IES990305A2

IES990305A2 - A compound magnet

Info

Publication number: IES990305A2
Authority: IE
Inventors: David Patrick Hurley; John Michael David Coey
Original assignee: Magnetic Solutions Holdings Lt
Priority date: 1999-04-13
Filing date: 1999-04-13
Publication date: 2000-11-15
Also published as: WO2000062313A1; AU3668100A

Abstract

A compound magnet comprising a carrier ring (2) which defines a plurality of magnet receiving segments (9) within which permanent magnets (10) are located in side by side and end to end abutting relationship. The magnets (10) are magnetised in a direction of magnetisation B extending parallel to their abutting sides (14) and perpendicular to their ends (15). The magnets (10) are arranged in the segments (9) with the directions of magnetisation of the permanent magnets (10) parallel to each other, and form a direction of magnetisation B of the segments (9) which in turn is parallel to direction of magnetisation of the magnets (10). The direction of magnetisation B of the segments (9) is such as to generate a uni-directional concentrated magnetic field A which extends diametrically across and through the centre of the carrier ring (2). <Figures 1 and 4>

Description

The present invention relates to a compound magnet, and in particular to a compound magnet of the type comprising a plurality of magnets located side by side so that the combined magnetic fields of the magnets defines a predetermined magnetic field. Such compound magnets may be ring magnets and the like. The magnets making up the compound magnet may be provided by permanent magnets, electro magnets or any other suitable magnets.

Ring magnets, whether of circular, square, rectangular or other shape are commonly used to provide a relatively strong uni-directional magnetic field. The ring magnet in general is formed by a plurality of 15 discrete magnets which are arranged in a carrier ring so that the individual magnetic fields of the magnets which make up the ring combine to form a concentrated uni-directional magnetic field extending diametrically .. across the ring, typically through the centre of the ring. However, in order to arrange the magnets of the ring such that the combined effect of their respective magnetic fields acts to form a concentrated unidirectional magnetic field, the magnets have to be secured in the carrier ring with their respective directions of magnetisation appropriately arranged. ι.μιμλμμγ.;· - ¾ Ul nm m, ,, _ (NT f Ί-) 02 j z Γ z o rs so 200 TJ m z F - -1 Ό z C 9 * e □ · d e 1 9 Z CD ” Γ ’ b ?! Π . Ί z? 2 5(/: ί fe* “G • X. • CJ c o z IE 990305 This, in general, requires that the magnets be arranged in the carrier ring such that components of magnetic fields of adjacent magnets act against each other to the extent that the repulsive magnetic forces between adjacent magnets may be so high as to cause the carrier ring to fracture.

There is therefore a need for a compound magnet which overcomes these problems.

The present invention is directed towards providing such a compound magnet.

According to the invention, there is provided a compound magnet comprising a magnet carrier haviiig a plurality of spaced apart discrete magnet retaining segments, each segment carrying a plurality of parallel-sided magnets, the directions of magnetisation of which are similar and parallel, the respective magnets being arranged in side by side abutting relationship within the respective segments, and the magnetic fields of the magnets extending parallel to the abutting sides of the respective magnets.

In one embodiment of the invention the magnets of each segment are arranged in end to end abutting relationship .

IE 990305 In one embodiment of the invention, the direction of magnetisation of each magnet extends perpendicularly to respective abutting ends of the magnets.

In one embodiment of the invention, the compound magnet 5 is a ring magnet, and the magnet carrier comprises a ring carrier. Preferably, the magnets in the respective segments are arranged with their direction of magnetisation being such that the combined magnetic field generated by the magnets defines a predetermined magnetic field.

In one embodiment of the invention, the predetermined magnetic field is a relatively concentrated unidirectional magnetic field, and ideally, acts diametrically across the carrier ring, and preferably, through the centre of the carrier ring.

In one embodiment of the invention, the direction of magnetisation of the magnets in each discrete magnet retaining segment is different to the direction of magnetisation of the magnets in each adjacent segment.

In one embodiment of the invention, the magnets are permanent magnets .

The invention will be more clearly understood from the IE 990305 following description of an embodiment thereof, which is given by way of example only, with reference to the accompanying drawings, in which: Fig. 1 is a plan view of a compound magnet according to the invention with a portion of the compound magnet removed, Fig. 2 is an end elevational view of the compound magnet of Fig. 1, Figs. 3(a) and (b) illustrate the arrangement of magnets in the compound magnet of Fig. 1, Fig. 4 is a plan view of a portion of the compound magnet of Fig. 1, and Fig. 5 is an end elevational view of the portion of Fig. 4 of the compound magnet of Fig. 1.

Referring to the drawings, there is illustrated a compound magnet, in this embodiment of the invention a compound ring magnet 1 for generating a relatively concentrated uni-directional diametrically extending magnetic field which is indicated by the arrows A. The ring magnet 1 comprises a carrier ring 2 of magnetic grade stainless steel having a bottom ring plate 4. A IE 990305 plurality of T-shaped units 5 are secured to the bottom ring plate 4 and inner plates 6 secured to centre legs 7 of the T-shaped units 5 define a plurality of spaced apart discrete magnet retaining segments 9 within which pluralities of permanent magnets 10 are located, see Fig. 3. A plurality of top plates 12 secured to the Tshaped units 5 close the magnet retaining segments 9.

At least some of the magnets 10 are parallel-sided magnets having parallel sides 14 and parallel ends 15 and are arranged in the segments 9 in side by side and end to end abutting relationship. Most importantly, the direction of magnetisation of each magnet 10 is parallel to its parallel sides 14, and perpendicular to its ends 15. Thus, the direction of magnetisation of the magnets 10 in each segment 9 are in the same direction and parallel to each other. However, the magnets 10 in adjacent segments 9 are arranged such that the direction of magnetisation of the magnets 10 of each segment 9 is different to the direction of magnetisation of the magnets 10 of the adjacent segments 9 for directing the magnetic field through the ring and forming the uni-directional concentrated magnetic field A. The directions of the magnetic fields of the permanent magnets 10 in the respective segments 10 is illustrated by the arrows B.

IE 990305 It has been found that by arranging the magnetics 10 in the respective segments 9 with their magnetic fields extending in the same direction and parallel to each other and most importantly parallel to the abutting sides 14 of the magnets 10, the repulsive forces acting between the adjacent magnets 10 within each segment 9 is minimised.

The magnets 10 may be of any suitable hard magnetic material, for example, Nd-Fe-B, Sm-Co, Sm-Fe-N, alnico, MnAl, Pt-Co, Ba-Fe-O, Sr-Fe-O. In the present embodiment of the invention, the diameter of the ring magnet 1 is 0.6 metres, and is suitable for providing a concentrated uni-directional diametrical magnetic field of strength in the order of 1 millitesla to 2 teslas.

While the permanent magnets have been described as being of a specific type, it will be readily apparent to those skilled in the art that the permanent magnets may be of any suitable type and material. Indeed, it will also be appreciated that in certain cases the magnets may not be permanent magnets, but rather may be electro magnets or other suitable magnets.

The invention is not limited to the embodiment hereinbefore described which may be varied in construction and detail.

Claims

1. A compound magnet comprising a magnet carrier having a plurality of spaced apart discrete magnet retaining segments, each segment carrying a plurality of parallel-sided magnets, the directions of magnetisation of which are similar and 5 parallel, the respective magnets being arranged in side by side abutting relationship within the respective segments, and the magnetic fields of the magnets extending parallel to the abutting sides of the respective magnets.

2. A compound magnet as claimed in Claim 1 in which the magnets of each io segment are arranged in end to end abutting relationship.

3. A compound magnet as claimed in Claim 1 or 2 in which the compound magnet is a ring magnet, and the magnet carrier comprises a ring carrier, the magnets in the respective segments are arranged with their direction of 15 magnetisation being such that the combined magnetic field generated by the magnets defines a predetermined magnetic field.

4. A compound magnet as claimed in Claim 3 in which the predetermined magnetic field is a relatively concentrated uni-directional magnetic field, and acts 20 diametrically across the earner ring.

5. A compound magnet substantially as described herein with reference to and as illustrated in the accompanying drawings.