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US 4,068,585 AGranted
Electrostatic printer support with controlled electrostatic surface voltage
AssigneeElectroprint, Inc.
InventorLester E. Thompson
Life of this patent
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AssigneeElectroprint, Inc.
InventorLester E. Thompson
Estimating the term…
A line printing apparatus in which spot patterns of ink or toner particles are formed on a moving paper sheet. A modulator defined by a corona source and an electric shield which has a multiplicity of linearly arranged apertures is spaced from one side of the paper. The voltage at each aperture is individually controlled so that ions from the corona are permitted or prevented from passing through preselected apertures. The passing ions impinge certain particles in a toner particle cloud between the modulator and the one side of the paper sheet. A paper support bar is positioned on the other side of the paper and constructed of an insulator and an elongate electrode is secured to the back side of the insulator and positioned parallel to the aperture array. Lateral sides of the insulator are grounded and a high voltage applied to the electrode results in a high surface voltage on the paper support surface of the insulator which gradually drops off to zero or opposite potential from a maximum along a line aligned with the aperture array to the lateral sides of the insulator. Those toner particles impinged by ions are attracted to the high surface voltage on the insulator and deposited on the side of the sheet facing the modulator to sequentially form spot patterns and generate a line print. In one embodiment, the paper support bar is stationary and the paper sheet slides across its surface. In another embodiment, the paper support bar is a rotatable cylinder, preferably supported by rotatable support cylinders with electrically insulative surfaces.
In a non-contact line printing apparatus of the type having a print receiving medium, a source of charged particles spaced from one side of the medium, an electrode on the other side of the medium to form an electric field in the space between the source and the medium so that charged particles are propelled by the field through space from the source to impinge the medium in a printing zone, and means for electrically modifying the field in accordance with an image to be reproduced, the improvement comprising:
An electrostatic non-contact line printer comprising an elongate source of charged particles, an elongate conductor spaced from and parallel to said source so that a printing medium and an ink marking particle cloud can pass between said source and said conductor, means for establishing an electric field between said elongate source and said elongate conductor to attract said charged particles from said elongate source to said elongate conductor, means for modifying the field in accordance with an image to be reproduced, and discharge prevention means positioned between said source and said conductor for preventing the formation of an electric discharge in the vicinity of the conductor when the conductor is subjected to a relatively high voltage thereby to prevent unintended electrical charging of the ink marking particles by said electric discharge and the resulting attraction of the ink marking particles to said modifying means said discharge prevention means comprised of at least first and second portions, said first portion having a resistivity which is lower than said second portion, said first portion having an exposed paper-facing-surface intersecting the plane including the center-lines of said elongate source of charged particles and said elongate conductor.
Apparatus for non-contact line printing on an elongate, longitudinally movable strip of material comprising a corona source for the emission of ions, an electric voltage modulator extending over the width of the material on one side thereof, being spaced from the material and including an array of apertures for the selective passage of ions through the apertures, an electrode parallel to the aperture array, extending beyond the material width and located on another side of the material for forming an electric field between said modulator and the electrode whereby a particle mist can be introduced between said modulator and the material and selected ones of the particles impinged by ions passing through the apertures become charged for attraction to and deposition on the material and thereby forming spot patterns on the material, means electrically insulating said electrode from the material, said insulating means having an exterior surface for contacting the material as the material advances longitudinally, said insulating means comprised of first and second high resistivity components of different resistivities, the first component positioned between said electrode and said material, said second component positioned on the opposite side of said conductor and having a higher resistivity than said first component and means forming a voltage on said exterior surface which voltage is highest along a line aligned with the aperture array and which tapers off relatively rapidly and continuously to approximately ground potential at lateral sides of said exterior surface.
Line printing apparatus for forming spot patterns of particles on a longitudinally moving sheet paper or the like comprising a modulator including an array of apertures arranged perpendicular to the paper motion and spaced from the paper for selectively passing ions through some of the apertures to thereby charge a particle mist between the aperture array and the sheet and thus form the spot patterns by impinging the charged particles on the paper, and a backup bar on a side of the sheet opposite the array for supporting a portion of the sheet aligned with the array while spot patterns are formed on the sheet, the backup bar being constructed of a material having a lesser electric resistance than the electric resistance of the paper sheet, the backup bar including means for applying a maximum electric potential to a surface portion of the bar contacting the sheet and aligned with the array and for gradually decreasing the potential on the bar to either side of the bar center to prevent high electric field concentrations and the formation of ions in the vicinity of the bar which are attracted to the modulator and which would cause a deposit of particles on the modulator said backup bar comprised of an electrically conductive support member partially enclosing a first semiconductive element which, in turn, partially encloses a second semiconductive element having a lower resistivity than said first semiconductive element.
Dependencies are inferred from the claim text.