Coaxial, multiple-shaft ferrofluid seal apparatus

Claim 1

A coaxial, multiple-shaft radially polarized ferrofluid seal apparatus, which apparatus comprises: (a) a magnetically permeable housing for the seal apparatus; (b) a magnetically permeable central shaft element extending in the housing; (c) a one or more spaced apart magnetically permeable coaxial shaft elements about the central shaft element, and each coaxial shaft including first and second spaced apart nonmagnetically permeable shaft sections to define a magnetically permeable central section there between; (d) a radially polarized annular permanent magnet means secured to one of the coaxial shafts to provide a source of magnetic flux; (e) a thin magnetically permeable annular sleeve means secured to one radially polarized surface of the permanent magnet to form one or more radial gaps with a surface of a coaxial shaft element; (f) pole block means comprising a magnetically permeable block element which includes at least first and second pole block means having spaced apart raised pole piece at the one and other axial end to form a plurality of radial gaps under each pole piece with a surface of a shaft element, the first pole piece means secured to the housing and the second pole piece means secured to the central shaft; (g) a pair of magnetically permeable bearing means for each shaft to support the central and coaxial shaft elements, the bearing means disposed on either side of the permanent magnet means; (h) nonmagnetically permeable annular insulating means to insulate magnetically each of the bearing means from the permanent magnet means and each of the pole block means, the insulating means radially aligned with the first and second shaft sections; and (i) ferrofluid in the radial gaps to form a plurality of ferrofluid O-ring seals under each pole piece and sleeve means and to provide for the sealing of the coaxial shaft elements whereby the magnetic flux from the permanent magnet passes in a closed circuit through the housing, the bearing means, the central shaft, the pole block means, the sleeve means, the central shaft sections, the ferrofluid in the radial gaps; and the radially polarized permanent magnet means.