Nok Corporation

Takao Kanno

Yutaka Kouda

Tomoko Minagawa

Hirokazu Nagato

Yoshiyuki Takeishi

Yasushi Yamamoto

Hiroshi Anzai

Yoshimi Imamoto

Yutaka Koda

Hirokazu Yamamoto

Takahiro Ishizuka

Yasuki Karita

Takemi Namba

A magnetic fluid seal device that increases a permissible value of eccentricity for two members to improve sealability and decreases a variation of quality by injecting a magnetic fluid before assembling of parts, that saves structural members to achieve thinning, and that is easy to produce. An annular magnetis buoyantly supported by the magnetic fluidandretained, and the space between a housingand a shaftis sealed by the annular magnetand magnetic fluidand

Magnetic fluid seal device

There is provided a light shielding apparatus with a light shielding seal that reduces a sliding resistance and, at the same time, improves light shielding property and realizes saving of a space. There is provided a light shielding structure that is provided between a plurality of members and , which are arranged to be able to move relatively to each other spaced a predetermined distance apart, and is capable of preventing light from entering from a gap to be formed between these plurality of members and , having magnetic force generating means and that are disposed in any one of the above-mentioned plurality of members and and magnetic fluid which is magnetically held by the magnetic force generating means and and contacts the other member and shielding a gap, which is formed between the above-mentioned plurality of members and , by the above-mentioned magnetic fluid

Light shielding structure

A fluorine-based magnetic fluid, which comprises (A) fine magnetic particles as dispersed in (D) a perfluoropolyether base oil represented by the following general formula:

Fluorine-based magnetic fluid

A fluorine-based magnetic fluid, which comprises (A) fine magnetic particles dispersed in (D) a perfluoropolyether base oil represented by the following general formula:

A magnetic fluid is produced by adding a solution of N-polyalkylenepolyamine-substituted alkenylsuccinimide in a hydrocarbon solvent to an aqueous suspension of fine particles of ferrites, thereby adsorbing the N-polyalkylenepolyamine-substituted alkenylsuccinimide onto the fine particles of ferrites, distilling off water and the hydrocarbon solvent therefrom, and dispersing the fine particles of N-polyalkylenepolyamine-substituted alkenylsuccinimide-adsorbed magnetites as residues into a base oil of low vapor pressure having a vapor pressure of not more than 0.1 mmHg at 25.degree. C.

Process for producing magnetic fluid

A magnetic fluid containing fine particles of ferrite stably dispersed in a carrier liquid is prepared by adding carrier liquid and a dispersing agent selected from N-polyalkylenepolyamine-substituted alkenylsuccinimide, an oxyalkylene-substituted phosphoric acid ester and a nonionic surfactant, and, if required, hydrocarbon solvent having a low boiling point to particles of ferrite which is coated with water-soluble surfactant and subjecting the resulting mixture to a dispersion treatment and, if required, removal of the hydrocarbon solvent.

Process for preparing a magnetic fluid

A magnetic fluid containing fine particles of ferrite stably dispersed in a low vapor pressure base oil is prepared by adding N-polyalkylenepolyamine-substituted alkenylsuccinimide (and a low vapor pressure base oil) to a suspension of fine particles of surfactant-adsorbed ferrite dispersed in a low boiling point hydrocarbon solvent, heating the resulting mixture, separating the hydrocarbon solvent therefrom, adding a low vapor pressure base oil and a specific dispersing agent to the fine particles of N-polyalkylenepolyamine-substituted alkenylsuccinimide-coated ferrite as the residues and subjecting the resulting mixture to a dispersion treatment.

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Tokyo, Japan

Takao Kanno