Magnetically coupled pump assembly

1. A pump assembly comprising:

a pump chamber including an inlet and an outlet;

a first cup at least partially enclosing the pump chamber and including a protrusion with a central recess;

a shaft positioned within the central recess;

a substantially hemispherical rotor unit including a plurality of ferrous metal elements spaced apart from each other and molded in plastic, the rotor unit positioned inside the first cup and rotatable around the shaft, wherein the plastic of the rotor unit has an outer surface that is curved in two perpendicular axes, wherein the plastic of the rotor unit defines a central cutout through the rotor unit, wherein the curved outer surface of the plastic is curved between two radial points having differing lengths extending from a center of the rotor unit to the curved outer surface of the plastic, wherein the plurality of ferrous metal elements are disposed on the outer surface of the plastic of the rotor unit, wherein each of the ferrous metal elements include a first surface disposed on the outer surface of the plastic of the rotor unit and a second surface opposite the first surface, and wherein the first surface and the second surface of each of the plurality of ferrous metal elements are curved around both of the two perpendicular axes;

an impeller coupled to the rotor unit; and

a stator unit positioned outside of the first cup and separated from the first cup by a second cup, wherein the stator unit includes a stator cup and a ring magnet, wherein the curved outer surface of the plastic of the rotor unit is disposed facing the ring magnet of the stator unit, wherein the plastic of the rotor unit is positioned to leave the second surface of the plurality of ferrous metal elements physically exposed to an inner surface of the first cup, and wherein the second cup includes a protrusion with a central recess that is configured to align with the protrusion with the central recess of the first cup.

2. The pump assembly of claim 1 , wherein the first cup includes a curved inner surface and wherein the curved outer surface of the plastic minimizes a gap between the first cup and the rotor unit.

3. The pump assembly of claim 1 , wherein the plurality of ferrous metal elements are constructed of stainless steel.

4. The pump assembly of claim 1 , wherein the plurality of ferrous metal elements include four ferrous metal elements.

5. The pump assembly of claim 1 , wherein the ring magnet has a curved inner surface.

6. The pump assembly of claim 1 , wherein the shaft keeps the rotor unit substantially centered within the first cup.

7. The pump assembly of claim 1 , wherein the rotor unit and the impeller are coupled together by fitting protrusions of the impeller into receiving holes of an upper surface of the rotor unit.

8. The pump assembly of claim 1 , wherein the central cutout includes an annular shoulder, and the annular shoulder contacts the protrusion of the first cup when the rotor unit tilts within the first cup.

9. The pump assembly of claim 1 , wherein the rotor unit includes a lip, and wherein the plurality of ferrous metal elements are disposed flush with the lip of the rotor unit.

10. The pump assembly of claim 1 , wherein the rotor unit includes a first flat surface and a second flat surface, wherein the curved outer surface of the plastic meets the first flat surface and the second flat surface.

11. A pump assembly comprising:

a disposable portion including:

a first cup including a protrusion with a central recess,

a shaft positioned within the central recess,

a substantially hemispherical rotor unit including a plurality of ferrous metal elements spaced apart from each other and molded in plastic, the rotor unit positioned inside the first cup and rotatable around the shaft, wherein the plastic of the rotor unit has an outer surface that is curved in two perpendicular axes, wherein the plastic of the rotor unit defines a central cutout through the rotor unit, wherein the curved outer surface of the plastic is curved between two radial points having differing lengths extending from a center of the rotor unit to the curved outer surface of the plastic, wherein the plurality of ferrous metal elements are disposed on the outer surface of the plastic of the rotor unit, wherein each of the ferrous metal elements include a first surface disposed on the outer surface of the plastic of the rotor unit and a second surface opposite the first surface, wherein the first surface and the second surface of each of the plurality of ferrous metal elements are curved around both of the two perpendicular axes, and wherein the plastic of the rotor unit is positioned to leave the second surface of the plurality of ferrous metal elements physically exposed to an inner surface of the first cup, and

an impeller coupled to the rotor unit; and

a reusable portion including:

a stator unit with a stator cup and a ring magnet, wherein the curved outer surface of the plastic of the rotor unit is disposed facing the ring magnet of the stator unit;

a second cup positioned over the stator unit and the ring magnet so that the second cup physically separates the first cup from the stator unit when the disposable portion and the reusable portion are coupled together, wherein the second cup includes a protrusion with a central recess that is configured to align with the protrusion with the central recess of the first cup;

the disposable portion and the reusable portion being removably coupled together by positioning the first cup within the stator cup so that the ring magnet encircles the rotor unit.

12. The pump assembly of claim 11 , wherein the ring magnet includes a curved inner surface.

13. The pump assembly of claim 11 , wherein the reusable portion includes a motor coupled to the stator unit.

14. The pump assembly of claim 11 , wherein the plurality of ferrous metal elements have an outer curvature that matches the curved outer surface of the plastic.

15. The pump assembly of claim 11 , wherein the rotor unit is a substantially solid piece with the central cutout.