Patent ID: 7144217

Claim:
A molten metal pump system comprising: a pump framework; a pump motor mounted on the pump framework; a pump base attached to the pump framework, the pump base including an impeller aperture with interior walls; an impeller shaft attached to the pump motor; an impeller body attached to the impeller shaft and at least partially within the impeller aperture in the pump base, the impeller body comprising: a center portion with a shaft aperture therein; a plurality of vanes extending outward from the center portion, each vane including a radially outward end, an input side, and an output side; and wherein a particle relief passageway is defined between the radially outward end of the plurality of vanes on the impeller and the interior walls of the impeller aperture, the particle relief passageway being a predetermined size to allow particles of a predetermined size to pass between the plurality of vanes and the interior wall of the impeller aperture where metal enters between the plurality of vanes and the pump base.