Abstract: A liquid dielectric having a surface that is contacted by an end of an electrode so as to form a contact area between the electrode and dielectric liquid wherein said area is limited thereby providing a contact resistance that is large compared to the rest of the electrode and dielectric liquid. Current through the contact area causes local heating of the electrode at the contact and raises its temperature toward the melting point of the electrode. Heating causes an increase in resistance of the electrode region so that the area of contact can be increased further immersion of the electrode. The contact area becomes a high-energy region where high energy reactions can be sustained such as fusion and the erosion of the electrode to generate powder having a very fine particle size.

Abstract: Apparatus is provided for the production of ultrafine powder. The powder is produced by spark erosion within an electric discharge cell. The starting material for production of the powder is a body in chunk form of the material to be pulverized. The material is contained in an electric discharge cell having a fine mesh screen bottom. The cell and its contents are immersed in a dielectric fluid such as water, liquified gas or an organic base liquid. The cell and its contents are vibrated to cause the chunks to separate repeatedly and momentarily. A sparking voltage is impressed repeatedly through the body to develop sparks between confronting portions of separated chunk surfaces. Small particles produced as a result of the sparking fall through the screen of the cell and are collected as product.

Abstract: A ferrofluid comprised of composite particles comprised of polymer-enmeshed magnetic metallic particles in indefinite suspension in a carrier fluid is produced by providing a pair of electrodes formed of a composition which will produce the desired magnetic metallic particles, immersing the electrodes in an organic dielectric liquid, applying a pulsed electric potential between the electrodes, adjusting the gap therebetween until there is an electric discharge eroding an electrode producing magnetic metallic particles enmeshed in polymer, recovering the magnetic material from the dielectric liquid and dispersing the magnetic material in a carrier fluid producing ferrofluid.

Abstract: A ferrofluid comprised of composite particles comprised of polymer-enmeshed magnetic metallic particles in indefinite suspension in a carrier fluid is produced by providing a pair of electrodes formed of a composition which will produce the desired magnetic metallic particles, immersing the electrodes in an organic dielectric liquid, applying a pulsed electric potential between the electrodes adjusting the gap therebetween until there is an electric discharge eroding an electrode producing magnetic metallic particles enmeshed in polymer, recovering the magnetic material from the dielectric liquid and dispersing the magnetic material in a carrier fluid producing ferrofluid.

Abstract: An easily assembled transverse magnetic printing head and method for making same are disclosed for use in a coincident current, matrix-driven, transverse printing head. In accordance with one embodiment of the present invention, digit lines pass through a recording gap in mirror image fashion as between adjacent word groupings. Similarly, the word line patterns are arranged on a printed circuit board in a zig-zag fashion. A feature common to both the word and digit line printed circuits, however, is the presence of a small expanse of circuit wiring unsupported by printed circuit substrate material through which a high permeability magnetic comb structure is inserted to form required recording gaps. The coincident current scheme is retained by driving the digit lines from alternating directions. The arrangement of the digit lines in the present invention permits the use of a planar printed circuit with no crossovers and therefore a circuit which is easily fabricated in a flexible, printed circuit design.

Abstract: A high resolution magnetic printing head comprises a pair of interlaced printed circuit board structures. Each printed circuit board structure comprises a two or three layer assembly in which each layer comprises a flexible printed circuit board having an elongated gap therein with electrically conductive signal lines crossing the gap. On each three layered structure, the signal lines on adjacent circuit boards are substantially parallel where the lines cross the gaps in the printed circuit boards. The two printed circuit board structures are adjacently disposed so that their respective elongated gaps are aligned but so that the conductive signal lines are interlaced. High permeability magnetic material is then deposited between said interleaved signal lines by electrodeposition so as to form magnetic pole pieces between the conductors bridging the elongated gaps.

Abstract: Ferrite particles having a plurality of distinct Curie temperatures are encapsulated within a polymer matrix to provide tagging material especially useful in identifying explosive materials even after detonation. In one embodiment, phosphor is dispersed within the polymer matrix to facilitate collection of tag particles following detonation. The tags are also usable in tagging other articles, especially where harsh environmental conditions are likely to be encountered.

Abstract: A magnetic belt for magnetic printing and the like has a relatively low surface resistivity provided by a conductive surface layer to eliminate unacceptable toner background.

Abstract: A magnetic printer includes an elongated comb-like printing head disposed opposite a magnetizable-oxide-bearing surface of a selectively magnetizable moving belt, and adapted to magnetize regions of the belt in a direction transverse to the direction of belt movement; and a magnetic brush for depositing magnetic ink upon the oxide-bearing remaining surface of the belt, with the magnetic brush positioned beneath the printing head, whereby the printing head provides a bearing surface along which the magnetic belt slides. The brush is designed for minimum field at the inking position while the head is designed to have its field direction transverse to the direction of the field of the brush, for minimum field interaction.

Abstract: Apparatus for fabricating a continuous loop of magnetic belt material, for use as a recording medium in a magnetic printer, utilizes a pair of cylindrical members spaced essentially parallel to one another, over which magnetic tape is layed, and held thereon by means of vacuum hold-down devices, while a seam is precisely cut and ultrasonically bonded. Methods for carrying out the fabrication are disclosed.

Abstract: A magnetic printing head, for selectively magnetizing regions of magnetic recording media moving transversely therepast, has an elongated comb-like member of magnetizable material. Each of a multiplicity of slots in the member contains conductor means energizable to carry a flow of current for generating a magnetic orientation field between two adjacent comb-tooth tips and transverse to the direction of media movement. The conductor means in each slot may comprise at least a pair of independently energizable conductors for generating the orientation field responsive to coincident flows of current therein, preferably selected by matrix techniques.

Abstract: A recording head array for magnetic printing machines comprises a flat sheet pole spaced from a line of magnetic pin poles. Spaces between image elements recorded by adjacent poles are thereby reduced. The sheet pole may be magnetized to provide a direct current bias field.

Abstract: An improved magnetic brush for transferring toner to a latent image in a magnetic printing machine comprises a rotatable applicator cylinder disposed around a multipole magnetic stator. The two poles of the stator lying closest to the image are excited with magnetic fields of like polarity to minimize interaction between the magnetic brush field and the recorded magnetic image.

Abstract: Recording head current in magnetic printing systems is reduced by application of a direct current magnetic bias field. The bias and recording fields add to produce a sum field with sufficient strength to switch a premagnetized recording medium. The bias field may be applied directly to the surface of the recording medium or may be concentrated at the recording medium surface by pin poles.In one embodiment of the invention the bias field is supplied by a permanent magnet common pole in a pin pole-type recording head array.