Coaxial, multiple-shaft ferrofluid seal apparatus

摘要

A multiple-shaft coaxial ferrofluid seal apparatus which comprises: a nonmagnetic housing; a central shaft element; and one or more successively coaxial shaft elements about the central shaft element with one or more of the coaxial shaft elements composed of a nonmagnetically permeable shaft section between a first and second magnetically permeable shaft sections. The seal apparatus includes an axial polarized annular permanent magnet together with first and second pole piece elements, the pole piece elements generally aligned with the magnetically permeable shaft sections to provide for a single magnetic structure within the housing and for a closed-loop magnetic flux to retain ferrofluid as a ferrofluid seal between the coaxial shaft elements which provides for hermetic sealing of the rotary motion of two or more of the coaxial shaft elements employing a single magnetic structure. The multiple-shaft coaxial ferrofluid seal apparatus also includes rotary bearings for the coaxial and central shaft element.