Patent ID: 7210226

Claim:
A method of manufacturing an impeller comprising the steps of: (a) forming an impeller having a plastic disc body and magnetisable material distributed and encapsulated within said body comprising the steps of; (i) locating a ring of magnetisable material in an injection mould, including centrally locating said ring by engaging an outer surface thereof at spaced locations around said surface; (ii) locating a shaft centrally within said mould, passing through said ring, such that said shaft and said ring have a common axis of rotational symmetry; (iii) injecting plastic into said mould to encapsulate said ring of magnetisable material and span between said ring and said shaft; (iv) extracting said impeller from said mould; (v) forming an annular plastic cap having a lower face and an array of impeller vanes distributed around and extending from said lower face; and (vi) securing said cap to an upper face of said disc by connecting the free ends of said vanes to said upper face; (b) testing the imbalance of said impeller; (c) removing plastic material from said impeller to compensate for said tested imbalance; and (d) magnetising said magnetisable material to have an annular array of alternating poles.