Impeller

1. An impeller comprising:

a plastic disc having an upper face and a lower face,

an annular array of vanes spaced around the periphery of said disc and extending from said upper face,

an axially located and aligned rotation support passing through said plastic disc, and regions of permanently magnetisable material encapsulated within said plastic disc for the formation of an annular array of magnetic poles,

wherein said magnetisable material comprises a ring of magnetisable material within said plastic disc, said ring and said plastic disc each having a common axis of symmetry,

wherein said rotation support comprises a shaft passing through and extending from either side of said plastic disc, said shaft having a common axis of symmetry of said plastic disc and said ring,

wherein said plastic disc includes a hub portion spanning between an inner edge of said ring of magnetisable material and an outer surface of said shaft, and in said hub region, said upper face of said plastic disc extends upward along the outer surface of said shaft,

wherein said impeller includes an annular plastic cap spanning amongst and connecting with the tops of said annular array of vanes, and having a central opening there through above said hub portion of said plastic disc, with an upper end of said shaft protruding into said central opening and,

wherein said vanes are integrally moulded with said cap, extending from a lower surface of said cap and having lower ends which contact and are secured with said upper face of said plastic disc.