Shrouded thrust bearings

A rotary blood pump comprising:

• a housing defining a cylindrical pumping chamber having a blood inlet and a tangential blood outlet;
• a rotatable impeller within said pumping chamber, said impeller having a rotational axis and a plurality of raised sectors surrounding said rotational axis, each of said raised sectors having an upper surface area defining a tapered region curved in the direction of rotation of said impeller and having a leading portion and a trailing portion such that a gap between each of said tapered regions and an interior surface of said housing decreases from said leading portion to said trailing portion to create a hydrodynamic thrust bearing with said interior surface of said housing when said impeller is rotating;
• a fluid flow path between each pair of adjacent sectors, each of said fluid flow paths having parallel sidewalls perpendicular to the sidewalls of adjacent flow paths and extending along an inclined bottom surface descending across the axial height of said impeller to a radially peripheral exit at the base of said impeller, the surface area of a leading sidewall of each flow path being less than the surface area of the opposite sidewall of said flow path;
• and
• inner and outer boundaries of each of said tapered regions being defined by inner and outer coextensive shrouds, an interior side of each of said inner shrouds defining an inwardly facing and concavely shaped surface area coextensive with said inner shroud and descending toward said rotational axis of said impeller.