Title of Invention

IMPROVEMENTS IN HIGH SPEED ROTOR SHAFTS

Abstract

A rotor (10) for a high speed machine, such as a brushless, DC motor, said rotor having a rare earth magnetic core (12), a sleeve (14) formed of non-magnetic material surrounding said magnetic core (:2) to radially constrain the core during high speed rotation thereof, the sleeve (14) extending beyond from the core in both axial directions, end pieces (16, 18) secured within each end of the sleeve (14) and respectively directly or indirectly engaged with each end of the magnetic core (12) characterised in that the end pieces (16, 18) apply an axial compressive force to the magnetic core with the sleeve (14) being heat-shrunk onto the end pieces (16, 18) to secure the end pieces (16, 18) in the sleeve (14).

Full Text

WE CLAIM: 1. A process for the production of expandable particles of styrene polymers, having improved processability characteristics, which comprises: i) producing expandable particles of styrene polymers containing from 2 to 20% by weight of an expanding agent as herein described; ii) covering these particles with an antistatic agent as herein described in a quantity of less than 1% by weight; iii) vigorously frictioning the particles in a mixing apparatus in order to heat their surface, by simple mechanical friction alone; iv) discharging the particles thus treated from the mixing apparatus. 2. The process according to claim 1, wherein the friction is such as to heat the mass of particles to a temperature ranging from 20 to 55°C. 3. The process according to claim 1 or 2, wherein the particles of styrene polymers containing the expanding agent are produced by carrying out the polymerization in an aqueous suspension of a styrene monomer, alone or mixed with one or more ethylenically unsaturated monomers copolymerizable with this, in the presence of the expanding agent. 4. The process according to claim 3, wherein the suspending agents are selected from products soluble in water such as polyvinylalcohol, methyl-cellulose, polyvinylpyrrolidone and not very soluble products such as magnesium pyrophosphate or calcium triphosphate. 5. The process according to claim 3, wherein the expanding agent is selected from aliphatic hydrocarbons, alone or mixed with each other, containing from 2 to 6 carbon atoms; petroleum ether; halogenated derivaties of aliphatic hydrocarbons containing from 1 to 3 carbon atoms; carbon dioxide. 6. The process according to any of the previous claims, wherein the antistatic agents are selected from the esters of fatty acids; mono- or poly-hydric alcohols; amines; amides; polyoxyethylene or polyoxyalkylene derivatives; ethylene oxide-propylene oxide copolymers; aminic soaps; aminic salts of alkylsulphates; compounds of quaternary ammonium; alkylphosphates; aminic salts of alkyl-phosphonic acids. 7. The process according to any of the previous claims, wherein the quantity of antistatic agent is between 0.001 and 0.5% by weight. 8. The process according to any of the previous claims, wherein the vigorous friction operation is carried out by means of a screw mixer or a rotating blade mixer. 9. A process for the production of expandable particles of styrene polymers substantially as hereinbefore described. WE CLAIM 1. A rotor for a high speed machine, such as a brushless, DC motor, said rotor having a rare earth magnet core, a sleeve surrounding said magnet core to radially constrain the core during high speed rotation thereof, the sleeve extending axially from the core in both axial directions to form a hollow shaft for the rotor, the sleeve being formed of electrically conductive material, and end pieces within the sleeve and respectively directly or indirectly engaged with each end of the magnet core, said end pieces applying an axial compressive force to the magnet core. 2. A rotor according to claim 1 wherein the machine is a DC motor in which the magnet core is magnetized diametrically, and the core material is Neodymium-Ircin-Boron 3. A rotor according to claim 1 or claim 2 wherein the resonant bending frequency of the rotor exceeds the maximum rotating frequency. 4. A rotor according to any one of claims 1 to 3 wherein the sleeve applies a radial compressive force to the magnet core so that the core is under both radial and axial compressive forces while at rest. 5. A rotor according to claim 1 wherein the compressive force is of a magnitude that, at maximum rotational speed, minimal, if any, tension occurs in the magnetic core. 6. A rotor according to any one of claims 1 to 5 wherein at least one of the end pieces is indirectly engaged with the respective end of the core through a non-magnetic spacer. 7. A rotor according to any one of claims 1 to 6 wherein the rotor sleeve is formed of a non-magnetic, high strength metal, which has a relatively high Young's modulus to provide bending stiffness for the motor shaft. 8. A rotor according to claim 7 wherein the material of the rotor sleeve is selcclcd from tnconcl, titanium and titanium alloy. 9. A rotor according to any one of claims 1 to 8 wherein the end pieces are held in place in the sleeve by heat shrinking the sleeve onto an assembly of the end pieces and magnet core. 10. A rotor according to any one of claims 1 to 8 wherein the end pieces are connected to the sleeve by welding or adhering one or both end pieces to the sleeve either while applying tension to the sleeve or applying compressive forces to the pieces. 11. A method of constructing a rotor for a high speed machine, said rotor including a rare earth magnet core, including steps of forming a sleeve the inner diameter of which is of a dimension which provides an interference fit with end pieces to he located within the sleeve, heating the sleeve to a temperature below its tempering temperature so that the sleeve radially and axially expands, inserting the magnet core and end pieces in the expanded sleeve, applying an axial force to the end pieces so as to apply compressive forces to the core, and cooling the sleeve whereby the sleeve shrinks around the outer surfaces of the magnet core and end pieces. 12. -A method according to claim 11 wherein the diameter of the magnet core is of a dimension which gives an interference fit with the sleeve. 13. A method according to claim 11 or claim 12 wherein the sleeve is heated to the desired temperature by an induction heating coil system into which the sleeve is placed. 14. A method according to any one of claims 11 to 13 including the step of rapidly cooling the heated sleeve while the core is under compressive pre-stressing forces. 15. A method according to claim 14 including the step of controlling the rate of cooling to prevent damage to the magnetic properties and the surface of the magnet core and to ensure that the sleeve engages with and grips the end pieces before engaging and gripping the magnet core. 16. A method of constructing a rotor for a high speed machine, said rotor including a rare earth magnet core, including the steps of forming a sleeve, locating the core within the sleeve, providing end pieces in the sleeve to engage either directly or indirectly through a spacer with the axial ends of the core, axially compressive pre-stressing the core using the end pieces, and securing the end pieces to the sleeve while the core is axially pre-stressed. 17. A method according to claim 16 wherein the end pieces are secured to the sleeve by welding, adhesive or heat-shrinking the sleeve to produce an interference fit. 18. A rotor produced by the method of any one of claims 11 to 17. 19. An electric motor having a rotor according to any one of claims 1 to 10 or claim 18. 20- A rotor for a high speed machine substantially as hereinbefore described with reference to the accompanying drawings. 21• A method of constructing a rotor for a high speed machine substantially as hereinbefore described with reference to the accompanying drawings. ! i i 22* - An electric motor having a rotor substantially as hereinbefore described with reference to the accompanying drawings.

Documents:

175-mas-1998-abstract.pdf

175-mas-1998-assignment.pdf

175-mas-1998-claims duplicate.pdf

175-mas-1998-claims original.pdf

175-mas-1998-correspondence others.pdf

175-mas-1998-correspondence po.pdf

175-mas-1998-description complete duplicate.pdf

175-mas-1998-description complete original.pdf

175-mas-1998-drawings.pdf

175-mas-1998-form 1.pdf

175-mas-1998-form 26.pdf

175-mas-1998-form 3.pdf

175-mas-1998-form 4.pdf

175-mas-1998-pct.pdf