms a loop with an outer side and an inner side and such that the end portions (8, 9) define an overlapping region, the end portions each having a contact face arranged to abut a contact face of the other end portion in the overlapping region such that the first end portion (8) is located on the outer side of the loop and the second end portion (9) is located on the inner side, the bracelet comprising a first magnetic circuit portion (11 a, 11 b; 111; 211) integrally formed in the first end portion and a second magnetic circuit portion (12 a, 12b, 12c, 12 d) integrally formed in the second end portion, 12e, 12 f; 112, a first electrode; 212) -said first and second magnetic circuit portions are arranged to mutually attract and cooperate so as to join together said contact surfaces of said two ends (8, 9) in said closed position of said bracelet;

characterized in that said first and second magnetic circuit portions each comprise a soft ferromagnetic alloy yoke (14 a, 14b, 16a, 16b, 16c, 16d, 16e, 16 f; 114, 116; 214, 216) having an elongated shape and arranged transversely to said bracelet and parallel to said contact face of said end portion in which said magnetic circuit portions are integrally formed, in that said first magnetic circuit portion (11 a, 11 b; 111; 211) comprises a row of bipolar magnets (18A; 118A; 218A) arranged between the ferromagnetic yoke and said contact face of said first end portion (8), said row of magnets having a direction of polarization parallel to each other and perpendicular to said contact face of said first end portion, and the magnets being regularly spaced on the yoke, and in that a plurality of second magnetic circuit portions (12 a, 12b, 12c, 12d, 12e, 12 f; 112; 212) are integrally formed in said second end portion (9), the second portions are arranged parallel to each other and spaced apart from each other to enable selection of bracelet length.

2. Bracelet with magnetic clasp according to claim 1, wherein the length of the ferromagnetic yoke (14 a, 14b, 16a, 16b, 16c, 16d, 16e, 16 f; 114, 116; 214, 216) is greater than half the width of the end (8, 9) in the form of a strap.

3. Bracelet with magnetic clasp according to claim 1, wherein the space between two second magnetic circuit portions (12 a, 12b, 12c, 12d, 12e, 12 f; 112; 212) is at least equal to three quarters of the width of one of said second magnetic circuit portions.

4. Bracelet with magnetic clasp according to claim 1, wherein several first magnetic circuit portions (11 a, 11 b; 111; 211) are integrated in said first end (8), said first portions being arranged parallel to each other and spaced apart from each other.

5. Bracelet with magnetic clasp according to claim 4, wherein said first magnetic circuit portions (11 a, 11 b; 111; 211) are spaced apart from each other further than said second magnetic circuit portions (12 a, 12b, 12c, 12d, 12e, 12 f; 112; 212).

6. Bracelet with magnetic clasp according to claim 5, wherein the second magnetic circuit portions (12 a, 12b, 12c, 12d, 12e, 12 f; 112; 212) are more numerous than the first magnetic circuit portions (11 a, 11 b; 111; 211) and the space between them increases gradually towards the extremity of the second end (9).

7. Bracelet with magnetic clasps according to claim 1, wherein said second magnetic circuit portions (12 a, 12B, 12c, 12d, 12e, 12 f; 112; 212) each comprise a row of bipolar magnets (18B, 118B, 218B) arranged between a ferromagnetic yoke (16 a, 16B, 16c, 16d, 16e, 16 f; 116; 216) of said second portion and said contact face of said second end (9), the rows of magnets having a direction of polarization parallel to each other and perpendicular to said contact face of said second end, and wherein the rows of magnets of said first and second magnetic circuit portions (8, 9) each have the same number of magnets (18A, 18B; 118A; 118B; 218A, 218B) arranged so that in said closed position of the bracelet the magnets (18A; 118A; 218A) of said first portion can each interact with magnets (18B, 118B, 218B), the two matching magnets are superposed and polarized in the same direction.

8. The bracelet of claim 1, wherein the direction of polarization of some magnets in a row of magnets is in a direction opposite to the direction of polarization of other magnets in the same row of magnets.

9. The bracelet of claim 8, wherein each magnet in a row of magnets is polarized in an opposite direction to its nearest neighbor in the row of magnets.

10. Bracelet with magnetic clasp according to claim 1, wherein said first and second end portions (8, 9) each comprise an elastomeric layer in which said magnetic circuit portions (11 a, 11b, 12a, 12b, 12c, 12d, 12e, 12 f; 111, 112; 211, 212) are embedded.