Tdk Electronics Company, Limited

Takeo Tada

Katsuji Honda

Masami Oguriyama

Yoshifumi Hirata

In an anisotropic polymeric magnet in tubular form, the magnetization orientation is directed in one direction perpendicular to the axial line of the tubular magnet. In a bipolar anisotropic magnet in tubular form, the magnetic poles can be formed only at symmetrical portions of the magnet with respect to the axial line and an imaginary line connecting the magnetic poles with each other is parallel to said one direction. In order to symmetrically distribute the magnetism around a tubular bipolar anisotropic magnet, a weld line(s) formed by injection molding of a mixture of ferromagnetic material powder and polymeric material is located in the portion(s) of the magnet where the magnetic poles are not formed. In the processes for producing the tubular anisotropic magnet, the gate(s) for injecting a mixture of ferromagnetic material powder and polymeric material is positioned in an injection machine, so that the position of the confronting ends of the flow(s) of the mixture do not coincide with the position of the magnetic poles.

Anisotropic polymeric magnet in the tubular form and process for

A rubber or plastic magnet of high magnetic properties is produced by incorporating a magnetoplumbite type magnetic powder into a rubber or thermoplastic or thermosetting matrix at a high concentration with a high degree of orientation of the magnetic particles. Such high concentration and orientation can be obtained by using a magnetoplumbite type magnetic powder having a compressed density in the range between 3.30 g/cm.sup.3 and about 3.55 g/cm.sup.3 and an average particle size of about 1.00 and 1.50.mu., said particles being prepared by dry crushing process from coarse sintered particles and having predominantly single crystal structure.

Rubber or plastic magnet and magnetic powder for making the same

Procedure for pulverizing ferrite particles for use in the production of flexible magnets utilizing alcohols containing up to 4 carbon atoms and having a boiling point up to 100.degree. C. as a pulverization promoter, annealing at an elevated temperature, and dispersing in a flexible, nonmagnetic matrix.

Process for producing flexible magnets

An improved roller, consisting in part of a cylindrical permanent magnet, for use in electrostatic record developing devices is disclosed. Of the plurality of magnetic poles formed on the cylindrical surface of the permanent magnet, two of the same polarity are positioned with an auxiliary magnetic pole of opposite polarity located therebetween. The magnetic field intensity of the auxiliary magnetic pole is from about 1/10 to 1/2 that of the other magnetic poles.

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Urawa, Japan

Takeo Tada