Rotary pump for blood and other sensitive liquids

A rotary blood pump for the displacement of blood, comprising:

• a housing having a peripheral wall and a pair of lateral walls, said peripheral wall being rigid having a single-lobe trochoidal surface defining a pumping chamber with said lateral walls;
• an intake port and a discharge port opening into said chamber and formed in said housing;
• and
• a rotary piston eccentrically mounted in said chamber and eccentrically driven therein to displace blood from said intake port to said discharge port, said rotary piston having a pair of opposite edges spacedly juxtaposed directly with said surface and describing a theoretical epitrochoid (E) upon orbiting said chamber as said rotary piston is eccentrically driven therein, said edges being formed with circular arc curvature whose radius is smaller than an equidistant (a) from the center of said curvature to said surface whereby said curvature and said surface define a gap seal having a minute constant width sufficiently small to prevent substantial blood flow therepast and sufficient to prevent damage to blood cells by shear stress as said edges sweep along said surface, said curvature having a center substantially coinciding with the intersection of said epitrochoid (E) and a piston symmetry axis extending through both of the piston edges, said lateral walls defining with corresponding flanks of said piston a minute constant spacing of a width forming a gap seal sufficiently small to prevent substantial blood flow therepast and sufficient to prevent damage to blood cells by shear stress as said flanks sweep along said lateral walls.