GB2057590A

GB2057590A - Magnetic Balancing of Bearings

Info

Publication number: GB2057590A
Application number: GB8013110A
Authority: GB
Original assignee: United Gas Industries Ltd
Current assignee: United Gas Industries Ltd
Priority date: 1979-07-02
Filing date: 1980-04-22
Publication date: 1981-04-01
Also published as: GB2057590B

Abstract

A vertical axis turbine rotor 11, intended particularly for measuring low gas flows, is mounted on a fairing 15 through low friction bearing 19 on a stationary spindle, and an upper pair of magnets 22, 20 having facing south poles are secured one to the rotor and the other to the fairlng and a similarly secured lower pair of magnets 21, 23 have facing north poles. The rotor, having a limited freedom to move up and down on the spindle, tends to move to a position in which the various vertical forces, e.g. its weight, the repelling forces between the magnets and upward thrust from flowing gas, cancel one another out. This reduces the pressure on the bearing and thereby the frictional resistance to rotation. <IMAGE>

Description

SPECIFICATION Magnetic Balancing This invention relates to magnetic balancing arrangements, particularly for reducing frictional forces in bearings.

The invention provides a magnetic balancing arrangement comprising a member rotatable about a normally vertical axis relative to fixed structure carrying bearing means for said member, an upper pair of magnet means one mounted on the rotatable member and the other on the fixed structure, said magnet means having adjacent pole faces of like polarity spaced normally vertically apart, and a lower pair of magnet means one mounted on the rotatable member and the other on the fixed structure, said lower pair of magnet means also having adjacent pole faces of like polarity spaced normally vertically apart, whereby the weight of the rotatable member is wholly or partially supported by repelling force between one or other of said pairs of magnetic means.

Since the like poles repel one another, the repelling forces between the lower pair of poles tends to support the weight of the rotatable member so relieving the bearing of the frictional force due to said weight.

The rotatable member may carry blades whereby it is rotated by the movement of a fluid.

According to another aspect, the invention provides an axial turbine type gas meter having a rotor carrying blades which may be moved by flowing gas, the rotor being supported by a magnetic balancing arrangement as described above.

Specific embodiments of the invention are shown in the accompanying drawings, in which.

Figure 1 is a section through a gas meter having a rotor balancing arrangement, Figure 2 is a diagrammatic representation of an alternative balancing arrangement for use in another gas meter, and Figure 3 is a diagrammatic representation of another alternative balancing arrangement.

Referring first to Figure 1, the axial turbine type gas meter shown is intended to be mounted inline in a gas which is flowing vertically upwardly in the direction shown by arrow A. The meter has a lightweight rotor 11 with spiral blades 12 extending into an annular gas flow path,1 4. The rotor is mounted in a steamlined fairing 1 5 which operates both to direct the gas flow into the annular path and to mount the rotor. The fairing 1 5 is secured in an outer housing 1 6 by brackets 1 7. Gas flowing through the annulus 1 6 causes the rotor to turn at a speed related to thevolume of gas flowing. The rotations of the rotor are measured by an electronic pick-off (not shown) and the gas flow calculated therefrom.

In order to measure low gas flows the rotor is made lightweight, e.g. is a hollow construction of a plastics material. The rotor rotates on a fixed spindle 18, the ends of which are secured in the fairing 15, and has limited freedom for movement along said spindle. Bearings 19 having bearing surfaces of sapphire or P.T.F.E. are secured to the spindle to provide very low frictional resistance to the rotation of the rotor. Resistance is reduced further by balancing the weight of the rotor through magnets. The rotor carries an annular magnet 20 on its upper side and another annular magnet 21 on its lower side. The fairing carries a stationary annular magnet 22 adjacent upper rotating magnet 20 and another stationary annular magnet 23 adjacent lower rotating magnet 21.The adjacent pole faces of the upper pair of magnets 22 and 20 are of south polarity, while the adjacent pole faces of the lower pair of magnets 21 and 23 are of north polarity.

The effect of the four magnets is to balance the weight of the rotor and also to act as a forward thrust bearing. Because like poles repel one another the two upper poles are mutually repellant and the two lower poles are mutually repeliant. The rotor when stationary takes up a balanced position on the spindle in which the upward thrust on the rotor from the two lower magnets is equal to the sum of the downward thrust on the rotor from the two upper magnets plus the weight of the rotor. When the rotor is subjected to gas flow, the gas pressure produces an increased upward thrust on the rotor producing an unbalance. The consequent upward movement of the rotor on the spindle, however, moves the magnet 20 closer to magnet 22, and so increases the downward repelling force until it counteractsthe extra upward thrust.The rotor therefore regains its balance, with only minimum pressure on the bearings 19. Resistance to rotation remains therefore very low. By this means the rotor adjusts its position over a range of gas flows to cancel out the increased forward thrusts.

It will be noted that there is a similarity between the increase in forward thrust with increased gas flows and the increase in magnetic repelling force as the rotor is moved closer to the upper magnets. Both forces increase on a square law. Therefore, as gas flows increase the force balance can be maintained.

The magnetic balancing arrangement of Figure 2 replaces the two magnets 20,21 with a single two-poled magnet 30 mounted on a rotor 31.

Otherwise the fixed magnets 32 are similar to those of Figure 1.

In the Figure 3 arrangement, a spindle 40 is secured to the rotor (not shown) to rotate therewith and is carried in bearings 41 in recesses in fairing 42. Magnets 43 and 44 are secured to the spindle either side of the rotor and co-operate in similar manner to that described in relation to Figure 1, with fixed magnets 45, 46.

Although the magnetic balancing arrangement has been described hereinbefore with reference to a gas meter, it could be used in other rotating machinery using vertical axes.

Claims

1. A magnetic balancing arrangement cornprising a member rotatable about a normally vertical axis relative to fixed structure carrying bearing means for said member, an upper pair of magnet means one mounted on the rotatable member and the other on the fixed structure sold magnet means having adjacent pole faces of like polarity spaced normally vertically apart, and a lower pair of magnet means one mounted on the rotatable member and the other on the fixed structure, said lower pair of magnet means also having adjacent pole faces of lilse polarity spaced normallv vertcally apart, whereby the weight of the rotatable member is wholly or partially supported by repelling force between one or ether of said pairs of magnetis means.

2. A megnetic balancing errangement as clsimed in claim 1 wherein said upper pair of poies is of one polarity and the lower pair is of opposite polarity.

3. A magnetic balancing arrangement as claimed in claim 2, Wherein said rotatable member has limited freedom for ventical movement relative to said fixed structure whereby it tends to take up a position in Which the magnetic forces between the magnet meansm, its Weight and other pressures thereon are vertically balanced.

4. A magnetlc balaneing arrangement as claimed in clain 3,wheroin snid rotatabie member carries one magnet of said upper pair i of magnetic means on its upper surface facing the other of said upper pair mounted on the fixed structure immediately abous it, and one magnet of said lower pair of magnet means on Its lower surface facing the other of said lower pair mounted on the fixed structure immediately below it.

5. A magnetic balancing arragement as claimed in clairn 4, wherein said rotatable member rotates in bearing means on a normally vertical spindle which passes through holes in the pairs of magnet means and is mounted in the stationary strueture.

6. A magnetic balancing arrangement as claimed in claim 3, wherein a lower magnet o the upper pair and an upper magnet of the lower pair are combined into one eiongated magnet.

7. A magnetic balancing arrangement as claimed in claim 4, Wherin said rotatable member inchudes a spindle rotatable about a normally vertical axis in bearing mounted in the stationary structure, said spindle passing through holes in the pairs of magnet means.

8. A magnetic balancing arrannement substantially as set forth hereinbefore With reference to Figure 1 or Figure 2 or Figure 3 of the accompanying dravbings.

9. A gas meter substantially as described hereinbefore with reference to Figure 1 or to that Figure as modifled tey reference to figure 2 or do figure 3 of the accompanying drawngs.