An impeller includes a plastic disc, an annular array of vanes, a rotation
support and regions of permanently magnetisable material. The plastic disc
has an upper face and a lower face. The vanes are spaced around the
periphery of the disc and extend from the upper face of the plastic disc.
The rotation support is axially located and aligned through the disc. The
regions of permanently magnetisable material encapsulated within said
plastic disc for the formation of an annular array of magnetic poles.
