GB2186625A - Magnetic catch - Google Patents

Abstract

The catch comprises a first part A having a permanent magnet 1 with a hole H therethrough and a one pole face a, and a second part B ferromagnetic backing plate 2 against in the form of a second ferromagnetic plate 3 with a projection 3a locatable in the hole H. The hole terminates in an opening which is greater in one dimension than in another perpendicular thereto. This opening may be defined by the magnet having a uniform hole of this shape, or by a casing member covering at least the pole face b. The shape of the hole allows the catch to be released by pivoting the parts apart about a point on the edge of the magnet in line with the greater dimension of the opening, whilst preventing inadvertent tilting in any other direction. The catch may be used on handbags, jewellery or as a support for a hook. <IMAGE>

Description

SPECIFICATION Fastener This invention is concerned with fasteners of the kind comprising first and second fastener members adapted to be magnetically attracted to each other, the first and second fastener members being adapted respectively to be fixed to two elements desired to be fastened together by use of the fastener.

There are numerous proposals in the prior art for magnetic fasteners of this kind. It is a common practice for the first fastener member to comprise a first ferromagnetic member and an apertured permanent magnet and for the second fastener member to comprise a second ferromagnetic member provided with a forwardly directed projection thereon adapted to make contact with the first ferromagnetic member through the said aperture when the first and second fastener members are attracted towards each other.

A number of improvements in such magnetic fasteners have been proposed by the present Applicant. The reader is directed, for example, to U.S. Patents Nos: 4021891 and 4453294 and to British Patent Specification No: 2173244, the latter disclosing how the permanent magnet can be made in such a way which enables a previously conventional case for the permanent magnet to be eliminated.

Nevertheiess, as will be explained in more detail below with reference to the accompanying drawings, I have found that the previous proposals still suffer from a disadvantage namely either that the two fastener elements are difficult to disengage by simple leverage or alternatively where they are readily detachable by simple leverage, there is a danger for the fastener inadvertently to become disengaged as a result of leverage occurring in ndrmal use of the article in which the fastener is provided.

The present invention has arisen from my work seeking to provide improved constructions for such magnetic fasteners.

In accordance with the present invention, there is provided a fastener comprising first and second fastener members; the first fastener member comprising a first ferromagnetic member and a permanent magnet, the first ferromagnetic member being coupled to the permanent magnet in facial contact with one magnetic pole surface thereof, and the first fastener member having an outwardly directed surface on the opposite side thereof from the said first ferromagnetic member and provided by a second magnetic pole surface of said permanent magnet of opposite polarity to said one magnetic pole surface or a casing extending at least part way about the said first fastener member, and the first fastener member including a hole extending from said outwardly directed surface to said first ferromagnetic member, the opening of said hole at said outwardly directed surface having a diameter greater in one direction than perpendicular thereto; the second fastener member comprising a second ferromagnetic member provided with a forwardly directed projection and being adapted to be attracted toward said first fastener member into a position in which it makes contact with the outwardly directed surface of said first fastener member with said projection located within the hole and magnetically attracted to the first ferromagnetic member or a projection of the said first ferromagnetic member upstanding within the hole.

The invention is hereinafter more particularly described by way of example only with reference to the accompanying drawings in which: Fig. 1 is a sectional view through an embodiment of fastener constructed in accordance with the present invention, illustrating both the basic structure and the lines of force; Fig. 2 is a view generally similar to Fig. 1 illustrating the first and second fastener members separated; Fig. 3 is an overall perspective view of the embodiment of Figs. 1 and 2; Fig. 4 is a top plan view of the first fastener member of the embodiment of Fig. 3; Fig. 5 is a sectional view similar to Fig. 1 but omitting the lines of force, and taken along the line X-X in Fig. 4; Fig. 6 is a view generally similar to that of Fig. 5, for an alternative embodiment, as it would be seen along the line Y-Y in Fig. 4;; Figs. 7 to 14 are sectional views, in each case as they would be seen taken along a line corresponding to the line Y-Y in Fig. 4, for various modified embodiments; Figs. 15 to 21 are sectional views through various embodiments of one ferromagnetic member illustrating different ways in which the fastener members may be connected to one of a pair of members adapted to be fastened by means of the fastener; Figs. 22 and 23 illustrate in section, two further alternative embodiments for the fastener; and Fig. 24 is a cross-sectional view of a prior proposed fastener.

Magnetic fasteners comprising first and second fastener members magnetically attracted towards each other are known in the patent literature.

Referring to Fig. 24, which shows one prior proposal, the first fastener member typically comprises a ferromagnetic member 102 and a permanent magnet 101. The ferromagnetic member 102 is coupled to the magnet 101 in facial contact with one magnetic pole surface thereof. The magnet 101 has a central hole 101a and the ferromagnetic member 102 has an upstanding projection 102a within the hole.

The second fastener member 103 may comprise a ferromagnetic member which is gener ally similar to the ferromagnetic member 102.

It has a forwardly directed projection 103a.

The permanent magnet 101 may suitably be made of a sintered magnet material such as ferrite protected with a metal case, not illustrated in Fig. 24. Alternatively, the magnet may be made of a synthetic resin material in which magnetic particles are embedded, thereby eliminating the need for a case. The hole 101a constitutes an important feature of this form of fastener since, as will be seen from Fig. 24, when the second fastener member 103 is attracted into facial contact with the outwardly directed surface of the first fastener member, the projections 102a and 103a make contact with each other within the hole 101a. The permanent magnet 101 has its magnetic pole surfaces on its opposed axial end faces so that the hole is generally to be considered as magnetically neutral.However, as a result of the two projections making contact with each other within the hole, a magnetic circuit from the permanent magnet 101 through ferromagnetic member 103 and its projection 103a, projection 102a and ferromagnetic member 102 is completed backed to the permanent magnet 101. There is strong attraction between the two projections within the hole enhancing the fastening effect.

To facilitate insertion of the projection 103a into the hole 101a to enable the two fastener members to be engaged, the diameter of the hole is made significantly larger than the diameter of the projections by a radial dimension x. This arrangement enables ready engagement, avoiding the projection 103a being caught at the edge of the hole or at an angle within the hole against the inner wall thereof, even if the second fastener member is offered up to the first at an inclination.

With this arrangement, the first and second fastener members are readily disengaged by applying leverage in the manner illustrated in phantom in Fig. 24 using the edge of the first fastener member as a fulcrum.

Magnetic fasteners of this general kind are widely employed as handbag fasteners. The ready disengagement feature may be disadvantageous when the fastener is used for this purpose. For instance, if the leather used for a handbag lid is relatively thick or relatively inflexible, the material of a handbag lid may itself exert a leverage force in its natural state on the fastener, the material seeking to return to the situation where the handbag is open.

Equally, when a handbag is rather full, as is common, then a sideways or leverage force may again be exerted on the fastener tending to open the handbag.

Thus, we have found that the very presence of the radial space x necessary to enable the fastener readily to be engaged can lead to inadvertent opening of the fastener when used for example on a handbag. Users find this inconvenient. The present invention adopts a solution to this problem which, in retrospect, appears extremely simple. However, to the best of Applicant's knowledge, despite the fact that a considerable number of magnetic fasteners of the kind with which the present invention is concerned have been manufactured and employed in handbags in the past, the relatively simple solution now proposed to the problems which have long existed has never previously been suggested.

Referring now to Figs. 1 to 5, a typical embodiment of fastener constructed in accordance with the present invention comprises a first or female fastener member A and a second or male fastener member B. The female member A comprises a plate of ferromagnetic material 2 coupled to one magnetic pole surface a of a permanent magnet 1 suitably formed of sintered ferrite or in the form of a plastics magnet in which magnetic particles are embedded in a plastics matrix. The male member B is attracted towards the outwardly directed surface of the female member A, in this case provided by the second pole surface b of permanent magnet 1. A projection 3a of ferromagnetic member 3 which forms the male member B is attracted to an upstanding projection 2a within a central hole 1a. As can best be seen in Figs. 3 and 4, the hole la consists of a shape H in the form of a flattened oval.Its dimension or diameter d in one direction (the sectional view of Fig. 5) is substantially greater than its diameter or dimension d in a directiqn at right-angles thereto (the sectional view of Fig. 2). As can be seen from Figs. 1 and 2, the dimension d is only slightly greater than the diameter of the projection 3a which may be generally cylindrical.

The embodiment of fastener described above and illustrated in Figs. 1 to 5 has the advantages of the prior art in forming a closed magnetic circuit by contacts between the two ferromagnetic members 2 and 3 concentrating the magnetic flux through these members within the hole. Engagement and disengagement between the two fastener members is relatively easy in the direction of the longer dimension d of the hole H so that the two fastener members can readily be engaged together or disengaged from each other when required. On the contrary, in the other direction of the small dimension d, any attempt to disengage the two fastener elements other than in the direct axial direction of the fastener is difficult for an attempt to lever the male member B from the female member A results in interference between the projection 3a and the internal surface of the hole resist ing disengagement and tending to return the two fastener members into facial contact with each other.

In use, for example on a handbag or the like, the fastener of Figs. 1 to 5 is suitably attached such that the shorter diameter of the hole la on the female member A is parallel to the open/closed direction of the lid. Alternatively, if the fastener is used on a necklace or metal chain, then the shorter diameter will be parallel to the direction of the tensile stress.

By reducing the diameter of the hole in the fashion illustrated, while maintaining a relatively large diameter in the direction at rightangles, the fastener exhibits an enhanced fastening effect even where the fastener is made relatively smaller than in such fasteners heretofore so that there is in effect a smaller magnetic force holding the two fastener members together.

Fig. 6 shows an alternative embodiment in which there is no upstanding projection on the ferromagnetic member 2, the forwardly directed projection 3a of the second fastener member being correspondingly greater in dimension so that it makes contact with the ferromagnetic plate 2. As will be appreciated, this arrangement is precisely equivalent to that of the arrangement of Figs. 1 to 5 with the magnetic lines of force again being induced onto the projections in view of the low magnetic reluctance of the ferromagnetic material of the members 2 and 3.

Figs. 7 to 14 show a number of ways in which the basic embodiment of Figs. 1 to 5 may be modified. Where appropriate, like reference numerals are employed in the various figures.

Thus, in each of Figs. 7 to 10, the permanent magnet 1 and ferromagnetic member 2 are held together within a non-magnetic case 4 which may be made, for example, of brass.

This construction is suitable for the case where the magnet 1 is made of a relatively brittle material such as sintered ferrite. As will be seen, in each of Figs. 7, 8 and 9, the case 4 has an inturned lip 4a' defining the shape of the opening 4a of the hole H at the outwardly directed surface of the female fastener member. The opening 4a may have a shape which corresponds exactly to the shape of the hole H of the embodiment of Figs. 1 to 5, apart from the thickness of the material of the case, and having a diameter longer in one direction than it is in a direction at right-angles thereto.

Alternatively, the opening 4a alone may take the shape of the hole H illustrated in Figs. 1 to 5, while the underlying hole la of the magnet 1 may be cylindrical, its diameter generally corresponding to the largest diameter of the opening 4a.

In the Fig. 7 arrangement, the second magnetic pole surface b of the permanent magnet 1 makes contact with the inside surface of the case 4, which generally has the form of a flattened dome. The case 4 is secured about the ferromagnetic member 2 by means of inwardly bent pawls 4b. The inwardly directed lip of the case 4 in effect forms a flange 4a'.

The arrangement of Fig. 8 is generally similar to Fig. 7 with the exception that a shielding plate 5 is interposed between the magnetic pole surface b and the surface of the case 4.

The purpose of this is to avoid inadvertent contact between, say, a magnetic strip on a bank card or the like inadvertently making contact with the outwardly directed surface of the first fastener member. Fig. 9 shows a further modification, namely the provision of an upstanding ridge or flange 4c about the periphery of the first fastener member. This ridge or flange has two advantages. Firstly, even if there still remains some leakage of magnetic flux despite the provision of the shielding plate 5, this flux will tend to be concentrated in the region of the pole face b. Flux in the region of the outer edge of the ridge or flange 4c will be slight and insufficient to affect magnetic recordings on bank cards, magnetic tapes and the like, even if contact is inadvertently made.

A second advantage is that in this arrangement the second fastener element fits into the well effectively defined by the ridge or flange 4c which tends to prevent sideways movement of the second member relative to the first.

Fig. 10 shows a modified arrangement in which the case 4 is of reduced extent on the outwardly directed surface of the first fastener member, simply having pawls 4b received in corresponding notches on the outwardly directed surface of the shielding plate 5.

Figs. 11 to 14 show alternative constructions which are suitable when the permanent magnet 1 is made of a plastics material in which is embedded a hard magnetic powder made of ferrite, alnico or from the rare earths.

Such a permanent magnet may be formed by punching out a generally circular shape from a sheet of such material. However, it is preferably made by moulding the material in a metal die, which achieves higher dimensional precision and enables the ferromagnetic member 2 to be incorporated with the magnet 1 in an integrated structure during the moulding operation. The magnet 1 is suitably formed so that the resinous material in which the magnetic powder is embedded forms a resilient skin layer on its surface. Such magnets show relatively high impact strength while maintaining relatively high magnetic capacity. No case 4 is required and a magnetic plate 2b forming the ferromagnetic member 2 may be moulded together with the material of the permanent magnet 1 in the same die or, alternatively, may be bonded thereto with an adhesive. A number of modifications are possible.Thus, in Fig. 12, the permanent magnet is moulded with an upstanding flange or ridge 1b. In Fig.

13 a shielding plate 5 is integrally moulded with the magnet 1 being partially embedded in its surface. Fig. 14 shows a corresponding arrangement with a flange 1b.

Figs. 15 to 21 illustrate a number of embodiments of ferromagnetic plate, equally suitable for the first or second ferromagnetic members, and illustrate various ways in which the projection such as projection 2a may be formed thereon and also a number of ways in which the fastener members can be connected to respective members intended to be fastened together by means of the fastener.

In Fig. 15 the projection 2a is integral with plate 2b and a generally U-shaped member having two legs 6 is welded to the reverse side of the plate. In Fig. 16 the projection 2a is formed separately from the plate 2b being effectively riveted thereto and to the U-shaped member providing the legs 6 through holes such as 2c in the centre thereof, a narrow rod 2a' of the projection 2a passing through the holes and being flattened on the reverse side.

In Fig. 17 means 6 for connecting the plate 2 to a member to be fastened to another by means of the fastener is in the form of a short tube 6 welded or brazed through its flange 6a to the plate 2b, The pipe-like member 6 in this case is passed through an opening in material fabric of a bag or the like and then flattened like an eyelet, suitably with a washer interposed.

Fig. 18 shows a modified arrangement involving a loop rather than a pipe in the centre.

Fig. 19 shows another arrangement in which the projection 2a is riveted to the plate 2b and to a seat plate 6b which holds the rim of a pipe member 6, again fastened to the material of a bag or the like in the manner of an eyelet.

As can be seen from Figs. 20 and 21, the projection 2a may be formed on the reverse side of the plate 2b with a root which may have either a pointed structure, or a threaded structure or, indeed, a pointed structure which is also threaded. By these means, the ferromagnetic plate can readily be coupled to any appropriate material. Fig. 22 shows an alternative embodiment of fastener suitable for use in a necklace, bracelet or belt. The respective ferromagnetic members 2 and 3 have no legs or other connecting members on their reverse side. Instead, they are provided with attachment holes 2b' and 3b' respectively for connection, for example, to a chain 7. By forming the ferromagnetic member 3 in a cranked configuration as shown in Fig. 22, when the fastener is connected, the two lengths of chain 7 are in line.

Fig. 23 shows an embodiment of fastener constructed in accordance with the present invention suitable for use as a hanger. As can be seen in Fig. 23, the projection 2a has a root which may be formed either as a nail or as a wood screw which is either driven home or screwed into place within the hole H to mount the female member to a wall or post.

The male member 3 is formed with a hook.

As will be seen, the hole H is orientated so that the narrow dimension is in the vertical plane so that the force of gravity does not lead to ready disengagement, ready disengagement being possible by sideways leverage.

Claims (6)

1. A fastener comprising first and second fastener members; the first fastener member comprising a first ferromagnetic member and a permanent magnet, the first ferromagnetic member being coupled to the permanent magnet in facial contact with one magnetic pole surface thereof, and the first fastener member having an outwardly directed surface on the opposite side thereof from the said first ferromagnetic member and provided by a second magnetic pole surface of said permanent magnet of opposite polarity to said one magnetic pole surface or a casing extending at least part way about the said first fastener member, and the first fastener member including a hole extending from said outwardly directed surface to said first ferromagnetic member, the opening of said hole at said outwardly directed surface having a diameter greater in one direction than perpendicular thereto; the second fastener member comprising a second ferromagnetic member provided with a forwardly directed projection and being adapted to be attracted toward said first fastener member into a position in which it makes contact with the outwardly directed surface of said first fastener member with said projection located within the hole and magnetically attracted to the first ferromagnetic member or a projection of the said first ferromagnetic member upstanding within the hole.

2. A fastener according to Claim 1, wherein the said outwardly directed surface is provided by the said second magnetic pole surface of the permanent magnet, the permanent magnet being formed ab initio with the said hole, which hole has a uniform cross-section along its length.

3. A fastener according to Claim 1, wherein the cross-section of the said hole within the permanent magnet differs from the cross-section of the hole where it opens on the said outwardly directed surface, the cross-section at said outwardly directed surface being defined by the said case.

4. A fastener according to any preceding Claim, wherein the said forwardly directed projection is generally cylindrical in configuration, the said projection making contact with the surface of the said first ferromagnetic member to form a complete magnetic circuit when the second ferromagnetic member is in facial contact with the said outwardly directed surface.

5. A fastener according to any of Claims 1 to 3, wherein both said outwardly directed projection and said upstanding projection are generally cylindrical in configuration, the two said projections being adapted to make contact with each other when the said second ferromagnetic member makes facial contact with the said outwardly directed surface of the first fastener member, thereby providing a complete magnetic circuit.

6. A fastener substantially as hereinbefore described with reference to Figs. 1 to 23 of the accompanying drawings.