Patent ID: 7052253

Claim:
A fluid pump comprising: (a) a housing with an inner wall defining a chamber having an axis and having opposed ends disposed coaxially with said chamber; (b) a rotor having opposed first and second ends and being operationally disposed within said chamber and having a rotor axis defining an axis of rotation, said rotor comprising: (i) a rotor body having a relative density substantially less than that of the respective fluid being pumped; (ii) a configuration defining a surface of revolution with an axial length defined between said first and second ends and providing a predetermined clearance between said rotor and said first and second ends, and with a diameter of said rotor body transverse to said axis of rotation being selected to provide a predetermined radial clearance between an outer surface of said rotor body and the inner wall of said housing, the clearances between said rotor and said housing being sufficiently large so as to render the effects of hydrodynamic bearings ineffective in stably supporting said rotor; (c) drive magnets disposed on said rotor and being positioned radially outwardly of said rotor axis generally medially of said first and second ends; (d) an electromagnetic drive mechanism coupled to a source of energy and arranged along said housing to deliver rotational driving energy to said rotor through said drive magnets; and (e) a plurality of passive magnetic bearing sets disposed on said housing and said rotor, said passive magnetic bearing sets including first and second magnetic bodies in mutually magnetically coupled relationship, with the first magnetic bodies of each bearing set being mounted on said rotor and with the second magnetic bodies of each bearing set being mounted along the inner wall of said housing, said first magnetic bodies being disposed adjacent to and in magnetically coupled relationship to respective second magnetic bodies to form respective bearing sets, each of said first and second magnetic bodies solely comprising a permanent magnet, each of the said first and second magnetic bodies comprising each of said passive magnetic bearing sets being polarized and positioned in mutually attracting or mutually repelling relationship so as to function as bearings selected from the group consisting of radial and thrust, said plurality of passive magnetic bearing sets being further arranged to form a passive suspension for said rotor within said housing, with said passive suspension having negative stiffness only in directions perpendicular to the rotor axis of rotation, such negative stiffness being of a magnitude such that centrifugal forces developed during rotation of said rotor overcome said negative stiffness and create positive stiffness of said rotor suspension in all required degrees of freedom.