Patent Publication Number: US-2017354212-A1

Title: Jewelry clasp having two fastening parts and use of said jewelry clasp, bracelet, and kit

Description:
The invention relates to a jewelry clasp comprising two cylindrical fastening parts that are designed to be complementary to one another, wherein the jewelry clasp can be closed in a closing position and each fastening part has a permanent magnet, as well as a housing with barbs and holding devices. These two fastening parts may each be attached in particular to one of the two ends of a bracelet. In another aspect, the invention relates to a bracelet comprising a jewelry clasp according to the invention, as well as a kit comprised of a plurality of bracelets, wherein the bracelets in the kit may have a jewelry clasp according to the invention. 
     It is consistent with general everyday experience that it is difficult to place a bracelet on one&#39;s own wrist. The reason for this is that the hand around the wrist of which the bracelet is to be fastened is no longer available to close the fastening of the bracelet. 
     Various types of bracelet fasteners are known in the prior art. These include jewelry clasps designed in two parts, one fastening part being attached to one end of the bracelet and the other fastening part being attached to the other end of the bracelet. To bring the jewelry clasps into a closing position, one fastening part will often have a hook-shaped structure which must be introduced in a suitable manner into the second fastening part to achieve the desired fixation. 
     One disadvantage of such hook fasteners is that the fastening parts are usually very small and are made of thin materials, which are sometimes processed poorly, in order to save on the cost of materials. In addition, such hooks do not usually have suitable guides to assist the user, so that the hook-shaped structure of one fastening part can reach the receptacle part of the other fastening part in a suitable manner. The handling of such a jewelry clasp from the prior art is therefore difficult, in particular when the fastener must be closed with just one hand. 
     It is also possible that the hook-shaped structure becomes stuck or hooked in the wrong position in the receiving structure of the other fastening part and this gives the user the impression that the jewelry clasp is properly closed. However, then with any movement or pulling on the fastening parts, it may happen that the fastening is released and the bracelet falls from the wearer&#39;s wrist, whether noticed or not. 
     There are also known jewelry clasps which are also designed in two parts so that the two fastening parts have an outside thread and an inside thread, so that such a jewelry clasp can be closed by rotating the two fastening parts together. However, everyday experience has taught us that it is very difficult to close such a rotary fastener in particular when only one hand is available, as mentioned above. The reason for this is that one of the two fastening parts must be secured, while the other fastening part must be rotated. This is difficult to manage with just one hand. 
     Another disadvantage of such a rotary fastener is also that it is not easy under the difficult conditions described above to accurately place the fastening part with the outside thread in exactly the correct position with respect to the fastening part with the inside thread, so that the rotary closure can be closed immediately. Instead, it is often the case that the one fastening part is inserted into the other fastening part with a certain angle of inclination so that the two fastening parts become engage and it is further made more difficult to close the jewelry clasp designed as a rotary fastener. Here again with such jewelry clasps it is important to be aware that the manufacturing of the two fastening parts that fit together must be carried out with a great precision and the two threads must not have any manufacturing related burrs which would make it more difficult to fasten the parts correctly. 
     In addition, jewelry clasps based on magnetic attraction between two magnets whose different poles are opposite one another are also known in the prior art. Such fasteners are usually also designed in two parts, where the two fastening parts each comprise a magnet with the magnets of mutually repellant poles being arranged opposite one another. The use of magnets in conjunction with jewelry clasps has the advantage that use of such a jewelry clasp is simplified because the magnetic force acting between the two fastening parts facilitates the approach of the two closure parts to one another. However, jewelry clasps based only on magnetic force are easy to open because the magnetic force of the commercial magnets that are available inexpensively is either limited or very expensive when using magnetic materials that generate greater magnetic forces. 
     Against the background of this prior art, the object of the present invention is to provide a jewelry clasp which does not have the disadvantages and shortcomings of the jewelry clasps described in the prior art while being simple and convenient to open and close with just one hand and ensuring a secure fastening even when there is a sudden pull. 
     This object is achieved by the features of claim  1 . Thus, according to the invention, a jewelry clasp having two fastening parts is provided, each comprising a permanent magnet and a housing, wherein the housing has an opening and opposite this there is a rear side such that the housing comprises a first area that is preferably cylindrical and a second area wherein the second areas of the fastening parts consist of barbs and holding devices designed to be complementary to one another, and wherein the jewelry clasps may be opened and may be closed in a closing position, such that in the closing position, one barb of a fastening pan is introduced into a holding device of the other fastening part, and the permanent magnets are in contact with one another. 
     It is provided in particular that a jewelry clasp has two fastening parts, such that the fastening parts each comprise a permanent magnet and a housing. The housing has an opening and a rear side opposite this opening. In addition, the housing has a cylindrical first and second area wherein the second area of the fastening parts consists of barbs and holding devices designed to be complementary to one another. The jewelry clasp may be opened and closed in the closing position, such that a barb of a fastening part is introduced into a holding device in the other fastening part in the closing position, and the permanent magnets are in contact with one another. 
     It is also preferable that the fastening parts each have a permanent magnet and a housing, such that the opening in the housing is opposite a rear side of the fastening part and the housing consists of a first cylindrical area and a second area such that the second area is formed by barbs and holding devices. The jewelry clasp according to the invention is characterized in that in a closing position of the jewelry clasp, there is one barb of a fastening part in a holding device of the other fastening part and the permanent magnets are in contact with one another. 
     When using the jewelry clasp according to the invention, a mechanical approach comprising the barb and holding devices and an approach based on magnetic force, which effectively facilitates the approach of the two fastening parts to one another, advantageously supplement one another. Due to this special design of the barbs and the holding devices, there is a magnetic force caused by the two permanent magnets between the fastening parts, bringing the two fastening parts into contact with one another, as well as the barbs and the holding devices, so that a particularly secure fastening of the jewelry clasp is ensured. Thus, through the combination according to the invention of the curved design of the intermediate spaces in the barbs, which are situated in the transitional area between the first area of the housing and the second area of the housing of the fastening parts achieves a synergistic effect with the attractive effect between the magnets caused by the magnetic force between the permanent magnets, this synergistic effect consisting of the fact that the two fastening parts automatically enter the preferred closing position due to the magnetic force because of the design of the barbs, wherein the closing position is surprisingly secure with regard to unwanted opening of the jewelry clasp. The curved shape of the intermediate spaces between the barbs is illustrated in  FIGS. 2 and 5  in particular. It has been found that the synergistic effect goes beyond what the average person skilled in the art would have expected for simple aggregation of a magnetic single fastener and a mechanical single fastener with regard to the strength and safety of the closing effects of the jewelry clasps according to the invention. 
     If the barbs of one fastening part pass through the opening in the housing of the other fastening part into these interspaces, the two fastening parts experience an attractive magnetic force due to this proximity. This draws the barbs into the interspace until the barbs are in form-fitting contact with the housing wall of the other fastening part from which they are moved further in the direction of the holding devices until they engage in the latter. Thus the jewelry clasp is in a closing position and a surprisingly secure closure of the piece of jewelry is ensured. In particular, the curved design of the fastening part interspaces, the barbs and the holding devices as well as the magnetic attractive force supplement one another to yield a surprisingly effective closing mechanism. When there is a sudden release of the form-fitting connection of the two permanent magnets, for example, the corresponding design of the barbs and the holding devices advantageously continues to ensure a secure fastening of the jewelry clasp. 
     In an advantageous embodiment of the invention, the second areas of the fastening parts comprise sliding surfaces which form an angle α with an imaginary axis of opening and closing that runs centrally in the fastening parts. It is preferable for the imaginary opening and closing axis running centrally in the fastening parts to be arranged centrally in the first cylindrical area and to extend from there into the second area. The term “centrally” in the sense of the present invention preferably means that the imaginary opening and closing axis passes through the midpoint of the circular base area of the fastening part and is the same distance from all points on the outside wall of the cylinder, such that this distance preferably corresponds to the radius of the circular base area. 
     It is additionally preferable for the sliding surfaces to be formed by the areas that are designed to be flat between the holding device and the transitional area between the first and second areas of the fastening part. This transitional area preferably correlates with the lowest area of the opening in the housing of the fastening part according to the invention. The sliding surfaces are preferably designed to be curved, so that the sliding surfaces of the two fastening parts of a jewelry clasp according to the invention slide into one another in a particularly low-friction manner when they encounter one another so that the barbs and holding devices of the fastening parts can engage in one another and form a surprisingly effective closure that cannot be released accidentally. Therefore, an unwanted unintentional release of the closure is prevented unexpectedly reliably, when said unwanted unintentional release could result in loss of the piece of jewelry, for example, if the unwanted opening of the fastening parts of the jewelry clasp is not noticed in time. It was completely surprising that the presence and design of the sliding surfaces as components of the fastening parts would make the insertion of the barbs into the openings in the housing particularly simple and would greatly facilitate the establishment of the closing position. 
     An imaginary straight line can be drawn into the plane spanned by the sliding surface, the arrangement of this straight line being illustrated with respect to the sliding surface in  FIG. 3 . Within the sense of the invention, it is preferred that the straight line forms an angle α with the imaginary axis of opening and closing, such that the position of this angle in relation to the imaginary axis and the straight line in the plane of the sliding surface is also shown in  FIG. 3 . 
     In another preferred embodiment of the invention, this angle α is greater than or equal to 25°. It has been found that the fastening effect of the jewelry clasp according to the invention leads to surprisingly good results in this angle range in particular and ensures a particularly secure connection of the ends of a piece of jewelry that are to be connected, for example. 
     The preferred angle size of greater than or equal to 25° in particular correlates with the magnetic attractive force of the two magnets of the fastening parts so that the structural design of the jewelry clasp corresponds especially effectively to the magnetic connection between the permanent magnets. Thus a particularly effective unexpected interaction between the mechanical closing effect and the magnetic closing effect is achieved. The inventors have discovered in particular that the combination of magnetic closing effect and mechanical closing effect leads to a synergistic closing effect of the closure as a whole which was not expected by the technical world. Instead it was previously assumed according to the prior art that it is sufficient to provide either a mechanical fastening mechanism or a magnetic fastening mechanism. However, investigations by the inventors have shown that precisely the combination of a magnetic closing effect with a mechanical closing effect results in a particularly effective and secure fastening mechanism, in particular for jewelry, but also for applications in other technical fields because the total force and closing effects are greater than the sum of the individual fastening mechanisms. This synergistic overall effect, which exceeds the individual effects, is manifested in particular when an axial force is applied to the closed jewelry clasp in the closing position in the direction of the intended axis of opening and closing. A conventional jewelry clasp having only a magnetic fastener, for example, could be opened accidentally in this case when the axial force exceeds the magnetic fastening force. Such an unintended opening in the case of an axial pull in the direction of the intended axis of opening and closing is rendered practically impossible with the jewelry clasp according to the invention due to the interaction of the magnetic attractive force between the two permanent magnets within the two fastening parts and the mechanical fastening mechanism comprised of barbs and holding devices. 
     In another preferred embodiment of the invention, the housing for the fastening parts consists of a first area with a closed exterior wall wherein this first area is connected to the rear side of the fastening part. It is additionally preferred for the barbs and holding devices to form the second area of the fastening parts. In the sense of this invention, the rear side of the fastening parts is advantageously a circular surface which is facing the piece of jewelry to be closed. This rear side forms a base plate for a fastening part. A first area of the fastening part which is cylindrical in design and comprises a closed exterior wall is connected to this base plate. 
     In the sense of this invention, this first cylindrical area of the jewelry clasp is also referred to as the bottom part. Its height, when considered from the base plate, amounts to approximately one-half the height of the fastening part. The second area of the fastening part is connected to the first area of the fastening part and forms the upper area of the fastening part. This is advantageously formed by barbs and holding devices. 
     It is preferable for each fastening part to have two barbs and two holding devices which are opposite one another and in contact with one another forming an angular distance of 180° to one another. The barbs of the upper area of the fastening part form an extension of the exterior wall of the lower area of the fastening part. The barbs are shaped like a walking stick. The stick area of the barb is formed by the exterior wall of the fastening part and preferably has the same thickness as the exterior wall of the lower cylindrical area of the fastening part. In comparison with a walking stick, the stick area of the barb is designed to be wider and flat. 
     The upper area of the barb forms a hook-shaped area corresponding to the handle in the case of a walking stick. The area of the barb where the fingers would be placed in the case of a walking stick corresponds to the holding device of the upper area of the fastening part. In the front area of the handle part of the barb, the thickness of the wall material becomes thinner, tapering at the center to a tip shaped like a line. This tip of the barb which is shaped like a line engages in the holding device of the other fastening part when in the closing position. 
     Between the two barbs of a fastening part there is a curved opening. The inside of this opening is designed so that in the approach of the two fastening parts, the barb of the other fastening part is inserted into this opening. Due to the approach of the two fastening parts, the magnetic force begins to act between the two fastening parts. Therefore the two fastening parts are pulled toward one another. It is preferable for the magnetic force to increase as the distance between the fastening parts is reduced. Due to the curved design of the opening of the fastening parts, the barbs are guided along the curved inside surface of the opening. The barb thus automatically enters the holding device of the barb on the other fastening part so that, in addition to the fastening effect, which is based on the magnetic force, a secure mechanical closure of the jewelry clasp is also ensured. 
     In another preferred embodiment of the invention, the housing for the fastening parts has an identical number of barbs and holding devices. It is preferable for each fastening part to have two barbs and two holding devices. The number  2  is especially preferred because this permits a symmetrical arrangement of the barbs and holding devices relative to one another and there is still enough space between the barbs for the two closure parts to approach one another and for the barb of one fastening part to be guided into its closing position by the corresponding design of the opening of the other fastening part. It has been found that a jewelry clasp, in which the fastening parts each have two barbs and two holding devices, ensures a particularly effective and secure closure. 
     In addition, the use of two barbs and two holding devices permits a delicate and visually attractive design of the fastening parts. In addition, due to the delicate design of the fastening parts, this saves on material, so that inexpensive production of the fastening parts according to the invention is possible. 
     In another preferred specific embodiment of the invention, the permanent magnets are situated in the interior of the fastening parts. The permanent magnets are also advantageously designed to be cylindrical and have diameters which correspond to the inside diameters of the housings of the fastening parts. In the sense of the present invention, the term “correspond” means that the permanent magnets can be inserted into the cylindrical housing of the fastening parts without forming a visually perceptible distance from the interior side of the housing and without permitting any play in the permanent magnet or wobbling. The permanent magnets are advantageously accommodated by the lower area of the fastening parts and protrude into the upper area of the fastening parts. 
     In another preferred embodiment of the invention, the permanent magnets are of different lengths. One of the two permanent magnets advantageously has a length which preferably amounts to 50% to 70%, especially preferably 55% to 65% and most preferably 58% to 62% of the total height of the fastening part, measured from the lower base plate of the fastening part. This permanent magnet advantageously protrudes preferably 20% to 40%, especially preferably 25% to 35% and most preferably 28% to 32% into the upper area of the fastening part. It is additionally preferred for the permanent magnet of the other fastening part to have a height which preferably amounts to 70% to 95%, especially preferably 75% to 90% and most preferably 80% to 85% of the total height of the fastening part. This second permanent magnet preferably protrudes 60% to 80%, especially preferably 65% to 75% and most especially 68% to 72% into the upper area of the fastening part. It is preferable for the sum of the lengths of the permanent magnets protruding into the upper part of the fastening parts to correspond together to the height of the upper area of the fastening part. The different lengths of the permanent magnets are illustrated in a particularly illustrative manner in  FIGS. 3 to 5  of the present patent application. The aforementioned dimensions advantageously produce the surprisingly effective interaction of the mechanical and magnetic closing effect of the jewelry clasp according to the invention, which goes beyond the sum of the individual effects. 
     In another preferred specific embodiment of the invention, the permanent magnets are made of neodymium. Neodymium is one of the metals of the rare earths and is advantageously used for particularly strong magnets. It may also be preferable to use a neodymium-iron-boron compound for production of the permanent magnets. Neodymium advantageously has a permanent magnetic behavior with a susceptibility χ of 3.6×10 −3 . Neodymium magnets are surrounded by an especially strong magnetic field which permits a secure magnetic fastening of the jewelry clasp according to the invention. When combined with other materials, these magnets constitute an inexpensive opportunity to create a large magnetic force at a reasonable price. 
     In another preferred embodiment, one fastening part has a larger inside diameter than the other fastening part. The different sized inside diameters of the two fastening parts together with the curved design of the opening of the two fastening parts advantageously make it possible for the barbs of one fastening part to fit precisely into the holding devices of the other fastening part. In the sense of this invention, the curved design of the opening of the two fastening parts is also referred to as a “screw-like structure.” Due to this screw-like structure of the fastening parts, the angle of rotation at which the openings in the two fastening parts encounter one another advantageously does not play a role. The magnetic force and the design of the opening ensure that the barbs and holding devices will always be in the preferred closing positions. 
     It has been found that fastening parts in the stated height range ensure a particularly good handling. On the one hand, the fastening parts according to the invention can be gripped easily and brought into contact with one another. On the other hand, they produce a high-quality, visually pleasing, delicate impression in the user and the observer, which in particular does not give a clumsy impression. 
     In another preferred embodiment of the invention, the height of the fastening parts is in the range of preferably 9 to 11 mm, especially preferably 9.95 to 10.05 mm, most preferably 10 mm, and the fastening parts preferably have an outside diameter of 4 to 8 mm, especially preferably 5 to 7 mm, most preferably 6 mm, and the fastening part preferably has an inside diameter of 4 to 4.5 mm, most preferably of 4.2 mm, and the fastening part preferably has an inside diameter of 3.8 to 4.1 mm, most preferably of 4.0 mm. It has proven advantageous to design the fastening parts with inside diameters and outside diameters within the aforementioned ranges because this permits a particularly simple and secure joining of the fastening parts. This simplifies handling of the jewelry clasp according to the invention and prevents unwanted entanglement and blocking of the fastening parts. It has advantageously been found that, when using outside diameters in the range of 5 to 7 mm, a surprisingly low-friction engagement of the fastening parts is made possible. In addition to the advantageous effects mentioned above, a preferred outside diameter of 6 mm results in a particularly easy connection to a sheathing of the fastening parts being made available, and this sheathing can be secured on the fastening parts in a particularly effective manner. 
     It has been found that fastening parts in the preferred height range ensure a particularly good handling. On the one hand, the fastening parts according to the invention can be gripped well and can be brought into contact with one another. On the other hand, fastening parts give a delicate, visually attractive and high-quality impression to the user and observer, and this impression does not make them appear to be chunky and bulky in particular. 
     It has also been found that fastening parts with a preferred height of 9 to 11 mm can be manufactured especially easily and inexpensively because these dimensions correspond especially well to those of standardized milling machines and casting devices. A preferred height of the fastening parts of 9.95 to 10.05 mm is advantageous in particular when a particularly delicate and visually slender appearance of the jewelry clasp is to be achieved. Tests have shown in this regard that at a preferred height of the fastening parts, such a ratio relative to the outside diameter of the fastening parts is achieved that it gives a visually pleasant positive impression in most observers. A preferred height of the fastening parts of 10 mm corresponds surprisingly well—both visually and technically—to the usual dimensions and standards in the technical field of jewelry production, so that such fastening parts can be connected to the connecting ends of the pieces of jewelry in a particularly simple and visually attractive manner. For example, the fastener device according to the aforementioned embodiment of the invention may also be used to join different elements of clothing items to one another. Bikini tops or halter neck tops might be one example. 
     In another preferred embodiment of the invention, the height of the fastening parts is in the range of preferably 4 to 6 mm, especially preferably 4.5 to 5.5 mm, most preferably 5 mm, and the fastening parts preferably have an outside diameter of 2 to 4 mm, especially preferably 2.5 to 3.5 mm, most preferably 3 mm, and the fastening part preferably has an inside diameter of 2 to 2.25 mm, most preferably 2.1 mm and the fastening part preferably has an inside diameter of 1.9 to 2.05 mm, most preferably 2.0 mm. These dimensions advantageously and preferably each correspond to 50% of the values already cited in the preceding embodiment with regard to the height and inside diameter and outside diameter. The advantages mentioned above with regard to the individual dimension ranges thus also apply similarly to the 50% reduced values. The reduced embodiment may be particularly easy to use for children&#39;s pieces of jewelry in which opening of the jewelry clasp is particularly undesirable because it could result in the jewelry being swallowed, for example. In addition, pieces of jewelry for children are often designed to be particularly small, which is also true of the fasteners for them so that they are suitable for small children&#39;s hands. Material is advantageously saved through this design of the jewelry clasp, so that resources are conserved and manufacturing costs are reduced. This embodiment is therefore particularly advantageous for jewelry clasps made of high-quality and expensive materials. 
     In another embodiment of the invention, the height of the fastening parts is preferably in the range of 10 to 30 mm, especially preferably 15 to 25 mm, most preferably 20 mm, and the fastening parts preferably have an outside diameter of 5 to 15 mm, especially preferably 6 to 13 mm, most preferably 12 mm preferably has an inside diameter of 5 to 10 mm, most preferably 8.4 mm, and the fastening part preferably has an inside diameter of 6 to 10 mm, most preferably of 8 mm. It has been found that the aforementioned dimensions are especially suitable for providing a fastener device for industrial applications in particular, for example, for mountain climber cables, dog leashes and/or cable couplings, but this list should show only possible applications and is not intended to be definitive. For example, carabiner hook-and-screw connections, which are subject to the disadvantages and shortcomings described in the description of the prior art, could advantageously be replaced by fastener devices according to the invention. The fastener device according to the invention thus facilitates the joining of different cables or cords and ensures a particularly secure connection. For example, the fastener device may also be used to join components of clothing items to one another. 
     There is a need for reliable closing of jewelry clasps, so that the jewelry is not lost. On the other hand, there is an expectation on the part of consumers that a piece of jewelry should be easy to open and close, i.e., it should be easy to handle. These two requirements are contradictory to a certain extent because known jewelry clasps that are easy to open and/or those that are known from the prior art do not generally ensure a secure fastening, and furthermore, secure fastening mechanisms are typically difficult to handle. The present invention surprisingly overcomes this presumed contradiction and thus constitutes a departure from the prior art. 
     In another preferred embodiment of the invention, the barbs of a fastening part protrude further into the holding devices of the corresponding fastening part when there is a pull along the imaginary axis of opening and closing which runs centrally in the fastening parts. When there is a sudden strong and abrupt pull on the two fastening parts along the imaginary axis of opening and closing, the adhesive connection of the two permanent magnets in the interior of the fastening parts may be released. The barb of one fastening part is advantageously secured by the holding device on the other fastening part. 
     The fastening effect of the jewelry clasp according to the invention is advantageously based on two supplementary principles: the barbs and holding devices ensure a mechanical closure of the jewelry clasp while the two permanent magnets in the interior of the fastening parts make a magnetic contribution toward a secure fastening of the jewelry clasp. If the two fastener components are eliminated, for example, due to a sudden pull, then one of the two components of the closing mechanism alone can also ensure an effective fastening of the jewelry clasp. The jewelry clasp according to the invention is thus a particularly efficient safety mechanism against inadvertent opening of the jewelry clasp with a sudden pull. When the pull is released, i.e., when the magnetic force between the two permanent magnets is greater than the tensile force pulling the two fastening parts apart from one another, the two fastening parts are pulled back together again by the magnetic force until they are in the original closing position in a form-fitting manner. It was completely surprising that the sliding surfaces in particular which are preferably formed by the flat regions between the holding device and the transitional area between the first area and the second area of the fastening part, this attraction is supported in a particularly effective manner. Use tests have shown that the design of the sliding surfaces makes a significant contribution to the synergistic cooperation of the mechanical closing effect with the magnetic closing effect of the jewelry clasp, wherein the overall fastening effect goes surprisingly beyond the fastening effect of a strict aggregation of closing effects. In addition, the presence of the sliding surface preferably leads to a fastener that is particularly easy to handle and can be operated especially well with one hand in particular. 
     The unexpectedly effective cooperation of the mechanical components with the magnetic components of the jewelry clasp according to the invention is manifested in particular when applying an axial pull in the direction of the imaginary axis of opening and closing. The overall closing effect of the mechanical effects and the magnetic closing effects then does not in particular amount to a strict aggregation of the known individual effects but instead has a synergistic effect in particular which is manifested in that the fastening parts of the jewelry clasp according to the invention can withstand greater loads than the usual jewelry clasps and fastener devices whereas these loads are greater in particular than the sum of the load that can be withstood by a jewelry clasp which is based only on mechanics or only on magnetism. The present patent application advantageously does not maximize exclusively the fastener effect of the jewelry clasp but instead optimizes its overall functionality to the extent that a surprisingly good balance is assured between a secure fastening on the one hand and a fastener that is easy to handle on the other hand. 
     In another preferred embodiment of the invention, the jewelry clasp is opened and closed by rotating the two fastening parts in opposite directions from one another. To close the jewelry clasp, a barb of a fastening part is advantageously inserted first into one of the two openings in the corresponding fastening part. The barb of the one fastening part is advantageously moved by the magnetic force along the inside wall of the opening and into one of the holding devices of the corresponding fastening part due to the curved screw-like or thread-like design of the opening of the fastening parts. 
     Due to the curved design of the opening of the fastening parts, the two fastening parts are rotated one into the other until the two permanent magnets are in form-fitting contact in the interior of the fastener. At the end of the rotating process, both the mechanical component and the magnetic component are contributing toward an unexpectedly secure fastening of the jewelry clasp which is the result of the synergistic interaction of the different closing effects. It is preferable for the two fastening parts to move in opposite directions in the rotating operation. The magnetic attraction of the two permanent magnets preferably results in the barbs sliding around the sliding surfaces, which preferably form an angle α of greater than or equal to 25° with the imaginary axis of opening and closing, in particular in a frictionless manner and without any entanglement or clamping into the holding devices of the corresponding fastening part. 
     It is additionally preferred for the first areas of the fastening parts to each have six to ten bulges, preferably eight wedge-shaped bulges, such that half of the bulges are present on the inside of the housing wall of the fastening parts and the other half are in the same location on the housing wall on the outside of the fastening parts. These wedge-shaped bulges are illustrated in  FIG. 4 . In the context of this patent application, a wedge is a three-dimensional structure having a rectangular base area formed by two parallel longitudinal sides and wide sides and having a height that changes over the length of the wedge. The increase in height runs in a linear and steady pattern from the lowest height, which is usually h=0 mm, to the maximum height. These wedge-shaped bulges facilitate the fixation of the permanent magnet when they are mounted on the inside of the housing wall, and thereby increase the stability of the fastening parts when they are mounted on the outside of the housing wall. It was completely surprising that the handling of the fastening parts of the jewelry clasp according to the invention can be greatly facilitated by providing wedge-shaped recesses. 
     In another preferred embodiment, the wedge-shaped bulges are distributed regularly over the circumference of the housing wall of the fastening parts. When four bulges, for example, are provided on the inside or outside of the housing wall, these four bulges each have an angle spacing of 90°. The average person skilled in the art will recognize that the angular distance beta can preferably be determined by the following equation with a number n of n wedge-shaped bulges: 
       beta=360°/ n.  
 
     Due to the regular distribution of the wedge-shaped bulges on the circumference of the housing wall of the first areas of the fastening parts, a visually attractive and especially harmonious impression of the fastening parts is surprisingly achieved. The average person skilled in the art knows that the angle or distances determined in this way are average values, but the actual distances may deviate from the calculated average, for example, due to deviations in production. Of course jewelry clasps having such deviating values still fall within the scope of protection of the present invention. 
     It is additionally preferable for the wedge-shaped bulges to have a length in the range of 2.2 to 2.6 cm, preferably a length of 2.4 cm. When the wedge-shaped bulges have a length in the range of 2.2 to 2.6 cm preferably a length of 2.4 cm, it is advantageously possible to arrange them in the position of the first areas on the inside and outside of the fastening parts, among others, on which the housing wall has the least height. 
     It is additionally preferable for the wedge-shaped bulges to taper from the top to the bottom. In the context of the present patent application, the term “bottom” refers to the direction in space in which the rear side of the fastening part is arranged. However, the term “top” describes the direction in space in which the second areas of the fastening part, comprising the barbs of the fastening part, among other things, are arranged. Thus the wedge-shaped bulges have their maximum height in the area of the rear side of the fastening parts and on their opposite ends. 
     In other preferred specific embodiment, the invention relates to a jewelry clasp with wedge-shaped bulges on fastening part A having a maximum height in the range of 0.19 to 0.21 mm, preferably a height of 0.2 mm. It is further preferred that the wedge-shaped bulges on fastening part B arranged on the inside of the housing wall of fastening part B have a maximum height in the range of 0.09 to 0.11 mm, preferably a height of 0.1 mm, and the wedge-shaped bulges on fastening part B arranged on the outside of the housing wall of the fastening part B, have a maximum height in the range of 0.19 to 0.21 mm, preferably a height of 0.2 mm. Tests have shown that the wedge-shaped bulges having the aforementioned dimensions ensure an improved handling in comparison with the jewelry clasps known from the prior art, in particular for the case when a piece of jewelry having a jewelry clasp according to the invention is to be closed reliably with just one hand, for example, because the bulges offer an improved resistance and point of attack. This is also true with the use of the fastener device according to the invention for connecting cables, for example, in climbing or mountain climbing, where one must often use only one hand for joining cable ends and support in bringing together the cable ends through the attractive force of the permanent magnets offers an excellent advantage. 
     In another preferred specific embodiment of the invention, the fastening parts comprise refined zinc alloys, stainless steel, aluminum, silver, gold, ceramic material, titanium, ABS plastic, glass fiber-reinforced plastic and/or carbon fibers. It is preferable for the fastening parts to be made of nonmagnetic materials so that there is no super-positioning of different magnetic fields that might have a negative effect on the fastening effect of the permanent magnets. 
     The term “refined zinc alloy” in the sense of the present invention preferably refers to zinc alloys that have been standardized with regard to their composition and may contain copper and/or aluminum as additional alloy ingredients. Refined zinc alloys can be processed advantageously and more easily than pure zinc and are also available at a lower cost. Refined zinc alloys are preferably processed by zinc die casting, which preferably refers to a die casting processing. Therefore, large quantities of fastening parts according to the invention can be manufactured advantageously under inexpensive conditions. The fastening parts manufactured in this way are characterized by a high dimensional stability, have very good mechanical values and are very suitable for a surface treatment such as nickel plating or chrome plating. Because of their properties, refined zinc alloys are tolerated especially well and usually do not lead to allergic reactions, as tests have shown. Fastening parts produced from refined zinc alloys may therefore advantageously also be used in particular for producing jewelry clasps for children or for people with a tendency to skin reactions. 
     Stainless steel is characterized by a particularly high degree of purity with regard to the alloy additives used and usually does not have any visual impairment due to rust or corrosion. Fastening parts produced from aluminum are advantageously especially lightweight and give a visually attractive impression to the user. Titanium is a transition metal characterized by a high corrosion resistance, good strength and a low weight. It advantageously has a silvery metallic appearance. Ceramic materials and plastics advantageously do not cause any allergies and are an inexpensive, low-weight alternative to the materials mentioned above. 
     ABS plastics (acrylonitrile-butadiene-styrene) are preferably thermoplastics, which are very suitable for being coated with metals (galvanization) and polymers. In particular galvanizing, painting and printing of fastening parts produced from ABS plastic are made possible in especially simple ways. In addition, it has been found that fastening parts made of ABS plastic can advantageously also be produced by using 3D printing methods. 
     The term “glass fiber-reinforced plastic” in the sense of the present invention preferably denotes a fiber-plastic composite consisting of a plastic and glass fibers. It is preferable to use thermosetting plastics such as polyester resin or epoxy resin as the base as well as thermoplastic polymers such as polyamide [nylon]. Glass fiber-reinforced plastics advantageously form an inexpensive but nevertheless very high quality fiber-plastic composite which can also be used, for example, in applications that are subject to high mechanical stresses. In comparison with fiber-plastic composites made of other reinforcing fibers, glass-fiber-reinforced plastic preferably has a relatively low modulus of elasticity, even lower than that of aluminum, for example. A high elongation at break and elastic energy uptake are advantageously achieved due to the glass fiber reinforcement. Tests have shown that glass fiber-reinforced plastic also has an excellent corrosion behavior even in an aggressive environment, which is why it is especially suitable for manufacturing fastening parts for pieces of jewelry. In addition, glass fiber-reinforced plastics are characterized by good moldability and a high design freedom in the production of fastening parts. 
     The terms “carbon fiber” and “carbon fiber-reinforced plastic” in the sense of the present invention preferably denote a composite material, in which carbon fibers are embedded in a plastic matrix, usually epoxy resin. The matrix material preferably serves to bond the fibers and to fill the interspaces. The matrix of carbon advantageously improves the mechanical properties of the material, in particular the tensile strength and stiffness. An important advantage when using carbon fibers is the low density of the material in comparison with metal so that especially lightweight fastening parts can be obtained when they are produced from carbon fibers. 
     When gold is used as the starting material for production of the fastening parts, it is preferable to use gold with a degree of purity of less than 14 karat. This preferably corresponds to an amount of 585 parts by weight gold in a total amount of 1000 parts by weight. Especially high-quality and high-priced fastening parts are obtained by using gold. 
     In another preferred specific embodiment of the invention, the fastening parts are produced by milling, by CNC milling, by the injection molding process and/or by the die-casting method. 
     The term “milling” in the sense of the present invention preferably denotes the machining of metals, wood or plastics in such a way that they are cut by means of a milling tool. This is preferably performed on special machine tools, whereby in the context of the present invention, the term preferably denotes manually or mechanically controlled milling, which is preferably also referred to as conventional milling. It is preferable that the rate of advance in conventional milling is optionally regulated with cranks or simple machine-feed systems. However, the term CNC milling denotes computer-controlled milling, in which the milling machine can be programmed by means of a machine control. The CNC technique advantageously enables 3D milling, with which complex 3D contours can be created. 
     The term “injection molding method” in the sense of the present invention preferably denotes to a casting method, which is used mainly in processing plastics. It is preferable for the respective material to be liquefied, i.e., plasticized, in an injection molding machine and then injected under pressure into a mold, which is the injection mold. In the mold, the material is converted back to the solid state, preferably by cooling or by a crosslinking reaction, and then is removed as a finished part after opening the mold. The cavity of the mold advantageously determines the shape and surface structure of the finished part. It has been found that directly usable molded parts can be produced inexpensively in large numbers with this method. In addition, injection molding permits almost free choice of shape and surface structure such as, for example, smooth surfaces, a grain for areas, patterns, engravings, etc., that are pleasant to touch, and color effects. 
     The term “die casting” describes an industrial casting method for serial or mass production of construction parts. It is especially suitable for metallic materials with a low melting point such as, for example, alloys of aluminum, zinc, silicon and/or magnesium. It is preferable for the liquid melt to be forced under a high pressure of approx. 10 to 200 MPa and at a very high mold filling rate of up to 12 m/s into a die-casting mold, which is preferably also referred to as a casting mold or cavity in the sense of the present invention, where it preferably solidifies in die casting. It is advantageous to work without a model and/or permanent mold in the die-casting method, so that the mold need only be manufactured once, which is advantageous in mass production of the same fastening parts. 
     In another preferred specific embodiment, one of the two fastening parts is provided with a sheathing of nonmagnetic stainless steel, aluminum, ceramic material, titanium, plastic and/or a noble metal. It is preferable for the noble metals to be selected from a group consisting of gold, silver, platinum, iridium, palladium, osmium, rhodium, ruthenium and/or a combination of these noble metals. This sheathing is advantageously provided with a product identification or brand name identification. The sheathing of noble metals or the other materials listed above upgrades the visual appearance of the fastening parts and creates a high-quality attractive visual impression of the jewelry clasp according to the invention. 
     In another preferred specific embodiment of the invention, the sheathing of one of the two fastening parts is affixed by hydraulic pressing. Hydraulic presses operate by the hydrostatic principle in a force-bound process. According to the hydrostatic principle, the pressure in a liquid is constant and a force acting on a wall of a container can thus be multiplied in this way. As a rule, hydraulic presses are used when a very high pressure is acting constantly and uniformly over a relatively great distance for the purpose of compression. Hydraulic presses can advantageously be used in a flexible manner and are easy to retrofit. It is also preferable for the fixation of the permanent magnets in the fastening parts to be accomplished by hydraulic pressing. However, it may also be preferable to implement the fixation of the permanent magnets in the fastening parts by adhesive bonding. These two methods may also be combined with one another to advantage. This ensures a particularly effective fixation of the permanent magnets in the fastening parts. 
     In another aspect, the invention relates to the use of the jewelry clasp as a safety clasp and/or fastening system. It is therefore also preferable to refer to the jewelry clasp according to the invention as a fastening device, wherein the two terms are used synonymously in the context of the present invention. Use of the fastening device as a safety fastener and/or fastening system advantageously relates to industrial applications such as mountain climbing cables, dog leashes and/or cable couplings, but this list should merely show possible fields of application and should not be conclusive. It was completely surprising and in particular was not self-evident that the jewelry clasp according to the invention could also be used in industrial applications. In the past, the average person skilled in the art has assumed that jewelry clasps may be used primarily for accessories and pieces of jewelry, which can be attributed in particular to the shortcomings and disadvantages described in the prior art. Due to the synergistic combination of mechanical and magnetic closing effects and the resulting unexpected overall closing effect of the fastening device according to the invention, this can now also withstand loads such as those not previously assumed in the technical world, namely that these would be too great for conventional jewelry clasps and fastening devices of the aforementioned type. The jewelry clasp according to the invention and/or the inventing fastening device can surprisingly now also be used in novel application areas that could not previously be imagined, where these industrial applications would not have been self-evident for the average person skilled in the art in particular. 
     In another aspect, the invention relates to a bracelet comprising a jewelry clasp according to the invention. In another aspect, the invention relates to a kit comprising at least two bracelets which have a jewelry clasp according to the invention and are joined to one another in such a way as to form a decorative necklace. It has been found that the average diameter of the human arm is in a ratio to the average diameter of the human neck such that a necklace can be formed by joining at least two bracelets to one another and together forming a necklace. Depending on the desired length of the necklace and depending on the preferred method of wearing it, two, three or four bracelets can be combined with one another to form a necklace by means of the jewelry clasps according to the invention. 
     In the sense of the present invention a necklace consists of a group of at least two bracelets wherein it is preferable for the necklace to be at least twice as long as a bracelet. This is the case, for example, when two bracelets are joined together to form one necklace. It may also be preferable for the necklace to be at least three or four times longer than a bracelet. In this case three or four bracelets are advantageously joined to one another to form a necklace. 
     In another aspect the invention relates to a kit comprising at least two bracelets. It is preferable for these two bracelets to be joined to one another by means of the jewelry clasps according to the invention. This yields a necklace that is worn close to the neck. Combining three bracelets yields a necklace that is worn more loosely. It may be preferable to combine similar bracelets to form a necklace but it may equally be preferable to combine different bracelets. When using more than two bracelets it may also be preferable to combine two similar bracelets and one different bracelet or the other way around. Thus there are no limits to the possible variations. 
     It is preferable to provide bracelets in lengths of 8, 20 and 22 cm, for example. To increase the multitude of variations and in particular also to make it possible to assemble long necklaces by combining them, bracelets are also provided in the preferred lengths of 26 and 75 cm, for example. These are made preferably essentially of leather and may be used as wrap-around bracelets. The average person skilled in the art will understand that the term “essentially” in the context of this patent application is to be understood to mean that the bracelets having preferred lengths of 26 and 75 cm are made primarily of leather but may also include smaller amounts of other materials, preferably natural materials. The use of leather and other natural materials has proven to be particularly advantageous when users of the bracelets and necklaces suffer from allergies to metals or metal alloys. 
     It may also be preferable for the kit to comprise at least two bracelets, wherein the at least two bracelets are joined to one another using other types of jewelry clasps. Within one kit, several types of fasteners may advantageously be combined with one another in different positions. 
    
    
     
       The invention will now be described in greater detail on the basis of exemplary embodiment and the following figures, in which: 
         FIG. 1  shows a side view and oblique view of fastening parts A and B according to the invention 
         FIG. 2  shows an enlarged side view of one each of fastening parts A and B according to the invention 
         FIG. 3  shows an exemplary side view of a fastening part A according to the invention with an imaginary axis of opening and closing 
         FIG. 4  shows an example of a side view of a fastening part B according to the invention, also showing the first and second areas 
         FIG. 5  shows additional side views of one fastening part A and B each according to the invention 
         FIG. 6  shows a top view of a fastening part A and B according to the invention 
         FIG. 7  shows a schematic diagram of how bracelets are worn on a human arm 
         FIG. 8  shows a schematic diagram of three bracelets 
         FIG. 9  shows a schematic diagram of how a necklace is worn on a human neck 
         FIG. 10  shows a schematic diagram of a necklace according to the invention, comprised of three bracelets 
         FIG. 11  shows a schematic diagram of a necklace according to the invention, comprised of two bracelets 
     
    
    
       FIG. 1  shows a side view and an oblique view of the fastening parts A and B according to the invention. The top part of  FIG. 1  shows an oblique view of the two fastening parts A and B according to the invention. This shows the permanent magnets ( 10 ) in the interior region//internal area? of a fastening part ( 28 ). The permanent magnets ( 10 ) are affixed in the internal area//interior region? ( 28 ) of the fastening parts (A, B) by means of hydraulic pressing or adhesive bonding. The fastening parts (A, B) consist of a housing ( 12 ), the rear side ( 16 ) of which faces the piece of jewelry. The housing ( 12 ) is divided into a first area ( 18 ) and a second area ( 20 ), the first area ( 18 ) being the lower area of the cylindrical housing ( 12 ). The second area or upper area ( 20 ) of the fastening part (A or B) is designed to be open ( 14 ) and is formed by barbs ( 22 ) and holding devices ( 24 ). These barbs ( 22 ) and holding devices ( 24 ) are designed to be complementary to another and thus cooperate with one another in such a way that they ensure a secure fastening of the jewelry clasps. 
       FIG. 1  shows clearly that the permanent magnets ( 10 ) of the fastening parts (A, B) have different lengths. The permanent magnet ( 10 ) of the fastening part (A) is designed to be longer than the permanent magnet ( 10 ) of the fastening part (B) and it protrudes further into the second area ( 20 ) of the fastening part (A). 
       FIG. 1  additionally shows the curved shape of the intermediate space between the barbs ( 22 ) of the fastening parts (A, B). This curved shape of the interspaces facilitates closing of the jewelry clasps according to the invention due to the fact that when bringing the two fastening parts (A, B) into contact, the barbs ( 22 ) of the one fastening part (A) entered the interspaces situated between the barbs of the fastening part (B) and are guided along the curved shape of the intermediate space into the holding device ( 24 ) of the fastening part (B). The attractive magnetic force between the two permanent magnets ( 10 ) of the two fastening parts (A, B) plays a supporting role here. 
     Due to the combination of the mechanical design of the upper area of the housing of the fastening parts (A, B) with the use of magnetic force between the two permanent magnets ( 10 ) of the two fastening parts (A, B), a secure fastening of the jewelry clasps is ensured. In particular it is possible to close the jewelry clasps by said combination using just one hand. 
       FIG. 2  shows an enlarged side view of one each of the fastening parts (A and B) according to the invention.  FIG. 2  shows clearly the difference in length of the permanent magnets ( 10 ). The permanent magnets ( 10 ) are situated in the internal area ( 28 ) of the respective fastening part. The fastening part (A or B) is formed by a housing ( 12 ) which is itself formed by a rear side ( 16 ) and an exterior wall ( 26 ) in the lower area ( 18 ). The housing ( 12 ) is designed to be cylindrical or sleeve-shaped in the lower area ( 18 ). Fastening mechanisms may be provided on the rear side ( 16 ), with which attachment of the jewelry clasp to a piece of jewelry can be implemented. The upper area ( 20 ) of the fastening part (A or B) is formed by barbs ( 22 ) and holding devices ( 24 ). This shows that the holding devices ( 24 ) represent a recess on the lower side of the barb ( 22 ). There is an opening ( 14 ) in the fastening parts (A, B) between the barbs. 
       FIG. 3  shows an example of a side view of a fastening part (A or B) according to the invention with an imaginary axis ( 30 ) of opening and closing. This imaginary axis ( 30 ) of opening and closing of the fastening parts (A or B) runs centrally, i.e., in the middle through the lower area ( 18 ) of the fastening part, which is designed to be cylindrical and continues in a straight line in the upper area ( 20 ) of the fastening part (A or B). The imaginary axis ( 30 ) of opening and closing thus starts at the midpoint of the circular rear side ( 16 ) of the housing ( 12 ) of the fastening part (A or B) and then leads upward at a right angle to said rear side ( 16 ). The imaginary axis ( 30 ) of opening and closing thus forms an imaginary midline for both the housing ( 12 ) of the fastening part and for the permanent magnets ( 10 ). 
     The adhesive bond formed in the closing position between the two permanent magnets ( 10 ) in the interior ( 28 ) of the housing ( 12 ) is released when there is a sufficiently strong pull (mainly suddenly or with a jerk) on the two fastening parts (A, B) along the imaginary axis ( 30 ) of opening and closing. Despite this release of the bond based on magnetic force, the barbs ( 22 ) of the one fastening parts (A or B) remain in the holding devices ( 24 ) of the other fastening part (B or A) respectively. When the pull subsides, the permanent magnets ( 10 ) are pulled toward one another again, and the jewelry clasps again assume the original completely closed position, in which the permanent magnets ( 10 ) are in form-fitting contact with one another. 
     In addition,  FIG. 3  shows a sliding surface ( 52 ) which forms an angle α ( 54 ) with the imaginary axis ( 30 ) of opening and closing. This angle α ( 54 ) may be imagined as being formed in particular when a straight line ( 56 ) is drawn in the plane spanned by the sliding surface ( 52 ). All the points on this straight line ( 56 ) lie in the plane of the sliding surface ( 52 ). The angle α ( 54 ) is preferably greater than or equal to 25°. 
     As an example  FIG. 3  shows a fastening part (A) which can be seen by the fact that the permanent magnet ( 10 ) of the fastening part (A) shown here protrudes into the area of the barbs ( 22 ). The permanent magnet ( 10 ) of the fastening part (A) therefore protrudes further into the second part ( 20 ) of the fastening part (A). 
       FIG. 4  shows an example of a side view of a fastening part (B) according to the invention with the diagram of the first area ( 18 ) and the second area ( 20 ).  FIG. 4  shows a fastening part (B), which can be recognized by the fact that the permanent magnet ( 10 ) takes up only approximately one-third of the total length of the second area ( 20 ) of the fastening part (B). 
     The first area ( 18 ) of the fastening part (B) extends from the rear side ( 16 ) of the housing ( 12 ) of the fastening part (B) up to the location where the completely closed exterior wall ( 26 ) of the housing ( 12 ) ends and an intermediate space begins between the barbs ( 22 ) of the second area ( 20 ) of the fastening part (B), by definition, the transition between the first area ( 18 ) and the second area ( 20 ) of the fastening part (B) is marked with a dotted line in  FIG. 4 . 
     In addition,  FIG. 4  shows one possible position for a wedge-shaped bulge ( 50 ) on the outside of the housing wall ( 12 ,  26 ) of the first area ( 18 ) of a fastening part (A, B). The rectangular base area of the wedge-shaped bulge ( 50 ), which is bordered by two parallel longitudinal sides and two parallel broad sides can be seen in the top view. The height of the wedge ( 50 ), which increases from the bottom to the top, extends in the third direction in space, which is not shown here. This means that the height of the wedge ( 50 ) assumes its smallest value in the area of the rear side ( 16 ) of the fastening part, whereas the height of the wedge ( 50 ) assumes its maximum value on the opposite side of the wedge-shaped bulge ( 50 ). The wedge-shaped bulge ( 50 ) tapers from top to bottom. 
     This does not show that the wedge-shaped bulges ( 50 ) are arranged uniformly or regularly over the circumference of the outside and inside walls of the housing ( 12 ) of the first area ( 18 ) of the fastening part (A, B). A uniform or regular arrangement of the wedge-shaped bulges ( 50 ) means in particular that the angular distances between the wedge-shaped bulges ( 50 ) are constant. For example, in the presence of four bulges on the inside or outside of the housing ( 12 ), the angular distance is 360°/4=90°. In general, the angular distance β (beta) in degrees is between n individual wedge-shaped bulges according to the formula 360°/n=beta. 
       FIG. 5  shows another side view of one each of the fastening parts (A or B) according to the invention. In comparison with  FIG. 2 , the fastening parts (A, B) are rotated by an angle α here.  FIG. 5  shows clearly that the permanent magnet ( 10 ) of the fastening part (B) is designed to be shorter than the permanent magnet ( 10 ) of the fastening part (A).  FIG. 5  also shows that the permanent magnet ( 10 ) is situated in the interior ( 28 ) of the fastening parts (A, B) and that their diameters ( 34 ,  36 ) correspond to the inside diameters of the housings ( 12 ) of the fastening parts (A, B). The housings ( 12 ) are formed by an outside wall ( 26 ) and the rear side ( 16 ) and are designed to be cylindrical or sleeve-shaped. The rear side ( 16 ) has a circular base area. For visual reasons, the housing ( 12 ) may be provided with a sheathing ( 32 ). This sheathing ( 32 ) may consist of nonmagnetic stainless steel, aluminum, ceramic material, titanium, plastic and/or noble metals. 
     In addition,  FIG. 5  also shows the barbs ( 22 ) and the holding devices ( 24 ) of the fastening parts (A, B).  FIG. 5  also shows the opening ( 14 ) in the upper area ( 20 ) of the fastening part. The barbs ( 22 ) of the one fastening part (A or B) are inserted into these openings ( 14 ) in the interspaces between the barbs ( 22 ) of the respective other fastening part (B or A). the jewelry clasp according to the invention is closed in a closing position ( 48 ) because of the magnetic force between the two permanent magnets ( 10 ) and the curved design of the transitional area between the first area ( 18 ) and the second area ( 20 ) of the fastening part (A, B), along the exterior wall of which the barb ( 22 ) of the one fastening part (A or B) is guided to the holding device ( 24 ) of the other fastening part (B or A). 
       FIG. 6  sows the top view of the two fastening parts (A and B). The inside diameter ( 36 ) of the opening ( 14 ) of the fastening part (B) is smaller than the inside diameter ( 34 ) of the opening ( 14 ) of the fastening part (A). Due to the screw-like structure of the upper area ( 20 ) of the fastening parts (A, B) the fastening parts (A, B) always fit together accurately. The thread-like structure created in the two openings ( 14 ) results in the two fastening parts (A, B) being able to be screwed together until the two permanent magnets ( 10 ) come into form-fitting contact in the interior ( 28 ) of the jewelry clasp. 
       FIG. 7  shows a schematic diagram of how the bracelets ( 42   a, b, c ) according to the invention are worn on a human arm ( 38 ). This shows a human arm ( 38 ) with a hand ( 40 ). The bracelets ( 42   a, b, c ) shown here are worn in the area of the forearm or the wrist. Similar bracelets or different bracelets may be worn together. It is also possible for two of the three bracelets to be identical. Of course it is equally possible to wear one, two or several bracelets at the same time. The position of the bracelets is indicated only schematically in  FIG. 7  and in practice may deviate from the diagram shown here. 
       FIG. 8  shows a schematic diagram of three bracelets ( 42   a, b, c ). In this schematic diagram, the round dots at the ends of the bracelets ( 42   a, b, c ) correspond to the fastening parts (A. B) of the jewelry clasp according to the invention. This shows bracelets in an open position, i.e., the fastening parts (A, B) are not in the closed position but instead are not in contact with one another at all and are separate from one another. 
       FIG. 9  shows a schematic diagram of how a necklace ( 44 ) is worn on a human neck ( 46 ). This shows how a necklace ( 44 ) is formed by connecting three bracelets ( 42   a, b, c ). For example, one fastening part (A) of a bracelet ( 42   a ) is connected to a fastening part (B) of another bracelet ( 42   b ). Unlike the situation in establishing a closing position of a bracelet ( 42 ), in which the fastening part (A, B) of a bracelet ( 42 ) are brought together into a closing position, in the case when a necklace ( 44 ) is to be formed from two or more bracelets, corresponding fastening part (A, B) of different bracelets ( 42 ) are brought into contact with one another and brought to a closing position. Depending on how many bracelets ( 42 ) are to be combined with one another to form a necklace ( 44 ), the length of the necklace ( 44 ) is approximately two, three or four times as long as the bracelet ( 42 ), etc. 
     A kit comprised of at least two bracelets joined together to form a necklace ( 44 ) may thus comprise bracelets ( 42 ) having a jewelry clasp according to the invention as well as bracelets having a different type of fastener mechanism as long as the bracelets can be joined together in the manner described here. 
       FIG. 10  shows a schematic diagram of a necklace ( 44 ) according to the invention comprises of three bracelets ( 42   a, b, c ). The black dots in  FIG. 10  represent the fastening parts (A, B) of a bracelet ( 42 ). This shows that one fastening part (A) of a bracelet ( 42 ) cooperates with a corresponding fastening part (B) of another bracelet ( 42 ) to form a complete closed jewelry clasp. The diagram of three bracelets ( 42   a, b, c ) is shown as an example. It is also possible to combine two, three, four or more bracelets ( 42 ) together to form a necklace ( 42 ). When a necklace ( 44 ) is formed by combining three bracelets ( 42 ) the result is a necklace ( 44 ) whose length is approximately three times greater than the length of a single bracelet ( 42 ). 
       FIG. 11  shows a schematic diagram of a necklace ( 44 ) according to the invention, comprised of two bracelets ( 42 ). The black dots correspond to the fastening parts (A, B), which are in an unconnected, not closed position in  FIG. 11 . When a necklace ( 44 ) comprised of two bracelets ( 42 ) is formed by combining two bracelets ( 42 ), the result is a necklace ( 44 ) approximately twice as long as single bracelet ( 42 ). In the arrangement illustrated in  FIG. 11 , one fastening part (A) of a bracelet (A or B) cooperates with a corresponding fastening part (B) on the other bracelet (B or A). The jewelry clasp according to the invention here is used not only for the fastening of the necklace ( 44 ) but also serves to join the components of the necklace ( 44 ), namely the at least two bracelets ( 42 ). The necklace ( 44 ) formed by combining two bracelets ( 42 ) is advantageously worn on the neck with a close fit. 
     LIST OF REFERENCE NUMERALS 
     
         
         A Fastening part 
         B Fastening part 
           10  Permanent magnets 
           12  Housing 
           14  Opening 
           16  Rear side 
           18  First area of a fastening part 
           20  Second area of a fastening part 
           22  Barb 
           24  Holding device 
           26  Exterior wall 
           28  Interior area of a fastening part 
           30  Imaginary axis of opening and closing of the fastening parts 
           32  Sheathing 
           34  Inside diameter of fastening part A 
           36  Inside diameter of fastening part B 
           38  Human arm 
           40  Human hand 
           42  Bracelet 
           42   a, b, c  Bracelets 
           44  Necklace 
           46  Human neck 
           48  Jewelry clasp in a closing position 
           50  Wedge-shaped bulges 
           52  Sliding surfaces 
           54  Angle α 
           56  Straight line in the plane of the sliding surface