Magnetic fastener means

Abstract: A fastener means for fastening first and second elements for example a handbag and a flap for closure of the same has an attraction means attached to the first element and a means to be attracted attached to the second element. The attraction means is a permanent magnet (1) having a through hole between the opposite end surfaces thereof. The permanent magnet (1) has a first pole of first magnetic polarity adjacent one of the end surfaces which is oriented to extend away from the first element when the attraction means is attached thereto, and a second pole of opposite magnetic polarity adjacent the other end surface. The means to be attracted is a ferromagnetic member (3) which is detachably attracted to the first end surface. The angle formed by the end surface adjacent the first end surface and a peripheral side face of the magnet extending between the end surfaces is 95° or larger.

Description: The present invention relates to fastener means. Fastener means which operate by magnetic attraction have been known for a long time and are used in particular as handbag or luggage clasps. A typical example of such a magnetic closure is disclosed in Japanese Utility Model Publication No: Sho 56-45985. In a typical arrangement there is provided an attraction means attached to a first element, for example the body of the handbag and a means to be attracted attached to a second element, for example the flap of the handbag. The attraction means includes a permanent magnet, so that when the attraction means and means to be attracted are brought into confronting relationship, the magnetic force serves to hold them together, thus fastening the flap to the body of the handbag. However, the magnetic force is not so great that the two elements cannot be readily pulled apart to open the handbag when desired. Typically the permanent magnet has a through hole extending between opposite end surfaces which serve as opposed magnetic pole surfaces, and there are two ferromagnetic plates, that is: plates made of a ferromagnetic material but not themselves consisting of a permanent magnet. One of these plates together with the permanent magnet is covered with a plate-like casing and together effectively forms the attraction means. The other plate serves as the means to be attracted to the fastener means. One or the other of the ferromagnetic plates is provided with a post. When the means to be attracted is brought into facial contact with the attraction means, the post extends into the through hole and contacts the other ferromagnetic plate. It is possible that each plate could have a half post, the two half posts meeting in the through hole. The permanent magnet is flat and generally disc-like. Invariably, the peripheral side extending between the opposite end surfaces in this form of fastener forms a right angle with each end surface. US-A-4 825 526 discloses a fastener of this kind which also has a yet further ferromagnetic plate overlying the distal pole surface of the permanent magnet and serving as a pole plate. The attraction means is of cylindrical form. The present invention has arisen from our work seeking to obtain in this type of fastener the maximum attraction force between the means to be attracted and the attraction means while at the same time limiting the leakage flux from the permanent magnet. Such leakage flux may destroy magnetically recorded information, for example information on bank and credit cards and subway tickets. US-A-3 372 443 is concerned with a somewhat different construction of fastener in which both the attraction means and the means to be attracted comprise a permanent magnet with a through hole extending between opposite end surfaces which serve as opposed magnetic pole surfaces. Each of the permanent magnets has an armature in the form of a ferromagnetic member attached to its rear surface and including a post extending into the respective through hole. When the two means engage, the two posts contact each other, one post having a stud end and the other having a recess in its end for receiving the stud end. The two permanent magnets are oppositely poled so as to be attracted to each other when the posts interengage. Each permanent magnet plus armature is mounted within a holder shell which is bent both around the proximal outer edge of the armature and the distal outer edge of the magnet. To enable this, these extreme edges are bevelled. We have found that by providing the permanent magnet, in a fastener of the kind having only a single such magnet, with a peripheral surface extending between the two pole surfaces at an angle of 95° or more to the distal pole surface of the permanent magnet there is improved attraction force and significantly reduced leakage flux. We provide, in accordance with the present invention, a fastener means for fastening first and second elements for example a handbag and a flap for closure of the same comprising: an attraction means comprising a permanent magnet and adapted to be attached to said first element; and means adapted to be attracted to said attraction means but not incorporating a permanent magnet, said means to be attracted being adapted to be attached to said second element; said permanent magnet of said attraction means having a through hole extending between opposite end surfaces thereof, a first pole of first magnetic polarity adjacent one said end surface which is oriented to extend in the direction away from said first element when said attraction means is attached thereto, and a second pole of opposite magnetic polarity adjacent the other said end surface, and a peripheral side face extending between said end surfaces, and a ferromagnetic member attached to said other end surface, said attraction means being adapted to be attached to said first element via said ferromagnetic member; and said means to be attracted comprising a ferromagnetic member arranged to be detachably attracted to said first pole; said fastener means being characterised in that one and/or the other of said ferromagnetic members is in the form of a plate having a post adapted for extending into said through hole, such that said ferromagnetic members are abutted against and attracted to each other via said through hole to complete a magnetic circuit from one said pole to the other of said permanent magnet within said through hole, and in that the angle formed by said one end surface and said peripheral side face is 95° or larger. The attraction means preferably has a covering. The covering may be a casing which may attach the second ferromagnetic member to the permanent magnet. Alternatively the covering may be a plating. The invention is hereinafter more particularly described by way of example only with reference to the accompanying drawings in which:- Fig. 1 is an overall perspective view, with parts separated, of a first embodiment of fastener means constructed in accordance with the present invention; Fig. 2 is a sectional view through the two parts of the fastener means of Fig. 1; Fig. 3 is a sectional view showing how the two parts of the fastener means of Fig. 1 are attached to, for example, a handbag and a flap for closure of the same; Fig. 4 and Fig. 5 are sectional views illustrating how magnetic flux may be measured in a comparative embodiment not in accordance with the present invention; Figs. 6 and 7 are corresponding views showing how magnetic flux may be measured in an embodiment according to Figs. 1 and 2; Fig. 8 is a sectional view illustrating an embodiment of apparatus for measuring the said magnetic flux; Fig. 9 is a sectional view of the permanent magnet of a comparative embodiment not in accordance with the present invention; Fig. 10 is a sectional view of the attraction means of the said comparative embodiment 1; Fig. 11 is a sectional view of the said comparative embodiment 1 with the parts interengaged; Fig. 13 is a sectional view of the attraction means of an embodiment in accordance with the present invention; Fig. 14 is a view corresponding to Fig. 11 for the embodiment of fastener incorporating the attraction means of Fig. 13; Fig. 15 shows the permanent magnet of a second embodiment of fastener means in accordance with the present invention; Figs. 16 and 17 are views corresponding to Figs. 13 and 14 for the second embodiment; Fig. 18 is a sectional view of the permanent magnet of a second comparative embodiment; Figs. 19 and 20 are views corresponding to Figs. 10 and 11 for the second comparative embodiment; Figs. 21, 22 and 23 are views corresponding to those of Figs. 18, 19 and 20 for a further embodiment of fastener means in accordance with the present invention; Figs. 24, 25 and 26 are views corresponding to Figs. 21, 22 and 23 for a yet further embodiment of fastener means constructed in accordance with the present invention; Figs. 27, 28 and 29 are views corresponding to Figs. 24, 25 and 26 for a further comparative embodiment not in accordance with the present invention; Figs. 30, 31 and 32 are views corresponding to Figs. 27, 28 and 29 for a further embodiment of fastener means constructed in accordance with the present invention; Figs. 33, 34 and 35 are views corresponding to Figs. 30, 31 and 32 for yet another embodiment of fastener means constructed in accordance with the present invention; Fig. 36 shows a variation in the geometry of the attraction means for an embodiment of fastener means constructed in accordance with the present invention, shown in sectional view; Fig. 37 is a similar sectional view for another variation in the geometry of the attraction means in an embodiment of fastener means in accordance with the present invention; and Figs. 38, 39 and 40 are corresponding sectional views showing three yet further embodiments of attraction means for use in fastener means in accordance with the present invention. Figs. 1 through 3 show a typical embodiment of fastener means according to the present invention: Fig. 1 is a perspective view to show the attraction means A and the attracted means B; Fig. 2 is a sectional view thereof; and Fig. 3 is a sectional view to show how these means are attached. The attraction means A which constitutes the fastener means comprises a disk-like permanent magnet 1 having a through-hole 1a that extends in the direction of the magnetic poles, and a ferromagnetic member 2 attached on one magnetic pole surface b of the magnet 1. The attracted means B comprises a ferromagnetic member 3 which is to be attracted not only to the other magnetic pole surface a where the ferromagnetic member 2 of the means A is not attached but to said ferromagnetic member 2 via the through-hole 1a. In this embodiment, the ferromagnetic member 2 includes a ferromagnetic plate 2a and a ferromagnetic projection 2b while the ferromagnetic member 3 includes a ferromagnetic plate 3a and a ferromagnetic projection 3b. Both the attraction means A and the attracted means B are provided with legs 4 having strips 4b, 4b to allow the members to be attached on the base material D of a handbag, etc. With a base 4a of the leg 4 being attached to the ferromagnetic plate 2a of the ferromagnetic member 2, the portion 2b′ of the projection 2b with a smaller diameter in the through-hole 1a of the magnet is thrusted in the plate 2a and the base 4a and integrally caulked and attached to the permanent magnet 1. The base 4a of the leg 4 is attached to the ferromagnetic plate 3a of the ferromagnetic member 3. The portion 3b′ of the projection 3b with the smaller diameter erected from the ferromagnetic plate 3a is thrusted in the plate 3a and the base 4a and caulked to integrally form the attracted means B. In the fastener means of the above construction, the magnetic pole surface a of the magnet 1 of the attraction means A and the peripheral side face c extending between the magnetic poles form an angle t which is 95° or greater. Although the permanent magnet 1 in this embodiment is not covered with a casing, it is possible to integrally contain the permanent magnet 1 and the ferromagnetic member 2 in a casing to form the attraction means. The magnet 1 and the ferromagnetic member 2 may be bonded with an adhesive; alternatively, the magnet 1 and the ferromagnetic member 2 may be formed integrally by insert molding using plastics. The permanent magnet may be in the form of a disk, a rectangle, or an ellipse. As will be described later, the ferromagnetic projections 2b and 3b provided on the ferromagnetic members 2 and 3 respectively may be such that the ferromagnetic members 2 and 3 will be abutted against and attracted to each other in the through-hole 1a of the magnet 1 of the attraction means A. Either one of them may be omitted, and the height of the projections 2b and 3b may either be identical or different. Further, instead of providing the ferromagnetic projections 2b and 3b separately from the ferromagnetic plates 2a and 3a respectively, they may be formed as an integral projection from the plates 2a and 3a respectively by press molding and the like. As the peripheral side face c of the fastener means having the above construction is wider than the prior art fastener means wherein the angle t formed by the magnetic pole surface a of the magnet 1 and the peripheral side face c is 90°, the magnetic pole surfaces will be separated by a peripheral surface of greater extent. As a result, the magnetic flux on the magnetic pole surface b can be easily contained in the circuit formed by the ferromagnetic plate 2a, the ferromagnetic projections 2b, 3b, ferromagnetic plate 3a and the magnetic pole surface a , enhancing the magnetic attraction between the projections 2b and 3b and reducing the flux leakage from the peripheral side face c . Changes in the magnetic flux distribution attributable to the geometric characteristics of the permanent magnet 1 will now be described based on the actual measurements. First, reference is made to a fastener means wherein the ferromagnetic members 2 and 3 are both provided with projections 2b and 3b respectively. The intensity of magnetic flux was measured using a gaussmeter. As shown in Figs. 4 through 7, the sensor G of the gaussmeter was attached to the magnetic pole surface a of the permanent magnet 1 when the attraction means A was measured separately. When the means B was attracted to the attraction means A, the sensor G of the gaussmeter was abutted against the peripheral side face c of the magnet 1 in such a manner that the sensor G would be placed in parallel with the magnetic pole surface a of the magnet 1. Figs. 4 and 5 show how the prior art lock closure is measured by a gaussmeter, and Figs. 6 and 7 show the method of measuring the present invention fastener means. In the measurements, the galvanomagnetic effect type gaussmeter Model GT 3B (Nippon Denji Sokutei K.K.) with a gallium arsenide sensor was used. The attraction force of the fastener means was measured using the system shown in Fig. 8. As shown in the figure, the attraction means A was attached to the support 5 of the instrument K while the attracted means B was attached to the tip of the tension rod 7 provided on the movable arm 6 of the instrument K. The movable arm 6 was pulled up, and the pulling strength (kg) when the attracted means B was detached from the attraction means A was measured. The instrument K is manufactured by Oba Keiki Seisakusho as the standard cylinder type tension gauge. A sleeve 8 was interposed between the leg strips 4b, 4b of the means A and B. The sleeve 8 was in turn engaged with a screw rod 9 of the fixing screw. The leg strips 4b, 4b were provided with a bore each, through which a pin 10 was inserted into the sleeve 8 to assemble the means A and B for the measurement. Comparative Embodiment 1 The fastener means shown in Figs. 9 through 11 uses a permanent magnet 1 of the attraction means A wherein the angle formed by the magnetic pole surface a and the peripheral side face c is 90°, the diameter of both the magnetic pole surfaces a and b is 19.1 mm, the diameter of the through-hole 1a is 6.2 mm, the plate thickness is 3.2 mm, and the weight is 2.8 g. As shown in Table 2, the intensity of the magnetic flux of the magnet 1 of the Comparative Embodiment 1 was 556 Gauss at P-1 and 308 Gauss at P-2. When the ferromagnetic member 2 was attached, the measurement read 612 Gauss at P-3 and 315 Gauss at P-4, indicating an increase in the leakage flux due to attachment of the ferromagnetic member 2. Measurement at P-5 when the attracted member B was attached was extremely low in the leakage flux or 122 Gauss. The attraction force of the Comparative Embodiment 1 was averaged at 2.28 kg under the condition as shown in Fig. 11. The result of measurement is shown in Table 1. Embodiment 1 The fastener means shown in Figs. 12 through 14 comprises the attraction means A and attracted means B, each having a ferromagnetic projection 2b, 3b respectively. The angle t formed between the magnetic pole surface a and the peripheral side face c of the magnet 1 in the attraction means A is 95°. The diameter of the magnetic pole surface a is 18.7 mm, that of the surface b is 19.2 mm, the plate thickness is 3.2 mm, the diameter of the through-hole 1a is 6.2 mm, and the weight is 2.8 g. Measurements of the leakage flux at P-1, P-2, P-3, P-4 and P-5 of the magnet 1 of the Embodiment 1 alone, of the magnet 1 attached with the ferromagnetic member 2, and of the magnet 1 attached with both the attraction and attracted means A and B are shown respectively in Table 2. The attraction force of the fastener means according to the Embodiment 1 was measured under the condition as shown in Fig. 14. As shown in Table 1, the average attraction force was 2.55 kg. Embodiment 2 The fastener means shown in Figs. 15 through 17 comprises the attraction means A and attracted means B, each having the ferromagnetic projection 2b and 3b respectively. The angle t between the magnetic pole surface a and the peripheral side face c is 130°. The diameter of the surface a is 16 mm, that of the surface b is 21 mm, the plate thickness is 3.2 mm, the diameter of the through-hole 1a is 6.2 mm, and the weight is 2.8 g. Measurements of the leakage flux at P-1, P-2, P-3, P-4 and P-5 of the magnet 1 of the Embodiment 2 alone, of the magnet 1 attached with the ferromagnetic member 2, and of the magnet 1 attached with both the attraction and attracted means A and B respectively are shown in Table 2. The attraction force of the fastener means according to the Embodiment 2 was measured under the condition as shown in Fig. 17. As shown in Table 1, the average attraction force was 2.65 kg. Attraction Force (kg) Measurement Comparative 1 Embodiment Embodiment 1 Embodiment 2 I 2.30 2.60 2.70 II 2.25 2.45 2.55 III 2.25 2.55 2.65 IV 2.30 2.65 2.55 V 2.30 2.50 2.70 Average 2.28 2.55 2.65 Intensity of Magnetic Flux (Gauss) Measurement point Comparative 1 Embodiment Embodiment 1 Embodiment 2 P-1 556 566 581 P-2 308 295 281 P-3 612 630 654 P-4 315 306 280 P-5 122 110 89 The permanent magnets 1 used in the embodiments 1 and 2 and the Comparative Embodiment 1 all weigh 2.8 g, and are magnetized under the same conditions. As is evident from the Table, the attraction force of the Embodiment 1 shows an increase by 11.8% and the Embodiment 2 an increase by 16.2% as compared with the Comparative Embodiment 1. The values of leakage flux on the magnetic pole surface a of the magnet 1 of the Embodiments 1 and 2 at P-1 and P-3 respectively are greater than those of the Comparative Embodiment 1, indicating that an excellent magnetic field suitable for attracting the means B is formed. The values of leakage flux on the peripheral side face c of the magnet 1 at P-2, P-4 and P-5 in the Embodiments 1 and 2 respectively are smaller than those of the Comparative Embodiment 1, indicating that a magnetic field is suitably formed in the Embodiments to avoid destruction of information magnetically recorded on a magnetic ticket and the like which might otherwise be caused by the leakage flux from the peripheral side face c . The angle t between the magnetic pole surface a and the peripheral side face c of the magnet 1 can be designed still larger. However, if the angle t is made too large, the angle between the magnetic pole surface b and the peripheral side face c becomes too small, making the edge of the magnet 1 between faces b and c too brittle. Even if the magnetic pole surface b is designed sufficiently large in area and the angle t is designed extremely large, the surface a on which the means B is to be attracted to its counterpart becomes relatively too small for use, nor is it preferable in terms of appearance. In view of the foregoing, the angle t between the magnetic pole surface a and the peripheral side face c of the magnet 1 is designed preferably to be 145° or smaller. Comparative Embodiment 2 The attracted means B of the fastener means of the Comparative Embodiment 2 shown in Figs. 18 through 20 is provided with the ferromagnetic projection 3b, which is directly contacted with the ferromagnetic plate 2a of the attraction means A within the through-hole 1a. The ferromagnetic member 2 is not provided with the projection 2b. The angle t between the magnetic pole surface a and the peripheral side face c of the magnet 1 in the attraction means A is 90°, the diameter of both the magnetic pole surfaces a and b is 19.1 mm, the plate thickness is 3.2 mm, the diameter of the through-hole 1a is 6.2 mm and the weight is 2.8 g. Table 4 shows the measurements of magnetic flux at P-1, P-2, P-3, P-4 and P-5 of the magnet 1 of the Comparative Embodiment 2 alone, of the magnet 1 attached with the ferromagnetic member 2 and when the attraction and attracted means A and B are assembled. The attraction force of the fastener means according to the Comparative Embodiment 2 was measured under the condition as shown in Fig. 20. As shown in Table 3, the average attraction force was 2.28 kg. Embodiment 3 The fastener means of Embodiment 3 shown in Figs. 21 through 23 comprises the attracted means B having the ferromagnetic projection 3b, which is directly contacted with the ferromagnetic plate 2a of the attraction means A within the through-hole 1a. The ferromagnetic member 2 is not provided with the projection 2b. The angle t between the magnetic pole surface a and the peripheral side face c is 95°. The diameter of the surface a is 18.7 mm, that of the surface b is 19.2 mm, the plate thickness is 3.2 mm, the diameter of the through hole 1a is 6.2 mm, and the weight is 2.8 g. Measurements of the leakage flux at P-1, P-2, P-3, P-4 and P-5 of the magnet 1 alone, of the magnet 1 attached with the ferromagnetic member 2 and of the magnet 1 attached with both the attraction and attracted means A and B respectively are shown in Table 4. The attraction force of the fastener means according to the Embodiment 3 was measured under the condition as shown in Fig. 23. As shown in Table 3, the average attraction force was 2.52 kg. Embodiment 4 The fastener means of the Embodiment 4 shown in Figs. 24 through 26 comprises the attracted means B having the ferromagnetic projection 3b, which is directly contacted with the ferromagnetic plate 2a of the attraction means A within the through-hole 1a. The ferromagnetic member 2 is not provided with the projection 2b. The angle t between the magnetic pole surface a and the peripheral side face c is 130°. The diameter of the surface a is 16 mm, that of the surface b is 21 mm, the plate thickness is 3.2 mm, the diameter of the through-hole 1a is 6.2 mm, and the weight is 2.8 g. Measurements of the leakage flux at P-1, P-2, P-3, P-4 and P-5 of the magnet 1 alone, of the magnet 1 attached with the ferromagnetic member 2 and of the magnet 1 attached with both the attraction and attracted means A and B respectively are shown in Table 4. The attraction force of the fastener means according to Embodiment 4 was measured under the condition as shown in Fig. 26. As shown in Table 3, the average attraction force was 2.57 kg. Attraction Force (kg) Measurement Comparative 2 Embodiment Embodiment 3 Embodiment 4 I 2.30 2.45 2.55 II 2.30 2.55 2.60 III 2.30 2.50 2.55 IV 2.20 2.55 2.55 V 2.30 2.55 2.60 Average 2.28 2.52 2.57 Intensity of Magnetic Flux (Gauss) Measurement point Comparative 2 Embodiment Embodiment 3 Embodiment 4 P-1 556 566 581 P-2 308 295 281 P-3 613 624 645 P-4 320 312 285 P-5 119 111 99 The permanent magnets 1 used in the Comparative Embodiment 2 and the Embodiments 3 and 4 all weigh 2.8 g, and are magnetized under the same conditions. It is evident that the attraction force of the Embodiment 3 shows an increase by 10.5 % and the Embodiment 4 an increase by 12.7 % as compared with the Comparative Embodiment 2. The values of leakage flux on the magnetic pole surface a of the magnet 1 in the Embodiments 3 and 4 at P-1 and P-3 respectively are greater than those of the Comparative Embodiment 2, indicating that an excellent magnetic field suitable for attracting the means B is formed. The values of leakage flux on the peripheral side face c of the magnet 1 at P-2, P-4 and P-5 in the Embodiments 3 and 4 respectively are smaller than those of the Comparative Embodiment 2, indicating that a magnetic field is suitably formed in the Embodiments to avoid destruction of information magnetically recorded on a magnetic ticket and the like which might otherwise be caused by the leakage flux from the peripheral side face c . Comparative Embodiment 3 The attracted means B of the fastener means shown in Figs. 27 through 29 has no ferromagnetic projection 3b; instead, the ferromagnetic projection 2b projecting inside the through-hole 1a of the magnet 1 is directly contacted with the ferromagnetic plate 3a of the attracted means B. The angle t between the magnetic pole surface a and the peripheral side face c of the magnet 1 in the attraction means A is 90°, the diameter of both the magnetic pole surfaces a and b is 19.1 mm, the plate thickness is 3.2 mm, the diameter of the through-hole 1a is 6.2 mm and the weight is 2.8 g. Table 6 shows the measurements of magnetic flux at P-1, P-2, P-3, P-4 and P-5 of the magnet 1 of the Comparative Embodiment 3 alone, of the magnet 1 attached with the ferromagnetic member 2 and when the attraction and attracted means A and B are assembled. The attraction force of the fastener means according to the Comparative Embodiment 3 was measured under the condition as shown in Fig. 29. As shown in Table 5, the average attraction force was 2.25 kg. Embodiment 5 The attracted member B of the fastener means according to the Embodiment 5 shown in Figs. 30 through 32 is not provided with the ferromagnetic projection 3b; instead, the ferromagnetic projection 2b projecting within the through-hole 1a is directly contacted with the ferromagnetic plate 3a of the attracted means B. The angle t between the magnetic pole surface a and the peripheral side face c is 95°. The diameter of the surface a is 18.7 mm, that of the surface b is 19.2 mm, the plate thickness is 3.2 mm, the diameter of the through-hole 1a is 6.2 mm, and the weight is 2.8 g. Measurements of leakage flux at P-1, P-2, P-3, P-4 and P-5 of the magnet 1 of the Embodiment 5 alone, of the magnet 1 attached with the ferromagnetic member 2 and of the magnet 1 attached with both the attraction and attracted means A and B respectively are shown in Table 6. The attraction force of the fastener means according to the Embodiment 5 was measured under the condition as shown in Fig. 32. As shown in Table 5, the average attraction force was 2.48 kg. Embodiment 6 The attracted means B of the fastener means according to the Embodiment 6 shown in Figs. 33 through 35 is not provided with the ferromagnetic projection 3b; instead, the ferromagnetic projection 2b projecting within the through-hole 1a is directly contacted with the ferromagnetic plate 3a of the attracted means B. The angle t between the magnetic pole surface a and the peripheral side face c is 130°. The diameter of the surface a is 16 mm, that of the surface b is 21 mm, the plate thickness is 3.2 mm, the diameter of the through-hole 1a is 6.2 mm, and the weight is 2.8 g. Measurements of leakage flux at P-1, P-2, P-3, P-4 and P-5 of the magnet 1 of Embodiment 6 alone, of the magnet 1 attached with the ferromagnetic member 2 and of the magnet 1 attached with both the attraction and attracted means A and B respectively are shown in Table 6. The attraction force of the fastener means according to Embodiment 6 was measured under the condition as shown in Fig. 35. As shown in Table 5, the average attraction force was 2.52 kg. Attraction Force (kg) Measurement Comparative 3 Embodiment Embodiment 5 Embodiment 6 I 2.20 2.50 2.55 II 2.30 2.45 2.50 III 2.15 2.50 2.50 IV 2.30 2.40 2.55 V 2.30 2.55 2.50 Average 2.25 2.48 2.52 Intensity of Magnetic Flux (Gauss) Measurement point Comparative 2 Embodiment Embodiment 3 Embodiment 4 P-1 556 566 581 P-2 308 295 281 P-3 653 667 684 P-4 272 265 242 P-5 120 112 100 The permanent magnets 1 used in the Comparative Embodiment 3 and the Embodiments 5 and 6 all weigh 2.8 g, and are magnetized under the same conditions. It is evident that the attraction force of the means of the Embodiment 5 shows an increase by 10.2 % and that of the Embodiment 6 an increase by 12.0 % as compared with the Comparative Embodiment 3. The values of leakage flux on the magnetic pole surface a of the Embodiments 5 and 6 at P-1 and P-3 respectively are greater than those of the Comparative Embodiment 3, indicating that an excellent magnetic field suitable for attracting the means B is formed. The values of leakage flux on the peripheral side face c of the magnet 1 at P-2, P-4 and P-5 in the Embodiments 5 and 6 respectively are smaller than those of the Comparative Embodiment 3, indicating that a magnetic field is suitably formed in the Embodiments to avoid destruction of information magnetically recorded on a magnetic ticket and the like which might otherwise be caused by the leakage flux from the peripheral side face c . The peripheral side face c of the attraction means A as shown in Fig. 36 is not a simple slope connecting the magnetic pole surfaces a and b at a gradient; rather, the side face c rises at a right angle from the surface b and is tapered at an upper portion. The angle t between the surface a and the side face c is therefore the angle at this bend leading to the surface a . The peripheral side face c of the attraction means A as shown in Fig. 37 is curved toward the surface a . The angle t between the surface a and the side face c is the angle between the surface a and the line segment connecting the start and the end of the curve. In Fig. 38, the ferromagnetic projection 2b of the ferromagnetic member 2 is pressed into the through-hole 1a of the magnet 1 to assemble the magnet 1 and the ferromagnetic member 2 of the attraction means A. In Fig. 39, the peripheral side of the magnet 1 is covered with a non-magnetic casing 11 to protect and assemble the same with the ferromagnetic member 2. In Fig. 40, the non-magnetic casing 11 is a rectangle box with an opening on the bottom and a hole connecting to the hole 1a on the top, and has spaces 12 inside the casing 11. This construction prevents destruction of information magnetically recorded on a magnetic medium such as the bank cashing card or the credit card caused by leakage flux of the magnet 1 housed inside the casing together with the ferromagnetic member 2. As mentioned above, because the angle t formed between the magnetic pole surface a of the magnet 1 constituting the attraction means A and the peripheral side face c extending between the magnetic poles is 95° or greater, the space between the magnetic poles including the peripheral side face c has a greater magnetic reluctance, and the magnetic flux of the permanent magnet 1 will form a magnetic circuit mainly comprising the ferromagnetic means 2 and 3 that are abutted against and attracted to each other via the through-hole 1a of the permanent magnet 1. We have found that with the angle t between the magnetic pole surface a and the peripheral side face c of the permanent magnet 1 constituting the attraction means A being 95° or larger, magnetic flux leaking outside from the peripheral side face c is reduced, and the magnetic flux of the permanent magnet 1 can be concentrated on the contact point between the ferromagnetic member 3 of the attracted means B and the ferromagnetic member 2 of the attraction means A to secure high attraction force. Because of lower leakage flux on the peripheral side face c , the risk of destruction of information magnetically recorded on a magnetic medium such as the bank cashing card and the like is reduced.

Claims: A fastener means for fastening first and second elements (D, D) for example a handbag and a flap for closure of the same comprising: an attraction means (A) comprising a permanent magnet (1) and adapted to be attached to said first element (D); and means (B) adapted to be attracted to said attraction means (A) but not incorporating a permanent magnet, said means (B) to be attracted being adapted to be attached to said second element; said permanent magnet (1) of said attraction means (A) having a through hole (1a) extending between opposite end surfaces (a, b) thereof, a first pole of first magnetic polarity adjacent one said end surface (a) which is oriented to extend in the direction away from said first element when said attraction means (A) is attached thereto, and a second pole of opposite magnetic polarity adjacent the other said end surface (b), and a peripheral side face (c) extending between said end surfaces (a, b), and a ferromagnetic member (2) attached to said other end surface (b), said attraction means (A) being adapted to be attached to said first element via said ferromagnetic member (2); and said means (B) to be attracted comprising a ferromagnetic member (3) arranged to be detachably attracted to said first pole; said fastener means being characterised in that one and/or the other of said ferromagnetic members (2, 3) in the form of a plate having a post (2b, 3b) adapted for extending into said through hole (1a), such that said ferromagnetic members (2, 3) are abutted against and attracted to each other via said through hole (1a) to complete a magnetic circuit from one said pole to the other of said permanent magnet (1) within said through hole (1a), and in that the angle formed by said one end surface (a) and said peripheral side face (c) is 95° or larger. A fastener means according to Claim 1, further characterised in that said attraction means (A) further comprises a covering (11). A fastener means according to Claim 2, further characterised in that said covering (11) is a casing. A fastener means according to Claim 3, further characterised in that said second ferromagnetic member is attached to said magnet by means of said casing. A fastener means according to Claim 2, further characterised in that said covering (11) is a plating.

Inventors: MORITA TAMAO, MORITA, TAMAO
Applicants: TARMO CO LTD, TARMO CO. LTD.
Application year: 1991
Main classification: A41F1
IPC codes: A45C13, H01F7, A41F1