On-site fillable ferrofluidic seal

An on-site fillable ferrofluid seal for forming a hermetic seal around a magnetically-permeable shaft in rotatable relation with a housing, said seal comprising:

• magnet means surrounding said shaft and having an inner diameter larger than the outer diameter of said shaft;
• at least two magnetically-permeable pole pieces in magnetic communication with and sandwiching said magnet means, said pole pieces extending from said magnet means to a position close to said shaft to form gaps between the pole pieces and the shaft;
• at least one channel extending through one of said pole pieces to allow ferrofluid to be introduced into a location between said pole pieces where said ferrofluid is drawn into said gaps to form liquid O-ring seals around said shaft;
• and
• a filler tube seated in said channel, said tube having an end extending to said location between said at least two pole pieces, said filler tube end forking into two portions, one of said two portions extending towards one of said at least two pole pieces and said gap between said one pole piece and said shaft, the other of said two portions extending towards another of said at least two pole pieces and said gap between said another pole piece and said shaft.

A ferrofluid seal for forming a hermetic seal around a magnetically-permeable shaft, said seal comprising:

• a magnet surrounding said shaft;
• a plurality of magnetically-permeable pole pieces in magnetic communication with said magnet, two of said plurality of pole pieces extending beyond said magnet to a position close to said shaft to form at least one gap between each of said two pole pieces and said shaft;
• a hollow guide tube extending through said magnet to a position axially between said two pole pieces;
• and
• a filler tube filled with ferrofluid and extending through said guide tube, said filler tube having an end having a sufficient width and being positioned in sufficient proximity to both gaps formed between said two pole pieces and said shaft that ferrofluid brought to said end is simultaneously drawn to said both gaps to form a liquid O-ring seals in said both gaps.

A ferrofluid seal for forming a hermetic seal around a magnetically-permeable shaft, said seal comprising:

• a magnet surrounding said shaft;
• a magnetically-permeable pole piece in magnetic communication with said magnet, said pole piece extending towards said shaft to form a gap between said pole piece and said shaft;
• a removable filler tube having an end;
• a guide tube extending through a portion of said seal, said guide tube slidably receiving said filler tube and positioning said filler tube so that said end is located in close proximity to said gap;
• a mechanism for injecting ferrofluid through said filler tube and into said gap;
• and
• a mechanism for removing said filler tube and sealing said guide tube.

A method for filling a ferrofluid seal with ferrofluid, said seal forming a hermetic seal around a magnetically-permeable shaft and having a magnet surrounding said shaft, a magnetically permeable pole piece in magnetic communication with said magnet, said pole piece extending towards said shaft to form a gap between said pole piece and said shaft and a guide tube extending through a portion of said seal, said method comprising the steps of:

• A. inserting a removable filler tube having an end through said guide tube and positioning said filler tube end to a location near said gap;
• B. injecting said ferrofluid through said filler tube and into said gap;
• C. removing said filler tube;
• and
• D. sealing said guide tube.

A method for filling a ferrofluid seal with ferrofluid to form a hermetic seal around a shaft, said seal comprising a magnet surrounding said shaft, a pole piece in magnetic communication with said magnet and extending to close proximity with said shaft to form a gap between said pole piece and said shaft and a channel extending into said seal to allow ferrofluid to be introduced into said gap, said method comprising the steps of:

• A. Attaching one end of a non-magnetic syringe needle to a syringe containing ferrofluid, said needle having a free end;
• B. inserting said needle free end through said channel until said needle free end is at a location where ferrofluid brought to said needle free end is drawn into said gap;
• C. forcing ferrofluid from said syringe to said needle free end;
• and
• D. removing said needle free end from said channel.

A method for filling a ferrofluid seal with ferrofluid to form multiple seals around a rotatable magnetically-permeable shaft having an axis and a plurality of radially-extending shaft projections, said seal having an end and comprising a magnet surrounding said shaft and generating a magnetic field, a magnetically permeable pole piece in magnetic communication with said magnet and having a plurality of pole-piece projections, said plurality of pole-piece projections extending towards said shaft projections to form an interprojection region including a plurality of gaps therebetween, said method comprising the steps of:

• A. displacing said plurality of shaft projections relative to said pole-piece projections from an initial position an axial distance sufficient to modify said magnetic field between said two pole pieces;
• B. applying said ferrofiuid to said seal end;
• C. allowing said modified magnetic field to draw said ferrofiuid from said seal end into all of said inter-projection region;
• and
• D. returning said plurality of shaft projections to said initial position.

A method for filling a ferrofluid seal with ferrofluid to form multiple seals around a rotatable magnetically-permeable shaft having an axis and a plurality of radially-extending shaft projections, said seal having an end and comprising a magnet surrounding said shaft, a magnetically permeable pole piece in magnetic communication with said magnet and having a plurality of pole-piece projections, said plurality of shaft projections extending towards said pole piece projections to form an inter-projection region including a plurality of gaps therebetween, said method comprising the steps of:

• A. displacing said plurality of pole piece projections relative to said shaft projections from an initial position an axial distance sufficient to position one of said plurality of pole piece projections between two of said plurality of shaft projections in order to modify said magnetic field between said two pole pieces;
• B. applying said ferrofluid to said inter-projection region at said seal end;
• C. allowing said modified magnetic field to draw said ferrofluid from said seal end into all of said inter-projection region;
• and
• D. returning said plurality of pole piece projections to said initial position in order to return said magnetic field to a non-modified state where the magnetic field causes liquid O-ring seals to form in all of said plurality of gaps.