GB2364174A

GB2364174A - Method and means of magnetizing and mounting permanent magnets on a ferrous member

Info

Publication number: GB2364174A
Application number: GB0009755A
Authority: GB
Inventors: Nazar Ai-Khayat; Neil Brown; Jeremy Owen Dowdall; John Ernest Bean; Stephen Frederick Allen; Cleveland Mills
Original assignee: Newage International Ltd
Current assignee: Cummins Generator Technologies Ltd
Priority date: 2000-04-19
Filing date: 2000-04-19
Publication date: 2002-01-16
Anticipated expiration: 2020-04-19
Also published as: GB2364174B; GB0009755D0

Abstract

A method and means of magnetizing and mounting permanent magnets on a ferrous member 10 comprises: sequentially supplying plates 60 of unmagnetised magnetisable material to magnetizing means 51. Energizing the magnetizing means 51 to magnetise each plate 60. Then mounting the said plates 60 in sequence into respective positions on the ferrous member 10 such that the polarity of each plate 60 is opposite to that of the plates adjacent to it. Each part of a two part adhesive 40 may be separately applied to the plate receiving positions 35, formed by radially extending arms 32 on the ferrous member 10. A projecting lip 20 and resilient bias means 33 may be used to clip the plate 60 into position. On insertion of the plate 60 into a position the adhesive 40 may act as a lubricant whilst the two parts of the adhesive are mixed and chemically react to hold the plate in position. The magnetizable plates 60 may be formed of rare earth material such as NeFeB.

Description

2364174 "A Method of and Apparatus for Automatically Mounting Permanent

Magnets on a Member Formed of Ferrous Metal" This invention relates to mounting permanent magnets.

In particular it relates to mounting permanent magnets on a member formed of ferrous metal.

Handling energised magnets is not straightforward.

Movement can be affected by nearby ferrous objects and ferrous debris can be attracted to the surface of the magnets Handling is particularly difficult if the magnets are rare-earth permanent magnets Such magnets tend to be very brittle and therefore prone to breaking All these problems affect the attachment of energised magnets to the rotor plates of electrical machines It is an object of this invention to address these problems.

According to one aspect of this invention there is provided a method of mounting permanent magnets on a member formed of ferrous metal including the steps of:

(i) selecting plates of unmagnetised magnetisable material; (ii) presenting the selected plates one after another to magnetising means; (iii) actuating the magnetising means to energise each plate in turn with a different polarity from the next plate; and (iv) mounting each magnetised plate in position on the member.

The method may include the additional steps of:

a) forming the member into a flat disc with a raised circumferential lip on one side; b) applying an adhesive to the one side of the member; c) fixing a spider to the one side, the spider comprising a plurality of radially extending arms which together with the one side of the member and the lip define a plurality of circumferentially distributed compartments on the one side of the member; d) supporting the member such that its plane lies substantially horizontally, with the one face uppermost; e) moving a magnetised plate towards the centre of the member in a radial direction, the magnetised plate lying in a plane which is parallel to that of the member and which results in a lower surface of the magnetised plate sliding over the lip, and the angular position of the member being such that the magnetised plate approaches a compartment; f) continuing to move the magnetised plate towards the centre of the member such that eventually the magnetic attraction between the magnetised plate and the member causes the magnetised plate to pivot about the lip and adopt a position wherein part of the lower surface contacts the adhesive on the one side of the member and part of the lower surface contacts the lip; g) further continuing to move the magnetised plate towards the centre of the member until all the magnetised plate has moved over the lip and the magnetic attraction between the magnetised plate and the member causes the magnetised plate to adopt a position wherein all the lower surface of the magnetised plate contacts the adhesive and locates the magnetised plate within the compartment; and h) curing the adhesive to secure the magnetised plate relative to the member.

The adhesive may have lubricant properties and act as a lubricant between the lower surface of the magnetised plate and the one side of the member, thereby facilitating relative movement between the magnetised plate and the member.

The spider may include resiliently deformable structure between two or more arms which further defines the plurality of compartments and is adapted to deform in reaction to pressure from the magnetised plate such that step (g) further comprises the step of:

(g)(i) the resiliently deformable structure partially recovering its shape and pushing the magnetised plate away from the centre of the member such that the magnetised plate abuts the lip.

The adhesive may also be a two-part adhesive which is cured by a chemical reaction between a first chemical component and a second chemical component, and each component may be applied to the one side of the member so as to form concentric rings containing that component, rings containing the first component of the adhesive being juxtaposed with rings containing the second component such that the movement of the part of the lower surface of the magnetised plate which contacts the adhesive causes the two components to mix and the chemical reaction to commence.

The magnetised plates may be of a rare-earth material and are preferably Neodymium-Iron-Boron (Ne Fe B).

According to another aspect of this invention there is provided a member formed of ferrous metal and apparatus for mounting permanent magnets on the member, the apparatus comprising mechanical handling means, magnetising means and mounting means, wherein the handling means is operable to select plates of unmagnetised magnetiseable material and present the selected plates to the magnetising means, the magnetising means is operable to energise each plate in turn with a different polarity from the next plate and the mounting means is operable to mount each magnetised plate on the member.

The member may comprise an abutment for each plate, each abutment projecting from the member and serving as locating means for locating the respective plate on the member.

The locating means may include resilient means which act to urge the respective plate against the respective abutment.

A specific embodiment of the present invention is now described by way of example and with reference to the following drawings of which:

Figure 1 is an axial view of a rotor and a spider; Figure 2 is a perspective view of a device for selecting, magnetising and locating magnetiseable plates; Figure 3 is a sectional view of the rotor and spider of Figure 1, the section being on the line III-III; Figure 4 is a view similar to Figure 3 showing the magnet advanced; and Figure 5 is another view similar to Figure 3 showing the magnet further advanced.

Figure 1 shows a rotor plate 10 The rotor plate 10 is cast from a ferrous material so as to form a flat annular disc A circumferentially continuous lip 20 is formed integrally around the periphery of the cast disc 10 on one of its two sides The lip 20 is more clearly shown in the cross section of Figure 3.

Figure 1 also shows a spider 30 This is made from an injected-moulded, resiliently-deformable material, such as nylon The spider 30 comprises a central hub 31 with a number of arms 32 protruding radially therefrom with constant angular pitch In this particular embodiment there are six arms 32 arranged with a pitch of 60 degrees Each arm 32 has two ends:

a root that is connected to the hub 31 and a free end that is furthermost from the hub 31 Additional structure 33 is provided between the roots of each adjacent pair of arms 32 This additional structure 33 forms an arcuate section of the circumference of a circle that is concentric with the hub 31 The free end of each arm 32 comprises a bolt hole for use in attaching the spider 30 to the rotor plate 10.

In combination, the lip 20, the arms 32 of the spider and the additional structure 33 of the spider 30 define six compartments 35 on the surface of the rotor plate 10.

( Adhesive 40 is applied to the surface of the rotor plate 10 in each compartment 35 The adhesive 40 is a two-part adhesive which comprises two chemical components which are respecively applied as globules 41 and 42, see Figure 3 When the globules 41,42 of the two components are mixed, a chemical reaction occurs and the adhesive 40 cures In both its unmixed state and mixed state (prior to curing), the adhesive exhibits lubricant properties.

Figure 2 shows the rotor plate 10 rotatably positioned on a device 50 The device 50 comprises a stack of unmagnetised magnetiseable plates 60 of a rare earth material such as Neodymium-Iron-Boron, and a magnetiser 51 Each plate 60 is of a size that would make it a sliding fit in one of the compartments 35 if inserted in a direction perpendicular to the one side of the rotor plate 10.

The rotor plate 10 is positioned adjacent to the magnetiser 51, which in turn is adjacent to the stack of unmagnetised magnetiseable plates 60 Also included in the device 50 is a pusher (not shown) The pusher is an actuatator rod which is operable to move a plate 60 from the stack and push it through the magnetiser 51 onto the rotor plate 10 Such actuators are well known to those skilled in the art and need not be described further When the plate 60 is pushed through the magnetiser 51, the magnetiser 51 energises the plate 60, turning it into a permanent magnet with a certain polarity During this proces the rotatably mounted rotor plate 10 is indexed so that a compartment 35 lines up with the magnetiser 51 The energised plate 60 is then pushed into a first compartment 35 and located on the rotor plate 10; a procedure described more fully below The pusher then returns to the stack of plates 60 to select another plate 60 from the botom of the stack This other plate is energised as described previously but with a polarity that is opposite to the certain polarity given to the plate 60 During the energising procedure, the rotor plate is indexed so that a second compartment 35 lines up with the magnetiser 51, the second compartment 35 being adjacent to the first compartment 35 The other plate 60 is then pushed into the second compartment and located on the rotor plate 10.

Figure 3 shows a sectional view through a compartment 35 at the line II-II of Figure 1 The compartment 35 on the one side of the rotor plate 10 is enclosed on a first side by the additional structure 33 of the spider and on a second side by the lip 20 Also shown is the hub of the spider 31 and the globules 41 and 42 of the two components of the adhesive 40.

The spatial positioning of the rotor plate 10 relative to the device 50 is such that the top of the lip 10 is level with an energised plate delivery surface 52 of the device 50 The angular positioning of the rotor plate 10 relative to the device 50 is such that one compartment 35 is aligned with the approaching plate 60.

The device 50 moves the energised plate 60 towards the hub 31 of the spider 30 such that the energised plate moves over the lip 20 of the rotor plate 10 in a direction indicated by arrow 55 When a substantial portion of the energised plate 60 has moved over the lip 20, the magnetic attraction between the energised plate 60 and the rotor plate 10 causes the energised plate to rotate about the lip 10 and adopt the position shown in Figure 4 In this position, the energised plate 60 is in contact with the adhesive 40 and the lip 20 The adhesive 40 acts as a cushion during this rotation and reduces the likelihood of the energised plate breaking The energised plate 60 continues to move under the influence of the device 50 in the direction shown by arrow 55 Movement of the energised plate 60 relative to the rotor plate 10 is facilitated by the adhesive 40 which acts as a lubricant In addition, movement of the energised plate 60 over the adhesive 40 causes the two components 41,42 to mix and the curing process to commence.

The movement of the energised plate 60 continues in this manner until the energised plate 60 reaches the additional structure 33 as shown in Figure 5 Further movement of the energised plate 60 in the direction shown by the arrow 55 causes the additional structure 33 to deform When all of the energised plate 60 has moved over the lip 20, the magnetic attraction between the energised plate and the one side of the rotor plate 10 causes the energised plate 60 to rotate again and adopt a position wherein the energised plate 60 is within the compartment 35 The additional structure 33, being of the resiliently-deformable material referred to above, attempts to recover its original shape and exerts a force on the energised plate 60 in an opposite direction to that shown by arrow 55 This force causes the energised plate 60 to move in the direction of the force until it abuts the lip 20 In- so-doing, the remaining unmixed components 41,42 of the adhesive 40 are mixed This movement is again facilitated by the lubricant properties of the adhesive 40 When curing has taken place, the energised plate 60 is held firmly in position within the compartment 35.

As will be appreciated by the skilled addressee, under operating conditions an energised plate attached to a rotor plate is subject to tangential and radial forces These forces act to dislodge the energised plate from the rotor The embodiment discussed above counters the tangential forces by means of the arms 32 of the spider 30 and the radial forces by means of the lip 20 of the rotor plate 10 As a consequence the energised plate 60 remains in position within the compartment 35 during operation.

Claims

1 A method of mounting permanent magnets on a member formed of ferrous metal including the steps of:

(i) selecting plates of unmagnetised magnetisable material; (ii) presenting the selected plates one after another to magnetising means; (iii) actuating the magnetising means to energise each plate; and (iv) mounting each magnetised plate one after another in position on a surface of the member such that each magnetised plate has a different polarity adjacent the surface than does the respective magnetised plate mounted previously thereto and/or the respective magnetised plate mounted subsequently thereto.

2 A method according to claim 1 wherein step (iv) includes the step of pushing each magnetised plate such that each magnetised plate slides across the surface of the member into position on the surface.

3 A method according to claim 2 wherein step (iv) is preceded by the step of applying an adhesive to the surface of the member, the adhesive having lubricant properties such that it acts as a lubricant between each magnetised plate and the surface of the member, thereby facilitating the sliding of each magnetised plate across the surface of the member.

4 A method according to claim 3 wherein the adhesive is a two-part adhesive which is cured by a chemical reaction between a first chemical component and a second chemical component thereof, each component being applied to the surface of the member so as to be juxtaposed thereon such that the sliding of the magnetised plates across the surface of the member causes the two components to mix and the chemical reaction to commence.

A method according to any one of the preceding claims wherein the member is a disc and step (iv) includes the step of rotationally indexing the disc through a constant angle such that subsequent magnetised plates are mounted on the member so as to be angularly spaced and such that, collectively, the magnetised plates form a circular array on the surface of the member.

6 A method according to claim 5 and including the step of:

fixing a spider to the surface, the spider including a plurality of radially extending arms arranged with a constant angle therebetween substantially equal to the constant angle through which the disc is indexed such that the spider circumferentially locates the magnetised plates, each plate being sandwiched between a respective pair of radially extending arms.

7 A method according to claim 6 wherein the member is a disc that includes a radially outermost circumferential lip projecting from the surface of the member, and the spider includes resiliently deformable structure between two or more arms which is adapted to deform in reaction to pressure from at least one magnetised plate and to at least partially recover its shape so as to push the magnetised plate into abutment with the lip, thereby radially locating the magnetised plate.

8 A method according to any one of the preceding claims wherein the magnetised plates are of a rare-earth material.

9 A method according to any one of the preceding claims wherein the magnetised plates are Neodymium-Iron-Boron (Ne Fe B).

A member formed of ferrous metal and apparatus for mounting permanent magnets on the member, the apparatus comprising mechanical handling means,

magnetising means and mounting means, wherein the handling means is operable to select plates of unmagnetised magnetiseable material and present the selected plates to the magnetising means, the magnetising means is operable to energise each plate and the mounting means is operable to mount each magnetised plate on the member in turn with a different polarity from the next plate.

11 A member formed of ferrous metal and apparatus for mounting permanent magnets on the member according to claim 10 wherein the member includes an abutment for each plate, each abutment projecting from the member and serving as locating means for locating the respective plate on the member.

12 A member formed of ferrous metal and apparatus for mounting permanent magnets on the member according to claim 11 wherein the member is a disc having a surface on which the magnetised plates are mounted in a circular array and the locating means includes a spider having a plurality of radially extending arms arranged such that the spider circumferentially locates the magnetised plates, each magnetised plate being sandwiched between a respective pair of radially extending arms.

13 A member formed of ferrous metal and apparatus for mounting permanent magnets on the member according to claim 11 or claim 12 wherein the locating means includes resilient means which act to urge the respective magnetised plate against the respective abutment.

14 A member formed of ferrous metal and apparatus for mounting permanent magnets on the member according to claim 13 when appended to claim 12, wherein the abutment includes a circumferential lip projecting from the periphery of the surface of the disc and the spider includes resiliently deformable structure between two or more radially extending arms thereof adapted to deform in reaction to pressure from at least one magnetised plate and to at least partially recover its shape so as to urge the magnetised plate into abutment with the circumferential lip.

15 A member formed of ferrous metal and apparatus for mounting permanent magnets on the member according to any one of claims 8 to 12 wherein the plates are of a rare-earth material.

16 A member formed of ferrous metal and apparatus for mounting permanent magnets on the member according to claim 13 wherein the plates are Neodymium-Iron-Boron (Ne Fe B).

17 A method substantially as described hereinbefore with reference to the accompanying drawings.

18 A member formed of ferrous metal and apparatus for mounting permanent magnets on the member substantially as described hereinbefore with reference to the accompanying drawings and as shown in those drawings.