WO2019021187A1

WO2019021187A1 - Permanent magnet coupling

Info

Publication number: WO2019021187A1
Application number: PCT/IB2018/055514
Authority: WO
Inventors: Jacques Henri Smit
Original assignee: Jacques Henri Smit
Priority date: 2017-07-24
Filing date: 2018-07-24
Publication date: 2019-01-31

Abstract

A permanent magnet coupling (11) is disclosed, the coupling being adapted for use in a drive system between a drive member (12) and a driven member (14). The coupling comprising: at least one paramagnetic conductor (16) having a first side and a second side, opposing the first side, the at least one paramagnetic conductor being sandwiched between, or flanked by, magnetic rotor assemblies (18, 20) so that a first magnetic rotor assembly faces the first side and a second magnetic rotor assembly faces the second side, each magnetic rotor assembly having at least two permanent magnets (22, 26) so disposed within the respective magnetic rotor assemblies to ensure permanent magnets with opposing the same or repelling poles are positioned on opposite sides of the at least one paramagnetic conductor to create a magnetic field through which the at least one paramagnetic conductor can move. The invention extends to a method of using said coupling.

Description

PERMANENT MAGNET COUPLING

THIS INVENTION relates to torque transfer. More particularly the invention relates to a permanent magnet coupling adapted to transmit torque from a motor to a load across an air gap. The invention extends to a drive system including the permanent magnet coupling of the invention. The invention further extends to a method of actuating a drive system having the permanent magnet coupling of the invention disposed between a drive member and a driven member.

BACKGROUND TO THE INVENTION

Torque is a measure of the turning force on an object. In drive systems, the object may be a rotor (or so-called load shaft) of a load such as, for example, a pump, fan, conveyor, compressor, mixer, crusher, mill and the like. The rotor is typically rotatably connected via a suitable coupling to an input shaft of a prime mover, such as a motor or internal combustion engine adapted to rotate the rotor.

Several types of shaft-to-shaft couplings are used in industry as part of rotating drive systems for different application requirements.

There are two drive-driven arrangements or configurations. In the first type, the drive and driven components rotate at the same speed and the second where the drive and driven components rotate at different speeds.

Flexible couplings commonly provide strong, durable prime mover to load connection and are apt to sufficiently connect two shafts which run out of line. The flexible couplings also operate to take up shocks and vibrations and prevent them from being transmitted from one shaft or rotatable member to the other.

Where the drive and driven components are required to rotate at different speeds reducers, commonly known as gearboxes, are introduced, requiring different types of couplings. A common drive system coupling utilizes flow of a hydraulic fluid to transmit rotating mechanical torque from an input shaft of a prime mover to a rotor or load shaft. Hydrodynamic fluid couplings require a hydraulic fluid which poses environmental hazards. A water filled coupling was recently introduced. The drive and driven shafts in a fluid coupling are not mechanically connected.

The development of the permanent magnet coupling was a step forward in technology as it provided efficient torque transfer between a prime mover and a rotor of a load, by utilization of magnetism. There are two permanent magnet coupling configurations namely axial and radial.

All types of magnets can be used in permanent magnet couplings, hard ferrite, SmCo type, Alnico, NdFeB type rare earth and new printed magnets. The permanent magnet coupling generally use high power Neodymium-lron-Boron permanent magnets to create an induced magnetic force in a diamagnetic material used for torque transfer from the prime mover to the load. Torque transmission occurs between a radial or axial array of permanent magnets arranged in a rotor attached to the one shaft and an opposing diamagnetic conductor disk or drum, usually copper or aluminium, attached to the second shaft. There is an air gap between the magnet rotor and the conductor. The magnets in the array have alternating poles facing the copper conductor.

The magnetic coupling serves the exact same purpose as the traditional fluid coupling and can be a direct drop-in replacement. There are variable speed and delay soft start fluid couplings. The main purpose of the permanent magnet coupling is to allow for a 'soft- start'. The torque transmitted by a traditional permanent magnet coupling can be varied by changing the distance of the air gap between magnets in the prime mover and the conductor. This is generally done to extend the start-up time allowing more slip between the driver and driven shafts. There are benefits to having an air gap in magnetic couplings. Torque transmission occurs across the air gap with no mechanical connection between the prime mover to the rotor of the load. This means that vibration transfer from the prime mover or driving member to the rotor of the load, or driven member, is prevented. With no shaft-to-shaft connection present in a permanent magnet coupling, shock loads can be cushioned and vibration reduced.

Furthermore, in magnetic couplings, precise alignment between the driving member and the driven member is not as critical as compared to other drive system couplings. The magnetic coupling can cope with shaft misalignment of up to 3 degrees whereas the fluid coupling requires a bearing on each opposing shaft. The magnetic coupling also has the benefit of not having any bearings or other wear parts. However, the applicant believes that existing permanent magnet couplings, and drive systems using same, do leave scope for improvement in torque transmitting efficiency.

As such, it would be advantageous to introduce a torque transferring permanent magnet coupling designed to: obtain a practically perfect dynamic balance when used in a drive system; be durable and practically immune from disorder after proper installation; require no lubrication; have a high torque transmitting efficiency.

SUMMARY OF THE INVENTION In broad terms and in accordance with an embodiment of the invention there is provided a permanent magnet coupling comprising: at least one paramagnetic conductor having a first side and a second side, opposing the first side, the at least one paramagnetic conductor being sandwiched between, or flanked by, magnetic rotor assemblies so that a first magnetic rotor assembly faces the first side and a second magnetic rotor assembly faces the second side, each magnetic rotor assembly having at least two permanent magnets so disposed within the respective magnetic rotor assemblies to ensure permanent magnets with the same or repelling poles are positioned on opposite sides of the at least one paramagnetic conductor to create a magnetic field through which the at least one paramagnetic conductor can move.

The invention also provides for an air gap to be provided between the first magnetic rotor assembly and the first side of the at least one paramagnetic conductor; and between the second magnetic rotor assembly and the second side of the same paramagnetic conductor. The invention further provides for a magnetic material metal backing plate to be disposed on the outside of the respective magnetic rotor assemblies to flank said assemblies while the at least one paramagnetic conductor is sandwiched between said assemblies.

The respective magnetic rotor assemblies may be connected and adapted to rotate together.

The flanking magnetic material metal backing plates may be connected to each other by a magnetic material metal spacer extending between a first permanent magnet rotor assembly end and a second permanent magnet rotor assembly end, which spacer assists in creation of an electromagnetic field that extends across the at least one paramagnetic conductor and links south and north poles of the two or more flanking magnetic rotor assemblies electromagnetically.

In an embodiment of the invention, there is provided for the at least one paramagnetic conductor to be selected from a paramagnetic material such as, for example, copper and aluminium.

The invention also provides for each of the respective magnetic rotor assemblies to comprise a rotor body having at least two apertures therein to snugly locate at least two permanent magnets. The apertures may be disposed in a circular fashion on the rotor body.

In an embodiment of the invention, the permanent magnet coupling comprises multiple paramagnetic conductors, each being sandwiched between, or flanked by, magnetic rotor assemblies with two or more permanent magnets so disposed within the respective magnetic rotor assemblies to ensure permanent magnets with opposing repelling poles are positioned on opposite sides of the paramagnetic conductors to create a magnetic field through which the paramagnetic conductors can move. In accordance with a further aspect of the invention there is provided a drive system including the permanent magnet coupling as described herein before, the permanent magnet coupling being apt for positioning between a driving member and a driven member in the drive system to transfer torque, upon actuation of the driving member, from the driving member to the driven member. In accordance with yet a further aspect of the invention there is provided a magnetic material soft metal backing plate for shielding magnetic flux on opposite sides of the at least one paramagnetic conductor in a permanent magnet coupling and, the soft metal backing plate, in use, being disposed on the outside of respective magnetic rotor assemblies of the permanent magnet coupling to flank said assemblies while at least one paramagnetic conductor is sandwiched between said assemblies. Flanking magnetic material soft metal backing plates may be connected to each other by a magnetic material metal spacer extending between a first magnetic rotor assembly end and a second magnetic rotor assembly end, which spacer assists in creation of an electromagnetic field that extends across the at least one paramagnetic conductor and links south and north poles of the two or more flanking magnetic rotor assemblies electromagnetically.

In accordance with a still further aspect of the invention there is provided a method of actuating a drive system having a drive member and a driven member, the method comprising: positioning a permanent magnet coupling as described herein between the drive member and the driven member; and actuating rotation of the drive member, which may be connected to either a paramagnetic disk conductor of the permanent magnet coupling or to one of the magnetic rotor assemblies of said coupling, to drag along and rotate either said paramagnetic disk conductor of the permanent magnet coupling or one of the magnetic rotor assemblies of said coupling to drive the drive system.

In accordance with a still further aspect of the invention there is provided a method of actuating a drive system having a drive member and a driven member, the method comprising: positioning a permanent magnet coupling between the drive member and the driven member,

which permanent magnet coupling includes:

at least one paramagnetic conductor having a first side and a second side, opposing the first side, the at least one paramagnetic conductor being sandwiched between, or flanked by, magnetic rotor assemblies so that a first magnetic rotor assembly faces the first side and a second magnetic rotor assembly faces the second side, each magnetic rotor assembly having at least two permanent magnets so disposed within the respective magnetic rotor assemblies to ensure permanent magnets with the same or repelling poles are positioned on opposite sides of the at least one paramagnetic conductor to create a magnetic field through which the at least one paramagnetic conductor can move,

so that an air gap is provided between the first magnetic rotor assembly and the first side of the same paramagnetic conductor; and between a second magnetic rotor assembly and a second side of the same paramagnetic conductor; actuating rotation of the drive member, which in turn is connected to the first magnetic rotor assembly; and allowing alternating North and South poles to be created in the at least one paramagnetic conductor which follow the rotation of magnetic rotor assemblies, when either of these magnetic rotor assemblies are driven by the drive member via the air gap defined between the respective magnetic rotor assemblies so that the driven member, connected to the at least one paramagnetic conductor, is dragged along by the induced magnetic fields in the at least one paramagnetic conductor thereby to effect rotation.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention are now described, by way of example, with reference to the accompanying non-limiting diagrammatic drawings. In the drawings:

Figure 1 shows a section view of a drive system (partially shown) including the permanent magnet coupling in accordance with the present invention;

Figure 2 shows a section view of a drive system (partially shown) including the permanent magnet coupling in accordance with a further embodiment of the present invention; and Figure 3 shows a section view of a drive system (partially shown) including the permanent magnet coupling in accordance with yet a further embodiment of the present invention.

DETAILED DESCRIPTION OF THE DRAWINGS

Referring to Figure 1 , reference numeral 10 generally indicates a drive system (partially shown, i.e. without motor and load) and including a permanent magnet coupling 1 1 in accordance with the present invention.

Drive system 10 is presented herein to bring about rotation, which is caused by any suitable driving member 12 such as, for example, an electric motor acting on a load. For convenience, the load herein is referred to as the driven member 14. Similar driving members 1 12, 212 and driven members 1 14,214 are shown and referred to in Figures 2 and 3 as similar, but slightly different embodiments of the same inventive drive system 100, 200 are depicted in Figures 2 and 3. Accordingly, in this description, similar features of the different embodiments of the invention are depicted with like numerals, unless otherwise indicated. As such, the permanent magnet couplings 1 1 1 and 21 1 are similar, but not identical, to permanent magnet coupling 1 1 .

Referring to Figure 1 , both drive system 10 and permanent magnet coupling 1 1 include a paramagnetic disk conductor 16. The disk conductor 1 6 is typically, but not necessarily manufactured from copper. The copper disk conductor 16 is shown to be connected to a rotatable shaft of the driven member 14. The copper disk conductor 16, connected to the driven member or load 14, is intended to be driven and rotated by the driving member 1 2 adjacent thereto. Torque is transmitted from the driving member 1 2 to the driven member 14, via the copper disk 1 6, when the driving member 12 begins to rotate. A small delay in the form of slip between the copper conductor 1 6 and a magnetic rotor assembly 18 is present before rotation of the driving member 12 effects rotation of both the driven member 14 and copper disk 16.

It is envisaged that any other paramagnetic conductor may be utilized and that such paramagnetic conductor and its use are believed to fall within the ambit of the present invention.

Similar disks 1 16 and 21 6 are depicted in Figures 2 and 3. They also function in the same way as disk 1 6 as they are intended to be driven and rotated by the driving member 1 12, 21 2, although same is not physically connected to the driven member 1 14,214.

Although, the driving member 1 2, 1 12, 212 is depicted in the drawings as being the first rotating member with the copper disk 16, 1 1 6, 216 kept initially stationary and only beginning to rotate after lapse of a small delay, it will be appreciated that in other non- shown embodiments of the invention, the copper disk 16, 1 16, 216 may be initially connected to a rotating driving member and not to the driven member such that the driven member, then has a delayed start.

Returning to Figure 1 , the copper disk conductor 16 is disposed between two opposing magnetic rotor assemblies 18,20. The first magnetic rotor assembly 18 defines a first magnetic rotor assembly end 18.1 while an opposingly disposed magnetic rotor assembly 20 defines an opposingly disposed magnetic rotor assembly end 20.1 .

A spacer 50 is provided to connect the ends 18.1 and 20.1 . The spacer 50 is either of uniform construction and integrally formed with magnetic material metal backing plates 52, which backing plates 52 are disposed on the outside of the two opposing magnetic rotor assemblies 18,20. The spacer 50 and backing plates 52 typically consist of a ferromagnetic or ferrimagnetic material such as iron, nickel, or cobalt. The spacer 50 spans across the copper disk conductor 16 and the length thereof is defined between the ends 18.1 and 20.1 . Air gaps 21 are disposed between the first and opposing magnetic rotor assemblies 1 8 and 20 and, therefore, no physical contact exists between the driving member 12 and the driven member 14. As shown in Figures 2 and 3, every paramagnetic conductor or copper disk conductor 1 1 6,216 has a magnetic rotor assembly 1 1 8,120 and 218,220 respectively on either side thereof with the outside rotor assemblies having metal backing plates 152, 252 on the outside. The magnetic metal backing plates 152, 252 are connected to each other by way of spacers 150,250 also made from magnetic metal material. This arrangement with repelling pole magnets on opposite sides of the copper disk conductor 1 1 6,21 6 increases the magnetic flux in which the copper disk conductors 1 1 6,216 operate. The opposing rotor assemblies 1 18,218 and 120,220 are assembled such that same pole magnets face each other, resulting in the opposing rotor assemblies 1 18,218 and 120,220 pushing each other apart.

Again, referring to Figure 1 , four equidistantly spaced apart permanent magnets 22, with alternative poles facing inwards, are located within apertures defined in an aluminium body 24 of the first magnetic rotor assembly 18. Another four identically positioned and equidistantly spaced apart permanent magnets 26 are defined within an aluminium body 28 of the opposingly disposed magnetic rotor assembly 20. The magnets 22 and 26 are facing towards the surface area of the copper disk 16 to create a magnetic force field. The magnets 22 and 26 are so disposed so that repelling magnetic forces are created between the first magnetic rotor assembly 18 and the opposingly disposed magnetic rotor assembly 20, i.e. north poles are positioned to face towards north poles and similarly south poles are positioned to face towards south poles. As a result, an electromagnetic field propagates in a wavelike manner axially along the length of the spacer 50 and across both the copper disk conductor 1 6 and the two magnetic rotor assemblies 18 and 20 to form a smooth, alternating electromagnetic field.

The unique positioning of the copper disk conductor 16,1 16,216 relative to the two flanking magnetic rotor assemblies 18,20 and 1 18,120 and 218;220 is believed to create an electromagnetic field during rotation of the magnetic rotor assemblies 18,20 and 1 1 8,120 and 218;220 relative to the conductor 16,1 16,216; or during rotation of the conductor 16,1 16,21 6 relative to the magnetic rotor assemblies 18,20 and 1 18,120 and 21 8;220. Thereby the resultant force acting on the copper disk conductor 16,1 16,216 is increased.

In use, alternating North and South poles are created in the copper disk conductor 16,1 16,216 which follow the magnetic rotor assemblies 1 8,20 and 1 1 8,120 and 218;220, when either of these magnetic rotor assemblies 1 8,20 and 1 1 8,120 and 218;220 are driven. If the copper disk conductor 1 6,1 16,216 is rotatably driven, the magnetic rotor assemblies 18,20 and 1 18,120 and 218;220 follow (are dragged) by the induced magnetic fields in the copper disk conductor 1 6,1 16,216. As a result, a drive system 1 0, 100, 200 is created having an enhanced permanent magnet coupling 1 1 , 1 1 1 , 21 1 that provides an ideal dynamic balance capable to more efficiently 'drag along' the load. Accordingly, either the paramagnetic disk conductor 16,1 16, 21 6 or one of the magnetic rotor assemblies 18,20 can be rotated first so as to start rotation of the drive system 10, 1 00, 200.

The permanent magnet coupling 1 1 , 1 1 1 , 21 1 is furthermore durable in that way less moving parts are present compared to common couplings, therefore, the coupling 1 1 , 1 1 1 , 21 1 is practically almost immune from disorder as it requires no lubrication and no attention after being properly installed. Test results indicate that torque transmitting efficiency is higher than commonly known magnetic couplings used in drive systems.

There are different types of permanent magnets that can be used in the magnetic couplings ranging from hard ferrite, SmCo type, Ainico, NdFeB type rare earth and new printed magnets. Permanent magnet NdFeB is the most popular type.

Different spatial relationships of the couplings 1 1 1 , 21 1 of the invention, wherein multiplication of copper disks 1 16, 216 are depicted, are shown in Figures 2 and 3. However, Figures 2 and 3 are believed to be not departing from the spirit and scope of the invention. Similarly, it will be appreciated that any method of using the magnetic coupling 1 1 , 1 1 1 , 21 1 of the above described drive system 1 0, 1 10, 21 0 to effect rotation, falls within the ambit of this invention. It is believed that the magnetic dipole moments of the spinning unpaired electrons in the paramagnetic conductor or copper disk conductor 1 6,1 16,21 6 are 'magnetised' to a far greater extent which leads to increased torque transfer across the air gaps. The permanent magnet coupling 1 1 has a greater torque density (by as much as 60%) compared to conventional magnetic couplings.

The applicant believes that use of drive system 10, 1 1 0, 210 or the permanent magnet coupling 1 1 , 1 1 1 , 21 1 , instead of use of conventional drive systems and magnetic couplings, will not only reduce driving member size as smaller inertias will be present, but also increase torque transfer across the air gaps present in a magnetic coupling. The applicant also believes that the invention provides a simple, effective and improved magnetic coupling 11, 111,211 and drive system 10, 110,210. The invention for which patent protection is sought is now defined by way of the appended set of claims.

Claims

1 . A permanent magnet coupling comprising: at least one paramagnetic conductor having a first side and a second side, opposing the first side, the at least one paramagnetic conductor being sandwiched between, or flanked by, magnetic rotor assemblies so that a first magnetic rotor assembly faces the first side and a second magnetic rotor assembly faces the second side, each magnetic rotor assembly having at least two permanent magnets so disposed within the respective magnetic rotor assemblies to ensure permanent magnets with opposing the same or repelling poles are positioned on opposite sides of the at least one paramagnetic conductor to create a magnetic field through which the at least one paramagnetic conductor can move.

2. The permanent magnet coupling of claim 1 , wherein an air gap is provided between the first magnetic rotor assembly and the first side of the at least one paramagnetic conductor; and between the second magnetic rotor assembly and the second side of the same paramagnetic conductor.

3. The permanent magnet coupling of claim 1 , including a magnetic material soft metal backing plate disposed on the outside of the respective magnetic rotor assemblies to flank said assemblies while the at least one paramagnetic conductor is sandwiched between said assemblies.

4. The permanent magnet coupling of claim 1 , wherein the respective magnetic rotor assemblies are connected and adapted to rotate together.

5. The permanent magnet coupling of claim 3 or 4, wherein the flanking magnetic material soft metal backing plates are connected to each other by a magnetic material metal spacer extending between a first permanent magnet rotor assembly end and a second permanent magnet rotor assembly end, which spacer assists in creation of an electromagnetic field that extends across the at least one paramagnetic conductor and links south and north poles of the two or more flanking magnetic rotor assemblies electromagnetically.

6. The permanent magnet coupling of claim 1 , wherein the at least one paramagnetic conductor is manufactured from copper or aluminium.

7. The permanent magnet coupling of claim 1 , wherein each of the respective magnetic rotor assemblies comprise a rotor body having at least two apertures therein to snugly locate at least two permanent magnets.

8. The permanent magnet coupling of claim 7, wherein the apertures are disposed in a circular fashion on the rotor body.

9. The permanent magnet coupling of claim 1 , including multiple paramagnetic conductors, each being sandwiched between, or flanked by, magnetic rotor assemblies with two or more permanent magnets so disposed within the respective magnetic rotor assemblies to ensure permanent magnets with opposing repelling poles are positioned on opposite sides of the paramagnetic conductors to create a magnetic field through which the paramagnetic conductors can move.

10. The permanent magnet coupling of claim 1 , including a magnetic material soft metal backing plate for shielding magnetic flux on opposite sides of the at least one paramagnetic conductor, the soft metal backing plate being disposed on the outside of respective magnetic rotor assemblies of the permanent magnet coupling to flank said assemblies while the at least one paramagnetic conductor is sandwiched between said assemblies.

1 1 . The permanent magnet coupling of claim 5, including a magnetic material metal spacer that extends between a first magnetic rotor assembly end and a second magnetic rotor assembly end to flank respective magnetic rotor assemblies of the permanent magnet coupling and to assists in creation of an electromagnetic field that extends across the at least one paramagnetic conductor and links south and north poles of the two or more flanking magnetic rotor assemblies electromagnetically.

12. A drive system having a driving member and a driven member, the drive system comprising a permanent magnet coupling as claimed in any one of claims 1 to 9, wherein the permanent magnet coupling is positionable between said driving member and said driven member to transfer, upon actuation of the driving member, torque from the driving member to the driven member.

13. A method of actuating a drive system having a drive member and a driven member, the method comprising: positioning a permanent magnet coupling as described herein between the drive member and the driven member; and ubiquitously actuating rotation of the drive member, which may be connected to either a paramagnetic disk conductor of the permanent magnet coupling or to one of the magnetic rotor assemblies of said coupling, to drag along and rotate either said paramagnetic disk conductor of the permanent magnet coupling or one of the magnetic rotor assemblies of said coupling to thereby drive the driven member of the drive system.

14. A method of actuating a drive system having a drive member and a driven member, the method comprising: positioning a permanent magnet coupling between the drive member and the driven member,

which permanent magnet coupling includes:

so that an air gap is provided between the first magnetic rotor assembly and the first side of the same paramagnetic conductor; and between a second magnetic rotor assembly and a second side of the same paramagnetic conductor; actuating rotation of the drive member, which in turn is connected to the first magnetic rotor assembly; allowing alternating North and South poles to be created in the at least one paramagnetic conductor which follow the rotation of magnetic rotor assemblies, when either of these magnetic rotor assemblies are driven by the drive member via the air gap defined between the respective magnetic rotor assemblies so that the driven member, connected to the at least one paramagnetic conductor, is dragged along by the induced magnetic fields in the at least one paramagnetic conductor thereby to effect rotation.

15. A permanent magnet coupling, substantially as shown in any one of Figures 1 to 3 of the accompanying drawings, read with the description as provided herein.