GB2395744A

GB2395744A - Magnetic retaining device

Info

Publication number: GB2395744A
Application number: GB0227228A
Authority: GB
Inventors: Keith Blunden; James Bell
Original assignee: Magnet Applications Ltd
Current assignee: Magnet Applications Ltd
Priority date: 2002-11-21
Filing date: 2002-11-21
Publication date: 2004-06-02
Also published as: GB0227228D0

Abstract

A magnetic retaining device comprising first 1 and second 2 magnetic elements movable between engaged and disengaged positions, wherein: ```the first magnetic element defines an aperture 5 having an entrance and an opposing end, there being a magnetic pole adjacent the entrance and a second, unlike magnetic pole adjacent the end; ```the second magnetic element has a pair of unlike magnetic poles; ```in the engaged position, the second magnetic element is received in the aperture such that the magnetic poles of the first magnetic element are adjacent the respective unlike poles of the second magnetic element; and ```in order to move into or out of the engaged position, a magnetic pole of the second magnetic element must pass in close proximity to a like magnetic pole of the first magnetic element.

Description

À 1 Magnetic Retaining Device The present invention relates to a magnetic

retaining device which is particularly useful for 5 retaining lids and doors of various types of housings and containers.

It is well known to employ magnetic retaining or fastening devices on a variety of housings and 10 containers, in which the retaining effect relies -

primarily upon magnetic forces of attraction between unlike poles of a magnetic materials. Examples of such containers are handbags, luggage, storage boxes and various items of furniture.

The magnetic devices conventionally comprise two elements, a magnetically attractive element and a magnetically attractable element.

20 One of these elements is conventionally attached to the movable lid part of the container, such as the flexible material of the cover of a handbag, or the lid or the frame of a rigid housing of a storage box or item of furniture.

Either one or both of the magnetically attractive and magnetically attractable elements conventionally comprise a permanent magnet. The permanent magnet on the attractive element may have 30 an annular shape which defines an axial bore. The magnetically attractable element may further comprise a magnetic projecting member which engages within the axial bore on the magnetically attractive element when the two couple together under the 35 attraction of suitably oriented unlike magnetic

poles. Both elements often further comprise ferromagnetic plates which are in contact with the 5 permanent magnets of the respective elements.

Often, there is also a mechanical interference complementing the magnetic interaction between the two elements. For example, the magnetic projecting 10 member (and/or the receiving surface with which it is in contact) may be machined such that the mutually contacting surfaces are textured to create enhanced frictional forces when the two surfaces are moved relative to one another.

Known magnetic retaining devices depend primarily upon magnetic attraction to keep their parts in the closed position while often using mechanical means to help prevent lateral or axial 20 movement and thus disengagement. However, these combined means are often insufficient to retain the two magnetic elements of the device in the closed position when the container is subjected to extreme forces. For example, storage boxes employing magnetic retaining devices which are used in a dynamic application (such as storage containers in cars) must ideally be adapted to withstand high lateral 30 and axial forces, in the event of an impact. This will help prevent the storage container cover flying open and spilling its contents to dangerous effect.

Accordingly, the present invention provides a 35 magnetic retaining device comprising first and

- 3 second magnetic elements movable between engaged and disengaged positions, wherein: the first magnetic element defines an aperture having an entrance and an opposing end, there being 5 a magnetic pole adjacent the entrance and a second, unlike magnetic pole adjacent the end; the second magnetic element has a pair of unlike magnetic poles; in the engaged position, the second magnetic 10 element is received in the aperture such that the -

magnetic poles of the first magnetic element are adjacent the respective unlike poles of the second magnetic element; and in order to move into or out of the engaged 15 position, a magnetic pole of the second magnetic element must pass in close proximity to a like magnetic pole of the first magnetic element.

The retaining action of the device of the 20 present invention is dependent particularly on the orientation of magnetic poles of the respective magnetic elements when the device is in operation.

The magnetic forces may provide a resisting 25 effect to the motion of the moving part to which the second magnetic element is affixed. Accordingly, the magnetic retaining device of the present invention is suitable for sustaining high forces acting to separate the surfaces to be retained 30 together. Thus, the device may be used in trim applications in commercial vehicles, passenger cars, vans and trucks such as centre consoles, glove boxes and armrests. The device may, however, also be used in furniture housings, domestic boilers, office 35 equipment, for example on flaps or doors.

- 4 The first and second magnetic elements will typically consist of or comprise a permanent magnet.

The first magnetic element may have any suitable 5 shape. For example, it may be annular or rectangular. The term annular" as used herein refers to any element in which there is an aperture, for example ring-shaped, rectangular or square-

shaped elements. Alternatively, the element may 10 comprise two discrete sections, with an aperture -

therebetween. The second magnetic element is configured so as to be insertable into the first magnetic element.

15 The first magnetic element of the present invention is preferably configured and has dimensions such that a clearance around the projection when in the aperture of preferably no less than 0.5mm is maintained between the first and 20 second magnetic elements when the two are coupled together. In a preferred embodiment of the present invention, a plate or member is located at each end 25 of the first and second magnetic elements. In a preferred configuration, the plate or member located at the end of the first magnetic element constituting the entrance of the aperture is annular. In a preferred configuration employed in the present invention, the plates or members are used as return paths or armatures to concentrate the magnetic flux emanating from the permanent magnets.

35 The plates or members preferably comprise a

- 5 ferromagnetic material, advantageously ferrous steel. A further advantageous feature of the present 5 magnetic retaining device is the provision of an interface material between the engaging surfaces of the first and second magnetic elements which may serve to reduce noise upon closure. A suitable material is any compliant interface material, but 10 preferably, rubber or fabric are used.

A range of permanent magnets may be employed in the device, whether based upon a rare earth or non-

rare earth magnet. Preferred magnets (either in 15 fully dense or bonded form) are ceramic magnets based upon strontium or barium ferrite or rare earth magnets based upon samarium cobalt or a neodymium iron boron magnet.

20 The siting of respective elements of the magnetic retaining device of the present invention is not restricted to any particular portion of the two surfaces on the storage container which are to be engaged. Advantageously, the second magnetic 25 element is positioned at the leading edge of the moving part (such as the lid or door).

The invention will now be described in detail, by way of example only, with reference to the 30 accompanying drawings in which: Figure 1 is a cross section of the first and second magnetic elements in accordance with one embodiment of the invention, when disengaged;

- 6 Figures 2 a-c are plan views of alternative embodiments of the invention; Figure 3 is a side view of a storage container 5 with a magnetic retaining device according to the present invention sited in two possible positions (A, B); and Figures 4 a-e are a cross section of the.

10 magnetic retaining device in operation, showing the-

relative positions of the magnetic elements at five points during the process of engaging and disengaging the two.

15 Referring to Figure 1, a magnetic retaining device in accordance with a first embodiment of the invention includes a first magnetic element 1 and a second magnetic element 2 that are capable of being detachably coupled 20 magnetically.

Specifically, the first element 1 includes an annular permanent magnet 1B having a central aperture 5, an annular plate 1C covering the first 25 end of permanent magnet 1B and with an opening to allow access to the aperture 5, and a continuous plate 1A abutting the second axial end of permanent magnet 1B.

30 As is seen from Figure 1, a portion of the plate 1A abutting permanent magnet 1B closes off the axial aperture 5 defined by the permanent magnet 1B.

The second magnetic element 2 includes a second 35 permanent magnet 2B. The second magnetic element 2

- 7 - further comprises a plate 2C abutting a first end of the permanent magnet 2B and a plate 2A abutting the second end of the permanent magnet 2B.

5 In a preferred configuration of the present invention, the plates of the respective magnetic elements 1 and 2 are used as return paths or armatures to concentrate the magnetic flux emanating from the permanent magnets 1B and 2B. In particular, 10 the device effectively uses virtually all of the magnetic flux available by controlling and encapsulating it as a result of the spatial arrangement of respective plates and permanent magnets. The spatial proximity of plates and 15 permanent magnet forces the flux into a path which is as close as possible to the surface of the magnet, without shorting out the magnetic surface.

In addition to providing the effect of 20 concentrating the magnetic flux, since the plates of respective magnetic elements 1 and 2 comprise ferromagnetic materials, the lines of force from the permanent magnets 1B and 2B couple with those from the ferromagnetic plates, thus further enhancing the 25 available magnetic flux. The plates 1C, 2C, 1A and 2A of the respective magnetic elements comprise a ferromagnetic material, advantageously ferrous steel. 30 The effect of concentration of magnetic flux which the plates 1C, 2C, 1A and 2A carry out serves to minimise radial and lateral leakage of flux around the perimeter of the magnetic elements. This minimization of flux leakage has the further advantage of reducing 35 damage to devices such as credit cards, computer disks

and other items which store information on magnetic media. In the magnetic retaining device of the present 5 invention the first magnetic element 1 has one pole, e.g. a south pole in Figure 1, at its first end adjacent the plate 1A, and an opposite pole, e.g. a north pole in Figure 1, at its second end adjacent the plate 1C.

The second magnetic element 2 is arranged such that at its first end adjacent the plate 2C it has a pole opposite to that at the first end of the first magnetic element 1, e.g. a north pole in Figure 1.

15 Similarly, the second magnetic element 2 has at its second end adjacent the plate 2A a pole opposite to that at the second end of the first magnetic element 1, e.g. a south pole in Figure 1.

20 In this way, when the second magnetic element 2 is inserted in the aperture 5, magnetic attraction between the opposite poles at the respective first ends of the first and second magnetic elements 1,2 couples the two elements together.

In the preferred embodiment of the present invention illustrated in Figure 1, a pad of compliant interface material 3 is present between the engaging surfaces of the magnetic elements 1,2.

30 The pad 3 may be provided on the plate 2C of second magnetic element 2 and/or on the surface of plate 1A which forms the closed end of the aperture 5.

The pad 3 serves to minimise the sound of the 35 metallic "click" commonly heard when magnets are

- 9 - drawn together and serves to protect the respective surfaces from scratching.

Figure 2 illustrates three alternative 5 embodiments of the magnetic elements 1,2.

Figure 2(a) is a plan view corresponding to Figure 1, of the annular first magnetic element comprising an annular permanent magnet 1B which 10 defines a concentric circular aperture 5, receiving a circular second magnetic element 2.

Figure 2(b) illustrates an embodiment in which two permanent magnets (1B and 1B') of substantially 15 rectangular shape are arranged parallel to define a substantially rectangular aperture 5 between them, receiving a substantially rectangular second magnetic element 2.

20 Figure 2(c) illustrates an annular first magnet element 1 comprising an annular permanent magnet 1B which defines a concentric square aperture 5, receiving a square second magnetic element 2.

25 It will be appreciated that there are many other possibilities for the configuration of the two magnetic elements 1,2 and these examples are not limiting. 30 Figure 3 illustrates two possible positions A and B. respectively, at which a magnetic retaining device according to the present invention may be sited on a storage container 1, although many other positions are also possible. The container 1 comprises a housing 10 35 joined to a lid 11 at hinge 12. The first magnetic

element 1 is located on the housing 10 and the second magnetic element 2 is located on the lid 11, although these positions could be reversed.

5 In position A, the device is sited such that the second magnetic element 2 is located towards the leading edge of the movable lid 11, remote from the hinge 12. In position B the device is located near the hinge mechanism 12 (or fulcrum). Location in 10 position B might favour an uncluttered fixing if the retaining device is just one of a number of components present on the two surfaces to be engaged. The device may also be built into the hinge moulding or stamping to serve this objective.

Figures 4(a) through to 4(e) illustrate the relative positions of the magnetic elements 1,2 as the two elements proceed from a fully separated to a fully engaged position, in response to a downward 20 force represented by the arrow in the figure. This force is in a direction generally parallel to the longitudinal axis of the permanent magnets 1B and 2B, and will typically be exerted manually.

25 Figure 4(a) illustrates the arrangement as second magnetic element 2 approaches the first magnetic element 1 from above. This spatial arrangement may be described as a "full separation" of the two elements, when there is sufficient 30 distance between the two to make any magnetic forces negligible. Figure 4(b) illustrates the relative positions of elements 1 and 2 at a slightly closer degree of 35 approach of magnetic element 2. This position is

- 11 described as "partial separation" of the two elements. As element 2 approaches element 1 there is 5 repulsion between the like magnetic poles at the first ends of the first and second magnetic elements 1,2 which, arbitrarily, are both North poles in the Figure. The like poles could equally both be South poles for the same effect to be achieved.

During this time at which like poles are in close proximity, there will be a net repulsive magnetic force acting between the two magnetic elements 1,2. This net repulsive force must be 15 overcome before the two elements 1,2 can approach more closely to a position in which the net attractive magnetic forces dominate, acting to engage the two elements 1, 2 fully. This net repulsive magnetic force provides a resisting effect 20 to the motion of the moving part to which the second magnetic element 2 is affixed. Consumers generally prefer the feel of this sort of damped action.

Together with the pad 3 of interface material to reduce noise, these features help to provide a 25 quiet, controlled closing action and avoid slamming.

Figure 4(c) represents the positions of the magnetic elements 1,2 when there is no net magnetic force exerted on second magnetic element 2. This 30 position is described as the "neutral point".

Usually, this point will be achieved when second magnetic element 2 is substantially half way into aperture 5.

35 Figure 4(d) represents a closer still degree of

- 12 approach of the magnetic elements 1,2 such that they are in "partial engagement". It may be seen that second magnetic element 2 is now significantly inserted into the aperture 5.

Further engagement is now facilitated by the magnetic attraction between the North pole at the first end of element 2 and the opposing South pole of element 1, and also between the South pole at the 10 second end of element 2 and the opposing North pole of magnetic element 1.

Figure 4(e) shows "full engagement" of the magnetic elements 1,2. In this position, the 15 magnetic element 2 abutts the plate 1A of magnetic element 1 and, optionally, the two surfaces may sandwich interface material 3.

Magnetic attractive forces hold the two 20 elements in engagement. Accidental disengagement is hindered by this, and also by the fact that to achieve disengagement, the North pole of magnetic element 2 must pass the North pole of magnetic-

element 1 and overcome the repulsive force 25 therebetween. This repulsive force acts to resist movement of magnetic element 2 out of aperture 5.

Thus the device of the present invention is particularly suitable for applications which experience forces tending to cause disengagement 30 e. g. for containers in vehicles which are subject to such forces when cornering or during rapid change of speed. It will be apparent to those skilled in the art 35 that various modifications and variations may be

- 13 made to the magnetic retaining device without departing from the scope of the invention as set out in the claims.

Claims

- 14 Claims:

1. A magnetic retaining device comprising first and second magnetic elements movable between 5 engaged and disengaged positions, wherein: the first magnetic element defines an aperture having an entrance and an opposing end, there being a magnetic pole adjacent the entrance and a second, unlike magnetic pole adjacent the end; 10 the second magnetic element has a pair of unlike magnetic poles; in the engaged position, the second magnetic element is received in the aperture such that the magnetic poles of the first magnetic element are 15 adjacent the respective unlike poles of the second magnetic element; and in order to move into or out of the engaged position, a magnetic pole of the second magnetic element must pass in close proximity to a like 20 magnetic pole of the first magnetic element.

2. A magnetic retaining device as claimed in claim 1, wherein the first and/or second magnetic elements is or comprises a permanent magnet.

3. A magnetic retaining device as claimed in claim 2, wherein the first magnetic element is annular. 30

4. A magnetic retaining device as claimed in claim 2, wherein the first magnetic element comprises two permanent magnets spaced apart to define an aperture therebetween.

35

5. A magnetic retaining device as claimed in

- 15 any one of the preceding claims, wherein a plate or member is located at each end of the first magnetic element. 5

6. A magnetic retaining device as claimed in any one of the preceding claims, wherein a plate or member is located at each end of the second magnetic element. 10

7. A magnetic retaining device as claimed in claim 5 or claim 6, wherein a plate or member located at the end of the first magnetic element constituting the entrance of the aperture is annular.

8. A magnetic retaining device as claimed in any one of claims 5 to 7, wherein the plate or member comprises a ferromagnetic material.

20

9. A magnetic retaining device as claimed in claim 8, wherein the ferromagnetic material is or comprises ferrous steel.

10. A magnetic retaining device as claimed in 25 any one of the preceding claims, wherein, in the engaged position, an interface material is present between the first and second magnetic elements.

11. A magnetic retaining device as claimed in 30 claim 10, wherein the interface material comprises a compliant material.

12. A magnetic retaining device as claimed in claim 11, wherein the compliant material comprises 35 rubber, plastic, or a fabric.

- 16

13. A magnetic retaining device as claimed in any one of claims 2 to 12, wherein the permanent magnet comprises a rare earth or non-rare earth magnet.

14. A closable container having a magnetic retaining device as defined by any one of claims 1 to 13.

10

15. A magnetic retaining device substantially as herein described with reference to any one of Figures 1 to 4.