US Patent 7396153 Ultraclean magnetic mixer

In a magnetically-coupled liquid mixer of the type having a drive mount secured to and extending into a mixing vessel, an external first magnet array adjacent to the drive mount, a stub shaft extending from the drive mount into the vessel and having a first thrust bearing surface, and a driven portion rotatably-mounted on the stub shaft and having a second thrust bearing surface and a second magnet array, the improvement wherein the first and second arrays are positioned with respect to one another such that the first and second thrust bearing surfaces are spaced apart at least in the absence of above-threshold fluid dynamic thrust forces on the driven portion.