US 6,227,820 B1 · Axial force null position magnetic bearing and rotary blood pumps which use them

Abstract

A generally cylindrical rotor very closely confined between two rigid thrust bearing surfaces is radially suspended by an array of attracting or repelling magnets or by a combination of permanent magnets and ring shaped members composed of ferromagnetic material. The geometry permits very small spacing between magnetic components to achieve high radial stiffness. High magnetic axial forces exerted between the rotor and stationary component on one end of the rotor are counter-balanced by equal and opposite forces at the other end of the rotor. Precise positioning of the rotor in the location where the opposing axial magnetic forces counterballance each other yields a net magnetic axial force on the rotor of near zero, hence the reference to this as the null position. Wear resistant mechanical thrust bearings confine the rotor axially to maintain this position during rotatioin. Precisely balance the magnetic axial forces in the proper geometry with relation to the mechanical thrust bearings. Blood pumps utilizing this type of bearing are disclosed, including both axial flow pump and centrifugal flow pump configurations with high flow washing of the junction of the rotating and stationary parts to prevent thrombus accumulation.

Claims15

Dependent claims

A passive radial magnetic bearing system adapted to support a rotor for rotation about an axis while it is axially confined by mechanical means, comprising,

a. Rotor means mechanically free to rotate about an axis,
b. Axial motion limiting means to permit said rotor means to rotate while closely confining it axially,
c. Mechanical thrust bearing means affixed to said rotor means and to said limiting means,
d. A first axially magnetized generally cylindrical permanent magnet mounted to said limiting means in alignment with the axis of rotation of said rotor means, adjacent to one end of said rotor means,
e. A second axially magnetized generally cylindrical permanent magnet mounted to said limiting means in alignment with the axis of rotation of said rotor means, adjacent to the other end of said rotor means,
f. Force transferring means, comprising a pair of generally cylindrical ferromagnetic structures mounted adjacent to each end of said rotor in axial alignment with the axis of rotation of said rotor which are subject to magnetic forces originating from said first and second permanent magnets to both support said rotor for radial rotation and force it against said thrust bearing means,
g. Axial force balancing means comprising means to mount said magnets to said limiting means in position such that the net axial forces exerted on one end of said rotor by said first magnet are almost exactly counter-balanced by the axial forces exerted on the other end of said rotor by said second magnet.

4 more elements

Dependencies are inferred from the claim text.

Axial force null position magnetic bearing and rotary blood pumps which use them

Life of this patent

Axial force null position magnetic bearing and rotary blood pumps which use them

Life of this patent

Abstract

Claims15