GB2222915A - Magnetic devices to assist movement of a component - Google Patents

Abstract

A magnetic device comprises a disc (2) mounted for rotation in one direction only relative to a support or framework (1), the support (1) having a pair of magnets (12, 13) fixed to it, the magnetic fields of which interact with magnetic fields produced by magnets 7, 8 which form a magnet unit (6), the plurality of units being spaced apart and mounted pivotally by pins 11 on the disc (2). Magnetic repulsive forces are produced due to the magnetic fields being of the same polarity, the strength of which is related to the position of magnets 12, 13 and the separation between magnets 7, 8. These forces cause a movement of the disc. <IMAGE>

Description

MAGNETIC DEVICES This invention relate; i a,ti;nziic devices.

It is well known that magnets having opposite polarities attract each other, and that magnets having the same polarities, repel eaci other.

It is an object of the invention to provide a magnetic device which produces movement due to magnetic repulsion.

According to the present invention, there is provided a magnetic device comprising a support, a plate arranged for movement with respect to the sot, at least one magnet unit containing two magnets at a distance from one another and the magnet unit(s) being on and carried by the plate, the or each magnet unit being relatively movable wit respect to the plate, and at least one pair of two magnets fixed with respect to the support and arranged to interact with magnetic fields produced by the or each magnet unit to produce movement of the plate, the strengths, extent and positions of the or each pair of two fixed magnets and the strengths, extent and positions of the magnets forming the magnet unit(s) being such that the strength of interaction in the direction of relative movement between one of the two fixed magnets o a pair of fixed magnets and one of the magnets of a magnet unit is greater han the strength of interaction between the other magnet of the pair of two fixed magnets and the other magnet of the magnet unit.

Advantageously, each magnet unit comprises a pair of magnets spaced apart by an arm, the arm passing through an aperture in the plate and is pivotally connected thereto.

The arm is pivoted at a point such that the ratio of distances between each magnet and the pivot is less than one. In ore? embodiment, the ratio is half.

The present invention may have application In an arrangement where linear motion is desired. However, in one particular embodiment of the invention, the desired motion is circular. In such an embodiment, the plate is a disc mounted for rotation on a spindle, and magnet units are eluispaced around the disc at a given radial distance from the spindle. The disc may have twenty-four magnet units arranged on it.

Each magnet may be a permanent magnet, and each magnetic field can be shaped by mild steel t soCt iron pole pieces attached to the magnet.

At least one magnet may b an electromagnet.

For a better understanding of the present invention, reference will now be made by way of example only to the accompanying drawings in which: Figure 1 is a schematic plan view of a magnetic device according to the invention, and ire 2 is a sectional view along the lines II-II of Figure 1.

A magnetic device is illustrated in the figures. The device comprises a support or outer framework 1 and a disc 2 rigidly mounted on a spindle 3. The framework 1 supports the spindle 3 and disc 2 for rotation about their axes by means of a pair of bearings 4, 5 positioned one at either end of the spindle 3.

Tvlenty-four magnet units 6 are attached to the disc 2.

Each magnet unit 6 comprises two magnets 7 and 8 spaced apart by an arm 9. Each arm 9 passes through an aperture 10 formed in the disc 2 and is pivotally attached on the disc 2 by means of a pivot 11. The pivot 11 divides the arm in a fixed ratio, for example a ratio of approximately 1:2 as shown in figure 2.

The arm 9 hangs in a vertical plane transverse to the plane of the di- 2 a, shown in Figure 2 due to the effects of gravity. When the arm 9 pivots about pivot 11 the magnets 8 and 7 move inwards and outwards in a generally radial direction relative to the disc 2.

A pair of two further magnets 12 and 13 are rigidly attached to the framework 1. These fixed magnets are spaced from one another in a circumferential direction and also in a vertical direction as shown in Figure 2. These magnets 12, 13 are sufficiently close to one another that the magnetic fields produced by each magnet can interact with respective ones of the magnetic fields produced by magnets 8 and 7 of magnet unit 6 at the same time.

In the device illustrated, the disc 2 is caused to rotate about its axis due to forces generated by magnetic repulsion. This repulsion is produced by the interaction of magnetic fields having the same polarity, that is facing poles of magnets 7, 13 and 8, 12 are the same. All the facing poles of the magnets may have the same polarity, for example being all north or all south poles.

Alternatively, the facing poles of magnets 7 and 13 may be of one polarity, and of magnets 8 and 12 of the opposite polarity.

The interaction between the pairs of magnets 7, 13 and 8, 12 is such that the repulsive forces generated by the interaction between magnets 8 and 12 is weaker than the interaction between magnets 7 and 13. However, the arm 9 is divided in a fixed ratio as mentioned above, and this ratio enables the weaker interaction between magnets 8 and 12 to overcome the stronger interaction between magnets 7 and 13.

A dog clutch (not shown) is fixed to the spindle 3 and is used to prevent rotation of the disc 2 in a direction other than a desired direction, for example in a clockwise direction as shown by arrow 14 in Figure 1.

When the disc 2 is positioned relative to the framework 1 such that one of the magnets 8 of a magnet unit 6 is brought near to the fixed magnet 12, a repulsive force is generated as magnets 8 and 12 are of the same polarity.

This repulsive force has a radial component acting towards the centre of the disc 2 and a tangential component acting at a tangent to the periphery of the disc 2 tending to cause the disc 2 to rotate in an anticlockwise direction but this is prevented by the presence of the dog clutch as mentioned previously. The radial component of the repulsive force makes magnet 8 move away from the magnet 12 in a radially inward and upward direction and causes the magnet unit 6 to rotate about the pivot 11. The aperture 10 in which the arm 9 is located is of sufficient size to allow such movement. As a consequence of the rotation about pivot 11, magnet 7 is caused to move in a radially outward and downward direction towards the framework 1.

At the same time as the magnet 7 is moved towards the framework 1, the magnetic field of magnet 7 is made to interact with the magnetic field of magnet 13 fixed to the framework 1. Because both magnets 7 and 13 are of the same polarity, a repulsive force is generated due to this interaction. This repulsive force has a tangential component and a radial component, the tangential component causing the disc 2 and spindle 3 to rotate about their axes. The radial component of the repulsive force is overcome by the radial component of the interaction between magnets 8 and 12 as a result of the fixed ratio division of the arm 9. The tangential component of the repulsive force moves the disc 2 in a clockwise direction bringing an adjacent magnet unit 6 towards the fixed magnets 12 and 13. When the disc 2 is moved further, the operation of a magnet unit 6 as described above can be repeated, that is, when a magnet 8 of the adjacent magnet unit 6 is brought sufficiently near to the fixed magnet 12.

After a magnet unit 6 has passed the fixed magnets 12 and 13, the arm 9 returns to its vertical position as mentioned above, from which position the magnet unit 6 can again interact with the fixed magnets 12 and 13.

Each of the magnets 7, 8, 12 and 13 is chosen to produce a magnetic field of sufficient strength to generate the repulsive forces which are required to cause the magnet unit 6 to rotate about pivot 11 and the disc 2 to rotate about its axis.

The magnetic fields produced may be shaped by fixing mild steel pieces or soft iron pieces to the magnets themselves.

It is desirable to make the magnet units move mainly under magnetic rather than gravitational forces. In order to minimise the role of gravitational forces, the magnet unit may have a spring at the pivot to offset the generally greater weight of the longer lower section of arm 9 below the pivot, or the arm 9 may be e.g. of greater cross section above the pivot such that the centre of gravity o the magnet unit is only just below the pivot. Also, it is desirable to avoid oscillation by damping the pivot by appropriate means.

In the illustrated case, the distance between the magnet 8 and the pivot 11 is twice the distance between the magnet 7 and the pivot 11. Therefore, the amount of movement of magnet 8 towards the centre of the disc 2 due to the radial component of the repulsive force generated between magnets 3 and 12 will cause magnet 7 to move a distance half that moved by magnet 8. Other ratios for dividing the arm 9 may also be possible.

Because of the smaller movement of magnet 7 in relation to the movement of magnet 8 of the magnet unit 6, magnetic fields utilised within the described embodiment of the invention are shaped to compensate for this smaller movement.

Naturally, careful consideration must be given to relationships between components for a particular embodiment of the invention, for example the extent of the magnetic fields produced by magnet units 6 and fixed magnets 12, 13, the fixed ratio division of the arm 9, and the energy required of magnetic repulsion to cause relative movement of a magnetic unit. Also, if the embodiment has a plurality of magnet units or of pairs of fixed magnets, they should be sufficiently spaced not adversely to interfere with one another functioning. Instead of a single arm connecting the two magnets 7 and 8, each magnet could be carried by a separate arm which is connected for relative movement with respect to the other arm. In such an arrangement, simple or complex gears may be used to provide the relative movement.

Although magnets 12 and 13 are fixed to the framework 1 at the periphery of disc 2 in the illustrated embodiment, at least one of these magnets could be positioned adjacent spindle 3 either above or below the plane in which the disc 2 rotates.

Although twenty-four magnet units are illustrated in the described embodiment, a different number of magnet units can be employed.

The magnets described may be permanent magnets, electromagnets or hybrid magnets. Depending on the specific embodiment, some magnets may be permanent magnets, for example those forming magnet unit 6 and others electromagnets, for example, magnets 12 and 13.

In the described embodiment, one pair of fixed magnets 12, 13 are utilised. However, if necessary, further pairs of fixed magnets can be used. Any further pairs of fixed magnets may be arranged to be equispaced around the framework 1.

A magnetic device according to the invention may be used to assist the movement of a moveable component in its defined path of travel.

Claims (12)

1. A magnetic device comprising a support, a plate arranged for movement with respect to the support, at least one magnet unit containing two magnets at a distance from one another and the magnet unit(s) being on and carried by the plate, the or each magnet unit being relatively movable with respect to the plate, and at least one pair of two magnets fixed with respect to the support and arranged to interact with magnetic fields produced by the or each magnet unit to produce movement of the plate, the strengths, extent and positions of the or each pair of two fixed magnets and the strengths, extent and positions of the magnets forming the magnet unit(s) being such that the strength of interaction in the direction of relative movement between one of the two fixed magnets of a pair of fixed magnets and one of the magnets of a magnet unit is greater than the strength of interaction between the other magnet of the pair of two fixed magnets and the other magnet of the magnet unit.

2. A device according to Claim 1, wherein each magnet unit comprises a pair of magnets spaced apart by an arm, the arm passing through an aperture in the plate and is pivotally connected thereto.

3. A device according to Claim 2, wherein the arm is pivoted at a point suc that the ratio of distances between each magnet and the pivot is less than one.

4. A device according to any one of Claims 1 to 3, wherein the plate is a disc mounted for rotation on a spindle.

5. A device according to Claim 4 and including a plurality of magnet units equispaced around the disc at a given radial distance from the spindle.

6. A device according to Claim 4 or 5, wherein twenty-four magnet units are utilised.

7. A device according to any one of the preceding claims, wherein each magnet is a permanent magnet.

8. A device according to any one of the preceding claims and including means attached to one or more of the magnets to shape the magnetic field thereof.

9. A device according to Claim 8 wherein the means for shaping the magnetic field is mild steel or soft iron pole pieces attached to the magnet.

10. A device according to any one of Claims 1 to 7, wherein at least one magnet is an electromagnet or a hybrid magnet.

11. A device according to any one of Claims 1 to 10 wherein the magnets of the magnet unit(s) are permanent magnets.

12. A magnetic device substantially as hereinbefore described with reference to the accompanying drawings.